Abstract:[Objective] This study systematically summarized and analyzed the current application status, technical characteristics, and environmental benefits of interlayer construction in soil improvement, nutrient cycling, ecological restoration, and crop management, aiming to provide scientific basis and theoretical support for improving modern agriculture's quality, efficiency, and sustainable development. [Methods] The effects and regulation mechanisms of interlayer construction on soil physical structure, soil water-salt-heat, soil nutrient status, soil enzyme activities, soil microbial properties, and crop productivity were comprehensively addressed. [Results] Interlayer construction could improve soil structure, nutrient content, ecosystem service functions, and agricultural production efficiency, but the responses process to interlayer mode selection and farmland management measures have shown differences. [Conclusion] The critical scientific problems and future development directions that need to be solved in the process of agricultural development and ecological governance were provided. It primarily involves exploring the response mechanism and residual effects of water and salt regulation, nutrient release, and habitat succession on the interlayer-soil-microbial-crop system in depth. This also includes developing and integrating cost-effective and practical interlayer laying technology and supporting equipment, as well as screening and optimizing key technologies and operational parameters for interlayer construction suitable for various climate conditions, soil textures, crop layouts, and farmland management methods. Furthermore, it aims to expand and validate the practical application effects and successful pathways of interlayer construction technology. Within the framework of the dual carbon development pattern and multiple strategic overlapping context, the focus and direction of future research will be on innovating and technologically transforming new interlayer materials based on the efficient utilization of solid waste resources.

Abstract:[Objective] To elucidate the responses of surface runoff, subsurface runoff, and underground runoff hydrological pathways to slope in maize sloping farmland in Karst regions. [Methods] Taking the karst maize slope in Guizhou Province as the research object, the artificial simulated rainfall test method was used to investigate the effects of different slopes (5°, 10°, 15°, 20°, 25°) on the runoff and sediment yield patterns of various hydrological pathways under the same rainfall intensity (60 mm/h). [Results] (1) Surface runoff and sediment yield showed a very significant positive correlation with slope gradient at the level of 0.01(p＜0.01). The maximum runoff modulus and maximum sediment yield modulus were 0.18 L/(min·m²) and 13.12 g/(min·m²) respectively. Surface sediment yield changed from sheet erosion to rill erosion during the 10~30 min period. (2) The maximum runoff coefficient was 49% when the subsurface runoff was at a moderate slope (15°), and there was a highly significant positive correlation between runoff yield, as well as sediment yieldand slope gradient. Although the correlation between underground runoff or sediment production and slope gradient was not significant, the proportion of underground runoff was still affected the greatest by slope gradient. (3) The total sediment yield on the surface was greater than that in the soil layer and subsurface. The fitting relationship between the three different hydrological paths (surface, soil layer, and subsurface) and slope gradient was surface runoff > interflow > subsurface runoff. [Conclusion] In the maize slope farmland in karst areas, as the slope gradient increases, the soil erosion patterns of different soil layers show inconsistency, and the main form of soil erosion is surface erosion, supplemented by underground leakage. The maize canopy can slow down the evolution of surface soil erosion forms at small slope gradients. The research results can provide theoretical reference for estimating soil erosion in karst maize sloping farmland and maize planting strategies.

Abstract:[Objective] A study on the spatial and temporal patterns of wind erosion climate indices and their responses to atmospheric and oceanic circulation patterns in the Chinese Mollisol region is of great significance for the early warning and prevention of wind erosion. [Methods] Four wind erosion climate indices, including occurrence frequency of ≥ 5 m/s of threshold wind of transporting sand, daily maximum wind velocity, daily extreme wind velocity and wind erosion climatic erosivity, were selected to address the spatial and temporal patterns of wind erosion climate indices in the spring (March-May) of the Chinese Mollisol region from 1960 to 2020 based on the daily wind speed data and meteorological data, and to elucidate the impacts of atmospheric and ocean circulation patterns on these indices. The research methods included the moving average, Mann-Kendall test and multiple wavelet coherence. [Results] The occurrence frequency of ≥ 5 m/s threshold wind speed of transporting sand varied from 5 to 30 times per season, daily maximum wind velocity varied from 6.1 to 8.7 m/s, daily extreme wind velocity varied from 9.8 to 12.2 m/s, and wind erosion climatic erosivity varied from 19.5 to 101.1 in the Chinese Mollisol region form 1960 to 2020. An intermonthly change trend of these four wind erosion climate indices followed by April > May > March. Except for daily extreme wind velocity, there was a significant decreasing trend of the other three indices from 1960 to 2020 with a significant abrupt change around 1990, but a noticeable upward trend of these indices was observed after 2014. The spatial distribution of wind erosion climate indices in the Chinese Mollisol region showed an increasing and then decreasing trend from the northwest to the southeast, and topography was a crucial factor affecting the distribution of wind erosion climate indices. Moreover, the Asia Polar Vortex Intensity Index (APVII) was the most important circulation pattern affecting wind erosion climate indices, and the Pacific/North American Pattern (PNA) also had a significant impact on wind erosion climate indices. However, there was no significant correlation between the wind erosion climate indices and the superposition of APVII and PNA, while the superpositions of three APVII-PNA-AO patterns had a significant effect on the occurrence frequency of the threshold wind of transporting sand. Overall, after 2014, there was a rapid increasing trend in the wind erosion climate indices in the Chinese Mollisol region, and both APVII and PNA circulation patterns had significant impacts on the wind erosion climate indices. [Conclusion] The factors that influenced the spatial and temporal patterns of wind erosion climate indices in the Chinese Mollisol region include wind velocity, topography and atmospheric-oceanic circulation patterns, etc. Attention should be paid to the potential wind erosion hazards caused by the enhancement of wind erosion dynamics after 2014.

Abstract:[Objective] To investigate the characteristics of soil disintegration under different vegetation restoration measures in degraded land of Pinus massoniana, compare the improvement of soil disintegration in severely degraded P. massoniana land in granite red soil area of Southern China by different vegetation restoration measures, and reveal the interactions between the influencing factors of soil disintegration in granite red soil area in Southern China. [Methods] In this study, a severely degraded land of P. massoniana in Changting County was selected as the research area, and a degraded land of P. massoniana was used as the control group (CK). Three vegetation restoration measures, including closure management (E1), whole slope sowing grass (E2) and tree-shrub-grass ditch model (E3), were set as the experimental groups. Correlation analysis, principal component analysis and path analysis were used to study the disintegration of surface soil in four plots. [Results] (1) There were significant differences in soil anti-erodibility under each measure. Compared with CK, the soil disintegration coefficient of E1, E2 and E3 measures decreased by 16.3%, 52.5% and 67.2%, respectively. The tree-shrub-grass furrow model (E3) was more suitable for the treatment of severely degraded P. massoniana land. (2) Soil organic carbon content, total phosphorus content, available phosphorus content, total potassium content, available potassium content, water content and aggregate characteristics were the main influencing factors of soil disintegration. (3) Among various factors affecting soil disintegration, soil geometric mean diameter (GMD) was the main direct influencing factor and played a dominant controlling role. [Conclusion] The size of soil disintegration characteristics under different vegetation restoration measures follows the order of CK> E1> E2> E3. The soil disintegration characteristics can be maintained at a low level by adopting the tree-shrub-grass furrow management measure. This measure is more effective for soil and water loss control in severely degraded P. massoniana forest in granite red soil area. Soil geometric mean diameter (GMD) is a direct control factor affecting soil disintegration characteristics, and can be used as a preferred index to evaluate soil disintegration characteristics.

Abstract:[Objective] As a typical mode of gravity erosion in the Pisha sandstone area, debris sliding has become a significant source of coarse sand material within gullies, seriously threatening the ecological security of the basin. Clarifying the erosion mechanisms in this region is of great importance for the ecological protection and high-quality development strategy of the Yellow River Basin. [Methods] Using the gully slope system in Inner Mongolia as the study area, field monitoring and three-dimensional laser scanning technology were employed to analyze the spatial and temporal changes in micro-topography and erosion characteristics of the erosion interface under different slope aspects. Additionally, the relationships between these changes and meteorological factors were investigated. [Results] (1) The Pisha sandstone gully slopes exhibited significant debris sliding erosion, with distinct slope aspect differentiation. The average erosion areas of the shady slope and the sunny slope accounted for 43.11% and 45.48% of the total study area, respectively. The erosion intensity on the sunny slope was greater than that on the shady slope, with the variation in surface roughness being more pronounced on the sunny slope. However, the variations in surface relief, surface dissection and elevation variation coefficient were more significant on the shady slope. Slope aspect was a critical topographic factor influencing gravity erosion on gully slopes. (2) There was a highly significant positive correlation (p<0.01) between the retreat rate of gully slopes and surface relief and surface dissection. The correlation between the retreat rate of gully slopes and micro-topographic factors was better for shady slopes (R²=0.721) compared to sunny slopes (R²=0.631). The fitting effect of micro-topographic factors with gully slope retreat rate was superior to that with erosion area and erosion volume. (3) During the period from July to August in the Pisha sandstone area, the importance of meteorological factors affecting the erosion of the shaded slope was temperature>rainfall>solar radiation>relative humidity>wind speed. For the sunny slope, the order was temperature>relative humidity>wind speed>rainfall>solar radiation. The GAM model demonstrated a good explanatory ability for the slope aspect variation in erosion characteristics. [Conclusion] The results of this study provide a theoretical reference for the study of gravity erosion mechanisms and ecological construction in the Pisha Sandstone area.

