Abstract:Biological soil crusts (BSCs) are special complexes composed of cryptogam, microorganism and soil fine particles bonded by their exuding mucilaginous material, which widely distributed in various climate and habitat conditions. As important components of ecosystem, BSCs play vital roles in soil ecological, hydrological, biological and geochemical processes as well as ecological restoration process. The paper reviewed the ecological functions of BSCs, mainly centering on the effects of BSCs on soil physical, chemical, and biological characteristics, and soil hydrological and erosional processes. Although much has been achieved, there are still many problems need to be deeply and systematically explored. The future studies may focus on the extension of the study region and spatial-temporal scale, multiprocess coupling mechanism, the process of BSCs influencing nitrogen cycle and its responding mechanism to nitrogen deposition, and the spatial distribution and interaction between vascular plants. The results can promote the correlational research on BSCs and deepen the understanding of BSCs ecological functions and earth surface processes.

Abstract:In order to study the effects of forest land and rain intensities on the phosphorus loss regulation in subsurface runoff, the typical Quercus acutissima forest, Robinia pseudoacacia forest and Quercus acutissima-Robinia pseudoacacia mixed forest in hilly area of middle southern Shandong Province were selected as the research objects. And simulated artificial rainfall experiments were carried out. The results showed that:(1) Subsurface runoff accounted for 36.16%~46.93% of the total runoff in forest, and for 18.58% in grassland. The rainwater infiltration capacity was higher in forest land than that in grassland, and the mixed forest gave the highest rainfall infiltration capacity. With the increase of rainfall intensities, the proportions of subsurface runoff decreased from 54.34% to 37.62% in forest. (2) TP losses with subsurface runoff in forest were only 45.88%~63.25% of those in grassland. Total TP losses in forest land were 55.32%~77.43% lower than thoseof grassland. Compared with grassland, the control effect of phosphorus in forest land was better, especially for the mixed forest, which gave the best control effect on phosphorus loss. With the increase of rainfall intensities, TP losses with subsurface runoff in forest increased by 0.68 times to 1.33 times. (3) TP losses with subsurface runoff accounts for 12.12%~25.00% of the total TP losses in forest and grassland. TP losses in subsurface runoff occupied the certain proportions of the total TP losses, so the subsurface runoff could not be ignored in TP loss control. With the increase of rainfall intensities, the proportions of TP losses with subsurface runoff decreased from 30.66% to 10.62% in forest. These findings could provide important reference for phosphorus loss control in forestland and the improvement of ecological environment.

Abstract:Crop rotation affects dynamic changes of C factor in USLE and reduces hillslope soil erosion by improving soil properties. Based on six years observation data of runoff, soil loss and rainfall from the soybean-red adzuki bean rotation and bare-fallow runoff plots in the thin layer Mollisol region of the Northeast China, this paper analyzed erosive rainfall characteristics, discussed effects of crop rotation on preventing hillslope soil erosion, and explored yearly and monthly changes (May-October) of C factor (crop cover and management) during 2011-2016. The results showed that all erosive rainfall in the study area occurred from May to October, which occupied 32.5% to 68.1% of annual precipitation, and its distribution of inter-annual was uneven. For the bare-fallow runoff plot with 5° slope gradient, soil erosion mainly occurred in June to August and annual runoff and soil loss was 48.4 mm and 1 388.2 t/(km²·a) respectively; while for the crop rotation plot with 5° slope gradient, soil erosion mainly occurred in May to July and annual runoff and soil loss was 19.5 mm and 166.7 t/(km²·a) respectively. Compared with the bare-fallow plots, average annual runoff and soil loss from crop rotation plot under 5° slope gradient were decreased by 59.7% and 88.0%, respectively. Average yearly C value for crop rotation plots was 0.12. For soybean crop, C value was 0.04, ranging from 0.007 to 0.080; and for red adzuki bean, C value was 0.38, ranging from 0.28 to 0.46. Monthly C values of soybean and red adzuki bean varied between 0.01~0.24 and 0.01~0.80, respectively. The soybean-red adzuki bean rotation had a significant effect on preventing hillslope soil erosion in the thin layer Mollisol region of the Northeast China. The results provided scientific basis for quantitative evaluation of soil erosion and prediction model establishment in thin layer Mollisol region of the Northeast China.

Abstract:The southern red soil region is densely populated, with strong development and utilization of land resources and diverse types of soil erosion. In order to research the eroded sediment sources in watershed with intensive exploitation under different land use types in red soil region, this study selected a small watershed in the town of Gande as researd object, and analyzed 41 geochemical properties of the potential sediment sources as well as sediment in the basin. Kruskal-Wallis H test and Stepwise discriminant analysis were used to identify the best combination of fingerprint factors and calculate the sediment contribution rates of each sediment source. The results showed that the best fingerprint combination was made up of eight factors, including A-P, Cu, P, Y, Ca, Ga, Sn, and Nd. The total cumulative contribution rate was over 90%, and the value of GOF was higher than 0.80. A multivariate mixed model was applied to identify the different sediment sources. It indicated that sediment mainly came from forest, tea plantations and mining area in the front rainy season, constituting 28.59%, 28.20%, and 27.59% respectively. The relative contribution rates of the four land use types were tea plantations > forest > mining area > farmland in the typhoon rainy season. The figures of sediment contribution percentages showed that the unit area sediment contribution rate in mining area was 8 times, 10 times and 10 times respectively of those in farmland, forest and tea plantation. That's to say, the soil erosion intensity in mining area is the highest.

Abstract:Due to the difficulty of extracting runoff depth (1~5 mm) and hydrodynamic parameters (velocity, depth, etc), it is difficult to study the water flow structure, energy dissipation and sediment transport of runoff erosion on slope surface. Based on the principle of hydrodynamics and similarity theory, the flow similarity process of overland sediment flow on slope surface was simulated by enlarging the depth of runoff with non-conventional scale model. The results were as follows:(1) When the water depth of overland sediment flow was enlarged by 2.5 times and sediment content was 10~320 kg/m³, the errors of surface line (resistance), velocity and erosion topography from the prototype and model of overland sediment flow were 0~0.1%, 0.1%~5.3% and 0.9%~4.9%, respectively, all the errors of which were within the allowable ranges. The prototype and the model fitted the similarity transform relationship, such as geometry and motion. (2) When the water depth was 0.5~1.25 cm, the overland sediment flow was turbulent, the vertical distribution of velocities of the prototype and the model fitted the logarithmic distribution, which could be expressed by the same equation. (3) The non-conventional scale model could be used for the further studies of hydrodynamic parameters extraction, flow structure, energy dissipation and sediment transport of the overland sediment flow.

Abstract:Storm pattern plays a key role on rill erosion processes, and contour ridging has the unique characteristic of rill erosion. In this study, simulated rainfall experiment was conducted to determine the characteristics of rill morphology, runoff and sediment yielding, flow hydraulic characteristics and dynamic mechanisms of rill erosion. Using the runoff box for simultaneously changing the row grade and field slope, four storm patterns (the rising, falling, rising-falling, and falling-rising patterns) were set on cinnamon soil in a contour ridge system. All patterns included three rainfall intensities:30, 60, and 90 mm/h, and comprised the same kinetic energy, total rainfall amount, and average rainfall intensity. Results showed that the differences in rates of headward erosion, bank landslip, and the downcutting of rill bottom among storm patterns greatly changed rill morphology. Compared with the rising pattern, rill width and depth from the rising-falling, falling-rising, and falling patterns increased by158.8% and 38.9%, 115.7% and -27.8%, 21.6% and -33.3% respectively, while the correspondingly increased ratios of width to depth were 14.9%, 60.4%, and 82.6%, respectively. Rill runoff and sediment yield showed significant differences among storm patterns. Runoff ranked in the following order:the rising-falling > falling-rising > falling > rising pattern, and sediment yield was in order of the rising-falling > falling > falling-rising > rising pattern. Regardless of storm pattern, power function relationship was found between runoff rate and sediment yield rate, while the exponent in the rising-falling, falling, and falling-rising patterns increased by 2.52, 2.46, and 1.46 times respectively, compared with the rising pattern. As for rill flow hydraulic characteristics, the largest difference occurred in Reynolds number, and stream power was in dynamic mechanisms parameter. Reynolds number and stream power from the rising-falling, falling-rising, and falling patterns significantly increased by 107.0% and 106.8%, 42.2% and 41.9%, 16.6% and 16.7%, respectively, compared with the rising pattern. These findings would help understand the mechanism of contour ridge influence on rill erosion process, and was of great importance to apply the contour ridge tillage for soil erosion control.

Abstract:The effect of graphene solution combined with chemical fertilizer on the soil nutrients loss was studied by soil column leaching test, and the fertilizer retention effect of graphene solution was explored. A total of five graphene solution concentrations were designed, and four times leaching was carried out, the conductivity, nitrogen, phosphorus and potassium contents of each leaching solution and the soil after four times of leaching were determined. The results showed that:(1) Application of graphene solution combined with chemical fertilizer had effect on the conductivity, nitrogen, phosphorus and potassium contents of the leaching solution, and the greater the graphene solution concentration added, the more obvious the effect was. The content of nitrate nitrogen, total nitrogen and phosphorus in the leaching solution treated with graphene solution could be reduced by 88.2%, 80.9% and 84.7%, respectively. (2) After four times of leaching, the content of nitrogen, phosphorus, potassium and the conductivity value in the soil treated with graphene solution increased compared with the control, and the retention effects of total nitrogen and total phosphorus increased by 175.0% and 59.3%, but there was no significant effect on the retention of ammonium nitrogen. (3) The effect of graphene solution on the pH of the eluent and soil was not obvious. The application of graphene solution combined with chemical fertilizer into the soil could significantly reduce the leaching loss of soil nutrients, and had obvious retention effect of the soil nutrients. Graphene solution had the function of fertilizer conservation.

Abstract:Taking the terrace + Myrica rubra + Paspalum natatum (C1), hillside ditch+ fish-scale pits + Lonicera japonica (C2), terraced fields with slope + fish-scale pits + Camellia oleifera (C3), fish-scale pits + Camellia oleifera (C4), slub ditch + arbor and shrub and herb (C5) five soil and water conservation measures and no measures (CK) in purple soil slope land of Ninghua County, western Fujian Province as the research object, the available nutrients contents and erodibility characteristics were compared and analyzed; and the relationships between soil available nutrients and erodibility characteristics were revealed. The results showed that the available nutrients contents of purple soil were higher than those of CK except nitrate nitrogen under 5 soil and water conservation measures. The contents of ammonium nitrogen, nitrate nitrogen, available phosphorus (AP) and available potassium (AK) showed the changes of C2 > C3 > C4 > C1 > C5 > CK, C2 > CK > C4 > C3 > C5 > C1, C2 > C5 > C1 > C3 > C4 > CK and C2 > C1 > C3 > C5 > C4 > CK respectively. All the soil AN/AP and AN/AK under 5 soil and water conservation measures were less than CK, while AP/AK showed C3 < CK < C4 < C1 < C5 < C2. In general, five soil and water conservation measures could improve the balance of soil available nutrients. The K values of soil erodibility under 5 measures were lower than that of CK. The contents of soil organic carbon were higher than that of CK. Among them, the soil K value under C2 was the least, and the contents of organic carbon and sand were the highest. It could be seen that the soil and water conservation measures could effectively improve the anti-erosion ability in the purple soil slope of west Fujian, where the hillside ditch + fish-scale pits + Lonicera japonica gave the best. The soil available nutrients were closely related to the characteristics of erodibility. The higher the K value of soil erodibility, the more serious the available nutrients loss and the lower the available nutrients contents. These findings provided data support for evaluating the effect of soil erosion control in purple soil area of Western Fujian, and also provided reference for the selection of soil and water conservation measures in this area.

