Abstract:Saline-alkaline soil is an important reserve resource of arable land in our country. Saline-alkaline soil management and agricultural utilization play an important role in ensuring the absolute safety of rations, maintaining the stability of existing arable land, and adhering to the safety bottom line of basic food self-sufficiency. Biochar, which is an environmentally friendly soil amendment, has a great prospect in promoting the sustainable development of agriculture. However, most of the existing researches focused on the improvement effect of biochar in neutral and acidic soil, and lacked of in-depth research and systematic summary on the improvement effect of biochar in saline-alkaline soil. This article comprehensively analyzed the research progress of biochar in physical properties, chemical properties, nutrient utilization and microorganisms in saline-alkaline soil, summarized the possible mechanism of biochar in saline-alkaline soil amelioration. The application prospect of biochar was prospected in order to provide reference for ecological management of saline-alkaline soil.

Abstract:In order to explore the spatial effects of different hedgerow patterns on soil physical and chemical properties and soil erodibility, this study took Zhangjiachong Soil and Water Conservation Experimental Station in Zigui County of the Three Gorges Reservoir Area as the research area, and selected the economic woodland plot (H1) and agricultural land plot (H3) as the control plot of "hedgerow and economic woodland plot" (H2) and "hedgerow and farmland plot" (H4) respectively. The soil physical and chemical properties were compared and analyzed in three slope positions (up, middle and down slope) and two soil layers (0-20 and 20-40 cm). The results showed that:(1) In the same plot, the spatial variations of soil mechanical composition and soil nutrient content were obvious, and the difference was significant (p<0.05). The soil mechanical composition was mainly composed of sand (59.01%~63.51%) and distributed in the upper slope, while the soil fine particles mainly distributed in the middle and lower slopes. The soil nutrients in 0-40 cm soil layer were downhill > middle slope > upper slope, and the average content of total potassium was 3.75%~19.61% higher than that of the control plot. (2) In different plots, the contents of soil fine particles and soil nutrients in hedgerow plot was higher than those in non hedgerow plot, and the proportion of soil fine particles was as follows:H4 plot (39.94%) > H2 plot (38.92%) > H1 plot (38.34%) > H3 plot (37.84%). There was a negative relationship between the K values of soil erodibility and the fine particles contents. The larger proportion of soil fine particles, the smaller the K value, the more difficult soil erosion occurred. The soil of H4 was less likely to be eroded than that of H2. (3) With the increase of soil organic matter, clay, total nitrogen and total potassium contents, soil erosion resistance could be effectively enhanced. Soil erodibility K value of soil erodibility was significantly positively and negatively correlated with silt and clay (correlation coefficients were 1.000, -0.708), but not with sand, organic matter, total nitrogen and total potassium (p>0.05).

Abstract:The existence of subsurface water flow will aggravate the process of soil erosion. Soil detachment rate is an important physical parameter of the soil erosion prediction model, and the response of detachment rate to subsurface water flow is worthy to study in further. The characteristics of rill detachment of purple soil under different conditions (three subsurface water saturation depths of 5, 10 and 15 cm, three slope gradients of 5°, 10° and 15°, and three flow discharges of 2, 4 and 8 L/min) were studied by using limited rill simulation erosion test. The experimental results showed that the rill detachment rate decreased exponentially and linearly with the gully length and sediment concentration at different saturation depths of subsurface water, respectively. Detachment capacity reached its maximum value at subsurface water saturation depth of 15 cm and decreased with the decreasing of saturation depth of subsurface water. The multiple nonlinear regression equations showed the rill detachment rate was positively correlated with flow discharge, slope gradient and saturation depth of subsurface water, and the standardized coefficients were 1.14, 0.72 and 0.36, respectively, indicating that the rill detachment rate was more sensitive to flow discharge than slope gradient under the condition of subsurface water flow. The study provides some theoretical basis for the rill erosion mechansim under the effect of subsurface water flow in purple soil.

Abstract:In order to study the changes of the hydraulic characteristics of overland flow, a series of laboratory flume simulation experiments were conducted on smooth and vegetated beds under three slope gradients, eight flow discharges and four vegetation spatial patterns. The results showed that:(1) The water level of grass covered slope was 1.02~1.38 times that of smooth glass slope, and the flow velocity was 6.52%~36.73% slower than that of glass covered slope. With the increase of flow discharge and slope gradients, the velocity increased with a power function (R²>0.95). (2) There was a significant linear positive correlation between Reynolds number and discharge (R²>0.99), but no significant correlation between Reynolds number and slope gradient and grass cover pattern. Grass cover effectively reduced Froude number on slope. (3) With the increase of discharges and slope gradients, the overland flow pattern of grass-covered slope changed from laminar-slow or rapid flow to turbulent-rapid flow. (4) With the increase of discharges, the overland flow resistance coefficient decreased with a power function (R²>0.86). Slope gradient had no significant effect on resistance coefficient (p>0.05). (5) The effect of raising water level was random pattern > patch > grass square > belt. The effect of slowing down velocity was random pattern > belt > patch > grass square. Froude number on slope was patch > belt > grass square > random pattern. The ability to resist erosion was random pattern > grass square > belt > patch.

Abstract:We take the representative farmland-type and woodland-type depression small watersheds in the Qingmuguan karst valley region as the research object, and start from the depression sediments, the depth distribution characteristics of ¹³⁷Cs specific activity, HCHs, organic matter, clay content, and bulk density of the sediments in each depression profiles were studied. ¹³⁷Cs tracer method and HCHs were applied to sediment dating, and the evolution characteristics of soil erosion in karst depression small watershed in the past 60 years was traced, and its driving factors were discussed. The results show that:(1) Only a few sediment profiles had detected ¹³⁷Cs and HCHs in the farmland depressions of Fort Yard. The depth distribution of ¹³⁷Cs and HCHs could not be used for sediment dating, which reflected that the developed sinkhole had a great impact on the sediment profile. (2) The sand production modulus of the Longdongcao farmland depression in 1963-1983 and 1984-2019 were 231.78 and 82.04 t/(km²·a), respectively, while those values in Laodong village woodland depression small watershed were 68.79 and 39.46 t/(km²·a), respectively, indicating that the ecological environment of the basin has been significantly improved. Compared with 1963-1983, there was no significant change in the average annual precipitation in the region from 1984 to 2019. The sand yield modulus of the two small watersheds both decreased significantly, indicating that the sand yield intensity of the basin in the past 60 years was mainly controlled by land use, water and soil conservation measures and other human activities. (3) The peak value of ¹³⁷Cs and HCHs of profile, surface sediment ¹³⁷Cs, HCHs values and watershed sand yield modulus in different periods of Longdongcao depression were significantly greater than those of the Laodong village depression. It was mainly caused by the difference in sand production intensity under the influence of human activities, which conducted in the cultivated land and woodland type small watershed of the two depressions. In addition, the combined tracer method of ¹³⁷Cs and HCHs could be used to assess the temporal changes of sediment yield in the southwestern karst basin.

Abstract:The quantitative research on the contribution rate and the future deposit potential of check dams in the Yanhe River Basin has important reference value for evaluating the construction benefits of check dams. Based on the runoff and sediment transport data of the Yanhe River Basin from 1952 to 2018 and the data of the construction period, control area, total storage capacity, and the sedimentation storage of the key check dams in the 2011 National Water Conservancy Census, the inverse calculation model for the sediment retention capacity of the key check dam was established. The annual sediment retention and sediment reduction contribution rate of the key check dams in the Yanhe River Basin were calculated, and the future sediment retention years of the key check dams was predicted. The results showed that the annual average sediment interception of the key check dams in the Yanhe River Basin continued to increase in different periods, and the average annual sediment interception from 2000 to 2011 was 4.01 million ton per year, which was the maximum value among the different periods. The human activity was the main factor for the decreased annual sediment transport in the Yanhe River Basin, and the contribution rates of the human activity to the sediment reduction in the Yanhe River Basin from 1997 to 2005 and 2006 to 2011 were 63.44% and 84.98%, respectively. The proportion of sediment reduction caused by the key check dams accounting for that caused by the human activities was decreased, from 24.67% of 1997-2005 to 7.46% of 2006-2011. By the end of 2019, the future sediment-retaining period of 62% of the key check dams in the Yanhe River Basin was less than 30 years. Compared with those in the southern region, the key check dams in the northern Yanhe River Basin has the stronger future sand-retaining ability. The results in this study could provide reference for soil erosion control and benefit evaluation, soil and water conservation measures planning and layout, and comprehensive management of the Yanhe River Basin.

Abstract:Surface roughness is one of the important parameters affecting surface erosion, and it is also one of the hot issues in soil erosion research. It is of great significance to study the spatial heterogeneity of surface roughness in Feldspathic Sandstone Region during natural rainfall to explore the response law of soil erosion. In this paper, the spatial heterogeneity of surface roughness of bare Feldspathic Sandstone Region was studied by geostatistics and ArcGIS spatial analysis. The results showed that:the surface roughness showed a moderate variability during one rainfall event. The surface roughness had a strong spatial autocorrelation during one rainfall event. According to the analysis of spatial distribution characteristics, the increase or decrease of surface roughness was obvious in the downhill of the slope, indicating that the changes of the slope were that the top of the slope was scoured, and the bottom of the slope was filled. The contents of sand and silt particles were decreased, but clay increased. The surface roughness changed more obviously at the bottom slope. Therefore, the surface roughness changed with the changes of soil clay particles. Before and after rainfall, soil clay contents and surface roughness showed a positive correlation, which was more strong after rain. The relationship between silt and surface roughness was not significant, and sand and surface roughness showed a negative correlation.

