Abstract:Analyzing the carbon sequestration function and evaluating the carbon sequestration capacity of Yudiba dams is a crucial prerequisite for determining the carbon sequestration effects of Yudiba dams and other soil and water conservation measures, and can provide valuable data references for achieving carbon emission peak and carbon neutralization. Here, we take the Yudiba dams on the Chinese Loess Plateau as the research object, systematically exploring the carbon sequestration effect and mechanism of Yudiba dams, and propose an estimation method for their carbon sequestration capacity. The results show that Yudiba dams effectively protect soil and carbon, mitigate erosion and carbon emission, and promote vegetation and carbon sequestration. In the past 50 years, the carbon conservation, carbon emission reduction, and carbon sequestration capacity of Yudiba dams on the Chinese Loess Plateau are 2.16×10⁷, 4.33×10⁶~8.66×10⁶ and 6.84×10⁵ t C, respectively, which can enhance the carbon neutralization capacity of the ecosystem and reduce the carbon peak value. Yudiba dams and other significant soil and water conservation measures have demonstrated a variety of positive ecological restoration benefits, such as soil conservation, erosion reduction, and vegetation restoration, which fully promote the comprehensive role of carbon sequestration in carbon conservation, carbon emission reduction, and carbon sequestration increase. The implementation of soil and water conservation that focus on enhancing carbon sequestration not only reinforces the significance of terrestrial ecosystems in carbon sequestration, but also leads to a continual improvement of the carbon sequestration potential of terrestrial ecosystems, and plays a significant role in achieving carbon emission peak and carbon neutrality within the sphere of soil and water conservation.

Abstract:Glyphosate herbicides are essential materials in agricultural production, but excessive use can lead to a large amount of glyphosate and its derivatives remaining in soil, posing a threat to the ecological environment. By systematically elaborating the migration and transformation process of glyphosate in the environment, as well as its effects on soil organisms and environmental quality, the toxic effects of glyphosate on soil earthworms and microbial communities, the synergistic effects of glyphosate with other soil pollutants, and the changes in soil carbon, nitrogen, and phosphorus biogeochemical cycles driven by glyphosate were emphatically analyzed. At the same time, the deficiencies of the current research were pointed out, and the focus of the next research was put forward: (1) Strengthen the study on the degradation mechanisms and influencing factors of glyphosate, and screen for more efficient degrading microbial strains to improve the degradation efficiency of glyphosate and the ability to remediate glyphosate-contaminated environments. (2) To carry out regular monitoring and risk assessment of glyphosate in agricultural environments, map out the migration pathways of glyphosate in karst areas, explore the adsorption and removal ability of glyphosate in karst geology, so as to better evaluate the carbon sequestration stability of karst geology and the safety of aquatic ecosystems. (3) By using enzyme stoichiometry and other research methods, the conversion rate, flux, and coupling relationship between glyphosate and microbial metabolism, nutritional requirements, and environmental effects in the soil can be explored.

Abstract:Microaggregates are the basic unit of soil aggregate structure and have stronger stability than large aggregates. Their formation and stability play a decisive role in the long-term sequestration of soil organic carbon. Current studies on the formation and stability of microaggregates mainly focus on agricultural soils. Studies on soil aggregate stability, organic carbon distribution and microbial community characteristics after vegetation restoration in red eroded soil are also mainly concentrated on macroaggregates. However, the dynamic changes and their main influencing factors of soil microaggregates remain unclear, and the internal mechanism is still lack of understanding. In this paper, the formation process and stability of soil microaggregates were summarized, and the effects of litter, roots and mycorrhizal on the formation and stability of soil microaggregates were reviewed. It was expounded that microbial community, chemical combined organic carbon and organic carbon structure in soil microaggregates were important mechanisms for soil organic carbon stability, and the research direction of microaggregates in the later stage was put forward, in order to reveal the biochemical mechanism of the formation and stability of microaggregate in the forest restoration process of red eroded soil, and to provide a reference for further clarifying the coupling effect of organic matter, soil aggregate structure microbe and chemistry, and the mechanism of forest soil carbon sequestration.

Abstract:Slope and crop growth period are the key factors affecting the soil infiltration performance of sloping farmland, and crop growth can result in soil characteristics and root changes, which further affect the slope infiltration process. Through artificial simulated rainfall experiments, the slopes (3°, 5°, 10° and 15°) and 2 rainfall intensities (40 and 80 mm/h) of four slope cultivated land were designed, and the experiments were carried out in four growth stages of millet (early jointing period, middle jointing period, early heading period, early pustulation period) to explore the influence mechanism of slope and growth period on soil infiltration characteristics of millet slope farmland, and combined with the infiltration model (Horton, Kostiakov and Philip models) to evaluate the applicability of soil moisture infiltration process in cultivated land of millet slope. The results showed that: (1) The soil infiltration capacity decreased with the increase of slope, and compared with the slope of 3°, the stable infiltration rate, average infiltration rate and cumulative infiltration rate of the soil in farmland of 15° slope decreased by 30.76%~52.38%, 21.28%~37.50% and 22.51%~43.55%, respectively. (2) With the extension of millet growth period, soil infiltration capacity increased significantly, and compared with the early jointing stage, the stable infiltration rate, average infiltration rate and cumulative infiltration amount of soil in the early filling stage increased by 23.81%~80.00%, 20.83%~40.00% and 17.84%~54.10%, respectively, showing that the early jointing period < the middle jointing period < the early heading period < the early pustulation period. (3) By fitting the measured values of infiltration rate, the Horton model could best fit the soil infiltration process of slope farmland, and the fitting parameters of the model had physical significance. The research results can provide a theoretical basis for increasing rainfall infiltration, improving water use efficiency and reducing water and soil loss in sloping farmland.

Abstract:Through in situ observation experiment in the field micro-plots, the 34 erosive rainfall patterns from 2017—2021 were classified based on the concentrated periods of rainfall during the rainfall process, and the effects of rainfall pattern variation on the interrill erosion on loess slopes and slope effects were systematically analyzed. The results showed that the advanced rainfall pattern was dominant, accounting for 52% of the total rainfall, while the intermediate rainfall pattern and delayed rainfall pattern each accounted for 24%. The contribution of intermediate rainfall pattern to total runoff yield (25.56%±3.83%) was significantly lower than that of the advanced rainfall pattern (36.70%±2.07%) and delayed rainfall pattern (37.74%±4.01%) (p<0.05). The average runoff yield of different rainfall patterns was in the order of delayed rainfall pattern > intermediate rainfall pattern > the advanced rainfall pattern, and the delayed rainfall pattern and intermediate rainfall pattern was significantly higher than that of advanced rainfall pattern. The average sediment yield of different rainfall patterns was in the order of delayed rainfall pattern > advanced rainfall pattern > intermediate rainfall pattern. The rainfall of the delayed rainfall pattern was significantly higher than that of the intermediate rainfall pattern (p<0.05). The variation of slope effect of rainfall pattern on the effect of interrill erosion is not obvious, but with the increase of slope, the average runoff and sediment yield of delayed rainfall pattern were larger than that of advanced and intermediate rainfall pattern, indicating that the sediment yield of delayed rainfall pattern was relatively sensitive to the variation of slope. In the nonlinear fitting models of runoff, slope and rainfall parameter combination and sediment yield, the equation decision coefficients were delayed rainfall pattern (0.939~0.942) > the intermediate rainfall pattern (0.776~0.845) > the advanced rainfall pattern (0.220~0.537), indicating that the classification of rainfall pattern could improve model simulation accuracy.

Abstract:To compare the effects of single urea and urea combined with slow-release fertilizer application on runoff nitrogen loss, soil nutrients and growth of silage forage maize in slope arable land of Yunnan Province. In the runoff trough experiment under natural rainfall, three treatments of single urea (CK), urea supplemented with the nitrification inhibitor Instant Nortech ^®21 with 40% N replacement + 60% common urea (Treatment I) and polyglutamate Plus 3 with 40% N replacement + 60% common urea (Treatment Ⅱ) were set up under iso-nitrogen conditions according to conventional fertilizer application rates in Yunnan. The results showed that the highest reductions of total N, ammonium N and nitrate N loss concentrations were 2.59, 1.60, 1.42 mg/L and 1.61, 1.38, 1.25 mg/L for treatments I and Ⅱ, respectively, when compared with CK treatment during the fertility period. Compared to CK, the cumulative losses of total nitrogen, ammonium nitrogen and nitrate nitrogen were reduced by 18.56%, 16.19%, 24.31% and 10.75%, 8.73% and 17.08% for treatments I and Ⅱ, respectively. During the growth period of silage maize, the combined application of slow release fertilizer treatment significantly increased the ammonium N content by 13.94%~45.04% and 9.63%~22.39%, significantly reduced the nitrate N content by 3.70% ~29.91% and 8.61%~12.55%, and significantly increased the soil microbial biomass N content by 22.13%~31.76% and 11.80%~22.81%. Urea combined with slow-release fertilizer could also significantly increase the silage yield and plant N uptake, and improve the quality traits of silage maize by significantly increasing the crude protein and crude fat contents and reducing the crude ash and detergent fibre contents of the plant. Correlation analysis showed that runoff N loss was negatively correlated with soil N content, silage maize yield and plant N uptake, soil N was positively correlated with both yield and plant N uptake, and yield was significantly positively correlated with plant N uptake. In conclusion, compared with single urea, urea combined with slow-release nitrogen fertilizer could slow down the nitrification process of soil nitrogen, significantly enhance the nitrogen fixing ability of soil, maintainthe high nitrogen level of soil, and thus improve the yield and quality of silage maize, providing a scientific and theoretical basis for the fertilization of silage maize in red soil slope arable land.

