Abstract:Objective Traditional gully classification systems focus on agricultural landscapes. However, on the Qinghai-Xizang Plateau, where human activity is limited, gullies primarily occur in natural landscapes. Therefore, it is necessary to propose a tailored gully classification system that is suited to the natural landscapes of the Qinghai-Xizang Plateau.Methods Extensive field investigations were conducted in typical regions of the Qinghai-Xizang Plateau, including the Yarlung Zangbo River and its two tributaries, the Southeast Xizang, the Qiangtang Plateau, the Three-River Headwaters region, the Hehuang Valley, the Qaidam Basin, and the Qilian Mountains. These field studies were complemented by indoor interpretations using sub-meter high-resolution remote sensing imagery.Results Various landforms that resemble but are not gullies in terms of genesis or morphology were identified and distinguished. The gullies were classified based on multiple criteria, including scale, genesis, the landform in which they developed, and morphology. The gullies were classified by scale into small, medium, large, and giant gullies; by genesis into rainfall-runoff gullies, snowmelt-mudflow gullies, glacial gullies, permafrost-thermal gullies, and human activity gullies; by the landform in which they developed into steep-slope gullies, valley-bottom gullies, gentle-slope gullies, cliff gullies, terrace gullies, tableland-edge gullies, and tableland-surface gullies; and by morphology into straight gullies, curved gullies, spoon-shaped gullies, strip-shaped gullies, widened gullies, narrow-long gullies, wide-short gullies, radial gullies, parallel gullies, and dendritic gullies.Conclusion This study preliminarily proposes a comprehensive gully classification system based on multiple criteria suitable for the characteristics of the Qinghai-Xizang Plateau. It suggests using scale as the primary basis for comparison with gully classification systems in other regions, such as the Loess Plateau, and provides support for soil erosion research and ecological environment protection on the Qinghai-Xizang Plateau.

Abstract:Objective The ecological environment in China's arid and semi-arid regions is highly vulnerable, with soil erosion posing a significant challenge. In light of climate warming, investigating the current state of soil water erosion in these regions is of critical importance.Methods Based on the RULSE model, the model factors and soil water erosion modulus for China's arid and semi-arid regions for the years 1990, 2000, 2010, 2015 and 2020 were calculated, and an accuracy validation (R²=0.60) was conducted. On the basis of the calculations and validation, the optimal parameter geographic detector was utilized to analyze the dynamic driving forces and changes associated with both single and interactive factors.Results 1) From 1990 to 2020, the average annual soil water erosion in China's arid and semi-arid regions amounted to 4.71×10¹⁰ kg, exhibiting a slight upward trend in the soil water erosion modulus at a rate of 0.000 7 t/(hm²·a). 2) The intensity of soil water erosion was predominantly characterized by slight to moderate erosion. The proportions of areas experiencing increases and decreases in soil water erosion intensity both rose, while the proportion of areas with stable soil water erosion intensity declined. 3) Slope, precipitation, and precipitation erosion force were identified as the primary single driving factors of soil water erosion in these regions from 1990 to 2020, with these three factors alternating as the main dominant factor throughout the study period. Interactions between any two selected factors enhances the explanatory power regarding soil water erosion, with the interaction between slope and precipitation erosion force consistently serving as the primary dominant interaction factor during the study period.Conclusion Overall, the soil water erosion situation in China's arid and semi-arid regions is experiencing slight deterioration. To effectively address this issue, it is crucial to consider topographical and precipitation characteristics concurrently when implementing management measures, in order to improve soil water erosion conditions in arid areas.

Abstract:Objective To explore the transpiration characteristics of common trees and their responses to meteorological factors in secondary forests on karst slopes.Methods Heat diffusion probe method (TDP) was used to monitor Broussonetia papyrifera, Koelreuteria paniculata, Triadica sebifera, Ailanthus altissima, Melia azedarach, Toona sinensis, and Rhus chinensis in Puding karst ecosystem observation and research station of Chinese academy of sciences, and to study the relationship between tree transpiration characteristics and meteorological factors.Results 1) The average daily transpiration of B. papyrifera, K. paniculata, T. sebifera, A. altissima, M. azedarach, T. sinensis, and R.chinensis were (4 409.97±3 260.63), (6 611.27±5 629.57), (3 956.32±2 498.50), (2 984.98±2 039.09), (6 300.25±4 637.71), (780.69±738.80) and (2 320.73±1 717.18) g/d, respectively. 2) The sap flow rates of B. papyrifera, K. paniculata, T. sebifera, A. altissima, M. azedarach, T. sinensis, and R. chinensis were the highest in sunny days, followed by cloudy days, and the lowest in rainy days. 3) The influence of atmospheric temperature (T) and saturated vapor pressure difference (VPD) on B. papyrifera, K. paniculata, T. sebifera, A. altissima, M. azedarach, T. sinensis, and R. chinensis under sunny weather was the greatest, followed by that on relative humidity (RH) and total irradiance (Eg).Conclusion The transpiration of common trees in secondary forests on karst slopes is limited by special water environment. Different deciduous trees have different water use strategies, and the rate of sap flow is mainly affected by VPD and Eg.

Abstract:Objective Peak-cluster depression is one of the important karst landform types. Exploring the influence of different landscape positions on soil saturated hydraulic conductivity (Ks) can provide a reference for further understanding of the hydrological processes in this area.Methods Saturated hydraulic conductivity and the corresponding soil physical and chemical properties of different soil depths on the slope and in the depression were measured. By measuring Ks and soil physical and chemical properties at different soil depths on the slope and in the depression, the distribution characteristics of Ks and the corresponding influencing factors were studied according to variance analysis, regression analysis and path analysis.Results Landscape position and soil depth had a significant influence on Ks distribution (p < 0.05). The influence of landscape position was mainly identified at 0—10 and 20—30 cm soil depths, and the influence of soil depth was primarily occurred found on the slope. The effect of land use on Ks was not significant (p > 0.05). The influence of landscape position on soil particle composition and total phosphorus was not obvious (p > 0.05), but organic carbon, total nitrogen and bulk density changed significantly with landscape position (p < 0.05). For the slope, Ks was significantly positively correlated with silt, sand, organic carbon and total phosphorus (p < 0.05), and significantly negatively correlated with clay and bulk density (p < 0.05). For the depression, there was a significant positive correlation between Ks and bulk density (p < 0.05). Path analysis indicated that bulk density and organic carbon were the primary factors affecting Ks for both the slope and depression. The regression equations of Ks for the slope and depression were established based on multiple stepwise regression, and the variance explanation rates of the influencing factors were 76.2% and 32.6%, respectively.Conclusion The results showed that the difference in geomorphic features had a major impact on the distribution of soil hydrological parameters, and can provide a scientific basis for the study of soil and water processes in small peak-cluster depression watershed of the karst region.

Abstract:Objective To investigate the effect of winter soil freezing on soil erodibility and anti-erodibility in the Yellow River section of the Ulan Buh Desert.Methods Particle size screening experiments were conducted on dry, wet, and frozen sand on the windward slope of mobile dunes, along with shear strength tests before and after freezing.Results Sand particle sizes at three positions on the dunes increased due to the bonding effect of water. The particle size peak shifted from 0.15—0.2 mm to 0.3—0.355 mm, with approximately 35.12% of fine sand particles bonding to form larger, medium sand particles. After freezing, very coarse sand emerged, and the particle size peak shifted to 0.5—0.6 mm. Sand particles bonded and coarsened, forming coarse and very coarse sand (52.02%). The proportion of highly erodible particles decreased to 23%—36%, while moderately erodible particles increased to 53%—63%, and hard-to-erode particles increased to 2%—17%. As soil moisture in the dunes increased, the cohesion of frozen soil significantly increased (p < 0.05), along with shear strength and erosion resistance (p < 0.01). Freezing coarsened sand bonds in dune soil, increasing the proportion of moderately and hard-to-erode particles (up to 70%), shear strength by 0.14%—13.07%, and erosion resistance by 0.6%—2.2%. Freezing could effectively improve the corrosion resistance of sand dune soil and inhibit wind erosion.Conclusion The research results can provide a theoretical basis for the wind erosion resistance of dune wind erosion "bare spot" in freezing period.

Abstract:Objective To investigate the characteristics of runoff-phosphorus loss hysteresis relationship under different rainfall types.Methods This study focused on the Menglianggu small watershed in the rocky mountainous area of northern China. Using data from 32 rainfall events recorded between 2010 and 2012, C-Q (concentration-discharge) loops and Pearson correlation analysis were applied.Results 1) During torrential rain, a large amount of phosphorus was released after soil saturation, causing the phosphorus concentration peak to lag behind the runoff peak. In the case of heavy rain, dissolved phosphorus was released from nearby sources, while particulate phosphorus was transported from distant sources to the runoff. During moderate rain, the transport of DIP (dissolved inorganic phosphorus), PP (particulate phosphorus), and TP (total phosphorus) was mainly influenced by surface runoff, whereas DP (dissolved phosphorus) was affected by soil and sediment. Light rain showed rapid transport of DP and slower transport of PP. 2) The C-Q loops of phosphorus transfer exhibited various patterns during the runoff process. PP and TP often showed a clockwise lag, accounting for 18%—23%, mainly due to the strong scouring of surface runoff. The counterclockwise lag appeared in 12%—18% of the phosphorus components, resulting from the slow release of soil phosphorus and the resuspension of riverbed sediments. Dissolved phosphorus loss mainly exhibited a figure-eight positive loop, accounting for 16%, while DIP loss showed a figure-eight negative loop, accounting for 19%. Linear lags were less frequent, and complex lags ranged between 31% and 45%. 3) Under torrential and heavy rain conditions, DIP and DP had weak or negative correlations with runoff (Q), attributed to the rapid surface scouring, which caused PP to be more easily lost, while DP was adsorbed by the soil or diluted by the runoff. Under moderate rain, the appropriate runoff scouring force enhanced the releases of DP. In light rain, runoff primarily transported PP attached to loose soil particles. Particulate phosphorus and total phosphorus were consistently highly correlated across different rainfall types, indicating that TP mainly originated from PP.Conclusion The Menglianggu watershed needs to be protected against phosphorus loss for different rainfall conditions.

