Abstract:Cultivated land in Southwest Karst Area is characterized by a special double space structure with surface and underground, which cause particularity and complexity in soil erosion process in those areas, and produce a series of special environmental geological problems, such as soil erosion, drought, and desertification. This paper aimed on process and the driving forces of soil loss or leakage on karst slope land, which could provide theoretical basis and technical support for the comprehensive controlling and ecological restoration of rocky desertification. Meanwhile, this paper had summarized the latest research progress on surface erosion and underground leakage loss mechanism in the karst slope of Southwest in China. So far, the process and mechanism of surface erosion have conducted qualitative, whereas the studies of underground leakage loss were in qualitative description and indoor simulation exploration stage. Simulations and field observations on karst slope land showed that soil erosion type on karst slope farmland was a process of transition from underground leakage to surface erosion. That was, the soil loss type was dominated by underground leakage when small rainfall occured, and the surface erosion and underground leakage loss was equal even the surface erosion was higher than the underground soil loss at heavy or storm rain conditions. Alternatively, analyzed deeply the research and development of soil and water loss control in Karst areas, and pointed out the future development of soil and water loss.

Abstract:For developed eluvial horizon (A), illuvial horizon (B), transition horizon (BC) and the parent material horizon (C) of granite collapsing gullies region in Tongcheng, Hubei province, the impact of slope and flow on soil anti–scouribility and related soil physical properties were explored. Specifically, the slope were 8.8％, 17.6％, 26.8％, 36.4％, and 46.6％, and the flow were 0.2 L/s, and 1.0 L/s, respectively. The results showed that physical and chemical properties were ⑴ significant different among layer A, layer B, layer BC, and layer C of granite collapsing gully soil. ⑵ When the flow was constant, index of soil anti-scourability showed a decreasing trend, with the increase of the slope; when the slope was constant, the index under high flow conditions was low; at the same slope and flow conditions, the index decreased from layer A to layer C, indicating that layer A has the best anti-scourability, while layer C has the worst. ⑶ The soil anti-scourability index of all layer decreased linearly with the increase of the slope (p<0.05), and the erosion resistance of soil decreased with the increase of the slope. The absolute values of the coefficients of regression equation in layer A were the largest and the constant was also the largest. This shows that theanti-scourability of layer Achanges sharply with the slope, the erosion resistance of layer A is the strongest and the soil loss is the least. ⑷ There was a positive correlation between soil anti-scourability index and the content of silt, clay content, water stability index and permeability coefficient, and negative correlation with soil dry density and sand content. The correlation between dry density and water stability index was very high, which showed extremely significant correlation. The soil anti-scourability was positively correlated with organic matter content, CEC and free iron Oxide, while negatively correlated with soil pH, specifically, the correlation coefficient with the organic matter content was greater than 0.9, which was extremely significant.

Abstract:The standard runoff plots with hedgerows of gardenia (shrubs) and ryegrass (herbaceous) were set up to study the effects of different hedgerows on soil physicochemical properties and on the characteristics of phosphorus loss in the typical lime soil slope farmland in Xiangxi River Basin of Three Gorges Reservoir area. Results showed that the hedgerows system could effectively increase the fine particles content in soil and reduce bulk density, so as to improve soil fractal characteristics. It could also enhance soil dredging and water content, and finally increase the soil corrosion resistance index Prevention and control soil nutrient loss. The effects of two hedgerows on soil physicochemical properties and phosphorus loss varied in different soil depths and different intercropping zones in the lime soil slope farmland, but the effects were not significant. The contents of Ca8-P, Al-P, Fe-P, O-P and Ca10-P in soil were significantly correlated with soil clay contents (r = 0.772, 0.805, 0.683, 0.682, 0.738). There was a significant negative correlation between soil bulk density and clay contents (r = -0.648), indicating that the hedgerows system could reduce soil bulk density and phosphorus loss through effectively blocking and enriching soil clay particles, to achieve the improvement of soil physicochemical properties and controlling of agricultural non-point source pollution in lime soil slope farmland.

Abstract:By using artificial rainfall simulation system and variable slope soil trough, the runoff and sediment yield responses of red soil slope under heavy rainfall were tested to study the response of artificial red soil slope to heavy rainfall. The rainfall intensities included 140, 160, and 190 mm/h, and the slope degrees included 10 °, 15 °, 20 ° and 25 °. The experimental results showed that the erosion modulus in red soil slope with simple artificial treatment under super rain intensity of 140～190 mm/h was significantly lower than that in slopes without treatment under rain intensity of 50～120 mm/h , and the rill development process was slow. This indicated that soil treatment on slope could effectively improve the soil erosion resistance. Under the same rainfall intensity, the runoff yield time firstly delayed and then shortened with the increasing of slope degree, and the critical gradient of the runoff yield was between 20°and 25°. Under the same rainfall intensity, the erosion modulus firstly increased and then decreased with the increasing of slope degree, and the critical gradient was different under different rainfall intensity. The erosion critical gradient was 15°～20° when the rainfall intensity was 140 mm/h, and it was 20°～25° when the rainfall intensity was 160 mm/h and 190 mm/h. Overall, the erosion process was affected by the rainfall intensity more than the slope degree. The erosion processes of slopes with different slope degrees were relatively stable when the rainfall intensity was 140 mm/h, and the development of rill was weak. The erosion was strengthened when the rainfall was 160 mm/h, but there was not obvious tend in the erosion process. When the rainfall intensity was 190 mm/h, the erosion mainly occurred in the first 30 min of the rainfall, and the development of rill was relatively severe, and it tends to be stable after 30 min.

Abstract:Subsurface flow is an important form of water flow in slope cropland of purple soil area, while rainfall intensity is the key factor to control subsurface flow and soil water content. In order to understand the impact of rainfall intensity on soil water and subsurface flow at different layers of purple soil depth and to discover the correlation between water content and interflow in purple soil area, Minitrase TDR probes were buried into purple soil profile, which included superficial layer (0—20 cm)，middle layer (20—40 cm) and deep layer (40—60 cm), to continuously measure soil moisture content in situ under the conditions of three simulated rainfall intensities (60 mm/h, 90 mm/h and 120 mm/h). During the simulated rainfall process, the precipitation-runoff-producing was observed by collecting different layers’ interflow. The results indicated that: (1) When the simulated rainfall intensity was small, the changes of soil water content in superficial layer showed a trend of from rising to stability. Then along with the increasing rainfall intensity and soil depth, it presented rising, stable or always stable state. (2) As the soil depth and rainfall intensity increased, the response of soil water content to rainfall intensity was not obvious, with an increasing stabilization time and little change in soil water content. (3) The presence of various levels of interflow was observed in all layers under different rainfall intensities. Subsurface flow producing presented an unimodal process under low rainfall intensity conditions, otherwise, it had double peaks. (4) The producing time of interflow declined significantly with higher rainfall intensity, and increased with deeper layers. (5) It could be concluded that rainfall intensity had obvious correlations with soil water content and subsurface flow.

Abstract:In order to investigate the effects of different slope vegetation patterns on energy regulation and the relationships between water and sediment, an indoor scouring experiment was set up. The erosion and sediment yield equation under different slope vegetation patterns was established based on the energy parameter for the in-depth understanding of the response relationships between energy and sediment yield. The results showed that: (1) Compared to the bare slope, the runoff power greatly reduced under slope vegetation cover condition, indicating that vegetation could effectively reduce runoff power and protect the soil. At different times, unit stream power was small in the slope, but rapidly increased when flowing into the trench, showing a "N" shape curve. SPSS analysis showed that effects of slope vegetation patterns on the unit stream power was not significant (P >0.05), and little effect on the change of the runoff energy consumption was observed. At different times, the slope surface runoff energy consumption on each section in different slope vegetation patterns ranged in 1 500~2 000 J, but increased sharply in the channel, up to about 4 800 J. (2) Planting vegetation on the slope of slope gully system could effectively play an important role of water storage and sediment reduction. When the distance between grasses strip to the slop top was 2 m (pattern F), the water storage efficiency was up to 19.07%, and when the distance was 6 m (pattern B), the sediment reduction rate was as high as 69.02%. (3) The cumulative runoff yield and cumulative sediment yield in different slope vegetation patterns showed a functional relationship of M=aQb, and the correlation coefficient a and b could be used as indicators of water storage and sediment reduction efficiency. (4) There was a linear relationship between runoff power and average sediment transport rates in different slope vegetation patterns, the functional form was D=cω+d.

Abstract:Slope gradient is an important factor affecting the surface slope erosion of red soil. The objectives of this study were to investigate the impact of slope gradients on runoff and sediment yield erosion processes. Three rainfall intensities (1.0 mm/min, 1.5 mm/min, 2.0 mm/min) and three slope angles ( 10°, 15°, 20° ) were comparatively studied under simulated rainfall. Results showed that: (1) Under the same rainfall intensity, the time of the initial runoff were shortened with the increasing slope gradients on red soil, slope angle and runoff volume were positively correlated; under the same slope gradient, both the time of initial runoff and runoff volume decreased with the increasing rainfall intensity. (2) The effects of slope gradients on the sediment yieldwere more complicated, an increasing slope gradient generally increased the average sediment yield, which had greater volatility under 15°. (3) The contribution of slope gradients to runoff volume was more than 60%, and to sediment yield was above 30%. These findings provided theoretical basis for erosion prediction and prevention in erosion area of red soil.

Abstract:Based on runoff and sediment yield at plot and small watershed scales by field monitoring of 8 years and 7 years respectively in the black soil region of Northeast China, the characteristics of runoff and sediment yield of the first two rainfall events and those of the rest events were compared, which represented the runoff and sediment yield that was influenced and not influenced by freezing and thawing respectively. Results showed that with the effects of freezing and thawing, the runoff coefficient reduced by 0.07 and 0.03 at plot and small watershed scale respectively. Initial abstraction duration increased by 71.7% at slope scale; while, there was no obvious increase at small watershed scale. Soil loss, soil erodibility and sediment concentration increased significantly at both scales under freezing and thawing, and soil erosion was?more?likely to?occured. When the runoff was small, the sediment amount of the rainfall events with freezing and thawing was smaller than that of the rainfall events without it. Compared to those rainfall events without freezing and thawing, the rainfall events with freezing and thawing led to the runoff reduction. As a result, sediment amount of the rainfall events with freezing and thawing was lower at the same rainfall, while it was higher at the same runoff. Freezing and thawing had a more evident effect on rill development and sediment amount at plot scale when runoff was small, as well as capacity of the loose deposits transportation and sediment amount at small watershed scale when runoff was large. The results provide a scientific basis for the quantitative evaluation and transformation model of soil erosion with freezing and thawing in the black soil region of Northeast China.