Abstract:In order to explore the effect of freeze-thaw cycle on the ability of black soil aggregate to resist the influence of different damage. the typical black soil of Heilongjiang province was taken as the research object. and the effects of freeze-thaw cycles and the initial moisture content on stability of soil aggregate with different initial size were analyzed through three different crushing processes of LB method. The results showed that the freeze-thaw cycles had significant effect on the stability of aggregates with different size of 1~2, 2~3 and 3~5 mm (P<0.05). The stability of aggregates followed the order of wetting oscillation (WS) > slow wetting (SW) > fast wetting (FW). FW treatment had the greatest damage to the stability of black soil aggregates, while the SW treatment and WS treatment had less damage. At the same time, the initial water content and the number of freeze-thaw cycle had extremely significant influence on the MWD_FW, MWD_SW and MWD_WS of three different sizes aggregates (P<0.01). With the increasing of the number of freeze-thaw cycle, the large aggregate of >0.2 mm was broken and the content of the small aggregate (<0.2 mm) increased. The initial water content had a destructive effect on 2~3 and 3~5 mm aggregates, while for 1~2 mm aggregates, it was helpful to improve the structure and increase the stability of aggregates.

Abstract:Ecological control of non-point source in small watershed is an important means to control agricultural non-point source. Qianjiagou, which is a typical small watershed in Danjiangkou reservoir area, was selected as the object, and the effect of non-point source ecological resistance control system was evaluated by monitoring the water quality at the outlet of the small watershed, monitoring the inflow and outflow water of each control measures, and calculating pollutant load reduction. The results showed that after the ecological resistance control system of Qianjiagou was stable for half a year, the TN, NO₃-N, NH₃-N, COD_Mn and TP in the outflow of the small watershed decreased by 38%, 23%, 63%, 49% and 16%, respectively. Among the resistance control measures, surface flow wetland had higher removal rates of NH₃-N (54%), TP (70%) and TSS (78%), the ecological pond and ecological ditch had higher removal rates of TN (36%, 39%), NO₃-N (43%, 37%) and COD_Mn (63%, 56%), the small artificial wetland had higher removal rates of TN (56%), NH₃-N(85%), COD_Mn (84%), TP(57%) and TSS(87%) and the ecological filter wall had higher removal rate of TSS (81%). The overall reduction rates of COD_Mn, NH₃-N, TN and TP loads by the resistance control system were 56%, 73%, 63% and 59%, respectively.

Abstract:Anji white tea has high economic benefits, and large amount of chemical fertilizer has been applied in Anji white tea, while nitrogen and phosphorus loss in tea garden has been one of main sources of agricultural non-point pollution in the Xitiaoxi River Basin. This study continuously observed the effects of fertilization reduction and inter-row planting of trees on controlling nitrogen and phosphorus loss in the runoff of white tea garden through field runoff plot experiment with two growth cycles. The experiment included four treatments, which were conventional fertilization (CK), nitrogen and phosphorus reduction (T1), phosphorus reduction with inter-row planting of Albizia julibrissin (T2), and nitrogen and phosphorus reduction with inter-row planting of A. julibrissin (T3), and each treatment had two replicates. The results showed that the runoff and sediment amounts of inter-row planting treatments (T2, T3) were significantly less than those of the treatments with no inter-row planting (CK, T1) (P<0.05) in each growth cycle. During the two observation cycles, the cumulative losses of total nitrogen, all nitrogen fractions, total phosphorus and inorganic phosphorus in runoff water of treatment CK were all significantly higher than those of the other three treatments, the cumulative nitrogen outputs in sediment of treatment CK was significantly higher than those of treatment T3, and the cumulative phosphorus outputs in sediment of treatment CK was significantly higher than those of treatment T2 and T3 (P<0.05). Nitrogen loss in white tea garden was mainly with runoff water, and phosphorus loss was mainly with runoff sediment. Reduction of nitrogen and/or phosphorus application, inter-row planting and the combination of the two measures could effectively decrease the runoff loss of nitrogen and phosphorus in the white tea garden, and the combined measures of nitrogen and phosphorus reduction with inter-row planting were more effective. Thus, the fertilization doses of N 270 kg/hm², P₂O₅ 90 kg/hm², and inter-low planting density of 200 plants/hm² A. julibrissin were recommended for the local white tea culture.

Abstract:Ridge and furrow are the important confluence paths in soil erosion of long and gentle slope farmland. It is very important to understand the hydraulic characteristics of ridge and furrow for simulating the soil erosion process of slope farmland in typical black soil area of Northeast China. The main hydraulic parameters and variables of ridge and furrow under different ridge cultivation methods, slopes and rainfall intensities were systematically analyzed using indoor rainfall simulation method. Under different ridge planting patterns, the erosion amount were narrow ridge > wide ridge > no ridge, showing linear positive correlation with the product of slope and rainfall intensity. The variation curve of hydraulic radius with rainfall intensity and slope was logarithmic. The hydraulic radius of wide ridge was 8.4% to 11.6% higher than that of narrow ridge, with an average of 10.0%. Under the same slope and rainfall intensity, the roughness of wide ridge was higher than that of narrow ridge. Moreover, with the increase of slope, the decrease in roughness of wide ridge was weaker than that of narrow ridge. There was a significant difference between the recommended values of roughness in the existing soil erosion models and the observed values in this experiment. Therefore, it is necessary to recalibrate the roughness value for erosion process of long and gentle slope cultivated land under ridge cultivation in this area.

Abstract:In order to explore the technical measures to reduce nitrogen and phosphorus loss in intensive orchards and slow down agricultural non-point source pollution, this study compared and analyzed the effect of drip fertigation and plant hedgerows on reducing nitrogen and phosphorus loss in surface runoff and improving the water quality in field ditch based on field positioning experiments. The results showed that the plant hedgerows increased the minimum daily rainfall of surface runoff, and reduced the frequency of runoff. The amount of surface runoff was reduced by 19.18% compared with the treatment without plant hedgerows. Compared with CK treatment, the TN and TP concentrations in runoff water of the drip fertigation treatment decreased by 31.23% and 25.18%, respectively. The TN and TP concentrations in the plant hedgerows treatment decreased by 16.74% and 13.60%, respectively, and the TN and TP concentrations in the treatment of drip fertigation + plant hedgerows decreased by 52.32% and 43.89% than the CK treatment, which were the lowest in all treatments. The loss fluxes of TN and TP in the treatment of drip fertigation + plant hedgerows decrease by 45.38% and 36.81%, respectively, compared with the CK treatment. In the treatment of drip fertigation + plant hedgerows, the TN and TP concentrations in the ditch water decreased by 23.98% and 26.64%, respectively, compared with the CK treatment. These results indicated that the implementation of drip fertigation combined with plant hedgerows in intensive farmland such as orchards can effectively reduce nitrogen and phosphorus loss in runoff and slow down the discharge of agricultural non-point source pollutants, which has great prospects in practical applications.

Abstract:Taking millet sloping farmland in the Loess Plateau as the research object, through artificial simulated rainfall test, the influence of millet at different growth stages on the erosion process of sloping farmland with different slope gradients was explored, and the characteristics and mechanism of the erosion process of sloping farmland in the Loess Plateau were revealed. According to the current policy of returning cultivated land to forest (grass), rainfall characteristics and millet growth characteristics in the experimental area, artificial rainfall simulation was conducted on millet planting slopes at four growth stages (seedling stage, jointing stage, heading stage and grout stage) under the conditions of 80 mm/h rainfall intensity and four slopes (3°, 5°, 10° and 15°). The results showed that millet had a significant impact on the erosion process of sloping farmland. With the growth of millet, the initial runoff yield time increased, the runoff yield curve tended to be stable in shorter time, and the average runoff and sediment yield intensity decreased, and the runoff and sediment reduction benefit of millet increased gradually. On the 3° and 15° slopes, the initial runoff yield time increased from 5.25 and 1.40 min on bare ground to 12.70 and 7.63 min at the grouting stage, respectively. On the 3° and 15° slopes, the average runoff yield strength decreased to 0.52 and 0.78 L/(m²·min) during the grouting period, and the average sediment yield strength decreased to 0.83 and 2.07 g/(m²·min) during the grouting period. Compared with bare field, runoff and sediment yield decreased by 12.27%~48.24% and 19.90%~84.00%, respectively, from seedling stage to grouting stage. The results could provide a reference for revealing the erosion mechanism of millet sloping farmland in the Loess Plateau and provide a scientific basis for regional high-quality development.

Abstract:For further optimization and rational allocation of soil and water conservation measures, three small watersheds under different land use patterns in loess hilly and gully region was taken as an example. According to the sedimentation profile sampling, siltation layer identification and corresponding relationship with erosive rainfall events, the capacity curve of the check-dams was established combined with 1:10 000 early topographic map and Total Station measurement to estimate the sediment deposition, and then the sediment yield was determined based on the controlled watershed area and performance period. The results showed that:(1) The multi-year average sediment depositions in Dongergou, Yanqiao and Luqu dam-controlled small watersheds under different land use patterns from dam construction to 2016 in the Majiagou catchment of Yanhe River basin were 2 748.80, 4 634.31 and 3 141.17 t, respectively. (2) The multi-year average sediment yields of Dongergou, Yanqiao and Luqu watersheds were 2 432.56, 3 131.29 and 1 794.95 t/(km²·a), which were mild erosion, moderate erosion and mild erosion, respectively. The minimum rainfall of erosion and sediment yield in the dam-controlled small watershed under different land use patterns was greater than 20 mm. (3) Different land use patterns had significant effects on the erosion and sediment yield in small watersheds. The multi-year average sediment yield of Yanqiao watershed with obvious human activities was larger than that of Dongergou watershed with lots of forest and grassland, while the multi-year average sediment yield in Luqu watershed was the smallest with mainly forest and terraces. Thus, it could be concluded that the reasonable configuration of different water and soil conservation measures in loess hilly and gully region is an effective way to reduce erosion and sediment yield in small watersheds.

Abstract:In order to quantitatively evaluate the effect of different root contents on the shear strength of the root-soil composite, the distribution characteristics of the root area ratio of the Bischofia javanica with the increase of buried depth were analyzed. An improved large-box direct shear experiment was carried out on the remolded vertical root-soil composite with seven different root area ratios and four different normal stress levels. The changing rules of the soil cohesion and internal friction angle under different root area ratios were studied. The results showed that the shear strength of the root-soil composite of the Bischofia javanica was increased by 1%~25% compared with the soil without roots. Under the same root area ratio, the shear strength of the root-soil composite increased when the normal stress increased, but with a decreased growth rate. With the increases of the root area ratio, the shear strength of the root-soil composite increased first and then decreased. There was an optimal root content to maximize the shear strength of the root-soil composite. The peak shear strengths under four different normal stress levels are 100, 121, 136, 142 kPa respectively, and the corresponding root area ratios were all 0.20%. When the root content exceeded the optimal value, the attenuation rate of the shear strength was related to the normal stress. The larger the normal stress, the smaller the attenuation. The effect of the root area ratio on enhancing the shear strength of root-soil composite was mainly reflected in the soil cohesion, while its influence on the internal friction angle was small. The results of this study could provide some theoretical bases for stabilizing slopes using Bischofia javanica roots and have positive significance for further understanding the interaction between the arbor roots and soil.