Abstract:ObjectiveRestoring vegetation and combating rocky desertification on dolomite slopes in karst regions face significant challenges. The upper epikarst zone, which underlies the shallow soil layer, plays a crucial role in ecosystem processes. Nevertheless, the coupling relationships between the soil and the upper epikarst zone remain poorly understood.MethodsA representative dolomite hillslope was chosen for detailed soil-epikarst system structure investigation through trench excavation method. By integrating Kriging interpolation with geographically weighted regression analysis, the spatial distribution characteristics of different medium layers in the soil-epikarst system were analyzed. The study preliminarily proved the co-evolving feature of the soil and the underlying upper epikarst zone on dolomite hillslopes.Results1) The thickness of soil and upper epikarst zone on the dolomite hillslope gradually increased down the slope. The average thickness of the upper epikarst zone on a hillslope scale was 50 cm, with an average volume of 0.47 m³/m², accounting for 43.9% of the total volume of the soil profile, indicating that the ecological function of epikarst in karst regions is extremely important. 2) The soil-epikarst system's structure of the dolomite hillslope exhibited strong spatial heterogeneity. The spatial heterogeneity of the underlying upper epikarst zone (C+C₀=18.88) was significantly higher than that of the overlying soil layer (C+C₀=15.84); 3) The overall soil thickness, especially the B horizon's thickness, was significantly positively correlated with the upper epikarst zone's weathering degree, indicating that the increase of soil thickness promoted the weathering of the underlying upper epikarst zone, and there was a clear coupling and collaborative development relationship between soil and upper epikarst zone.ConclusionThe soil and upper epikarst zone in karst regions have evolved in a mutually reinforcing manner. The upper epikarst zone acts as an essential substrate for supporting the karst ecosystem. The soil thickness, especially the B horizon' thickness, may be critical parameters for predicting epikarst depth on karst hillslopes. In karst areas, the underlying carbonate rocks can not be ignored when carrying out soil and water resources evaluation.

Abstract:ObjectiveTo explore the change rule and influencing factors of soil saturated hydraulic conductivity (Ks) after returning orchard to farmland.MethodsAging apple orchards (AO) and orchards with different tillage years (2 a, 4 a, 6 a, 10 a) on the Loess Plateau were selected as the research objects, and the pure farmland (CK) was used as the control. The Ks and soil basic properties of the 0—200 cm layer in different plots were measured. Pearson correlation analysis was used to analyze the response characteristics and influencing factors of Ks after returning orchard to farmland on the Loess Plateau.ResultsWith the increase of returning years, the average clay and silt content in 0—200 cm soil layer of farmland showed a decreasing trend, the average sand content showed an increasing trend. The order of the mean values of Ks in different plots was (2.25±1.19) cm/h (6 a) > (1.60±0.71) cm/h (AO) > (1.49±0.29) cm/h (4 a) > (1.46±0.44) cm/h (2 a) > (1.40±0.40) cm/h (CK) > (1.04±0.61) cm/h (10 a). On the whole, with the increase of returning years, the average value of Ks increased first and then decreased. With the increase of soil depth, Ks in different plots showed a decreasing trend. The influencing factor of Ks in the 0—40 cm soil layer was organic matter content, and the influencing factors of Ks in the 40—100 and 100—200 cm soil layers were soil bulk density and organic matter content.ConclusionReturning orchard to farmland significantly affected the temporal and spatial distribution characteristics of Ks, and the influencing factors were different at different depths, which were depth-dependent. The results can provide a data basis and theoretical basis for the study of soil water cycle after returning orchard to farmland on the Loess Plateau.

Abstract:ObjectiveTo identify the main driving factors of soil moisture in the middle reaches of the Yellow River, to analyze the impact of land cover and climate change on soil moisture changes in the middle reaches of the Yellow River, and to provide a theoretical basis for regional ecological environmental protection and high-quality development.MethodsThe SiB2 model was used to simulate the surface soil moisture (SSM) and root zone soil moisture (RZSM) in the middle reaches of the Yellow River for the years 2000, 2005, 2010, 2015 and 2020, and to analyze their spatial and temporal distribution patterns. The main driving factors were analyzed by combining the GeoDetector, Random Forest, and SHAP, and the contribution of land cover and climate change to the changes of SSM and RZSM was analyzed by using scenario-setting method.Results1) The SiB2 model could better simulate the soil moisture in the middle reaches of the Yellow River after the parameter calibration. 2) Soil moisture in the middle reaches of the Yellow River showed overall spatial distribution characteristics of high in the south and low in the north, and there were differences in the distribution characteristics of SSM and RZSM under different ecological zones, different seasons and different land cover types. 3) Precipitation, soil type and downward shortwave radiation were the main drivers of SSM in the middle reaches of the Yellow River, and precipitation, soil type and land cover type were the main drivers of RZSM in the middle reaches of the Yellow River, and there were differences in the drivers of soil moisture in different ecological zones. 4) The effect of land cover type conversion on RZSM in the middle reaches of the Yellow River was regionally different, and the main direction of change was the decrease of RZSM due to the increase of leaf area index(LAI). 5) Compared to 2000, the decline in SSM and RZSM in 2020 was dominated by differences in climate change and land cover change, respectively.ConclusionLand cover changes in the middle reaches of the Yellow River from 2000 to 2020 led to a decline in soil moisture in the root zone, and precipitation magnitude had an important effect on changes in soil moisture after land cover type conversion.

Abstract:ObjectiveRainfall is the main source of soil water supply, which directly affects the distribution characteristics of soil water, and then affects the growth of vegetation, to explore the response of soil moisture to typical rainfall at different stands and slope sites in Qiaoshan forest region.MethodsThe Qiaoshan forest area on the southern Loess Plateau was taken as the research object. Through monitoring the rainfall and soil moisture at different depths of typical stands (broad-leaved pure forest and mixed forest), the response characteristics of soil moisture at different layers to rainfall patterns under different vegetation cover and slope location conditions were explored.Results1) Rainfall during the study period was mainly concentrated in August, September and October, with the highest rainfall being 251.7 mm in September. The seasonal differences in soil moisture in the same soil layer at different points were significant (p≤0.05), and the average soil moisture in all soil layers was the lowest in summer.2) During moderate rainfall events, only shallow soil moisture content responded to rainfall, and the response intensity of soil moisture content to rainfall in mixed forest was greater than that in broad-leaved pure forest.3) In the event of heavy rain, the response of soil moisture to rainfall was greater in the mixed forest than in the pure broad-leaved forest, and the response relationship was as follows: lower slope > middle slope > upper slope for the shallow layer, and upper slope > middle slope > lower slope for the deep layer.4) In the event of heavy rainfall, the response of soil moisture to rainfall was greater in broad-leaved pure forest than in mixed broad-leaved forest, and the response relationship was as follows: lower slope > middle slope > upper slope for the shallow layer, and upper slope > middle slope > lower slope in the deep layer.5) In the three rainfall events, the supplement amount of the mixed forest was 1.55, 1.65 and 1.00 times that of the pure broad-leaved forest, respectively.ConclusionIt is of great significance to study the response of soil moisture to rainfall and the process of shallow soil moisture movement in Qiaoshan forest area for optimal allocation of rainfall resources and sustainable restoration of forest ecosystems.

Abstract:ObjectiveForest fire, as the primary natural and human-induced disturbance in subtropical forests, seriously affects the soil biochemical cycle. We aimed to clarify the response of soil extracellular enzyme activities to the restoration process following forest fire disturbance.MethodsWe investigated the soils of subtropical secondary forests at different stages of recovery following forest fire disturbances. Subtropical forest soils at seven stages of restoration were analyzed using a spatial substitution time series approach. The forests were categorized into three age groups, including old forests (60—70 years), middle-aged forests (30—40 years), and young forests (< 20 years). We aimed to reveal the succession patterns of extracellular enzyme activities and their stoichiometric characteristics following forest fire disturbances by measuring invertase activities related to soil carbon (C), nitrogen (N), and phosphorus (P) in subtropical forest soils.ResultsThe activities of soil cellulose hydrolase (CBH) and β-N-acetylglucosaminidase (NAG) increased significantly with forest stand age, but the activities of other extracellular enzymes did not increase significantly with stand age. Correlation analysis and redundancy analysis showed that soil C and N contents were the key factors affecting the change of soil extracellular enzyme activities. In addition, the ratios of soil extracellular enzyme C, N and P were 1∶0.94∶1.53, 1∶1.02∶1.63 and 1∶0.99∶1.47 in young, middle and old forests, respectively, indicating that soil microorganisms in subtropical forest was limited by P, but such P-limitation was improved gradually with forest stand age following forest fire disturbance.ConclusionThe extracellular enzyme activities related to soil N transformation increased with forest stand age following forest fire disturbances in subtropical forest soils. The stoichiometric characteristics of soil extracellular enzyme gradually tended to be stable, indicating that soil health was progressively improved during the restoration process following forest fire disturbance in subtropical forests.

