Abstract:To explore the spatial differentiation characteristics of rill erosion, artificial rainfall experiments were used to analyse stimulate the rill erosion process of slope under different rainfall intensities and slopes, and the variation characteristics of rill erosion intensity and morphology along the slope direction were discussed. The results showed that with the increase of slopes and rainfall intensities, rill erosion was increasing. Under specific treatments, rill erosion intensity increased first and then decreased in space; the rill morphology parameters, such as rill width, rill depth and rill split degree, also increased first and then decreased in space, and the peak values appeared in the middle of the slope. Rill width and rill depth had a very significant positive correlation with the amount of rill erosion, and the evolution of rill erosion intensity and morphology was consistent. The runoff collection leaded to the increased power of runoff erosion in the middle of the slope, where the ditch wall collapse and undercut erosion were serious, and rill width and rill depth were enlarged. However, the rill erosion under the slope was lower due to the large amount of sediment concentration and the stable base level of soil erosion. Severe erosion tended to occur in the middle of the slope, so it was necessary to strengthen prevention and control measures or take measures to intercept and drain water. The research results could provide theoretical and technical support for the prevention and control of rill erosion.

Abstract:Ten runoff plots with different configuration patterns of soil and water conservation measures in Shixia watershed Soil and Water Conservation Technology Demonstration Park were used as the study objects, and the changes in local rainfall patterns from 2004-2019 were firstly analyzed. In addition, 19 representative heavy rainfall events occurring in 2010-2018 were used as sample rainfall events to explore the effects of different configuration patterns on soil erosion and non-point source pollution characteristics. The results showed that: (1) Rainfall variation from 2004-2019 ranged 331.4~598.9 mm, with an average annual rainfall of 484 mm, a decrease in the frequency of light and moderate rainfall, and an increase in the frequency of heavy rainfall. (2) Soil and water conservation measures were effective in reducing flow and sediment and nutrient loss. In terms of reducing surface runoff, the best configuration models were fish scale pit clover fields and maize terraces, with flow reduction rates of 88.59% and 88.40% respectively; in terms of reducing sediment, the best configuration model was maize terraces, with a sediment reduction rate of 97.82%; in terms of reducing non-point source pollution, the best-performing configuration model was maize terraces, whose reduction rates for TN, TP and COD were 79.57%, 75.90% and 91.31% respectively. (3) Under heavy rainfall conditions, rainfall was positively correlated with flow production and sediment production, TN, TP and COD, and the correlation between rainfall and runoff volume and runoff coefficient were higher, with correlation coefficients of 0.608 and 0.553 respectively. I₃₀ and I₆₀ were more highly correlated with flow production and sediment production and COD. In addition, the correlations of rainfall ephemeris and I₆₀ with TN, TP and COD were also high. The results of the study provide a reference basis for revealing the soil erosion mechanism of slopes under heavy rainfall conditions in suburban areas of Beijing, and at the same time provide a scientific basis for local work on soil and water conservation under heavy rainfall.

Abstract:The morphological characteristics of gully erosion are the key factors to understand the occurrence and development of gully erosion, which are regarded having the great significance to explore the variation characteristics of gully morphology parameters in different seasons for in-depth understanding of the erosion process of gully erosion and its governance. In this study, three erosion gullies in Guangrong small watershed of Hailun City, Heilongjiang Province were selected as the research objects to explore the differences in the length, area, volume and other morphological parameters of erosion gully under seasonal changes. The results showed that: (1) The cross-sectional morphology of erosion gullies changed from "V" shape to "U" shape from the head to the tail in different seasons; (2) The length increase of erosion gullies caused by the gully advance and the gully tail retreat during the rainfall period was greater than that caused by the gully advance during the snow melt period; (3) The increase of erosion gully area in the precipitation period was greater than that in the snow melt period, but the changes of erosion gully area in different periods were different. The increase of erosion gully area in the precipitation period was mainly caused by the change of gully length and the large-scale collapse around the gully head, while the increase of erosion gully area was caused by the change of gully length and the expansion of gully bank in the snow melt period; (4)The variation of gully volume in the precipitation period was greater than that in the snow melt period, which was related to the variation of gully length, area and the shearing capacity of runoff. The undercut gully erosion capacity of runoff generated by rainfall in the precipitation period was greater than that generated by snow melt runoff in the snow melt period. The results can provide theoretical bases for the prevention and control of gully erosion.

Abstract:To investigate characteristics of nitrate nitrogen transport in purple sloped soils at different periods under different rainfall events, laboratory soil tanks and simulated rainfall installation were equipped to set each single and total 12 intermittent rainfalls, and nitrate transport characteristics during short and long time periods were discussed respectively. In each soil tank, eight observed points were designed uniformly along the soil profile. The results showed that the soil water and nitrate nitrogen of purple sloped soils transported evenly from the upper 15 cm depth soil layer to the foot slope of lower 35 cm depth soil layer. However, nitrate concentrations of observed points declined rapidly from initial 345.7 mg/L to 99.7 mg/L during the first 6 rainfall events of 12 intermittent rainfalls; mean nitrate concentrations decreased from 69.7 mg/L to 52.0 mg/L during the 7^th to 9^th rainfall event, and tended to stable. As rainfall occurred, nitrate nitrogen transported towards the lower and foot of sloped soils, and the top of slope showed minimal transport. In addition, the nitrate concentration of subsurface outflow was about 1/3 of that of subsurface soil water. Overall, subsurface nitrate loss showed rapid decrease after 3 rainfall events. This research provided better understanding for nitrate transport and loss mechanism of purple sloped farmland as response to intermittent rainfall events, which was from a bran-new perspective.

Abstract:In recent years, check dams on the Loess Plateau have played an important role in mitigating soil erosion and silting land for land reclamation. But compared with earth and rock dams, the flood control standard of check dams is not high, and the dam break is more likely to occur. Check dams are distributed in a number of small basins in the form of stairs, forming a complex dam system network, which brings great challenges for the correct evaluation of the risk of failure. This paper adopted a failure risk analysis model of check dam systems based on hydrological calculations in small watersheds and considered the complex inflow conditions and the corresponding calculation program FT-IWHR. Taking the check dam reinforcement project in the Xi'ao watershed in Shanxi Province as an example, under the checking conditions (the flood return period is 200 years), the current check dam system was analyzed for continuous collapse risk. At the same time, the feasibility analysis of the danger-removing and reinforcement scheme was carried out under the two working conditions of the current check dam system and the siltation surface of each dam reaching the design siltation elevation after a few years. The results showed that the current 8# medium dam did not meet the flood control standards, and the critical rainfall was only 133 mm. The critical rainfall would increase to 945 mm after adding the spillway of 6 m wide and 3 m high, and the critical rainfall would decrease to 886 mm after the siltation surface reached the siltation elevation. both of which could meet the flood control requirements. And the addition of a spillway could effectively reduce the risk caused by the rise of the siltation surface. The risk analysis method and practical application results of check dam system have certain reference value for flood control risk analysis and planning design of check dam system under extreme rainfall.

Abstract:The development of soil cracks endangers the stability of soil bund, further influences soil conservation. In order to reveal the law of crack development and the main influencing factors under water evaporation, a typical purple soil bund on sloping farmland in Beibei district of Chongqing was chosen to sample and test. Different levels of initial water contents (25%, 30%, 35%), dry densities (1.3, 1.4, 1.5 g/cm³) and reinforcements (0.05%, 0.15%, 0.25%) were defined to model the crack development process of purple soil bunds by using a set of simulated bunds. The crack development intensity, complexity indexes and the relationship between crack development and (initial) water content, dry density, and reinforcement were studied through image analysis. The results showed that the crack development process could be divided into three stages under water evaporation in terms of the initial stage, rapid crack expansion and stabilization. Under different initial water contents, the cracks intensity and complexity of all specimens increased rapidly with the decreasing water evaporation, and then tended to be stable at the water content of 12%. Dry density was an important factor impacting soil shrinkage and swell. Under the same initial water content, the cracks intensity and complexity increased as dry density increasing. The amount of reinforcement of polypropylene fiber was inversely proportional to the degree of cracks development. Comparatively, the initial water content had a great impact on the early stage of crack development in the process of water evaporation, but after the cracks began, the water content became a more important impacting factor, followed by the dry density and reinforcement. These results are expected to provide a basis for the design, construction, maintenance and management of soil bunds in purple soil area.

Abstract:To explore the effect and mechanism of soil physical crust on runoff and sediment yield on the Loess Plateau sloping farmland, so as to provide scientific basis for the prevention and control of soil and water loss on sloping farmland in the Loess Plateau, indoor artificial rainfall simulation experiment was conducted to study the influence of deposition crust on slope farmland and splashing crust formed after ploughing on the production process of runoff and sediment on slope. According to the crust formation characteristics of sloping farmland in the study area, five treatments were designed in the experiment, including bare land, deposition crust, deposition crust destruction, tillage and tillage splashing crust, and each treatment corresponded to two replicates. Taking the 25° slope of Ansai loessial soil as an example, the rainfall intensity was set to 120 mm/h and the rainfall duration was set to 1 h. The results showed that: (1) The deposition crust of sloping farmland promoted slope runoff and inhibited slope sediment yield. After breaking the crust, the total sediment yield was 19.28 times that of the original. (2) After ploughing, the total runoff decreased by 19.91%, but the total sediment yield increased by 14.67%. In addition, after ploughing the cultivated land and forming splashing crust, the total sediment yield was 4.08 times and 9.98 times that of the original, respectively. (3) The cumulative sediment amount increased as power function with the increasing of cumulative runoff. According to the coverage of topsoil crust on sloping farmland, the increase process could be divided into convex increase (crust coverage) and concave increase (no crust coverage). In summary, the deposition crust formed by sediment deposition drying at the ridge or grass belt under sloping farmland should be actively protected. The splashing crust formed by rainfall in the ploughed sloping land should be broken in time.