Abstract:[Objective] Soil erosion is one of the most important ecological and environmental problems in the world. It is of great significance to reveal the coupling mechanism of water and gravity combined erosion by analyzing the water and sediment process of water and gravity combined erosion under different conditions and its synergistic change law with gravel content. [Methods] Two types of soil, with no gravel and gravel content of 40%, were set up. Through the method of artificial simulation of continuous rainfall in the field, the influence of gravel content on soil erosion process and its synergistic change rule under the combined action of water and gravity were discussed. [Results] (1) Gravel-free soil did not produce runoff under two rainfalls. The gravel-containing soil did not produce runoff under the first rainfall, but started to produce runoff at 36 min under the second rainfall. The initial runoff time basically tended to advance with the increase of rainfall times, and the range of variation was 8~36 min. (2) The total runoff of each rainfall in the gravel soil was 8.97, 63.9, 70.8, 79.7 and 127.5 L, respectively. The runoff process in the later stage of each rainfall was basically the same, and the runoff rate decreased gradually. (3) The total sediment yield of each rainfall was 0.26, 10.6, 5.74, 3.15, 9.37 g, the erosion rate of the gravel soil fluctuated greatly under each rainfall, but the overall trend decreased in the later stage of rainfall. (4) Gravity erosion occurred in the non-gravel soil during the second rainfall. The erosion amount was 106.37×10³ cm³, and the deposition amount was 76.28×10³ cm³. Under the third rainfall, a small area of collapse occurred in the middle and lower part of the gravel soil, and the amount of gravity erosion was 6.08×10³ cm³. [Conclusion] The research results can provide a theoretical basis for analyzing the coupling mechanism of water and gravity combined erosion forces.

Abstract:[Objective] In order to reveal the effect of different soil and water conservation measures on reducing runoff and sediment in Ta-pieh Mountains, optimize the allocation mode of soil and water conservation measures in Ta-pieh Mountains. [Methods] Based on the erosion observation data of four runoff plots in Shiqiaopu, Hongan, Yingshan and Tuanfeng, the water and soil conservation benefits under different water and soil conservation measures were compared and analyzed. [Results] (1) There was no obvious benefit of soil and water conservation in normal farming, but the benefit of soil and water conservation was improved under terraced field + tillage mode, and the comprehensive benefit of stone ridge terraced field + peanut-rape was the best, and the reduction rate of soil erosion reached 55%; (2) The allocation mode of biological measures combined with engineering measures has good water and soil conservation benefits, but there are differences in the benefits of runoff and sediment reduction. For example, the benefits of sediment reduction in stone ridge terrace + chestnut were better than those of runoff reduction; (3) Vetiver and vetiver contour hedgerow were the best measures for soil and water conservation in this study, and the comprehensive benefit of vetiver contour hedgerow reached 70%. [Conclusion] Vetiver and vetiver contour hedge are suitable to be popularized in Huanggang and Ta-pieh mountainous areas, and the combination of multiple measures has more advantages than a single measure. The research results can provide reference for regional soil and water conservation measures allocation.

Abstract:[Objective] To investigate the effects and applicability of different intercropping patterns of medicinal herbs on water, soil, and nutrient losses in young oil tea gardens on red soil slopes. [Methods] Runoff plot experiments were carried out in Jiangxi Province, a major province for cultivating traditional Chinese medicinal herbs, with interplanting above-ground harvested medicinal herb of Ai pattern (YA), interplanting below-ground harvested medicinal herb of Yujin + vegetative hedges pattern (YY), traditional conservation measure of straw mulching + moisture furrow pattern (YC), and clean tillage pattern for control (CK). Observation of runoff, sediment, nitrogen and phosphorus losses under natural rainfall events, and comprehensive benefit evaluation of each pattern were carried out. [Results] (1) All conservation measures significantly reduced water, soil, and nutrient losses in young oil tea plantations, except for the clean-tillage mode. Compared with CK, the runoff reduction effects of YA, YC and YY amounted to 15.22%, 67.30% and 64.12%, respectively; the sediment reduction effects amounted to 72.63%, 97.19% and 98.19%, respectively; the decrease in total nitrogen (TN) loss was 57.86%, 96.53% and 95.87%, respectively; and the decrease in total phosphorus (TP) loss was 32.18%, 98.62% and 98.86%, respectively. (2) Under moderate rain, heavy rain and rainstorm, YY pattern all showed good soil and water conservation and nutrient interception effects, with runoff reduction effects and sediment reduction effects ranged from 45.11% to 83.25% and 96.08% to 99.02%, respectively. The nitrogen and phosphorus reduction effects ranged from 83.02% to 99.14% and 88.38% to 99.65%, respectively; whereas YA pattern only had a better nutrient interception effect under moderate and heavy rain, the soil and water conservation effect under heavy rain was not obvious. (3) Based on the TOPSIS model, the comprehensive benefits of the four patterns were evaluated and ranked as YY (0.48)> YC (0.29)> YA (0.23)> CK (0.02). [Conclusion] Below-ground harvesting of medicinal herb Yujin + plant hedge mode is the most economical and effective management measure to control soil erosion and nutrient losses of young oil tea plantation on red soil slope in this experiment. Selecting medicinal herbs with staggered harvesting period and erosion risk period will better utilize the ecological benefits of interplanting medicinal herbs, and can avoid additional nutrient losses of young oil tea plantations.

Abstract:[Objective] To clarify the distribution characteristics and coupling relationship between soil erosion and hydrologic and sediment connectivity in Changchong River Basin, and to provide basis for soil erosion control and soil erosion prevention in this area. [Methods] By using the RUSLE model and introducing the connectivity index (IC) and topographic humidity index (TWI), the distribution characteristics of soil erosion, hydrological and sediment connectivity in the Changchong River Basin in 2021 were quantitatively evaluated by GIS platform. The effects of different slope, land use, elevation and slope direction on soil erosion intensity and hydrologic and sediment connectivity in small catchments were discussed, and the coupling relationship between soil erosion and hydrologic and sediment connectivity was analyzed through spatial autocorrelation. [Results] (1) The average soil erosion modulus in the Changchong River Basin was 380 t/(hm²·a), and the soil erosion intensity was mainly slight erosion, which gradually intensified from north to south. (2) The high hydrological and sediment connectivity is mainly distributed in cultivated land, and the opposite is true in forest and grassland land. The higher value is mainly located in the low-lying flat area with low slope and easy water accumulation, while the lower value is mainly in the steep mountainous area. (3) Topographic factors and land use types significantly affected soil erosion and hydrological and sediment connectivity (p<0.01). The relatively low soil erosion intensity and hydrological and sediment connectivity levels, the higher erosion intensity and connectivity levels accounted for a higher proportion of arable land, but a smaller proportion of woodland and grassland. Among the hydrological and sediment connectivity grades, the proportion of 5° ~ 10° and 10° ~ 15° slope, 90.30 ~ 131.96 and 131.96 ~ 175.34 m elevation area is higher. The higher the grade, the higher the proportion of sunny slope area is. (4) Soil erosion has a significant positive correlation with hydrologic and sediment connectivity, mainly reflected in slope, slope direction, land use and elevation. [Conclusion] Improving the vegetation coverage and dominance of the Changchong River Basin to reduce its hydrologic and sediment connectivity can effectively reduce soil erosion and sediment production, and has an important impact on the ecological environment management, water and sediment control, and scientific prevention and control of soil and water loss in the small watershed.

Abstract:[Objective] To study the effects of vegetation restoration on rainfall infiltration and runoff is of great theoretical and practical value for rational utilization of watershed water resources and ecological construction. [Methods] Taking the Nanxiaohegou Watershed in the Gully Region on the Loess Plateau as the research area, the double-ring infiltration experiments and slope surface simulated rainfall experiments were conducted to analyze the effects of vegetation restoration on infiltration and runoff processes and characteristics on slopes. [Results] (1) Vegetation restoration significantly increased the values of soil infiltration characteristics and capacity, with the order of artificial forest > natural grassland > corn farmland. (2) Compared to bare ground, grassland increased the transformation of rainfall into soil storage, reduced surface runoff, and led to the appearance of multiple layers of interflow. (3) Compared to bare ground, grassland showed more rapid changes in soil moisture content, richer runoff components, and less runoff volume. (4) When the intensity of rainfall on bare ground was much greater than the infiltration capacity of the land, surface runoff would be formed rapidly, and the amount of infiltration would be small, and there was a shallow and relatively impermeable layer in naturally restored grassland, and there was a big difference between the infiltration capacity of the upper and lower soil layers, so as to form a loamy mid-stream. [Conclusion] Vegetation restoration alters the hydrological properties of the soil, changing the runoff mechanism on slopes from predominantly overland flow to a combination of overland flow and interflow.