Abstract:ObjectiveTo elucidate the change trajectories of soil erosion intensity in Yunnan Province from 1990 to 2022, and analyze the types of changes and their driving factors, in order to provide a scientific foundation for effective soil erosion control strategies.MethodsSoil erosion intensity conditions in Yunnan Province was quantitatively assessed based on the RUSLE model, and the dynamic characteristics were captured by introducing interannual change rates. Soil erosion intensity change trajectory types were identified by combining change rates and frequencies using an improved Stability Mapping Method (STD). The contribution of driving factors were analyzed, and the characteristics of driving factors across different trajectory types were compared using the Random Forest model.ResultsThe interannual change trend of soil erosion in Yunnan Province was mainly stable, with significant changes observed in areas with substantial decrease and increase. Soil erosion intensity change trajectories exhibited significant spatial differentiation, with cyclical trajectories being the most prevalent (53.90%), followed by non-continuous stepwise (14.78%) and fluctuating types (14.08%). Precipitation, slope, population density, GDP, and vegetation cover were the main driving factors affecting soil erosion intensity trajectory changes, which contributed 17.92%, 14.56%, 12.52%, 12.67% and 9.41%, respectively. There were differences in driving factors across different trajectory types. Areas with cyclical and non-continuous stepwise trajectories had higher precipitation and greater slopes, while stepwise trajectory areas had higher farmland coverage and lower forest coverage.ConclusionThe characteristics of soil erosion intensity trajectory changes in Yunnan Province are significant, with spatial heterogeneity in driving mechanisms. Therefore, soil erosion control strategies should reflect regional differentiation and specificity, and adopt location-specific measures based on regional characteristics. The STD trajectory partitioning method based on change rates effectively captures the dynamic changes in soil erosion, and can provide new insights for monitoring, early warning, and partitioned control of soil erosion.

Abstract:Objective Red soil is a typical soil in Southern China, and organic substitution is an important way to improve the physicochemical properties of red soil. This study aimed to explore the effects of different organic substitution materials and aggregation on the microfauna communities in a red soil.Methods Soil samples from five long-term fertilization treatments were collected, including application of inorganic nitrogen, phosphorus, and potassium (NPK) fertilizer alone (I), NPK+peanut straw (IPS), NPK+rice straw (IRS), NPK+radish (IR) and NPK+pig manure (IPM). Soil aggregates were fractionated, and high-throughput sequencing was used to determine the microfauna communities within the aggregates.Results Compared to I, IPM and IRS significantly increased soil organic matter content, while IPS and IR had relatively smaller effects; IPM also significantly increased soil pH, total nitrogen, and available phosphorus content. Organic substitution had no significant effect on the diversity of soil microfauna but significantly influenced their community structure. Nematodes were the most abundant soil microfauna in upland red soil, with a relative abundance of 93.0% in I; IPM and IRS significantly reduced their relative abundance to 62.2% and 70.0%, respectively, while IPS and IR had smaller effects. Aggregate size significantly affected the Shannon and Chao1 indices of soil microfauna, with the diversity indices of the 53—250 μm and < 53 μm aggregates significantly higher than those of the 250—2 000 μm and > 2 000 μm aggregates, indicating that smaller particle sizes were more conducive to increasing soil microfauna diversity. Aggregate size also significantly affected soil microfauna community structure, but its impact was weaker than that of organic substitution.Conclusion Both organic substitution and aggregate size could significantly affect soil microfauna communities, with pig manure and rice straw having greater effects than peanut straw and radish. The aggregation process reduced microfauna diversity in red soil.

Abstract:Objective Considering the severity of both spring drought and spring cold, and shallow effective topsoil in the southern mountainous areas of Ningxia Province, synergistic effects of no tillage combined with mulching on improving soil moisture use and potato yield were investigated.Methods From 2014 to 2016, three different no-tillage mulching modes, including no-tillage straw mulching (NJ), no-tillage mulching film (ND), no-tillage no mulching (NB), and no-tillage no mulching as control (CK), were set up after autumn crops were harvested for three consecutive years. The effects of no-tillage with mulching mode on soil moisture retention, precipitation utilization and potato yield in arid region of southern Ningxia were analyzed.Results Soil water storage and water storage efficiency during the fallow period were the highest under ND treatment, which increased by 7.60% and 140.35% compared with CK, respectively; Those in normal year and dry year were the highest under NJ treatment, which were increased significantly by 11.18% and 65.43%, and 28.42% and 122.72% compared with CK, respectively. NJ treatment had the highest soil water storage from the seedling stage to harvest in normal and dry years, and from the budding stage to harvest in relatively dry years, which was increased by 10.51%, 12.89% and 20.04%, respectively, compared with CK. ND treatment significantly increased soil water storage by 11.42% compared with CK at the seedling stage in relatively dry years. The no-tillage and straw mulching treatment has the best soil water storage effect from the budding stage to swelling stage of potatoes in relatively dry years, specifically in the 100—140 cm layer, the 40—100 cm layer in normal years, the 0—40 cm layer in dry years, and the 100—160 cm layer. The no-tillage and plastic mulching treatment had the best soil water storage effect on the 180—200 cm layer in normal and dry years. The water consumption in ND treatment was 22.26% and 36.57% higher than that in CK in early growth stage (sowing-budding stage) and middle growth stage (budding-expanding stage) of relatively dry years, respectively. The water consumption in NJ treatment significantly increased by 1.21 times, 7.14 times and 13.91%, respectively, compared with CK, in the late growth period (expanding-harvest stage) and middle and late growth period (budding-harvest stage) of relative dry years and dry years, respectively. Potato yield was the highest in NJ treatment, which was significantly increased by 51.80% compared with CK. In normal years and dry years, potato yield of ND treatment significantly increased by 6.35% and 71.36% compared with CK, respectively. Through correlation analysis, it was found that water consumption during the seedling stage played an important role in potato yield, yield composition, and water use efficiency. The annual precipitation use efficiency, precipitation use efficiency and water use efficiency in the growth period were higher under NJ treatment than under CK, which were significantly increased by 51.79%, 51.80% and 50.52%, respectively; those under ND treatment significantly increased by 35.14%, 36.14% and 21.61% compared with CK in normal years and dry years, respectively.Conclusion No-tillage combined with mulching can effectively improve soil water storage and soil moisture retention during the fallow period and growth period, and significantly improve potato yield and water use efficiency. The no-tillage and straw mulching mode can realize continuous potato yield increase and high water use efficiency.

Abstract:Objective Research on the preferential flow characteristics triggered by cracks in coal mining subsidence areas can provide support for scientific and rational development of water resource management and ecological management practice in the mining area.Methods Three cracks of the same width (3 cm) were selected in the coal mining subsidence area of Shenfu-Dongsheng Coal Field to carry out the staining tracer test under the same rainfall intensity and different rainfall durations. Processing software such as Adobe Photoshop 2020, Image Pro Plus 6.0, SketchUp Pro 2019, and Auto CAD 2 019 were used to analyze the preferential flow characteristics of cracks under different rainfall durations.Results 1) Soil volumetric water content, porosity, and saturated hydraulic conductivity in the preferential flow occurrence area of the Shenfu-Dongsheng coal mining subsidence area were greater than those in the non-preferential flow area, and the volumetric weight and field water-holding capacity were less than those in the non-preferential flow area zone. 2) When the rainfall duration was 10, 20 and 30 min, the corresponding depths of substrate flow were 5, 8 and 10 cm, respectively, while the depths of preferential flow were 26.4, 47.7 and 44.3 cm, respectively. The longer the rainfall duration, the deeper the development of substrate and preferential flow. 3) The staining area ratio at each test site showed a decreasing trend with the increase of soil depth, and the morphology showed an S shape. When the rainfall duration was short, the magnitude of change in the coloring area ratio with soil depth was small; when the rainfall duration was long, the fluctuation of the coloring area ratio curve increased. 4) In general, with the increase of soil depth, the number of wide staining paths decreased, the number of fine staining paths increased, and the total number of staining paths showed a tendency of increasing first and then decreasing. The longer the rainfall duration, the wider the soil staining paths at the same depth was, and there were more wide paths.Conclusion The findings can provide a scientific basis for land reclamation and ecological management in coal mining areas.