Abstract:In this study, data mining and integration were used to establish China's soil permeability database, and comprehensive analysis of the influencing factors were applied to reveal the regional variation of soil permeability. The results showed that:(1) The changes in soil permeability were regional in Southwest China < North China < Northeast China. Southwestern China had the worst soil permeability, and the logarithm of infiltration rate fluctuated between -0.5~-2.0. The soil permeability in North and Northeast of China was good, with values above 0.5. (2) Climate types and forest ages indirectly improved soil penetration by affecting vegetation. Vegetation could effectively increase soil infiltration, but there was no significant difference between vegetation types. As soil layers deepened, soil permeability declined. The threshold values existed for all the effects of soil organic matter, soil bulk density and non-capillary porosity on soil infiltration. The values were 30%, 1.0 g/cm³, and 30%, respectively. When the value of each factor exceeded this threshold, its effect on soil penetration decreased. In order to better explore the effect of soil types on soil permeability, the analysis of soil structure, aggregates and other data should be strengthened in the future research. (3) The effects of altitude, soil depth and soil bulk density on soil permeability occurred mainly through affecting the number of non-capillary pores in the soil. Non-capillary porosity was the dominant factor affecting soil infiltration, with the path coefficient of 0.34.

Abstract:Through wind tunnel experiment in the Minqin oasis desert region, the soil wind erosion rate and blown sand structure of 0-20 cm in five cropland abandoned for different years were simulated under five wind speeds. The results indicated that mean soil wind erosion rate increased significantly in the cropland abandoned more than 20 years, and the soil wind erosion rates of abandoned 30 and 40 years croplands was 2.40~4.97 times that of other treatments. The exponential functions were found between rate of wind erosion and wind speed in all the five abandoned cropland, and the wind erosion rate increased faster with the increasing of wind speed in 30 and 40 years abandoned cropland. Wind speed of 14 m/s was the significant point for aggravating soil wind erosion. When the wind speed was greater than 14 m/s, soil wind erosion rate of cropland abandoned more than 20 years was significantly higher than that of abandoned within 20 years. In 0-20 cm, there was a negative linear relationship between the rate of sediment transport and the height in the cropland abandoned within 20 years, and negative exponential functions were founded in cropland abandoned 30 or 40 years. The total volume of sand transport in 0-4 cm and sand transport percent between 0-4 cm and 0-20 cm (Q_0-4/Q_0-20) in the cropland abandoned within 20 years were less than those of cropland abandoned more than 20 years. With the increasing of the abandoned years, the content of nonerodible soil particles (aggregates and coarse grits larger than 1mm) in the surface soil layer significantly reduced, and soil wind erosion rate decreased by a negative line function with the increasing of nonerodible soil particles content. Thus abandoned years should be properly reduced in order to increase soil resistance to wind erosion in this region.

Abstract:The hilly region of red soil in southern Jiangxi is being faced with serious soil erosion and land degradation. In this study, we took the Nanfeng County as a case study to explore the relationships between soil erosion and nutrient elements under wetland pine forest, orange orchard and paddy field using the ¹³⁷Cs tracer approach. The results showed that:(1) There were significant differences in the distributions of ¹³⁷Cs and nutrient elements in soil with the three land use types. The contents of ¹³⁷Cs in soil of wetland pine forest decreased exponentially along with the vertical profile. While in the soils of orange orchard and paddy fields, the ¹³⁷Cs was evenly distributed in the plough layer due to human disturbance. The distribution of organic matter was similar with ¹³⁷Cs. The contents of total nitrogen, alkali nitrogen, available phosphorus and available potassium in the three land use types showed obvious accumulation in surface layer. (2) In the soil of hillside wetland pine forest, the contents of ¹³⁷Cs, total nitrogen, alkali nitrogen, available phosphorus, available potassium and organic matter were characterized by:downhill > uphill > mid-slope. While in the orange orchard soil, the activities of ¹³⁷Cs were mid-slope > downhill > uphill. The contents of total nitrogen, alkali nitrogen and available phosphorus showed downhill > mid-slope > uphill. And the maximum contents of available potassium and organic matter were found on the uphill. (3) Correlation analysis showed that ¹³⁷Cs was positively correlated with organic matter, total nitrogen and alkali nitrogen, indicating that organic matter and nitrogen in small watershed might have the same physical migration mode as ¹³⁷Cs. The pH value was significantly negatively correlated with ¹³⁷Cs. While there were no significant correlations between the contents of available phosphorus and available potassium and ¹³⁷Cs. (4) Among the three land use types, the ¹³⁷Cs, organic matter, total nitrogen and alkali nitrogen contents in the paddy field of the small watershed valley were the highest. On the hillside, the contents of ¹³⁷Cs and soil nutrient elements in the orange orchard were higher than those in the wetland pine forest, indicating that the changing slopping-to-terraced orange planting patterns could effectively alleviate soil erosion and nutrient loss, and improve the regional ecological environment.

Abstract:In order to explore the relationships between soil water dynamics and aggregate stability under different vegetation cover, the soil under the three vegetation types of osmanthus field, rapeseed field and fir field was selected as the research objects. The relationships between soil aggregate and soil water content in the long-term, short-term (before and after short-term rainfall) were investigated. The results showed that in the relatively long-term (one year), the aggregate stability under the fir trees field was significantly higher than those of the osmanthus and rapeseed fields. The water stable aggregate was dominated by 0.25~2 mm. The one-year aggregate variation was significantly negatively correlated with soil water content, which meant the aggregate stability increased with decreasing soil water content. For example, in osmanthus field and rapeseed field, soil water were positively correlated with the portion of aggregate (< 0.25 mm), but negatively correlated with the portion of aggregate (> 0.25 mm). This indicated that the soil water content could promote the large aggregates into microaggregates, and therefore, the stability of aggregate changed. In the short term, the soil aggregate mean weight diameter (MWD) changed in response to the soil water content.Specifically, soil aggregate MWD showed a downward trend with the beginning of rainfall, then reached a minimum value, after that, the aggregate MWD rose gradually when the rainfall stopped. The pattern of aggregate MWD was related with the rapid changes in soil water caused by rainfall and rainfall mechanical effect. Therefore, in combination with long-term and short-term changes of aggregate, fir trees in red soils can effectively regulate the dynamics of soil water variation, and improve the stability of aggregates, then play important role in preventing soil water erosion.

Abstract:A Five-year field experiment was conducted to study the size compositions and stability of soil aggregate and their soil organic carbon (SOC) contribution rates to total SOC in different maize straw returning treatments (without straw returning, CK; straw cover returning, SCR; straw rotational tillage returning, SRT). The results indicated that straw returning modes significantly increased the mass of macro-aggregates (>250 μm), mean weight diameter (MWD) and geometric mean diameter (GMD), compared with CK (P < 0.05). SRT had more significant effects on formation of soil macro-aggregates than SCR, but there was no obvious difference in stability of soil aggregate between SRT and SCR. SRT markedly enhanced SOC of every size aggregates and contribution rates of aggregates SOC, which were higher than SCR in SOC of >2 000 μm and <53 μm aggregates, contribution rates of 250~2 000 μm aggregates SOC. There were significant positive correlations between the SOC and the stability and associated-C (P < 0.01) of aggregate. Straw rotational tillage (two years of rotary tillage plus one year of moldboard return) was more favorable for macro-aggregates formation and soil structure stability, improving carbon pool of soil aggregate and their SOC contribution rates, which one of was the most appropriate rotational tillage pattern in Chernozem soil, northeast China.

Abstract:In this study, two stands and natural grassland were selected in Taihe Red soil degraded area of Jiangxi Province to research the distributions and turnover characteristics of organic carbon in soil aggregates. The results showed that the proportion of macroagrregates was the largest and that of microaggregates was the lowest.The content of organic carbon of all aggregates was higher in the Schima plantation than that of the grassland. The organic carbon in soil silt (< 53 μm) was the highest. The δ¹³C value of soil aggregate in the surface soil had the highest decrease in grassland compared with the original soil, and moderate in broad-leaved forest. The turnover time of soil organic carbonin surface layer in coniferous forest was 41~53 years,lower than that in 10-20 cm soil layer. The turnover time of organic carbon in the clay particle of the two plantation was the shortest and that in the macroaggregate was the longest.The results also showed that vegetation restoration from evergreen broad-leaved Schima superba in the red soil region could effectively enhance soil fertility thus not only increasing the organic carbon content in the original soil, but also increasing the organic carbon content in the aggregate. However, the vegetation restoration effect of Pinu smassoniana plantationwas weaker than that of broad-leaved forest. So some measures should be taken to promote the restoration of coniferous forest.

Abstract:In order to explore the effect of soil bulk density on the water infiltration capacity under surge-root irrigation (SRI) in red soil regions, a experiment of water infiltration was carried out under different soil bulk density levels of red soil for SRI in soil bins. The results showed that the bulk density had a significant effect on soil infiltration capacity. With the decrease of soil bulk densities,wetting front migration, the cumulative infiltration and the infiltration rates showed increasing trends. The smaller the bulk density was, the greater decrease occurred. The wetting front migration, the cumulative infiltration and the steady infiltration rates and soil bulk densities were negatively correlated as power functions. For the same depth soil layer, the smaller the soil moisture content was observed in the larger the soil bulk density. The effect of bulk densities on the water content distribution was gradually weakened during the water redistribution process. The Kostiakov infiltration model showed that the initial infiltration rates of the soil decreased with the increase of bulk densities. Under the greater the bulk density, the infiltration capacity decreased more fastly. This research could lay the foundation for the popularization and application of SRI technology in red soil areas.

Abstract:In order to investigate the response characteristics of the runoff and organic carbon loss to slope gradients in slope purple soil farmland with contour ridges, the surface runoff, interflow and dissolved organic carbon loss were studied during maize growth stages. Runoff plots and field artificial rainfall simulation methods were adopted. The results showed that the surface runoff displayed an order of 20° > 15° > 10° during the whole maize growth stage, while the interflow for 10° > 15° > 20°. For the different slope gradients, the surface runoff displayed an order of seedling stage > mature stage > jointing stage > tasseling stage, however, the interflow followed:tasseling stage > jointing stage > mature stage > seedling stage. The dissolved organic carbon (DOC) mass concentrations of surface runoff showed 20° > 15° > 10° during the whole maize growth stage, and seedling stage > jointing stage > mature stage > tasseling stage for the different slope gradients. The DOC mass concentrations of interflow showed an order of 10° > 15° > 20° at seedling stage, jointing stage and mature stage. The DOC mass concentration of interflow at seedling stage was maximum and tasseling stage was minimum for the different slope gradients. The DOC migration flux of surface runoff displayed an order of 20° > 15° > 10° during the whole maize growth stage, and seedling stage > mature stage > jointing stage > tasseling stage for the different slope gradients. The DOC migration flux of interflow displayed an order of 10° > 15° > 20° during the whole maize growth stage, while DOC migration flux of interflow for the different slope gradients showed the consistency with surface runoff. These results could provide theoretical basis for runoff and organic carbon loss regulation under different slope gradients during maize growth season.