Abstract:[Objective] To investigate the constitutive relationship governing the entire failure process of root-soil matrixs. [Methods] By employing the Duncan-Chang model and conducting triaxial tests, a stress-strain constitutive relationship model was developed to analyze the entire failure process of the undisturbed root-soil matrixs. Vetiver samples at different growth stages (20, 40, 60 days) were utilized in conjunction with laterite to form root-soil matrixs. Subsequently, the response of model parameters to variations in root biomass was analyzed. [Results] (1) The Duncan-Chang constitutive relationship demonstrated an excellent capability in simulating the mechanical behavior of root-soil matrixs. Despite the inability to capture the strain softening phenomenon of individual soil, the stress-strain curve, predicted shear strength indicators, and measured values exhibit a strong correlation (R²>0.91). They effectively predicted the variation characteristics of the curve in the elastic, hardening and plastic stages. (2) The Duncan-Chang constitutive model parameters of root-soil matrixs exhibited a significant correlation with root characteristic parameters. With the growth of vetiver, the parameters c_c、φ_c、K、R_f and initial shear strength E_i all increased. The variation pattern of parameter n was slightly unique, as it was larger in the bare soil group than in the root-soil group. However, within the root-soil group, n gradually increased with plant growth. (3) The vetiver root system effectively reinforced the soil. Throughout the growth peroid, the longer the growth time, the more developed the root system and the greater the root biomass, the greater improvements in soil shear strength and shear strength indicators (c_t、φ_t) would be. [Conclusion] A constitutive relationship of root-soil matrixs based on the Duncan-Chang model has been established, and this can enhance the understanding of the mechanical behavior of root-soil matrixs in shallow surface landslides, and provide a theoretical basis for effective prevention and control of shallow surface landslide disasters.

Abstract:[Objective] Converting slopes into terraces is a crucial soil and water conservation and agricultural measure on the Loess Plateau. Understanding the impact of terraced walls on soil water is conducive to preserving soil water and enhancing terrace productivity. [Methods] Soil samples were collected from different locations on typical artificial high-slope terraces (terraced wall height of 5 meters) on the Loess Plateau to measure soil water content and soil physical and chemical properties. The spatial distribution characteristics and influencing factors of soil water were analyzed. [Results] The results showed that as the distance from the terraced wall increased, the soil water storage in the 0-300 cm soil layer increased significantly from 15.9 mm to 328.6 mm. The evaporation from the terraced wall decreased gradually from 318.0 mm to 83.4 mm. When the terrace width was 300 cm, the evaporation from the terraced wall could account for 33% to 38% of the soil water storage. The depth of the soil layer and the distance from the terraced wall were the main factors influencing soil water content, while the correlation between soil particle composition as well as organic matter content and soil water content was low. [Conclusion] Lateral evaporation caused by the terraced walls on the Loess Plateau significantly affects the distribution of soil moisture, leading to a reduction in soil water on the side adjacent to the walls. Appropriate measures should be taken in terrace maintenance and management to reduce soil water loss due to evaporation from the terraced walls.

Abstract:[Objective] To investigate the soil moisture response to rainfall in loess ground with different slopes and vegetation types. [Methods] Eight in-situ observation plots were established, including flat surfaces with bare soil, Artemisia cover, and Robinia pseudoacacia cover, 15° slope with bare soil, Artemisia cover, R. pseudoacacia cover, and R. pseudoacacia-Artemisia complex cover, and 35° slope with R. pseudoacacia-Artemisia complex cover. Soil moisture content and basic physical parameters of the profiles were measured. The wetting front depth after rainfall was observed and the impact of vegetation type and slope gradient on rainfall infiltration was analyzed. Additionally, laboratory model tests with six different slope gradients were conducted to study the relationships between slope gradient, as well as vertical infiltration depth, and infiltration thickness normal to the slope surface. [Results] The results suggest that vegetation types significantly affected the depth of the wetting front, soil moisture content, and saturation of slope soils. The R. pseudoacacia-Artemisia complex cover had the shallowest wetting front depth with a saturation of 73.0%. The bare soil exhibited the deepest wetting front and the lowest saturation, which was only 52.4%. The slope gradient had a minimal impact on the wetting front depth, soil moisture content and saturation for slopes with identical vegetation. However, after a number of short-term rainfall events, the moisture content and saturation in the wetting zone were slightly higher in flat ground than those in slopes. Laboratory model tests revealed that the vertical infiltration depth in slope was independent of slope gradient. In contrast, the infiltration thickness normal to the slope surface decreased with increasing slope gradient. [Conclusion] The study can provide a theoretical support for shallow landslide mitigation and soil erosion control for loess slopes.

Abstract:[Objective] The long-term variations of soil saturated hydraulic conductivity (K_s) and its primary controlling factors in terraces on the Loess Plateau were explored. [Methods] Terraces were selected for three land use types, i.e. farmland, orchard, and grassland, with slope designated as the control. Soil samples were collected from slopes and terraces with construction ages of 7, 20, 30 and 40 years to determine the K_s and soil physicochemical properties. The Kruskal-Wallis H test, Spearman correlation analysis, and partial least squares path model (PLS-PM) were conducted to examine the impact of terrace construction on K_s and its temporal variations, as well as the influencing factors. [Results] (1) The K_s of terraces under different land use types exhibited varying patterns with increasing ages of terrace construction. The K_s of farmland increased continuously with construction age of 7, 20, 30 and 40 years, increasing from 0.18 mm/min to 0.28 mm/min, with a growth rate of 55.56%. The K_s of orchard increased with the increase of construction years firstly, then showed a decreasing trend after 30 years, and the K_s of orchard with a construction age of 30 years was significantly higher than that of orchard with a construction age of 7 years, increasing from 0.12 mm/min to 0.35 mm/min, with a growth rate of 191.67%. The K_s of grassland increased with the increase of construction years firstly, then remained relatively stable after 20 years, and the K_s of grassland with a construction age of 20 years was significantly higher than that of grassland with a construction age of 7 years, increasing from 0.14 mm/min to 0.31 mm/min, with a growth rate of 121.43%. (2) The primary factors influencing K_s included soil particle size distribution, soil bulk density, and mean weight diameter of aggregates, with the path coefficients being -0.431, -0.561 and 0.226, respectively. [Conclusion] The variation in the impact of terrace land use types on soil properties resulted in varying patterns of K_s with increasing ages of terrace construction. The results can provide a basis for the subsequent management of terraces and the development of efficient dryland farming.

Abstract:[Objective] To investigate the changes of soil respiration in desert ecosystems and its relationship with environmental factors during the spring freeze-thaw period in arid and semi-arid regions, and to provide data support for the carbon budget of sandy land ecosystems in arid and semi-arid regions. [Methods] Soil respiration rates of salix plantations that were untouched and unlevelled stubble (ww), untouched and levelled stubble (wp), untouched and unlevelled stubble (zw), and levelled and levelled stubble (zp) were measured in the snow-free treatment by using the Li-6800 soil-carbon-water flux measurement chamber in the Salix Forest Germplasm Resource Bank of the Dalate Banner, Ordos, Inner Mongolia, and the atmospheric temperature, soil temperature and humidity were measured simultaneously. [Results] The results showed that the daily change of soil respiration during the freeze-thaw alternation period showed a unimodal trend, with the peak occurring between 10:00 am and 12:00 pm. Snowfall accelerated soil respiration rate and enhanced the temperature sensitivity of soil respiration (Q₁₀) during the spring freeze-thaw period, but it did not change the daily change pattern of soil respiration. After stubble levelling of the salix plantation, soil respiration rate slowed down but Q₁₀ increased; land preparation measure reduced the daily flux of soil respiration in general, and it also reduced the Q₁₀ value. Soil respiration was significantly correlated with soil temperature under each treatment, and the single factor model could explain 51%~68% of the variation in soil respiration (p<0.001), but the correlation between soil respiration and soil moisture was not significant. The two-factor composite model of soil temperature and moisture explained soil respiration better than the single factor model, and it explained 81% of the variation in soil respiration. The simulation results of the structural equation modelling (SEM) showed that all factors could jointly explain 70% of the variation in soil respiration rate, snowfall and stubble levelling directly affected soil respiration, and land preparation affected soil respiration indirectly by affecting soil temperature and moisture. [Conclusion] Snowfall in winter can provide water for vegetation growth in early spring, and it regulates the carbon budget in arid and semi-arid regions; stubble levelling and land preparation can impede the release of carbon during the freeze-thaw period in arid and semi-arid areas and indirectly slow down the loss of carbon from the soil, thus contributing to the regulation of the carbon budget of the ecosystem.