Abstract:Objective Soil quality is a critical indicator of ecosystem health and sustainable land management.Methods Key soil quality indicators (e.g., organic matter, total nitrogen, available nitrogen, capillary porosity, and pH) were identified through principal component analysis (PCA), and the soil quality index (SQI) of five typical artificial forest types in the Dianchi Lake Basin was evaluated using the minimum dataset (MDS) method.Results 1) Cyclobalanopsis glauca (CG) and Pinus yunnanensis (PY) forests exhibited significantly higher soil quality than Eucalyptus plantations. CG showed the greatest water retention capacity, while PY had outstanding performance in nutrient supply and fertility maintenance. Mixed forests had the highest organic matter and available nitrogen contents, showing strong nutrient accumulation potential. Shrub forests demonstrated moderate soil quality, with organic matter and total nitrogen levels between that of mixed forests and Eucalyptus plantations. In contrast, Eucalyptus plantations had the lowest SQI, highlighting the adverse effects of monoculture on soil structure and nutrient cycling. 2) Stratified analysis showed that PY had the highest SQI in the surface layer (0—20 cm), CG performed best in the subsurface layer (20—40 cm), while CG and mixed forests were superior in the deep layer (40—60 cm). The average SQI values ranked in the order of CG (0.60) > PY (0.54) > mixed forest (0.47) > shrub forest (0.33) > Eucalyptus plantation (0.20). 3) MDS results showed a strong correlation with the Total Dataset (TDS) (R²=0.69), confirming the method's effectiveness for soil quality assessment.Conclusion The study can provide scientific guidance for soil management in the Dianchi Lake Basin. Mixed planting of CG and PY in water conservation areas is recommended, and management of Eucalyptus plantation should be improved to restore soil quality.

Abstract:Objective The objective of this study was to investigate the effects of various tillage practices on on slope shape and micro-topographic features on typical sloping croplands of southwestern alpine-canyon area.Methods 50 times of conventional tillage and contour tillage events were applied to rectangular plots (5 m×20 m) with a slope of 15° to examine the impacts of tillage disturbance on the slope shape and micro-topographic features by combining the stylus method and 3 D laser scanning technology.Results After 50 times of conventional tillage, the slope shape gradually evolved from a linear slope to a ''-type composite slope, while after contour tillage, the slope shape evolved to a ''-type. After 50 times of successive tillage, the range of soil loss under conventional tillage and contour tillage accounted for 15% and 11% of that of the whole slope, and the range of accumulated soil accounted for 13% and 6% of that of the whole slope, respectively. The two kinds of tillage disturbance patterns caused significant changes in the surface roughness and topographic undulation on the slope, and the degree of change of conventional tillage was greater than that of contour tillage. The average thickness of the soil loss under conventional tillage and contour tillage were 1.17 and 0.45 cm/time, respectively. Tillage frequency had the largest indirect effect on soil loss, while the disturbance patterns had the largest indirect effect on soil loss.Conclusion Tillage frequency and tillage pattern are the most important factors affecting slope shape and micro-topographic features. As the frequency of tillage increases, the amount of soil loss will gradually increase.

Abstract:Objective To explore the effects of water and nitrogen management on soil nitrogen metabolism enzyme activity and wheat nitrogen utilization under irrigation based on soil moisture.Methods The experiment adopted a two-factor split zone design, and the main plot was three irrigation levels, i. e. the relative water content of the 0—40 cm soil layer at jointing and anthesis stages of wheat was supplemented to 65% (W1), 75% (W2) and 85% (W3). The subplot was four nitrogen application rates, i. e. pure nitrogen 0 (N0), 150 (N1), 180 (N2) and 210 (N3) kg/hm². Soil nitrogen metabolism enzyme activity, nitrogen accumulation and translocation, nitrogen nutrition index (NNI), residual amount of nitrate-nitrogen, grain yield, water-and nitrogen-use efficiencies were measured and analyzed in two wheat growing seasons from 2022 to 2024.Results 1) Supplementing irrigation to 75% and applying 180 kg/hm² nitrogen (W2N2 treatment) could significantly improve the activities of soil urease and protease, reduce the activity of soil nitrate reductase, facilitated the transformation of soil nitrogen into crop absorbable forms. According to the results of variance analysis, the effects of irrigation level, nitrogen application rate and their interaction on soil nitrogen metabolism enzyme activity reached a very significant level (p < 0.01). In addition, W2N2 treatment significantly reduced the residual amount of nitrate-nitrogen in the 60—120 cm soil layer, and reduced the risk of soil nitrogen leaching. 2) Both W2N2 and W2N3 treatments could significantly increase nitrogen accumulation in vegetative organs, nitrogen translocation and grain nitrogen accumulation, and had the best NNI, which could meet the nitrogen requirements of wheat. The effects of irrigation level, nitrogen application rate and their interaction on NNI, nitrogen accumulation and transport of wheat reached a significant level (p < 0.01). 3) The highest grain yield could be obtained by W2N2 treatment, while further increasing water and nitrogen input had no significant effect on grain yield. Different irrigation levels and nitrogen application rates had significant effects on grain yield, and the interaction between the two factors reached a very significant level (p < 0.01). The decision coefficient of irrigation level and nitrogen application rate on grain yield was 0.313 and 0.485, respectively. 4) W2N2 treatment had high water-and nitrogen-use efficiencies, that would be easy to cause a significant decrease under continuous improvement of irrigation level and nitrogen application rate. The effects of irrigation level, nitrogen application rate and their interaction on water-and nitrogen-use efficiencies of wheat reached a significant level (p < 0.01). Compared with W2N2 treatment, the two-year average nitrogen fertilizer agronomic efficiencies of W2N3, W3N2 and W3N3 treatment were reduced by 13.02% to 26.34%, the nitrogen utilization rates were reduced by 9.77% to 23.64%, and the irrigation water use efficiencies were reduced by 2.88% to 38.10%.Conclusion The soil relative water content of the 0—40 cm soil layer at the jointing and anthesis stages of wheat supplemented to 75%, and nitrogen applied at 180 kg/hm² can significantly improve wheat grain yield, water-and nitrogen-use efficiencies, nitrogen accumulation, nitrogen translocation in vegetative organs and grain nitrogen accumulation, and have the best soil nitrogen metabolism enzyme activity and NNI. It is the optimal water and nitrogen management for wheat with high yield and high efficiency in the Huang-Huai-Hai region.

Abstract:ObjectiveAcid hydrolyzed soil organic carbon fractions are important in soil, and the changes of their contents will affect soil microbial community composition. The study aimed to investigate the response of acid hydrolyzed soil organic carbon fractions and soil microbial communities to different logging residue treatments.MethodsThree treatments, including residue removed (R), residue burnt (RB) and residue retained (RR), were applied to a Chinese fir plantation in the Castanopsis kawakamii Nature Reserve in Sanming, Fujian, and soils in different soil layers (0—10, 10—20 cm) were collected three years after planting young Chinese fir to study acid hydrolyzed soil organic carbon fractions (labile fraction Ⅰ, Ⅱ and recalcitrant fraction) and microbial community.Results1) Different logging residue treatments had no significant effect on acid hydrolyzed soil organic carbon fractions in the 0—10 cm soil layer. In the 10—20 cm soil layer, the content of labile fraction Ⅰ (LPⅠ) was significantly higher in the RR (7.2 g/kg) and R (6.8 g/kg) treatments than in the RB (4.7 g/kg) treatment, and the contents of labile fraction Ⅱ (LPⅡ, 1.06 g/kg) and recalcitrant fraction (RP, 3.59 g/kg) in the RB treatment were significantly lower than those in the R treatment (1.32 and 7.79 g/kg, respectively). The contents of acid hydrolyzed soil organic carbon fractions in the 0—10 cm soil layer of the RB treatment were all significantly higher than those in the 10—20 cm soil layer. 2) The microbial biomass carbon content of the RB treatment in the 0—10 cm soil layer (335.1 mg/g) was significantly lower than that of the RR (540 mg/g) and R (453.7 mg/g) treatments, but there was no significant difference in soil microbial biomass nitrogen in each soil layer among different treatments. Soil microbial biomass phosphorus content and total PLFAs in the two soil layers were significantly higher in the RR treatment than in the RB treatment. In the 0—10 cm soil layer, the F∶B ratio was significantly higher in the RB treatment than in the RR and R treatments, while GP∶GN ratio was significantly higher in the RR treatment than in the RB and R treatments. 3) There were positive correlations between acid hydrolyzed soil organic carbon fractions and total microbial biomass and PLFAs content of each microbial taxon.ConclusionRetention of logging residue treatments facilitated the maintenance of different soil organic carbon fractions at high levels and had a positive effect on soil microbial biomass and soil microbial community composition. This study is of great significance for taking reasonable management measures of Chinese fir plantations and improving soil productivity.

Abstract:ObjectiveExploring the spatial variability of soil organic carbon (SOC) and the differences in its main controlling factors between karst and non-karst areas.MethodsTaking Wenshan County, a typical karst county in southeast Yunnan Province, as an example, a grid sampling method was employed to conduct the spatial differences in SOC content and storage in top soil (0—20 cm) and deep soil (0—200 cm). Furthermore, we used the semi-variogram function and geographical detector to analyze the impact of external environmental factors on the spatial differentiation of SOC.ResultsThe average SOC content in the top soil and deep soil was 17.80 and 5.18 g/kg, respectively, with a total storage of 3 770.89×10⁴ t. The distribution pattern revealed higher SOC content in the topsoil of the western region and lower SOC content in the central and northern regions, while the deep soil exhibited higher SOC content in the central and western regions and lower SOC content in the northeastern region in Wenshan County. In non-karst areas, the SOC content in the topsoil and deep soil was 20.88 and 6.12 g/kg, respectively, which was 27.94% and 32.75% higher (p < 0.01) than that in karst areas. The semi-variogram model showed that the nugget effect value of SOC ranged from 14.62% to 59.93%, indicating that structural factors dominate the spatial differentiation of SOC in Wenshan County. According to the analysis of the geographical detector, temperature and altitude were the main controlling factors affecting SOC in the top soil layer in karst areas. As the temperature decreased and the altitude increased, the SOC content in Wenshan County showed an increasing trend. However, the SOC content in karst areas was generally lower than that in non-karst areas due to their lower altitudes, severe rocky desertification, and relatively poor vegetation growth. For the deep soil, precipitation was the main controlling factor affecting SOC in karst areas. The leaching effect caused by precipitation might combine dissolved calcium with organic matter to form humic acid calcium, promoting the accumulation of SOC in deep soil. In non-karst areas, stratigraphic chronology played a leading role. The soil developed from Permian basalt parent material may have higher soil clay and macro-aggregate contents, which helps to maintain the physical protection and stability of SOC in deep soil.ConclusionThis study will provide a reference for precise assessment of SOC and the regulation of soil carbon pools in southwestern karst region.