Abstract:In order to explore the influence mechanism of desertification on the soil organic carbon (SOC) and soil inorganic carbon (SIC), we studied the distribution characteristics of SOC and SIC in bulk soil and their different particle sizes by spatial method instead of time method during the desertification process of desert grassland in Yanchi County. The results showed that:(1) The SIC and SOC contents in 0-10cm soil layer declined with the increasing desertification of desert grassland. The rank of SIC and SOC contents in each particle size of semi-fixed dunes and mobile dunes were soil inorganic carbon of clay and silt (CSIC) > soil inorganic carbon of fine sand (FIC) > soil inorganic carbon of coarse sand (CIC), soil organic carbon of fine sand (FOC) > soil organic carbon of coarse sand (COC) > soil organic carbon of clay and silt (CSOC). (2) The rank of SOC, SIC and STC densities in 0-30 cm soil layer were desert grassland > fixed dunes > semi-fixed dunes > mobile dunes. Compared with desert grassland, SOC and SIC densities in fixed dunes, semi-fixed dunes and mobile dunes declined by 18.5%, 57.7%, 60.5% and 6.7%, 35.9%, 47.0% respectively. (3) The SOC and SIC contents in different particle size fractions of 0-10 cm soil layer and SOCD and SICD of 0-30 cm soil layer were significantly positively correlated with SOC and SIC contents in bulk soil, and CIC and COC had the greatest influence on SOC. The SIC in bulk soil were significantly negatively correlated to CSIC and CSOC. Therefore, desertification control is extremely important to reduce soil carbon loss in desert grassland.

Abstract:To investigate the water conservation function of litter and soil in degraded poplar plantation in Bashang plateau, a sample plot survey was conducted in poplar plantation with three degradations (light degradation, medium degradation and heavy degradation) in Zhangbei from July to September, 2016, and water conservation characteristics of litter and soil were quantitatively analyzed. The results showed that:(1) Litter storage was sorted as light degradation (24.68 t/hm²) > medium degradation (13.43 t/hm²) > heavy degradation (3.66 t/hm²), and the effective retention capacity listed in the order of light degradation (29.28 t/hm²) > medium degradation (23.18 t/hm²) > heavy degradation (3.30 t/hm²), the maximum water-holding capacity followed the order of light degradation (34.90 t/hm²) > medium degradation (24.13 t/hm²) > heavy degradation (3.86 t/hm²), the maximum water-holding rate followed the order of light degradation (228.80%) > medium degradation (228.70%) > heavy degradation (119.94%). There was an logarithmic function relationship between water-holding capacity and immersion time, while a exponential function relationship was found between water-holding rate and immersion time. (2) The soil bulk density of the three poplar plantations ranged from 1.65 to 1.80 g/cm³, capillary porosity ranged from 27.42% to 33.64%, and the range of total porosity ranged was 29.97%~38.57%. (3) There was a power function relationship between soil infiltration rate and infiltration time. The stable infiltration rate followed the order of medium degradation (3.32 mm/min) > light degradation (2.58 mm/min) > high degradation (2.44 mm/min). The water conservation capacity of soil and litter of degraded poplar plantations in Bashang Plateau was at a poor level and decreased significantly with the increasing of degradation degree. Therefore, reasonable tree species selection should be paid attention to during forest managemen, and the seriously degraded forest land should be restored by replanting other tree species or promoting regeneration. The results could provide some theoretical basis and reference for the degradation evaluation and the restoration and reconstruction of local poplar plantation.

Abstract:Understanding the temporal and spatial variation of soil moisture of forest and studying the effects of vegetation transpiration, forest floor evapotranspiration and meteorological factors on soil moisture are important to vegetation restoration, integrated forest-water management and the improvement of the eco-hydrological functions of forest/vegetation in the arid regions. A stand plot of Larix principis-rupprechtii plantation was established in the semiarid Diediegou small watershed on the north side of Liupan Mountains, Ningxia. Meteorological conditions, forest transpiration, forest floor evapotranspiration and soil moisture during July to October in 2013 were simultaneously monitored by automatic meteorological station, thermal diffusion probes, micro-lysimeters and time domain reflectometry. The soil moisture was monitored in the layers of 0-20, 20-40, 40-60 and 60-80 cm, to explored the main factors affecting the soil moisture. The results showed that:(1) Affected by the random rainfall events, the soil moisture showed corresponding pulse variation. On the whole, the mean soil moisture (32.69%) of the surface layer (0-20 cm) was relatively lower than that of the layers followed (about 40.00%). The variation range of soil moisture decreased gradually with the increasing of soil depth and rainfall amount. (2) The main meteorological factors influencing soil moisture were temperature, saturation vapor pressure deficit and atmospheric pressure. The forest transpiration and forest floor evapotranspiration had a significant correlation with the soil moisture of the main root zone (0-60 cm) during the whole study period. (3) The correlation coefficients between soil moisture and all the influencing factors decreased with the increasing of soil depth, which were significant in the main root zone, but no longer significant in the soil layers below (60-80 cm). In summary, the forest soil moisture was affected by both the precipitation input and evapotranspiration output. The temporal variation of soil moisture in each soil layer was similar. However, the soil moisture of surface layer was low and with a larger variation range. The sensitivity and amplitude of soil moisture to the influencing factors decreased gradually with the increasing of soil depth.

Abstract:In order to investigate the effects of different water regulations on the root spatial distribution, water consumption, water use and other indexes in a typical alley cropping system comprising apple (Malus pumila)-soybean (Glycine max), an experiment of mulching and irrigation coupling was carried out in the Loess Plateau of Shanxi Province. Three levels of irrigation thresholds were set:55% (low, W1), 70% (medium, W2), and 85% (high, W3) of field capacity. Meanwhile, two mulching materials including straw (M1) and plastic film (M2) were also set. The results indicated that the water regulation increased the total root length density of apple and soybean, and also expanded the root length distribution of apple in horizontal and vertical directions. The apple root length density was negatively correlated with the distance from the tree row while the soybeans had positive correlation, and both the crops had negative correlations with the vertical depth. The distribution of soil moisture increased first with the distance from trees to the crops then decreased at grain filling stage, and the minimum values occurred in the distance of 1.5~2.0 m away from the tree line. Compared with clean tillage treatment (CK0) and single mulching treatment (CK1 and CK2), the water regulation treatments increased the soil moisture in 0-60 cm depth significantly. The cluster analysis showed that the main competition area in soil moisture for the two plants was in the distance 0.5~1.5 m away from the tree row with soil depth of 0-40 cm. The apple fine roots in the M2W2 treatment were concentrated in 20-40 cm soil layer while the soybeans' in 0-20 cm soil layer, which alleviated water competition between the two species. Additionally, the water consumption in M2W2 could be reduced by 40~50 mm compared with W3 and the yield and water use efficiency could be increased by 29.37%~41.92% and 12.29%~53.35%, respectively, compared to other water regulation treatments. The net income could be 2 976.5 yuan/hm². Above all, covering plastic film in young apple-soybean intercropping system, combined with irrigation amount of 150 m³/hm² at branching stage, 400 m³/hm² at podding stage and 300 m³/hm² at grain filling stage could significantly increase the water use level and economic benefits in the intercropping system.

Abstract:A pilot study of hydrological effects of litters layer and soil layer was carried out in three different vegetation types (Pinus tabulaeformis plantation, Larix gmelinii plantation and Robinia pseudoacacia natural secondary forests) in Dahuofang Watershed. The hydrological functions of litters layer and soil layer were quantitatively determined by immersion method and cutting-ring method. The results showed that:(1) The litter volume of three different vegetation types was about 23.20~39.11 t/hm², which followed the order of R. pseudoacacia natural secondary forests > P. tabulaeformis plantation > L. gmelinii plantation, and the volume of semi-decomposed litter was higher than that of undecomposed litter in broad-leaved forest, while the opposite trend was observed in coniferous forest. (2) The maximum water-holding capacity and modified interception amount was 50.24~109.19 t/hm² and 41.70~90.71 t/hm², respectively, both of them followed the order of R. pseudoacacia natural secondary forests > P. tabulaeformis plantation > L. gmelinii plantation. (3) Semi-decomposed litter could be saturated in 8 hours and undecomposed litter reached saturation in 10 hours, the water-holding capacity had logarithmic relationship with soaking time (R²>0.91), the absorption rate changed the most within the first 1 hour of soaking, and it obviously slowed down after 4 hours, and there was a power function relationship between water absorption rate and soaking time (R²>0.93). (4) The average soil bulk density of the three vegetation types ranged from 1.10 g/cm³ to 1.25 g/cm³, total porosity was about 27.96%~30.19%. The soil effective water-holding capacity was about 21.11~29.39 t/hm², which followed the order of R. pseudoacacia natural secondary forests > P. tabulaeformis plantation > L. gmelinii plantation. A significant power function relation between infiltration rate and infiltration fitting time was found (R²>0.90). Considering the hydrological effects of litters layer and soil layer of three different vegetation types, the water conservation function of R. pseudoacacia natural secondary forests was stronger than that of the other vegetation types, which suggested that more attention should be paid to protect and restore the natural secondary forests in the Dahuofang watershed in order to improve water conservation function of forest.

Abstract:Nitrogen and phosphorus deficiencies and seasonal drought are major problems of plantations in coastal sandy land of Fujian. Nutrient resorption can reduce dependence of plants on soil nutrients supply, thereby enhancing their ability to adapt to adversity. Casuarina equisetifolia, Acacia cunninghamia and A.aulacocarpa artificial plantations in the coastal sandy land of Fuzhou city were taken as objects, and nitrogen and phosphorus concentrations and stable nitrogen isotope abundance values (δ¹⁵N) in leaves at different ages (mature leaves and senescent leaves) were determined. The nitrogen and phosphorus resorption efficiencies of leaves (NRE, PRE), resorption proficiency (NRP, PRP) and their relationship with biological nitrogen fixation rates were studied by statistical methods. The results showed that (1) the NRE of leaves of different nitrogen fixing tree species in the coastal sandy land was sequenced as A.aulacocarpa (52.80%) > A.cunninghamia (28.27%) > C.equisetifolia (24.63%). The leaf NRE of A.aulacocarpa was significantly higher than those of A.cunninghamia and C.equisetifolia, but there was no significant difference between the latter two species. The PRE of leaves followed the order of A.cunninghamia (74.08%) > A.aulacocarpa (63.99%) > C.equisetifolia (40.47%), and there was significant difference among them. (2) The biological nitrogen fixation rates of different nitrogen fixing trees in coastal sandy land listed in the order of A.cunninghamia (69.45%) > A.aulacocarpa (69.15%) > C.equisetifolia (34.59%). There was no significant difference in nitrogen fixation rate between the two Acacia species, however, the biological nitrogen fixation rate of the two Acacia species was significantly higher than that of C.equisetifolia by 99.88%~100.77%. (3) The biological nitrogen fixation rates of different nitrogen fixing trees was negatively correlated with NRE, PRE and NRP, and positively correlated with PRP. Therefore, there was a coupling relationship between nutrient resorption and biological nitrogen fixation (BNF) in different nitrogen fixing tree species in the coastal sandy land, and BNF significantly affected NRE, PRE, NRP and PRP. The results would provide a basis for revealing the adaptation mechanism of different nitrogen fixing tree species to barren soil and seasonal drought in coastal sandy land, and also provide a reference for forest management.