Abstract:[Objective] Empirical rainfall thresholds have geographical limitations, it is of great significance to carry out a rainfall threshold modeling study for landslide hazard on the Chinese Loess Plateau. [Methods] Taking the Yanhe River Basin on the Loess Plateau as the research area, the landslide identification of the Yanhe River Basin based on InSAR was carried out by integrating Sentinel-1A, DEM, GPM rainfall and other multi-source data. Then the correlations between rainfall factors and landslide shape variables were calculated to determine the rainfall days and effective rainfall attenuation coefficient in the early period. Finally, the effective rainfall (E), rainfall intensity (I) and rainfall duration (D) were calculated, and the E-D, I-D and E-I rainfall threshold models were established by combining the power function. [Results] (1) A total of 107 landslides from 2017 to 2021 were identified, including the specific location and accelerated deformation time of landslides. (2) With the increase of rainfall days in the early period, the correlations between cumulative rainfall and landslide shape variables showed a trend of first increasing and then decreasing. When the attenuation coefficient of effective rainfall in the current period (K) was equal to 1, the correlation between the effective cumulative rainfall in nine days (the rainfall on the day of landslide occurrence and the rainfall in the previous eight days) and the landslide shape variable was the strongest. (3) The expressions corresponding to the E-D, I-D and E-I rainfall threshold models are E=12.19D^0.661,I=10.66D^－0.255 and E=3.84I^1.141, respectively. [Conclusion] The rainfall threshold model can provide a scientific basis and reference for meteorological early warning of landslide hazards in the Yanhe Basin of the Chinese Loess Plateau.

Abstract:[Objective] Studying the accumulation characteristics and hydrological effects of typical mixed Robinia pseudoacacia plantations is crucial for deeply investigating the water conservation capacity of artificial forests on the Loess Plateau. [Methods] This study focused on five different mixed planting patterns of Robinia pseudoacacia in the loess hilly region, including R. pseudoacacia×Hippophae rhamnoides, R. pseudoacacia×Amorpha fruticosa, R. pseudoacacia ×Pinus tabuliformis, R. pseudoacacia×Prunus davidiana, and R. pseudoacacia×Prunus sibirica, with pure R. pseudoacacia plantations serving as a control for comparative analysis. Through field investigations and laboratory experiments, quantitative research was conducted on the accumulation, water-holding capacity, and evaporation characteristics of litter in these mixed plantations. [Results] (1) The total litter accumulation in different mixed R. pseudoacacia plantations ranged from 0.29 to 1.01 kg/m², with semi-decomposed litter accounting for more than 60% in all cases. Except for the mixture with A. fruticosa, the leaf litter accumulation in other mixtures was higher than that in pure R. pseudoacacia plantations. (2) After 24 hours, the water-holding capacity of litter from different mixtures stabilized with no significant differences. The trend for different organs was leaf> grass> fruit> branch. Furthermore, the effective interception and storage capacity of R. pseudoacacia× A. fruticosa was the largest (1.74 kg/m²), and the effective storage capacity of semi-decomposed litter was greater than that of undecomposed litter (p<0.05). (3) Evaporation of semi-decomposed and undecomposed litter reached a stable stage after 84 and 60 hours, respectively. The evaporation amount and rate followed the same trend as water-holding capacity, in the order of leaf> grass> fruit> branch. (4) During the water-holding and evaporation coupling process, a significant logarithmic relationship existed in the water-holding phase (R²≥0.84, p＜0.01), while a significant power function relationship was observed in the evaporation phase (R² ≥ 0.94, p＜0.01). The natural water content of litter was reached indoors and outdoors between 48~60 hours and 24~36 hours, respectively. [Conclusion] Overall, the hydrological effect of R. pseudoacacia×A. fruticosa litter was optimal. These findings provide a scientific basis for vegetation restoration, soil and water conservation projects, and ecological benefit evaluation in the region.

Abstract:[Objective] To investigate the evolution of soil carbon pool under catchment scale integrated soil and water conservation measures and evaluate the potential of soil and water conservation carbon sink. [Methods] Typical small watershed for soil and water loss control in the Loess Plateau was taken as the research object. Based on the analysis of the spatio-temporal changes of soil and water conservation measures in the watershed, the evolution law of soil organic carbon (SOC) pool under different soil and water conservation measures was clarified, and the potential of soil carbon sink under different soil and water conservation arrangements was evaluated with scenario analysis. [Results] (1) Compared with 1977, the total area of soil and water conservation measures in the basin increased by 32.9%, with the area of dam land, slope woodland, terraced grassland and terraced woodland increasing by 0.5%, 5.0%, 11.1% and 16.3%, respectively. The types of soil and water conservation measures were mainly terraced grassland and slope grassland. (2) The SOC density of different soil and water conservation measures increased compared with the bare land on the slope, and the SOC density of terraced measures was higher than that of slope measures. Terraced grassland, terraced woodland, slope grassland, channel grassland, slope woodland and dam land increased by 318.1%, 255.3%, 150.0%, 130.9%, 103.9% and 73.9%, respectively. (3) Soil and water conservation carbon storage in the study area increased from 264.5 t in 1977 to 332.8 t in 2022, with an increase of 25.8%, of which only 3.5% increased from 1977 to 2004, 22.4% increased from 2004 to 2015, and it then tended to be stable after 2015. (4) Under the condition that the soil below the ridge crest line remained unchanged, the soil organic carbon sequestration potential was the highest when the terraced grassland measures were adopted above the ridge crest line, with an increase of 20.5% compared with 2022. [Conclusion] The results indicate that, even in small watersheds with well-established soil and water conservation measures, optimizing the configuration of soil and water conservation measures can further enhance carbon sequestration potential.

Abstract:[Objective] To analyze the impacts of the "Grain-for-Green Project" on the ecosystem carbon stocks in Guizhou Province. [Methods] Taking Guizhou Province as an example, the spatial and temporal distribution pattern and carbon stock changes of the "Grain-for-Green Project" in Guizhou Province from 2000 to 2020 were investigated by using ArcGIS in combination with the InVEST model. [Results] (1) During the 20-year period, land use in Guizhou Province had changed significantly, and the comprehensive dynamic had shown a downward and then an upward trend, which was 0.32%, 0.11%, 0.09%, 0.35% in order. There was an interconversion among cropland, woodland and grassland, with built-up land and waters mainly derived from cropland. (2) The total area of the "Grain-for-Green Project" from 2000 to 2020 was 2 381 700 hm², of which the land use transformation was mainly dominated by the conversion of cropland to forest land, which accounted for 84.86% of the total area of the "Grain-for-Green Project", and mainly in Zunyi, Bijie and Qianxinan Prefecture, etc. (3) A total of 257.40×10⁶ t carbon stock was added to the "Grain-for-Green Project" area from 2000 to 2020, showing a trend of gradual growth. Cropland shifted to forest land sequestered the largest amount of carbon, amounting to 239.89×10⁶ t (93.2%), and the soil carbon pool was the main contributor, with a carbon stock of 178.15×10⁶ t (69.21%). [Conclusion] The implementation of the "Grain-for-Green Project" helps to increase the regional ecosystem carbon stock. The carbon sequestration capacity of conversion of cropland to forest land is the largest, and the carbon sequestration capacity of conversion of cropland to grassland is smaller. The implementation of the "Grain-for-Green Project" in the future can prioritize the conversion of cropland to forest land, in order to increase the regional carbon stock.

Abstract:[Objective] Chongqing, as the economic center of the upper reaches of the Yangtze River in China and a barrier to ensure ecological security in the middle and lower reaches of the Yangtze River, is a typical ecological functional and fragile area in China. Studying the spatiotemporal evolution characteristics and ecological sensitivity of its land use is of great significance for the reconstruction of land use and ecological protection in the research area. [Methods] A comprehensive assessment of the ecological sensitivity of Chongqing City was conducted by using remote sensing data from the years 2000, 2010 and 2020. This evaluation integrated various analytical approaches with software tools such as ArcGIS and Fragstat. Specifically, the Coupled Spatial Distance Index Model, Spatial Autocorrelation Analysis, Geodetector Model, and Grid Coding techniques were applied to evaluate the ecological sensitivity comprehensively. [Results] (1) In the study area, the landscape matrix was predominantly composed of farmland, accounting for more than 45% of the total area. There had been a significant reduction in both cropland and grassland, while the areas of forest land and urban-rural construction land had increased markedly from 2000 to 2020. (2) Over the course of 20 years, the average value of the comprehensive ecological sensitivity index rose from 1.037 to 1.045, indicating an overall improvement in the ecological environment of the study area. Spatial autocorrelation analysis revealed that the Global Moran’s I index for the comprehensive ecological sensitivity in Chongqing consistently exceeded 0, indicating a clear spatial heterogeneity in the sensitivity. Specifically, sensitivity decreased in a stepwise manner from the inner to the outer regions. Areas of high and very high sensitivity were predominantly found in the western part of Chongqing, the eastern new town, and the northeastern Three Gorges Reservoir area. Regions with significant changes in sensitivity levels were located in the central urban area and the southeastern Wuling Mountainous area of Chongqing. (3) The temporal and spatial evolution of comprehensive ecological sensitivity in the study area was the result of the joint action of natural environmental factors and social economic factors. Single-factor detection results indicate that the comprehensive index of average temperature, soil type, and land use degree were the main driving factors. The results of interactive exploration showed both linear and nonlinear enhancements, and the impact of the interaction between average temperature, annual rainfall, first industry added value, and per capita GDP on comprehensive ecological sensitivity showed a significant synergistic enhancement effect. [Conclusion] Based on the characteristics of ecological sensitivity spatial and temporal evolution in the study area, Chongqing City is divided into five zones, i.e. the comprehensive development zone, ecological improvement zone, potential governance zone, ecological regression zone, and strict protection zone, and corresponding measures are proposed for each zone. The research findings can provide theoretical support and decision-making basis for the reconstruction of ecological security pattern and sustainable development of Chongqing.