Abstract:The exposed feldspathic sandstone region is one of the main source regions of coarse sandiment in the middle reach of Yellow River. Studying the change law of slope micro-topography under rainfall condition had great significance to guide vegetation construction and reduce coarse sandiment into Yellow River. In this study, taking Baojiagou watershed in feldspathic sandstone region as the research object, through hierarchical clustering method and linear regression method, we divided the types of rainfall and studied their effects on runoff and sediment yield, we also analyzed the change law of slope micro-topography under rainfall condition. The results showed that:(1) The natural rainfall in the research area could be divided into four types, the type Ⅰ was long-duration heavy rain, the type Ⅱ was long-duration moderate to heavy rain, the type type Ⅲ was short-duration heavy rain, and the type IV was short-duration light to moderate rain. (2) Parabolic function correlation were existed between the P of the type Ⅱ rainfall and soil loss amount. There was a polynomial function relationship between I₃₀ of the type Ⅱ rainfall and runoff depth. Polynomial function correlation were existed between the P of the type Ⅲ rainfall and runoff depth and soil loss amount. There was a certain functional relationship between the I₃₀ of the type IV rainfall and the sand content in the water flux. (3) During one rainstorm season, the average value of micro-topography slope grandiant of exposed bed rock slope increased from 22.76° to 23.09°, the rill density on the slope surface increased from 0 to 33.73 m/m². With the continuous development of microtopography of slope surface, which was beneficial to the occurrence of erosion, the runoff and sediment yield on the slope surface increased.

Abstract:Total nitrogen (TN), as one of the cementing substances formed by soil aggregates, can accelerate the transformation among aggregates with different particle sizes. Taking the Wangmaogou small watershed in the Loess Plateau as the research object, the "S" method and the digging section method were used to sample the 0-60 cm soil of slope farmland, grassland, shrubland, forest and terraces. The slope farmland was used as a control to explore the stability of soil aggregates and their TN content under four ecological constructions. The TN contribution rates of soil aggregates were analyzed for different depths (0-20, 20-40, 40-60 cm) and different particle sizes (> 5, 5~2, 2~1, 1~0.5, 0.5~0.25, < 0.25 mm). The results showed that ecological construction significantly increased the content of large soil aggregates. Compared with grassland and forest, the aggregates of > 5 mm in the surface soil were increased by 469% and 438% respectively, and the stability of soil aggregates (MWD, GMD) were increased. In the vertical direction, the stability of the aggregates decreased with the increasing depth. Compared with sloping farmland, grassland, shrubland, forest and terraces could increase the TN content of soil aggregates to varying degrees. Among them, forest aggregates had the highest TN reserves (36.53 kg/m²), and the TN reserves in the shrubland (32.12 kg/m²), grassland (20.30 kg/m²) and terraces (18.62 kg/m²) were increased by 131%, 46% and 34% respectively compared with slope farmland. With the increase of soil depth, the influence of different ecological construction types on aggregate TN content gradually was weakened. With the natural succession process of sloping farmland-grassland-shrubland-forest, the contribution rate of TN by aggregates of < 0.25 mm showed a decreasing trend. Terraced fields could improve the soil structure of sloping farmland to a certain extent. With the particle size range of 5~0.25 mm, the TN content of soil aggregates could reach the level of grassland recovery, but the aggregates of > 5 mm had still relatively large space for recovery.

Abstract:In order to investigate the effects of flow intensities, slope gradient and fractal dimension of erosion sediment particles on soil erosion on slope surface of accumulation body, three soils (aeolian sandy soil, red soil and Lou soil) and four flow intensities (8, 12, 16 and 20 L/min) were selected. Field runoff scouring simulation experiments were carried out on three slopes (28°, 32° and 36°). The results showed that:(1) The interaction of flow intensity and slope had the greatest influence on the average velocity of slope. The velocity of slope flow of the three soils increased by 1.00~1.49 times with the increase of flow intensities and 0.99~1.29 times with the increase of slope. (2) The interaction among flow intensities, slope and fractal dimension of soil particles had the greatest influence on the average runoff yield on slope, while flow intensity had the greatest influence on runoff. The runoff rate and runoff yield of the three soils increased with the increase of flow intensities by 1.09~6.10 and 1.05~5.74 times respectively, and increased with the increase of slope by 0.80~2.59 and 0.82~2.59 times respectively. (3) The interaction between the intensities of flow and slope had the greatest influence on the sediment yield and sediment yield. The sediment rate and sediment yield of three soils increased with the increase of flow intensities, increased by 1.17~5.67 and 1.17~5.20 times respectively, and increased by 0.96~3.32 and 0.94~7.54 times respectively with the increase of slope gradients. These research results could provide a theoretical reference for soil erosion prediction and loss control of engineering accumulation slope with different soil properties.

Abstract:Research on soil hydraulic properties in different positions of the hillslope can provide reference for the prediction of surface hydrological process and ecological restoration in mountainous areas. In this study, undisturbed soil samples were collected from different slope positions in Dalaoling forest region, which was a typical small catchment of the Three Gorges Reservoir area, and the hydraulic parameters such as saturated water conductivity, equivalent pore diameter and water storage capacity were measured. The V-G model was used to fit the soil water characteristic curve to evaluate the soil permeability and water holding capacity of soil at different slope positions. The results showed that the soil infiltration performance of the top position was the best, and the average saturated hydraulic conductivity was 108.54 cm/d, while the average saturated hydraulic conductivity of other four slope positions was 34.81~47.56 cm/d. However, the water content of the top position decreased largely (63.67%) when the suction value increased from 0 to 100 kPa, while the average water content of other four positions decreased by 46.36%~52.07%. The macropore volume ratio of the soil at the top position was 20.95%, and that of the other four points was ranging from 12.27%~16.58%. The percentage of field water capacity in total soil water storage capacity was 45.24% in the top position, which was the smallest, and that of the other four points was 60.08%~65.33%. The V-G model was used to fit the soil water retention curve, and the determination coefficient (R²) of each point was greater than 0.95, which indicated that the fitting effect was good. The saturated hydraulic conductivity was positively correlated with soil macropore volume ratio and sand content, and negatively correlated with silt content and clay content. The parameter α of V-G model was related to air entry values. The smaller α value was, the stronger the water retention capacity was. In the experiment, α value was positively correlated with sand content and macropore volume ratio, and negatively correlated with silt content and clay content. The more sand particles and macropores was, the worse soil water holding capacity was. The value of parameter n affected the curvature of fitting water characteristic curve. The smaller n value was, the smoother the curve was. And n value was positively correlated with sand content and negatively correlated with silt content. The more sand content was, the faster the soil drainage was with the increasing of suction. The soil at the top of the mountain slope had the worst water-holding capacity and the strongest permeability, while the difference of other slope positions was not significant. The results of V-G model fitting were consistent with the measured results.

Abstract:Taking liana vegetation and secondary arbor forest in Yongding (Beijing section) riverside as the research object, this paper studied preferential flow characteristics of the section dyed pictures and infiltration water volume by using the methods of field dyeing tracer, root system analysis, morphological and statistical analysis. The results showed that the depth of matrix flow in the sample plot covered by liana vegetation was 5.48 cm smaller than that in the secondary arbor forest, and the number of channels with preferential flow paths was 67% more than that in the secondary arbor forest. The phenomenon of preferential flow was more obvious in liana vegetation sample plot, and the average dyeing area ratio (34.17%), preferential flow ratio (69.44%) and length index (457.79%) were 9.89%, 18.66% and 25.71% larger than those of arbor forest plot, respectively. In the two kinds of plots, the root length density decreased with the increasing of soil depth. The root length density of 0-10 cm surface soil layer in liana plot was 2.96 times higher than that in secondary arbor forest. The relationship curve between dye area ratio and root length density was well fitted, and the correlation index R² of liana plot was 0.97. Under the same external conditions, the soil under liana vegetation had higher preferential flow degree than that under secondary arbor forest.

Abstract:The investigation of soil saturated hydraulic conductivity and its influencing factors in the alpine region is critical for evaluating water conservation capacity of the fragile ecosystem and constructing regional hydrological modeling. The distribution and influencing factors of soil saturated hydraulic conductivity (K_s) under different land use patterns were studied by measuring soil physicochemical properties and K_s in the 0-30 cm soil layers along a north-south transect in the Eastern part of Qinghai Province. The results showed that the average value of K_s followed the decreasing order of forestland (1.89 cm/h) > grassland (1.62 cm/h) > farmland (1.41 cm/h). The K_s of farmland (0.10~3.92 cm/h) decreased gradually with the increasing of soil depth, while K_sof forestland (0.28~7.69 cm/h) and grass (0.10~5.34 cm/h) land increased first and then decreased with the increasing of soil depth. K_s was significantly correlated with soil physical and chemical properties such as pH, bulk density, porosity, clay content, organic matter content and saturated water content (P<0.05). The multiple regression analysis showed that the K_s pedo-transfer function equations of farmland was obtained using total porosity, non-capillary porosity and saturated water content as input parameters, the K_s pedo-transfer function equation of forestland was obtained by using capillary porosity and non-capillary porosity as input parameters, and the K_s pedo-transfer function equation of grassland was obtained by using bulk density, non-capillary porosity and saturated water content as input parameters. The results could provide reference for the simulation and prediction of K_s under different land use patterns in other alpine regions.