Abstract:The extensive use of dyed image analysis techniques in the research of soil preferential flow, optimization and improvement of dyeing image analysis methods, can promote in-depth study of the movement process of soil preferential flow, and quantitatively refine and analyze the developmental composition of preferential flow. Taking typical farmland sugarcane field as the research object, through field dyeing tracer experiment, using hue segmentation technology, combined with fractal and gray system theory, the preferential flow degree of sugarcane field soil in two typical farming methods (ridge and no-tillage) was quantitative analyzed and evaluated. The results showed that: under the same external water supply conditions, the preferential flow in the soil space of the ridged sugarcane field was scattered, clumpy and dot-like compared to the branch-like staining morphology of the no-tillage sugarcane field. The dyeing grade 1of the ridged sugarcane field, the fractal dimensions of 2 and 3 both decreased with the increase of soil depth. The preferential flow of "rapid change" in the top soil layer (0—10 cm) of ridged sugarcane field was 12.0 times that of no-tillage sugarcane field at the same depth, and the average percentage of preferential flow of "active" degree of no-tillage sugarcane field was 67.4%, which is 1.2 times that of ridged sugarcane land (54.2%). Bulk density had the greatest impact on the development of preferential flow in ridged sugarcane fields, and the degree of preferential flow decreased with the increase in bulk density. The saturated hydraulic conductivity of no-tillage sugarcane fields had the greatest impact on the development of preferential flow, and the degree of preferential flow decreased with decrease of saturated hydraulic conductivity. Ridge tillage affects the water content of sugarcane fields, speeds up the movement of water in the soil surface, reduces the development of deep preferential flows, reduces water infiltration, and can play a role in water storage and fertilizer preservation to a certain extent, can provide technical support for industry's production increase and increase related research of sugarcane planting in Guangxi.

Abstract:To explore the difference in shear strength of different plant root-soil composites and the influence of various factors on it, four different vegetation coverage areas including coniferous forest, broad-leaved forest, shrub, and grassland in Wenchuan County were selected as the study area. Sixteen dominant plant root-soil composites and unrooted bare soil original samples were prepared in the field, and indoor fast shear experiments were conducted. The enhancement effect of the typical plant roots on the shear strength and deformation resistance of the soil were analyzed. The gray correlation method was used to analyze the degree of influence of the roots and soil related factors on the shear strength of the root-soil composite. The results showed that: (1) The addition of 16 kinds of plant roots could improve the shear strength and deformation resistance of the soil to a certain extent, and the shear strength was mainly enhanced by increasing the cohesion of the soil. The cohesion of the root-soil composite was greater than that of the bare soil by 6.09%~153.27%. Different root systems had obvious differences in enhancing the cohesion of the soil. But the internal friction angle did not change significantly, and most of them were slightly smaller than that of the bare soil. (2) The gray correlation degree of each factor with cohesion and internal friction angle was relatively large, among them, the correlation degree between cohesion and dry density was the highest (0.803), followed by root weight density (0.793), and plasticity index was the lowest (0.626). The correlation between internal friction angle and plasticity index and dry density was relatively high (0.789, 0.700), D_c was the lowest (0.567), and the influence of root characteristic parameters on internal friction angle was not significant.

Abstract:The change of soil structure under freeze-thaw cycles is one of the main reasons for the aggravation of soil erosion on black soil slope during snowmelt period. The stability and microstructure of soil aggregates are the key factors affecting soil erodibility. Based on the controlled freezing and thawing simulation experiment, the dynamic characteristics of the microstructure of black soil aggregates during the freeze-thaw cycles were analyzed by using the wet sieving method, scanning electron microscopy (SEM) and Image Pro Plus (IPP) analysis. Moreover, the interaction between the water stability and the microstructure characteristics of soil aggregates was elucidated. The results showed that: (1) The destructive effect on soil aggregate stability was found during the freezing and thawing cycles. At the micro level, the freeze-thaw cycles derived soil pores to develop into long strips. With the increase of freeze-thaw cycles, the connectivity of soil pores and the area porosity increased. On the macro level, it showed that soil macro aggregates migrated to micro aggregates, and the water stability of aggregates decreased. (2) The increase of soil initial water content would enhance the damage degree of soil aggregate under freeze-thaw cycles, and there was a significant change within seven freeze-thaw cycles. With the increase of soil initial water content, the aggregate area porosity increased significantly. (3) Aggregate area porosity was significantly correlated to the mean weight diameter (MWD) and the geometric mean diameter (GMD). The increase of area porosity could explain 49.1% and 50.3% of MWD and GMD, respectively.

Abstract:Aiming at the problem of how to improve the gully land consolidation soil poor structure in the Loess Plateau, the vertical one-dimensional stable water potential infiltration experiments were conducted to explore the effects of different organic materials (bio-organic fertilizer, crushed straw, 50% crushed straw + 50% bio-organic fertilizer, Urea, CK) on gully land consolidation soil's wetting front movement, cumulative infiltration, infiltration rate, and soil water evaporation characteristics. Green-Ampt model, Philip model and Kostiakov model were used to fit and analyze the regularity of soil moisture infiltration. The results showed that: (1) Crushed straw and bio-organic fertilizer both reduced the soil water movement rate and enhanced soil water holding capacity; crushed straw simultaneously reduced the soil stable infiltration rate, which was 17.65% lower than CK. (2) There was a good linear relationship between wetting front depth and the cumulative infiltration; by fitting the three infiltration models, it was found that the Philp model and Kostiakov model had the best fitting effect, which were more in line with the Dynamic relationship between soil infiltration rate with time in gully land consolidation soil on the Loess Plateau. (3) In the process of soil water evaporation, adding crushed straw had a positive effect on blocking and accumulating soil moisture and increasing soil water content.

Abstract:To investigate the effects of soil hydraulic parameters on the long-range correlation of soil moisture under different climatic conditions, a 1-D vadose zone model (HYDRUS-1D) was utilized to simulate soil moisture time series under different climatic conditions in China (humid area, semi-arid area, and arid area) using generated soil hydraulic parameters datasets for sandy and clay loam soils. Then, the long-range correlation of soil moisture data was calculated by detrend fluctuation analysis. The results showed that: (1) The scale exponent (h) of the simulated soil moisture ranged from 0.570 to 1.915, indicating that there was an obvious long-range correlation. Soil moisture time series was mainly characterized by persistence for sandy, but for clay loam, there were both persistence and anti-persistence. (2) The long-range correlation was positively correlated with the soil depth, clay fraction, and aridity index. (3) The main soil hydraulic parameters affecting long-range correlation were n, α, and K_s. Specifically, n was the main hydraulic parameter affecting long-range correlation for sandy soils at all locations. For clay loam soils, α was the predominant hydraulic parameter affecting long-range correlation in humid area, α and K_s were the main hydraulic parameters affecting long-range correlation in semi-arid and arid areas. The results can provide some reference for revealing the long-term evolution mechanism of soil moisture.

Abstract:In order to determine the water use strategy of fruit-grass complex system in different habitats, we studied the hydrogen and oxygen isotopic values of soil water, xylem and stem water of single cropping apple (SA) treatment and fruit grass composite systems (apple+white clover (AW), apple+ryegrass (AR)) in Yangling of Guanzhong and Luochuan of Northern Shaanxi. Direct comparison method and IsoSource model were used to analyze the water use strategy of fruit-grass complex systems in different seasons under different habitats. The results showed that under different habitats, the vertical fluctuation of soil water content of orchard in Yangling area was larger than that in Luochuan area. The consumption of soil water in 40—80 cm layer in Yangling was greater than that in Luochuan. The planting of white clover in Yangling orchard in dry season would increase the consumption of deep soil water. In the dry season, the depth of soil water mainly used by apple trees was 40—100 cm (63.0%), and that of the forage was 0—20 cm (65.0%). The water use level of apple trees in Yangling was lower than that in Luochuan. The depth of soil water used by apple trees in SA and AW was 20—40 cm (54.3%), that in AR was 40-100 cm (65.0%). The depth of soil water used by white clover and ryegrass was 0—20 cm (59.3%) and 20—40 cm (62.2%), respectively. In the rainy season, the water source layer of apple trees in both places were the same, the depth of soil water used by apple tree in SA was 20—40 cm, that in AW and AR was 40—100 cm. And the forage intervention moved down the water absorption layer of apple trees. The results indicated that the fruit-grass complex system could adjust its water use strategy with the seasonal changes in different habitats. The fruit-grass complex system in Luochuan area responded more quickly to the water change, and increased the use of deep soil water when water was insufficient to avoid water competition. And it had a better adaptation mechanism to habitat heterogeneity than that in Yangling. In Yangling area, the fruit-grass complex system could store soil water, but would increase the consumption of deep soil water in the dry season, so it should be supplemented with irrigation timely.

Abstract:In order to evaluate the effectiveness of the ecosystem restoration project implemented in Kangping County, Shenyang City, Liaoning Province, since 1999, the temporal and spatial distribution characteristics of the land surface ecosystem in Kangping area were interpreted by using multi-period landsat images. The pattern of the land surface ecosystem in Kangping area since 1984 were studied by using the research methods such as the regression analysis of climate elements, the ecosystem transfer matrix and the comprehensive human disturbance index of the ecosystem. In particular, the temporal and spatial changes of the ecosystem in the past 20 years since the implementation of the ecosystem restoration project were explored and the driving force mechanism of its evolution was analyzed. The results showed that: (1) During 1999—2020, the ecological system pattern of Kangping area changed significantly, which was mainly reflected in reduction of the proportion of sandy land by 35.391%, reduction of the proportion of cultivated land by 6.240%, and a substantial increase in the area of forest land. (2) Through regression analysis of climatic elements, we found that the overall climate in Kangping area became wet during the study period, especially after the implementation of the ecosystem restoration project, which was suitable for the growth and restoration of land surface vegetation. Finally, it was concluded that the main driving force for the evolution of the ecological system pattern of Kangping area was a series of ecosystem restoration projects implemented in the region since the end of the last century, and the auxiliary driving force was the decrease of the days of the sand-driving wind per year the climate humidification in the region.