Abstract:[Objective] The forest coverage rate in the Yangtze River Delta region reaches 33.4%, and the underlying surface soil may have an important impact on the regional greenhouse gas budget. To explore the characteristics of changes in CH₄ and N₂O fluxes in the forest ecosystem soil in this region, as well as the effects of soil physicochemical properties and litter on these two greenhouse gas fluxes. [Methods] Taking the typical broad-leaved forest soil in Hangzhou, Zhejiang Province as the research object, soil-air interface CH₄ and N₂O fluxes were continuously measured from November 2022 to November 2023 by the static chamber-gas chromatography method. [Results] The average annual absorption fluxes of CH₄ in the soil without litter (S) and soil with litter (SL) treatments were(47.82±18.54),(36.80±13.55) μg/(m²·h), as well as the average emission fluxes of N₂O were (80.74±45.24),(52.70±25.98) μg/(m²·h), respectively. The seasonal variations of CH₄ absorption fluxes were similar under the two treatments of S and SL, with the absorption flux in spring and summer being higher than that in autumn and winter. The N₂O emission fluxes of the two treatments also showed similar seasonal variations, with the highest in summer, followed by spring, and lower in autumn and winter. Litter had a significant impact on CH₄ absorption and N₂O emissions, with litter remove leading to a 29.9％ increase in CH₄ influx and a 53.2％ increase in N₂O efflux. Correlation analysis revealed that the CH₄ absorption flux and N₂O emission flux under the two treatments were significantly positively correlated with soil organic carbon content and soil temperature, respectively (p<0.05). The CH₄ absorption flux had a significant negative correlation with soil bulk density under SL treatment (p<0.05). [Conclusion] The research results indicate that broad-leaved forests have an important role in forest carbon sinks, and the management of soil litter in broad-leaved forest is crucial for balancing CH₄ absorption and N₂O emissions, as well as mitigating climate warming.

Abstract:[Objective] Soil organic carbon is an important component of the carbon cycle in forest ecosystems, and active organic carbon can indicate changes in soil carbon pools. Studying the pattern of change of soil active carbon fractions and carbon pool stability in different forest types is of great significance to the understanding of the biogeochemical processes of the carbon cycle, and can provide a basis for the management of ecosystem carbon pools oriented to carbon sequestration and emission reduction. [Methods] The soil samples of 0-10 and 10-20 cm soil layers were collected from May to September in the growing season from Larix gmelinii, Pinus sylvestris var. mongolica, Betula platyphylla and Populus davidiana forests in the northern part of Daxing' anling, and the contents of different reactive carbon oxides in the soils were measured by the modified Loginow method, and the active carbon utilisation (ER) and carbon pool activity (CPA) were used to measure the carbon pool stability and the carbon cycle. [Results] (1) From May to September, soil total organic carbon (TOC), highly active organic carbon (LOC-H) and moderately active organic carbon (LOC-M) of the four forest types showed a "single-peak" trend of change, and reached a peak in August, and the contents were higher in broad-leaved forests than in coniferous forests. (2) The utilisation rate of soil stability organic carbon (ER₄) fluctuated between 72.33% and 85.11% from May to September, it was significantly higher than the utilisation rates of the other three types of active carbon, and dominated the soil carbon pool. (3) Soil carbon pool activity (CPA) fluctuated between 0.20 and 0.38, with P. davidiana forests>B. platyphylla forests>P. sylvestris var. mongolica forests >L. gmelinii forests; that of coniferous forests peaked in August, while that of broad-leaved forests were highest in May. (4) Soil active organic carbon content and carbon pool stability were subject to the combined effects of climatic factors and soil factors. Sucrase was the main influence of soil factors, while rainfall and photosynthetically active radiation were more influential among climatic factors. The overall stability of soil organic carbon in coniferous forests in the cold temperate zone was greater than that in broad-leaved forests, but the rate of organic carbon loss from deeper soil layers in coniferous forests was higher than that in broad-leaved forests under higher temperatures. [Conclusion] This study helps to improve the understanding of soil active carbon and organic carbon pools in cold temperate forests, artificially promoting secondary forest succession or introducing coniferous species as soon as possible is suggested to form mixed forests in the region, but the role played by broad-leaved forests in soil carbon pools should not be ignored in the context of increasing global warming.

Abstract:[Objective] The alpine and canyon region of Southwest China is a crucial ecological security barrier within the national "Three Zones and Four Belts" strategy, and it plays an essential role in ensuring national ecological security and promoting regional high-quality development. However, the ecosystem services and their trade-offs and synergies in this area remain unclear. [Methods] Three typical ecosystem services in the alpine and canyon region of southwest China from 2000 to 2020 were systematically evaluated using the InVEST model, RUSLE model, and WR index, in combination with multi-source geographic datasets. [Results] (1) From 2000 to 2020, carbon sequestration and water retention services in the alpine and canyon region of southwest China were steadily improved, with annual carbon sequestration increasing from 1 927 g/(m²·a) to 1985 g/(m²·a), and the WR index rising from 0.062 to 0.067. Spatially, carbon sequestration gradually increased from northwest to southeast, while water retention exhibited strong spatial heterogeneity. In contrast, soil retention services was overall deteriorated, decreasing from 263.50 t/(km²·a) to 226.25 t/(km²·a), with a reduction of 27.50% in the northwest Yunnan alpine canyon ecological maintenance zone. (2) The proportion of the area of ecosystem service hotspot areas increased by 5.41%, following a distribution pattern of the first-class hotspot areas> the non-hot spot areas> the second-class hotspot areas> the third-class hotspot areas form 2000 to 2020. (3) Carbon sequestration services exhibited a synergistic relationship with both water retention services and soil retention services, with synergy areas accounting for 54.91% and 44.46% of the total area, respectively. These synergies were mainly located in the southeastern Tibetan alpine canyon ecological maintenance zone and the eastern Tibetan-western Sichuan alpine canyon ecological maintenance and water retention zone. However, water retention and soil retention services displayed a trade-off relationship, with the synergy area accounting for only 20.14% of the total area. [Conclusion] The results can provide necessary references for scientifically formulating and implementing ecological protection policies and optimizing resource management strategies in the alpine and canyon region of Southwest China.

Abstract:[Objective] To clarify the spatio-temporal characteristics of vegetation evolution in the Three Gorges Reservoir Area, and to quantitatively analyze the relationships between vegetation and key determinants, including climate, terrain, and human activities. [Methods] Based on Normalized Difference Vegetation Index(NDVI) data, a suite of analytical techniques was employed, including Theil-Sen Median Trend Analysis, the Mann-Kendall Test for significance, Hurst Exponent Analysis, and Geographic Detector Modeling, to investigate the spatio-temporal patterns and driving forces of NDVI within the Three Gorges Reservoir Area from the year 2000 to 2020. [Results] (1) The change of NDVI in the Three Gorges Reservoir Area showed an overall ascending trend from 2000 to 2020, with a mean annual rate of increase at 2.89×10^-3/a, and the value of NDVI increased from the southwestern to the northeastern parts of the area. (2) Elevation, population density, and surface temperature are pivotal factors that significantly account for the variability observed in NDVI, with an explanatory power for each exceeding the threshold of 0.4. (3) Elevation and nocturnal illumination are the key interactive drivers of NDVI in the Three Gorges Reservoir Area, with a pronounced q value of 0.641. Their interplay showed a nonlinear or synergistic enhancement, and the integrated explanatory power of the two factors on NDVI changes is always greater than that of single factors. [Conclusion] The results of this study can offer a robust scientific support for the formulation of ecological and environmental conservation policies and for sustainable ecological development within the Three Gorges Reservoir Area.

Abstract:[Objective] Understanding the future temporal and spatial evolution of land use and soil erosion in the Huaihe River Basin is of significant importance for rational and coordinated use of land resources, formulating future soil and water conservation strategies, and promoting sustainable development strategies. [Methods] Based on the PLUS model and the Chinese Soil Loss Equation (CSLE), the land use patterns in the Huaihe River Basin under three scenarios—natural development, ecological protection, and rapid development—for the year 2030 were simulated, and the future soil erosion patterns in the basin under these three scenarios were predicted. [Results] (1) Under all three scenarios, there was a significant expansion of construction land, with a maximum expansion area of 187.80 km², while other land types decreased to varying degrees. (2) The soil erosion intensity in the basin from 2015 to 2021 showed a downward-then-upward trend. The average soil erosion amounts were 221.96, 214.13 and 461.15 t/(km²·a), respectively. High-intensity erosion was mostly concentrated in the northeastern high-slope areas, which require special attention. (3) Geographic detectors indicate that slope, DEM, and soil properties were the main driving factors influencing the distribution of erosion in the basin. (4) In 2030, the soil erosion modulus under natural development, rapid development, and ecological protection scenarios were 295.48, 259.45 and 127.64 t/(km²·a), respectively. An ecological protection model with appropriate expansion of construction land can meet both ecological protection and economic development demands. [Conclusion] This study can provide insights for land use management and soil conservation measures within the basin and promote healthy development.