Abstract:The distribution features of biomass and carbon storage of 43-year-old Cyclobalanpsis glauca mixed forest in Yongshun county, Hunan province, were studied. The biomass of tree layer and under-storey was measured by the average standard method and plot harvest method, and carbon contents by potassium dichromate-hydration heating method. The results showed that biomass per unit area of the mixed forest was 320.03 t/hm². The order of biomass per unit area from large to small was tree layer, litter layer, shrub layer and herb layer. Carbon storage per unit area of the mixed forest was 389.43 t/hm², which included vegetation layer (249.02 t/hm²) and soil layer (140.41 t/hm²). As increasing of soil depth, the carbon storage decreased. The average volumes per plant of Cyclobalanpsis glauca, Castanopsis fargesii and Cunninghamia lanceolata were 0.156 1, 0.291 2 and 0.296 0 m³ respectively, while the average carbon storages per plant were 103.85, 99.15 and 97.90 kg respectively. Cyclobalanpsis glauca was slow-growing woody species with large wood density, its average individual volume was only half of Castanopsis fargesii's and Cunninghamia lanceolata's, but both its average biomass per plant and average carbon storage per plant were higher than the latter two. It showed that the ability of carbon sequestration of tree species wasn't entirely determined by the growth rate. This finding provided a new option of tree species for ecological forest.

Abstract:Carbon content, biomass, carbon storage and distribution pattern in tree layer of Pinus yunnanensis forest with contour reverse-slope terrace arrangement were estimated in central Yunnan through standard plot survey and biomass measurement, and characteristics of carbon increment and distribution in each organ were analyzed in 8 years. The results showed that the variation of carbon content in different organs was 41.01%~47.35% under the treatment of contour reverse-slope terrace, the average carbon content was ranked as sti > leaf > branch > bark > thick root > median root > fine root. Aboveground biomass of the 10~15-year-old plantation was 32.75% higher under the treatment of contour reverse-slope terrace than that of control. Belowground biomass of the 10~15-year-old and 15~30-year-old plantation (30.73% and 35.71%) were increased significantly under contour reverse-slope terrace, and the total biomass raised significantly with the increasing of age group. Carbon storage of aboveground in 10~15-year-old (32.79%) and carbon storage of belowground in the 15~30-year-old (35.60%) were significantly increased under contour reverse-slope terrace. After 8 years of arranging contour reverse-slope terrace, carbon increment of aboveground (53.33% and 20.45%) and carbon increment of belowground (53.70% and 73.43%) increased significantly in 10~15-year-old and 15~30-year-old plantation. In conclusion, contour reverse-slope terrace should be pay close attention in the process of afforestation. Artificial afforestation should be carried out in accordance with local conditions on the basis of contour reverse-slope terrace to increase the afforestation area and vegetation carbon storage in slope areas so as to protect the local ecological environment.

Abstract:The typical shelter forests around Dahuofang Reservoir in Liaodong were taken as research object in this study, including the coniferous and broad-leave mixed forest (larch-pine-locust mixed forest), larch, pine and locust. Soil nutrients were determined to study the distribution characteristics of organic carbon, total nitrogen and organic carbon in soil profiles under different forest stands. The results showed that with the increase of soil depth, the soil organic carbon and total nitrogen contents decreased gradually in the studied four forests. The order of soil profile organic carbon contents in the four forests was:larch forest (24.16 g/kg) > locust forest (23.07 g/kg) > coniferous and broad-leave mixed forest (16.06 g/kg) > pine forest (15.76 g/kg). The order of total nitrogen contents was:locust forest (5.23 g/kg) > larch forest (4.57 g/kg) > pine forest(3.45g/kg) > coniferous and broad-keave mixed forest(2.42g/kg); The order of average C/N was:Larch forest(7.36) > coniferous and borad-leave mixed forest(6.51) > pine forest(4.67)>locust forest(4.57). The organic carbon storages of 0-40 cm soil layer in four forest stands:Larch forest (112.94 t/hm²) > locust forest (107.40 t/hm²) > coniferous and broad-leave mixed forest (105.42 t/hm²) > pine forest (89.89 t/hm²). There was no significant difference in soil pH between different forests. And the soil pH of each soil layer increased with the increasing soil depth. The soil bulk densities of the four forests was in descending order:Coniferous and broad-leave mixed forest (1.73 g/cm³) > pine forest (1.65 g/cm³) > larch forest (1.64 g/cm³) > locust forest (1.56 g/cm³). There was a significant positive correlation between soil organic carbon contents and soil total nitrogen contents in the four forest stands, while no significant correlations occurred between soil organic carbon and total nitrogen content and C/N. In the coniferous and broad-leave mixed forest stand, a significant linear relationship occurred between soil bulk density, soil total nitrogen content and soil pH with soil organic carbon, while no significances in other pure forest stands.

Abstract:Pot experiments were carried out to study the effects of urea and controlled-release nitrogen fertilizer (CRNF) application on soil fertility and nitrogen fertilizer use efficiency (NUE) and growth of rape in Southern China, and it could provide reference for the application and dissemination of CRNF in rape production. An experiment with a randomized complete block design was conducted to investigate the effects of urea and CRNF on rape biomass and yield, soil inorganic nitrogen at different growth stages, nitrogen uptake of rape, physiological characteristics of rape, soil microbial nitrogen and enzyme activity using high yielding variety "Xiangyou15". According to the standard amount of nitrogen application in rape field, four treatments were set up in this study, conventional urea (Urea), controlled-release nitrogen fertilizer 1(CRNF1), controlled-release nitrogen fertilizer 2 (CRNF2) and no nitrogen fertilizer (CK). The result showed that compared with the conventional urea treatment, CRNF significantly increased the biomass of rape by 11.2%~20.1% at flowering and harvest stage, the NO₃-N concentration of rape at flowering and harvest stage in the CRNF1 treatment was significantly increased by 43.2% and 61.8%, respectively, and the NH⁴⁺-N concentration in soil in CRNF2 treatment was obviously increased by 18.7% and 64.1%, respectively, at flowering and harvest stage, which ensured the supply of soil nitrogen at the late growth stage of rape. Compared with the Urea treatment, total nitrogen uptake in rape was significantly increased by CRNF at the bolting and flowering stage. In eventually, the nitrogen use efficiency (NUE) was increased by 23.1%~60.2% and the agronomic nitrogen use efficiency (NAE) raised by 19.1%~30.5%. CRNF1 treatment significantly increased the SPDA value and total chlorophyll content by 6.5% and 10.1%, respectively, at the late growth stage of rape. Compared with the Urea treatment, CRNF1 treatment significantly increased the soil microbial nitrogen by 142.5% at the late growth stage of rape. In addition, the activity of soil urease, FDA hydrolase in the CRNF application treatment were significantly increased by 8.4%~12.9% and 24.5%~32.4%, respectively, at the late growth stage of rape. These results demonstrate that under the condition of total nitrogen application rate unchanged, application of CRNF mainly increased soil available nitrogen content at later growth stages, improved photosynthesis, enhanced soil microbial biomass and enzyme activity, thereby increased nitrogen uptake of rape, increased NUE and dry matter accumulation of rape, and increased grain yield.

Abstract:Mixing broad-leaved tree species is an important measure to improve soil fertility and enhance nutrient cycling in coniferous forests, but their mixed effects vary with coniferous tree species. Masson pine (Pinus massoniana) and slash pine (P. elliottii) are widely planted in the subtropical China. However, the mixed effects of the two coniferous forests are still not clear. Soils with 60 cm depth were collected in four forest types:masson pine plantation (MP), slash pine plantation (SP) and two mixed forest of Schima superba with MP (MPM) and SP (SPM), to determine the bulk density, organic carbon (OC), total nitrogen (TN) and total phosphorus (TP) concentrations. The carbon, nitrogen and phosphorus storages and their stoichiometry were also calculated. The OC concentration of MP in 0-60 cm soil layer significantly increased by mixing with broad-leaved tree species, but there was no significant difference in OC concentrations between SP and SPM. Meanwhile, the TN concentrations of MP and SP increased in response to mixed effects. The OC storage of 0-60 cm soil depth in MPM increased by 95.8% compared with MP, while mixing with broad-leaved species had no effect on soil OC storage in SP. The total N storage of 0-60 cm soil depth in MP and SP significantly increased by 15.8% and 28.4% respectively after mixing with broad-leaved tree species. The soil C/N of MP in 0-40 cm soil layer increased and soil C/N of SP in 0-10 cm soil layer decreased after mixing with broad-leaved tree species. The soil C/P in 0-20 cm and soil N/P in 0-10 cm of MP while significantly increased induced by mixed effect, whereas there was only significant difference in soil N/P in 0-10 cm layer between SP and SPM. Soil nitrogen storages increased after the two coniferous forests mixed with broad-leaved tree species, while no significant influence of mixed effects was observed on the phosphorus storage. Moreover, the characteristics of soil carbon, nitrogen and phosphorus stoichiometry were influenced by mixing effects. And, the soil nutrients concentrations, storages and their stoichiometry characteristics of MP were more sensitive to mixed effects compared with those of SP.

Abstract:To evaluate the wetland pollution and potential environmental risks in Min River Estuary, the effects of wetland vegetations and physicochemical properties on the distribution of sediment phosphorus were explored. From land to sea in the research area, sediments of four sites with different wetland vegetation types (Spartina alterniflora, Phragmites australis, Cyperus malaccensis and Cyperus compressus respectively) were sampled in 2017, and then phosphorus speciations were analyzed using SMT method. In all four vegetation types wetlands, organic phosphorus (OP) accounted for averagely 32.03% of total phosphorus (TP), between 0.176~0.369 mg/g. Inorganic phosphorus (IP) accounted for averagely 66.49% of TP, between 0.308~0.666 mg/g. TP concentrations were from 0.491~0.998 mg/g, which were considered as moderate pollution level with the pollution index (moderate polluted 0.819~1.618). Results suggested that the distribution of phosphorus speciations varied from wetland vegetation types. The highest concentration of OP was found in the Phragmites australis wetland, and the lowest in Cyperus compressus. The Ca-P concentrations were obviously higher in Cyperus malaccensis and Cyperus compressus wetlands than in Spartina alterniflora. However, the Fe/Al-P concentrations were significantly higher in Spartina alterniflora wetland compared to other wetlands. Since TP was strongly related to IP, the trends of TP and IP were similar:The highest concentration in Cyperus compressus wetland and the lowest in Phragmites australis wetland. Finally, the Ca-P concentrations showed the significantly negative correlation with bulk density, and the positive correlation with water contents. TP concentrations were significantly negatively correlated to conductivity, and positively correlated to water contents. All these phenomenon described could relate to the comprehensive effects of vegetation types and growth stages, physicochemical properties, terrestrial materials, hydrological environment, litters, and human production activities.