Abstract:In order to explore the influence of the gravel interbed on the carbonate-derived laterite hydraulic properties, indoor soil column infiltration and vertical infiltration experiments were conducted to examine the relationship of 3 different gravel volume contents (0, 40% and 80%) and 3 different gravel burial depths (0, 5 and 15 cm) between the cumulative infiltration, wetting front, infiltration characteristics, and soil water characteristic curves. The applicability of the traditional soil infiltration model was analyzed by three models. These Brooks-Corey model parameters were inverted by the measured infiltration data and the modified Green-Ampt model. The results showed that the cumulative infiltration, wetting front, initial infiltration rate, average infiltration rate, and steady infiltration rate obviously decline, along with the increase of the gravel content at the same gravel burial depth. When the gravel content was 40%, the largest soil steady infiltration rate (12.71 mm/h) was found in gravel burial depth of 15 cm, which was 1.33 times higher than that of 0 cm. The Horton equation's validation of the infiltration characteristics were superior to those expressed by the Kostiakov model and Philip formula. At the same gravel burial depth (0 and 5 cm), the inverted parameters a, n, and h_d increased with the increase of gravel content, while K_s decreased. The soil water retention of control group was the lowest, and the soil water retention of the gravel interbed decreased with the increase of the gravel content. However, when the gravel burial depth was 15 cm, the soil water retention of the gravel interbed increased with the increase of the gravel content. As the gravel content arrived at 40%, the relationship of soil water retention in different gravel burial depths was 0 cm > 5 cm > 15 cm. These results can provide data reference for the taking advantage of water resource in the southwest karst regions.

Abstract:To explore the correlation of species diversity and aboveground biomass and the vertical variation of species diversity, taking five grassland types in the Buerjin forest area of Altai mountains as the research object, the species diversity change characteristics of various grassland types were analyzed through the investigation of various grassland types in Buerjin forest area in Altai Mountains. The results showed that: (1) There were significant differences in aboveground biomass among the five grassland community types. The aboveground biomass of the desert grassland and mountain meadow grassland was lower, that of the mountain grassland was the highest, while that of the mountain meadow and alpine meadow was between them. (2) There are significant differences in the species diversity index, dominance index, richness index and evenness index among different grassland types. The species dominance, diversity and evenness of alpine meadows were the best, and the abundance of the mountain grasslands was significantly better than that of other grassland types. (3) Aboveground biomass was only significantly related to dominance and diversity in mountain meadow grassland and mountain meadow, but there was no significant correlation between aboveground biomass and species diversity in desert grassland. (4) In the range of 900~2 400 m above sea level, the changes of the species dominance, richness, evenness and diversity index of grassland communities were basically the same, showing a trend of first rising, then falling and then rising, reaching peaks in the 1 200~1 400 and 2 200~2 400 m zones. The results would provide some conference and further understanding for the distribution pattern of grassland and its functions in the Buerjin forest area of Altai mountais.

Abstract:In order to explore the eco-environmental effects and formation mechanism of land spatial transformation, taking Harbin section of Songhua River Basin as an example, the grid element method was used to analyze the temporal and spatial differentiation characteristics of eco-environmental effects of land spatial transformation by combining eco-environmental quality index, global autocorrelation model and kernel density function, The driving mechanism of spatial differentiation of eco-environmental quality was revealed with the geographic detector model from 1986 to 2016. The results showed that: (1) Ecological-production-living space was mainly production space, in which agricultural production space and forestry ecological space accounted for the largest proportion. The production space and ecological space decreased, and the living space increased in study area from 1986 to 2016; (2) During the study period, the eco-environmental quality was basically stable and showed a slight downward trend as a whole, indicating that the eco-environmental quality had deteriorated. In terms of spatial distribution, the eco-environmental quality index had significant and positive spatial autocorrelation, showing a spatial pattern of "dense in the South and sparse in the north", "dense in the edge and sparse in the middle", and there was a phenomenon of agglomeration in space; (3) The main controlling factors of spatial differentiation of eco-environmental quality were the distance to water area and the distance to roads above township level. The interaction between various factors was mainly nonlinear enhancement, and the interaction within socio-economic factors was obviously stronger than that between natural factors and socio-economic factors. The combined action of multiple factors leaded to the spatial differentiation of eco-environmental quality in the study area.

Abstract:In order to deeply explore the driving factors of urbanization on ecosystem service value and the spatial spillover effect of ecosystem service, taking the county of Shanxi Province as the research unit, based on the land use data and socio-economic data from 2000 to 2018, constructs a comprehensive evaluation system of ecosystem service value and urbanization level, and analyzes the spatial characteristics of the correlation between urbanization and ecosystem service value through bivariate spatial autocorrelation, In addition, the spatial econometric model is used to explore the driving factors of urbanization on ecosystem service value and the spatial spillover effect of ecosystem service. The results showed that: During the study period, the ecosystem service value of Shanxi Province showed a downward trend as a whole, and the comprehensive level of urbanization was significantly improved, but the overall level was low. There is a significant negative correlation between urbanization and ecosystem service value in the study area, showing a U-shaped development trend. The results of spatial econometric model show that the urbanization rate, built-up area and ecosystem services are significantly negatively correlated, while the per capita retail sales of social consumer goods and the square of urbanization level are significantly positively correlated with ecosystem services. Ecosystem service value has a positive spillover effect on neighboring counties. Under the premise of controlling other explanatory variables unchanged, every 1% increase in the ecological value of neighboring counties will have a 0.243% promotion effect on the county. Ecosystem services in the study area are integrated and unstable, which makes the county governments lose their enthusiasm for environmental protection.

Abstract:Under the background of climate change, the increase of the frequency and intensity of extreme precipitation events directly affects regional ecological security. Analyzing the tempo-spatial variation characteristics of extreme precipitation is of great significance for regional risk assessment. Based on the daily precipitation data of 22 meteorological stations in Shanxi Province from 1960 to 2019, 12 extreme precipitation indices were selected, the tempo-spatial variation characteristics of extreme precipitation in Shanxi Province during past 60 years were studied by using the methods of linear trend analysis, Mann-Kendall trend test, mutation analysis, Morlet wavelet analysis and Inverse Distance Weighted (IDW) interpolation. The results showed that: (1) A trend of drought was detected in Shanxi Province, and the number of rainfall days (R1MM) exhibited a significant downward trend. (2) Some extreme precipitation indices experienced a mutation around the 1970s, meanwhile, a significantly downward trend was detected after the mutation. (3) The variation of extreme precipitation had the main cycle of about 17 years, some indices had periodic changes around 7~8 years or 4~5 years. (4) The southwestern part of Shanxi Province showed a trend of drought, while the extreme precipitation events in northwestern part showed an increasing trend. The results of this study provided references for the implementation of countermeasures in response to extreme precipitation events in Shanxi Province.

Abstract:In order to explore the characteristics of the propagation process of meteorological drought to hydrological drought in karst region, the SPI and SRI standardization indexes were used to identify regional drought, and methods of cross wavelet, wavelet coherence and state transition probability were used to explore the drought propagation characteristics such as propagation intensity and response rate. The results showed that: (1) The duration of meteorological drought and hydrological drought in the 60 s and 70 s of the last century was shorter, while the regional droughts in the 80 s of the last century and the early 21st century lasted longer. There was a significant positive correlation between SPI and SRI, and the process of meteorological drought tended to hydrological drought took 1.5 months. (2) The transmission intensity of drought DPI in the karst area was greater than 1 and the response rate was relatively high. Hydrological drought was extremely sensitive to the occurrence of meteorological drought, especially in areas where the cutting depth of the surface was relatively shallow and the karst development was relatively strong. (3) The propagation process was mainly affected by the cutting depth of the surface. The influence degree of each underlying surface condition to the drought propagation process was sequenced as surface cutting depth> karst development intensity> elevation> topography and landforms, among them the characteristics of drought propagation was significantly negatively correlated with the depth of surface cutting, and positively correlated with the intensity of karst development, elevation, and topography. In the areas with shallow cut, medium cut, or low altitude and strong karst development, the transfer of DPI and Rr between each grade was more active. On the whole, the propagation characteristics showed an increasing trend in 57 years. The results could provide a theoretical basis for drought prevention and monitoring in karst areas, especially for the sustainable development planning of ecologically fragile areas.