Abstract:The function of sand-fixing is an important index to evaluate the degree of regional ecological security. Studying the temporal and spatial variations and internal differences can provide important reference for improving the ecological environment and promoting the sustainable development of the ecosystem. Based on multi-source remote sensing data of the Beijing-Tianjin sandstorm source region and using the revised wind erosion equation (RWEQ) and GIS spatial statistics technology, this paper evaluated and analyzed the spatial and temporal changes of sand-fixing function and regional difference in the Beijing-Tianjin sandstorm source region from 2000 to 2017. The results showed that:(1) During 2000-2017, the regional sand-fixing function presented an increasing trend, with the average annual sand-fixing amount of 4.006 billion tons and sand-fixing capacity of 56.38 t/hm². Both of them increased with time, and the average annual increase rates were 41 million tons and 58 million t respectively. The sand-fixing capacity of the newly added areas in phase Ⅱ was higher than that in phase I project. (2) In the sub-zone scale, five sub-zones' function of sand-fixing was enhanced, and the increasing of desertification land control area on the Ordos Plateau was most pronounced, with 16.113 5 million t/a. The desertification land control area on the Ordos Plateau and the water conservation and control areas in the Bashang Grassland and Hilly regions in north China were the main function supply area of sand-fixing, accounting for 57.96%. (3) On the pixel scale, the studied region showed a high-low-high variation trend from west to east. During the evaluation period, 54.11% of the region showed an increasing trend in sand-fixing capacity, which varied from 0.10 to 12.22 t/(hm²·a). In addition, 46.83% of the studied region had the higher sand-fixing capacity than 45.00 t/hm², showing a strong function of sand-fixing.

Abstract:The objective of this study was to explore the correlation between characteristics of fractal dimension and soil texture and alkalinity of typical halophytic landscape in the Western Songnen Plain, China. A volume-based fractal model was adopted to calculate the particle-size composition and fractal dimension of the 0-30 cm soil of six typical halophytic landscapes, and the relationships among soil fractal dimension and texture, alkalinity characteristics were analyzed by correlation analysis. The results showed that:(1) Among the six typical halophytic landscapes, the fractal dimension of farmland soil was the smallest (2.35), and that of Artemisia suaeda community soil was the largest (2.61), and the average fractal dimension was 2.48. The fractal dimension increased with the increasing of alkalization degree of halophytic landscape soil. (2) The coarser the soil texture was, the higher the sand content was, and the smaller the fractal dimension value was. The finer the soil texture was, the higher the content of clay and silt was, and the larger the fractal dimension was. (3) Fractal dimension was significantly positively correlated with salt content (r=0.87, P<0.05), especially with HCO₃^- content in salt composition (r=0.89, P<0.01) and total phosphorus content in nutrients (r=0.90, P<0.01). (4) There were also significant correlations among particle-size composition, salt content, HCO₃^- content and total phosphorus. The fractal dimension of different halophytic landscape soils were significantly correlated with soil particle size composition and soil salinity, so the fractal dimensions could be used to reflect soil texture and indicate soil salinization features.

Abstract:In this study, we collected leaf litter of three evergreen coniferous trees, three deciduous broadleaf trees, four evergreen broadleaf trees, and five ferns in the water conservation forests at the middle reaches of the Gan River, and compared the interspecific differences in litter water-holding and water-loss characteristics using the laboratory soaking and water loss experiments. The results showed that, for all species, litter water absorption rate showed a decreasing trend with soaking time in the initial 8 hours, and then did not change with soaking time. Similarly, litter water loss rate decreased with water loss time in the initial 12 hours, and then remained constant. After 24 hours of soaking, fern (202.5%) had higher litter saturated water holding capacity than deciduous broadleaf trees (173.0%), evergreen broadleaf trees (124.6%), and evergreen coniferous trees (86.5%). In addition, both deciduous broadleaf trees (65.4%) and ferns (65.4%) had higher litter water loss capacity than evergreen broadleaf trees (53.6%) and evergreen coniferous trees (42.8%). Both saturated water holding capacity and mean water loss rate of leaf litter were negatively correlated with the initial litter tissue density (R²=0.428 and 0.266, respectively), but positively correlated with the initial specific leaf area (R²=0.488 and 0.398, respectively). These results indicated that litter tissue density and specific leaf area were the important factors controlling the interspecific variations of water-holding and water-loss capacity of leaf litter among plant functional groups. Our observations highlight the importance of understory fern litter to forest water conservation function, which would be helpful to the future evaluation of ecosystem services and development of management practices in the water conservation forests at the middle reaches of the Gan River.

Abstract:Lake is an important factor to maintain ecological balance. As the largest freshwater lake in China, water area of Poyang Lake has been changed due to the advance and prolonged dry season. It is of great significance for the stability of regional ecological environment and economic development to study the variation characteristics and driving factors of water area in Poyang Lake during the dry season. In this study, based on the remote sensing image data of Poyang Lake in dry season from 1973 to 2018, Mann-Kendall trend test, Mann-Kendall mutation analysis and Pettitt mutation test were used to analyze the area change of Poyang Lake during the dry season, and the double mass curve method was used to quantify the effects of the difference of inflow and outflow as well as land use change caused by human activities on the water area of Poyang Lake. The results showed that:(1) During the study period, the water area of Poyang Lake showed a very significant decline in the dry season (P<0.01), the year of the abrupt transition point was 2002 (P<0.01). (2) The difference of runoff in and out of the lake showed an insignificant increase trend over the years. From 1980 to 2015, the land use of Poyang Lake basin showed an increase in industrial and construction land in urban and rural areas, while other land use types showed a decreasing trend. (3) Taking 1977 to 2002 as the base period, the contribution rate of land use change caused by human activities was 87.48% to the change of Poyang Lake's water area during the dry season from 2003 to 2016, which was the main reason for the significant reduction of water area of Poyang Lake in dry season. The results could provide scientific basis for the rational utilization of water resources and the maintenance of regional ecosystem balance in Poyang Lake.

Abstract:Determining the erosive rainfall standard of daily rainfall is an important prerequisite for improving the calculation accuracy of the simple model based on the daily rainfall. The standards of erosive daily rainfall in the Poyang Lake Basin were studied with the method of minimum deviation. The results showed that:(1) The erosive event rainfall standard in Poyang Lake Basin was 14.0 mm, where the coefficient deviation was 1.8%, the loss rate for erosion amount was 2.8% and the mixing index was 14.9%. (2) The monthly rainfall at each station was the highest rainfall in June with an inverted "V" shape; the type of rainfall time spanning two days or more was the most, accounting for 52.4% of the total erosive event rainfall. (3) The erosive daily rainfall standard in the Poyang Lake Basin was 10.0 mm, where the deviation value of the annual average rainfall erosivity between daily and event rainfall was 0.11%.

Abstract:Snow is an important part of water resources in arid regions. Change of precipitation pattern and snow melting caused by climate warming are bound to have an important impact on the runoff process and its components. In this study, Hutubi river basin on the north slope of Tianshan mountains was selected as a typical watershed for snow replenishment in arid region. We used site meteorological observation data and IPCC CMIP5 climate scenario data to drive the improved VIC model of rain and snow partition scheme and snowmelt runoff calculation module, and used observed runoff and MODIS snow cover area data to optimize the model's multi-objective parameters. Then the runoff components, runoff variation characteristics and response mechanism of streamflow to climate change were quantitatively analyzed in Hutubi river basin. The results showed that:(1) The runoff process of the Hutubi river showed a concentrated unimodal distribution in the warm season. Snowmelt runoff, rainfall runoff and glacier runoff accounted for 27.7%, 66.1% and 6.2% of the total runoff, respectively. From 1978 to 2010, under the background of significant increase in temperature and precipitation, little change in snowfall amount, and significant decrease in snowfall proportion, the total runoff and rainfall runoff increased significantly, while snowmelt runoff increased slightly. (2) Under the RCP4.5 climate scenario, it predicts that the temperature in the Hutubi River Basin will increase significantly in the future, precipitation will increase slowly, and snowfall will decrease significantly. Affected by climate change, the total runoff of the basin will increase slowly, in which rainfall runoff will increase significantly, and snowmelt runoff will decrease significantly. The annual distribution of runoff will also change in the future, which will show the decrease of spring runoff amount and peak value, the increase of runoff in dry season and the advance of snowmelt runoff peak. (3) In spring, the proportion of snowmelt runoff is the highest, and its change directly determines the change of total runoff. It estimates that a significant reduction in snowmelt runoff in the future will result in a decrease in total runoff during the irrigation period from March to June, which will further aggravate the contradiction of agricultural irrigation water under the existing agricultural mode.

Abstract:Evaluation the influence of hydropower station construction on landscape pattern and habitat quality was of great significance to improve local ecological environment quality and reduce soil erosion. Taking the surrounding area of Laxiwa Hydropower Station as the research area, based on the land use and DEM data in 2000, 2005, 2010 and 2015, the temporal and spatial evolution law of landscape pattern index in each period of hydropower station construction was analyzed by the moving window method, and the temporal and spatial distribution characteristics of habitat quality were studied by combining with invest model, so as to explore the impact of hydropower station construction on the regional landscape pattern and habitat quality of surrounding areas. On this basis, the spatial autocorrelation method was used to analyze the spatial and temporal clustering degree of habitat quality, and the influence of hydropower station construction on the spatial and temporal clustering degree of habitat quality in surrounding areas in plateau area was discussed. The results showed that:(1) In the middle period of hydropower station construction from 2005 to 2010, the spatial distribution of landscape pattern index changed significantly, while that in the early period of hydropower station construction from 2000 to 2005 and the late period of hydropower station construction from 2010 to 2015 remained almost the same. (2) The habitat quality of the study area was mainly between 0.3 and 0.7, during the middle period of hydropower station construction from 2005 to 2010, the proportion of the area with medium habitat quality increased from 35.15% to 45.26%, and the proportion of the area with good habitat quality increased from 48.23% to 40.28%. (3) Habitat qualities of Moran's I in 2000, 2005, 2010 and 2015 were all positive, showing non randomness in space. The "high-high" spatial aggregation was mainly river and bare land area, and the "low-low" spatial aggregation was mainly sparse grass and construction land area. From 2005 to 2010, the "insignificant" spatial aggregation turned to "low-low" spatial aggregation in the northwest of the hydropower station location.