Abstract:Four different vegetation communities, which represented the primary forest successional sequence in the central hilly area of Hunan Province, China, were chosen in this study. They were:Loropetalum chinense-Vaccinium bracteatum-Rhododendron mariesii scrub-grass-land (LVR), L. chinense-Cunninghamia lanceolata-Quercus fabri shrubbery (LCQ), Pinus massoniana-Lithocarpus glaber-L. chinense coniferous-broad leaved mixed forest (PLL) and L. glaber-Cleyera japonica-Cyclobalanopsis glauca evergreen broad-leaved forest (LAG). The modified phosphorus fractionation method of Tiessen and Moir, which was put forward originally by Hedley, was used to study the differences in the concentrations and composition ratios of phosphorus components at different vegetation restoration stages. The result showed that with the restoration of vegetation, the concentrations of total phosphorus (TP), total inorganic phosphorus (Pi) and total organic phosphorus (Po) increased in the same soil layer. The concentrations of NaHCO₃-Pi, NaOH-Pi, HCl-Pi and NaHCO₃-Po and NaOH-Po belonged to rapid accumulation type, and Residual-P belonged to slow accumulation type, while Resin-Pi stable type. The NaOH-Pi and NaOH-Po were the major components of the Pi and Po in different forest stands, respectively. The phosphorus pool was mainly composed of Residual-P and Po. With the vegetation restoration, the percentages of Po to TP increased gradually in the same soil layer, Pi increased first and then decreased, while Residual-P decreased gradually. The concentrations of TP and each P component decreased in the same forest stand with the increase of soil depth. With the restoration of vegetation, the changes of the diversity of community plant, community biomass, nutrients contents and quality of the litter layer significantly affected the contents of each P component in soil, and subsequently affected the composition ratios of soil phosphorus pool.

Abstract:The distribution and movement features of nitrogen in 1 m soil layer under different nitrogen fertilizer application were studied through artificial soil column simulation experiment in laboratory to reveal the dynamic changes of nitrogen in farmland soil. Results indicated that FN (the amount of inorganic nitrogen used by farmers) and RN (inorganic nitrogen dosage recommended by soil nutrient supply and crop demand) significantly increased the leaching of NH₄⁺-N and NO₃^--N from upper soil layer to lower soil layer. The treatments of RN+HA (zinc humic acid urea equivalent to the recommended inorganic nitrogen with RN) and RN40%+OMB (60% inorganic nitrogen fertilizer of RN with homemade organic substances) could prolong the peak time of NH₄⁺-N in the upper soil layer and reduce the NH₄⁺-N in the lower soil layer. At the end of leaching experiment, comparing with RN, the application of humic acid (HA) decreased the NH₄⁺-N residue by 29.7%~54.2% in the soil layer below 60 cm under the same amount of nitrogen, and reduced the accumulation of NO₃^--N by 17.4% in 60-80 cm soil layer. In RN 40%+OMB treatment, the dosage of inorganic nitrogen fertilizer was the minimum, and NH₄⁺-N was the highest in 0-20 cm soil layer and it was stable at 2.0 mg/kg in 40-100 cm soil layer. Comparing with RN+HA, NO₃^--N in 0-20 cm and 20-40 cm soil layer in this treatment increased by 12.3% and 2.0%, respectively, and the NO₃^--N residue in the soil layer lower than 40 cm was significantly reduced. Contrasted with RN, the total inorganic nitrogen residue of RN+HA and RN40%+OMB decreased by 7.4% and 20.2%, respectively, and the apparent leaching rate was decreased. Therefore, RN40%+OMB could inhibite the downward movement of nitrogen and reduce the risk of nitrogen leaching, and these results provide a scientific basis for reducing the nitrogen leaching.

Abstract:The aim of the current study was to examine the changes of soil physical and chemical properties and microbial quantity characteristics and to provide a reference for the restoration and utilization of the degraded grassland in alpine meadow of Gannan, Gansu Province. Soils were classified as reseeded rye group, reseeded oat group and non-reseeded (control group), and the soil was collected from the above three groups on May, July and October 2017, respectively, to investigate their physiochemical characteristics and the microbial quantity characteristics. Results showed that the soil water contents of reseeded rye grassland was significantly higher than that of oat grassland (P<0.05), the soil water contents of the above grassland were significantly higher than that of control in May and July, while there was no significant difference in October (P>0.05). There was no significant difference in pH among different sowing methods in each month (P>0.05). There was no significant difference in total nitrogen and phosphorus contents among different soil groups (P>0.05). However, the soil organic carbon contents in 10-20 cm soil layer in May, and the total nitrogen content in 40-50 cm soil layer in October of the reseeded rye group were significantly higher than the same parameters of the oat and control groups (P<0.05). On the contrary, the soil organic carbon content in 20-30 cm soil layer of the reseeded oat group was significantly higher than those of the rye and control groups in July. In May, the soil bacterial loads in 0-30 cm soil layer of the reseeded rye and oat groups were significantly higher than that of the control group (P<0.05), while the same parameter in 0-10 cm soil of reseeded groups was significantly higher than that of the control group in July (P<0.05), and the bacterial load in 0-30 cm soil layer of the reseeded rye group was significantly higher than that of the control in October (P<0.05). In May and October, the fungal load in 0-10 cm soil layer of both reseeded rye and oat groups were significantly higher than that of the control group (P<0.05), and the fungal load in 10-30 cm soil layer and actinomycelial load in 0-10 cm soil layer of reseeded groups were significantly higher than that of control group in July (P<0.05). Redundancy analysis showed that the changes of soil bacteria and fungi were linkage, and positively correlated with soil organic carbon, total nitrogen, total phosphorus and other nutrients. Therefore, it could be concluded that the changes of soil nutrients after supplementary sowing had led to the differences in soil microbial quantity, which needed attention in grassland restoration and management practices.

Abstract:In order to explore the effects of different organic material types and different shapes of same organic materials on the binding form and composition of soil humus in primary saline and alkaline land, the field experiment was carried out for three consecutive years in the primary saline and alkaline land in the western area of Jilin province, and field sampling and indoor analysis were carried out in this study. The experiment was conducted with five treatments, which were granular straw (KL), normal corn straw (JG), grass (MC), sheep manure (YF) and CK. The experimental results showed that:(1) Compared with the CK treatment, the application of different organic materials increased the soil humus content of the original saline-alkali soil, and promoted the increase of humus content in various combined forms in the soil. There was no significant difference in the content of loosely combined humus among the KL, MC and YF treatments, while the difference was significant in comparison with CK. Organic materials had a great influence on the content of conjugated humus in the combined state, and the difference was significant among the treatments. There was a significant difference in the content of stable combined humus between KL treatment and other treatments, and there was no significant difference among the JG treatment, MC treatment and YF treatment, but the difference was significant compared with CK treatment. The tightly bound humus content of the treatments applied organic materials were significantly different with that of CK, and the difference between KL treatment and JG treatment was significant, but there was no significant difference between other treatments. (2) Different organic materials all could improve the loose/tight ratio and the loose/stability ratio, which was conducive to the renewal of humus and the improvement of soil fertility. (3) There were significant difference in H/F ratio between the treatments applied organic materials and CK, and the increase of H/F ratio indicated that the further condensation of FA into HA with a high degree of aromatization and complex structure, and increased the content of HA, and promoted both the polymerization degree and the humification degree of soil humus. Organic materials could increase the humus content of the original saline-alkali soil and increase the content of humus in combined forms. The effect of different forms of the same organic material was significant difference. In this experiment, the effect of granular straw (normal corn straw was crushed under high temperature and pressure, 2 cm long, 0.5 cm diameter cylindrical particles) was much better than other treatments.

Abstract:In order to explore the relationship between photosynthetic index and the variation of CO₂ concentration in the rhizosphere of cotton soils with different salinity contents, four different salinity treatments (CK:0%,F1:0.2%,F2:0.4%,F3:0.6%) were set, and the variation of soil CO₂ concentration and photosynthetic characteristics of cotton under two soil texture (sandy soil and loam soil) were studied in barrel cultivated cotton. The results showed that with the development of cotton growth period, the CO₂ concentration of the two soil textures both increased first and then decreased, and the peak values appeared at the flowering and boll stage, and the maximum CO₂ concentration was 17 061.95 μmol/mol in loam and 17 572.00 μmol/mol in sandy soil. Under the salt treatments, the soil CO₂ concentration of the two soil textures both increased with the increasing of soil depth. The average value of soil CO₂ concentration at 50 cm soil depth was 13 540.32 μmol/mol, which was nearly two times that of the surface layer at 10 cm depth. With the increasing of salinity content, the difference of CO₂ concentration between the two texture soils was significant, both of them showed a downward trend, and the CO₂ concentration of loam soil was significantly higher than that of sandy soil. The interaction between salinity content and soil texture had extremely significant effects on net photosynthetic rate (P_n) of cotton (P<0.01). Under the same soil texture condition, P_n of cotton showed a downward trend with the increasing of salinity content at different growth stages, and reached the minimum value in F3 treatment, but the effect of low salinity content on cotton photosynthesis index was not significant (P>0.05). Under the same salinity treatment, there was significant difference in P_n of cotton between different soil textures, showing loam > sandy soil. There was a close correlation between CO₂ concentration of two soil textures and cotton net photosynthetic rate under different salinity treatments, and cotton P_n could explain 81.2% of the variation of CO₂ concentration in rhizosphere soil, which indicated that salinity content and soil texture type affected soil CO₂ concentration through cotton net photosynthetic rate. The results could provide a theoretical reference for the growth environment of crop.

Abstract:Fully analyzing the photosynthetic physiological characteristics of the main sand-fixing species in multiple scenarios has important scientific meanings for the maintenance and reconstruction of the ecosystem. The artificial Populus of Horqin Sandy Land was selected as the test materials to measure the light response and CO₂ response curves by using Li-6400 infrared gas analyzer. The testing scenarios included comparison across different months, tender and mature leaves, morning and afternoon, as well as different CO₂ concentrations and light intensity environments. Further, the net photosynthetic rate (P_n), transpiration rate (T_r) and water use efficiency (WUE) were analyzed. The results indicated that:Under the same light intensity and CO₂ concentration, the P_n at vigorous growth period was larger than that at the initial and late growth periods. The P_n, T_r and WUE were significantly different by comparing tender and mature leaves, the transpiration of tender leaves was relatively stronger, while photosynthesis of mature leaves was relatively stronger. These findings provided main reference value for the study of the physiology of artificial Populus in semiarid areas.

Abstract:In order to effectively cope with the shortage of irrigation water resources and to clarify the soil water storage and consumption characteristics in wheat field under micro sprinkler irrigation, the effects of micro sprinkler irrigation amounts on soil water storage and consumption and water use efficiency (WUE) were studied in Linfen Basin, Shanxi Province, by means of large-scale contrast method. The results showed that the soil water storage in 0-100, 0-200 and 100-200 cm soil layers at greening stage, jointing stage, filling stage and maturity stage increased with the increase of micro sprinkler irrigation amounts. The soil water storage in 0-200 cm soil layers from greening stage to maturity stage had significant differences between 150 mm and 75 mm of micro sprinkler irrigation amounts, 150 mm and 0 mm, and even between 75 mm and 0 mm. With the increase of micro sprinkler irrigation amounts from pre-sowing to maturity stage, soil water consumption in 0-100, 0-200 cm and 100-200 cm soil layers decreased. All the proportions of soil water consumption in shallow layer (0-100 cm) to the entire 0-200 cm were greater than those in deep layer (100-200 cm). And the proportions of shallow layer (0-100 cm) increased with the increase of micro sprinkler irrigation amounts, while those in deep layer (100-200 cm) decreased. The soil water consumption in 0-100 and 100-200 cm soil layers at different growth stages had positive and negative correlations respectively with the initial soil water storage in the corresponding stage. The WUE and yield increased with the increase of micro sprinkler irrigation amounts in 0~150 mm. When micro sprinkler irrigation amount reached 525 mm, the yield increased but WUE decreased. The irrigation water use efficiency (IWUE) decreased with increase of irrigation amounts. These findings an provide theoretical basis and technical support for the impacts of water shortage on wheat production system.