Abstract:[Objective] The study of spatial-temporal variations and influencing factors of water-related ecosystem services under complex terrain in Southwest China can serve as a foundation for the ecological management and sustainable development in this region. [Methods] The annual water yield and soil erosion in Southwest China from 1992 to 2020 were evaluated to explore the multi-dimensional (including time, space and elevation) variation characteristics by the InVEST model and universal soil loss equation. In addition, the relative weight analysis method was used to quantify the relative contribution rate of climate and land use change to water-related ecosystem services. [Results] (1) From 1992 to 2020, water yield in Southwest China showed a downward trend, with a notable mutation occurring in 2002; soil erosion showed an increasing trend, with a mutation observed in 1997. (2) The water yield decreased and soil erosion increased with rising altitude. (3) The relative contribution rate of precipitation to both water yield and soil erosion in karst areas was found to be greater than that in non-karst areas. [Conclusion] Climate change has a more significant impact on water yield and soil erosion, while land use change has a less obvious impact. This study will contribute to the ecological protection in complex terrain (with different elevations and different landforms) and provide a scientific basis for land management and ecological restoration measures in karst areas.

Abstract:[Objective] To investigate the spatial and temporal variations of land surface temperature (LST) in central Yunnan urban agglomeration and its relationship with land use/land cover (LULC) types. [Methods] Based on Google Earth Engine (GEE) platform, LST was inverted using Landsat satellite image data of central Yunnan urban agglomeration region from 1990 to 2020, and was analyzed using Sen-MK trend analysis, mean-standard deviation method, urban thermal field variance index (UTFVI) and correlation analysis were used to quantitatively analyze the spatial and temporal variations of LST and its response to LULC types in central Yunnan urban agglomeration from 1990 to 2020. [Results] (1) There were significant spatial and temporal differences in interannual temperature classes in central Yunnan urban agglomeration. The mesothermal area always occupied an absolutely dominant position (40%), but its area share decreased year by year. (2) From 1990 to 2020, the areas with UTFVI 0 showed an increasing trend year by year, and the areas with UTFVI > 0.02 showed a decreasing trend, and the ecological and thermal environments were gradually improved. (3) There were response differences in LST for different LULC types. Among them, LST was significantly positively correlated with the proportion of built-up area (r > 0.70). LST was always the lowest in the water area, with a multi-year average temperature of 17.38 ℃, while the highest temperature was found in the area covered by built-up land and cropland, with multi-year average temperatures above 21 ℃. (4) The rapid expansion of cities in the central Yunnan urban agglomeration had resulted in significant changes in LULC. The built-up land area had increased by more than 100.29%, and the rapid development of cities had increased LST from 1990 to 2020. [Conclusion] LULC is an important factor affecting the LST, and reasonable configuration of LULC structure can improve the thermal environment of urban agglomeration. The study's results can provide important insights for rational development planning and improvement of ecological conditions in the urban agglomeration of central Yunnan.

Abstract:[Objective] Soil microbial metabolic efficiency profoundly affects soil nutrient cycling and soil carbon sequestration in the recovery process of eroded and degraded areas. However, it is unclear how tree species mixture affects soil extracellular enzyme stoichiometry and microbial carbon-utilization efficiency in single Pinus massoniana plantation in the eroded red soil area. [Methods] In this study, we used single P. massoniana plantation, and P. massoniana and Schima superba mixed plantation with different restoration years, determined the soil physicochemical properties, extracellular enzyme activity and phospholipid fatty acid markers of different forests, and calculated the soil enzyme stoichiometric ratio and microbial carbon-utilization efficiency (CUE). [Results] (1) With the increase of restoration years, soil acid phosphatase (AP) and β-glucosidase (βG) activities were significantly reduced, while C∶N_EEA (βG∶NAG), vector length (VL) and vector angle (VA) of the mixed forest were lower than that of pure forest, while C∶P_EEA (βG∶AP) and N∶P_EEA (NAG∶AP) showed the opposite trend, indicating that long-term mixing is beneficial to alleviate the carbon limitation and phosphorus limitation of microorganisms.(2) Mixing was beneficial to improve CUE and significantly increased with the increase of forest age. Specifically, compared with that of Y39-CF and Y19-MF, CUE of Y39-MF significantly increased by 200.00% and 136.84%, respectively.(3) By analyzing the characteristics of soil enzyme activity and the relationship between CUE and environmental factors, it was found that soil carbon, nitrogen and phosphorus availability was an important influencing factor, mainly affecting AP activity, C∶P_EEA, N∶P_EEA, VL, VA and CUE, while the stoichiometric ratio of soil nutrients mainly affected βG activity and C∶N_EEA.(4) The results of redundancy analysis (RDA) showed that the ratio of fungi and bacteria mainly affected the characteristics of soil enzyme activity and CUE in the mixed forest, while the main influencing factors in pure forest were actinomyces and Gram-negative bacteria. [Conclusion] Mixing tree species significantly improves forest soil nutrients, affects the release of soil extracellular enzymes, and improves CUE, and it is conducive to soil carbon sequestration. Therefore, the differences between pure forest and secondary forest should be considered in future management and research of P. massoniana forest.

Abstract:[Objective] To study the characteristics of changes in chemical properties and diversity and structural composition of soil microbial communities in Pinus yun-nanensis soils on the Central Yunnan Plateau under nitrogen deposition, and to analyze the correlation between soil microorganisms and soil chemical properties, in order to provide a scientific basis for understanding the trend of changes in nutrient cycling in forest soil ecosystems under nitrogen deposition and observing soil microbiological changes. [Method] The soil of P. yunnanensis forests on the Central Yunnan Plateau was selected as the research object, CO(NH₂)₂ was used as the N source, and four different gradients were set up for simulated N deposition experiments, including control CK [N 0 g/(m²·a)], low nitrogen LN [N 10 g/(m²·a)], medium nitrogen MN [N 20 g/(m²·a)], and high nitrogen HN [N 25 g/(m²·a)], the structure and diversity of soil bacterial and fungal community were analyzed, and the characteristics of the changes of soil pH, TOC, TN, TP, NH⁺₄-N and NO^-₃-N were determined. [Results] (1) In both the dry and rainy seasons, soil pH and TOC content were reduced, and TN was increased under each N treatment when compared with CK, and both NH⁺₄-N and NO^-₃-N were increased at MN and HN compared to CK; (2) Both bacterial and fungal α-diversity were higher in the rainy season than in the dry season; bacterial α-diversity increased at LN under both seasons compared to CK, whereas fungi α-diversity increased at LN in the dry season; (3) In both the dry and rainy seasons, the dominant bacterial phyla were Proteobacteria, Acidobacteria and Actinobacteria, and the dominant fungal phyla were Basidiomycota, Ascomycota and Mortierellomycota; (4) The dominant bacterial and fungal genera were significantly correlated with pH, TOC, TN and NO^-₃-N during the dry and wet seasons. [Conclusion] Nitrogen deposition can provide soil microorganisms with effective nutrients such as NH⁺₄-N and NO^-₃-N, but soil acidification due to nitrogen deposition can reduce soil TOC content and affect the structure of soil microbial communities.

Abstract:[Objective] Afforestation following the Grain for Green initiative is a crucial measure to improve soil structure and reduce soil erosion. Understanding the mechanisms of the effects of afforestation tree species on the formation of soil aggregates can provide valuable insights for soil conservation. [Method] Four types of artificial forests (Cryptomeria fortunei (CF), Cryptomeria fortunei and Betula luminifera (MF), Camellia sinensis (CS), and Neosinocalamus affinis (NA)) established on sloping farmland (SF) (cornfield) in the Rainy Area of Western China after 20 years of afforestation were taken as the research objects, in order to analyze the changes in soil aggregate content and stability after the conversion from farmland to artificial forests. [Results] (1) Compared to the sloping farmland, the artificial forests of MF, CS, and NA significantly increased the soil aggregates >5 mm, but decreasd the 0.5~1 mm soil aggregates (p < 0.05). The dominant soil aggregates shifted from 0.5~1 mm to >5 mm. (2) The soil aggregate parameters, including the geometric mean diameter (GMD), mean weight diameter (MWD), and the content of aggregates of >0.25 mm (R_0.25), increased by 46.93%~330.30%, 47.01%~191.03% and 5.02%~19.66%, respectively, in the artificial forests. Conversely, the destruction rate (PAD_0.25) and fractal dimension (PSD) decreased by 15.41%~75.09% and 1.65%~9.20%, respectively. These indicators of aggregate stability consistently demonstrated that the stability of soil aggregates in the artificial forests was enhanced, with a specific ranking of CS> NA> MF> CF, indicating that CS and NA were both relatively superior. (3) The content and stability of dominant soil aggregates were extremely significantly positively correlated with the content of NOC, and extremely significantly negatively correlated with the content of soil gravel (p < 0.01). [Conclusion] The weathering of purple soil following afforestation provides the material foundation for aggregate formation, while the humus formed in the soil of artificial forests acts as a binding agent, promoting the formation of large aggregates and the maintenance of their stability.