Abstract:ObjectiveTo explore the impact of primary forest conversion on soil microbial community diversity, structure and functions, in order to provide a theoretical reference for soil health preservation.MethodsA subtropical typical primary evergreen broad-leaved forest and the adjacently converted conifer plantation, orchards, sloping tillage, and rice paddy were chosen in northwest Hunan Province. We assessed the response of the bacterial and fungal genomic diversity, community structure, and predicted functions to primary forest conversion.ResultsComparing to the primary forest, the bacterial diversity was increased by 29%—34% in cultivated lands, while the fungal diversity was decreased by 42%—49% in the orchards. The response direction and magnitude of soil bacterial and fungal predicted function depended on the specific soil function and converted land-use type. Comparing to the primary forest, the relative abundance of global and overview maps, carbohydrate metabolism, and metabolism of cofactors and vitamins were 9%—25% higher in orchards and croplands, while the relative abundance of membrane transport, signal transduction, cellular community-prokaryotes were 11%—27% lower in orchards and croplands. In sloping farmland soil, the relative abundance of endophyte-litter saprotroph-soil saprotroph were 32%—42% lower than those in the primary forest, while the animal pathogen and plant pathogen were 10%—397% higher than those in the primary forest. There was no significant difference in > 50% of the relative abundance of predicted microbial functions between the primary forest and plantations. The predicted bacterial functions are mainly regulated by soil moisture and labile organic C content, whereas the predicted fungal functions are mainly regulated by soil pH, quantity of labile organic C, and nutrient availability.ConclusionThis study suggests that the conversion of primary evergreen broad-leaved forest to Cunninghamia lanceolata plantation is relatively conducive to the maintenance of soil health and functional potential, whereas the conversion to sloping farmland can increase the risk of soil-borne diseases on crops. Our findings provide a theoretical basis for predicting regional soil health evolution and rational land planning.

Abstract:ObjectiveControlled release of potassium chloride can achieve slow release of potassium ions synchronized with crop absorption, while ensuring the effectiveness of potassium ions in the soil, meeting the demand for potassium in the later stage of crop growth, and significantly improving the utilization rate of potassium fertilizer. Exploring the effects of long-term application of controlled-release of potassium chloride and its mixed fertilizers on maize yield and quality, providing technical support for achieving high-quality maize production.MethodsBased on the long-term field experiment of controlled release potassium chloride applied to summer maize (Zea mays L., Zhengdan 958) (started in 2014), six treatments were set up: no potassium fertilizer (CK), constant ordinary potassium chloride (K), constant polyurethane coated potassium chloride (CRK1), 1/3 potassium reduction polyurethane coated potassium chloride (CRK2), constant mixed potassium chloride (BBF1) and 1/3 potassium reduction mixed potassium chloride (BBF2). Relevant indicators such as maize growth, soil potassium supply level, potassium uptake capacity, photosynthesis, etc. were measured during the tasseling stage, and relevant indicators such as maize quality and agronomic benefits were determined during the maturity stage.Results1) Compared with K treatment, CRK1, BBF1, CRK2, and BBF2 showed an increase in yield of 9.82%, 12.06%, 7.13% and 10.68%, respectively. The aboveground biomass increased by 9.22%, 10.44%, 4.16% and 6.09%, respectively, and the economic benefits increased by 16.29%, 28.37%, 14.15% and 21.12%, respectively. 2) The potassium ion content in CRK1 and BBF1 increased by 19.93% and 13.89% respectively compared to K treatment; The chlorophyll SPAD values of CRK1 and BBF2 increased by 7.32% and 6.59% compared to K treatment; The leaf area index LAI value of CRK1 increased by 7.04% compared to K; The net photosynthetic rate of CRK1 and CRK2 increased by 18.58% and 18.66% compared to K. 3) Compared with K treatment, the starch content of CRK1, BBF1, CRK2, and BBF2 increased by 4.27%, 2.51%, 9.32% and 7.16%, respectively, while the oil content increased by 5.65%, 3.11%, 6.63% and 5.92%, respectively; The crude protein content of CRK1 and CRK2 increased by 4.23% and 1.06% respectively compared to K treatment. Compared with K treatment, CRK1, BBF1, CRK2, and BBF2 increased starch production by 14.73%, 19.10%, 17.56% and 18.96%, crude protein production by 14.47%, 14.04%, 8.27% and 8.03%, and oil production by 16.03%, 19.67%, 14.27% and 17.23%, respectively.ConclusionControlled release potassium chloride can meet the potassium requirements for maize growth and quality formation, improve maize growth, optimize maize grain quality traits, and significantly improve maize yield and potassium fertilizer utilization efficiency when mixed with ordinary potassium chloride. It also reduces fertilizer input costs and achieves the goal of reducing production and quality.

Abstract:ObjectiveSoil physical crusting is a common obstructive phenomenon on exposed surfaces, it can lead to shrinkage cracks as the soil dries, thus directly affecting soil moisture retention and utilization. This study aimed to clarify the development patterns of cracks in physical crusts.MethodsArtificial rainfall was employed to simulate the formation of different types of physical crusts, followed by crack formation during the drying process. Parameters such as crack area, perimeter, length, and width were measured using a paraffin filling method, the geometric characteristics and spatial variations of cracks in depositional crusts (DC) and structural crusts (SC) under different conditions were quantitatively analyzed.ResultsCracks in depositional crusts (DC) exhibited significantly higher geometric parameters compared to those in structural crusts (SC). With increasing rainfall duration, the crack shape coefficient and density decreased, while the average crack width increased. Three types of lateral shrinkage cracks were identified, including penetrating shrinkage (PS), interlocking shrinkage (IS), and suspended shrinkage (SS). As rainfall duration increased, the proportion of PS increased, while IS and SS proportions decreased. As soil depth increased, cracks in depositional crusts displayed a stepped decrease and a brief increase under different rainfall durations, while cracks in structural crusts showed an initial sharp decrease followed by a gradual decline.ConclusionThe type of crust and rainfall duration are crucial factors influencing crack development. This study highlights the impact of crusting on crack formation, suggesting timely field management practices to modify water infiltration and evaporation, and can provide a technical support for effective field management.

Abstract:ObjectiveTo explore the correlation between land use ecological risk and carbon storage, in order to improve the regional ecological risk prevention and carbon sequestration capabilities, so as to effectively guide the formulation of environmental management policies.MethodsThe landscape pattern index, PLUS and InVEST models were used to analyze and predict the spatial and temporal changes of land use ecological risk and carbon storage in Yunnan Province under the scenarios of natural development, economic development, and ecological protection. Spearman correlation analysis and spatial autocorrelation analysis were used to explore the correlation characteristics.Results1) Land use in Yunnan Province is dominated by forest land, which exceeded 57% of the total area. 2) From 2000 to 2020, the ecological risk in Yunnan Province decreased slowly, with lower and medium-risk areas exceeding 50%, the spatial distribution remained relatively stable, the change of risk mainly occurred between adjacent levels, and the high-level risk area transferred to the low-level risk area by 39 675.06 km². 3) Carbon storage in Yunnan Province initially increased and then decreased, with a total reduction of 2.257×10⁷ t from 2000 to 2020. Forest land contributed the most to carbon storage, while large-scale conversion of cropland, grassland, and forest land into construction land was the main reason for the reduction in carbon storage. 4) The ecological risk and carbon storage of Yunnan Province would decrease under all three scenarios in 2030. Under the ecological protection scenario, forest land area would increase by 895.83 km² compared to 2020, high and higher ecological risks would significantly decrease, and the reduction in carbon storage would be suppressed, indicating that this is the optimal scenario for the future development of Yunnan Province. 5) Ecological risk and carbon storage in the study area were negatively correlated, with spatial distribution mainly characterized by low-high and high-low aggregations.ConclusionThe study provides various recommendations based on the spatial aggregation characteristics of ecological risk and carbon storage in Yunnan Province, offering a scientific basis for preventing ecological risks and enhancing carbon storage in the region.