Abstract:In the context of global warming, drought disasters are becoming more frequent. In order to comprehensively and finely study the temporal and spatial changes of precipitation in central China from 2010 to 2019, this study combined remote sensing data of water vapor (PWV), enhanced vegetation index (EVI), elevation, slope, and aspect, based on the geographically weighted regression model combined with Kriging Interpolation (GWRK), the GPM IMERG and TRMM 3B43 data from 2010 to 2019 were spatially downscaled, and the data of 53 meteorological stations in the area were used for accuracy evaluation. For the optimized downscaling data, the coefficient of variation method, Theil-Sen Median trend analysis coupled with the Mann-Kendall significance test method and the Hurst index method were used to analyze the temporal and spatial characteristics of precipitation changes and sustainability characteristics in Central China, and future precipitation trends were predicted. Finally, the NPA (Normalized Precipitation Anomaly) and the SPEI12 (standardized precipitation evapotranspiration indices) were constructed to realize the spatio-temporal monitoring of drought in the study area. The research results showed that the details of the precipitation data are enhanced after downscaling, and the overestimation of the original data can be effectively improved. The downscaling data of GPM data was closer to the measured data than the downscaling data of TRMM. In the past 10 years, the temporal and spatial distribution of precipitation in Central China were quite different, with high fluctuations and high fluctuations in precipitation accounting for 69.21% of the entire region. The precipitation changes during the 10 years were dominated by non-significant changes, of which slightly increased areas accounted for 54.88% of the entire region, and slightly decreased areas accounted for 40.41% of the entire region. The future trend of precipitation in Central China was dominated by a continuous increase, mainly distributed in the northern part of the region. Areas with uncertain future trends accounted for 21.63% of the entire region, mainly concentrated in Hunan. There were great differences in the spatial distribution of NPA in Central China. As a whole, it was in a state of drought-free and light-drought disasters. NPA and SPEI₁₂ had a relatively good correlation, and all years had passed the 0.05 significance test, which can be to a certain extent Reflect the drought in Central China. Downscaling data can reflect the temporal and spatial dynamic changes of precipitation in more detail, and is of great significance for accurate monitoring of drought and flood disasters, guiding agricultural production and promoting sustainable economic development.

Abstract:Accurate identification of the temporal and spatial evolution law and trajectory characteristics of land use pattern is of great significance to scientifically promote ecological protection and high-quality socio-economic development in the region. Three periods of land use data in 1990, 2005 and 2018 were used to construct the trajectory sequence of land use change in the southwest Hubei. In order to reveal the spatial and temporal evolution characteristics and change trend of land use pattern in the southwest Hubei over the past 30 years, using various indices of land use change, chord diagram visualization and standard deviation ellipse methods, this study carried out from three aspects: total land use change characteristics, quantitative change trajectory characteristics and spatial change trajectory characteristics. The results showed that: (1) Stability characteristic of total land use change was obvious. Forestland and cultivated land were always been the main land use types in the study area. The area of cultivated land decreased continuously, while the area of built-up land increased continuously. The change of land use was active, but the overall trend was flat. (2) The dominant characteristics of the quantitative change trajectory of land use pattern were obvious. From 1990 to 2005, it was dominated by the mutual conversion between cultivated land and forestland and outflow of forestland. From 2005 to 2018, it was dominated by mutual conversion between cultivated land, forestland and grassland and further expansion of built-up land. On the whole, the change of land type was manifested in the transfer of spatial location. Land use change types were more diverse, and land use change behavior was more active in 2005—2018 than those in 1990—2005. (3) The spatial change trajectory was characterized by significant clustering and divergence. From 2005 to 2018, the dynamics change intensity of comprehensive land use was greater. There were spatial variations in the center of gravity, area, direction and diffusion trends of land use pattern change in the study area over the past 30 years. The results could provid a reference basis for land use research and territorial spatial planning in the southwest Hubei Province.

Abstract:Scientifically identifying regional hydro-ecological space and analyzing its distribution characteristics were of great significance to the planning of hydro-ecological space and the regulation of hydro-ecological space problems such as flood disasters. Taking Linli County, Hunan Province, as the research area, this study constructed a classification system of hydro-ecological space with the help of GIS and RS platform, regional explicit hydro-ecological space was identified, and the three types of recessive hydro-ecological spaces of regional water conservation, soil and water conservation and flood regulation were visualized. And the distribution characteristics of each water ecological space were quantitatively analyzed. Finally, explicit and recessive hydro-ecological spaces that were integrated were superposed with current land use map for analysis. The results showed that: (1) Explicit hydro-ecological space occupied 4.73% of total area of Linli County, which distributed in dots, patches, bands and branches in the county, and located in a low-altitude, relatively gentle slope area. (2) The area of recessive hydro-ecological space accounted for 49.97%, which was less than 69.68% of the total area of water conservation, soil and water conservation and flood regulation space, which accounted for 15.44%, 38.07% and 16.17%, respectively, showing the characteristics of "small concentration and large dispersion". The identification results intuitively reflected spatial distribution characteristics of maintaining regional hydro-ecological security. (3) Hydro-ecological space accounted for 49.99% of total area of Linli County, which mainly distributed in the areas around Daoshui, Lishui and its tributaries. Small and medium-sized reservoirs were scattered in patches. (4) The proportions of cultivated land and construction land in hydro-ecological space were 44.40% and 21.19%, respectively, indicating that there was an overlapping space between hydro-ecological space and non-ecological land types with intensive human activities. This study revealed that current land use was in conflict with the hydro-ecological space in Linli County. The non-ecological land types in the hydro-ecological space could be re-planned later, in order to efficiently protect hydro-ecological space and avoid safety issues of hydro-ecological.

Abstract:Land use change is the main driving force of regional carbon emissions change, and revealing the impact of land use change on carbon emissions is instructive for the formulation of carbon emission policies. However, research on the impact of land use change on carbon emissions in areas with rapid economic development is still limited. Taking Anhui Province as objective, this study evaluated the net carbon emissions from the perspective of carbon source/sink based on the land use change from 2000 to 2020, analyzed the spatio-temporal characteristics of carbon emissions, and clarified the carbon emission effect from the aspects of carbon footprint, ecological carrying capacity and ecological deficit. The results showed that: (1) During 2000 to 2020, the net carbon emissions from land use in Anhui Province increased, with an average annual increase of 5 039 200 tons. Forest was the main carbon sink, but the amount of carbon sinks varied little from year to year. Construction land was the main carbon source, with an average annual increase of 5 113 700 tons. (2) During 2000 to 2020, the carbon source change area was mainly distributed in the central and northern plain area of Anhui Province, and the carbon sink change area was mainly distributed in the mountainous of southwest. Furthermore, the central and northern area of Anhui Province was the hottest areas of the carbon emission intensity changes. (3) Among the carbon emission effects caused by carbon source/sink changes, the ecological carrying capacity did not change much from 2000 to 2020, but the carbon footprint and ecological deficit increased, with an annual increase rate of 6.2% and 8.7%, respectively. Therefore, the central and northern plain area of Anhui province was the key control area for implementing carbon emission reduction. Meanwhile, reducing the construction land and increasing forest area could effectively adjust the carbon emission effect in study area.

Abstract:Soil moisture is one of the key factors affecting the ecological processes and ecological carrying capacity of alpine meadows in the Qinghai-Tibet Plateau. Mastering its change characteristics is of great significance for ecological protection and restoration in alpine region. Based on the soil moisture data monitored by hobo soil temperature and humidity instrument (HOBO Data Loggers-Onset Corporation of USA), soil moisture change characteristics during August 2019 and August 2020 of three layers L1 (0—5 cm), L2 (5—15 cm) and L3 (15—30 cm) of alpine meadow topsoil under different degradation stage sites, which were non-degradation (ND), light to moderate degradation (LMD), highly degradation (HD), in the Three-River Source Region were analyzed. The results showed that: (1) There were significant seasonal variations in soil water content under different degradation stages. The high values mainly distributed in summer, while the low values distributed in winter and spring. The intra-annual mean values of topsoil water content under different degradation types followed the order of LMD (0.320 cm³/cm³)> ND (0.284 cm³/cm³) >HD (0.211 cm³/cm³). (2) After continuous rainfall in summer, the soil water content began to decrease significantly after 24 hours. Among them, the change range of L1 layer was the largest and that of L3 layer was the smallest. (3) The soil depth of 0—5 cm in ND and LMD alpine meadows, and the 5—15 cm of HD alpine meadows corresponded to a higher water content layer, because that the soil water content was significantly negatively correlated to soil water content and soil capacity, and significantly positively correlated to C/N and organic carbon.

Abstract:The Pinus tabulaeformis plantation of severely burned areas in Beijing was taken as the research object, based on in situ sampling method and indoor immersion method, litter samples were collected in control plot and burned plot from July 2020 to December 2020 and their standing crops, water holding capacity and effective retention were measured and analyzed to explore the decomposition and hydrological effects of litter under the interference of forest fire. It could provide a basis for giving better exerting the function of forest water conservation and soil and water conservation. The results showed that: (1) The average standing crop of litter in semi-decomposed layer and decomposed layer of Pinus tabulaeformis plantation were 16.18 t/hm² (leaves proportion > 80%) and 31.88 t/hm², the average thickness were 2.77, 2.79 cm, respectively. Compared with the control plot, the litter thickness and standing crop of the semi-decomposed layer after fire were decreased by 39.35% and 53.77% respectively. (2) The average natural moisture content of litter in semi-decomposed layer (41.94%) was slightly higher than that in decomposed layer (36.07%) in Pinus tabulaeformis plantation, and the average maximum water holding capacity was 201.88%, which was lower than that of decomposed layer from July to September, and vice versa from October to December. The average maximum water holding capacity and effective retention in semi-decomposed layer were 35.80, 19.85 t/hm², which were significantly (P < 0.05) lower than those of decomposed layer from August to December (69.28, 46.64 t/hm²). Compared with the control plot, the natural moisture content, maximum water holding rate, maximum water holding capacity and the effective retention of litter in semi-decomposed layer after fire were decreased by 32.19%, 13.36%, 60.05% and 62.47% respectively. (3) In the 24-hour immersion process, the litter water holding capacity and water absorption rate in semi-decomposed layer were lower than those of decomposed layer from July to September, and vice versa from October to December. The water holding capacity and water absorption rate of litter after fire in semi-decomposed layer were lower than those in control plot. In conclusion, the decomposition of litter (semi-decomposed layer) in Pinus tabulaeformis plantation was first fast and then slow, and the decomposition was accelerated after burning. The indexes of water holding capacity and water holding processes of litter mainly showed that decomposed layer was higher than semi-decomposed layer, and non-burned was higher than severe burned, that is, the hydrological effects of litter was affected by the decomposition stage and burning.