Abstract:In order to study the community features, soil nutrient characteristics and their correlations in different degraded grasslands of East Qilian Mountains, the lightly degraded grassland (LDG), moderately degraded grassland (MDG) and heavily degraded grassland (SDG) were taken as the research objects, and the combination of field investigation, laboratory measurement and data statistical analysis was adopted. The results showed that:(1) The characteristics of plant communities, including aboveground biomass, height, density, frequency and vegetation coverage, showed a decreasing trend from LDG to SDG, and the difference was significant (P < 0.05). And the species Margalef index, Shannon index and Evenness index of the MDG were the maximum, however, the Dominance index was the minimum. (2) There were 19 families, 38 genera and 41 species in the study area, and the plants with strong ecological adaptability mainly concentrated in Legumes, Gramineae, Compositae and Rosaceae. The vegetation types of different degraded grasslands included K. humilis with Leymus secalinus, K. humilis with Thalictrum alpinum, K. humilis with L. secalinus, among which K. humilis was the dominant species in different degraded grasslands. In different degraded grasslands, the functional groups were dominated by forbs, followed by Gramineae grasses and poison grasses. (3) With the aggravation of grassland degradation, soil available nitrogen, available phosphorus, organic carbon and water content all decreased, while pH increased. (4) The highest contribution rate of soil factors to vegetation growth in different degraded grasslands was the available nitrogen, available phosphorus and water content, respectively. In summary, with the aggravation of grassland degradation, the community structure of plants was changing to a single trend, soil nutrient content was reduced and the contribution rate of soil factors to plants was also changed accordingly.

Abstract:A 4-year field trial was conducted at the Rained Agricultural Experimental Station of Gansu Agricultural University in the Loess Plateau of central Gansu Province. Experimental treatments of carbon (C) addition sources included straw, biochar and no C addition, and each C treatment was combined with three nitrogen (N) addition levels, 0, 50 and 100 kg/hm² respectively. The experimental set-up was a randomized complete block design with three replications. The aim of the study was to determine the effect of different C sources and different N levels on soil bulk density, total porosity, soil saturated hydraulic conductivity, soil aggregate stability and crop yield. The soils were sampled at three layers (0-5, 5-10 and 10-30 cm) per plot. The results showed that compared with no Caddition treatments, application of biochar or straw increased soil total porosity, reduce bulk density, especially biochar addition, it had significant effects on reducing bulk density and increasing soil total porosity at all three observed depths, the effects of straw addition, however, was observed at 0-5 cm layer. Both straw and biochar could significantly improve soil saturated hydraulic conductivity, but the effect of biochar addition was greater than that of straw addition plots. Among observed layers, in comparison with no C addition plots, both biochar addition and straw addition could enhance the amount of soil mechanical stable aggregates and MWD significantly, and the effect of biochar addition was greater than that of straw. The amount of soil water stable aggregates and MWD were increased more significantly in biochar addition soils than those in no C addition and straw addition treatments. Hence, both biochar and straw treated soils improved soil physical properties, and biochar showed the greatest effects. The effects of biochar, straw and nitrogen on crop yield were significant, but biochar was the best, especially biochar 15 t/hm² + nitrogen 100 kg/hm². As a whole, biochar addition was proposed for the sustainable agricultural development in the Loess Plateau of central Gansu Province.

Abstract:Taking 18 soil plots at different altitudes as the research object in Xiaowutai Mountain, Hebei Province, 14 indexes, such as soil physical properties, water-holding capacity and nutrient characteristics, were analyzed and compared to reveal the vertical variation of soil physical and chemical properties at different altitudes. The results showed that:(1) With the increasing of altitude, the soil bulk density gradually decreased, while the total porosity increased gradually, and the variation of capillary porosity was not obvious. As soil depth increased, soil bulk density increased and total porosity decreased. (2) Soil water content, capillary water-holding capacity, maximum water-holding capacity and field water-holding capacity increased gradually with the increasing of altitude, and gradually decreased with the increasing of soil depth, meanwhile this decreasing trend gradually expanded with the increasing of altitude. (3) The content of soil organic matter, total nitrogen, total phosphorus and alkali-nitrogen gradually increased with the increasing of altitude and decreased with the increasing of soil depth. The content of total potassium in soil was a parabolic type "first rising and then descending" with the increasing of altitude, and reaching its peak at 2 100~2 200 m. The content of available potassium and available phosphorus in 0-20 cm soil layer did not change obviously with the increasing of altitude. The content of available potassium in 20-60 cm soil layer increased with the increasing of altitude, while the content of available phosphorus in 40-60 cm soil layer decreased. (4) Soil organic matter, total nitrogen and alkaline nitrogen had obvious "surface aggregation phenomenon", and the higher the altitude, the more obvious it was. The content of total phosphorus and available potassium had obvious "surface aggregation phenomenon", and the higher the altitude, the less obvious it was. There was a certain "surface aggregation phenomenon" in soil available phosphorus content, but it was not obvious. Soil total potassium content had no "surface aggregation phenomenon".

Abstract:In order to study the effect of nitrogen application on the infiltration and water and salt transport in salt and alkali soil, the saline soil with salt content of 0.3%, 0.9% and 1.2% and four different nitrogen concentrations (0, 300, 600, 900 mg/L) were combined as the treatments, and one dimensional vertical soil column infiltration experiment were carried out. The results showed that:(1) Nitrogen application reduced the infiltration of saline alkali soil. Under the same nitrogen application level, the infiltration capacity of saline alkali soil decreased with the increasing of salt content, and the desalting depth also decreased. (2) With the increase of infiltration time, the soil moisture of the lower root zone was the maximum when no nitrogen was applied, and the water retention of soil was the best at this time. (3) In the saline soil with salt content of 0.3%, the amount of desalination in the soil with nitrogen application was larger than that without nitrogen application, and the nitrogen application promoted the desalination of saline alkali soil; however in saline alkali soil with salt content of 0.9% and 1.2%, the amount of desalination was higher when there was no nitrogen application, which mean that nitrogen application had an antagonistic effect on the desalination of saline alkali soil. The research results provided an effective mechanism foundation for rational nitrogen application in saline alkali soil, and provided reference for crop growth and ecological protection in salinized area.

Abstract:In the field experiment, Salicornia bigelovii Torr. and Suaeda salsa Linn. were irrigated with seawater irrigation (control), 1:1 mariculture wastewater (1:1 mariculture wastewater treatment), whole mariculture wastewater (whole mariculture wastewater treatment) and normal fertilizer application with seawater (fertilizer treatment), and the plant growth and physiological characteristics were studied. The results showed that (1) Compared with the control, 1:1 mariculture wastewater irrigation increased aboveground dry weights (DW) of two plants, however whole mariculture wastewater irrigation decreased the aboveground dry weights. DW of plants in fertilizer treatment was obviously more than those in the other treatments and control. The above growth effects became more obvious with the extension of plant growth period, especially in S. salsa plants. (2) Compared with fertilizer treatment, mariculture wastewater irrigation decreased growth of the two plants and reduced contents of nitrogen and phosphorus (NP), chlorophyll (CHL) and soluble protein (SP) in the plant aboveground parts, and decreased more obviously with the increasing of the ratio of mariculture wastewater. However, the relative electrical conductivity (REC) and malondialdehyde (MDA) content increased with the increasing of the proportion of mariculture wastewater, and the increase of S. salsa was more obviously. (3) Treatment of 1:1 mariculture wastewater irrigation increased plant DW and CHL content, NP content of aboveground plant, and increased the activities of antioxidase, endopeptidase, carboxypeptidase, superoxide dismutase (SOD) as well as peroxidase (POD) and contents of SP and free amino acid (FAA) in different degrees. Moreover, with the increasing of the proportion of mariculture wastewater, the above indicators of the two plants decreased in various degrees. To sum up, 1:1 mariculture wastewater treatment could effectively promote chlorophyll synthesis in two plants, increase activities of SOD and POD, reduce MDA accumulation, reduce cell membrane damage, accelerate plant growth and increase NP uptake. The physiological response of S. vsalsa to the concentration of mariculture wastewater was more sensitive than that of S. bigelovii. The application of 1:1 aquaculture wastewater could largely replace the application of fertilizers, thereby reducing environmental pollution.

Abstract:The effects of drip irrigation frequency on soil physical and chemical indicators and cotton yield under subsoiling were studied, which provided a theoretical basis for optimizing the drip irrigation system in cotton fields of Xinjiang. In this study, three different drip irrigation frequencies (4 days/times, 7 days/times and 10 days/times, respectively) and 3 600 m³/hm² as the total irrigation amount were selected. The experiment was carried out under the mechanical subsoiling of 40 cm from May to September of 2016 and 2017 in the Tarim Basin. The soil bulk density, compaction, water content, salt content and yield components in 0-60 cm soil layer of cotton field were determined and analyzed. The results showed that during the growth period of cotton, the soil bulk density in 0-40 cm soil layer showed a trend of 10 days/times > 4 days/times > 7 days/times, and in 40-60 cm soil layer the value of the 4 days/times treatment was slightly higher. The soil bulk density and compaction of 0-60 cm soil layer were maintained at a low level in 7 days/times treatment. Under different soil depths, the soil water content of 7 days/times treatment maintained at a higher level during every growth period. The average value in two years was 14.1% and 18.0% higher that of 4 days/times and 10 days/times treatment, respectively. In the 0-60 cm soil layer, the soil salinity during the growth period was 4 days/times > 7 days/times > 10 days/times treatment. With the decreasing of drip irrigation frequency, the peak of soil salinity decreased gradually, and an obvious salt accumulation area was formed at the depth of 20-40 cm. Under different drip irrigation frequencies, the number of bolls per plant, single boll weight and seed cotton yield were the highest in 7 days/times treatment, and the lowest in 4 days/times treatment. Compared with 4 days/times and 10 days/times treatment, the average seed cotton yield in two years in 7 days/times treatment was increased by 12.1% and 10.0%, respectively. Therefore, moderate drip irrigation frequency (7 days/times) was conducive to maintaining the favorable soil cultivation environment and suitable water and salt environment for crop growth, which could promote the formation of cotton yield.