Abstract:[Objective] To elucidate the characteristics of litter decomposition and changes in soil organic carbon (SOC) fractions under thinning, and to reveal the impact of litter decomposition on the stability of SOC in coastal shelter forests under thinning. [Methods] After three years of thinning, the litter and surface soil (0—20 cm) of coastal shelter forests (Quercus acutissima Carruth. (QAC), Pinus thunbergii Parl. (PTP) and mixed Q. acutissima Carruth. andP. thunbergii Parl. (QP) in Qingdao were studied. In situ decomposition of litter, indoor analyses of chemical properties, and random forest model were used to characterize the litter decomposition and SOC fractions under three different thinning intensities (control 0, light 15% and heavy 30%), and analyzed their relationships. [Results] Heavy thinning significantly increased the mass remaining of QAC and QP litter during decomposition, with an increase of 22.36% and 4.18% compared to the control, respectively. The trend of K-value changes representing litter decomposition rate was opposite to mass remaining. The SOC content, mineral associated organic carbon (MAOC) content, and SOC stability of QAC and QP all significantly increased with the increase of thinning intensity. The content and stability of SOC were significantly correlated with nitrogen and phosphorus residual rates during litter decomposition under thinning, but not with litter decomposition rate. [Conclusion] Thinning reduces the decomposition rate of litter, but increases the residual rates of carbon, nitrogen, and phosphorus in litter, especially under heavy thinning. Thinning improves the stability of SOC, and the changes in SOC content and stability are mainly influenced by the residual rates of nitrogen and phosphorus in litter, with phosphorus residual rate having the greatest impact.

Abstract:[Objective] Soil acidification, structure and fertility degradation and poor water-holding capacities are common problems in the apple orchard on the Loess Plateau, effective soil improvement techniques are crucial for enhancing soil quality, and promoting the healthy and sustainable development of the orchards. [Methods] Based on 75 publications and 1 302 field trial datasets on soil improvement in the apple orchards of the Loess Plateau, meta-analysis and principal component analysis (PCA) were used to quantitatively evaluate the effects of different improvement measures, including mulching, fertilization, and soil conditioners, on soil quality. [Results] The results indicated that grass mulching, plastic film mulching, straw mulching, and gravel mulching effectively reduced soil bulk density by 6.63%, 5.96%, 6.04%, and 6.40%, respectively. Additionally, grass mulching and straw mulching also significantly increased soil nutrient contents. Chemical fertilizer effectively increased available nitrogen (by 111.17%), available phosphorus (by 112.29%), and available potassium (by 43.95%), respectively. Organic fertilizer not only increased soil available nutrients, but also significantly increased soil organic matter (by 57.19%), total nitrogen (by 57.64%), and nitrate-nitrogen (by 94.51%). Combined application of organic and inorganic fertilizer significantly reduced soil bulk density (5.58%) and increased nutrient contents. Water-retaining agents effectively reduced soil bulk density (by 4.88%), increased total nitrogen (by 40.90%) and nitrate-nitrogen (by 143.51%). Biochar significantly increased soil organic matter (by 39.35%), nitrate-nitrogen (by 91.23%), and available phosphorus (by 89.70%). Soil quality assessment results indicated that soil quality index (SQI) ranked as 7.72 (organic fertilizer)> 7.68 (straw mulching)> 7.20 (organic-inorganic fertilizer)> 6.05 (water-retaining agent)> 5.99 (grass mulching)> 5.94 (biochar)> 5.79 (chemical fertilizer)> 3.53 (plastic film mulching)> 2.63 (gravel mulching). [Conclusion] Considering the practical conditions of soil quality and apple orchards yields, it is suggested that straw mulching and combined application of organic and inorganic fertilizer should be prioritized as measures to improve orchard soil quality, followed by organic fertilizers and grass mulching.

Abstract:[Objective] To study the vertical distribution pattern of cadmium (Cd) in shallow karst fissure soil, analyze the impacts of various factors on the distribution of Cd in fissures, and provide a scientific basis for future research on the distribution pattern of Cd in underground fissure soil and the prevention and control of Cd pollution. [Methods] Taking the small watershed of Baobao Mountain in Weining County, a region with a typical high geological background in the northwest of Guizhou, as the research object, the total Cd concentration and speciation of Cd in shallow fissure soil, along with five soil property indicators such as pH value, organic matter content, cation exchange capacity (CEC), particle size, and aggregate were systematically analyzed. The distribution pattern of Cd and its influencing factors were examined using one-way ANOVA and correlation analysis. [Results] (1) The physical and chemical properties of the fissure soil significantly affected the distribution of Cd. (2) The average pH value of the fissure soil was 6.70. The average Cd concentration was 2.99 mg/kg, the concentration was high at 0—20 cm and gradually decreased with increasing soil depth, and Cd was predominantly in the reducible form. (3) Total Cd concentration was mainly influenced by soil pH, CEC, clay, silt, and water-stable aggregates, with CEC being the primary controlling factor for the vertical distribution of Cd. (4) The distribution of Cd speciation was controlled by different factors, depending on the form of Cd, with the weak acid-extractable form primarily influenced by organic matter, the reducible form mainly influenced by CEC, the oxidizable form mainly influenced by CEC, clay, and silt, and the residual form mainly influenced by silt content. (5) There was a significant difference in Cd concentration between the soils of funnel-shaped and trapezoidal fissure profiles and the rectangular fissure profile. [Conclusion] The vertical distribution pattern of Cd in fissure soil is jointly influenced by soil physicochemical properties and fissure morphology, with rectangular fissures being more conducive to the accumulation of Cd.

Abstract:[Objective] This study aimed to investigate the effects of different modified corn straw biochars on the water retention and fertilizer conservation capacity of arid loess soil and their effects on crop growth.[Methods] The corn straw biochar produced by pyrolysis at 500 ℃ for 2 h under a nitrogen atmosphere was modified by immersion in 1 mol/L H₃PO₄, NaOH, and NH₄Cl reagents, respectively, to obtain different modified corn straw biochars. The elemental composition, and physical and chemical properties such as pore structure, of the biochar were systematically characterized. Pot experiments were used to examine soil water retention, nutrient conservation, and plant growth using soil treated with different ratios of fertilizer and biochar.[Results] In terms of the physicochemical properties of biochar, the oxygen content in the modified biochar increased by 4.73%~9.18%, while the ash content decreased by 12.69%~20.70%. The pH significantly decreased, and the increase in O/C ratio indicated enhanced hydrophilicity of the biochar. The specific surface area of the modified biochar increased by 3.26~5.19 times, and the total pore volume increased by 3~6 times. In terms of soil water retention and nutrient conservation properties, under the treatments of mixed application of biochar and fertilizer, soil bulk density decreased with the increase of the biochar-to-fertilizer ratio, and soil porosity increased by 2.42%~4.07%. The field water-holding capacity increased with the biochar-to-fertilizer ratio, with the highest value of 37.38% observed under the NaOH-modified biochar-to-fertilizer ratio of 2∶1. When the NH₄Cl-modified biochar-to-fertilizer ratio was 2∶1, soil organic matter and total potassium contents reached the highest values, being 8.23 and 15.17 g/kg, respectively. The highest total nitrogen and total phosphorus contents were 0.37 and 0.95 g/kg, respectively, when the H₃PO₄-modified biochar-to-fertilizer ratios were 1∶1 and 2∶1. Mixed application of modified biochar and organic fertilizer could increase available phosphorus and rapidly available potassium that can be directly absorbed and utilized by plants. The growth promotion effect on corn plants was most significant when the NH₄Cl-modified biochar-to-fertilizer ratio was 1∶2, and it was noted that an excessively high biochar-to-fertilizer ratio was not suitable. [Conclusion] In the arid regions of the loess hilly area, considering various factors, the application of NH₄Cl-modified biochar with a fertilizer ratio of 1∶1 and mixed with organic fertilizer can enhance the soil’s water retention and nutrient conservation properties.

Abstract:[Objective] To demonstrate that appropriate application of straw and organic fertilizer can effectively improve soil quality, have a positive effect on soil acidification mitigation and erosion control. [Method] Acidified red soil was used as the research object and a comparative analysis was performed for the effects of conventional fertilization (CK), chemical fertilizer reduction (30%), straw returning (6 000 kg/hm², FSM0), and the combination of chemical fertilizer reduction (30%) coupled with straw returning (6 000 kg/hm²) and different gradients of organic fertilizers (1 500, 3 000, 4 500 and 6 000 kg/hm²) (FSM1, FSM2, FSM3, and FSM4) on soil properties at different stages of rapeseed growth and rapeseed yield. [Results] The reduction of chemical fertilizers combined with straw and organic fertilizer application significantly (p < 0.05) improved soil acidity and nutrient status. Compared with CK, soil pH increased by 0.05~0.25 unit under the five treatments, while exchangeable H⁺, exchangeable Al³⁺, and exchangeable acids decreased by 10.82%~39.81%, 5.18%~22.10% and 5.67%~23.90%, respectively. Additionally, the total exchangeable base increased by 7.63%~34.68%, and the total nitrogen and organic matter contents in the soil also significantly increased (by 19.22%~62.86% and 18.43%~61.50%, respectively). Analysis of soil mechanics properties indicated that with the increase of organic fertilizer application, soil shear strength was significantly enhanced, while the cohesion and internal friction angle exhibited a trend of first increasing and then decreasing. Under FSM2 treatment, the shear strength, cohesion, and internal friction angle all reached their peak values, with a respective increase of 22.22%, 20.06% and 11.38% relative to CK. Economic benefit analysis revealed that FSM2 had the highest net income. [Conclusion] Based on soil acidification improvement, fertility enhancement, structural improvement, and rapeseed economic benefits, chemical fertilizer reduction (30%) coupled with straw returning (6 000 kg/hm²) and 3 000 kg/hm² organic fertilizer application can be recommended as the optimal management strategy. The results of this study can provide a scientific foundation for improving soil acidification and increasing crop yields.