Abstract:In order to clarify soil erosion of degraded alpine meadow, the degraded grassland of Henan County in source area of the Yellow River was chosen as research object. Field rainfall simulation experiment in situ was adopted to analyzed the changes of soil runoff and erosion quantity with soil slope, degradation degree, rainfall duration and rainfall intensity under different rainfall conditions. The results showed that: Natural water content and density of degraded meadow soil declined with the slope and the degradation degree（P<0.05）. Under the same conditions, the runoff and sediment yields had negative correlations with vegetation coverage, showing power(y=140.69x-0.4667，R2=0.9882) and exponential functions (y=4294.3e-0.0418x，R2=0.9907) respectively. Both runoff and sediment yields had positive correlations with rainfall intensity, the correlation functions were y=40.35e0.0252x (R2=0.9708) and y=62.657e0.0201x (R2=0.9688) respectively. The plot runoff of 30° slope increased by 3.6 times and 1.7 times respectively than 10° and 20° slope, and sediments also increased by 16 times and 1.4 times respectively. These showed that the runoff and sediment yields increased sharply with the increase of slope. The variations of runoff and sediment concentrations were large under the vegetation coverage of less than 40%. Surface slope runoff began to rise slowly after 30 min of rainfall, and the slope sediment loss mainly concentrated in 5 ~ 15 min after rainfall, and the sediment yield was sharply reduced after 55 ~ 60 min of rainfall. Thus, it could be concluded that rainfall duration of one hour was the sensitive period of soil particle erosion. The confluence scouring of hillslope after natural slope runoff was the important reason of aggravate soil erosion in degraded grassland.

Abstract:In order to reveal the effect of rainfall, topography, land use pattern and other factors on sediment and phosphorus loss in natural small watershed, four small watersheds with different scales (Surong, Jieliu, Daxing, and Wanan) were chosen according to the natural physiognomy and land use characteristics of small agricultural watershed in Hilly Area, and the monitoring areas were 3.0, 34.6, 480.3 and 1 236.4 hm2, respectively. Phosphorus loss characteristics of small watershed were monitored in three rainstorm events and rainfall erosivity (R) of these rainstorms were 1 411.5, 595.7, 391.4 MJ·mm / (hm2·h), respectively. The results showed that： (1) The hydrological responses of Su Rong and Jie Liu, which were mainly residential areas, market towns and cultivated land, were faster, and the runoff peak value of these two watersheds appeared at 5 ～ 10 min after rainfall peak in the rainstorm event, while the sediment concentration peak and runoff peak appeared at 0.5 ～ 3 h behind rainfall peak in Daxing and Wanan. (2) There was a consistent significant correlation between sediment and total phosphorus (TP), particulate phosphorus (PP) (R > 0.6, P < 0.01) in three rainstorm events, the sediment and TP loss loads were the highest in the source small watersheds (Surong and Jieliu), the average TP loss load of Su Rong reached 0.36 kg/hm2, and the loss loads of sediment and TP of Wanan were the lowest, and the average TP loss load was 0.009 kg/hm2. (3) PP accounted for more than 50% of TP loss in the runoff. (4) The results of multivariate regression analysis showed that runoff and sediment contents could be used to predict phosphorus flux. A combination of sloping cropland, forestland and paddy field could significantly reduce the sediment and phosphorus loss load. The results could provide references for calculating the multi - scale loss of phosphorus in the rainstorm process of small agricultural watershed in Hilly area.

Abstract:To explore the responses of soil and water loss to the development of karst fissures, the effects of two different karst fissures structures: fissures exposed rock-soil (XL) and fissures buried rock-soil (XM) on subsurface runoff and nitrogen leaching were studied through rainfall simulation experiments, in which soil experimental micro-plots (QT) were selected as control. The results showed that the responses time of subsurface runoff under different karst fissures structures listed in the order of XL＜XM＜QT, the responses time of subsurface runoff to the rainfall were 29, 77, and 139 min, respectively, and responses time of subsurface runoff of XL and XM reduced by 79.14% and 44.60% compared to QT, respectively. The rainfall thresholds were 20.64, 55.06, and 94.90 mm, respectively, and rainfall threshold of XL and XM reduced by 78.25% and 41.98% compared to QT, respectively. The times of the stability of subsurface runoff rate were 59, 107, and 169 min, and the stability of subsurface runoff rates were 42.09, 42.36, and 38.24 mm/h, respectively. The nitrate nitrogen and nitrogen concentration were the highest in XL, which could reach 11.64, 10.45 mg/L, respectively. The nutrient concentration in subsurface runoff reached a stable value in XL and QT prior to runoff stopped. The total nitrogen amount under different karst fissures structures followed the order of XL＞XM＞QT, nitrate nitrogen leaching listed in the order of XM＞XL＞QT. Under different karst fissures structures, nitrate nitrogen was the main component of nitrogen leaching, which accounted for 82.32%～90.12% in total nitrogen leaching amount, however, the proportion of ammonia nitrogen was less than 2%. The existence of the fissures, especially the existence of the XL, could enhance both the subsurface runoff rate and the leaching of nitrogen for per unit area soil, the soil which at the bottom of the experimental micro-plot. Because of the widely developed fissures in karst area, the infiltration of water was promoted, moreover, the leaching of nitrogen was intensified too. The relevant results can provide scientific basis for explore the mechanisms of soil and water loss as well as construction material migration model in karst regions.

Abstract:In order to provide scientific basis for rational application of pig manure as an organic fertilizer in typical red soil sloping lands, a field runoff micro location test in peanut-grown red soils that developed from three typical parent materials (granite, red sandstone and red clay) was conducted for three consecutive years to monitor the effects of different pig manure amounts on water and soil loss and phosphorus loss in red soils in mid-subtropical region of China. The treatments included six application rates of pig manure (phosphorus content was 0, 0.5, 1, 2, 4 and 8 times that of the control) that combined with half amount of local conventional chemical fertilizers, and the application of conventional chemical fertilizers alone was took as the control. The results showed that runoff and sediment were obviously reduced by the application of pig manure, but the phosphorus content in runoff and sediment increased linearly with the increasing of pig manure application rate, and this suggested a growing environmental risk. Runoff and sediment volume of the three red soils listed in the order of were granite > red sandstone red > red clay red. When the pig manure application rate was 3 500 kg/(hm2·a), runoff and sediment reduced by 28.0% and 6.3%, respectively, in the red soil developed from granite, and the above two parameters reduced by 23.2% and 37.1%, respectively, in the red soil developed from red sandstone. When the pig manure application rate was 7 000 kg/(hm2·a), runoff and sediment reduced by 40.7% and 12.8% respectively in the red soil developed from red clay. When the pig manure application rates were 14 000, 28 000 and 28 000 kg/(hm2·a) for red soils from granite, red sandstone and red clay, respectively, the average total phosphorus content in runoff exceeded the standard value of Environmental Quality Standards for Surface Water of Class V. Total phosphorus content in runoff of the three kinds of red soil listed in the order of granite > red clay > red sandstone, and total phosphorus content in sediment of the three red soils listed in the order of red clay > granite > red sandstone. Under the condition of halving the conventional amount of chemical fertilizer, applying pig manure at the rate of 40 kg P/(hm2·a) for soils developed from granite and red sandstone, and at the rate of 80 kg P/(hm2·a) for the soil developed from red clay, could effectively reduce water and soil loss without increasing the risk of phosphorus loss over 3 years.

Abstract:The slope erosion and sediment yield are mainly affected by the dynamic process of slope runoff. The characteristics of slope runoff process are described by hydraulic parameters. The purpose of this paper was to study the relationships between slope erosion and sediment yield and hydraulics parameters，and to reveal the hydrodynamic mechanism of slope erosion and sediment yield through artificial rainfall simulation. The principles of classical hydraulic calculation and statistical fitting were applied for the comprehensive analysis of runoff and sediment yield process in different rainfall intensities and slope lengths. Five slope lengths (1, 2, 3, 4, 5 m) with 13 rainfall intensities were designed under a specific slope (20°). The conclusions were listed as follows: (1) Within the designed rainfall intensities (0.65～2.0 mm/min) and slope (20°), slope surface runoff were slowly, which was laminar flow under rainfall intensity < 0.7 mm/min, the smallest rainfall intensity of turbulent flow occurrence was 1.01 mm/min. (2) The influence of the slope length on the Froude number and resistance coefficient were larger than on the shear stress, runoff depth and Reynolds number. The slope length of 3 m was the step length of slope runoff fluctuation, and was the shortest slope length designed for a simulated experiment of hydrodynamic parameters. (3) The velocity was the main influence parameter of slope surface erosion and sediment yield, and the shear stress was one of comprehensive indicators for estimating the strength of slope surface erosion and sediment yield. The above results provided a simple and rapid judgment method for predicting the intensity of erosion and sediment yield through runoff and flow velocity in wide field.

Abstract:In order to characterize the soil erosion change in windy desert region of northern Shaanxi Province in the last 26 years, the Chinese Water Erosion on Hillslopes Model was combined with GIS and RS technic to assess the average erosion amount of Jialu River watershed in 3 period years (1988-1996, 1997-2004 and 2005-2013), and analyze temporal and spatial variation characteristics of soil erosion under different vegetation coverage and different land use patterns. The results showed that (1) the Chinese Water Erosion on Hillslopes Model is suitable to predict erosion in the study area; (2) Soil erosion intensity was closely related to the spatial distribution of rainfall erosivity (R), topography and land use patterns; (3) 26 years were divided into three periods, the first period of 1988-1996, the second period of 1997-2004 and the third period of 2005-2013, the corresponding mean annual R factor were 923.09, 1 010.75 and 1 551.40 MJ·mm/(hm2·h). The soil erosion modulus were 4 513, 5 855 and 3 556 t/(km2·a). The total soil loss of the first and third periods respectively were 5.10×106 t and 4.02×106 t, reduced by 21.18%. The land use patterns greatly changed in the watershed after Green for Grain Project. The area of cultivated land decreased from 53.38% to 25.87%, while the grassland increased from 38.64% to 69.64%. The descending order of soil erosion intensity in different land use was unused land, grassland, forestland and cropland, so the benefit of soil and water conservation was the most obvious in unused land and grassland. So Green for Grain Project has already obtained obvious benefit of water and soil conservation.

Abstract:In order to explore the influence of topographic factors on the development of erosion gully, re-grading Digital Elevation Model（DEM） at different levels was conducted in the study area. The erosion gully distribution data were obtained from the results of the Erosion Gully Census in the First National Water Resources Census (2010) and the results of the Erosion Gully Census in the Fifth Soil Erosion Census In Liaoning Province (2015). Erosion gully elevation, slope, slope aspect, slope length and space differentiation were based on the 1:50 000 DEM . This study analyzed the characteristics of erosion gully development and topographic differentiation in Liaoning province of China with the supported of geographic information system (GIS) and remote sensing (RS) technology. The results showed that the erosion gully density increased 0.02 km/km2 in the study area within 5 years, and the erosion gully mainly concentrated in the western Liaoning. The change value of the erosion gully density were less than 50 m/km2 in more than 70% of the study area, most of them were in the micro enhancement zone. The change value of density was maximum when the elevation was between 325 m and 350 m. The change values of density of the south slope and southwest slope were the maximum. When the slope was between 1.5o and 15o, the graph of change density was parabolic, and there was no obvious change when the slope was less than1.5o and more than 15o. The density change was the maximum when the slope length was between 600 m and 800 m, and there was no significant difference in density change when the slope length was more than 1 000 m.