Abstract:In order to investigate the carbon sequestration and oxygen release capacity of typical plants in the Helan Mountain, the photosynthetic physiological indexes of 10 species of trees, shrubs and grasses were measured by using the portable Li-6400XT photosynthetic apparatus, and the daily carbon sequestration and oxygen release capacity were analyzed. The results showed that:(1) The leaf area, leaf dry weight and leaf area index of Picea crassifolia were significantly higher than those of other plants. The specific leaf area of Carex muliensis was the highest, and showed a rank of herb > shrub > tree. The average daily net photosynthetic rate of Thermopsis lanceolata was the highest, and there was no significant difference between trees, shrubs and grasses. (2) The descending order of daily carbon sequestration and oxygen release capacity per unit leaf area was T. lanceolata, Ulmus glaucescens, Populus davidiana, Cotoneaster hissaricus, Agropyron cristatum, Pinus tabuliformis, Lonicera microphylla, Berberis thunbergii, P. crassifolia, C. muliensis. The descending order of daily carbon sequestration and oxygen release capacity of unit crown width was P. davidiana, P. crassifolia, U. glaucescens, P. tabuliformis, C. hissaricus, B. thunbergii, L. microphylla. The descending order of daily carbon sequestration and oxygen release capacity of a single plant was P. crassifolia, P. davidiana, P. tabuliformis, U. glaucescens, B. thunbergii, C. hissaricus, L. microphylla, T. lanceolata, A. cristatum. The daily carbon sequestration and oxygen release capacity of the four typical stand trees were in a rank of P. crassifolia forest, mixed forest, P. tabuliformis forest, U. glaucescens forest. (3) According to cluster analysis results, the carbon sequestration and oxygen release capacity on the per leaf area of trees (4 species) and shrubs (3 species) were divided into two levels, and herbs (3 species) were divided into three levels, which on the projection area scale of unit crown width of trees (4 species) and shrubs (3 species) were divided into three levels. However, the tree (4 species), shrub (3 species) and herb (2 species) were divided into two levels according to the single plant scale, and on the scale of unit land area of different forest species, four typical forests are divided into two levels. (4) There was no significant correlation between the daily carbon sequestration and oxygen release per unit leaf area of plants and the plant morphological indicators. The daily carbon sequestration and oxygen release per unit canopy projection area was significantly positively correlated with the leaf area index. Moreover, we observed that the daily carbon sequestration and oxygen release per plant was significantly positively correlated with plant height, diameter at breast height and leaf area index. The daily carbon sequestration and oxygen release per unit forest area was significantly positive correlation with stand density. In conclusion, both P. crassifolia and P. davidiana had high carbon sequestration and oxygen release capacity in different scales. In the ecological restoration process of the Helan Mountain in the future, the two species of trees should be given priority consideration, and shrubs and herbs with high carbon sequestration and oxygen release capacity, such as C. hissaricus, should be added to achieve the maximum ecological benefits.

Abstract:The purpose of this article was to analyze the impacts of afforestation in different regions and seasons on the Loess Plateau on the land surface temperature (LST) from 2002 to 2015 and their driving factors (Albedo and evapotranspiration) based on MODIS land cover, LST, Albedo, evapotranspiration (ET) data products and precipitation data. The results showed that during the study period, the cooling effect in the daytime dominated LST change ((-0.78±1.25)℃) and the cooling effect was mainly driven by ET ((0.84±1.35) mm/d). Moreover, the land surface temperature change caused by afforestation was closely related to precipitation, and afforestation would cause a slight warming ((0.03±0.22)℃) in semi-arid regions where the mean annual precipitation was less than 400 mm. In addition, the variations of LST presented a seasonal pattern, that was, the observed cooling effect in spring and summer was greater, while in winter, this effect was weak. The daytime cooling effect was the strongest in spring, followed by summer, winter and autumn. In terms of the nighttime LST, the warming effect in winter was the strongest, followed by spring, autumn and summer. Meanwhile, the correlation between LST variations and ET change(Albedo change) showed that the cooling effect derived by ET offset the warming effect caused by albedo and dominated the daytime LST variations. Such warming impact at night reflected that storage heat during the day was likely to be released at night. Vegetation restoration on the Loess Plateau had a cooling effect, which slowed down the trend of climate warming on a regional scale.

Abstract:At present, the ecological environment construction of the Loess Plateau is facing a new social environment. Vegetation managed with ecological values such as soil and water conservation began to change towards economic-utilization value. How to balance the proportion of land used for soil conservation value and land used for economic-utilization value, and how to optimize the allocation of vegetation space is an urgent theoretical and practical problem needed to be resolved. To solve this problem, this study established a value-trade-off model of watershed development from the perspective of economy-ecology-environment coupling complex system based on grid data expression of watershed. The results showed that the established value-trade-off model could calculate the maximum development benefit of the watershed based on the trade-off between grid development profit and soil loss value, and determine the optimal area threshold of watershed area development, and optimize spatial allocation of watershed vegetation. The decision-making system could provide a reference for watershed development, and help to evaluate the rationality of past watershed development and guide the spatial optimal allocation of vegetation in future watershed development.

Abstract:Based on the InVEST model and water footprint theory, the characteristics and matching status of water service supply and demand in Shiyang River Basin were analyzed, and the spatial heterogeneity of water service supply and demand status and its main driving factors were explored by using geographical detector. The results showed that:(1) From 2010 to 2018, the water service supply capacity was improved, showing a spatial trend of high in the south and low in the north. The total demand for water service showed a significant rising trend, and the demand for water service in irrigated agricultural areas and industrial areas in the middle of the basin was large. (2) The water service supply and demand matching situation was significantly improved during the study period. In 2018, the area that could fully meet the water service supply and demand was increased by 24.9% compared with that in 2010. (3) The interaction between land use types and other influencing factors was the most obvious. In different regions, the explanatory ability of each factor was significantly different. Land use types had the strongest explanatory power for ESDR spatial differentiation in the middle and lower reaches of arid regions with flat topography. However, in the upper reaches of the high and cold semi-arid and semi-humid regions with large surface fluctuations, the explanatory ability of annual precipitation and potential evapotranspiration was constantly enhanced, which became the key driving factor.

Abstract:Forest litter layer, as a unique layer of forest ecosystem, can intercept and absorb precipitation which is called litter water retention capacity. After precipitation, the temporary water of litters will continue to evaporate and infiltrate, adjust the water in the atmosphere and soil to facilitate the next water holding. Seven typical forests of Xiaowutai Mountain were taken as research objects, through combining field investigation and sampling and litter dehydration test which was more in line with the actual situation, the restoration characteristics of litter water holding capacity of different forests were comprehensively studied. The results showed that:(1) The water-holding capacity of litter layer gradually recovered with time. When the water loss test was carried out for 8 hours, the water holding capacity of the non-decomposed litter layer of all stands was restored to over 80%, and the water holding capacity of the litter in the semi-decomposed layer of the rest stands except pure forest of Betula was restored to over 60%. After 12 hours, the recovery trend of water-holding capacity of litter in each layer was gradually slow. (2) The laws of the non-decomposed, semi-decomposition litter layer water evaporation, infiltration and water holding process of seven typical stands were the same. The amount of evaporation and infiltration was larger in the early stage, and gradually decreased with the decrease of the amount of released water in the later stage. After fitting, the evaporation and infiltration amount were in logarithmic function relation with time, while the evaporation and infiltration rate were in power function relation with time.(3) Litter regulation and water storage effect of typical stands in Xiaowutai Mountain was generally characterized by the faster water retention and slower water evaporation and infiltration after water retention. Through cluster analysis, seven typical stands could be divided into three types of functional groups for regulating and storing water. In the future, functional groups should be taken into account in the tree species allocation of water source forests in this area or other similar habitats, which could realize the best ecological and hydrological functions of litter.

Abstract:The detritus input and removal treatments (DIRT), as an experimental design to study the effects of carbon input on soil texture and quality, plays a key role in the study of soil nutrient sources and main influencing mechanisms. In this study, the natural Castanopsis carlessii forest in the Sanming forest ecosystem and global change research station in Fujian province was selected, and five treatments were set up, including control (CT), no litter (NL), no roots (NR), no input (NI), double litter (DL), 0-10 and 10-20 cm soil samples in each treatment were collected in december 2018 to study the soil organic carbon fractions and their influencing factors. The results showed that:(1) In the 0-10 cm soil layer, the contents of NH₄⁺-N and total N (TN) in DL treatment were significantly higher than those in other treatments. The contents of NH₄⁺-N and dissolved organic N (DON) in NR treatment were significantly greater than those in NL and NI treatment. In the 10-20 cm soil layer, the contents of NH₄⁺-N, NO₃^--N, DON and TN in the DL treatment were significantly greater than those in other treatments. The contents of NH₄⁺-N in NI treatment was significantly lower than that in other treatments. (2) The contents of organic carbon in DL treatment was significantly higher than that in NL treatment, but there was no significant difference in soil organic carbon content between DL treatment and CT treatment (P>0.05), and there was no significant difference among other treatments. (3) The contents of active carbon fraction in the treatment with litter was significantly higher than that in the treatment without litter, and the order of active carbon fraction content was DL > CT > NR > NL > NI. The content of soil recalcitrant carbon in litter removal treatment (NL) was significantly higher than that in root removal treatments (NL and NI). (4) Litter and root input had significant effects on the activities of β-glucosidase and cellobiohydrolase in 0-10 cm soil layer, showing the same changing trend as soil active carbon. Redundancy analysis showed that the variation of soil organic carbon fractions was mainly controlled by β-glucosidase activity. The pH value and soil moisture content were also key factors affected soil organic carbon and its fractions. Litter input was conducive to improve the availability of soil nutrients and soil quality, and accelerate the carbon cycle, while plant roots played a key role in the stability of organic carbon in the soil.