Abstract:Identifying the effects of soil erosion-deposition on soil nutrients and enzyme activities in agricultural watersheds can provide an important scientific basis for soil erosion evaluation. Binzhou River Basin, a typical thin-layer Mollisol area, was selected as the study area, and two representative slopes were selected in the upstream, midstream and downstream of the basin. ¹³⁷Cs tracer technique was used to estimate soil erosion-deposition rates and impacts of soil erosion-deposition on soil nutrients (organic matter, total nitrogen and available phosphorus) and soil enzyme activities (invertase, urease and alkaline phosphatase) at both watershed and sloping scales were analyzed. The results showed as follows: (1) The soil erosion rates were the highest in the upstream of the Binzhou River Basin, which were 1.9 and 11.2 times of those in the midstream and downstream, respectively; at the sloping scale, the soil erosion rates were the highest in the middle slope locations, which were 1.3~2.6 and 2.8~12.2 times of those in the upper and lower slope locations, respectively. (2) At the watershed scale, the spatial distribution of soil organic matter and soil erosion rates showed an opposite trend and the contents of total nitrogen and available phosphorus in the downstream were both greater than those in the midstream; on the sloping scale, the contents of soil organic matter and available phosphorus as well as the activities of soil invertase, urease and alkaline phosphatase in the lower slope locations were all greater than those in the middle slope locations, indicating that soil erosion in farmland declined soil nutrient contents and enzyme activities. (3) The soil deposition rates in the deposition areas of the watershed had significant impacts on the contents of soil organic matter and available phosphorus as well as the activities of soil urease and alkaline phosphatase. (4) The contents of soil organic matter and available phosphorus had significant impacts on the activities of urease and alkaline phosphatase, indicating that the redistribution of soil nutrients caused by soil erosion-deposition was an important reason for the spatial differentiation of soil enzyme activities.

Abstract:The topographic critical model for the occurrence of erosion at gully head can effectively predict the conditions for the formation of erosion gullies, the depression formed by shallow landslide instability is also one of the ways of gully head formation. In order to explore the characteristics of the critical initiation model of shallow landslides, the rainfall-type shallow landslides in the Xiaolong mountain area of Tianshui City, Gansu Province was taken as the research project. We used area-slope relationship to construct the shallow landslide critical initiation model, and compared with the critical initiation model for typical erosion gully ephemeral gullies and permanent gullies located in the Loess Plateau. The effects of land use type, vegetation type and soil texture on the critical initiation model were also discussed. The results showed that: (1) The critical initiating model of shallow landslides was S=3.50A_s^-0.34, and its topographic threshold was 3.50, which was larger than ephemenral gullies (0.96) and permanent gullies (1.54) in the Loess Plateau. Shallow landslides in the study area generally occurred on steep slope area with thin soil layer, and the average slope (S=1.26 m/m) was higher than ephemeral gullies (S=0.35 m/m) and permanent gullies(S=0.46 m/m). The unit upslope drainage area (A=89.08 m²/m) was less than the ephemeral gullies(A=920.93 m²/m) and permanent gullies (A=1 129.82 m²/m). (2) The product of upslope drainage area and the square of the critical slope gradient (AS²) was used as an important energy index for gully formation. The AS² value of shallow landslide in the study area ranged from 269.1 to 5 703.2 m², with an average value of 1 772.97 m². The AS² value of ephemeral gullies in the Loess Plateau ranged from 4.74 to 892.66 m², and that of permanent gullies in 41 to 814 m². In terms of starting energy value, ephemeral gullies < permcnent gullies < shallow landslides. (3) Land-use type, vegetation type and soil texture had an effect on the initiation of shallow landslide by affecting the resistance, permeability and clay content of soil. Among different land use modes, agricultural land was the most vulnerable to erosion, followed by forest land. The erosion resistance of landslides near Pinus tabulaeformis forest was higher than those in Larix kaempferi forest. The results of this study provide a theoretical basis for exploring the initiation conditions of shallow landslides.

Abstract:In order to explore the characteristics of runoff and sediment of different rainfall types on bare slope in the red soil region, the data of 388 rainfall-runoff-soil erosion observations were collected from January 2013 to December 2020 in the red soil bare slope runoff community of Soil and Water Conservation Center of Changting Country, and rainfall events were divided by K-means clustering method into 4 types for analyzing. The results indicated that: (1) There were 3 main rainfall types in the study area, including A (short duration, large rainfall intensity, small rainfall amount, and low frequency), B (long duration, light rainfall intensity, large rainfall amount, and medium frequency) and C (medium duration, light rainfall intensity, small rainfall amount, and high frequency). Types B and C were the main sources of runoff and sediment yield on bare slope, which contributed more than 85% of runoff and soil erosion; (2) Runoff depth and soil erosion of single-rainfall were linearly positively correlated with the rainfall amount (P), maximal rainfall intensity of 30 min (I₃₀) and rainfall kinetic energy (E), and presented a power function relationship with rainfall erosivity (EI₃₀). However, the total interpretation of rainfall characteristics on runoff and sediment was less than 65%, and decreased with the increase of rainfall duration; (3) There were 3 kinds of constraints between rainfall characteristics and runoff and sediment of bare slope, and the constraint line showed the influence of rainfall characteristics on the potential maximum runoff depth and soil erosion. The potential maximum runoff depth of single-rainfall was mainly determined by P and E, and the potential maximum soil erosion of single-rainfall had a ceiling of 800~900 t/hm². The runoff and soil erosion characteristics of bare slope in the red soil region were analyzed from three aspects: single factor influences, comprehensive influences and constraint effects of rainfall characteristics, which provided a data basis for the soil erosion control in the red soil region.

Abstract:To explore the distribution of gravitational erosion and its environmental conditions under extreme rainstorm. The extremely rainstorm event caused by Typhoon "Lekima" in 2019 was chosen as the target. Using UAV aerial imagery and remote sensing interpretation, the quantities, spatial distribution characteristic and influencing factors of various gravitational erosion in Zengjiagou small watershed of Linqu County, Shandong Province, where the center of extremely rainstorm was located. The results showed that: (1) There were a total of 70 gravitational erosions in Zengjiagou. Among which, the predominant type was Landslide (49 sites), followed by debris flow (14 sites) and collapse (7 sites). (2) Gravitational erosion area and erosion amount were positively correlated with slope variation, slope, slope position, elevation, slope direction and slope direction variation, respectively, and negatively correlated with distance to terrace, distance to road and land use type. (3) Slope was the most important factor affecting gravitational erosion, which was prone to occur on slopes ranging from 30° to 50°. (4) Gravitational erosion had been profoundly influenced by human activities. Under heavy rainstorm, severe gravity erosion mostly occurred in terraced field and road slopes. The gravitational erosion prevention and control should be focused on strengthening the protection on both sides of the slope road, terraced field, and steep slopes with slope >30°. The results can provide scientific basis for coping with and preventing gravitational erosion disasters.

Abstract:Investigating the relationship between soil-water characteristic curve (SWCC) and shear strength of root-soil composites is expected to provide a scientific basis for revealing the strengthening mechanism of purple-soiled root-soil composites and maintaining the stability of soil bunds. The root-soil composites of herbaceous plants on the soil bunds of typical purple-soiled sloping farmlands in the Three Gorges Reservoir region was selected as the research object, and the effect of matrix suction on the shear strength of root-soil composites was constructed by using Hyprop2 soil moisture characteristic curve measuring instrument, filter paper method combined with the direct shear test. Major findings were: (1) SWCC of the root-soil composites could be divided into boundary effect zone, transition zone, and unsaturated residual zone, and the F-X model fitted best among the three commonly used models (B-C, VG, F-X). The saturated water content, air intake suction, residual water content, and suction at the same volumetric water content of the root-soil composites were all higher than those of the plain soil. (2) The cohesion of the root-soil composites first increased and then decreased with the decreasing volumetric moisture content, and the maximum cohesion of 51.25 kPa in the test range occurred at a volumetric moisture content of about 23%. At the same time, the angle of internal friction increased linearly. The cohesion of root-soil composites increased by 50% compared with plain soil at the same volumetric water content, and the internal friction angle was not greatly enhanced. (3) The enhancement effect of matrix suction on the shear strength of root-soil composites and its parameters had a stage-specific characteristic, and the critical suction value of each stage was consistent with the SWCC. The shear strength of soil in the transition zone(where the matrix suction was 3~500 kPa) was most obviously improved. After entering the unsaturated residual zone (matrix suction was greater than 500 kPa), the shear strength of soil increased at a slower rate due to the decrease of cohesion. In addition, the shear strength of the root-soil composites raised with increasing matrix suction to a greater extent than that of the plain soil. Establishing the relationship between SWCC and shear strength of the root-soil composites of purple-soiled bunds could estimate the shear strength of soil bunds under actual working conditions, which provides an important theoretical support for the construction, maintenance and management of slope cultivated land and the erosion control of slope cultivated land.