Abstract:With the intensification of global warming, the rainfall pattern is also changing. Soil enzymes are the important participants in the chemical process of forest ecosystem and can quickly reflect the changes of soil environment. Therefore, studying the response of extracellular enzymes activities in subtropical soil to precipitation changes can effectively evaluate the impact of climate change on soil organic matter decomposition and transformation. In this study, the natural Castanopsis carlesii forest in Castanopsis kawakamii Nature Reserve of Sanming, Fujian Province was selected, and three treatments were set up, including control (CT), 30% of throughfall excluded (TE1) and 60% of throughfall excluded (TE2). In September 2020, soil samples of different soil layers (0—10, 10—20, 20—40, 40—60 cm) in each treatment were collected to study the effects of 9-year throughfall exclusion on soil enzymes activities. The results showed that the activities of β-glucosidase (βG), β-N-acetylglucosaminosidase (NAG) and acid phosphatase (AP) in the four soil layers decreased after throughfall exclusion. Compared with CT, the activities of AP, βG and NAG in 0—40 cm soil under TE2 treatment were significantly decreased (P <0.05), and the activities of AP in 40—60 cm soil under TE1 and TE2 treatments were also significantly decreased. With increasing soil layers, the activities of three extracellular enzymes decreased. Redundancy analysis (RDA) showed that soil moisture content (SWC), total nitrogen (TN) and soluble organic carbon (DOC) were the main factors regulating the activities of soil extracellular enzymes in 0—10 cm soil, while DOC and ammonium nitrogen (NH₄⁺—N) in 10—20 cm, and soluble organic nitrogen (DON) and nitrate nitrogen (NO₃^-—N) in 20—40 cm. In 40—60 cm soil, the C∶P ratio mainly influenced the extracellular enzymes activities. In conclusion, the responses and regulatory factors of soil extracellular enzymes activities to the decrease of precipitation were different at different soil depths. The results of this study are helpful to further understand the mechanism of soil nutrient transformation and cycling in subtropical forests under global climate change.

Abstract:The effect of groundwater salinization on the stability of soil aggregates and the organic carbon pool was explored using the soil in seasonally humid area and the perennial dry area of Bayinbuluk alpine wetland. Four levels of groundwater were used in this study including control (NaCl 0 g/L), brackish water (NaCl 2 g/L), salt water (NaCl 6 g/L), and brine water (NaCl 23 g/L). The soil aggregates were classified into different sizes by wet sieving method. Results showed that the groundwater salinization had not significant effect of soil aggregates in 0—10 cm depth, but had a significant effect on the percentage of soil aggregates in 10-30 cm depth. With the increase of salinity, the percentage of soil aggregates > 2 mm first decreased and then increased. In 10—30 cm soil cglayer, the lowest values of the percentage of soil aggregates > 2 mm with the value between 1% and 14% were found in the 2 g/L treatment, while the values (5%~56%) increased significantly in the 23 g/L treatment. The percentage of soil aggregates > 2 mm in seasonally humid area was higher than that in perennial dry area. The mean weight diameter (MWD) and geometric mean diameter (GWD) in seasonally humid area increased first and then decreased with increasing soil depth, while MWD and GMD in perennial dry area decreased with increasing soil depth. MWD and GMD in 0—10 cm depth were significantly higher than those in other soil depths, and MWD (0.71~3.59 mm) and GMD (0.25~1.64 mm) under the 23 g/L treatment in 10—30 cm depth were significantly higher than those under the other treatments. Content of aggregate associated organic carbon in 0—10 cm depth first increased and then decreased with decreasing aggregates size. Content of aggregate associated organic carbon in 20—30 cm depth had similar change trend as in the 0-10 cm depth. Contents of soil organic carbon in 2~0.25 mm soil aggregates under the 6 and 23 g/L were significantly higher than other treatments. In conclusion, the groundwater salinization had a significant effect on the soil aggregates stability and organic carbon content in the 10—30 cm depth in the seasonal humid area and the perennial area, and the groundwater salinity of 2 g/L have damage effects on soil aggregates, which reduces the stability of the soil aggregates. The salinity with the value of 23 g/L has mild protective effect on > 2 mm soil aggregate. With decrease of the aggregates size, the soil organic carbon content reduces, and the content of macro-aggregate (> 0.25 mm) associated organic carbon is higher than other soil aggregates.

Abstract:In order to explore the changes of vegetation community characteristics and soil environmental factors in the 50 a plantation of Caragana korshinskii in the sqndy-hilly area of northwest Shanxi Province, the changes of growth characteristics, soil water content, soil nutrients and plant community characteristics of C. korshinskii were analyzed in 0 (abandoned land), 12, 18, 40 and 50 years. The results showed that: (1) With the increase of planting years of artificial C. korshinskii forest, the coverage and height of C. korshinskii increased significantly in the time gradient. Specifically, the coverage of C. korshinskii in the late planting period (40~50 years) was 1.98 times of that in the early planting period (0~12 years), while the height was 1.48 times of that in the early planting period (0~12 years). However, the density of C. korshinskii decreased significantly with the increase of planting years, from 0.35 plants/m² in the early planting period (0~12 years) to 0.11 plants/m² in the late planting period (40~50 years). (2) Soil environmental factors gradually recovered with the increase of planting years of artificial C. korshinskii forest, which showed that the SOC, pH, AN, and AK increased on the time gradient, and the SW, SS, and AP decreased. The restoration degree of 0—20 cm surface soil was higher than that of 20—100 cm soil. (3) In the early stage (0~12 years), the recovery rate of soil nutrients was significantly lower than that in the middle and late stage (12~50 years). The shrub had a significant enrichment effect on soil nutrients (0—20 cm). With the extension of the establishment time of the plantation, during the late planting period (40~50 years), the area of islands of fertility extended to the shrub. (4) With the increase of planting years in artificial C. korshinskii forest, the soil environment improved, the species and quantity of herbaceous plants increased significantly, and the dominant species also changed, from the pioneer annual species (Artemisia dalai-lamae and Avena fatua) as the dominant species in the early planting period (0~12 years) to the dominant perennial herbaceous species (Elymus dahuricus) in the middle and late planting period (12~50 years). The natural semi-shrub (Artemisia gmelinii) invaded, and the simple artificial C. korshinskii forest changed to the complex shrub community. (5) Planting artificial C. korshinskii forest had an obvious role in promoting soil environmental factors and community diversity. Through different types of plant community and soil environmental factors of RDA constraint sorting analysis diagram, artificial forest of C. korshinskii, annual herb, perennial herb and natural subshrub and soil environmental factors (SW, soil nutrient index) showed significantly correlation. Different types of plant communities and soil environmental factors were interrelated and mutually restricted to form a relatively stable community structure. The planting of C. korshinskii forest has important reference value for community restoration and ecological environment reconstruction in arid and semi-arid areas.

Abstract:To understand the status of soil water and salt and its migration laws during the freezing and thawing period in the farmland shelter forest in the Hetao Irrigation District of Inner Mongolia, the soil moisture, salinity, temperature and related meteorological data were measured and analyzed from October 2020 to April 2021. The results showed that the surface soil temperature changed significantly, and leveled off as the increasing soil depths. The rate of temperature decrease during the freezing period was greater than the rate of temperature rise during the thawing period. Considering the hysteresis of soil temperature changes, the freezing period was about 10 days shorter than the thawing period. Seasonal freezing caused the increased water content in the surface soil, and the dereased soil water content in the deep layer. During the thawing period, the soil water content gradually decreased. The surface soil water content in the farmland edges (0.3 H, 4 H) of the forest belts on both sides was smaller than that of farmland (1 H, 2 H, 3 H). The phenomenon of low soil water content in forest belts gradually disappeared with the deepening of soil layers. There was almost no difference in soil water content at different distances from the forest belt in 100 cm soil layer. During the freezing and thawing period, the salt content in soil increased. Soil freezing caused salt to accumulate in various soil layers. During the thawing, soil salt accumulated to the surface layer, and salt reduced in the deep soil. The degree of soil salt accumulation in farmland near forest belt was stronger than that in far forest belt. The transports of water and salt in soil basically showed a significant correlations, and the variability of salt was greater than that of water, indicating that the process of salt transport was more complicated. The results of this study revealed the law of soil water and salt movement in the farmland within the protection forest during the freezing and thawing period, and could provide a basic theoretical basis for agriculture in the irrigation area.

Abstract:Sediment carrying in water is the essential difference between muddy water irrigation and clean water irrigation. The muddy water and clean water film-hole irrigation free infiltration experiments were conducted to reveal the water-saving and infiltration reduction mechanism of muddy water irrigation. The changes in the infiltration capacity of muddy water film-hole irrigation, the movement distance of the wet front, the moisture content of the wet body, the soil particle composition of the dense layer, and the thickness of deposition layer with the infiltration time were studied. The quantitative model between the soil moisture content and the wet front movement distance was proposed, the relationship between the thickness of deposition layer and infiltration time, and the relationship between the retention amount and the depth of stranded layer had been established respectively. The results showed that sediment in muddy water had a greater influence on soil water infiltration. At the end of the infiltration, the cumulative infiltration of muddy water compared with clear water decreased by 27.83%. The soil moisture content decreased gradually from the center of film hole to the wetting front, the decreasing rate of soil moisture content increased gradually, and the distribution of soil moisture content in the radius of the wetting body was an elliptic curve. The relative content of fine particles in deposition layer was less than that of muddy water sediment, and its physical clay content was significantly lower than that of muddy cement sediment. The infiltration depth from the soil surface to 6 cm could be used as the stranded layer of the film-hole irrigation with muddy water. The content of fine particles in the stranded layer was more than that of the original soil. With the increase of infiltration soil layer depth, the difference between the soil particle composition of the stranded layer and the original soil gradually decreased, and the retention volume of fine sediment particles decreased with the increase of the depth of the stranded layer.