Abstract:As an area with fragile ecological environment and sensitive soil erosion, the study about soil erosion on the Three Gorges Reservoir Area is of great significance to its ecological construction. In this paper, Daning River Basin and Meixi River Basin were selected as the study areas. Based on the Remote Sensing mages in the year of 1988, 2000, 2010 and 2015, and by using GIS and RS technique combined with field survey, the data about soil erosion were extracted and the spatial variability of soil erosion evolution in different elevations and slope belts were analyzed through the comprehensive index of soil erosion intensity and landscape pattern index. Finally, based on the natural and socio-economic analysis and the reasons of the spatial differences of the basin, this paper explores the measures for soil erosion prevention and control. The results showed that (1) the most serious soil erosion zone and its evolution trend in the two river basins were different, from the point of view in the severity of soil erosion. The most serious erosion zones of Daning River Basin were in the elevation from 1 000 m to 1 200 m and in the slope from 25° to 35°, however the most serious erosion about the Meixi River Basin occurred in the elevations from 800m to 1 000m and in the slope of 25° to 35°; (2) the evolution of soil erosion were different in the two river basins. The soil evolution of Daning River Basin in >2 000 m elevation and >35° slope were the most serious, but not obvious in <200 m and 0°～5° degrees; (3) from the soil erosion landscape pattern evolution, in 800 to 1 200 m and 25° to 35° elevation slope belt, the possibility of soil erosion intensity in Daning River Basin was greater than that in Meixi River Basin. All above research results laid the foundation of the following up researches about science problem, which not only included spatial distribution of soil erosion in the height zone of 800～1 200 m with different slope and in the slope of 25° to 35° with different elevation, but also the relationship between the main natural factors and soil erosion.

Abstract:In order to get a better simulation of engineering accumulation in indoor experiment, image analysis and classical statistics methods were used to generalize the distribution and content of gravel with diameter > 1 cm on 368 engineering accumulation slopes, which were located in six water erosion regions. The generalized content intervals of gravel was obtained on different slope positions. Results showed as follows: Most gravel of different particle diameters obeyed normal distribution and there was a significant differency in the contents of gravel in mountain areas and in plain-hilly areas. The gravity separation effects of gravelwere obvious, and the bigger the gravel was, the greater the effects were. In mountain areas, it was appropriate to set the total amount of gravel between 50%~60% when designing the spoil underlying surface for laboratory rainfall simulation; the content of fine gravel, medium gravel, coarse and macrosome gravel were set in 20%~30%, 10%~15%, and 10% respectively; the content of gravel on top, middle and bottom slope of engineering accumulation are suggested to be 1∶1.3∶1.5. In hilly and plain areas, it was appropriate to set the total amount of gravel between 15%~20%, in while the fine gravel, medium gravel, coarse gravel and macrosome gravel accounted for 5%～10%, 3%～7%, 2%～5% and 2%～3% respectively. The optimized proportion of gravel on top, middle and bottom slope of engineering accumulation was 1∶1.5∶2.5.

Abstract:In this experiment, the natural rainfall was taken as the erosion power and the standard runoff plot method was used to study the formation of runoff and sediment transport in the longitudinal and cross ridge slope tilled with maize. Results showed that under continuous rainfall conditions, the process of runoff appeared as a “W-type” or an “inverted V-type”, and the sediment formation as a “W-type” or “M-type”. The time length of runoff and sediment yield was the same on the longitudinal ridge, and the total runoff and sediment yield were 1.66~5.80 times and 5.02~5.52 times of those on cross ridge, respectively. There was a significant difference between the peaks of runoff and sediment yield on longitudinal and cross ridges, and the peak phenomenon was found only between cross ridge and rainfall intensity , and 1 min was delayed. The process of runoff appeared as an “inverted V-type” under intermittent rainfall, and the sediment formation were an “inverted V-type” or “M-type”. The runoff and sediment yield on longitudinal ridge were 1.83 times and 2.32 times higher than those on cross ridge, and the first runoff accounted for more than 70% of the total, the sediment yield accounted for 94%~100% of the total. Both cross and longitudinal ridges had the peak phenomenon with rainfall intensity, and the runoff and sediment yield were delayed by 1~4 min with rainfall intensity on longitudinal ridge, 1 min on cross ridge. However, there was no peak phenomenon in the rest of rains. Under natural rainfall, the process of runoff and sediment yield was complicated on the longitudinal and cross ridge slopes. These findings could provide a theoretical basis for the prevention and control of soil erosion and the management of water and soil resources in regional sloping fields.

Abstract:Field experiment was conducted in Zhongnan hilly tea garden, and the effects of the farmers used to fertilize treatment (T1), replace the 10% chemical nitrogen or phosphorus fertilizer with organic manure (T2, T4) and organic fertilizer instead of chemical nitrogen or phosphorus fertilizer + straw covering 10% (T3 and T5) on nitrogen and phosphorus nutrient runoff erosion were explored. The results showed that compared with T1, runoff of T2 and T4 decreased by 15.4%~31.5% (P <0.05), T3 and T5 reduced by 46.8%~52.9% (P<0.01). Compared with T1, TN runoff loss of T2 and T4 decreased by 42.4% and 57.2% (P <0.05), T3 and T5 decreased by 74.7% and 74.6% (P < 0.01); Compared with T1, TDN runoff loss of T2 and T4 reduced by 18.2% and 39.2% respectively (P > 0.05), and T3 and T5 decreased by 75.6% and 74.1% (P < 0.01), and compared with T2, T4 showed extremely significant difference (P<0.01). As for NH4+-N and NO3-- N loss, there were no significance between T1 and T4 and T1 (P > 0.05), while T3 and T5 reduced by 61.5% ~ 71.9% and 78.2% ~ 71.9%, respectively (P < 0.05). Compared with T1, T2 and T4 reduced the loss of TP, but only T4 was significant (P<0.05), and TP loss of T3 and T5 reduced by 66.5% ~ 70.6% (P<0.01). In addition, TN ran off mainly through dissolved nitrogen loss (83.8% ~ 95.1%), and phosphorus ran off mainly through particle state (72.7% ~ 84.3%). Studies indicate that organic fertilizer and covering straw can effectively reduce nitrogen and phosphorus runoff loss of the tea garden, and the combination effect is better, and it is of great significance to reduce the risk of non-point source pollution, and it is suitable for large area promotion.

Abstract:In order to explore the effects of hydrodynamic erosion factors on soil detachment rate of freeze-thaw slope, two slopes (10°, and 15°), four flow rates (4.5, 6.5, 8.5 and 10.5 L/min), and four original thaw depth (2, 5, 10 and 15 cm) were designed to simulate filed runoff. By means of BP Neural Network and Stepwise Regression Analysis, we analyzed the relationship between the soil detachment rate and 7 hydrodynamic erosion factors, including stream power, unit stream power, original thaw depth, flow shear stress, flow rate, flow velocity and slope. The results showed that the rank of influence significance of hydrodynamic erosion factors from high to low was flow stream power＞unit stream power＞original thaw depth＞flow shear stress＞flow rate＞flow velocity＞gradient. Furthermore, according to BP Neural Network model, the average error of soil detachment rate prediction was 2.848% (R2=0.954). In view of Stepwise Regression Analysis model, the average error was 4.820% (R2=0.925). According to Single Hydrodynamic Erosion Factors (Stream power) model, the average error was 5.298% (R2=0.867). In general, the prediction effect based on BP Neural Network was better than others. This study provides a new idea for the establishment of soil erosion prediction model under different original thaw depths in the spring thaw period.

Abstract:By using HSC-OTT Persivel32 laser raindrop spectrum detector (Germany), raindrop size distribution under natural rainfall was detected in Nanxiaohegou basin of Jinghe River, and the characteristics and distribution of raindrops in different kinds of natural rainfall were analyzed. The relationships among the elements of rainfall characteristics were analyzed as well. Results showed that: (1) The raindrop diameter of natural rainfall was concentrated at 0.3～1.5 mm in the study area, and this result was basically identical with that on the Loess Plateau which determined by the method of traditional filter paper splash. But the raindrop diameter was smaller than those in Northeast and Minnan region. The median raindrop diameter (D50) increased with the increase of rainfall intensity when rainfall intensity (I) was less than10 mm/h. When rainfall intensity was greater than or equal to 10 mm/h, the median raindrop diameter (D50) dropped abruptly, to some extent, it was related to rupture of large raindrops after the increase of rainfall intensity. The variation of rain spectrum with rain intensity in this area could be fitted by Best distributed. (2) The distribution curve of raindrops number with the diameter was flat in common rainfall, and its kinetic energy was linearly correlated with rainfall intensity, while the distribution curve of raindrop number with diameter in short formation rainfall was steeper, and its kinetic energy and rain intensity were power function. The rainfall kinetic energy increased with the increasing of rain intensity in both kinds of rainfall, but the kinetic energy of short formation rainfall increased faster, therefore short formation rains were more erosive.

Abstract:In order to determine the temporal and spatial distribution of slope soil erosion and sediment yield under the condition of freeze-thaw cycle, rare earth element (REE) tracing technology was used in the study. Specifically, two gradients (10°, 15°), four initial thawing depths (2, 5, 10 and 15 cm) and four water flows (4.5, 6.5, 8.5 and 10.5 L/min) were designed to analysis the temporal and spatial variation of soil erosion and sediment yields. The results showed that the soil erosion and sediment yield increased with the increase of gradient and flow under the condition of the same initial thawing depth. The harvest soil erosion occurred in the first slope segment, which accounted for 68.24% of the total sediment yield, while the sediment yield was steady in third slope segment. The erosion and sediment yield increased with the increase of initial thawing depth and flow under the same slope gradient. The erosion and sediment yield reduced gradually with the slope and soil depth directions in freeze-thaw slope; In the La element tracer area, the sediment yield increased firstly, and then decreased, in other element tracer areas, the change of sediment yield was basically consistent with that of the La element tracer area.

Abstract:Soil water and salt transfer are important processes under freezing-thawing conditions in nature. The effects of soil salt concentration on soil water and heat transfer have not been investigated thoroughly under freezing/thawing conditions. The freeze-thaw characteristics of salinized soil and thecorresponding control mechanism of water-heat-salt after the mulched autumn irrigation in cold-drought-salt irrigation district were explored in the study. The field freez-thaw- experiment was conducted on the salinized soil after the mulched autumn irrigation with 5 treatments in terms of straw mulching quantity of 1.2 kg/m2 (F1.2), 0.9 kg/m2 (F0.9), 0.6 kg/m2 (F0.6), 0.3 kg/m2 (F0.3) and nomulching (CK). Results showed that: straw mulch promoted process of soil freeze-thaw, and changed the relationship between soil temperature and air temperature, resulting in the redistribution of water and salt in soil profiles, especially in the surface soil and tillage layer, which enhanced the available amount of spring water in the next year and restrained the spring salinification in surface soil and tillage layer, thus, the quality of autumn irrigation was improved. The maximum freezing depth of mulching was 4~26 cm smaller than CK, the initial freezing time and thawing time are lagged by 0~12 d and 0~21 d. The vaporization of melting water was restrained due to the straw mulch, which resulted weak surface salt accumulation. After the thawing period, the soil moisture content in F0.9 was the largest one in soil depth of 0~10 cm, and the F1.2 related ratio of desalinization was 81.18%, which was the best one among all the treatments. As for the tillage layer of 0~40 cm, the soil moisture content of F0.9 was the highest one and the best one desalinization occurred in F0.6, which was 75.65%. In order to ensure the appropriate salt content and water content in the coming year, the coverage amount of 0.6~0.9 kg/m2 is the optimal one. The findings can be used to provide references for the optimization of autumn irrigation system in Hetao Irrigation District.