Abstract:In order to understand the impact of rock strata dip on soil infiltration characteristics in karst trough valley area, taking the dip/anti-dip slope of Qingmuguan karst trough valley area in Chongqing as the research object, the differences of soil infiltration capacity of five typical land use patterns, namely abandoned land (AL), pepper land (PL), corn land (CL), forest land (FL), grassland (GL) in dip/anti-dip slope were analyzed, and the influence of soil physical properties on soil infiltration capacity was discussed. The results showed that: (1) There were significant differences in >0.25 mm water-stable aggregate content, capillary water holding capacity, clay and silt content between the dip and anti-dip slope (p<0.05). In terms of >0.25 mm water-stable aggregate content and capillary water holding capacity, the greatest differences were found between the dip and anti-dip slope of PL and FL, respectively, and in terms of clay and silt content, the greatest differences were found between the dip and anti-dip slope of CL, and both were anti-dip slope > dip slope. (2) Except for the soil infiltration capacity of FL, the soil infiltration capacity of the dip slope was lower than that of the anti-dip slope, and the soil infiltration capacity of the other four land use patterns was higher than that of the anti-dip slope. (3) Soil infiltration characteristics showed highly significant negative correlation with bulk density on dip and anti-dip slope (p<0.01), and had significantly positive correlation with total porosity, non-capillary porosity, >5 mm water-stable aggregate content and saturated water holding capacity in the dip slope (p<0.01), and had significantly positive correlation with non-capillary porosity, saturated water holding capacity and silt content in the anti-dip slope (p<0.01). The multiple stepwise regression analysis and path analysis revealed that the primary decision factor for the soil infiltration capacity on dip and anti-dip slope was both the bulk density, followed by >5 mm water-stable aggregate content and silt content, respectively. (4) Compared with the four fitting models of soil infiltration process, Philip model had the best fitting effect on the soil infiltration process of the dip and anti-dip slope. The research results can provide data support for soil erosion control and vegetation restoration in different rock strata dips in karst trough valley area.

Abstract:The implementation of Grain to Green Program (GTGP) significantly affects the physicochemical properties of the soil on the Loess Plateau, which may influence the soil erodibility. However, the response of soil erodibility to GTGP and its regional characteristics across the Loess Plateau were still unclear. Accordingly, with cultivated land as the control, the soil physicochemical properties of three types of reclaimed farmland (forest, shrub land and grassland) in four rainfall zones (200~300, 300~400, 400~500, >500 mm) on the Loess Plateau were studied through field investigation and laboratory analysis. The EPIC model was used to estimate soil erodibility and analyze the effects of different conversion types on soil erodibility in different areas of the Loess Plateau. The results showed that in the whole Loess Plateau, the soil organic carbon content of 0—20 cm of GTGP increased by 1.22~2.83 g/kg, and the soil organic carbon content of forest, shrub, and grassland increased by 1.70, 1.72 and 2.72 g/kg, respectively. In the Loess Plateau, there were significant differences in the clay particles between grassland and farmland within the rainfall zone of 200~300 mm, but there were no significant differences in the clay particles, silt particles and sand particles among different types of converted farmland in the rainfall zone of 300~400, 400~500 and >500 mm. Soil erodibility before and after GTGP on the Loess Plateau showed a decreasing trend from 0.012 4 to 0.011 5 (t·hm²·h)/(hm²·MJ·mm), respectively, but the difference was not significant, and there was no significant difference in soil erodibility among forest, shrub, grassland and cultivated land. Overall, the GTGP greatly enhanced the soil organic carbon content, but had no effect on soil particle composition and soil erodibility. The results can provide a scientific basis for predicting soil erosion on the Loess Plateau after GTGP.

Abstract:In order to reveal the characteristics of runoff and sediment and nutrient loss path of on steep slope caused by platform inflow of engineering soil deposits, a laboratory scouring experiment, designed to have three scouring inflow rates (1.7, 2.3, 2.9 L/min) and three slope gradients (25°, 30°, 35°), was conducted on disposal sites in opencast coal mine to research the processes of surface runoff, interflow and sediment and measure the concentration of nitrogen and phosphorus in these for calculating the nutrient loss and contribution. The results indicated as follows: Surface runoff was the main type of runoff generation in earth-covered engineering slope in eastern Inner Mongolia. With the increase of slope gradient and scouring inflow rates, surface runoff increased but interflow decreased. The sediment yield rose first and then decreased with the increase of slope gradient, and the critical slope gradient was about 30°. The loss concentrations of ammonium nitrogen and phosphate in surface runoff were higher than those in interflow, and the concentrations of nitrate nitrogen were lower when the scouring flow was larger (2.9 L/min). The loss of phosphate in runoff and nitrogen and phosphorus in eroded sediment firstly increased and then decreased with the increase of slope gradient. The loss of nitrogen and phosphorus from surface runoff and sediment increased with the increase of scouring inflow rates. The amount of nutrient loss in runoff was nitrate nitrogen > ammonium nitrogen > phosphate. Erosion sediment was always the main export route of phosphate, accounting for more than 59.69% of the total loss. The maximum nitrogen loss occurred only when the slope gradient was 30°, while on the 25°and 35°slope, surface runoff was the main route of nitrogen loss, at low inflow rates (1.7, 2.3 L/min), the nitrogen output from interflow was the second.

Abstract:In order to reveal the influence of hedgerow on the erosion distribution of sloping land, the slope was divided into five sections (from top to bottom) by using rare earth element oxides, and the simulated rainfall experiments were conducted at one slope gradient (15°), three rainfall intensities (60, 90 and 120 mm/h) and three slope conditions (CK-control slope, P-hedgerow and R-only hedgerow root). The results showed that with the increase of rainfall intensity, the erosion rate and erosion amount of the tracer slope sections in each slope condition increased, and the overall trend was CK>R>P. The hedgerow could significantly reduce the erosion rate and its erosion amount in all parts of the slope, and the erosion sand production was mainly concentrated in the three tracer areas of Ce, La and Yb in the middle of the slope. Compared with CK slope condition, the average contribution rate of Sm and Ce tracer slope sections to total erosion decreased by 77.15%, 90.38% and 30.01%, 28.35% under R and P slope conditions, respectively, while the average contribution rate of Yb, La and Eu tracer slope sections to total erosion increased by 54.34%, 35.39% and 12.39%, 40.58% and 101.45%, 91.31%, respectively. The results indicated that hedgerow caused a decrease in erosion contribution from the lower part of the slope and an increase in erosion contribution from the middle and upper parts of the slope, which had a significant effect on the spatial distribution of slope erosion by shifting the overall erosion site upward.

Abstract:In order to explore the difference of loess and red soil erosion affected by rainfall intensity and slope and its relationship with soil properties, various physical and chemical properties of loess and red soil were measured and analyzed, and four rainfall events were carried out on the two soils under two slope gradients (15°, 20°) and two rainfall intensity (60, 90 mm/h). The results showed that: (1) Compared with red soil, soil particles of loess were finer, and the differences in capillary porosity, saturated water content and field water holding capacity between loess and red soil were within 3% to 6%. There was no significant difference in the aggregates of each size of dry sieving, but the difference between the aggregates of the two was large after the destruction of wet sieving. The relative mechanical fragmentation index (RMI) of red soil was lower than that of loess. The organic matter content, cation exchange capacity and complex oxide content of loess were all higher than that of red soil, while amorphous oxide and free oxide were lower than that of red soil. (2) Under the same rainfall intensity and slope conditions, the runoff generation time of loess was shorter than red soil, after the start of runoff, red soil reached a stable runoff rate before loess. Under different rain intensity and slope conditions, the stable runoff rate of red soil ranged from 30 to 120 mL/s, while that of loess was between 100 to 220 mL/s. And within this range of slope and rain intensity, the runoff rate of red soil varied in distinct layers, while that of loess was staggered and complex. (3) The sediment yield and runoff sand content rate of red soil were both low, and the maximum sediment yield rate usually occurred within a few minutes of runoff. The sand yield rate of loess was similar to the runoff rate, it increased rapidly in the early stage of runoff, and then began to fluctuate after 10 minutes. When it entered the stage of relatively stable sediment yield, the sand yield rate and runoff sediment rate changed complicated with rainfall intensity and slope. (4) Different physical and chemical properties of soil were the internal factors affecting slope erosion. Compared with loess, red soil had better infiltration capacity and stronger resistance to runoff shear and denudation. The erosion degree of red soil under the same rainfall intensity and slope condition was much lower than that of loess, and the regularity was more obvious.

Abstract:In order to explore the impacts of different management measures on soil organic carbon migration in newly developed Citrus reticulate-based orchards in southern red soil regions, the effects of six management measures on soil erosion and soil organic carbon migration in orchards under the background of natural rainfall were monitored and evaluated, including clear tillage (CB), straw mulch (CS), radish peanut rotation intercropping (CRP), Trifolium strip mulch (CCS), Trifolium mulch (CC) and Bryophyta mulch (CT) in the young Citrus reticulate-based orchards (two years old) located in red soil slope land. Our results showed that: (1) The runoff production of 6 management measures CB, CS, CRP, CCS, CC and CT were 7.88, 4.45, 4.64, 3.24, 3.25 and 4.70 m³, respectively. Compared with CB, the runoff reduction benefits under CS, CRP, CCS, CC and CT measures were 43.51%,41.10%,58.94%,58.82% and 40.38%, respectively; the sediment production was 71.35, 21.27, 31.03, 14.24, 14.18 and 35.05 kg, and the sediment yield was reduced by 70.18%, 56.51%, 80.04%, 80.13% and 50.87%, respectively. (2) The loss intensity of sediment organic carbon was CB (20.75 g/m²), CS (4.78 g/m²), CRP (8.68 g/m²), CCS (3.52 g/m²), CC (3.38 g/m²) and CT (9.94 g/m²), respectively, which decreased by 76.94%, 58.16%, 83.01%, 83.71% and 52.11% compared with CB. (3) The loss intensity of sediment organic carbon and dissolved organic carbon was positively correlated with runoff production (R²=0.412 and 0.419, respectively). Surface management measures affected the migration of soil organic carbon in newly developed orchards in red soil slope mainly by regulating surface runoff generation. In conclusion, both the Trifolium strip mulch (CCS) and Trifolium mulch (CC) had obvious effects on inhibiting soil erosion and soil organic carbon migration loss. This study can provide a scientific basis for controlling soil erosion and soil organic carbon migration loss in newly developed orchards in red soil region of Southern China.