Abstract:Deep application of nitrogen (N) fertilizer helps to increase crop yield in dryland area, but the effect of depth of N fertilizer on wheat yield in hilly and gully regions of the Loess Plateau under different precipitation types is still unclear. This study used the meteorological data from 1990 to 2020, to explore the effect of N application depth on wheat yield in different precipitation types based on APSIM model and mathematical statistical methods. The correlation coefficient (R²) of the simulated and observed value of wheat yield and biomass was greater than 0.9, the model validity index (M_E) was greater than 0.8, and the normalized root mean square error (NRMSE) was less than 0.2, indicating that the model had good applicability in this region. The NRMSE of simulated and observed soil moisture dynamics during the growth period and soil profile moisture content at the harvest stage of the wheat field were 0.05 ~ 0.07 and 0.13 ~ 0.29, respectively, demonstrating that the model could accurately simulate the wheat field soil moisture changes. The yield potential of deep application of N fertilizer was the highest in wet years, followed by normal years. Compared with drought years, increasing the depth of N application in wet and normal years under the same nitrogen application rate could improve the stability and sustainability of farmland productivity. When the nitrogen application level was 150 kg/hm², increasing the depth of N application in wet and normal years had no obvious effect on the stability of farmland productivity, but it helped to improve the sustainability of farmland productivity. The interaction relationship between N application depth and amount and yield under different precipitation types showed that the relationship between wet years and normal years was better, with R² of 0.76 (P < 0.05) and 0.61 (P < 0.05), respectively. Increasing the depth of N application to 20 ~ 23 cm could obtain the highest potential yield. In a drought year, R² was 0.29 (P > 0.05), increasing the depth of N application had no significant effect on wheat yield. The results of the study are expected to provide theoretical guidance for optimizing fertilization measures at the regional scale for wheat in the hilly and gully regions of the Loess Plateau.

Abstract:This study was carried out to explore the reasonable utilization of brackish water in areas irrigated with brackish water and freshwater is short. This study set four treatments, including, reclaimed water irrigation(T1), mixed irrigation of 1∶2 with brackish water-reclaimed water (T2), mixed irrigation of 1∶1 with brackish water-reclaimed water (T3) and brackish water irrigation (T4), and took tap water irrigation (CK2), bare land irrigation with tap water (CK1) and bare land irrigation with 1∶1 with brackish water-reclaimed water (CK3) as the control, of which the saline degree of brackish water was 5 g/L. Based on the pot experiments, we measured the data of soil water content, soil salt content, water drop penetration time (WDPT), soil organic matter content, and soil enzyme activities including soil sucrase (S-SC), soil alkaline phosphatase (S-AKP/ALP), soil urease (S-UE), soil polyphenol oxidase (S-PPO), and analyzed the their responses to the mixed irrigation with different ratios of brackish water to reclaimed water. Finally, the index of integrated biological response version 2 was used to evaluate the impact of mixed irrigation on soil. The results indicated that: (1) Compared to T1, soil water content and soil salt content gradually increased significantly with the increase of the proportion of brackish water in the mixed solution on the whole. (2) Compared to T1, soil contents of K⁺ and Ca²⁺ had slight descending trend, soil contents of Na⁺ and Cl^- increased obviously, soil SO₄^2- content improved significantly, and soil Mg²⁺ content changed with no obvious trend with the increase of the proportion of brackish water in the mixed solution. (3) There were no significant differences in soil WDPTs and soil organ matter contents between T1 and CK2. Compared to T1, soil WDPTs and organic matter content had the ascending trend with the increase of the proportion of brackish water in the mixed solution. (4) The responses of different soil enzyme activities to different mixed irrigation with brackish water and reclaimed water were different. S-SC activity in T2 was the highest, S-UE activity in T3 was the highest but had no obvious differences from other treatments, and S-PPO activity in T4 was the highest following by T3 and no significant difference between them. (5) The index of IBRv2 in T2 was the lowest, and the value was 6.89. Therefore, considering soil environmental indexes and the limits of reclaimed water, reclaimed water could be used as an alternative source of fresh water in combination with brackish water, and mixed irrigation of 1∶2 with brackish water-reclaimed water is recommended based on the index of IBRv2 in short fresh water resource and areas irrigated with brackish water.

Abstract:It is meaningful to clarify the effects of tea planting on total nitrogen and mineral nitrogen in soil aggregates for providing a theoretical basis of applying nitrogen fertilizer. The effects of different tea cultivars (Fuding Dabaicha, Chuancha No. 3, Chuannong Huangyazao and Chuanmu No. 217) on total nitrogen and mineral nitrogen content in soil aggregates were studied by field investigation and indoor analysis. The results showed that: (1) As the decrease of particle size, the content of aggregates in each tea planting soil decreased firstly and then increased. The content of >2 mm aggregate was significantly higher than that of other aggregates, accounting for about 38.32%~66.26% of the total content. (2) With the decrease of aggregate particle size, the total nitrogen content of the soil of each tea cultivar decreased firstly and then stabilized, while the contents of ammonium nitrogen and nitrate nitrogen showed the opposite trend. (3) The contents of each nitrogen component in the soil of planting Fuding Dabaicha were higher than those of other cultivars. The trend of mineral nitrogen content in different soil layers was similar. (4) The reserves of each nitrogen component were the highest in > 2 mm aggregates, which were 6.25~11.44 kg/hm², 13.09~42.66, 14.38~51.03 g/hm², respectively. (5) The reserves of total nitrogen, ammonium nitrogen and nitrate nitrogen of the soil planted with Chuannong Huangyazao were higher than other cultivars. These research results provide a theoretical basis for the rational application of nitrogen fertilizer in tea-planting soils in the hilly areas of western Sichuan.

Abstract:To study the ecological recovery effect and soil physical and chemical factors affecting the species diversity of herb layer after land subsidence in mining area, we adopted the space-for-time substitution, selected the area of artificial recovery for 5a and 7a as the study sample sites and a sample site without artificial planting (C) as the control group. The plant species diversity index, and its correlation with soil physical and chemical factors within different recovery years were studied based on field plant community survey and soil sampling. The results showed that: (1) Compared with the control area, the number of Compositae and Amaranthaceae increased, and the number of Gramineae decreased. The number of species increased after 5 years, decreased after 7 years of artificial recovery, and the proportion of perennial herbs decreased gradually. Artificial recorvery improved the species richness of shrub layer. (2) After 7 years of artificial recovery, the species Shannon-Wiener diversity index of the herb layer increased significantly (P < 0.05). The dominant species changed from a single dominant species community dominated by Corispermum Stauntonii to a multi-dominant species community dominated by Dysphania aristata, Leymus racemosus, Astragalus Melilotoides and Setaria viridis. (3) Artificial vegetation recovery in coal mining subsidence area could improve SWC and soil TN, and the effect on soil TN was more significant (P < 0.05). Correlation analysis showed that SWC was the most important environmental factor affecting Shannon-Wiener, Simpson and Pielou index of herb layer, and TN also affected Shannon Wiener index. These findings indicates that the artificial vegetation recovery in coal mining subsidence area is of positive significance to improve SWC, TN, vegetation community structure and plant species diversity.

Abstract:Atmospheric nitrogen deposition can affect soil carbon and nitrogen dynamics by changing soil nitrogen availability (direct effect) and litter input (indirect effect). Soil aggregate is the most representative basic structural unit of forest topsoil, which is of great significance for the stable storage of organic carbon and nitrogen. The results showed that: (1) The contents of TOC (total organic carbon) and TN (total nitrogen) in layer A soil and aggregates with different particle sizes were significantly increased, and soil pH was significantly decreased by increasing (+L) and decreasing (-L) litter. Nitrogen addition significantly reduced the soil pH in layer B, which showed high nitrogen (HN) < low nitrogen (LN) < control (CK), and HN also significantly reduced the soil pH in layer A, and significantly increased the TOC content in layer B and aggregates. The addition of nitrogen and litter increase or decrease did not significantly affect the stability of soil aggregates. (2) Water stable macro aggregates (> 0.25 mm) was the dominant particle size in soil A and B, and the proportion of silt and clay (< 0.053 mm) was the lowest. The distribution of TOC and TN was the same in layer A and B. the contents of TOC and TN in > 2 mm aggregates were the highest, while those in 0.25 ~ 2 mm aggregates were the lowest. The contents of TOC and TN in layer A were higher than those in layer B. the contents of TOC and TN showed a V-shaped distribution with the decrease of soil aggregate size. (3) The stability of soil aggregates was positively correlated with the contents of TOC, TN, AN and AP, and negatively correlated with pH. The research results can provide reference for sustainable forest management.