Abstract:Soil carbon plays an important role in maintaining the productivity and yield stability of crops and regulating global climate change. The changes in soil carbon were affected by lots of factors, such as climate, environment and agricultural management measures. In order to study the effects of long-term conservational tillage measures on soil carbon pool and stability, we collected soils (0-200 cm depths) in farmland after 16 years of traditional tillage (T), traditional tillage + straw (TS), no tillage (NT) and no tillage + straw (NTS) treatments in maize (Zea mays L.) - wheat (Triticum aestivum L.) - common vetch (vicia sativa L.) rotation system on the Loess Plateau, China. We analyzed the changes in soil organic carbon (SOC), total carbon (TC), readily oxidized organic carbon (AOC) Content and soil carbon pool index (CPI), carbon pool management index (CPMI), and soil carbon pool activity index (AI). We found that 16 years of conservational tillage measures increased soil OC and AOC Content in the 0-5 cm soil depth, but had no effects at 5-200 cm depth. When compared with T treatment, TS, NT and NTS increased soil OC contents by 59.74%, 58.43% and 80.56%, respectively, and increased AOC contents by 49.80%, 49.56%, 53.17%, respectively. The effects of conservational tillage measures on soil carbon stability varied with soil depths, for example, the CPI was significantly higher in 0-10 cm soil depth than that in 10-20 cm soil depth; while the higher AI and CPMI were found in 10-20 cm soil depth. In addition, the AOC and CPI, AI, CPMI were significantly correlated, implying the changes in AOC contents were the main reason for the changes in soil carbon pool stability. The results from this study suggested that no tillage + straw was an effective measure to improve surface soil carbon pool and the stability in farmland.

Abstract:This study conducted a field plot experiment, including four nitrogen application levels:N0 (no nitrogen fertilizer), N1 (90 kg/hm² of nitrogen fertilizer in both early and late rice), N2 (120 kg/hm² of nitrogen fertilizer in early rice, 135 kg/hm² in late rice) and N3 (150 kg/hm² of nitrogen fertilizer in early rice, 180 kg/hm² of nitrogen fertilizer in late rice), to study the nitrogen absorption and the loss of nitrogen in various ways of double-cropping rice for two consecutive years in 2017-2018. The annual nitrogen surplus was calculated to preliminarily reveal the characteristics of nitrogen budget in double cropping rice fields. The results showed that on the nitrogen absorption, rice yield increased significantly with the increase of nitrogen application. Yield of N2 and N3 were significantly higher than that of N1, while N3 was higher than N2 without significant difference. The grain yield of double cropping rice was 8 869.6~11 002.1 kg/hm², straw yield was 8 666.2~10 744.2 kg/hm². Nitrogen accumulation in rice also increased significantly with nitrogen application. The average nitrogen uptake of single cropping rice was 70.6~112.5 kg/hm², and 140.88~226.5 kg/hm² in double cropping rice. The average nitrogen uptake efficiency was 25.6%~28.7%, 6.5~8.3 kg/kg in agronomic, 23.8~27.0 kg/kg in physiological, and 33.5~56.1 kg/kg in partial productivity. The nitrogen uptake efficiency of N2 treatment was highest. The nitrogen loss of N3 treatment was the highest, and N2 was slightly higher than N1, but the difference was not significant. As for the nitrogen loss, the annual ammonia volatilization loss of each treatment was 20.04~111.97 kg/hm² and the loss rate was 22.33%~26.68%. The N₂O emission loss was 1.38~3.15 kg/hm² and the loss rate was 0.49%~0.86%, the nitrogen leaching loss was 5.10~40.97 kg/hm² and the loss rate was 8.63%~10.87%, the nitrogen runoff loss was 3.78~12.98 kg/hm² and the loss rate was 1.67%~3.38%, the single annual soil inorganic nitrogen residue was -5.70~41.53 kg/hm², and the total nitrogen residue was -15.18~53.02 kg/hm². As for the nitrogen budget, the nitrogen surplus in each treatment was increased with the increase of nitrogen application. The nitrogen surplus of N3 treatment was the highest, N2 was slightly higher than N1. The nitrogen surplus was 13.05~32.20 kg/hm² in the nitrogen treatment in 2017, and 29.18~39.90 kg/hm² in 2018, showing an upward trend in the annual nitrogen surplus. It showed that fertilization was the most important source of nitrogen in double cropping rice field nitrogen cycle, the nitrogen output was dominated by crop absorption, ammonia volatilization and nitrogen leaching loss were also important nitrogen output pathways. The N2 treatment was an appropriate nitrogen application, that is to reduce nitrogen by 20%~25% than the farmers conventional application amount which could not only ensure the nitrogen absorption and use efficiency of double cropping rice, but also reduce the nitrogen loss and surplus.

Abstract:Field experiments were conducted to study the effects of different drip irrigation lateral layout on the root growth of machine-harvested cotton, water and nitrogen transport, and nitrogen use efficiency. Three drip irrigation capillary configuration methods were set up:(1) Embedded drip irrigation lateral + center layout (EB), (2) embedded drip irrigation lateral + side layout (ES), (3) labyrinth drip irrigation lateral + side layout (LS). The amount of nitrogen (N) applied was 300 kg/hm². At the same time, the ES treatment without nitrogen fertilizer was used as the control (CK). The results showed that after 24 hours of drip irrigation, soil moisture and nitrate nitrogen were mainly distributed in the 0-40 cm deep soil layer. The contents of water and nitrate nitrogen in the root zone below the crop row were high in LS and EB treatments, while the nitrate nitrogen in ES treatment moved to wide rows. More than 90% of cotton roots were distributed in the 0-30 cm soil layer, but the roots of the EB treatment were shallower, and more than 80% of the roots were distributed in the soil layer within 15 cm. Compared with the LS and EB treatments, the dry root matter quality of the ES treatment was significantly reduced by 31.7% and 25.5% respectively. The root length density, root surface area, root volume of ES treatment were significantly higher than those of LS and EB treatments. The LS treatment significantly increased the yield and nitrogen use efficiency, which were 9.4% and 18.0% higher than those of the ES treatment. The yield and nitrogen use efficiency of the EB treatment also increased by 6.5% and 8.5% respectively compared with the ES treatment. Machine-harvested cotton should be planted with the labyrinth drip irrigation lateral and side layout. Then the distribution of water and nitrate nitrogen would match the root system distribution better, which could significantly promote cotton root growth, increase nitrogen uptake, and increase yield and water and nitrogen use efficiency.

Abstract:Excessive nitrogen application has been a major problem in corn production, and combined application of nitrogen fertilizer synergist can be used as an important technical measure to achieve high and stable corn yield under the condition of nitrogen reduction. In 2016 and 2017, field experiments were set up in Xinjian Village, Hexing Township, Zhongjiang County, Deyang City, Sichuan Province, to study the effects of different nitrogen application rates and nitrogen fertilizer synergists on soil available nitrogen content and dry matter accumulation and yield of corn, so as to provide scientific basis for reducing nitrogen and increasing yield cultivation techniques of corn. The results showed that the nitrogen reduction combined with synergist could enhance the supply capacity of available nitrogen in soil, promote the accumulation dry matter of corn, improve the yield composition, increase corn yield, and achieve nitrogen reduction without yield reduction. The yield increase ranges of the conventional nitrogen treatment and 20% nitrogen reduction combined with synergist treatment were 5.53%~13.97% and 10.24%~17.05%, respectively. The yield increasing effect of nitrogen reduction combined with synergist was better. Under the condition of reducing nitrogen by 20%, compared with A₂B₂ treatment and A₂B₃ treatment, urease activity and soil nitrate nitrogen content of the A₂B₄ treatment decreased by 19.00%, 15.65% and -2.97%, 57.24%, respectively, and the soil ammonium nitrogen content and yield increased by 11.48%, 248.50% and 3.71%, 6.18% on average in the two years. In summary, under the condition of reducing nitrogen by 20%, the combination of nitrification inhibitor (DCD) and urease inhibitor (HQ) had the strongest supply capacity of soil available nitrogen, which could reduce nitrogen application without reducing corn yield.

Abstract:In order to make rational use of ammonium sulfate, we investigated the effects of 3, 4-dimethylpyrazole phosphate (DMPP) combined with ammonium sulfate on nitrogen conversion and N₂O and CO₂ emission in calcareous cinnamon soil. In this study, we analyzed the effects of ammonium sulfate and nitrification inhibitors (DMPP) on ammonium nitrogen (NH₄⁺-N) content, nitrate nitrogen (NO₃^--N) content, N₂O and CO₂ emission flux and cumulutive emission in calcareous cinnamon soil by laboratory culture experiments. The correlation analysis of correlative indexes was also carried out. The results showed that ammonium sulfate was highly nitrated in the first 15 days of culture. At the 15th day, the content of NH₄⁺-N in soil decreased by 477.28 mg/kg, and the content of NO₃^--N increased by 177.03 mg/kg. Addition of DMPP could significantly inhibit the transformation of NH₄⁺-N of ammonium sulfate to NO₃-N. After 30 days of culture, soil NO₃^--N content of 0.75%~1.75% DMPP treatment decreased by 174.02~177.00 mg/kg compared with that of ASN treatment. The nitrification inhibition rate was 94.92%~95.30%, and there was no significant dose effect in the range of 0.75%~1.75% concentration. Each does of DMPP showed better nitrification inhibition effect during the test period, and the duration of action was more than 30 days. When cultured for 30 days, compared with the CKⅡ treatment, the cumulative emissions of N₂O and CO₂ treated with ammonium sulfate alone significantly increased by 975.3% and 126.66%, respectively (P<0.05), while the cumulative emissions of N₂O and CO₂ treated with DMPP significantly decreased by 76.8% and 6.22%, respectively, compared with that treated with ammonium sulfate alone (P<0.05). Correlation analysis showed that there was a positive correlation between CO₂ emission flux and N₂O emission flux,and a negative correlation between soil pH and N₂O and CO₂ emission flux. In calcareous cinnamon soil, ammonium sulfate combined with 0.75% DMPP could inhibit soil acidification to a certain extent, and at the same time could significantly reduce the cumulative emissions of N₂O and CO₂ (P<0.05).