Abstract:As a key soil erosion prevention reserve, the bare slope of the southern foothills of Dabie Mountain has serious soil erosion. In order to explore the response of runoff and sediment to rainfall on typical bare land slopes, the rainfall-runoff-sediment process of bare land runoff plots was monitored by automatic runoff and sediment monitoring equipment. Based on the annual erosive rainfall data in 2020, the rainfall patterns were divided according to the rainfall peak time series. The characteristics of cumulative runoff and sediment yield of the four rainfall patterns and the runoff and sediment characteristics of individual rainfall were analyzed, and the optimal function model was established. The results showed that: (1) The maximum 30 min rainfall intensity was an important factor affecting the sediment volume and runoff coefficient of rainfall events in the southern foot of Dabie Mountains. There was a positive correlation between the rainfall and sediment load in the first 48 hours of initial and middle concentrated rainfall events. (2) There were significant differences in the process of runoff and sediment yield under different rainfall patterns, but the difference of runoff and sediment indexes was not significant. The optimal model of cumulative runoff and sediment yield under different rainfall patterns was Logistic model. (3) Under different rainfall patterns, the variation trend and peak value occurrence rule of rainfall intensity, runoff rate and sediment yield rate were consistent, and the process of sediment yield lagged behind the process of rainfall intensity. The lag of sediment yield mostly occurred in the early stage of concentrated rainfall, and the lag of runoff mostly occurred in the middle and late stage of concentrated rainfall. The results can reveal the relationship between rainfall-runoff-sediment yield, which has certain scientific guiding significance for the prevention and control of soil and water loss on the slope in this area.

Abstract:River runoff is an important form of water resources, and baseflow is a vital part of the runoff. It is of great significance to study the change of baseflow and its influencing factors to master the change of water resources in the basin. Based on the daily flow data of Qujiang Basin from 2007 to 2018, the applicability of nine different baseflow separation methods and the variation characteristics of baseflow were analyzed. The results showed that: (1) There were great differences among different methods, and the separation results of time step method and sliding minimum method were higher than others. The variance and coefficient of variation of F4 filtering method were 0.038 and 0.138, indicating that the separation of this method was more stable and less discrete, and had the best applicability in the Qujiang Basin. (2) The multi-year average baseflow index of the basin was 31.5%, and there were both summer and autumn flood seasons in the year, the multi-year average monthly precipitation, runoff and baseflow had the same variation trend, and the peak time of runoff and baseflow in the basin showed a lag compared with precipitation. (3) Wavelet coherence analysis showed that both precipitation and baseflow series in the basin had a 10~14 months variation cycle and changed in the same direction, the baseflow lagged behind the precipitation series in time and frequency, and the baseflow had a time delay in response to climate change. When the baseflow lagged 8~10 months behind the climatic index of the same period, the correlation between the two was significantly increased. The research results are helpful to improve the understanding of the change of baseflow in the Qujiang basin and provide a scientific basis for the management and regulation of water resources in the basin.

Abstract:Exploring the spatial and temporal changes of vegetation NDVI in Huangshui watershed and its driving factors will be beneficial to regional ecological environment restoration and regional sustainable development. Based on multi-source remote sensing data and socio-economic data, using the trend analysis method and Pearson correlation analysis method to explore the spatial and temporal changes characteristics of vegetation NDVI in Huangshui watershed from 2000 to 2020, and with the help of geographic detector to analyze the influence of natural and anthropogenic driving factors on the spatial variation of vegetation in the basin. The results showed that: (1) From 2000 to 2020, vegetation NDVI value of the watershed presented an overall upward trend, with an average growth rate of 0.003 8/a, among which Huangshui coastal and downstream parts of the most obvious rising trend, while there was an obvious downward trend in new towns and the "water diversion tunnel from Datong river into Huangshui river" project area. (2) In the whole watershed, temperature and elevation were the main factors affecting the spatial variation of vegetation NDVI; elevation, soil and vegetation type were the main factors affecting the spatial changes of vegetation NDVI. (3) The explanatory power of the interaction between the driving factors were higher than that of the single factor, showing a non-linear and two-factor enhancement, temperature and landscape interaction had the highest explanatory power, reaching 71.6%, and explanatory power of the spatial variation of vegetation NDVI was the strongest. (4) The spatial variation and change of vegetation NDVI in the watershed were influenced by both natural and human factors, and the natural factors played a leading role. With the significant improvement of people's awareness of environmental protection and the gradual implementation of regional ecological projects, the vegetation cover of the watershed is turning better.

Abstract:Forest carbon pool plays an important role in the global carbon cycle. In order to understand the temporal and spatial dynamics of carbon density of forest vegetation and its influencing factors in Zhongtiao Mountains region of Shanxi Province, we quantitatively studied the carbon density of forest vegetation and the contribution of each driving factor to the spatial distribution of carbon density by using stochastic forest and structural equation model based on the data of national forest resources continuous inventory from 2005 to 2015. The results showed that: (1) The carbon density and carbon storage of forest vegetation in Zhongtiao Mountains in 2005, 2010 and 2015 were 24.87, 26.56, 31.42 Mg C/hm² and 15.89, 16.00, 20.15 Tg C, respectively, which showed a continuous increasing trend with an average annual growth rate of 2.63% and 2.68%, respectively. (2) The spatial distribution characteristics of vegetation carbon density were as follows: high (> 100 Mg C/hm²) and medium-high (60~100 Mg C/hm²) carbon density plots were mainly distributed in the central and southwest of Zhongtiao Mountains, while low carbon density plots (< 60 Mg C/hm²) were mainly distributed in the northeast. (3) Stand age and average annual rainfall were two important driving factors affecting the spatial pattern of vegetation carbon density in the study area. The direct positive effect of stand age on carbon density was the most significant, and average annual rainfall affected the spatial distribution pattern of carbon density through an indirect effect on stand factors.

Abstract:Based on the eco-hydrological optimality theory of Eagleson, from the regional scale, a variety of environmental variables were integrated to simulate the optimal vegetation coverage under the eco-hydrological balance in Ningxia, and then determine the vegetation carrying capacity and study the optimal coverage of different vegetation types under the premise of not consumption of soil moisture. The results showed that: (1) During the study period (2000—2019), the correlation between the balanced vegetation coverage and the actual vegetation coverage based on Eagleson’s ecological optimality theory was 0.86, indicating that the model was well simulated. Excluding farmland, the average annual vegetation coverage in Ningxia was 0.048~0.984, and the simulated balanced vegetation coverage was 0.153~0.840. The vegetation coverage had a good spatial consistency, and the southern region was higher, showing a trend of decreasing gradually from south to north. (2) From the perspective of spatial distribution of vegetation carrying capacity, the difference between actual vegetation coverage and simulated equilibrium vegetation coverage in most regions was less than 0.05, indicating that they were not in overload state, and the vegetation overload area was mainly located in Jingyuan County. (3) The optimal coverage of simulated vegetation for the three land use types of grassland, shrubland and woodland decreased gradually from south to north. From the perennial average, the optimal coverage of simulated vegetation was 0.223~0.841 for grassland, 0.186~0.659 for shrub land, and 0.153~0.635 for woodland. The research results are helpful to scientifically guide the local ecological environment construction and provide theoretical support for the ecological restoration construction in similar areas.

Abstract:Exploring the spatial and temporal changes of regional aquatic ecosystem services and their relationship with land use is conducive to the protection of regional aquatic ecological environment and the rational development and utilization of land resources, and helps decision makers to improve the regional ecosystem service capabilities and balance the regional ecological functions and agricultural production functions through reasonable land use methods. Longxi River Basin (LRB) in Chongqing, an important ecological barrier in the upper reaches of the Yangtze River, was selected as the research object. The InVEST model was used to study the temporal and spatial variation characteristics of water ecosystem services such as water production, water purification and soil conservation services in the Longxi River Basin in recent 20 years and their effects on different land use types. The results showed that: (1) In the past 20 years, the water ecosystem services of the LRB in Chongqing were generally enhanced and improved, but there were some spatial differences. Although the water yield and water source conservation services of the whole basin had little difference, the forest-intensive area in basin of the water purification services was stronger than that of farm town and industrial agglomeration area. The soil conservation services in basin of water area, construction land and forest land in the central and north-south was stronger than the sloping land on the east and west sides of the basin. (2) Different land use types had different contributions to water ecosystem services. The order of the water yield services from strong to weak as follows: cultivated land > construction land > forest land > grassland > water area. The water conservation capacity from strong to weak as follows: cultivated land > grassland > water area > forest land > construction land. The water purification services from strong to weak as follows: forest land > grassland > construction land > cultivated land > water area. Soil conservation services from strong to weak as follows: water area > construction land > cultivated land > forest land > grassland. (3) In order to balance the supply and regulation services, it was appropriate to take township as a unit to divide the Longxi River Basin into ecological restoration area, agricultural production area and urban development area, and take corresponding ecological measures for each partition.