Abstract:[Objective] In order to reduce soil pollution caused by plastic film, the application effect of using PBAT fully biodegradable plastic film instead of ordinary PE plastic film combined with drip irrigation to grow maize in mild secondary salinized soil was investigated. [Methods] Comparative tests were conducted on four mulching treatments, including PBAT biodegradable film (black and white) mulching, ordinary black film mulching and open-field cultivated maize without mulching, under three irrigation conditions (2 600, 3 300 and 4 200 m³/hm²) from April to September 2023 in Xinghuocun Experimental Station, Huinong District, Ningxia, and there were 12 treatments in total. The degradability of degradable film and its effect on soil water and salt transport and maize growth were studied. [Results] The water content in the 0-20 cm soil layer under black and white fully biodegradable mulch film was 18.87% and 18.34% higher than that under ordinary PE film, respectively, and 1.16% and 0.72% higher than that without mulching, respectively, and the soil salt content under black and white PBAT fully biodegradable film mulching and ordinary PE film mulching was reduced by 15.01%~23.10% compared with that without mulching (p< 0.05). Compared with the non-mulching conditions with 2 600 and 3 300 m³/hm² irrigation, the yield under black fully biodegradable film mulching increased by 11.88%~16.65%, but the difference was not significant under the irrigation condition of 4 200 m³/hm². Compared with the yield of 2 600 m³/hm² irrigation without mulching, the yield of white fully biodegradable film mulching increased by 13.42% under irrigation conditions, but there was no significant difference under 3 300 and 4 200 m³/hm² irrigation conditions. The water-use efficiency of black and white PBAT fully biodegradable film mulching was increased by 23.31% and 13.50% respectively compared with ordinary PE film mulching. Compared with no-mulching, it increased by 37.63% and 26.69% respectively. [Conclusion] The study suggests that it is feasible to replace ordinary mulch film with degradable mulch film in drip irrigation agricultural production in saline-alkali lands in the irrigation areas along the Yellow River.

Abstract:[Objective] To improve humic acid-modified magnetic biochar (HA-MBC) and explore the combined effects of modified biochar and arbuscular mycorrhizal fungi (AMF) on the properties of saline-alkali soils and the growth of muskmelon. [Methods] Through response surface methodology, the effects of the ratio of magnetic biochar to humic acid (1∶4, 1∶6, 1∶8), the concentration of FeCl₃ and FeSO₄ reagents (0.02, 0.04, 0.06 g/mL), and the cross-linking duration (48, 72, 96 h) on HA-MBC were analyzed, to procure the optimum amendment scheme suitable for combined application with AMF. Moreover, by conducting pot experiments, the influence of individual fungi, individual biochar, and combined biochar-fungi (AMF+10%B, AMF+20%B) on the physicochemical properties, and enzyme activities of saline soil and alkaline soil, and the photosynthetic parameters of muskmelon were studied. [Results] Under 15 and 75 mmol/L saline-alkali stress, combined application of 20 g/kg AMF with 20% HA-MBC showed the best mitigation effects, with a "synergistic enhancement" observed. On one hand, the iron oxides and humic acids loaded on HA-MBC improved the physical and chemical properties of soil by increasing the quantity of surface functional groups and porosity, while AMF formed symbiotic roots to further enrich organic matter and nutrients, and increase soil enzyme activities, thus increasing the height and root length of muskmelon and promoting the recovery of F_v/F_m and the reduction of F₀ and qN. On the other hand, the application of HA-MBC could increase the colonization rate of AMF in saline and alkaline soils by 19.46% and 22.72%, respectively, thus further enhancing the effects of AMF. Moreover, nutrients such as Fe²⁺, Mg²⁺ and nitrogen could form a transformation cycle between biochar and fungi, thus improving nutrient use efficiency. Under 150 mmol/L saline-alkali stress, applying a low dose of HA-MBC still played a role in ameliorating soil and mitigating stress, while applying high doses of biochar inhibited the improvement of indicators. This might be due to excessive application of HA-MBC causing surface functional groups to aggregate toxic substances and salt ions excessively and compete for nutrients, subsequently reducing AMF colonization rates, weakening the mycorrhizal symbiosis, and hence diminishing the photosynthetic parameters of muskmelon. [Conclusion] HA-MBC prepared with a biochar to humic acid ratio of 6∶1 and cross-linking time of 72 h, using 0.04 mmol/L FeCl₃ and FeSO₄ reagents, is suitable for combined application with AMF. The synergistic application of HA-MBC and AMF can improve the physicochemical properties and nutrient structure of saline-alkali soil and promote the photosynthesis of muskmelon under low to medium saline-alkali stress levels, whereas excessive application of HA-MBC under high stress concentrations inhibits the improvement of soil indicators and the recovery of photosynthetic parameters in muskmelon.

Abstract:[Objective] To investigate the effects of inoculating heterotrophic ammonia-oxidizing bacteria (HAOB) on yield and water use efficiency of dryland maize. [Methods] A two-year field experiment was conducted in a drought-prone area using HAOB strain S2_8_1 as the test strain and maize as the plant material. Four treatments were set up, inoculation with HAOB strain without irrigation (DI), non-irrigated control (DCK), inoculation with HAOB strain with irrigation (WI), and irrigated control (WCK). [Results] Inoculation with the HAOB strain enhanced the nitrification rate in the rhizosphere soil and the photosynthetic rate of dryland maize, significantly promoted maize growth and increased the yield(p＜0.05). The above-ground biomass at different stages and the yield at harvest in the DI and WI treatments were significantly higher than those in the DCK and WCK treatments, especially in the DI treatment. In both the drier 2022 and the wetter 2023, maize yields in the DI treatment exceeded those in the DCK and WCK treatments by at least 24.98%; in 2023, the yield of the DI treatment was comparable to that of the WI treatment, exceeding that of WCK by more than 11.29%. Additionally, inoculation of HAOB improved the water use efficiency of maize, with DI showing at least a 4.84% increase compared to DCK, and WI showing at least a 3.06% increase compared to WCK. The nitrification rates in the rhizosphere soil and the yields of DI and WI were similar, but DI did not require irrigation and had a higher water use efficiency. [Conclusion] The application of HAOB strains in dryland agriculture is an effective method for improving maize yield, and it can provide a new technological pathway and research direction for the development of dryland agriculture.

Abstract:[Objective] To study the effects of brackish water irrigation on soil water and salt characteristics and crop growth is helpful to guide the safe utilization of brackish water. [Methods] A pot experiment of winter wheat was carried out under the condition of rain-shielding. Deionized water was used as the control (CK). Three kinds of brackish water treatments with conductivity of 4 dS/m and different sodium-potassium ratios were set up, including sodium-potassium ratio of 1∶0 (T1), sodium-potassium ratio of 1∶1 (T2), sodium-potassium ratio of 0∶1 (T3). The water-salt characteristics of the soil, the photosynthetic physiology, growth and development as well as yield formation of winter wheat were studied. [Results] Compared with CK, the 0-40 cm soil moisture content under T1, T2 and T3 brackish water irrigation increased by 19%, 8% and 14% (p<0.05), respectively. Soil EC_1∶5 (soil water ratio 1∶5 extract conductivity) and Na⁺ and K⁺ concentrations continued to increase with the growth period of winter wheat. The 0-40 cm soil salinity of T1, T2 and T3 treatments increased by 252%, 223% and 234% (p<0.05), respectively, and most of the salt accumulated in the 10-20 cm soil layer. The net photosynthetic rate of winter wheat was significantly reduced (by 16%, p<0.05) in the T1 treatment compared to CK, while there was no significant differences (p>0.05) between the T2 and T3 treatments and CK. The T2 treatment enhanced plant height, leaf area per plant and aboveground dry matter mass of winter wheat, and increased the yield by 8.41% (p<0.05) compared to CK; while there was no significant difference in underground dry matter mass among treatments (p>0.05). [Conclusion] In summary, irrigation using 4 dS/m brackish water changed the original water-salt characteristics of the soil, caused salts to accumulate in the soil and promoted winter wheat growth in the short term. In this study, the use of brackish water with a sodium-potassium ratio of 1∶1 had a better effect on winter wheat growth and yield enhancement. The results can provide a theoretical basis for sustainable utilization of brackish water.