Abstract:Mechanical stability of aggregate is a key factor influencing soil resistance to erosion. To investigate the variations of aggregate tensile strength for zonal soils and their stabilization mechanisms, aggregates of different sizes (1~2, 2~3, 3~5 and 5~10 mm) for six typical zonal soils (Cinnamon soil, Yellow-cinnamon soils, Brownish red soils, Red soils, Latosolic red soils and Latosols) in central-southern China were selected. In the study, the tensile strength and their relationships with soil physicochemical properties were examined. Main results were shown as follows: (1) With the increase of hydrothermal condition, soil pH and kaolinite content gradually decreased from north to south, while opposite trends were displayed in free iron (Fed) and aluminum (Ald) oxides. The content of organic matter decreased with soil depth. (2) All these soils were in heavy texture. Aggregate tensile strength generally decreased with the increase of aggregate size. For the same size aggregates, tensile strength showed a decreased trend from north to south in China. (3) Tensile strength was correlated positively with pH, silt content and vermiculite content significantly (R>0.63, p<0.01), while negatively with clay content, 1.4 nm transition mineral content, kaolinite content, Fed and Ald (R<-0.53, p<0.05). (4) Multiple stepwise regression showed that the Fed and cation exchange capacity could be used to better predict and evaluate tensile strength of 3~5 mm aggregate (R2=0.80, p<0.01). In general, the types and amount of clay mineral play a vital role in aggregate mechanical strength for zonal soils. The results?can?provide?a?basis?for?the?prediction?of?soil?erosion?and?decision-making?for?soil and water conservation.

Abstract:In order to study the effects of the seabuckthorn flexible dam on sediment in the soft sandstone gully, field experiments were carried out in the soft rock region of Inner Mongolia, and based on the experimental data of single seabuckthorn flexible dam after a rainstorm, effects of seabuckthorn flexible dam on sediment particle size distribution and organic matter and sediment retention effect of the dam were analyzed through employing the method of comparison. Results showed that single seabuckthorn flexible dam improved the organic matter content of gully sediment, and it had silt separation and fine sorting function and good sediment retention effect. The content of sediment organic matter increased from upstream to downstream of the seabuckthorn flexible dam, and the content of organic matter in middle sediment layer was higher than those in surface and bottom layer. The sediment particle size increased first and then decreased from upstream to downstream of the gully, and the same tendency appeared along the sediment profile of a rainfall deposit. After a rainstorm, the average thickness of silt deposited in unit area of seabuckthorn flexible dam was 0.369 m, and it was significantly higher than that of the control group.

Abstract:To explore the effect of soil structure on soil infiltration, the water movement characteristics of Yunnan red loam under the condition of freshwater drip irrigation was assessed by the comparison of the indoor and outdoor experiments, in which single and double point source drip irrigation with three drip discharges (2.68, 3.74, 4.68 L/h) was arranged. The soil bulk density was 1.2 g/cm3. The specifically analyzed characteristics of wetting front and wetting body under a certain drip discharge between undisturbed and disturbed soils would reveal the regional soil moisture migration rule, which provided reference basis for regional crop irrigation. The results showed that: (1) The wetting front transport rate of undisturbed soil was faster, and the earth’s surface wetting proportion of undisturbed soil increased faster than that of disturbed soil with the change of intersection time, which indicated that migration velocity of wetting front was related to soil porosity; (2) Under the same observation time, the wet body of undisturbed soil changed more quickly, and the wet body flat rate of undisturbed soil (16.53%) was greater than that of disturbed soil (45%); (3) The moisture content contour of undisturbed and disturbed soil had the same change trend, but did not overlap, while the degree of density differed; (4) The fractal dimension of undisturbed soil was less than that of disturbed soil, which indicated that the soil pore distribution of undisturbed soil differed， while the texture of disturbed soil was relatively uniform. The results revealed the soil moisture migration characteristics of undisturbed and disturbed Yunnan red loam, and provided reference for further mechanism research.

Abstract:For the exploration of how the marginal water influenced the subtropical red soil’s water transport parameters, different infiltration experiments were carried out with distilled water (CK), reclaimed water (RW), 2 times diluted, 4 times diluted and 6 times diluted reclaimed water (RW-D2, RW-D4 and RW-D6), wastewater (WW). The horizontal soil column infiltration absorption method was adopted to measure the transport velocity of wetting front and the water diffusion degree of the red soil and the pressure membrane method was applied to measure the water characteristic curve, in which van Genuchten (VG) model was used to obtain the characteristic parameters, such as residual and saturated values of the soil water content (θr , θs ), α, and n. The results showed that differences existed in the transport velocity of wetting front and the water diffusion degree of the red soil under different water infiltrating condition, the law that the transport velocity of wetting front obeyed could be described as: VCK≈VRW-D2﹥VRW-D6≈VRW-D4﹥VWW﹥VRW, under the same moisture content, conclusion could be made that DRW-D6(θ)﹥DRW-D4(θ)﹥DWW(θ)﹥DRW-D2(θ)﹥DCK(θ)﹥DRW(θ). Different water infiltrating processes had different impacts on the characteristic parameters’ changing rates of the VG model, in which α was the most sensitive while θr was the least sensitive. Therefore marginal water could reduce infiltrating velocity, water-holding capability and drought-resistant ability of the red soil.

Abstract:Based on the eddy covariance technique, the characteristics of water and heat fluxes of two alpine wet meadow wetland ecosystems in Qinghai Lake were studied in 2015. Results showed as follows: (1) The average daily water vapor fluxes of alpine Kobresia tibetica and Kobresia humilis wet meadow wetland ecosystems were 1.74 mm and 0.99 mm, respectively, and the annual water vapor fluxes were 633.3 mm and 362.1 mm, respectively, in Qinghai lake 2015. (2) The diurnal variation of sensible heat, latent heat and net radiation all showed a single peak curve in two kinds of alpine Kobresia wet meadow wetland ecosystems, the diurnal variation maximum value of the sensible heat and latent heat occurred later than the net radiation. The maximum value of the diurnal variation of the sensible heat was 179.06 W/m2 and the minimum was 46.02 W/m2; the maximum value of latent heat was 312.55 W/m2 and the minimum was 30.58 W/m2, in K. tibetica wet meadow wetland ecosystem. The maximum value of diurnal variation of the sensible heat was 161.86 W/m2 and the minimum was 31.60 W/m2; the maximum value of latent heat was 215.44 W/m2 and the minimum was 14.08 W/m2, in K. humilis wet meadow wetland ecosystem. (3) Through the analyse of bowen ratio: the energy distribution of two alpine Kobresia wet meadow was mainly latent heat in growing season; in the non-growing season the energy distribution of K. humilis wet meadow wetland ecosystem was dominated by sensible heat, K. tibetica wet meadow wetland ecosystem was more complex. The annual energy balance rate of K. tibetica wet meadow wetland ecosystem was 0.82, and the K. humilis wet meadow wetland ecosystem was 0.89, and the increase of soil heat flux item can improve the energy balance.

Abstract:Based on tissue heat balance theory, thermal dissipation sap flow velocity probes (TDPs) were used to measure sap flow velocity of Pinus tabulaeformis at Xiaowutai natural reserve in northern mountain areas of Hebei province. To explore the response of stem sap flow to environmental factors, the air temperature, relative humidity, solar net radiation, total radiation, and wind speed were simultaneously observed from March, 2015 to March, 2016. The results showed: (1) Stem sap flow of Pinus tabulaeformis started in late April and ended in late October, which lasted for 184 days at the Xiaowutai areas. On sunny days, the daily change of stem sap flow velocity presented unimodal curve in different months. There were differences in starting, peak and ending time and changing rate of stem sap flow in different months. (2) The diurnal average of stem sap flow velocity reached more than 0.02 kg/(h·cm) in every month except for April and October, especially higher in May and August in which it reached 0.028 and 0.027 kg/(h·cm). The monthly peak change of stem sap flow velocity was the same as diurnal average change. (3) Stem sap flow velocity was positively correlated with air temperature, solar net radiation, total radiation, vapor pressure and wind speed, whereas a negative correlation with relative humidity was observed. Influence of environmental factors to stem sap flow velocity was in the order of temperature > solar net radiation > total radiation > relative humidity > wind speed. (4) Water consumption of individual tree was （2 679.58±579.83）kg in the whole growth season, and the largest water consumption was in May and August with （585.14±110.92）kg and（510.08±87.96）kg.

Abstract:Numerous studies have been conducted on canopy interception and its influence on inter-rainfall isotopic composition and hydrochemical properties. However, little is known about how isotopic and hydrochemical characteristics chage in rainfall duration. The objective of this study was to understand the isotopic and hydrochemical characteristics of dwarfed jujube tree in rainfall duration. The water from stemflow, throughfall and rainfall in an open air were sampled continuously from two intra-rainfall events on Sept. 17—18 and Oct. 22—23, 2016 in the hilly and gully region of the Loess Plateau. At the same time, the volume of stemflow and rainfall in the open air were measured for four dwarfed jujubes of inter-rainfall events from July to Otc, 2016. The results showed that: (1) Average stemflow rates of dwarfed jujube was 2.3%～5.6% for inter-rainfall events; and stemflow was occurred when the rainfall amount reached 1.2 mm and 1.4mm during the two intra-rainfall evevts. (2) Relative to the rainfalls in the open area for two intra-rainfall events, the arithmetic-averaged δ2H of the throughfall and stemflow were enriched by 1.6‰～4.0‰ and 6.6‰～8.9‰, respectively; their arithmetic-averaged Cl- concentrations increased by 1.4～3.0 times and 13.3～13.4 times, respectively; their arithmetic-averaged SO42- concentrations increased by 1.5～2.7 times and 4.8～7.1 times, respectively. The throughfall and stemflow lagged behind the rainfall in the open area; during the intra-rainfall events, the delay was influenced by jujube tree canopy interception, the isotope was influenced by the prior period rainfall and further evaporation. The changes of hydrochemical components were gradually weakened with the increasing elapsed time since the start of a rainfall event.

Abstract:A typical artificial Robinia pseudoacacia plantation was used to study the characteristics of daily and seasonal soil carbon flux variation, and the changes of soil carbon flux components in different stand ages (12, 14, 15, 18 a) at Tianjiagou soil and water conservation technology garden of the Longdong Loess Plateau. Soil carbon flux was monitored using the infrared gas analysis technology and the grassland was used as control. The results indicated that the daily soil carbon flux of different ages showed significant difference (P<0.01). The diurnal soil carbon flux trend presented a single peak curve, the highest value occurred in the daytime (13:00—15:00) while the lowest was detected at night (2:00—5:00). In addition, seasonal soil carbon flux exhibited significant difference of different ages (P<0.01), The seasonal trends were in the order of summer > spring > autumn > winter. Soil carbon flux in summer was 8.78 to 20.32 times larger than that in winter. Soil carbon flux in spring was mainly with autotrophic respiration, while in summer and autumn with heterotrophic respiration, the contribution rate of autotrophic and heterotrophic respiration was basically the same in winter. For the grassland, soil carbon flux was mainly based on heterotrophic respiration in spring, summer and autumn, which was similar to R. pseudoacacia plantation in winter. The soil carbon flux of R. pseudoacacia plantation increased with the stand age with the annual soil carbon flux of 2 069.63 to 4 590.35 g/m2. The annual soil carbon flux of grassland was 2 806.27 g/m2, which was lower than that of the 18 a R. pseudoacacia plantation but higher than that of the other stand ages. Our study could provide a scientific basis for soil carbon sequestration and management measures of artificial R. pseudoacacia plantation in Longdong Loess Plateau.