Abstract:The application of activated water treatment technologies such as magnetization and de-electronic in agricultural irrigation has been widely concerned. In order to clarify the influence mechanism of magnetization-de-electronic water infiltration on soil water and salt transport, one-dimensional vertical infiltration test was conducted with tap water, magnetized water (0.4 T), de-electronic water and magnetization-de-electronic integral activation water, and the effect of magnetization-de-electronic integrated activation water on soil water and salt transport characteristics and salt leaching efficiency were studied. The results showed that compared with the control, the magnetization-de-electronic integrated activation treatment could effectively promote soil moisture infiltration, increase soil water content, reduce soil salinity, and improve the salt leaching efficiency of irrigation water. Moreover, the magnetization-de-electronic integrated activation water had different degrees of improvement in the infiltration capacity, soil water content, soil salinity, and salt leaching efficiency compared with the single magnetization or de-electronic method. Compared with de-electronic water, in the treatment of magnetization-de-electronic integrated activation water, the cumulative infiltration of increased by 28.0%, the time to reach the end of infiltration decreased by 25.7%, the soil moisture content of the 15 cm depth layer increased by 7.9%, and the overall soil desalination rate increased by 13.9%. Compared with magnetized water, in the treatment of magnetization-de-electronic integrated activation water, the cumulative infiltration increased by 6.7%, the time to reach the end of infiltration decreased by 12.2%, the soil moisture content of the 15 cm depth soil layer increased by 3.2%, and the overall soil desalination rate increased by 4.7%. The study results showed that magnetization-de-electronic integral activation water had a significant promotion effect on soil salt leaching, and its promotion effect was more obvious than that of magnetized water or de-electronic water, which was beneficial to create a good water and salt environment for crop growth, and provided a reference for the rational utilization of magnetization-de-electronic integral activation water.

Abstract:In order to compare the effects of mulch and soil covered drip irrigation on the growth of maize, three irrigation levels of high, medium and low were carried out to analyze the growth index, root distribution, water consumption and yield of maize. The results showed that the average leaf area index of mulched drip irrigation was 13%~20% higher than that of soil covered drip irrigation. The root of mulched drip irrigation evenly distributed in the top 30 cm soil layer. The root of soil covered drip irrigation was 10 cm deeper than that of mulched drip irrigation. The total water consumption of mulched drip irrigation was 9% lower than that of soil covered drip irrigation, which was obvious for water saving. The yield of mulched drip irrigation was 7%~15% higher than that of soil covered drip irrigation in the normal and dry year. The yield of mulched drip irrigation was 6%~19% lower than that of soil covered drip irrigation in the normal and wet year (p < 0.05). Medium irrigation treatment with the highest yield and water productivity was the best irrigation scheduling. For different study areas, the annual average precipitation and the annual precipitation forecast were used to calculate the precipitation in the growing period. When annual precipitation was less than 268.32 mm, it was better to use mulched drip irrigation with 186.1 mm of irrigation quota and 7 times; while soil covered drip irrigation for more than 268.32 mm with 228.0 mm of irrigation quota and 8 times. The results could provide a theoretical basis for high-efficiency irrigation of drip irrigation of maize in the study area and similar areas.

Abstract:The objective of this study was to determine the effect of freezing irrigation with saline water of different salinity on soil water infiltration and salt transport in severely saline-alkali soil. In order to compare and analyze the soil water infiltration characteristics and desalination effect, this study adopted an indoor simulation test of soil column made of organic glass. Six treatments with 3 different water quality (distilled water, 3 g/L brackish water, 10 g/L saline water) and 2 different methods (freezing irrigation, direct irrigation) were set up. The results showed that:(1) The initial infiltration rate of freezing irrigation was 8.2, 4.6 and 5.8 times higher than those of direct irrigation under three irrigation water quality. Under the freezing irrigation mode, the higher salinity of irrigation water, the faster soil infiltration rate. (2) Kostiakov model was suitable for fitting the soil water infiltration process under different saline water under freezing irrigation. Horton model is suitable for fitting the soil water infiltration process under direct irrigation. (3) The soil moisture contents in 0-60 cm soil layer of direct irrigation increased by 1.4%~6.3%, 1.6%~3.6%, 0.9%~7.6% respectively compared with those of freezing irrigation under the three irrigation water quality. (4) The desalination effect of 0-30 cm soil layer was more significant under each treatment, the salt was moved to 60 cm soil layer continuously, and the desalination rate of each treatment decreased gradually. In 0-30 cm soil, the desalination rate of fresh water under direct irrigation was the highest, which was 93%~97%, followed by 3 g/L of freezing irrigation, which was 87%~91%. In 50-60 cm soil, the desalination rate of fresh water under freezing irrigation was the highest, which was 13.3%, followed by 3 g/L brackish water freezing irrigation, which was 9.1%. Comprehensive consideration, salint water of 3 g/L with freezing irrigation could improve soil water infiltration rate, effectively reduce soil salt content in 0-60 cm.

Abstract:In order to explore the water-fertilizer management strategy suitable for maize growth in the Hetao Irrigation District, Inner Mongolia, this study conducted a field experiment with different irrigation and fertilization levels. After the calibration and validationby observed data, the AquaCrop model was used to simulate the variation pattern of corn yield and water use efficiency (WUE) under different irrigation and fertilization levels. The results indicated:(1) The R² values of simulated and measured canopy coverage and biomass were 0.74~0.99 and 0.87~0.99, respectively, during model calibration and validation. The NRMSE values ranged from 4.55% to 12.32% and 5.77% to 27.07%, respectively, while the E_NS ranged from 0.90 to 0.99 and 0.85 to 0.99 respectively. The R² values between the simulated and measured output values were 0.99 and 0.97, respectively, and NRMSE were 4.59% and 3.42%, and E_NS were 0.95 and 0.97, respectively. The R² between the simulated and measured WUE were 0.81 and 0.86, respectively, and NRMSE were 6.75% and 13.85%, and E_NS were 0.96 and 0.83, respectively, indicating that AquaCrop model had a good applicability in the Hetao Irrigation District. (2) The verified model was used to simulate the effects of irrigation changes on maize yield and WUE at different fertilization levels. The results showed that when irrigation rate reached 270 mm and continued to increase, the maize yield and WUE remained basically unchanged or even decreased. (3) With stable yield and high efficiency as the target, under the medium fertilization, the optimal corn yield and WUE were given at 270 mm of irrigation. Therefore, we recommend 270 mm irrigation, 375 kg/hm² fertilizing as the best combination to ensure the stable-yield and high-efficiency in the studied area.

Abstract:In order to explore the effects of different irrigation methods on soil structure and nutrients in kiwifruit orchard, two treatments of surface irrigation and micro-sprinkler irrigation were applied in the kiwifruit orchard of Yangling, Shaanxi Province from 2017 to 2019. The structure of soil aggregates and the contents of organic matter, available nitrogen, available phosphorus and available potassium in 0-50 cm soil layer were determined. The results showed that in 0-50 cm soil layer, the distribution uniformities of the soil particles size of >5.0, 2.0~5.0, 1.0~2.0, 0.5~1.0, 0.25~0.5, <0.25 mm in different soil layers under surface irrigation were higher than those under micro-sprinkler irrigation, and the grain of <0.25 mm was the most uniform in the two irrigation methods. The content of water-stable aggregates (> 0.25 mm) in soil under micro-irrigation was significantly higher than that under surface irrigation. The mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates under micro-sprinkler irrigation were higher than those under surface irrigation, while the fractal dimension (D) was lower than that under surface irrigation. The total contents of N, P and K in soil under micro-sprinkler were higher than those under surface irrigation. Micro-sprinkler irrigation could maintain the stability of soil structure and soil fertility, and promote the sustainable development of soil. It is a suitable irrigation method for mature kiwifruit orchard.

Abstract:In order to clarify the effect of layered fertilization on winter wheat yield, water consumption characteristics and water use efficiency under different irrigation conditions, and provide a theoretical basis for high-yield and high efficiency of wheat production practices in Huanghuaihai region, the split plot experiment with two factors of water and fertilizer was adopted combined with the local winter wheat irrigation system. In the experiment, water was taken as the main area, and the fertilization method was taken as the sub-area. Three irrigation treatments were set up, including no irrigation in spring (W₀), irrigation in spring jointing period (W₁), and spring jointing period irrigation + flowering stage irrigation (W₂), the irrigation amount was 90mm/time. Two fertilization treatments were conventional fertilization treatment (F₁) and layered fertilization treatment (F₂). The characteristics of winter wheat yield, water consumption and the water use efficiency under different irrigation and fertilization modes were analyzed. The results showed that compared with F₁treatment, soil water consumption, water consumption intensity of winter wheat jointing to anthesis stage and farmland water consumption of 40-120 cm soil layer in F₂ treatment increased significantly, and farmland water consumption in W₂F₂ treatment was the highest. Compared with conventional fertilization, the water use efficiency of winter wheat in layered fertilization treatment increased by 14.2%~3.0%, the water use efficiency of W₁F₂ treatment was the highest. Under the three irrigation conditions, compared with conventional fertilization, the number of ears per unit area, of winter wheat was significantly increased in the layered fertilization treatment, and the yield increased by 19.8%~6.4%, of which W₂F₂ treatment had the highest yield. Therefore, it was recommended that in areas with sufficient water, the management method of irrigation at spring jointing period and flowering stage combined with layered application of base fertilizer should be adopt, while in water shortage areas, the management method of spring irrigation at jointing stage combined with layered application of base fertilizer should be adopt.

Abstract:In order to reveal the effect of long-term organic fertilization on soil fertility of irrigated desert soil, based on the long-term fertilization experiment of irrigated desert soil in Hexi oasis irrigation area of Gansu province (1988 to present), four treatments including organic phosphate fertilizer (MP), organic and inorganic NPK (1/2 MN + P), nitrogen and phosphorus (NP) and no fertilizer (CK) were designed. Based on the existing test data of soil nutrient and crop yield and those data measured in the 31st year, the effects of long-term organic fertilization on soil fertility and crop yield in desert soil were studied. The results showed that compared with the initial value of the experiment, the average soil nutrient value of the past years and that in the 31st year of organic-inorganic combined application all increased, which indicted that the soil organic matter increased by 72.5% and 24.9%, soil total nitrogen increased by 72.3% and 25.7%, and soil total potassium increased by 16.1% and 33.0%. Compared with non-fertilizer control (CK), soil organic matter increased by 54.9% and 19.1%, soil total nitrogen increased by 47.3% and 14.9%, and soil total phosphorus increased by 73.0% and 15.3%. Combined application of organic and inorganic fertilizer could effectively reduce soil pH. Compared with CK, the average value of the past years and that in the 31st year of organic-inorganic combined application showed that the yield of wheat/maize intercropping system increased by 149.2% and 139.2%, fertilizer contribution rate (FCR) was 0.58, coefficient of variation (CV) was 0.21, and sustainability index (SYI) was 0.61. Nutrient and yield indexes all reached high quality level. In Hexi oasis irrigation area, Gansu province, long-term combined application of organic and inorganic could continuously and significantly increase the contents of soil organic matter, total nitrogen, total phosphorus, total potassium, alkali-hydrolyzed nitrogen, available phosphorus and available potassium, reduce soil pH and increase soil fertility and the contribution rate of fertilizer. It could significantly improve the yield, stability and sustainability of wheat/maize intercropping system. This study could provide decision-making basis for scientific fertilization of farmland soil and sustainable development of agriculture in Hexi Oasis Irrigation Area of Gansu Province.