Abstract:Identifying the migration and evolution of Production-Living-Ecological space(PLE space) and understanding the changes of spatial characteristics triggered by it have a profound influence on optimizing the layout of national land space and improving utilization level. Taking the urban agglomeration in the upper reaches of the Yellow River basin as the research object, based on the transfer matrix, the spatio-temporal evolution rule of the PLE space in the study area from 2000 to 2020 was analyzed. On this basis, by means of the strength analysis model, the change stability brought by the spatial evolution was discussed and quantified, from the dual perspective of the primary and secondary classification of the PLE space, respectively. The results revealed that: (1) The spatial change of PLE space in the study area was active during the past 20 years, but with a decreasing tendency in the amount and the scale, which was also concentrated upon the Hubao Eryu urban agglomeration and the Ningxia urban agglomeration along the Yellow city cluster, with the distribution high in the east and low in the west. Nevertheless, the overall pattern was still dominated by the ecological space and the production and living space were followed. (2) During the past 20 years, the spatial change trend of PLE space in the basin was first strong and then weak, which was unstable as a whole. The increase of production and living space was active and stable, while the decrease tended to be gentle. The increase of ecological space tended to be gentle, but the decrease tended to be active, and the stress of the first two groups on the ecological space tended to be normal. At the same time, PLE space in the basin was frequently transferred to each other, and there were two stable systematic transformation modes of production-life, life-ecological. (3) The transformation of PLE space within the secondary classification level was the dominant reason for the change of production, living and ecological space, while the development of economic drive, the influence of urban attraction, as well as the guidance of macro policies were the internal mechanisms that caused the alternant change of PLE space in the basin. (4) The joint research framework of transfer matrix and the intensity analysis model would realize the integrated monitoring of change monitoring and the changes of the characteristics of the regional PLE space. The improvement of space utilization efficiency, regulation of urban scale, persistence of cultivated land protection, fulfillment of effective space exit mechanism, and giving play to the guiding role of macro policies on space transform will have positive impacts on the high-quality utilization of PLE space of the study area.

Abstract:To explore the land use characteristics and spatial and temporal changes of landslides in Tianshui City, Gansu Province, Qinzhou District and Maiji District were selected as the representatives of typical loess landslide areas, based on 12.5 m resolution ALOS DEM data and the global 30 m fine ground cover dynamic monitoring products from 1985 to 2020, using GIS spatial analysis, land use net change volume index, land use transfer matrix and land use contribution ratio to analyze the characteristic parameters, land use/cover types, land use transfer characteristics and driving factors of landslides. The results showed that: (1) A total of 469 landslide samples were identified in the study area, with the average elevation concentrated in 1 200~1 400 m and the average slope concentrated in 10°~15°, the average aspect was westward slope, the relative height difference between the front and back edges concentrated in 100~150 m, the landslide area concentrated in 1×10⁴~10×10⁴ m², and the sliding length concentrated in 200~400 m. (2) From 1985 to 2020, the landslides were the most frequent in rainfed croplands, followed by grasslands; the land use types during the period showed dynamic change characteristics, divided into a continuous phase change phase from 1985 to 2000 and a weak adjustment phase from 2000 to 2020; among them, the most drastic changes were observed from 1995 to 2000, mainly in the transformation of rainfed croplands to grasslands and forest lands. (3) The transformation of rainfed cropland area was the most in the past 35 years, with a cumulative total of 8.74 km², contributing 6.58 km² to grassland, 1.94 km² to closed deciduous broadleaved forest and 0.20 km² to impervious surfaces, while the remaining land use types account for a small proportion and weak transformation; the net land use changes of rainfed cropland, grassland, closed deciduous broadleaved forest and impervious surfaces were the largest. (4) The utilization of individual landslides was diversified year by year, and the increase of grasslands and closed deciduous broadleaves forests enhanced the vegetation cover of the area and reduced the possibility of recurrence of landslides. Land use types and spatial and temporal change patterns of landslides in Tianshui City provided scientific basis for the development, reuse and ecological restoration of disaster-damaged land in the region.

Abstract:Exploring the relationship between spatial distribution and environmental control characters of gully landforms and building accurate extraction model are of great significance for gully landforms extraction in large scale. Based on the artificial extraction of gully landform samples combing with Landsat8 OLI image data with different periods of and DEM data of a typical watershed on the Chinese loess plateau, the random forest model was established to determine the best period for gully landforms extraction and the best combination of gullying features. Then, combined with the optimal model parameters, results of random forest were compared with support vector machine and artificial neural network model to validate the model generalization ability. Our results showed that: (1) The best image period for gully extraction was in December, and the best combination feature set was Red, Blue, elevation (H), SWIR1, positive and negative terrain (PNT), Coastal, texture (GLCM4) and NIR; (2) The distribution of gully landforms in the testing area extracted by three methods had consistently spatial pattern. Based on qualitatively and quantitatively modelling performance, the random forest model presented the best extracting performance, with the average overall accuracy of 80.48%, which was higher by 4.00 percentage and 8.63 percentage compared with the support vector machine model and the artificial neural network model, respectively; (3) The gully landforms accounted for 56.91% of the total testing area and the distribution of gullies in testing area was gradually concentrated from northwest to southeast. The results show that the random forest model has the best comprehensive performance in the study of high-precision gully landforms identification on the Chinese Loess Plateau, and can be widely extended.

Abstract:Since the "two-carbon goal" was proposed, the research on the spatial-temporal variation characteristics of land use carbon emissions is of guiding significance for the formulation of carbon emission reduction policies. Based on FLUS and grey prediction model, land use carbon emissions in 2030 were predicted in Urumqi, and the spatial-temporal pattern of carbon emissions from 2000 to 2030 was simulated by combining with previous years. The results were as follows: (1) During the land use change in the study area from 2000 to 2020, the forest land, unused land, water area and construction land showed positive growth, while the arable land and grassland showed negative growth. The area of grassland and cultivated land was mainly transferred to unused land and construction land, and the area change of water area and woodland was relatively stable. (2) The total carbon emissions in the study area showed an increasing trend from 2000 to 2020, and construction land was the main determinant. The spatial distribution of carbon emissions in the study area showed an increasing trend from south to north, with the highest carbon emissions in Midong District and the lowest carbon emissions in Daban District. (3) In the calculation results of carbon emissions under different scenarios in 2030, the total carbon emissions under cultivated land protection scenario were the highest (27.736 7 million t), while the carbon emissions under ecological environment scenario were the lowest (27.671 5 million t). (4) From 2000 to 2030, most areas of the study area tended to be stable, with large aggregation and sporadic distribution of the changing areas. The increasing area of carbon emission was mainly distributed in the central area of the study area and Midong District in the north, while the decreasing area was mainly distributed in Urumqi County and Dabancheng District in the south. The area with the largest increase in carbon emission was in the cultivated land protection scenario, accounting for 25.4% of the study area. The area with the largest decrease in carbon emission was in the ecological environment scenario, accounting for 13.3% of the study area.

Abstract:In order to reveal the response characteristics of surface soil carbon (C) and nitrogen (N) components to long-term addition of N and aboveground litter treatment in semi-arid sandy grassland ecosystem, a long-term (9-year) N addition and litter treatment sample plot established by the National Field Scientific Observation and Research Station in the southwest of Horqin Sandy Land was taken as the platform. The surface soil environmental factors, ammonium nitrogen, nitrate nitrogen, total organic carbon (TOC) and different C and N components were measured and analyzed. The results showed that: (1) There was no interaction between surface soil biochemical factors and different C and N properties during 9 years of N addition and aboveground litter treatment. (2) The N addition treatment significantly reduced soil pH (p<0.01), significantly increased soil nitrate nitrogen content (p<0.05) by 37.57%, and the contents of dissolved organic nitrogen (DON) and labile organic nitrogen (LON) were significantly increased (p<0.01, p<0.05). (3) The treatment of aboveground litter removal significantly reduced the contents of TOC, intermediate organic carbon (IOC), microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) (p<0.05). (4) After 9 years of N addition and aboveground litter treatment, there was no close correlation between different C and N components and soil environmental factors in semi-arid sandy grassland. The above results showed that long-term addition of N and aboveground litter could change the contents of different C and N components in the surface soil, but did not significantly change the ratio of each C and N component. This study provides a reference for revealing the effects of long-term addition of N and aboveground litter treatment on soil C and N storage and predicting future soil biogeochemical element dynamics in sandy grassland in semi-arid region.

Abstract:The Yellow River Basin Economic Belt is an important economic corridor in the north of China. Scientific assessment of the performance level of the ecological environment of the Yellow River Basin Economic belt and improvement of the ecological and environmental quality of the nine provinces along the Yellow River Basin were one of the important measures to achieve the high-quality development of the Yellow River Basin economic belt. In this paper, ecological environment quality assessment, ecological efficiency assessment and other research methods were used to evaluate the assessment of ecological environment quality, ecological efficiency and green total factor productivity from 2012 to 2017. The results showed that the ecological environment performance level of the Yellow River Basin economic belt presented a trend of increasing from a low level. The nine provinces along the Yellow River had obvious differences in eco-environmental quality and eco-efficiency system layer, and the upstream region was the best. In the ecological efficiency system layer, the ecological efficiency in the middle and lower reaches was the best and stable. The research results proposed to accelerate the implementation of the Yellow River Strategy from the three aspects of ecosystem restoration function, industrial green development and the improvement of the top-level system design of ecological environment, so as to improve the ecological and environmental performance of the Yellow River Basin economic belt.