Abstract:To understand the water use character of main tree species in soft sand-rock area, three main tree species (Caragana korshinskii Kom、Hippophae rhamnoides Linn. Pinus tabuliformis) in Geqiugou, Ordos, Inner Mongolia was examined using stem heart balance method to explore sap flow of these three tree species under different weather conditions and the daily change. The results showed: (1) The sap flow rates of the three tree species showed a unimodal curve, and nearly reached the peak at the same time during growing. (2) In the sunny day, the sapflow rate of Hippophae rhamnoides Linn was the highest, about 0.11772cm/s, the sap flow rate of Caragana korshinskii Kom and Pinus tabuliformis were similar; the daily average rates of the three species were 0.02901cm/s, 0.01815cm/s, and 0.02203cm/s, respectively. (3) In different weather conditions, the sapflow rates of the three species showed sunny day＞cloudy day＞rainy day, and the time when they reached the peak showed sunny day＞cloudy day＞rainy day. The results of the study are to provide theoretical basis for studying the water supply-demand relationship of plants in soft sand-rock area and environmental management.

Abstract:This research was carried out to quantify the variation of biomass carbon density and distribution patterns of Larix priucipis-rupprechtii plantation at different forest ages in Yanshan Mountainous area. The results can provide a scientific foundation of service function of carbon sequestration. According to three forest ages of L. priucipis-rupprechtii Plantation of Xinfeng Experimental Forest Farm of the Mulan State-owned Forest Farm Bureauin Hebei Province，basing on the data of 9 pieces of sample plots survey and 27 larch wood of different forest age, size order, we obtained larch biomass carbon density of different forest ages by using regression analysis, the method of quadrat harvest, soil profile sampling method and potassium dichromate oxidation-external heating method, and analyzed the characteristics and change tendency. The results showed that the performance of total ecosystem carbon density of different forest age of L. priucipis-rupprechtii plantation were 32 years (97.29 t/hm2) >21 years (90.56 t/hm2) >11 years (44.57 t/hm2), the arbor layer and soil layer were the main carbon pools, the proportion of the sum of these two was as high as 52.59%～71.51%; the carbon accumulation ability of the arbor layer increased with the increase of stand-age, the tree layer carbon density of L. priucipis-rupprechtii plantation at the forest ages of 11, 21, 32 years were 14.27, 38.57和42.37 t/hm2, and the difference reached the significant level; the carbon density of every organ of three forest ages of L. priucipis-rupprechtii were trunk >branch >root >bark >leaf, the difference of contribution rate between each organ had reached the extremely significant level. Among them, the contribution of trunk was the largest, with the increase of forest age, the proportion of carbon density of trunk increased, the proportion of carbon density of branch, leaf, bark declined, and the distribution ratio of root system was relatively stable. The tread of carbon density of the understory cover were litter layer > herb layer > shrub layer, and it increased with the increase of forest age; the carbon density of 0—60 cm soil layer showed that the carbon density decreased with the deepening of soil layer, the surface organic carbon content was the highest, and it increased with the increase of forest age, difference among different forest ages reached significant level; it was better to choose two factors of DBH and tree height to construct the model of predicting the carbon density of the tree layer with two elements. The change of carbon storage in L. priucipis-rupprechtii plantation was mainly affected by its own growth and development, at the same time, it was also affected by the density change caused by artificial tending.

Abstract:To reveal the distribution characteristics of soil organic carbon (SOC) and to study the influence of human activities on SOC in Karst area, 22 786 soil samples collected from 2 854 soil profiles were analyzed. Spatial distribution characteristics of SOC under different land uses in Guizhou Province were discussed. Combined with the control plan of rocky desertification in Guizhou Province, carbon sequestration caused by rocky desertification prevention and control was assessed. The results indicated that the SOC content in Guizhou was high, and the SOC density was low. The average SOC content in top soil (0 - 20 cm) was 25.07 g/kg, but the average SOC density was only 4.27 kg/m2. The SOC content of top soil in different land uses followed the order: shrub lands > arbor-shrub mixed forest lands > shrub grass lands > arbor forest lands > abandoned lands and uncultivated lands > grasslands > paddy lands > garden lands > arid lands and sloping croplands. The SOC density of top soil in different land uses descended in the order: paddy lands > shrub lands > arbor forest lands > arbor-shrub mixed forest lands > abandoned lands and uncultivated lands > shrub grass lands > arid lands and sloping croplands > grasslands > garden lands. The SOC content of top 60 cm soil was sensitive to human disturbance, and small discrepancies were observed among SOC contents of different land uses in deeper soil layers. If the rocky desertification prevention and control project (including returning farmland to forests, construction of artificial pasture, and artificial afforestation) was carried out efficiently, the SOC storage in Guizhou Province would be obviously promoted. Up to year 2050, at calculating depth of 0 - 10, 0 - 20, 0 - 30 and 0 - 100 cm, the total SOC sequestration caused by this project would be up to 1.99×1013, 3.37×1013, 4.45×1013 and 6.29×1013 g. In conclusion, the SOC of Karst areas was characterized by high content and low density, and the implementation of the rocky desertification prevention and control project was propitious to carbon sequestration in Karst areas.

Abstract:In order to understand the effects of vegetation restoration and ecological restoration process on soil carbon cycling, the profile distribution of soil organic and inorganic carbon under different slopes and vegetation types along two toposequences of Liudaogou watershed on the Loess Plateau (China) were investigated, and the profile distribution characteristics and the influencing factors of soil organic carbon and inorganic carbon among different slopes and among different vegetation types on the same slope were analyzed. The typical toposequences were located in the northeast slope (NE sequence) and west slope (W sequence) of the Liudaogou watershed, respectively. The results showed that soil organic carbon content decreased significantly with increasing of soil depth within 0 - 50 cm soil layer, and then remained relatively constant in the soil layer deeper than 50 cm, and the organic carbon content of the 0 - 50 cm soil layer was significantly higher than those of the 50 - 200 cm soil layers (p < 0.05). However, in the same soil depth (0 - 50, 50 - 200 or 0 - 200 cm), there was no significant difference on the mean organic carbon content under either forestlands or grasslands among different slopes (p < 0.05). Compared with organic carbon, soil inorganic carbon content was relatively high, and mainly enriched in the different soil layers deeper than 50 cm. In NE sequence, the mean inorganic carbon contents were comparable in the forestland and the grassland (p > 0.05). In contrast, in the W sequence the mean inorganic carbon content of the forestland was significantly higher than that of the grassland (p < 0.05); there was no significant difference on the mean inorganic carbon content of the grasslands among different slopes (p > 0.05), while the mean inorganic carbon content of the forestland in W sequence was higher than that in NE sequence (p < 0.05). Organic carbon content in the 0 - 50 cm soil layer was significantly negatively correlated with pH, bulk density and soil water content, but was significantly positively correlated with soil total porosity; inorganic carbon content in the 50 - 150 cm soil layer was significantly negatively correlated with pH and total soil porosity, but was significantly positively correlated with bulk density, clay content and soil water content. Soil carbon densities within 0 - 2 m profile were 15.3 ~ 47.4 kg/m2 and 18.3 - 51.3 kg/m2 in the NE sequence and W sequence, respectively, in which inorganic carbon density accounted for 78% ~ 94%. Total carbon density of 1 - 2 m soil layer were 35% ！ 74% of the total carbon density of 0 - 2 m soil profile. Our study indicated that neglecting inorganic carbon or neglecting deep soil carbon (1 - 2 m) would lead to underestimation of soil carbon stock by 88% and 51%, respectively.

Abstract:Canopy interception is a significant proportion of evapotranspiration of forest ecosystems, its quantification remains as one of hot issues in eco-hydrological studies. However, most studies were carried out just in the small scale of stand/plot. Since the canopy interception is influenced by many factors (e.g. rainfall, meteorological condition, canopy structure and growth process) at the stand/plot scale, and by the difference of forest canopy structure among slope positions, it often appears great spatial variation and scale effect at the slope scale. In order to realize the up-scaling from the measured value at plot to the whole slope, and to provide scientific basis for the accurate evaluation of forest hydrological impacts, the spatial-temporal variation and scale effect of canopy interception along the slope has to be precisely described based on deep-going studies. In this study, a representative slope with a horizontal length of 425.1 m and covered by Larix principis-rupprechtii plantation was selected in the small watershed of Xiangshuihe of Liupan Mountains in northwest China, and it was evenly divided into 16 continuous plots. In the growing season of 2015 (from May to October), the dynamics of stand/plot canopy structure (especially the leaf area index, LAI) in different months and its difference among the 16 plots along slope position were monitored; meanwhile, the gross rainfall at open field and the throughfall and stemflow was measured to calculate the canopy interception of each plot during each rainfall event. The variation of canopy interception along slope positions and within different months and their main influencing factors were analyzed using the “horizontal distance from the slope top (horizontal slope length)” as a scale scalar. The results showed that the canopy interception presents a remarkable variation along the slope and spatial scale effect, with a remarkable difference among the months. During the whole growing season, the overall variation tendency of canopy interception with rising horizontal slope length showed firstly an increase, reaching its maximum at the middle slope, and then a decline. The scale effect was +5.62 mm/100 m within the horizontal slope length of 0~316.6 m and -2.37 mm/100 m within the horizontal slope length of 316.6~425.1 m. In May, the variation of canopy interception along rising horizontal slope length showed a decreasing tendency, with the scale effect of -0.26 mm/100 m within the horizontal slope length of 0~425.1 m. In June, July and August, the variation tendency of canopy interception along slope length was consistent with the whole growing season. In June, the scale effect was +1.28 and -1.78 mm/100 m within the horizontal slope length of 0~261.1 m and 261.1~425.1 m. In July, the scale effect was +0.92 and -0.88 mm/100 m within the horizontal slope length of 0~267.6 m and 267.6~425.1 m. In August, the scale effect was +1.28 and -0.34 mm/100 m within the horizontal slope length of 0~211.2 m and 211.2~425.1 m. In September and October, the variation of canopy interception along the slope showed an increasing tendency. The scale effect was +2.38 and +0.81 mm/100 m within the horizontal slope length of 0~425.1 m, respectively. The LAI was the main factor affecting the spatial-temporal variations of canopy interception. The correlation between canopy interception ratio and LAI was positive and significant in every month. The slope average of canopy interception could be estimated through the up-scaling from the measured LAI at certain plot, the relation between plot LAI at different slope positions and the slope average of LAI, and the relation between canopy interception and plot LAI.