Abstract:ObjectiveDegradation of purple soil and water loss is serious, and it is difficult to increase and sequester carbon in the soil. The aim of the study was to explore the impact of carbon source addition on carbon sequestration of purple soil sloping farmland.MethodsPurple soil sloping farmland in Sichuan Province was selected as the research object. Six treatments were set up on 10° purple soil slopes, including no fertilization (CK), fertilizer+straw returning (T1), fertilizer+straw biochar (T2), fertilizer+cow dung (T3), fertilizer+organic soil matrix (T4), fertilizer+biochar cow dung and mushroom slag compost (T5), and each treatment was repeated three times. The change characteristics of runoff, sediment and carbon content under rainfall and different carbon sources were analyzed.Results1) Rainfall > 30 mm and short-term heavy rainfall (16.1 mm/h) could lead to surface runoff. The addition of carbon sources notably decreased surface runoff. In comparison with CK, the runoff reduction benefits of T2, T3, and T5 reached 38.64%, 38.61%, and 62.95%, respectively. The sediment erosion in different treatments was observed to follow the order of T1 > T4 > CK > T2 > T3 > T5, with the highest reduction being 58.99% compared to CK. 2) The loss of organic carbon through surface runoff was primarily attributed to sediment organic carbon, which accounted for 67.47%—90.43% of the total organic carbon loss. T2, T3, and T5 were effective in reducing the transport of organic carbon, resulting in a total organic carbon loss reduction of 21.74%, 19.40%, and 49.28%, respectively, compared to CK. Furthermore, the carbon fractions of T5, including dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), dissolved total carbon (DTC), and sediment organic carbon, exhibited a reduction in transport fluxes by 70.88%, 70.92%, 37.52% and 60.07%, respectively, compared to CK. 3) PLS-PM showed that the carbon sequestration of soil organic carbon was influenced to varying degrees by rainfall characteristics, soil physicochemical properties, and the addition of different carbon sources.ConclusionCarbon source addition (T2, T3, T5) can reduce the total amount of organic carbon loss. T5 can increase organic carbon sequestration; T2 and T3 can reduce the loss of each carbon component of surface runoff, but also reduce organic carbon sequestration. Addition of carbon source can increase carbon content and reduce carbon transport, but reduce carbon sequestration. The results need to be verified by long-term experiments. This study is of significant importance for enhancing the fertility of purple soil, maintaining soil carbon balance, and reducing soil carbon loss.

Abstract:ObjectiveThe contents of soil carbon (C), nitrogen (N) and phosphorus (P) along with their stoichiometric ratios are varied due to the varying nutrient uptake and utilization strategies among plantations of various tree species, which in turn can affect soil microbial activity. However, whether soil microorganisms adapt to these changes by adjusting their biomass and extracellular enzyme stoichiometric ratios remains uncertain. This study aims to explore the effects of plantations of various tree species on soil-microbe-exoenzyme C∶N∶P stoichiometric ratios and to investigate the correlations among soil-microbe-exoenzyme stoichiometry.MethodsAn investigation into the contents of C, N and P, as well as microbial biomass C (C_mic), N (N_mic), and P (P_mic) was conducted, and the activities of C-(β-1, 4-glucosidase+β-D-cellosidase, BG+CBH), N-(β-1, 4-N-acetylglucosaminidase, NAG), and P-(acid phosphatase, ACP) acquiring extracellular enzymes for microorganisms at 0—40 cm depth in four native tree species plantations were determined. These plantations included conifers Pinus massoniana, deciduous broad-leaved Liquidambar formosana, Devergreen broad-leaved Schima superba and Elaeocarpus decipiens located in the hilly region of central Hunan Province and shared a common soil development and management history.Results1) Plantations of different tree species significantly affected soil C, N, P contents, microbial biomass, extracellular enzyme activity; C_mic∶N_mic∶P_mic and EEA_C∶N∶P. C_mic∶P_mic ratios in P. massoniana plantations and L. formosana plantations were significantly higher than those in S. superba plantations and E. decipiens plantations, indicating that microorganisms competed with plants for soil available P. The utilization rate of soil P was low, especially in L. formosana plantations. NAG and EEA_N∶P in S. superba plantations were the highest, suggesting that microorganism were obviously limited by N there. ACP in E. decipiens plantations was higher, EEA_C∶N and EEA_C∶P were also higher than those in plantations of other tree species, while EEA_N∶P was the lowest, indicating that microorganisms were most restricted by C and P there. 2) There was no significant correlation between soil C∶N∶P and microbial biomass, extracellular enzyme C∶N∶P, while only C_mic∶N_mic and EEA_C∶N, C_mic∶P_mic and EEA_C∶P showed significant negative correlation, indicating that there was no covariance between soil C∶N∶P and microbial biomass C∶N∶P. There was a significantly positive correlation between soil C_∶N_∶P and C_∶P_imb, a significantly negative correlation between C_mic∶N_mic∶P_mic and C∶N∶P_imb, and a significantly positive correlation between C∶N_imb and EEA_C∶N, which confirmed the influence of C, N and P differences between soil and microorganisms on the stoichiometric ratios of extracellular enzymes. 3) Existing biomass of the litter layer had significant effects on soil C, N, P contents, P_mic, C_mic∶P_mic, N_mic∶P_mic, BG+CBH, NAG, and EEA_C∶P.ConclusionBy influencing the contents of soil C, N and P, plantations composed of different tree species can affect microbial biomass and extracellular enzyme activities. Soil microorganisms can adapt to diverse nutrient limitations by regulating their biomass C∶N∶P ratios and synthesizing specific extracellular enzymes. The results substantiate the microbial resource allocation theory.

Abstract:ObjectiveCynodon dactylon is an important component and the dominant species in the ecosystem of the water-level fluctuation zone (WLFZ) of the Three Gorges Reservoir, the largest hydropower project in the word. Investigation on the spatial distribution patterns and correlations of nutrient and stoichiometric characteristics between C. dactylon and its periradical soil is of significant importance in comprehending nutrient cycling as well as species adaptation features within the WLFZ.MethodsA field investigation of C. dactylon and its periradical soil across 16 sections in the WLFZ of the Three Gorges Reservoir Area from Banan to Yichang was conducted. The carbon, nitrogen, and phosphorus contents in plant organs (roots, stems and leaves) and soil were analyzed to explore the spatial heterogeneity and interrelationships of the ecological stoichiometric characteristics between C. dactylon and soil.Results1) The soil in the WLFZ associated with C. dactylon demonstrated a distinct "nitrogen-poor and phosphorus-rich" characteristic with significant spatial variations in nutrient contents and stoichiometric ratios. Specifically, soil organic carbon, total nitrogen, total phosphorus, C/N ratio, and C/P ratio exhibited a consistent increase from the upstream to the downstream sections, while N/P ratio was relatively stable. 2) From the upstream to the downstream of WLFZ, carbon contents in various organs of C. dactylon exhibited a decreasing trend, while nitrogen and phosphorus contents showed significant increasing patterns, likely due to intensified sedimentation and the resultant higher soil nutrient supply levels in the downstream WLFZ with the prolonged flooding time. Notably, nitrogen content in the leaves demonstrated a degree of spatial stability, suggesting that C. dactylon could absorb nitrogen efficiently and meet its leaf nitrogen requirements preferentially under nitrogen-deficient conditions. 3) Generally low variations in the stoichiometric ratios in organs of C. dactylon were found. However, the variability in C/N and C/P ratios in roots and stems were slightly stronger than that in leaves, suggesting that C. dactylon has evolved a strategy for maintaining stable physiological functions in leaves. 4) There were significant correlations of the nutrient contents between C. dactylon and soil, with the nitrogen supply of soil being the key factor influencing the variation of nutrient contents in C. dactylon. The correlations of stoichiometric ratios between C. dactylon and soil were relatively weak. 5) C. dactylon in the WFLZ generally exhibited strong homeostasis with the homeostasis index decreasing from the upstream to the downstream.ConclusionIn the context of changing water inundation patterns, the nutrient contents in C. dactylon and soil exhibit significant spatial variations and cooperative association, implying that the spatial evolution of soil nutrients has a profound impact on the ecological stoichiometric characteristics of C. dactylon. C. dactylon exhibits limited spatial differentiation in stoichiometry, indicating its strong adaptability to the heterogeneous soil conditions through adjustments in nutrient demand strategy. The feedback relationships of stoichiometry between C. dactylon and soil may exhibit instability under periodic waterlogging stress in WFLZ.

Abstract:ObjectiveThe Yellow River Delta, a typical ecological fragile area, faces prominent landscape ecological risk (LER) due to multiple factors. Systematic understanding of landscape risk is crucial for optimizing landscape patterns and effectively addressing ecological challenges.MethodsTaking Dongying, a typical city of the Yellow River Delta, as the study area to construct an assessment framework, which consists of two parts, one containing the ecosystem service value and the other the probability of landscape ecological damage in terms of 'stress-vulnerability-resilience'. The ESDA and Geographic detector were used to explore the spatial heterogeneity and influencing factors of LER at the grid scale.Results1) The average value of LER in Dongying was 0.15, generally showed a spatial pattern of high in the north and east, and low in the middle and southwest. The total value of ecosystem services was about 3 175.99 billion yuan, Which was lower than the GDP of that year, and the economic growth was unsustainable. The ecosystem service value showed a pattern of gradual diminution from the north and eastern coast to the southwest part. The probability of ecological damage was 0.43, showing a pattern of staggered distribution of high and low in the north and east, relatively balanced in the center and southwest. 2) The LER showed a significant clustering in spatial distribution, with a global Moran's I index of 0.747. In terms of agglomeration zoning, the HH risk agglomeration area accounted for 32.48% of the area of the risk zone, which was mainly distributed in the continuous distribution zone formed by the coastal zone in the north and east of Dongying. 3) The LER of Dongying was mainly dominated by factors of socio-economic foundation and environmental location conditions. In the citywide area, the determinant degree of coastline distance was 0.43, which was the primary factor dominating the urban LER. In contrast, in the urban area, the determinant degreee of population density was 0.38, which was the primary factor influencing the urban LER.ConclusionsThis study enriches the LER assessment method theoretically, and provides an empirical support for ecological protection and risk management in the Yellow River Delta.