Abstract:In order to investigate the effects of salt and alkali stress on growth and dry matter accumulation of processing tomato, different salt content soils (CK:1.5 g/kg, S1:4 g/kg, S2:7 g/kg and S3:10 g/kg) were prepared by barrel planting test, the growth index, physiological index, dry matter accumulation and yield of processing tomato under saline alkali stress and drip irrigation condition were studied. The results show that the treatment of S1 promoted the growth index, net photosynthetic rate, transpiration rate, stomatal conductance, leaf water use efficiency and chlorophyll content of processing tomato, but there was no significant difference between this treatment and CK (P>0.05). S2 and S3 treatments had a certain degree of inhibition on the above indicators, most of the maximum or minimum values appeared in S3 treatment, however, at the later growth stage, the stomatal limitation values of processing tomato decreased in the high salinity treatments of S2 and S3, which were generally lower than those of S1 and CK treatments (P<0.01), indicating that the decline of photosynthetic capacity of processing tomato under high saline alkali stress at the later growth stage was mainly caused by the stomatal closure of the leaves, and which was caused by high saline alkali stress. S1 treatment increased the yield of processing tomato by 2.1%, while S2 and S3 treatments reduced the growth of processing tomato by 18.7% and 65.4% respectively. The first stage of fruit expansion was a very important period for the growth and development of processing tomato. At this stage, the processing tomato grew rapidly and the accumulation rate of dry matter was accelerated, reaching the maximum value of the whole growth period. The research results could provide theoretical basis for cultivation and management techniques of processing tomato in saline alkali soil of Xinjiang.

Abstract:The effects of γ-PGA (0.1%, 0.2%, 0.3% and 0.4%) application on soil agglomeration structure, soil nutrient balance, spinach yield and economic benefit were studied by pot experiment. The results showed that with the increasing of γ-PGA application rate, the water-stable aggregates (WR_0.25), the average weight diameter (MWD) and geometric mean diameter (GMD) increased, while the agglomerate destruction rate (PAD) and the fractal dimension (D) decreased, which indicated that γ-PGA had a significant effect on improving soil agglomeration structure. With the increasing of γ-PGA application rate, the absorption of nitrogen, phosphorus and potassium by spinach decreased, while soil nutrient residue and surplus amount increased, and the apparent loss of nutrients decreased. Among the five treatments, the soil nutrient balance condition of the 0.1% application treatment was the best, while the 0.4% application rate had a negative effect on crop nutrient absorption and soil nutrient balance. Spinach yield and economic benefit decreased significantly with the increasing of γ-PGA application rate, and the yield in 0.4% application treatment decreased by 42.98% compared with the control (field without adding γ-PGA). The fitting results of the spinach economic benefits showed that the profit of the treatment applicated 0~0.1% γ-PGA was higher than that of the treatment without γ-PGA. In summary, the 0.1% application rate was better for improving soil structure and nutrient balance, promoting crop yield and crop nutrient absorption, which provided a theoretical reference for the further application of γ-PGA in actual production.

Abstract:In order to study the denitrification and N₂O production rate of sediments in the Dongyu River in spring, the sediment and surface water samples were collected along the Dongyu River in May, 2017. The acetylene inhibition method and incubation method were applied to determine the denitrification potential, denitrification rate and N₂O production rate. The N₂O diffusion flux was estimated by using the headspace equilibrium method and two-layered diffusion model. Moreover, the physicochemical properties of sediment and surface water were also analyzed to discuss the main influencing factors by using correlation analysis. The results showed that denitrification potential of the spring sediments in Dongyu River was 7 305.8~26 947.7 μmol/(m²·h), but from upstream to downstream, it tended to increase first and then decrease. The denitrification rate of sediment was 86.6~694.2 μmol/(m²·h), which was significantly lower than the denitrification potential at the same site (P < 0.01), moreover the change of the denitrification rate along the Dongyu River was not in accordance with the change of denitrification potential. The denitrification rate was only significantly positively correlated with the NH₄⁺ concentration in the sediments (P < 0.05), which indicated that the denitrification rate of sediment might be synthetically affected by the physicochemical properties of the sediments and surface water, and also there might be coupling effect of nitrification and denitrification in the water body. The N₂O production rate was 19.8~144.3 μmol/(m²·h), and the diffusion flux of N₂O varied from 170.9~667.8 μmol/(m²·h), which indicated that the water body of the Dongyu River was the source of N₂O emission to atmosphere. The diffusion flux of N₂O was significantly higher than the N₂O production rate of the corresponding point (P < 0.01), and it was significantly positively correlated with the concentrations of DO and NO₂^- in the overlying water (P < 0.05), which suggested that besides the N₂O produced from the sediment, the transformation of nitrogen in the overlying water was also an important pathway to discharge N₂O to atmosphere from the Dongyu River in spring.

Abstract:The effect of water retaining agent (Guilspare) of different dosage (0, 2, 4 and 6 L/m²) combined with Pisum sativum Linn returning to field on soil water retention capacity, fertilizing ability, tobacco agronomic and economic characters and chemical composition were investigated in town of Pingding. The results showed that water retaining agent significantly slowed the water loss process of soil, soil retention capacity were 4 L/m² > 6 L/m² > 2 L/m². Water retaining agent reduced soil pH, increased the contents of soil organic matter, total nitrogen, total phosphorus, available nitrogen, available boron and potassium, 4 L/m² water retaining agent combined with green manure returning enhanced soil organic matter content of 6.07~28.3 times compared to single green manure return, soil fertility improved mainly because of the increased biomass of Pisum sativum Linn. 4 L/m² water retaining agent with Pisum sativum Linn returning to field increased the thickness or weight of tobacco leaves which improved the quality of flue-cured tobacco. The rose output of 4 L/m² treatment was by 10.30%. As to the influence of water retaining agent with Pisum sativum Linn returning on chemical composition of flue-cured tobacco, the nitrogen and potassium content in middle leaves were 1.67% and 2.24% processing with 6 L/m² water retaining agent with Pisum sativum Linn return, had reached the level of high-quality tobacco (the total nitrogen content of 1.5%~2.5%, potassium >2.0%), furthermore, it reduced the ratio of sugar and nicotine, increased the ratio of chlorine and potassium, by which increased the coordination of acid and alkaline substances in flue-cured tobacco. The application of water retaining agent with green manure returning increased the comprehensive quality of the lower leaves, and reduced the quality of the upper and the middle leaves, it might be caused by the shortage of soil moisture and fertility supplied to the middle and upper leaves in soil of newly reclaimed land.

Abstract:Taking seven-year-old Luxing nectarine as test material, and the field smearing test was carried out and the ¹⁵N isotope tracing technique was applied to explore the effects of different concentrations of nano-carbon and the same concentration of urea solution (0 μg/mL+0.2%, 50 μg/mL+0.2%, 100 μg/mL+0.2%, 200 μg/mL+0.2%, expressed as CK, NC50, NC100 and NC200, respectively) on the growth, nitrogen absorption and distribution in the spring main shoots and leaves of peach, in order to provide new ideas and useful references for the application of carbon nanometers in the cultivation of peach trees. The solution was coated with some leaves. The results showed that compared with the control, the leaf area and the chlorophyll content were significantly increased after application of nano-carbon. The net photosynthetic rate, transpiration rate and stomatal conductance of the leaves in NC200 treatment increased by 15.8%, 30.0% and 12.4% compared with the control, respectively. The application of nano-carbon promoted the dry matter accumulation of the new peach shoots. The treatments of NC100 and NC200 increased the dry matter accumulation by 10.5% and 12.9%, respectively, compared with the control, and increased the total nitrogen content of the new shoots. High concentration of nano-carbon (NC200 treatment) increased the nitrogen uptake ability of new organs (Ndff value). With the increasing of nano-carbon concentration, the nitrogen utilization efficiency increased significantly. The nitrogen utilization rate of NC50, NC100, NC200 treatments increased by 13.6%, 29.5% and 40.0%, respectively, compared with the control. In addition, the nitrogen distribution rate in new leaves of NC200 treatment was the highest, reaching 19.55%, and the nitrogen distribution rate of NC50, NC100 and NC200 treatments were 4.5%, 16.2% and 17.1% higher than that of the control, respectively, and the differences were significantly. The above results indicated that nano-carbon could promote the absorption and utilization of nitrogen in new shoot leaves, effectively improve chlorophyll content, photosynthetic efficiency and local nitrogen utilization rate of new shoots, affect the distribution of nitrogen in different parts of shoots, and promote the transfer of nitrogen to the growth centers (new tender leaves).

Abstract:Taking the grassland sandy soil of East Wuzhumuqi as the research object, and simulating mercury deposition, orthogonal experiment was adopted. The effects of soil/solution ratio, initial mercury concentration, pH, humic acid and concentration of sodium nitrate on the adsorption of grassland sandy soil for HgCl₂ were studied through the method of orthogonal experimental design. The mercury determination in soil were determined by water bath digestion atomic fluorescence spectrometry. The results showed that the smaller the soil/solution ratio was, the larger the initial mercury concentration and the stronger the soil adsorption capacity. The amount of mercury adsorbed by soil was affected by the amount of humic acid, the concentration of sodium nitrate and solvent pH, and the adsorption amount increased first and then decreased with the increasing of the above three factors. When the solvent pH was 7.5, the concentration of exogenous humic acid was 0.6 mg/g and the concentration of sodium nitrate was 0.08 mg/L, the soil adsorption capacity reached the maximum. The factors affected the adsorption of sand for HgCl₂ followed the order of initial mercury concentration > soil/solution ratio > pH > sodium nitrate concentration > humic acid content. Fitting experimental data showed that the accumulation behavior of mercury in sandy soil accorded with the adsorption kinetics process and well correlated with Lagergren quasi-second-order kinetic model, which indicated that the adsorption process was mainly chemical adsorption and the adsorption process was irreversible.

Abstract:For understanding the effect of ferrous iron addition on contaminant removal in different layers of horizontal subsurface flow constructed wetlands, the nitrogen and COD removal and their mechanisms were investigated in this study. The results showed that addition of ferrous iron was beneficial to the removal of total nitrogen, nitrate nitrogen and ammonium nitrogen, and the removal of nitrogen was optimized at the ferrous iron concentration of 50 mg/L. However, the excessive ferrous iron addition inhibited nitrogen removal, especially for the removal of ammonium nitrogen in the lower layers, while the nitrogen removal with ferrous iron addition was greater than that without ferrousiron. As well, ferrous iron addition altered the layering effect of the three inorganic forms of nitrogen. At the beginning of the experiment, ferrous iron addition improved the COD removal, affecting the COD removal in the different layers. Iron concentrations in the different layers dropped rapidly after the input of ferrous iron, while pH values in the effluent increased first and then kept in a stable trend due to the valence structure and hydrolytic characteristics of iron. The pH value in the lower layer was lower than those in the upper and middle layers. Iron properties also caused the changes of oxidation reduction potential (ORP) in different layers. Addition of ferrous iron promoted the layering effect of ORP, but slowed down the decrease of ORP.