Abstract:Soil inorganic carbon is the main carbon form in arid area. Its distribution can affect the pattern of carbon accumulation and storage in the soil profile. Due to the lack of soil profile data in deep soil layer, the carbon distribution and carbon storage characteristics of soil profiles are hard to accurately quantify, so the amount of inorganic carbon in soil is uncertain. This research was conducted on two typical kinds of land (farmland and uncultivated land) in the Sangong River watershed of Xinjiang, China. Soil profiles were sampled from topsoil to deep soil until to near shallow groundwater, and a total of 190 samples were obtained in six soil profiles. The distribution characteristics of soil inorganic carbon (SIC) and soluble salt ion in the sampled soils were analyzed, and the relationship between inorganic carbon and soil salinity was studied by redundancy analysis. The results revealed the following: (1) the SIC content of farmland was significantly higher than that of the uncultivated land (p <0.05), and the SIC content of farmland increased by 27.9%, the range of change increased by 3.66 times compared with uncultivated land. Besides, the SIC contents of profiles in the uncultivated land and farmland were exhibited a distribution of "S" type and "M" type, respectively. (2) The soluble salt ions content of the farmland was significantly lower than that of the uncultivated land in the same soil layer (p <0.05), and the distribution of soluble salt ions content in soil profile showed an increase- decrease trend in the uncultivated land, while a decrease trend in the farmland, and which indicated that the quantity and distribution characteristics of soluble salt ion content in soil profile were significantly changed by agricultural activities. (3) The reverse of soil inorganic carbon of all soil profiles followed the order of 0 - 100 cm soil layer < 100 - 300 cm soil layer < below 300 cm soil layer, and the values were significantly different among three soil layers, however, at same soil layer the proportions of soil inorganic carbon reverse were basically the same in uncultivated land and farmland, the values of three soil layers were 10%, 35% and 55%, respectively （p<0.05）. (4) The order of the contribution of soil salinization factors to SIC was get through the redundancy analysis, and positive correlation was listed in the order of pH > ESP > SAR > CO32- > HCO3-, negative correlation was listed in the order of K+ > Ca2+ > Mg2+ > Cl- > Salt > SO42- > Cl- > Na+.

Abstract:A pot experiment was conducted to study the effects of different W-OH concentration (1%, 3% and 5%) on the maize growth and soil nutrient leaching. The results showed that W-OH could effectively promote maize growth and the effect became gradually obvious since the middle stage of maize growth. Under the current experimental conditions, the light and moderate W-OH concentrations (1% and 3%) were more beneficial to maize growth. After potting 3 months, compared with CK (without W-OH), under the light and moderate W-OH treatments, the maize height increased by 16% and 35%,the net photosynthetic rate increased by 3% and 17%,the stomatal conductance increased by 34% and 79%,and the transpiration rate increased 2 and 3 times, respectively. The precipitation had a different influence on water retention of W-OH. For light and moderate rainfall, 3% treatment had the lowest leakage, showing the most significant water retention effect. For heavy rainfall and rainstorm, the water retention effect of W-OH was positive related to its spraying concentration. The fertilizer retention effect of W-OH was positive related to its spraying concentration at the initial stage of maize growth and tended to be stable with subsequent rainfall leaching. During the observation period, both 3% and 5% treatments effectively reduced the total nutrients leaching loss, especially for nitrate nitrogen. The findings can provide scientific guidance for application of soil stabilizer in slope land.

Abstract:In order to confirm the effects of planting types on the vertical distribution of soil organic carbon (SOC), five typical planting types of terraces in the Baozigou basin located in Gansu province were studied, which included maize, wheat, potato, apple and intercropping (apple+potato). SOC content, storage and the controls were studied to investigate the effects of planting types on the stability of SOC in 0—200 cm soil layer. The results showed that: (1) The content of SOC in 0—200 cm ranged from 3.33~4.86 g/kg, and the differences among different planting types were significant; SOC in intercropping and apple were significantly higher than those in maize and wheat (P<0.05); SOC was significant different in different soil layer, and the content of SOC in 0—20 cm soil layers were significantly higher than other layers and the difference were slightly with the soil depth increased. The storage of SOC ranged from 8.0 t/hm2to 11.69 t/hm2, and the difference was more outstanding among different planting types; specifically, SOC storages in intercropping and apple were significantly higher than those in maize and wheat. (2) The distribution ratio of SOC in 0—20, 20—100 and 100—200 cm accounted for 17.57%, 41.21%, and 41.22%, respectively. The influences of different planting types on the stability of SOC distribution were small. Among different planting types, the ratio of the SOC storage in 0—20 cm to 20—40 cm soil layer were 1.51~1.78, 0—20 cm to 40—60 cm soil layer were 1.78~2.02, which indicates that soil is developing to maturation and soil quality is significantly improved. (3) Moisture has an effect on the vertical distribution of SOC; planting types had certain influences on the distribution and the storage of SOC, the apple orchard of terraced fields in the loess hilly region had a good advantage on the improvement of soil organic carbon in the Loess Plateau.

Abstract:Based on the indoor simulation experiment, the effects of amendment (biochar and calcium peroxide) on microbial biomass carbon, nitrogen and dissolved organic carbon and nitrogen in upland red soil were studied. The experiment included 4 treatments, namely CK, Ca (calcium peroxide, 1.72 g/kg), C (biochar , 21.46 g/kg), and C+Ca. The results showed that soil microbial biomass carbon, nitrogen and dissolved organic carbon had the same change tendency, which increased rapidly within 3 days, and reached the maximum on the third day, and then decreased with the time. Additionally, the effect of combined application of the two amendments was better than that of single application. The dissolved organic nitrogen increased slowly within 21 days; compared with CK, dissolved organic nitrogen under C+Ca, Ca, C treatments significantly increased by 62.1%, 55.5%, and 40.9% on twenty-first days, respectively; after 35 days, the effects of C+Ca and Ca was significantly better than those of C and CK. During the 120 day incubation period, C+Ca treatment could significantly improve the average content of microbial biomass carbon, nitrogen and dissolved organic carbon and nitrogen; the ranking of average content of microbial biomass carbon from high to low was: C+Ca>C>CK>Ca, and the average content of microbial biomass nitrogen in C+Ca treatment was significantly higher than those of other treatments. the ranking of average content of soluble organic carbon was C+Ca>Ca>C>CK, and they were significantly higher in C+Ca and Ca than those of CK and C. There was a significant positive correlation between microbial biomass carbon, nitrogen and dissolved organic carbon (P<0.01), but there was a significant negative correlation between microbial biomass carbon and dissolved organic nitrogen. Therefore, biochar and calcium peroxide can effectively improve soil microbial biomass carbon, nitrogen and dissolved carbon and nitrogen in upland red soil, and the combination of biochar and calcium peroxide is more beneficial to soil improvement.

Abstract:In order to explore the effects of different straw returning methods on microbial biomass carbon, nitrogen, phosphorus and soluble organic matter under rape/corn rotation system, field experiments were conducted on the purple soil, which was widely distributed in southwestern hilly region of China. This study was expected to contribute to the comprehensive and rational utilization of straw. The results showed that straw directly returning (CS), biochar returning (BC), straw with transformation promoter returning (CSD), equivalent straw and biochar returning (CSB) could all effectively increase the contents of soil microbial biomass carbon, nitrogen and phosphorus. The contents of soil microbial biomass carbon and phosphorus in CSD treatment were the highest, which were 46.32% and 94.09% higher than CK (single chemical fertilizer). Microbial biomass nitrogen content in CSB treatment was the highest followed by CSD treatment, which reached 104.47 mg/kg and 104.14 mg/kg, respectively. Except BC treatment, other treatments improved soluble organic carbon content by 63.26% · 189.46%, and the value of CSD treatment was most distinct, reaching 72.74 mg/kg. Four straw returning treatments decreased the content of soil soluble organic nitrogen (DON) comparing with CK, while the content of soil soluble organic phosphorus (DOP) increased, especially CSD treatment had the best effect on the improvement of soil soluble organic phosphorus. Compared with CK, straw returning reduced the DON/TN, but effectively increased the SMBC/SOC (except BC treatment), CS and CSD treatments had more expressive performance. DOC/SOC and SMBN/TN in CSD treatment were the highest, which reached 0.49% and 7.66%, respectively. Compared with CK, all straw returning treatments could increase the yields of rape and maize by 3.37% ~ 7.01% and 1.49% ~ 3.92%, respectively. CSD treatment was the best among four treatments. The best straw returning method under rape/corn rotation system in purple soil of southwestern hilly region was straw with transformation promoter returning, which had the highest active organic matter and was beneficial to increase soil productivity.

Abstract:Soil organic carbon (SOC) and humus components ( humic acid, fluvic acid, and humin etc.) in the soil layer of 0 - 80 cm under three irrigation modes (furrow irrigation, drip irrigation and subsurface irrigation) were studied through 13 years of continuous tomato cultivation irrigation experiment. And the effect of irrigation methods on the properties of soil organic matters in greenhouse was evaluated. The results demonstrated that SOC content and the contents of humus components in three treatments declined with the increasing of soil depths. This kind of change mainly concentrated in the 0 - 50 cm soil layer, and the change in 50 - 80 cm soil layer was less. However, the SOC and its components were significant different among irrigation methods. The soil profile was divided into two layers, the upper (0 - 20 cm) and the lower (20 - 80 cm). The total SOC contents in the upper layer of three irrigation methods was in the order of subsurface irrigation > furrow irrigation > drip irrigation, and in the lower layer the order was drip irrigation > furrow irrigation > subsurface irrigation. For soil humus acid contents of three irrigation methods, in the upper layer the order was drip irrigation > furrow irrigation > subsurface irrigation, and in the lower layer, the order was subsurface irrigation > drip irrigation > furrow irrigation. For soil humin contents of three irrigation methods, in the upper layer the order was furrow irrigation > drip irrigation > subsurface irrigation, and the humin content in the lower layer was in the order of subsurface irrigation > drip irrigation > furrow irrigation. Drip irrigation could make the SOC content remain at a high level in the 0 - 40 cm soil layer, and soil humus content was higher than that of the other two irrigation methods, and this was beneficial to improve the soil fertility level and ensure the nutrient supply of tomato.

Abstract:To definite the mechanism of the effects of exogenous organic carbon on soil organic carbon transport, we studied effect of exogenous organic carbon on concentrations and mineralization characteristics of soil organic carbon (SOC) and particular organic carbon (POC). We conducted a 5-year outdoor culture combined with the mineralization culture to analyze the translocation. There were 5 treatments: single chemical fertilizer, cow manure combined chemical fertilizer, chicken manure combined chemical fertilizer, corn stalks combined chemical fertilizer and poplar leaves combined chemical fertilizer. The results showed that: (1) SOC loss amount of the control in black soil mainly came from POC loss. The exogenous organic carbon was conducive to the accumulation of SOC and POC. Compared with the control, the average SOC and POC of animal manure treatments increased 16.6% and 27.8% respectively; plant residues treatments increased 27.0% and 46.4% respectively; (2) The dynamics of both SOC and POC mineralization preferably followed the first-order kinetics (R2 > 0.9). POC was more easily mineralized than SOC. The 60 days cumulative mineralization amounts of POC were 3 times higher than SOC; (3) The average POC mineralization rate of the treatments added animal manure or plant residues was 31.5% and 29.8% respectively. POC of animal manure treatment was easier to be mineralized. (4) The mineralization of black soil organic matter can be retarded by the addition of exogenous organic matter, especially the cow manure. The SOC mineralization rate of the cow manure treatment was 1.9%, 3.4% lower than the control. The POC mineralization rate was 24.8%, 17.4% lower than the control; (5) The ability of storage carbon of exogenous organic carbon in black soil followed the order of poplar leaves > corn stalks > cow manure > chicken manure.