Abstract:ObjectiveTo investigate the effects of combined application of biochar and microbial fertilizer on greenhouse gas emissions and sunflower yield in saline-alkali soil under plastic film mulching and drip irrigation.MethodsField experiments were conducted in saline-alkali soil in the Hetao Irrigation Area of Inner Mongolia, with different combinations of biochar (0, 7.5, 15 t/hm²) and microbial fertilizer (0, 112.5, 225 kg/hm²). Greenhouse gas emissions were monitored using static chamber-gas chromatography method. Changes in soil physicochemical properties, global warming potential (GWP), and sunflower yield were analyzed.Results1) Compared with the control (0 t/hm² biochar+0 kg/hm² microbial fertilizer), the treatment of 7.5 t/hm² biochar+225 kg/hm² microbial fertilizer increased soil organic carbon, available phosphorus, and available potassium contents by 63.9%, 155.7%, and 46.8%, respectively. 2) Compared to the control, the treatment with 7.5 t/hm² biochar +225 kg/hm² microbial fertilizer reduced cumulative CO₂ emissions from 4 373 kg/hm² to -394.3 kg/hm², increased cumulative CH₄ emissions from -0.08 kg/hm² to 0.1 kg/hm², reduced cumulative N₂O emissions from 0.23 kg/hm² to -0.09 kg/hm², and decreased GWP from 4 438.3 kg/hm² to -417.2 kg/hm². 3) Under the treatment of 15 t/hm² biochar+225 kg/hm² microbial fertilizer, sunflower yield reached 4 137.5 kg/hm², which was increased by 39.4% compared with the control (2 968 kg/hm²). 4) Mantel test analysis revealed that sunflower yield was extremely significantly correlated with soil physicochemical properties (p < 0.01); CO₂ emissions were significantly correlated with ammonium-nitrogen content and soil moisture, N₂O emissions were significantly correlated with nitrate-nitrogen content, and CH₄ emissions were extremely significantly correlated with nitrate-nitrogen content (p < 0.05).ConclusionCombined application of biochar and microbial fertilizer can simultaneously improve saline-alkali soil, reduce greenhouse gas emissions, and increase sunflower yield, with 7.5 t/hm² biochar+225 kg/hm² microbial fertilizer being the optimal combination. This technique provides a new strategy for reducing greenhouse gas emissions in agricultural production and increasing crop yields on saline-alkali soils.

Abstract:ObjectiveTo explore the differences in precipitation characteristics for multisource precipitation products and their applicability for runoff simulation in an alpine basin on the Tianshan Mountains.MethodsA comparative analysis of the spatiotemporal characteristics of precipitation was conducted in the upper reaches of the Manas River Basin, based on the datasets CN05.1, GPM, AIMERG, CMFD and ERA5. Subsequently, the accuracy of different products was evaluated based on observed precipitation, and their applicabilities for runoff simulation were assessed by means of HBV hydrological model.ResultsThe spatial pattern for all the precipitation products was characterized by a first increase and then a decrease from the north to south, whereas only AIMERG and CMFD were able to display higher precipitation in the glacier area. Consistent seasonal variation were detected, but large differences in summer precipitation were shown. In summer, ERA5 was twice as much as CN05.1, and GPM was lower than the other precipitation products. GPM underestimated the monthly precipitation, especially in winter and spring (64%—76%). While the monthly precipitation was overestimated by CMFD, ERA5 and AIMERG. The overestimation of ERA5 was the most serious, especially in summer and autumn (134%—206%), and CMFD slightly overestimated the monthly precipitation. AIMERG had a higher correlation with the observed monthly precipitation and greater critical success index in both rainy season and the non-rainy season. AIMERG, CMFD and CN05.1 had the greatest ability to reproduce daily runoff, with a higher NSE (0.81—0.82) and lower relative error (< 6%). Moreover, the former two products showed a better performance in reproducing extreme runoff when compared with CN05.1.ConclusionAIMERG and CMFD show great potential in runoff simulation of the upper Manas River. The results can serve as data references for runoff simulation and soil erosion prevention research in the Tianshan region, where meteorological data are limited.

Abstract:ObjectiveTo investigate the combined effect of crop cover and crop management practices on preventing soil loss and improving the accuracy of C-factor estimation.MethodsSix millet plots with different treatments, i. e., crop plot (C1), crop-roughness plot (C2), crop-crust plot (C3), bare plot (B1), roughness plot (B2), and crust plot(B3), were established and the soil loss at four growth stage was determined under simulated rainfall. The C factor was calculated using soil loss ratio (SLR). The major factors affecting SLR were also analyzed and their correlations with SLR were then regressed through numerical simulation using MATLAB. Subsequently, the SLR estimation models designed for soil erosion prediction on the Loess Plateau could be built. Finally, the C factor could be calculated using the proposed SLR estimation model combined with the distribution curve of rainfall erosivity.ResultsSurface roughness and soil crust could reduce soil loss in crop plot. Compared with SLR_crop, SLR_{crop-roughness} and SLR_crop-crust were on average 21.00% and 16.50% lower, respectively. The model formulas of crop plot, crop-roughness plot, crop-crust plot were obtained, through validating by field soil and water loss data conducted in Chunhua County, the model formulas could achieve accurate prediction. The estimated C values for the whole growth stage were 0.30, 0.25 and 0.25, respectively, with the Nash coefficients being 0.96, 0.87 and 0.75, respectively.ConclusionThe results can provide some insights for estimating C values at national scales.

Abstract:ObjectiveTo reveal the durability of solidified loess slope protection in long-term service.MethodsUnder the condition of dry-wet cycles, direct shear, permeability mechanical tests of solidified loess were carried out to study the evolution law of the macro-properties of stabilized loess, and the damage law of dry-wet cycles on the morphology of the microstructure was analyzed by using scanning electron microscopy and image processing technology. The micro-mechanism of improvement of the dry-wet cycle durability of the macro-properties of loess by biological glue was discussed, and the macro-micro-evolution feature function was established based on the macro-performance index and the micro-structure view parameters to describe the numerical response relationship between the macro-properties and the micro-structure under the dry-wet cycle conditions.ResultsThe biological glue inhibited the deterioration of mechanical properties of solidified loess, and the inhibitive effect was positively correlated with the content of biological glue; the change of permeability of solidified loess was increased by biological glue, and the change amplitude was negatively correlated with the content of biological glue. The dry-wet cycles resulted in the failure of loess cementation, particle damage and pore increase. The biological glue enhanced the loess cementation, slowed down the particle damage and changed the pore development pattern. More than 95% of the predicted points fell within the mean square error line. The addition of biological glue could improve the durability of the macroscopic properties of loess under dry-wet cycles. The sensitivity analysis of the characteristic function showed that the porosity had the greatest influence on the mechanical properties, and the large porosity with pore size > 32 μm had the greatest influence on the permeability.ConclusionThe research findings can provide a theoretical basis for the engineering application of biological glue for the technology of soil solidification and slope protection and subsequent improvement of the technology.

Abstract:ObjectiveAs a key parameter in the simulation study of ecosystem water cycle process, rapid dynamic simulation of leaf area index (LAI) can solve the limitation that the coupled soil water-vapor-heat-air model STEMMUS (simultaneous transfer of energy, mass and momentum in unsaturated soil) can only use fixed or measured LAI as an input parameter.MethodsIn this study, the "plant leaf area development sub-module" in EPIC model was coupled with the STEMMUS model, and the model was calibrated and validated using the measured transpiration of apple trees, soil moisture and soil temperature data under the growth conditions of apple trees in the mountain apple experimental demonstration base of Zizhou County in 2019 and 2020, so as to evaluate the applicability of the coupled model on the Loess Plateau.ResultsBy optimizing the plant growth parameters, the coupled leaf area development sub-module of the STEMMUS model significantly improved the simulation accuracy of the transpiration and water consumption process of apple trees, with the normalized root mean square error (NRMSE) of the calibration and validation years decreasing from 40.2% and 61.9% in the Original model to 30.0% and 33.2% in the coupled model, respectively, and the mean absolute error (MAE) decreasing from 0.52 and 0.64 mm/d to 0.42 and 0.38 mm/d, respectively. Meanwhile, the coupled model could better simulate the soil hydrothermal dynamic processes in apple orchards, and the NRMSE of simulated soil water content and soil temperature during the calibrated period and validation period ranged from 1.4% to 32.9% and 2.9% to 9.5%, respectively, and the MAE ranged from 0.13 to 4.26 cm³/cm³ and 0.34 to 1.49 ℃, respectively.ConclusionThe high agreement between the simulated and measured values indicates that the coupled model can accurately describe the dynamic growth process of apple tree leaf area and the ecohydrological process of orchard on the Loess Plateau, and this study can provide technical support for the research of the ecohydrological process of orchard in loess area.