Abstract:The aim of this study was exploring the effects of plastic film mulching and application of water retaining agent combined with microbial fertilizer on quantity of soil microorganism, enzyme activity, and yield and water use efficiency of seed maize in Hexi Corridor. In oasis irrigation area of the Hexi Corridor, six treatments were set up, which were single plastic film mulching (AF), single application of super absorbent polymer (AW), single application of microbial fertilizer (AB), application of super absorbent polymer combined with microbial fertilizer (WB), plastic film mulching combined with microbial fertilizer (FB) and neither super absorbent polymer nor microbial fertilizer in open field (CK). The dynamic changes of soil microbial quantity, enzyme activity in 0-20 and 20-40 cm soil layer before sowing and after harvesting, and the yield of seed maize were analyzed. The results showed that:(1) Single or combined application of microbial fertilizer both could improve the activity of soil catalase, urease, invertase, phosphatase, and increase the number of fungi, bacteria and actinomycetes, and the content of soil microbial carbon and nitrogen, and improve the soil microbial environment. Among them, the effect of super absorbent polymer combined with microbial fertilizer was the best, and followed by the treatment of FB. (2) The treatment of AB had little influence on the growth of seed maize, but the treatment of FB could significantly increase the leaf area index and dry matter accumulation of seed maize, and could adjust the yield composition factors. (3) Different drought resistance measures and the combined application of microbial bacterial fertilizers could promote yield formation of seed maize. Among the different treatments, the grain yield of the FB treatment was the highest (10 105.64 kg/hm²), followed by the treatment of AF (8 967.24 kg/hm²) and WB (8 323.93 kg/hm²), and the production increased by 61.99%, 43.74% and 33.43% compared with CK, respectively. (4) The water use efficiency was the highest in the treatment of FB (2.40 kg/m³), followed by AF (2.15 kg/m³) and WB (1.89 kg/m³), and the water use efficiency significantly improved by 80.10%, 61.84% and 41.80% compared with CK, respectively. Therefore, comprehensive considering the yield, water production efficiency and soil microenvironment, the best combination of drought resistant measures combined with microbial fertilizer was plastic film mulching combined with microbial fertilizer, which could not only promote the growth and development of seed maize, but also improve irrigation water use efficiency and water use efficiency, meanwhile improve the soil micro-environment of the tillage layer, which was of great significance to the sustainable development of seed maize production in the Hexi Corridor.

Abstract:Alpine grassland desertification is a serious threat to the ecological security of the Tibetan Plateau. Studying the variations in soil carbon, nitrogen and microorganisms during desertification processes is helpful to reveal the biological mechanism driving the desertification of alpine grassland. In this study, the variations of soil carbon and nitrogen, enzyme activity, and bacterial community diversity under the conditions of non-desertification, light desertification, medium desertification and heavy desertification were analyzed. The results showed that the medium and heavy desertification decreased soil organic carbon, dissolved organic carbon, microbial biomass carbon, total nitrogen, soluble total nitrogen, soluble organic nitrogen, microbial biomass nitrogen, nitrate nitrogen and ammonium nitrogen; while light desertification had no significant impacts on soil organic carbon, microbial biomass nitrogen, nitrate nitrogen and ammonium nitrogen. The β-D-Glucosidase, Sucrase, Chitinase, Urease and Peroxidase activities decreased with the increasing desertification, and the most drastic decline occurred at the stage from light to medium desertification. Soil bacterial diversity increased under light desertification, and then decreased under medium and heavy desertification, but there was no significant difference in soil bacterial community structure under different degrees of desertification. RDA showed that there was a significant positive correlation between soil enzyme activity and bacterial diversity. PCA showed that soil organic carbon, microbial biomass nitrogen, peroxidase, and chitinase had great impact on dominant bacteria species. Therefore, the protection measures taken at the light desertification stage could effectively prevent soil attributes from becoming a more severe condition in alpine grassland, in addition, the role of key bacterial communities also should be concerned during the restore process of desertificated soil.

Abstract:Based on the daily scale precipitation data of 140 meteorological stations from 1961 to 2019, monthly scale Land Surface Temperature (LST) and Normalized Difference Vegetation Index (NDVI) from 2000 to 2016, the Huaihe River Basin was taken as the research area. The meteorological drought was characterized by Standardized Precipitation Index (SPI), the typical dry years were determined, according to the SPI. And the agricultural drought was characterized by Temperature Vegetation Drought Index (TVDI). Landsat 8 data was used to extract winter wheat planting area in the Huaihe River Basin, and the further in-depth analysis was made on the correlation and influence between the underlying surface hazard-formative environmental conditions, such as elevation, slope, river, soil type, soil relative humidity and shallow groundwater depth, and winter wheat drought, to provide theoretical basis and technical support for the study of winter wheat drought disaster prevention and mitigation. The results showed that:(1) From 1961 to 2019, the precipitation changing trend in different growth periods of winter wheat was not obvious, and the precipitation in pre-winter growth period and filling and mature period showed a slightly rising trend. The upward and downward trends of all meteorological stations were not significant. According to SPI, the typical dry year in the pre-winter growth period was 2010, the over-wintering period was 2011, the regreening and heading period was 2006, and the filling and mature period was 2001. (2) By comparing the proportion of meteorological drought and agricultural drought above mild drought and the spatial distribution, the degree of agricultural drought in the Huaihe River Basin was generally greater than the meteorological drought, and their spatial distributions were consistent overall, but there were some regional inconsistencies. It was necessary to further analyze the impact of underlying surface hazard-formative environment on agricultural drought. (3) Winter wheat drought was highly correlated with river, surface soil relative humidity and shallow groundwater depth, but less correlated with elevation, slope and soil type. Winter wheat agricultural drought in the Huaihe River Basin was prone to occur in areas with relatively high elevation, steep slope, semi - hydrogenous soil type, distances from rivers, low surface soil relative humidity and shallow groundwater burial depth of more than 1 m. The degree of drought increased from coastal to inland and was higher in the south and lower in the north, so it was necessary to strengthen disaster prevention and drought resistance in such areas and increase artificial irrigation facilities.

Abstract:In order to explore the variation characteristics and influencing factors of penetration resistance of different soil types, taking six typical soils in Huang Huai Hai dry farming area and northeast dry farming area, including fluvo-aquic soil, cinnamon soil, black soil, chernozem soil, lime concretion black soils and brown soil, as research objects, 0-40 cm penetration resistance was measured, and its vertical distribution characteristics was analyzed. The quantitative relationship between penetration resistance and soil physical and chemical properties (water content, bulk density, texture and organic matter content) within 0-20 cm soil layer was analyzed. The thickness of the plough layer of different soil types was determined based on trend analysis. The results showed that:(1) In the 0-40 cm soil layer, the penetration resistance increased first and then kept stable with the increasing of soil depth. The lowest average penetration resistance was 1.188 MPa for chernozem and 0.819 MPa for ordinary dark aquic soil, respectively, while the highest was 1.706 MPa for cinnamon soil and 1.829 MPa for loamy calcareous alluvial soil, respectively. (2) In the range of 0-20 cm, for different soil types, different modeling methods had different effects. Partial least squares regression was suitable for fluvo-aquic soil, black soil and brown soil, and multivariate linearity was better for cinnamon soil and sand ginger black soil. The random forest regression was suitable for chernozem. The empirical formula developed in this study helps to clarify the changing factors of penetration resistance. (3) Mann-Kendall method and Pettitt method could objectively determine and examine the thickness of the plough layer. The plough layer thickness of typical soils in dry farming areas was 22.5 cm for cinnamon soil, 21.5 cm for fluvo-aquic soil, 20.0 cm for brown soil, 16.0 cm for black Calcium soil, 15.0 cm for sand ginger black soil and 14.0 cm for black soil. In cinnamon soil, fluvo-aquic soil and brown soil area, deep ploughing was suitable, and crops with developed root systems could be cultivated. Chernozem soil, sandy black soil and black soil area needed more protection, and the application of large-scale agricultural machinery should be reduced.

Abstract:Chemical enhancement can improve the heavy metal phytoextraction efficiency of hyperaccumulator from soil. A pot experiment was conducted to study the effects of different dosage and combinations of biodegradable chelating agents L-glutamic acid N, N-diacetic acid (GLDA) and liquid fertilizer on the absorption of Cd and Zn by hyperaccumulator Sedum alfredi, and evaluate the environmental risk of their leachate. The results showed that the single use of GLDA or liquid fertilizer both increased the extraction efficiency of Cd and Zn of Sedum alfredii. The phytoextraction of Cd and Zn in the treatment with 1.25 mmol/kg GLDA was 1.36 and 1.46 times as much as that of the control, respectively, and the treatment with 0.5 g/kg liquid fertilizer also increased phytoextraction of Cd and Zn by 1.40 and 1.43 times, respectively. The treatment with low dose of GLDA or liquid fertilizer resulted in highest Cd phytoextraction efficiency, which reached 41% to 42%. The concentration of heavy metal in the corresponding leachates of these two treatments were also lower than that of the control, indicating lower environmental risk. When the high dose of liquid fertilizer (2 g/kg) was combined with GLDA, the phytoextraction of Cd and Zn by S. alfredii was lower than that of the control. These results indicated that GLDA and liquid fertilizer had potential to enhance phytoremediation of S. alfredii, and it was better to use these two reagents separately and in low dosage. These preliminary conclusion needs further verification with field experiments.