Abstract:A field experiment was carried out in a six-year apple orchard to explore effects of 15N-urea absorption, utilization, loss and residue in the 0—60 cm soil layer of the orchard under different topdressing nitrogen applications (once, twice and other eight times) at fruit swollen stage using the 15N-labeled tracer method. Results showed that the highest Ndff value of different newborn organs (leaf, new shoots and fruits) were in the treatment received eight-time topdressing nitrogen application, and the lowest were found in the treatment received one-time topdressing nitrogen application at fruit expanding stage. At fruit maturity stage, the 15N absorption of the treatment received eight-time topdressing nitrogen application were 1.61 times and 2.10 times of the treatment received two-time and one-time nitrogen topdressing application respectively. The highest distribution ratio of 15N in vegetative and reproductive organs was in the treatment received eight-time topdressing nitrogen application, and the lowest was in the treatment received one-time topdressing nitrogen application at fruit maturity stage. With the passage of time, the amount of 15N residue in 0—60 cm soil layer of the treatment received eight-time topdressing nitrogen application was gradually higher than the treatments received two-time and one-time topdressing nitrogen application, and it was found mainly in the 0—40 cm soil layer. At fruit maturity stage, the plant 15N utilization rate of the treatment received eight-time topdressing nitrogen application was 17.65%, which was obviously higher than the treatment received two-time (10.99%) and one-time (8.37%) topdressing nitrogen application, and 15N loss rate the treatment received eight-time topdressing nitrogen application was 47.54%, which was obviously lower than the treatments received two-time (59.05%) and one-time (67.92%) topdressing nitrogen application. In short, all the findings indicated that eight-time topdressing nitrogen application at fruit swollen stage achieved the optimal effect, which could significantly reduce nitrogen loss rate, ensure steady and adequate supply of nitrogen and consequently improve nitrogen utilization rate, so as to exert its effect on the highest nitrogen demand of fruit trees.

Abstract:Analyzing the impact of climate change on agricultural production is beneficial to develop appropriate strategies and protect food security. In the study, the trends of meteorological factors in 1957-2013, and the effects of temperature and CO2 concentration on winter wheat yield were simulated by AquaCrop model in Northern Shaanxi Province. The results showed that the annual temperature in Northern Shaanxi increased at a rate of 0.22 ℃/10 a, while the annual precipitation decreased at a rate of 0.15 mm/10a in 1957-2013. With an increase of 0.1 ℃ in the annual temperature, the winter wheat yield in Yulin and Yan’an increased by 1.5% and 0.5%, respectively. When annual CO2 concentration increased by 10 μmol/mol, the winter wheat yield increased by 3.8% and 2% in Yulin and Yan’an, respectively. When the annual temperature and CO2 concentration rose simultaneously (i.e., temperature rose by 0.1 ℃ and CO2 concentration increased by 10 μmol/mol), the winter wheat yield increased by 5.1% and 2.3% in Yulin and Yan’an, respectively. Only considering the variation of temperature and CO2 concentration, the warm-dry and high-carbon climate were beneficial to improve wheat production in Northern Shaanxi. The winter wheat yield would increase at different degrees in the next 18 years in the Northern Shaanxi region. Under three typical years (i.e. dry, normal and wet year), the winter wheat yield in 2020, 2025 and 2030 in Yulin would increase by 21.2% ~ 31.8%, 25.4% ~ 36% and 29.7% ~ 40.7% respectively compared to that in 2012, whereas, the wheat yield in Yan’an would increase by 3.3% ~ 8.3%, 4.4% ~ 9.7% and 4.8% ~ 10.5%, respectively. Therefore, it is suitable to increase the winter wheat planting area moderately to increase agricultural output in Northern Shaanxi.

Abstract:The study focused on the effects of maltose and other carbohydrates on the improvement of continuous cropping soil and the growth of apple rootstock, and the findings could provide a new way to alleviate the apple continuous cropping obstacles currently. In April 2014, seedlings of Malus hupehensis Rehd were planted in pot with 10 kg continuous cropping soil, and the doses of four kinds of carbohydrates, fructose, glucose, maltose and arabinose of 50, 100, 200 mg/kg were added to the seedling pot after the seedlings grew 5 euphyllas. Then the growth, soil microbes and soil total organic carbon (TOC) were measured in September 2014. Compared with CK， the height increased by 52.9% with the glucose of 200 mg/kg, the diameter increased by 12.2% and the relative contents of chlorophyll increased by 12.5% with the maltose of 200 mg/kg, the photosynthetic rate increased by 18.5% with the glucose of 100 mg/kg. The fructose and arabinose could effectively increase the number of bacteria in the soil, which increased by 119.7% and 127.6%,respectively with the application of the concentration of 50 mg/kg. The number of actinomycetes in the soil increased significantly by 66.7%, 222.9% and 266.7%, respectively with the increase of different arabinose concentration. The number of fungi decreased significantly by 71.7% than CK with the application of 50 mg/kg maltose. The total organic carbon content was the highest when applied the glucose of 100 mg/kg and increased by 60.0% than CK. The principal component analysis showed that there were significant differences between the maltose of 100 mg /kg and CK, compared with CK,the height, the diameter, the leaf relative contents of chlorophyll, the photosynthetic rate, the TOC increased by 47.9%, 11.1%, 8.5%, 16.3%, and 47.6%, respectively, while the number of actinomycetes decreased by 49%. In summary, the maltose of 100 mg/kg can improve the quality of apple rootstock obviously, which are useful for the improvement of continuous cropping soil and the number of soil fungi in continuous cropping soil.

Abstract:We examined the physical and chemical properties of reclaimed soil in coal-mining subsidence areas, and the influences of biochar and combined application with organic and chemical fertilizers for three consecutive years.The results were as follows: all treatments could improve soil physical, chemical and biological properties. Compared with the control, organic + biochar treatment significantly decreased the soil bulk density by 10%, and increased soil pore water content by 7.14%, while the change of soil pH was not obvious. Compared with chemical fertilizer treatment, Soil available phosphorous, potassium in chemical + biochar treatment increased by 8.33%, and 6.34%, respectively, whereas biochar had little effect on soil alkaline nitrogen， little increase in the number of bacteria, fungi, actinomycete in organic+biochar treatment; the number of fungi increased significantly by 11.7% in chemical + biochar treatment. Corn production in organic + biochar treatment and chemical + biochar treatment increased by 3.03%, and 2.70% respectively, while biochar had little effect. Therefore, the application of organic and chemical fertilizer is beneficial to improve the reclaimed soil, while biochar is?of?no use.

Abstract:In the present study, the field investigation and indoor analysis were conducted to study the litter characteristics, soil physical features, soil infiltration characteristics and water retention capacities of different vegetation types in dump of opencast coal mine, and water retention capacities were evaluated by principal component analysis. The results indicated that the thickness and amount of litter were different significantly (P<0.05) among three vegetation types, and the litter thickness of arbor land, shrub land and weeds land were 1.80, 1.23, and 0.83 cm, respectively, and the litter accumulation of three vegetation types were 6.76, 2.96, and 0.58 t/hm2, respectively. The water retention capacity and interception capacity of litter in arbor land was the maximum, which was significantly greater than those in shrub land and weeds land (P<0.05). The soil bull density was in the order of weeds land > shrub land > arbor land. The soil infiltration capacity of arbor land and shrub land were significantly greater than that of weeds land, and the infiltration rate, the stable infiltration rate and cumulative infiltration of three vegetation types were 1.53 ～ 4.08 mm/min, 0.20 ～ 1.51 mm/min, 28 ～133 mL, respectively. The actual storage capacity of arbor land and shrub land were both greater than that of weeds land, and the water storage efficiency of arbor land and shrub land were significantly higher than that of weeds land (P<0.05). The water retention capacities of different vegetation types were evaluated by principal component analysis. Fifteen indicators were optimized into 3 principal components, with a cumulative contribution rate of 96.832%. The water retention capacities of different vegetation types were in the order of arbor land > shrub land > weeds land. To improve the water retention capacity of litter and soil of dump, arbor (Robinia pseudoacacia) could be selected as the main reclaimed vegetation.

Abstract:In this study ,we used soil physicochemical properties analysis were conducted in artificial Camellia oleifera forests with different ages (1 years and 15 years) in red soil hilly region of Yushan County, Jiangxi Province. Soil samples were collected in different slope positions (upper slope, middle slope, and lower slope) and different soil layers (0 – 10 and 10 – 20 cm). The results showed that: (1) with the increasing of the artificial Camellia oleifera forest age, there was a decrease in soil bulk density, and an increase trend in soil water content and field capacity; significant increases in soil pH value and organic matter content of middle and lower slope (P<0.05) were observed, and the contents of total nitrogen, total phosphorus and total potassium decreased; soil physicochemical properties improved after horizontal Planting Camellia oleifera in red soil slope land, and soil water content, field capacity and soil organic matter content increased in varying degrees, while soil bulk density and nutrient (N, P, K) content decreased, therefore reasonable fertilization, especially the application of P fertilizer, should be pay more attention to meet the need of the production during tending process of Camellia oleifera forest. (2) The soil physicochemical properties showed certain regularity in different slope positions. The soil bulk density of different slope positions followed the order of upper slope < middle slope < lower slope; and the water content of upper slope was the maximum, and the minimum field capacity was in lower slope; soil organic matter and total potassium both followed the order of upper slope < middle slope < lower slope, and there was significant difference in soil organic matter among different slope positions, while there was no significant spatial difference in total nitrogen and total phosphorus. (3) Compared with the 1 year Camellia oleifera forest, the spatial difference of soil physicochemical properties tended to be homogeneous in the 15 a stands. In order to reveal soil and water conservation effect of the combination measures of horizontal soil preparation and artificial Camellia oleifera, and to provided the theoretical basis for the comprehensive management of soil erosion and for the sustainable management of artificial tea tree land in the southern red soil slope.