Abstract:ObjectiveTo explore the effects of hydropower stations on the temporal and spatial changes of vegetation, clarify the response relationship of vegetation changes to hydropower station construction and climate factors, and provide a reliable scientific basis for regional sustainable development and sustainable operation of hydropower stations.MethodsNormalized vegetation index (NDVI) was used to reflect the vegetation change. Google Earth Engine (GEE) was used as the computing platform, coupled with ModTrendr algorithm, Theil Sen-MK, contribution degree analysis and partial correlation analysis methods to explore the effects of hydropower stations in the middle reaches of the Jinsha River on the spatial and temporal changes of vegetation during 2000—2022, and the effects of climate it were analyzed.Results1) The negative mutations were concentrated from 2011 to 2014, and the mutation area was concentrated in the catchment area. The forward mutation was concentrated in 2015 and 2017, and the mutation area was concentrated within the 5 km buffer zone of the riverbank. The time for vegetation to produce positive response was 1—4 years after the water was impounded, and the mutation intensity gradually weakened along the riverbank. 2) The vegetation NDVI around each hydropower station presented an overall upward trend (0.000 2—0.002 8/a), and an upward (gentle)-downward-upward trend before, during and after hydropower station construction. 3) Regional vegetation change was mainly caused by the joint action of human activities (hydropower station construction) and climate change, and the explanation degree was 69.12%. The contribution of human activities was much higher than that of climate change. 4) The partial correlation coefficients of temperature, precipitation and NDVI were -0.28 and -0.29, respectively. The partial correlation coefficients of temperature and precipitation differed greatly in different stages of hydropower stations, indicating that hydropower stations would affect regional climate.ConclusionHydropower stations have a negative impact on vegetation during construction and a positive impact on vegetation after operation. The impact of hydropower station construction on vegetation is higher than that of climate change, and the construction of hydropower stations may affect local climate, leading to a decrease in the overall correlation between temperature and precipitation and vegetation NDVI.

Abstract:ObjectiveTo establish an ecological security evaluation index system tailored to the distinctive landscapes of typical karst mountainous regions in Southwest China, to conduct a comprehensive study on the landscape ecological security evaluation and governance in Wenshan City, in order to provide a scientific foundation for regional ecological protection and sustainable development.MethodsBased on the landscape characteristics of karst mountainous areas, a landscape ecological security evaluation index system consisting of target, comprehensive, project, and indicator layers was established. Utilizing the geometric mean and the InVEST model, two comprehensive layers, i. e. ecological sensitivity and system service importance were evaluated. Subsequently, the ecological security target layer, delineated ecological functional zones, and proposed differentiated governance measures were evaluated.Results1) In Wenshan City, the sensitivity to soil erosion, geological disasters, and rocky desertification primarily fell into mild and moderate categories, comprising 48.83%—59.13% of the total area, with the least area being extremely sensitive, accounting for 5.92%—7.10%. 2) In Wenshan City, the significance of water conservation and biodiversity protection predominantly fell into mild and moderate categories, representing 67.42%—80.31% of the total area. The significance of soil conservation was primarily deemed unimportant, with the unimportant category accounting for 55.30% of the total area, and the extremely important category accounting for merely 2.06%—5.22%. 3) The overall level of landscape ecological security in Wenshan City was low, with merely 4.82% and 16.74% belonging to the first and second levels, respectively, and predominantly concentrated in the Wenshan Laojunshan Nature Reserve. The third-level area occupied the largest proportion, reaching up to 30.43%, and predominantly distributed in Dehou Town, Hongdian Township, Binglie Township, and other regions. The proportions of the fourth and fifth levels were 13.59% and 25.62% respectively, and widely spread across Binglie Township, Dongshan Township, Zhuilijie Town, and Kaihua Town. 4) The ecological function zones of Wenshan City were divided into four categories, i. e. the rocky desertification ecological function restoration zone, the urban ecological coordination construction zone, the biodiversity function protection zone, and the water conservation and soil conservation function improvement zone. Four governance measures and suggestions were proposed to address each regional ecological issue.ConclusionThe study integrates ecological sensitivity and ecosystem service importance to comprehensively evaluate the landscape ecological security of Wenshan City, and conducts zoning governance, the results can provide basic theoretical support for the construction of ecological security patterns, regional ecological protection, and sustainable development in the karst mountainous areas of Southwest China.

Abstract:ObjectiveTo explore the morphological characteristics and spatial evolution patterns of rural settlements in the karst depression rocky desertification area.MethodsThe distribution of rural settlements under the scenarios of economic development, natural development, and ecological protection by 2035 was predicted using the PLUS model. The morphological characteristics of rural settlements were identified through Morphological Spatial Pattern Analysis (MSPA), while the past, present, and future morphological characteristics and spatial evolution patterns of rural settlements were analyzed using landscape pattern indices, landscape comprehensive dynamics, and the Ripley K function method.Results1) There was an increasing trend in the area of rural settlements from 1990 to 2022, with the area expanding by 6.09 km² and the number of settlements increasing from 366 to 1 253. The core and edge were identified as the dominant types of rural settlements in the study area, with their areas increasing by 1.90 and 1.51 km², respectively, primarily concentrated in the central part of the study area. In contrast, isolated patches and branches, which increased by 1.07 and 1.15 km² respectively, were mainly distributed in the northern and northeastern parts. 2) The complexity, richness, and fragmentation of rural settlement types generally showed an increasing trend. The development of rural settlement types was most gradual from 1990 to 2000 and most intense from 2010 to 2022, with the expansion primarily occurring in Xingjie Village, Laojie Village, and their surrounding areas. Across the study scale, rural settlement types exhibited a clustering trend, which weakened as the spatial scale increased, and the urbanization process led to a reduction at spatial scale. 3) Under all three scenarios, the area of rural settlements showed an increasing trend, with the areas reaching 11.42, 7.68 and 9.14 km², respectively. The core type was identified as the dominant type in the study area, with its area increasing by 4.02, 2.60 and 3.14 km², respectively. Rural settlement types exhibited a clustering distribution pattern across spatial scales, with the ecological protection scenario restricting the expansion of rural settlements.ConclusionRural settlements in the study area are in a rapid development stage, with expansion mainly occurring in the core areas. The expansion of isolated patches has increased the complexity of the spatial distribution of rural settlements, and during the urbanization process, rural settlements have gradually concentrated within smaller spatial scales.

Abstract:ObjectiveTo explore the spatial and temporal evolution of soil erosion in Anshun City, southwest karst region, as well as the main controlling factors of soil erosion, and to master the soil erosion situation in the region, in order to help the management of rocky desertification and soil and water resources management in the region.MethodsThe optimised RUSLE model was used to estimate soil erosion in Anshun City from 2005 to 2020, while the Random Forest Model (RF) was used to reveal the driving factors of soil erosion, and to estimate the effects of the interactions between the driving factors on soil erosion in Anshun City from 2005 to 2020.Results1) From 2005 to 2020, soil erosion in Anshun City generally showed that low intensity soil erosion was distributed in the central, southeastern and eastern regions, while high intensity soil erosion was distributed in the northern and southwestern regions. In terms of time, soil erosion in Anshun City as a whole showed a trend of improvement, soil erosion grade in most of the areas mainly transferred from high to micro intensity erosion, but the erosion exacerbated in some areas. 2) Rocky desertification had a greater impact on soil erosion in Anshun City, and the change trend of rocky desertification was consistent with that of soil erosion. Soil erosion increased first and then decreased with the increase of rocky desertification intensity. 3) The most important land use types in Anshun City where soil erosion occured were forest land, arable land and grassland, and the overall rate of soil erosion was in the order of forest land < grassland < arable land, with cropland having a higher risk of soil and water runoff. 4) The analysis of the driving factors of soil erosion showed that that the vegetation cover and management factor, the factor of soil and water conservation measures and the intensity of rock desertification were the main driving factors. The results of the interactions between the driving factors showed that the interaction between the vegetation cover and management factors and the soil and water conservation measures were the dominant factors.ConclusionSoil erosion intensity in Anshun City showed an overall trend of improvement from 2005 to 2020, but there was an increase in erosion in some areas, with high intensity soil erosion being mainly located in the north and southwest areas with high human activity. Vegetation cover, land use and rock desertification intensity are the main influencing factors of soil erosion, while rock desertification control and soil and water conservation measures can better increase vegetation cover and improve soil erosion in Anshun City.

Abstract:ObjectiveTo investigate the spatial and temporal variations and the driving factors of the vegetation cover in Panzhihua City, and to provide a theoretical basis for Panzhihua City to formulate regional ecological environmental protection programs and maintain regional ecological balance.MethodsBased on Landsat-EVI data, in combination with natural and socio-economic data, the characteristics and driving factors of the vegetation cover in Panzhihua City during the period of 1990—2020 were analyzed with the help of dimidiate pixel model, Theil-Sen Median trend test, partial correlation and optimal parameter geographic detector model.ResultsThe spatial distribution of the vegetation cover (FVC) in Panzhihua City was characterized by 'low in the south and high in the north', with high-grade vegetation cover dominating. The FVC ranged from 0.635—0.792, with the area of degraded area accounting for 17.70% and the area of improved area accounting for 44.97% from 1990 to 2020. The area proportion of areas where FVC was positively correlated with precipitation and air temperature was 61.87% and 57.40%, respectively. Land use type, elevation, and air temperature were the main influencing factors of the spatial differentiation of FVC, with the influence being above 0.20; most of the interactions among the factors were shown to be enhanced, among which, the influence can be increased to 43.00% after the coupling of slope direction and air temperature; the influences of the driving factors on the growth of vegetation in the study area had their appropriate ranges.ConclusionsFrom 1990 to 2020 FVC showed an overall upward trend, but the vegetation degradation was obvious in some areas. In the future, regional vegetation construction should be focused on the terrain distribution pattern and climate change when optimizing the land-use pattern, in order to cope with the challenges of sustainable development of vegetation ecosystems under environmental evolution.