Abstract:As more and more nitrogen fractions are discharged into the atmosphere by human activities, the nitrogen content in the ecosystem gradually becomes saturated, and subtropical region has become one of the regions with the most serious nitrogen deposition in the world. Soil organic nitrogen (SON) fractions can directly reflect the response of soil nitrogen availability to nitrogen deposition. The effects of different nitrogen application levels on SON fractions were studied in a natural Castanopsis carlesii forest in the Castanopsis kawakamii Nature Reserve located in Sanming, Fujian Province. The results showed that: (1) SON content under high nitrogen treatment (1.23 g/kg) was significantly higher than that under control treatment (0.89 g/kg). The content of soil labile nitrogen fraction (LPⅠ-N + LPⅡ-N) in high nitrogen treatment (0.28 g/kg) was significantly higher than that in low nitrogen (0.24 g/kg) and control treatments (0.22 g/kg). Soil recalcitrant nitrogen (RP-N) contents in high nitrogen (0.94 g/kg) and low nitrogen (0.82 g/kg) treatments were significantly higher than that in control (0.68 g/kg). (2) Compared with control and low nitrogen treatment, high nitrogen treatment significantly increased the contents of soil total nitrogen (TN), microbial biomass nitrogen (MBN), ammonium nitrogen (NH₄⁺-N) and β-N-acetylglucosaminidase (NAG) activity (p<0.05). The contents of nitrate nitrogen (NO₃^--N), dissolved organic nitrogen (DON) and the activities of β-glucosidase (βG) and cellulolytic enzyme (CBH) showed an increasing trend with the increase of nitrogen application level. (3) Redundancy analysis (RDA) showed that soil TN and NAG enzymes were positively correlated with organic nitrogen and its fractions, while soil MBN and NH₄⁺-N were correlated with SON fractions. Overall, nitrogen deposition in this region improves soil nitrogen availability and microbial activity, which is helpful to further understand the soil nutrient transformation and cycling mechanism in subtropical forests under global climate change.

Abstract:In order to investigate the effects of pruning measures on the vegetation and soil of the salt lake protection forest in the transition zone of the Jilantai Desert Oasis, planted flower stick forests with different pruning years (1, 2 and 3 years) were used as research objects to compare and analyse the vegetation growth characteristics and soil physicochemical properties of Hedysarum scoparium forests with different pruning years. The results showed that: (1) Prune measure was beneficial to self-renewal of Hedysarum scoparium. The plant height and basal diameter of Hedysarum scoparium increased with the increase of age, and number of new branches followed an opposite trend. (2) Prune measure increased herbaceous biomass and herbaceous plant diversity under the forest, and the plant life forms were dominated by annuals and perennials in different pruning years of Hedysarum scoparium plantation. Understory vegetation coverage, density, plant height, aboveground biomass, Shannon-Wiener diversity index, Simpson dominance index and Margalef richness index were the highest in pruning 3 years Hedysarum scoparium. (3) At the beginning of pruning Hedysarum scoparium, wind erosion caused some fine particles to be blown away on the surface. The mechanical composition of the 0—30 cm soil layer was dominated by fine sand content and medium sand content, with the values ranging from 77.63% to 88.02%. (4) Pruning measure promoted soil water retention. The soil moisture content in 0—200 cm soil layer ranged as follows: 3 years > 2 years > 1 year > no pruning, and soil water stability became inferior. (5) Prune measure was conducive to soil nutrient accumulation. Soil organic carbon, total nitrogen, total phosphorus, alkali-hydrolyzed nitrogen and available phosphorus under Hedysarum scoparium forest were the highest in 3 years, and increased by 6.67%, 12.90%, 20.00%, 115.51% and 66.24%, compared with no pruning, respectively. The study suggests that appropriate prune measure can improve the habitat of artificial Hedysarum scoparium, but the ground surface needs to be covered to prevent soil water evaporation during the initial stage of pruning measure.

Abstract:Soil moisture is the main driving force for the patterns and processes in arid and semi-arid ecosystem, and topography-vegetation factors are the main factors affecting soil moisture on the small-scale. Soil moisture at different depths (0-40 cm in surface layer, 40-200 cm in middle layer, 200-300 cm in deep layer and 0-300 cm in whole) on fixed sand dunes near the northern sand dune in the southern edge of the Gurbantunggut Desert was used as a study object to investigate the relationship and variation patterns between soil moisture and topography-vegetation factors using generalized linear model (GLM), generalized additive model (GAM) and random forest (RF) models. The results showed that: (1) Soil moisture at different depths showed a consistent single-peaked distribution, and the magnitude of soil moisture at different depths was in the order of: deep > middle > surface, and there were significant differences between the two. (2) The vegetation and terrain factors affecting soil moisture at different depths obtained by GLM and GAM models were identical, and the accuracy of the RF model was better than that of GLM and GAM models. (3) Topographic factors elevation, slope, height difference and vegetation factors shrub multiplicity were negatively correlated with soil moisture at different depths under their influence, while topographic factors slope direction (specified as 0 due east, rotated clockwise) and vegetation factor biomass were positively correlated with the soil moisture they affected. The vegetation factor herbaceous cover was positively correlated with surface soil moisture and negatively correlated with mesocosm soil moisture. The results of the study can provide theoretical reference for the formulation of corresponding wind and sand control measures and the establishment of scientific and reasonable vegetation sand fixation model in the study area.

Abstract:By exploring the effects of nitrogen reduction combined with nitrification inhibitor DMPP and microbial agents and their combined application on soil nitrogen losses in different ways and nitrogen absorption and utilization of cucumber planting in greenhouse, and to screen the optimum nitrogen losses regulation measures for greenhouse vegetable production system by considering both yield and quality. The cucumber variety "Jinlv 20-10" was used as the experimental material to carry out filed experiment, and six treatments were set up, including no nitrogen application control (CK), conventional nitrogen application (CN), nitrogen reduction application (RN), nitrogen reduction application + DMPP (RND), nitrogen reduction application + microbial agent (RNM), nitrogen reduction application + DMPP + microbial agent (RND+M). Soil nitrous oxide (N₂O) emission, ammonia (NH₃) volatilization and soil profile nitrate nitrogen (NO₃^--N) accumulation, as well as the absorption and utilization, yield, and quality indicators of nitrogen by cucumbers were monitored and analyzed. The results showed that: (1) Compared with CN treatment, the absorption and utilization of nitrogen and nitrogen utilization rate of cucumber were improved by RN, RND, RNM and RND+M treatments. Under the same nitrogen application rate, RND+M treatment could increase total nitrogen absorption in shoots of cucumber by 18.93%, especially the apparent recovery rate of applied nitrogen (REN) and agronomic efficiency of nitrogen fertilizer (AEN) could reached up to 25.30% and 41.16 kg/kg (p<0.05), respectively, showing obvious positive synergistic effect, and better than the application of DMPP or microbial agent alone. (2) The soil N₂O emission, NH₃ volatilization and NO₃^--N accumulation in 0-120 cm soil profile were significantly decreased by 26.38%~41.45%, 28.82%~37.70%, and 13.07%~62.32% in the RN, RND, RNM and RND+M treatments compared with CN, respectively. Under the same nitrogen application rate, RNM treatment had little effect on N₂O emission and NH₃ volatilization in soil, but it could significantly reduce the NO₃^--N accumulation in 90-120 cm soil layer, which was 27.35% lower than that of RN. The N₂O emission in the treatments of RND and RND+M were reduced by 20.11% and 20.47%, and NO₃^--N accumulation in 0—120 cm soil profile were reduced by 30.06% and 24.70%, respectively, reducing the risk of nitrogen accumulation and leaching in the soil but increasing the potential risk of NH₃ volatilization (p>0.05). The performance of prevention and control of nitrogen losses was as follows: RND≈RND+M≥RNM≈RN. (3) Compared with RN treatment, the cucumber yield in RND+M treatments reached up to 70.32 t/hm². Besides, the cost-saving and profit-increasing increased 5150 yuan/hm². Moreover, the effect of RND+M treatment on improving the quality of cucumber fruit was more obvious, and the soluble protein content was 16.36% and 4.01% higher than that of RN and RNM treatment respectively. Comprehensive considering both the economic and environmental benefits, especially from the perspective view of sustainable soil development, under the experimental conditions, nitrogen applied as top dressing at the rate of 316 kg/hm², combined with 2% pure nitrogen of DMPP and 75 L/hm² microbial agent, which is considered to be an appropriate nitrogen losses regulation measure to achieve the high yield and quality, and green and high-quality development of greenhouse cucumber.

Abstract:To analyze runoff and sediment change of flood event in the Chabagou watershed under the condition of large-scale vegetation restoration plays an important role in revealing the evolution law of soil erosion on the Loess Plateau and the regulation of runoff and sediment in the Yellow River. Based on 101 flood events, combined with NDVI and rainfall data, the paper analyzed runoff and sediment characteristics of flood event in Chabagou watershed during different ecological construction periods, and selected two typical flood events for comparison to reveal the relationship between sediment transport and runoff erosion energy. The results showed that the average runoff amount of flood event in Period Ⅱ was 1.86 times that of Period I, but the average sediment yield was only 0.52 times. In the four peak discharge classifications, the average sediment transport modulus of flood event in Period I was significantly higher than that in Period Ⅱ. Compared with the flood event NO.2, the runoff and sediment transport process of NO.100 in Period Ⅱ showed good synchronization, and the flood duration was longer. In addition, the peak flow and peak sediment transport were significantly lower. The sediment transport modulus of flood event in both periods I and Ⅱ increased with the increase of runoff erosion power, but the sediment transport modulus in Period Ⅱ was lower than that in Period I. The results showed that large-scale vegetation restoration played a more significant role in regulating sediment transport of flood event than runoff in typical watershed on the Loess Plateau.