Abstract:In order to clarify the impact of planting years on the soil carbon (C), nitrogen (N), phosphorus (P) and their ecological stoichiometry characteristics of jasmine garden, the 3-year (J-3), 10-year (J-10), 15-year (J-15), 30-year (J-30) and > 40-year (J-40) jasmine gardens in Fuzhou were taken as the research object, soil C, N, P and ecological stoichiometric ratios and their environment factors were determined and analyzed. The result showed: (1) Compared with J-3, the soil bulk density of J-10, J-30 and J-40 were decreased significantly by 29%, 19% and 18% (P < 0.05) respectively with the increase of planting years. The soil clay contents of J-15, J-30 and J-40 were significantly reduced by 26%, 12%, 30% and 12% (P < 0.05) respectively. (2) Compared with J-3, soil C and N contents of J-10, J-15, J-30 and J-40 were decreased by 82% and 236%, 73% and 199%, 149% and 488%, 201% and 481% (P < 0.05) respectively. Available nitrogen (AN) contents were reduced by 97%, 337%, 234% and 98% (P < 0.05). Compared with J-3, soil P and available phosphorus (AP) contents of J-15 and J-40 were increased significantly by 119% and 123%, 123% and 136% respectively (P < 0.05). (3) Soil C and N had a good fitting relationship (R² = 0.96, P < 0.01), which indicated that C and N was significantly correlation and both C and N were significantly and negatively correlated with C∶N (P < 0.01), which were significantly and positively correlated with C∶P and N∶P (P < 0.01). (4) Compared with J-3, soil C∶N of J-10, J-15, J-30, and J-40 were significantly increased by 85%, 72%, 136% and 93% (P < 0.05) respectively, while C∶P and N∶P were significantly reduced by 161% and 390%, 279% and 554%, 109% and 472%, 372% and 809% respectively (P < 0.05). (5) Soil bulk density, pH, and clay content were the main factors affecting soil C, N, P and other nutrient factors and ecological stoichiometry. Soil pH was increased, and bulk density, clay contents were decreased with the increment of jasmine planting years. The physical and chemical structures of the soil were improved. On the whole, soil C, N, P and their ecological stoichiometric characteristics, physical and chemical properties of the jasmine garden in Fuzhou will undergo certain changes with the increment of planting years. These changes would be inconducive to the planting of jasmine, so further optimized fertilization and soil improvement will be need for achieving sustainable production of jasmine.

Abstract:To investigate the effects of different base topdressing rates of nitrogen (N) fertilizer on the activity of key enzymes of N metabolism, N accumulation and transport, yield and N fertilizer utilization in drip irrigated spring wheat under N reduction mode, and to provide a scientific basis for the efficient production of drip irrigation spring wheat in Xinjiang wheat area, with medium gluten Xinchun 6 (XC 6) and strong gluten Xinchun 37 (XC 37) as materials, five nitrogen base topdressing ratios of 0∶0, 2∶8, 3∶7, 4∶6 and 5∶5 were set to study the effects of nitrogen base topdressing ratio on nitrogen metabolism and nitrogen use efficiency of spring wheat under drip irrigation. The results showed that, with increasing N fertilizer basal rate, nitrogen metabolism enzyme activity, nitrogen accumulation, nitrogen fertilizer utilization rate (NUE), seed yield and protein yield all tended to increase and then decrease, while pre-flowering nitrogen translocation rate, pre-flowering nitrogen contribution rate, and nitrogen fertilizer physiological utilization efficiency (NPE) showed the opposite trend, and the above parameters were higher in XC 37 than XC 6 at the same N fertilizer basal rate. The interact of variety and N fertilizer basal chase ratio showed that pre-flowering N translocation, post-flowering N accumulation, post-flowering N contribution, NUE, N fertilizer agronomic use efficiency (NAE), N fertilizer partial production (NPEP), N harvest index (NHI), seed yield, and protein yield were increased by 1.51%~34.93%, 10.62%~83.63%, 4.82%~25.38%, 8.00%~45.11%, 6.97%~19.84%, 2.00%~5.80%, 7.95%~40.38%, 1.44%~84.86%, 4.44%~98.04%, respectively, under 3∶7 treatment compared to the rest of the treatments. Correlation analysis showed that NUE was significantly and positively correlated with protein yield, seed yield, plant nitrogen accumulation, GS, and NR. Therefore, a 3∶7 ratio of nitrogen fertilizer base topdressing could improve plant nitrogen accumulation and promote seed yield, protein yield and nitrogen utilization based on the increase of nitrogen metabolizing enzyme activity.

Abstract:A field experiment was conducted to study the improvement effect of soil quality in sloping red cultivated land by contour reverse-slope terrace. The small watershed of Yizhe in Songhua Dam in Kunming northern suburb of central Yunnan was selected as a research area in this study, the 3-years (CRT 3), 7-years (CRT 7), 9-years (CRT 9) samples in contour reverse-slope terrace and unaltered sloping farmland (CK) were used as the research objects, combined with corn yield in various samples, the effects of implementing years on soil structure, fertility and enzymes activities were investigated. The results showed that the soil physical properties of sloping farmland were significantly improved by the growing land preparation years of the contour reverse-slope terrace. It appeared that the soil clay, silt, total aggregate and total porosity increased significantly, while the sand content and bulk density decreased significantly. It increased soil fertility, among which the concentrations of total nitrogen, total phosphorus, total potassium, available phosphorus, available potassium and water content were significantly increased, and among which urease, amylase, sucrase, phosphatase, protease and catalase activities were increased by 24.25% ~ 117.43%, 20.90% ~ 82.82%, 17.09% ~ 99.69%, 30.15% ~ 82.63%, 32.21% ~ 66.50% and 11.67% ~ 41.39%, respectively. At the same time, corn yield was significantly increased, and CRT 9 had the most obvious effect, which increased by 22.47%. Land preparation measures of contour reverse-slope terrace could improve the soil environment of sloping farmland, and with the increases of land preparation years, soil quality would be better improved, effectively reduced land degradation.

Abstract:Pinus massoniana is the pioneer tree species in the red soil regions of southern China, however, its growth is impaired by the poor soil fertility. This study examined the effects of compound fertilizer, microbial fertilizer and super absorbent polymer (SAP) on the growth characteristics, biomass, plant nutrient content, and fertilizer uptake efficiency (FUE) of 1-year-old Pinus massoniana seedlings. A control (no fertilizer, CK) and three fertilization treatments, namely single application of compound fertilizer (0.94, 1.89, 3.56 g); mixed application of compound fertilizer and microbial fertilizer ((0.94+8.00), (1.89+8.00), (3.56+8.00) g); and mixed application of compound fertilizer and SAP ((0.94+1.01), (1.89+1.01), (3.56+1.01) g), were applied over 2 years. The results showed that: (1) Compared to the control, different fertilization treatments significantly increased the ground diameter and plant height growth of seedlings. The highest growth of seedling ground diameter and plant height were both F2B (mixed application of compound fertilizer and SAP, (1.89 + 1.01) g) treatments, which was significantly higher than other treatments. (2) Under the mixed application of compound fertilizer and microbial fertilizer, root biomass accounted for a larger proportion of the whole biomass. Meanwhile, under the mixed application of compound fertilizer and SAP, the whole biomass of the seedlings was higher. (3) Fertilization significantly increased the TN, TP, TK contents of leaves, stems, and roots of the seedlings. The TP content of seedlings had the greatest impact on its growth characteristics and is extremely significantly correlated, which explains 58.03% of the changes in seedling growth characteristics (P < 0.01). (4) Principal component analysis indicated that the F2B ((1.89+1.01) g) was the optimum fertilization amount and method in this experiment. Comprehensive analysis of growth characteristics and FUE of the seedlings showed that the F2B ((1.89+1.01) g) might serve as a highly effective fertilization method for Pinus massoniana growing in the severely eroded and degraded red soils of southern China. These results provide a theoretical basis for the fertilization management of Pinus massoniana forests with severely eroded and degraded red soils.

Abstract:Taking the typical shelter forest in Hobq Desert as the object, the physical and chemical properties of soil in different forests were measured to evaluate the soil improvement benefits of the shelter forest system and provide theoretical support for the management and maintenance of shelter forest in Hobq Desert. The results showed that: (1) 15 years after the establishment of the Hobq Desert Shelter Forest, the original quicksand texture had changed significantly due to the effect of vegetation improvement. Compared with the quicksand environment, the contents of soil AN, AP, AK, SOM, TN, TP and TK increased by 243.95%, 37.89%, 108.84%, 138.71%, 118.77%, 42.41% and 45.77%, respectively. Compared with other types of vegetation, the contents of SOM, AK and TN in Elaeagnus angustifolia shelter forest increased the most, with the increase of 188.36%, 151.84% and 158.67%, respectively. The AN content in Pinus sylvestris var. mongolica shelterbelt had the largest increase, with an increase of 481.86%. The physical properties of soil showed different rules with the increasing of soil layers. Compared with the quicksand environment, soil water content (SWC) and porosity (PV) changed significantly. (2) The variation ranges of C/N, C/P and N/P in this area were 7.46~27.22, 2.11~14.17 and 0.07~0.62, respectively. Vegetation type, soil depth and the interaction between them significantly affected soil quality, and vegetation restoration process in this study area was mainly limited by nitrogen content. (3)The redundancy analysis showed that the SWC and PV had significant correlation with the soil nutrients and stoichiometric characteristics of the shelter forest, and they were also the main environmental factors that affected the soil nutrients and stoichiometric features of the Hobq Desert Shelterbelt. These results could provide data support for evaluating the soil improvement benefits of the Shelter Forest System in Hobq Desert.

Abstract:A pot experiment was conducted to compare the remediation effects of different soil amendments derived from crawfish shell on an arsenic (As) and lead (Pb) contaminated soil. Soil amendments, including crawfish shell powder (CSP), chitin (CT), crawfish shell biochar (CSB) and CT-CSB combination (CT-CSB, CT∶CSB is 1∶1), were employed to assess the influence of their applications (1%) on the availability of nutrients, activities of enzymes, bioavailability of As and Pb, as well as growth of pak choi (Brassica chinensis). The results indicated that all treatments significantly increased the pH and cation exchange capacity (CEC) of the soil. Concentrations of available Pb decreased in all treatments, and the maximum reduction was found in the CSB treatment, which was 35.3% lower than control. Application of CT, CSB and CT-CSB decreased the concentrations of available As, and the maximum reduction was found in the CT-CSB treatment, which was 77.2% lower than control. The activities of soil enzymes including α-glucosidase, cellobiohydrolase, xylosidase, acetyl glucosaminidase and acid phosphatase were enhanced after the addition of CT, CSB and CT-CSB. Correlations analysis between soil enzyme activity and the concentrations of available Pb and As indicated that the application of different amendments could alleviate the stress of As and Pb in the soil, and thus enhance soil enzyme activities. Application of all amendments decreased the uptake of As and Pb in the edible part of pak choi, and increased the phytoavailability of nitrogen, phosphorus and potassium, thus promoting plant growth. The biomass of the edible part of pak choi increased by 190.9% in the CT-CSB treatment, compared with the control. In conclusion, application of CT, CSB and CT-CSB, in particular CSB, had superior potential for promoting plant growth and remediating soil polluted by As and Pb, offering a new approach for the in-situ remediation of soil co-contaminated with As and Pb.