Abstract:To clarify the physiological responses and compare the resistance intensities of two Ardisias pecies to the treatments of cadmium stress, hydroponic experiment was carried out with 2 years old seedlings of Ardisia crenata Sims. and Ardisia mamillata Hance. In the experiment, the cadmium concentrations were designed as 0, 0.025, 0.05, 0.1, 0.2, and 0.4 mmol/L. Several physiological indicators including plant height, superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities, proline (Pro), content malondialdehvde (MDA) content, photosynthetic characteristics, and fluorescence characteristics were measured. The following results were obtained: (1) Plant height, SOD, POD, and CAT activities of A. crenata and A. mamillata first increased with the increase of incubation time, and then the first two indicators decreased significantly; (2) After 20 days treatment, the accumulation of Pro content in the two plant species was induced for low cadmium concentration treatment (T2), especially significant for A. mamillata, which was up to 149.24%; (3) After 20 days treatment, MDA contents increased, with the highest increases of 169.07% and 122.70%, respectively; (4) An obvious increase of photosynthetic electron transfer efficiency (ETR) of A. mamillata was observed for low cadmium concentration treatment (T2), while qP (photochemical quenching coefficient) had no significant change, indicating that A. crenata startes the energy dissipation pathways sufficiently to avoid the damage of photosynthetic mechanism; (5) Both ETR and qP of A. mamillata decreased significantly after treatment with high concentration of cadmium (T4), indicating that PSII of A. mamillata has been hurt under the high concentrations of cadmium stress with the increasing of SOD and the damage of chloroplast structure; (6) ETR fluorescence parameters of A. crenata descended even in early stage of cadmium stress, and the decrease was much more significant in the later stage. After comprehensive analyses, it is supposed that both A. crenata and A. mamillata increase their antioxidant enzyme activities to resist stress for treatments with low cadmium concentrations, whereas high concentrations of cadmium destroye antioxidant enzyme and photosynthetical systems and thus decrease plant resistance. It is found that A. mamillata had higher resistance to cadmium than Ardisia crenata Sims, and has high potential for cultivation under the environment with high concentrations of cadmium.

Abstract:In order to reveal the correlation between Cd uptake and photosynthetic physiological characteristics of Solanum nigrum L., pot experiments in greenhouse were conducted to investigate the Cd uptake and physiological response of Solanum nigrum, during its mature growth stage under five levels of Cd (0, 2, 5, 10 and 20 mg/kg, denoted as Cd0, Cd2, Cd5, Cd10 and Cd20 respectively). The results showed that Solanum nigrum had a strong resistance to Cd, which could grow normally in 20 mg/kg Cd contaminated soil, and the Cd accumulation coefficient and translocation factor of Solanum nigrum in the Cd contaminated soil with ≤ 10 mg/kg were both larger than 1, however, when the soil was heavily polluted (20 mg/kg), the Cd uptake and transfer ability of Solanum nigrum decreased significantly (p<0.05). In general, the Cd content in the overground of Solanum nigrum was larger than that in the underground of Solanum nigrum, and the Cd accumulation in oveground parts of Solanum nigrum in five Cd levels were all significantly (p<0.05) larger than that in underground parts, which was about 10~15 times more. At the same time, the increase of soil Cd concentration could cause not only the changes of Cd uptake and transfer of Solanum nigrum, but also cause the changes of its photosynthetic physiological characteristic. The photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) of the flag leaf in Cd10 treatment were significantly higher ( 23.71%~79.80%) than those in Cd0, Cd2, Cd5 treatments（p<0.05）, while the photosynthetic intensity of Solanum nigrum was significantly decreased as Cd content of soil reaches 20 mg/kg. The results of correlation analysis showed that the Cd uptake by Solanum nigrum was mainly affected by soil Cd concentration (SCCD), and had no significant correlation with the internal factors, such as Tr and Gs. Therefore, it is not a good choice to improve the uptake and accumulation of Cd in Solanum nigrum by the physiological regulation of Solanum nigrum; further researches need to be done to reveal the mechanism and regulation of Cd uptake in Solanum nigrum.

Abstract:The effects of Cd stress (0, 3, 6 and 9 mg/kg) on the growth, Cd accumulation and soil enzyme activities of Miscanthus sacchariflorus were studied by pot experiments from seed germination and cultivation for 132 d. The results showed that: The tolerance index of Miscanthus sacchariflorus increased at first and then decreased with the increase of the concentration of Cd. It was beneficial for plant growth when the concentration of Cd was no more than 6 mg/kg, whereas the growth was suppressed when the concentration of Cd was greater than 9 mg/kg. With the increase of Cd concentration, the content of chlorophyll, MDA and soluble sugar in leaves increased firstly and then decreased, and the peak appeared in 6 mg/kg Cd concentration; while the carotenoid content of leaves showed?a?contrary?tendency with the increase of Cd concentration. Three micronutrients (Cu, Zn and Fe) in root increased gradually with the increase of Cd concentration. Specifically, with increasing Cd concentration, Cu and Fe concentrations in aboveground part decreased at first and then increased, while Zn concentration showed a?continued?slowdown. Cd concentration of root and aboveground part rose gradually with increasing Cd concentration and the distribution of Cd was higher in root than in aboveground part. The root bioconcentration factors (BCF) of Miscanthus sacchariflorus exceeded 1 in various Cd concentrations, but the aboveground part BCF and translocation factors (TF) were less than 1. Cd accumulation of root increased at first and then decreased with the increase of Cd concentration; while Cd accumulation of aboveground part increased all the time. Furthermore, root was the main part of Cd accumulation. Soil enzyme activities had no significant differences among different Cd concentration (P > 0.05). Soil urease activity was promoted by Cd concentrations of 6 and 9 mg/kg, while, soil catalase activity was inhibited. Overall, the enzyme activities of urease and catalase in rhizosphere were high than those in non-rhizosphere. The findings indicate that Miscanthus sacchariflorus has high tolerance to Cd and the root presents strong capacity to accumulate Cd, therefore the plant had a certain potential in the stabilizing remediation of Cd contaminated soils.

Abstract:Pot experiments were carried out to evaluate the influence of Bacillus megaterum LY02 inoculation on phytoremediation of Cd, Cu and Cd-Cu contaminated soil by Lolium perenne L. The results showed that inoculation B. megaterum LY02 in Cd, Cu and Cd-Cu contaminated soil significantly increased the aboveground biomass of Lolium perenne L by 65%~108.3%. The strain promoted phytoextration of heavy metal by Lolium perenne L in different kinds of contaminated soil, and Cd extraction was increased significantly by 45.8% compared with the control. Compared with the control, B. megaterum L siginificantly enhanced the available phosphorus in three kinds of contaminated soil by 18.2%, 26.7% and 16.2%, respectively. The available Fe was increased after inoculation, especially in Cu-contaminated soil, the increase was up to 152.5%. Furthermore, the content of available Cd and Cu in the rhizosphere were also enhanced in the three kinds of contaminated soil, the available Cu was increased by 49.7% in the Cu-contaminated soil. Above all, inoculation B. megaterum LY02 in Lolium perenne L can improve the content of available P and Fe in the contaminated soil, and enhance the content of available Cd and Cu, which are beneficial for the improvement of remediation efficiency of Lolium perenne .

Abstract:To investigate the effects of nano-TiO2 on the adsorption and desorption of Hg2+ in soil of the drawdown area of the Three Gorges Reservoir, nano-TiO2 particles of different crystal structures (anatase and rutile) were selected, and were added to soil to preparade four concentrations (0, 2, 4, and 8 g/kg) samples. Meanwhile, Hg2+ solutions with different Hg2+ concentrations were preparade to conduct the Hg2+ adsorption and desorption experiments. The results showed that nano-TiO2 particles increased Hg2+adsorption capacity of soil, but it was affected by the crystal form and concentration of nano-TiO2 particles. The adsorption capacity of anatase particles was stronger than that of rutile particles, and adsorbed Hg2+ was difficult to be desorbed. In anatase particles treatments, when the concentration of nano-TiO2 particles was 4 g/kg, its Hg2+adsorption capacity was the largest, which was 32.65% higher than that of the control group, and its desorption rate was lower than that of the control group. In the treatments with rutile particles, the amount of adsorbed Hg2+ increased with increasing of particle concentration, however Hg2+ was easily desorbed. When the particles concentration was 8 g/kg, its adsorption capacity was the maximum and was 18.18% higher than that of the control group, but its desorption rate was the largest. Nano-TiO2 particles, especially anatase particles, enhance the Hg2+ adsorption capacity of soil, and this may impact the migration and transformation of Hg2+ in the environment.

Abstract:The pot experiment was conducted to investigate how alfalfa, Fusarium sp. ZHH2, starch as well as their combination of different size could remove high molecular weight PAHs (HMW-PAHs) in agricultural soil in a coal mine area. The results showed that the removal rate of 6 types of individual HMW-PAHs (BbF, BkF, BaP, DbA, InP and BghiP) was in the range of 4.22%~45.01% in alfalfa treatment (M). There were significant differences among the combined treatments using different inoculum size of ZH-H2 and alfalfa (H1+M, H2+M, H3+M) for the degradation of HMW-PAHs. And the range of removal rates of 6 types of HMW-PAHs were 11.01%~ 45.30% and 15.20%~43.58% for treatment H1+M and H2+M, respectively. Compared with M treatment, the removal rates of BkF in teatment H1+M and H2+M increased by 1.62 times and 2.60 times respectively, whereas the other PAHs had no significant difference. However, compared to treatment M, H3+M treatment had a significant negative effect on the removal of HMW-PAHs . On the basis of H and M combination, starch of different size was added to improve the removal of these HMW-PAHs in soil. Further, the effect of the three factors treatments (D1+H1+M, D1+H2+M, D1+H3+M, D2+H1+M, D2+H2+M and D2+H3+M) on HMW-PAHs removal was analyzed. The results showed that the removal rates of BbF, BkF, BaP, InP, DbA and BghiP in the D1+H2+M treatment were the highest among all treatments of three factor combinations, which were 28.87%, 54.59%, 47.04%, 65.91%, 66.42%, and 71.88% respectively. And there was no significant difference between D1+H1+M and D1+H2+M in the removal of each HMW-PAH. Compared with H2+M treatment, the removal rate in the D1+H2+M treatment increased significantly by 0.46, 2.59, 1.71, 1.15, 0.52, and 1.37 times, respectively (P < 0.05). Therefore, the combination of Fusarium sp. ZH-H2, starch and alfalfa offers a suitable alternative for phytoremediation of aged PAH-contaminated soil in coal mining areas, with a recommended inoculation size of 0.5 g Fusarium sp. ZHH2, 0.25g starch per kg soil with the growth of alfalfa.

Abstract:To analyze the changes of water carrying capacity in Hanzhong City and to reflect the safety degree of water use in order to find ways and methods to improve the carrying capacity of waters. In this paper, the ecological carrying capacity of Hanzhong City is calculated and analyzed. From 2001 to 2013, the ecological carrying capacity of Hanzhong City is in a safe state, but the ecological carrying capacity index of the waters is larger and the safety degree is gradually reduced. Hantai area of ecological carrying capacity index is 0.56, in the basic safety state, the remaining counties ecological bearing capacity index of less than 0.50, is in safe condition. Among them, the Ningqiang, Lueyang, Zhenba, Liuba, Feping five counties of ecological carrying capacity index is less than 0.10; Yangxian, Xixiang, Mianxian three county of ecological carrying capacity index in 0.20～0.30,Nanzheng capacity index in 0.30～0.40, ChengGu index in 0.40～0.50. But a drop in ecological pressure increased, the ecological carrying capacity, safety degree gradually reduce the trend, suggest grassland, take next to fishery production planning, strengthen management of water ecological environment protection and strengthen the monitoring of water management measures to improve the water ecological carrying capacity.