Abstract:Rainfall can alter soil moisture status and promote transpiration in forest trees, but the effect of rainfall amount and its duration on sap flow and its environmental control mechanism remains unclear. Therefore, the poplar (Populus×euramericana) plantation of a riparian ecosystem free from soil water stress was selected as the research object in Gongqing Forestry in Shunyi District of Beijing, a semi-arid and semi-humid zone in northern China. During the growing seasons of 2019 and 2021, the TDP sensors was uesd to measure sap flow, as well as the environmental conditions such as climatic factors and soil water content. Based on the results of statistical analysis of long term (2016—2017,2019 and 2021) rainfall data in the region, the event with an interval of two rainfall pulses more than 22.5 h was divided into two separate rainfall events. According to the rainfall amount and duration of the rainfall event, the events with median ±1.5 times standard error were defined as common events, while the events with a cumulative probability greater than 90% were defined as extreme events. The results showed that: (1) Solar radiation was the only environmental factor that significantly controlled sap flow in this poplar plantation during the growing season (partial correlation coefficient r_p = 0.539). Vapor pressure deficit, wind speed and soil moisture content were not correlated with sap flow (p > 0.533), and this environmental control did not change before and after the rainfall event; (2) Sap flow decreased with the increase of rainfall amount after the rainfall events (R²=0.78, p = 0.004), but there was no significant correlation with the duration of rainfall events; (3) There were no significant differences in sap flow over time on the half-hourly scale following both common events and extreme events (p ≥ 0.264), but the dominant environmental control factors after the four types of rainfall events were not identical. Specifically, solar radiation and vapor pressure deficit always significantly affected half-hourly sap flow (r_p ≥ 0.374), while soil water content only significantly increased half-hourly sap flow after common and extreme rainfall duration events (r_p ≥ 0.215). Wind speed significantly suppressed half-hourly sap flow after common rainfall amount events (r_p = -0.258), but significantly enhanced half-hourly sap flow after common and extreme rainfall duration events (r_p≥ 0.183). The results of the study provide further insight into the influence of rainfall characteristics on sap flow and its biophysical control mechanisms, as well as improving the modelling and assessment of ecohydrological processes under climate change.

Abstract:The effects of different biochar mixing amounts on the evaporation characteristics of brackish water were investigated by centrifuge test and indoor soil column simulation test. Three biochar mass addition ratios (B₀, B₂ and B₄) and four brackish water salinity ratios (W₀, W₁, W₃ and W₅) were set up in the experiment. The effects of different treatments on soil water characteristic curve, pore distribution, cumulative evaporation, salt transport and daily variation of soil temperature under brackish water evaporation were analyzed, and the evaporation model was used for fitting analysis. The results showed that the combined application of biochar and brackish water could improve soil water holding capacity of soil and increase the proportion of larger and smaller pores in soil; The cumulative evaporation of soil water first decreased and then increased with the increase of biochar mixture, when the biochar mixture was 2%, brackish water evaporation could be inhibited better; Rose evaporation model could fit brackish water evaporation well; Biochar mixing in soil could reduce the surface accumulation of salt and make it evenly distributed in soil; Biochar could effectively reduce the diurnal variation of soil temperature; With the same amount of biochar application, brackish water with a salinity of 3 g/L could reduce the average soil temperature of 0-10 cm and increase the average soil temperature of 10-50 cm. Taking all the indexes into consideration, the biochar and brackish water treated with B₂W₃ are more suitable for farmland application, which provides a theoretical basis for better utilization of brackish water irrigation in arid areas of Northwest China.

Abstract:In order to investigate the stability of soil aggregates and the distribution characteristics of organic carbon (SOC) and total nitrogen (TN) aggregates in different particle sizes under different green manures application in dryland wheat fields in southern of Shanxi Province, and further understand the mechanism of carbon and nitrogen conservation of different green manures. Topsoil samples of 0-10, 10-20 and 20-30 cm after three consecutive years (2018—2021) during the winter wheat harvest period were collected under different green manure treatments (control, soybean, mung bean, sunflower, maize). Wet sieve method was used to classify the soil particle size. The contents of SOC and TN in coarse macroaggregates (>2 mm), fine macroaggregates (0.25~2 mm), microaggregates (0.053~0.25 mm) and silt+clay (<0.053 mm), and the stability of aggregates (R_0.25, aggregates mass fractions of >0.25 mm; MWD, mean weight diameter; GMD, geometric mean diameter) were measured. The contribution rates of aggregate SOC and TN to soil total organic carbon and total nitrogen of different particle sizes were measured. The results showed that the proportion of soil aggregate mass of fine and large aggregates was mainly 0.25~2 mm (22.77%~39.71%) under different green manure treatments. Aggregates mass fractions of >2 mm in 0-30 cm soil layer was significantly increased under green manure application, especially under soybean green manure, while the mass proportion of 0.25~2 mm and 0.053~0.25 mm particle size decreased, the mass proportion of <0.053 mm showed no obvious. Soybean green manure significantly increased R_0.25, MWD and GMD values in all soil layers. Soybean and maize significantly increased the soil total organic carbon content in 0-30 cm soil layers by 27.83% and 25.71%, respectively. Soybean green manure further increased the content of SOC in soil aggregates of different particle sizes. Applying green manure reduced the soil total nitrogen content, soybean green fertilizer treatment had the smallest reduction degree, and had an effect on increasing the total nitrogen content of <0.053 mm silt clay. The contribution rates of soil organic carbon and total nitrogen in 0-10 cm soil layer were the highest in large aggregates of 0.25~2 and >2 mm. Green manure (mean 21.39) application increased the soil C/N ratio by 7.68 compared with the control fallow (mean 13.71), among which maize had the best lifting effect, followed by soybean. Combined with the effect of soil carbon and preserve nitrogen in dryland wheat fields, soybean green manure for three consecutive years can effectively improve the stability of soil aggregates and soil fertility.

Abstract:Spectral reflectance and humic substances components were determined aiming at studying the effects of different fertilization on humic substances content and color of black soil based on 30 years long-term location trial. A total of 5treatments were included in this study: (1) Fallow; (2) No fertilizer application (CK); (3) Only chemical fertilizer (NPK); (4) Organic fertilizer partly replaced chemical fertilizer (NPKM); (5) Straw partly replaced chemical fertilizer (NPKS). Results indicated that soil organic carbon content in Fallow, NPKM, NPKS were significantly increased by 49.7%, 74.3%, 27.0% in contrast with NPK (p<0.05). The highest content of humic acid (HA) was 3.9 g/kg observed in NPKM, and following was in order of CK, NPKS, NPK, Fallow. Soil fulvic acid (FA) contents in NPKM, NPKS and Fallow were in range of 2.2 to 2.3 g/kg, significantly higher than NPK and CK. Soil humin (HM) content in NPKM was 18.6 g/kg, significantly higher than other treatments (p<0.05). The order of soil spectral reflectance from high to low was as following NPK > Fallow, CK > NPKS > NPKM. In contrast with CK, soil spectral reflectance in NPK was increased by 6.5% on average, while in NPKS and NPKM were decreased by 11.1% and 15.1% in average, respectively. According to the linear correlation analysis results, the spectral reflectance of black soil was significantly negatively correlated with soil HA and HM contents (p<0.01), and the correlation coefficient (r) were -0.858 and -0.681, respectively. Summing up the results above, it can be concluded that long-term organic materials application could significantly enhance soil humic substance content, lower soil spectral reflectance, and make black soil darker. Oppositely, long-term chemical fertilizer application increased soil spectral reflectance, and made black soil "faded". The effects of organic manure on improving soil organic materials and humic substances were better than straw.

Abstract:To study the effects of combined straw returning with organic fertilizer replacing partly chemical fertilizer on grain yield, grain quality and chemical fertilizer use efficiency in dryland maize-wheat double cropping system, From 2015 to 2020, based on a long-term field experiment conducted at Luoyang Dry Farming Experimental Station of Chinese Academy of Agricultural Sciences, since 2007. There are three treatments, i.e., no fertilizer control (CK), conventional application of nitrogen, phosphorus and potassium fertilizer in both maize and wheat season (NPK), straw mulching and organic fertilizer combined with replacing 1/3 of NPK input in wheat season (SORF). The grain yields and fertilizer use efficiencies in maize, wheat and all year from 2015 to 2020, and the grain nitrogen, phosphorus and potassium contents, grain protein contents, grain protein yields of maize and wheat from 2019 to 2020, and the contents of protein and its components in grain of wheat in 2020 were investigated. The results showed that: (1) Compared with the NPK treatment, the 5-year average yield of maize under SORF treatment were increased by 10.0%. However, there was no significant grain yield difference of wheat and all year between NPK and SORF treatments(p>0.05). (2) The grain N, P, K content in maize and wheat was increased significantly with the application of fertilizer. Compared with NPK treatment, SORF significantly increased grain nitrogen content, which significantly increased in protein content and protein yield of maize grain and wheat grain by 6.7% and 17.8%, 8.0% and 6.3%, respectively, and annual protein yield increased by 10.8%. (3) SORF and NPK not only increased the contents of each protein component, but also increased the ratio of glutenin/gliadin in wheat grain, and synergistically improving the protein quantity and quality in grain. Compared with the NPK treatment, SORF significantly increased the content of different grain protein component except globulin, but the increase of glutenin/gliadin ratio was not significant. (4) Compared with NPK treatment, the nitrogen agronomic use efficiency under SORF treatment were significantly increased by 54.8%, 31.2% and 77.3% in maize, wheat and all year, as well as nitrogen partial productivity by 10.0%, 45.6% and 20.7%, respectively, and the phosphate (potassium) agronomic efficiency and partial productivity by 31.2%, 77.3% and 45.6%, 55.7% in wheat and all year. Above all, SORF could not only improve the grain yield in maize, and the grain protein content, protein yield, as well as agronomic efficiency and partial productivity in maize and wheat, but also improved the contents of different grain protein components in wheat. Therefore, straw mulching combined with organic fertilizers replacing 1/3 of NPK of wheat season was the suitable fertilization model for high yield, high quality and high efficiency in the maize-wheat double cropping system of dryland region.