Abstract:In order to explore the effect of bermuda grass root exudates on migration and bioavailability of Pb in the fluctuation zone, low molecular weight organic acids secreted by bermuda grass roots of the dominant plants in the fluctuating zone of Three Gorges Reservoir area were selected, and the effects of root exudates on the total amount of Pb in contaminated soil and overlying water and the occurrence forms of Pb in soil were investigated in the dry and wet alternate environment through simulation tests. The results showed that in the wet and dry alternate environment, the Pb content in the topsoil decreased, the content of Pb in the bottom soil increased. After two times of wet and dry alternating, the Pb content in topsoil of the different treatments followed the order of mixed acid > citric acid ≈ acetic acid > malonic acid > control, the Pb content in the bottom soil was sorted as mixed acid > citric acid ≈ acetic acid > malonic acid > control. Carbonate-bound Pb and iron-manganese oxidized Pb in surface soil were the main reasons for the decrease of total Pb content, maximum reduction rates was 24.89% and 19.04% respectively. However, in the treatments added low molecular weight organic acids, the contents of Fe-Mn oxidized Pb and organic bound Pb in surface soil were higher than those in the control, while the exchangeable Pb content was lower than that of the control. Moreover, organic acids promoted the increase of contents of Pb in the carbonate bound state and Fe-Mn oxidation state in the bottom soil. During the two flooding process, the content of Pb in overlying water both increased first and then decreased, low molecular weight organic acids inhibited the release of Pb from soil to overlying water. In general, in the wet and dry alternate environment, the root exudates of bermuda grass reduced the environmental risk of Pb in topsoil.

Abstract:In order to provide scientific basis for food safety in rice fields, a field trial was conducted in Changsha, Hunan Province to investigate the effects of biochar amendment on the form of cadmium (Cd), the uptake and distribution of Cd and soil fertility of rice field polluted by Cd. Five biochar application treatments (0, 10, 20, 30 and 40 t/hm²) were set to analysis the effects of the biochar amendment on the migration of Cd in the soil and the distribution of Cd in the rice organs. The results showed that the biochar reduced the accumulation of Cd in the rice organs by passivating the acid-soluble Cd into the reducible Cd in the soil, and the amount of passivation increased with the increasing of biochar, the acid-soluble Cd decreased by 3.83%~19.08% in biochar treatments compared with CK. After the biochar applying, the translocation coefficient of Cd for stem to root and brown rice to stem were decreased by 4.23%~9.30% and 1.39%~8.33%, respectively. The decision analysis showed that the content of the acid-soluble Cd in soil directly affected the Cd content in the brown rice, and was regulated by soil pH and organic carbon in the soil. In conclusion, biochar amendment could improve the soil fertility and decrease the Cd bioavailability in the Cd polluted rice field. The addition of 20 t/hm² biochar could be taken as a reference standard for remediation of the rice field polluted by Cd around the research area.

Abstract:In order to find out the effects of different potassium (K) fertilizer on cadmium (Cd) in soil-crop system under the condition of reclaimed water irrigation, the field experiment was conducted to study the effects of different K fertilizer treatments on the Cd content of tomato plants, fruits, rhizosphere soil and non-rhizosphere soil. The results showed that under the condition of reclaimed water irrigation, applying K fertilizer could increase the yield of tomato fruits, the effect of KCl on the tomato fruit yield was more obvious than that of K₂SO₄, and the yield was increased by 6.10%~24.00% and 1.36%~13.16%, respectively, compared with the treatment without K fertilizer. The Cd content of tomato fruit in the treatment without K fertilizer was lower than that of the no fertilization treatment, but the decrease range was less than that of the treatment with K fertilizer. The Cd content of tomato fruit treated with KCl was lower than that treated with K₂SO₄, and the Cd content decreased by 58.33% and 8.33%, respectively, compared with the treatment without K fertilizer, and the content of Cd in all treatments did not exceed 0.05 mg/kg limit value. The pH value and the total Cd content of soil in the treatment without K fertilizer was lower than that in the treatment without fertilizer, but the decrease range was less than the treatment with K fertilizer. The available Cd increased. When KCl and K₂SO₄ were applied, the available Cd decreased compared with no fertilization treatment, and the total Cd content, available Cd content and the pH value in rhizosphere soil and non-rhizosphere soil were lower than those of treatment without K fertilizer. When the KCl was applied, the total Cd content of rhizosphere soil and non-rhizosphere soil decreased by 2.96%~3.11% and 5.75%~14.22%, respectively, and the available Cd content decreased by 10.75%~16.19% and 13.98%~28.74%, respectively. When the K₂SO₄ was applied, the content of total Cd in rhizosphere soil and non-rhizosphere soil decreased by 4.14%~5.90% and 8.10%~8.29%, respectively, and the available Cd content decreased by 15.97%~20.55% and 19.91%~24.70%, respectively. Therefore, under the condition of reclaimed water irrigation, the distribution and biological effectiveness of Cd in plant-soil system could be regulated by selecting appropriate K fertilizer. Compared with KCl, the application of K₂SO₄ could reduce the total Cd content and the available Cd content.

Abstract:Heavy metals mixed with toxic organics are increasingly contaminating soil with the development of the industry and the modernization of agricultural production, making remediation of the contaminated soils an urgent and challenging task. In this study, we set up 4 treatments with sandy loam as the test object:(1) Control group, co-contaminated soil (CK); (2) No fertilizer group, co-contaminated soil + ryegrass (NF); (3) Nitrogen fertilizer group, co-contaminated soil + ryegrass + nitrogen fertilizer (F1); (4) Nitrogen fertilizer and phosphate fertilizer group, co-contaminated soil + ryegrass + nitrogen fertilizer and phosphate fertilizer (F2). In order to provide a preliminary theoretical basis for remediation of contaminated soil and environmental impact assessment, we studied the effects of ryegrass and fertilization on microbial activity in oil, lead and cadmium co-contaminated soil. The results showed that both ryegrass and fertilization had positive effects on the soil basal respiration and microbial biomass carbon in the co-contaminated soil. Compared with the control, the peaks of basal soil respiration in NF, F1 and F2 increased by 20.94%, 24.41% and 42.69%, respectively. The effects of nitrogen and phosphate fertilizer (F2) on soil basic respiration were most significant. On the 10th day, the peaks of soil microbial biomass carbon in NF, F1 and F2 increased by 26.92%, 127.43% and 181.89%, respectively, indicating that fertilization treatments were better than non-fertilization. Various soil enzymes had different responses to ryegrass and fertilizer application. The activities of FDA hydrolysis were restrained in NF, F1 and F2, while the application of nitrogen fertilizer could maintain the dehydrogenase activity in the oil-lead-cadmium co-contaminated soil at a certain time. Fertilization could continuously and effectively improve and maintain the activity of urease in the oil-lead-cadmium co-contaminated soil. But there was little impact on the catalase activity. These findings implied that the soil microbial biomass, soil microbial biomass carbon and soil enzyme activity were enhanced by the application of nitrogen and phosphate fertilizer. It meant that planting ryegrass with nitrogen and phosphate fertilizer could promote soil pollutant removal and soil quality improvement.

Abstract:This study was to explore the feasibility of the biochar prepared from fungal residue as raw material for remediation of cadmium (Cd) contaminated soil. A pot experiment was carried out, and Letinous edodes (Berk.) sing residue biochar (SC) and Pleurotus ostreatus (Fr.) Kummer residue biochar (PC) were taken as the research objects, the effects of SC and PC on the physical and chemical properties of Cd contaminated soils, distribution of different forms cadmium in soils, Chinese cabbage growth and Cd accumulation were measured and analyzed. The application rates of 0.5%, 1% and 2% biochar (w/w,%) were set up. The results showed that SC and PC significantly increased soil pH and organic matter (SOM). Compared with the control, 2% biochar application could increase soil pH by 1.05 and 1.10 units, respectively; and increased soil organic matter (SOM) by 80.6% and 61.2%, respectively. Application of SC and PC reduced the content of soil exchangeable Cd and increased the residual Cd concentration. Correlation analysis showed that soil exchangeable Cd was significantly negatively correlated with pH, SOM and sucrase. Compared with the control, Cd accumulation in Chinese cabbage was significantly reduced by 57.5% and 54.1%, respectively, in 2%-SC and 2%-PC treatments. Compared with the control, the yield of Chinese cabbage was increased by 53.4% and 41.6%, respectively, in 1%-treatments, indicating that high dosage of fungal residue had negative effect on the growth of Chinese cabbage. On the whole, SC and PC could improve soil properties, reduce the toxicity of Cd to plants, and promote growth of Chinese cabbage.

Abstract:In order to systematically estimate the effects of plant fiber blanket on soil and water conservation under different rainfall intensities and on soil amelioration, simulated rainfall experiments and filed monitoring were conducted. In the simulated rainfall experiments, four rainfall intensities were set up and three types of plant fiber blankets were tested. The designed rainfall duration was 60 min. During the rainfall, runoff and sediment were collected every 5 min, of which the runoff volume and sediment yield were measured. In the field monitoring, three plots covered with straw blanket which were constructed in 2007, 2010 and 2013, respectively, and another three plots covered with coir blanket, mixed coir-straw blanket and straw blanket, respectively, which were constructed in 2014, were used to estimate the effects of the plant fiber blanket type and the time after constructed on soil's physical and chemical properties. The results showed that under 47 mm/h and above rainfall intensities, coir blanket, mixed coir-straw blanket and straw blanket could effectively reduce erosion and runoff, and the average soil loss reduction benefit was 94.92%, 86.06% and 83.42%, respectively, and runoff was reduced by 31.59%, 45.02% and 52.44%, respectively. This indicated that the efficiency of erosion reduction was apparently better than that of runoff reduction. The three kinds of plant fiber blankets had the highest effect of reducing erosion and runoff under 47 mm/h rainfall intensity. The highest erosion reduction efficiency was coir blanket (97.54%), and mixed coir-straw blanket had the highest runoff reduction efficiency (88.26%). With the increasing of rainfall intensities, both the efficiencies of erosion reduction and runoff reduction decreased, and the efficiency of runoff reduction decreased faster. As time after plant fiber blanket constructed prolonged, the physical and chemical properties of the soils covered with plant fiber blanket were gradually improved. Among the three types of plant fiber blankets, mixed coir-straw blanket was the best in soil amelioration after one year's conduction.

Abstract:This study was an exploration into monitoring technology of summer corn canopy SPAD values. A small lysimeter was used in the experiment to monitor spectral reflectivity of summer corn and SPAD values of plant canopy, which provided the basis for investigation of the responsive relationship between canopy spectral information and SPAD values. From this relationship, the sensitive wave band and the optimum spectral index were determined for the SPAD values of the summer corn under investigation. The findings suggested that the canopy spectral reflectivity decreased with the increase of SPAD values in the visible light band, but increased with the increase of SPAD in the near infrared band. The band to which SPAD was most sensitive was 700 nm and 690 nm when monitoring the original spectrum and the first differential spectrum respectively and the correlations with SPAD values were -0.498 (p < 0.05)and -0.538 (p < 0.01). The multivariate stepwise regression analysis found an optimum band combination of 405 nm, 408 nm, and 700 nm. From 73 published spectral indices, five indices, i.e., (SDr-SDb)/(SDr+SDb), MCARI//OSAVI, TCARI/OSAVI, SDr/SDb, and MTCI, were chosen because they produced a higher correlation with SPAD values of summer corn canopy. Among the five indices, the most suitable index was found to be (SDr-SDb)/(SDr+SDb), and the correlation coefficient was as high as 0.697 (p < 0.01) in the whole growth period. A combinational regression model of SPAD, built from sensitive band, spectral index, and optimum band, produced the following simulation performances in descending order:optimum band combination, spectral index, original spectral reflectivity, and first differential spectrum. A quadratic polynomial model built from (SDr-SDb)/(SDr+SDb) index, and a combinational linear regression model built from 405 nm, 408 nm, and 700 nm bands, were recommended as suitable models for spectral monitoring of summer corn canopy SPAD values.