Abstract:The ecological space of Chengdu-Chongqing Twin Cities Economic Circle is an important part of ecological civilization construction in southwest China. Taking the ecological space of Shuangcheng economic circle in Chengdu-Chongqing region as the research object, based on the theories of composite ecosystem, integrated protection and management of mountains, water forests, fields, lakes, grass and sand, this study comprehensively selected evaluation indicators from the aspects of policy objectives and public demand, used the coefficient of variation method and judgment matrix method to carry out ecological spatial zoning and proposes corresponding control mechanisms. The results showed that: (1) ESQ showed a stable and positive trend in the past 10 years, with a "basin-type" distribution pattern of low central space and high four weeks, and the quality grade change showed the characteristics of "good in the middle and stable in all around", mainly unchanged and improving; (2) ESQ was between weak variation and medium variation, and the proportion of weak variation area was large, and ESQ was relatively stable as a whole; (3) Based on the analysis of quality change characteristics and stability, the ecological space was divided into key protected areas, potential restoration areas, key restoration areas and ecological conservation areas. Implemented original ecological protection in key protected areas, and carryed out closed nature conservation; the key restoration areas were mainly artificial ecosystems, focusing on the implementation of artificial restoration, and carrying out ecological restoration and treatment projects; potential restoration areas should give priority to protection, focused on natural restoration, and strive to improve the overall ecological state; ecological conservation area was the main type of ecological space in the research area, ecological conservation should be implemented, on the basis of ecological protection, production development and construction could be reasonably carried out, and this area could provide strategic direction for the future urban development of the research area and reserve space for development. The study of zoning management and control of ecological space can facilitate decision-makers to identify and manage ecological protection and restoration space, and provide new ideas for the future development direction of the Chengdu-Chongqing Twin Cities Economic Circle.

Abstract:Due to the rapid development of urbanization and the impact of extreme weather, the conflict between urban land use and flood safety becomes prominent while the flooding risk increases. Taking Quxian of Sichuan Province as the study area, we updated the flood level and conduct inundation risk analysis. Using historical flood records and observation data over the past few decades, we established the flood level dataset and re-estimated the flood level in various recurrence intervals by analyzing the distribution of flood frequency and peak flood levels, and the correlation between flood levels at different locations. It was shown that, as a result of extreme weather, the flood levels of the main counties in Quxian have increased by an average of 40 cm compared with historical flood levels, i,e., those of the once-in-100-year, once-in-50-year, and once-in-10-year have risen to 254.75, 253.48 and 250.54 m, respectively. According to the national flood control standard, the central city of Quxian and Sanhui County should be able to resist flood with recurrence intervals of 50 and 20 years respectively, while other counties along the river remain at 10 years. Compared with the current flood control standard, the updated standards could potentially prevent agricultural and construction land from flooding by more than 30 and 7~8 km² respectively.

Abstract:In order to study the impact of different land preparation measures on the quality of the soil of the terraced orchards, three typical slopes (optimized prepared slope T_y, traditional prepared terraced slop T_c, and abandoned land CK) in navel orange orchard development demonstration area of Xiaoyang small watershed in Ningdu County, southern Jiangxi Province were selected as the research object. The primary component analysis method (PCA) was used to screen the minimum data set indicator to evaluate the soil quality in this area. The results showed that: (1) Total Data Set(TDS) and Minimum Data Setting(MDS) soil quality indexes had a significant positive correlation, R² = 0.604, indicating that MDS could instead of TDS to conduct soil quality evaluation of navel orange orchard development demonstration area in Ningdu County; (2) The soil quality index (SQI) of 3 typical slopes was manifested as: optimizing prepared terraced slope(0.477) > abandoned land(0.436) > traditional prepared terraced slop(0.220). There was no significant difference between T_y and CK, and SQI of T_y was about 1.16 times higher than that of T_c, indicating that soil quality would be significantly improved under optimized soil preparation measures; (3) In general, the SQI of the surface layer (0—10 cm) was higher than that of the deep soil (10—20 cm) in the different soil layers of the orchard. The SQI classification showed that the soil quality of the optimized terraced and abandoned land was better than that of the traditional prepared terraced slop. The research results can provide a scientific basis for the utilization and management of slope land resources in the red soil hilly region of South China and the layout of soil and water conservation measures after terrace construction.

Abstract:The properties and aging of biochar are important factors affecting the remediation effect of biochar in immobilizing Cd-contaminated soil. The differences of Cd²⁺ adsorption and Cd-contaminated soil immobilization efficiency of four different types biochar materials (sludge-based, straw-based, animal and poultry manure-based and wood-based) were comparatively investigated. The results showed that the application of biochar significantly increased the pH of soil pore-water (except palm fibers biochar), and decreased the concentrations of DOC and Cd in pore-water, and thus reduced the Cd uptake of rice roots in pore-water. At the same time, the application of four kinds of biochar increased soil pH value, but decreased soil available Cd, rice root and grain Cd content. However, aging weakened the immobilization effect of rice straw biochar and significantly enhanced the immobilization effect of palm fibers biochar on soil Cd, while aging had little effect on ash rich pig manure biochar and sludge biochar. Therefore, the raw materials and aging effects of biochar must be considered when choosing biochar immobilization to remediate Cd contaminated paddy soil.

Abstract:To improve the phytoextraction capacity of Cd hyperaccumulotor Sedum plumbizicola, pot experiments were done to investigate the effects of the chelating agent ethylenediaminetetraacetic acid (EDTA) and the plant hormone abscisic acid (ABA) on the growth and Cd transport of Sedum plumbizicola and verified by field experiment. The results of pot experiments showed that the foliar spraying EDTA and ABA could promote the transport of Cd by Sedum plumbizicola, and the transport coefficient of Cd from underground part to aboveground part was EDTA > ABA. But foliar application of EDTA inhibit the growth of Sedum plumbizicola. The concentrations of Cd in different tissues of Sedum plumbizicola varied greatly, with new leaves > roots > stems > old leaves. The concentration of Cd in the new leaves was 3.6~5.4 times of that in old leaves, and the majority was enriched in the cell wall and organelle fraction, accounting for 88%~94% of the total. EDTA treatment caused a sharp increase in the proportion of Cd allocated to organelles, and ABA, on the contrary, greatly increased the proportion of Cd distributed in the cell wall of new leaves. The combination of ABA and EDTA could alleviate the inhibition of growth by EDTA, and could be conducive to the Cd transportation from root to aboveground.. Field experiment verified that the enhanced phytoextraction of Sedum plumbizicola in Cd contaminated soil based on the foliar application of ABA and EDTA was feasible. The combination of ABA and EDTA treatment significantly increased the total Cd accumulation of Sedum plumbizicola by 37.87%. The results provide theoretical guidance for strengthening the remediation of Cd contaminated soil by Sedum plumbizicola.

Abstract:In order to realize the safe utilization of different types of Cd-contaminated soil by amendment treatment, the effects of calcium amendment material on soil pH, CEC, available Cd content, Cd fraction, biomass and Cd content of Chinese cabbage under different dosage levels were studied by laboratory culture and soil culture experiments. The results showed that: (1) The pH and CEC of the six soils were increased by calcium amendment material, and the CEC of the soil continued to increase with the increase of the amount of calcium amendment material, while the pH of the soil did not increase with the increase of the amount of calcium amendment material. (2) With the increase of amendment material dosage, the content of available Cd in the six soils decreased significantly at first and then stabilized, and there was no significant change when the amount of amendment material was greater than 2.5%. Under this addition level, the decrease of effective Cd content was as follows: typical yellow soil (63.32%) > acid purple soil (46.65%) > rinsed yellow soil (38.51%) > neutral purple soil (34.97%) > calcareous purple soil (18.03%) > lime-aquic soil (16.60%). The exchangeable Cd in soil mainly changed to carbonate binding state, Fe-Mn oxide binding state and residue state. (3) Except calcareous purple soil, calcareous amendment material significantly increased the biomass of Chinese cabbage in the other five contaminated soils and significantly decreased the content of Cd in the edible parts. When the dosage was 2.5%, the Cd content of Chinese cabbage in typical yellow soil, rinsed yellow soil and acid purple soil decreased by 84.28%, 79.90% and 69.87%, which was significantly better than that in neutral purple soil, lime-aquic soil and callitic purple soil (the decrease was only 40.27%, 31.13% and 17.98% when the dosage was 5%). This study revealed the dose-effect difference of calcium amendment material on six kinds of Cd polluted upland soils, and the immobilizing efficiency was better in typical yellow soil, rinsed yellow soil and acid purple soil, which provided a scientific basis for rational use of calcium amendment material under different soil conditions.