Abstract:In order to explore the effects of combined application of straw and nitrogen fertilizer on microbial activity and soil aggregates in sandy fluvo aquic soil, the effects of the different amounts of nitrogen fertilizer and combined application ratios of straw on organic matter, soil microbial biomass carbon, nitrogen content, soil enzyme activity and soil aggregate in sandy fluvo aquic soil were studied by using the method of indoor culture and controlling urea amounts under the condition of quantitative straw. The results showed that compared with CK, straw combined with proper amount of nitrogen fertilizer could significantly improve soil organic matter content (29.04%~41.90%), microbial biomass carbon content (53.34%~90.33%), nitrogen content (25.41%~38.67%), soil urease activity (35.29%~44.12%), polyphenol oxidase activity (36.67%~53.33%) and the proportion of large aggregates (> 0.25 mm)(8.81%~65.22%), and enhance the stability of aggregates (25.89%~91.96%)(P < 0.05). When the amount of urea was 0.213 g/kg, it was most conducive to increase soil microbial carbon content, the proportion of large particle aggregates (> 0.25 mm) and improve the stability of aggregates. When the amount of urea was 0.086 g/kg, the soil organic carbon and soil microbial nitrogen contents were significantly affected. Correlation analysis showed that soil organic carbon, microbial biomass carbon, nitrogen content enzyme activities were closely related to WMD and GMD, showing a positive correlation. In conclusion, straw returning combined with nitrogen fertilizer could improve soil nutrient content and soil physical properties in sandy fluvo aquic soil. The research results could provide a theoretical basis for optimizing straw returning technology and improving the fertility of sandy fluvo aquic soil.

Abstract:In order to study the effects of different doses of sweet potato vine and their biochar returning to the field on microbial activity and nutrient contents of dryland red soil, field positioning experiment was conducted. In the experiment, five treatments were set up, which were conventional management (CK), 3 000 kg/hm² sweet potato vine returning (S1), 6 000 kg/hm² sweet potato vine returning (S2), 1 000 kg/hm² sweet potato vine biochar returning (BC1) and 2 000 kg/hm² sweet potato vine biochar returning (BC2). The results showed that compared with CK, in the 0—10 cm soil layer, soil basal respiration of BC1 increased by 17.93%, while that of S1, S2 and BC2 decreased by 20.33%, 10.10% and 2.66%, respectively. In the 10—20 cm soil layer, the soil basal respiration of S2 and BC1 increased by 17.29% and 0.41%, respectively, while that of S1 and BC2 decreased by 13.61% and 16.93%, respectively. In the 20—30 cm soil layer, the basal respiration of S1, S2, BC1 and BC2 increased by 8.26%, 48.94%, 50.21% and 38.59%, respectively. Compared with CK, the soil microbial biomass carbon of S1, S2, BC1 and BC2 treatment increased about 1.30%, 6.09%, 28.52% and 39.64% in the 0—10 cm soil layer, respectively. In the 10—20 cm soil layer, soil microbial biomass carbon of S1, S2, BC1 and BC2 increased by 9.76%, 16.72%, 24.20% and 54.32%, respectively. In the 20—30 cm soil layer, soil microbial biomass carbon of S1, S2, BC1 and BC2 increased by 22.34%, 39.27%, 54.06% and 84.09%, respectively. It showed that sweet potato vines and their biochar could promote the soil basal respiration and soil microbial biomass carbon content to a certain extent. Sweet potato vine returning promoted the activities of soil FDA hydrolase and soil urease, but had little effect on soil sucrase activity. Returning biochar to the field inhibited the activities of soil FDA hydrolase and soil urease, and promoted soil sucrase activity. Sweet potato vine returning increased the content of soil organic carbon, while biochar returning reduced that. Sweet potato vine and biochar returning both increased the contents of hydrolyzed nitrogen and available phosphorus in the soil. The results showed that the addition of sweet pototo vine and biochar could effectively improve the soil physical and chemical properties and soil microbial activity, which was of great significance to improve the stability of soil ecosystem. The results provided a theoretical basis for the rational return of straw and biomass carbon to the field.

Abstract:In order to explore the direct and indirect effects of biochar on plant growth under water shortage condition, the growth indicators of ryegrass (Lolium perenne L.) and the physical and chemical properties of the soil were observed by controlling different addition of biochar and precipitation. The results showed that the addition of biochar could increase the field water holding capacity of the soil, the content of available phosphorus and soil pH. Under drought conditions, increasing the amount of biochar increased the height of ryegrass plants, but high-dose of biochars inhibited the growth of ryegrass. The addition of biochar could not maintain soil moisture, high concentration (> 15%) of biochar even increased the loss of soil moisture, but because of the potassium in biochar, it could provide the necessary nutrient for ryegrass to fight against the drought condition. Our results showed that appropriate addition of biochar (5%) could alleviate the inhibition of the growth and development of ryegrass in the absence of water, and promote their root growth and ensure a higher germination rate. In a word, the addition of biochar to the soil could promote plant growth under drought conditions and help alleviate the effects of drought stress on plants.

Abstract:Soil surface electrochemical characteristics are important basis for soil fertility. Studies on the effect of wheat straw and its biochar addition on the soil surface electrochemical properties can provide important theoretical and practical basis for improving the quality of cultivated land, sustainable utilization and reducing soil erosion. Through indoor constant temperature culture experiment, 11 treatments were set up: control (CK), 1% straw (J1), 3% straw (J3), 5% straw (J5), 7% straw (J7), 10% straw (J10), 1% biochar (S1), 3% biochar (S3), 5% biochar (S5), 7% biochar (S7), 10% biochar (S10). Soil samples were collected after 10 months, then determined for surface electrochemical parameters by the method of combined analysis of surface properties, including surface charge number (SCN), specific surface area (SSA) and surface charge density(σ₀), surface potential (φ₀), and surface electric field intensity (E₀). The relationships between surface electrochemical properties and soil physical and chemical properties were analyzed by redundancy analysis. The results showed that: (1) After applying straw and biochar, soil carbonate content decreased, while soil organic carbon (SOC), electrical conductivity, total nitrogen (TN) and carbon nitrogen ratio (C/N) increased. The addition of straw could reduce the pH of loessal soil, while increase the pH. (2) With the increase of straw application rates, Zeta potential decreased. After applying biochar, Zeta potential of each treatment was lower than that of CK, but Zeta potential increased with the increase of biochar application rates in general. (3) The SSA and SCN of soils increased with the increase of straw and biochar application rates. Compared with CK, the SSA of J10 and S10 increased by 114.0% and 98.1%; and SCN of J10 and S10 increased by 80.8% and 88.3%, respectively. Application of straw could reduce the surface charge density of soils. The σ₀ for straw-added soils was reduced by 5.5%~15.5% compared with that in CK. A small amount of biochar application could increase soil σ₀ compared with that in CK. On the whole, the σ₀ decreased with the increase of biochar application rates. When the amount of biochar was more than 5%, σ₀ for biochar-added soils was less than CK. (4) The results of redundancy analysis showed that SOC was the most important factor affecting the soil surface electrochemical properties and the explained amounts were 88.1% and 89.5% for straw and biochar addition, respectively. The application of straw and biochar could significantly increase the content of organic carbon and improve the basic physical and chemical properties of the Loessal soil. The SSA and SCN of soils increased while the surface charge density decreased with the increase of straw and biochar application rates. The content of organic carbon was the main controlling factor of the surface electrochemical properties.

Abstract:To evaluate the effects of single and combined application of biochar and humus on CH₄ and N₂O emission in paddy field and rice yield, taking the paddy field system of gleyic paddy soil in Lin'an, Zhejiang Province as the research object, two addition levels of rice straw biochar (0 and 20 t/hm²) and three addition levels of humus (0, 0.6 and 1.2 t/hm²) were set in the experiment, and a total of six treatments were carried out, which were B0F0 (control, without biochar or humus), B0F1 (humus dosage of 0.6 t/hm²), B0F2 (humus dosage of 1.2 t/hm²), B1F0 (biochar dosage of 20 t/hm²), B1F1 (the amounts of biochar and humus were 20 t/hm² and 0.6 t/hm², respectively), B1F2 (the amounts of biochar and humus were 20 t/hm² and 1.2 t/hm², respectively). Effects of biochar and humus addition on rice yield, CH₄ and N₂O emissions in rice fields were studied. The results showed that: (1) Compared with B0F0, application of biochar and humus alone or combination all reduced cumulative CH₄ emission and increased cumulative emission of N₂O in soil. (2) Biochar treatment had no significant effect on GWP (global warming potential) and GHGI (greenhouse gas intensity) (P>0.05). Humus treatment significantly decreased GWP and GHGI (P < 0.05). Biochar and humus had significant interaction on GWP and GHGI (P < 0.05). (3) Compared with B0F0, the application of biochar and humus alone or the combined application could reduce greenhouse gas emission intensity (GHGI) per unit rice yield to a certain extent. The GHGI of B0F2 treatment was the lowest, indicating that the application of humus alone (the amount of humus was 1.2 t/hm²) had the best emission reduction effect and environmental effect. The results could provide data support and theoretical basis for further discussion on carbon sequestration and emission reduction in paddy soil.

Abstract:This paper studied the effects of different artificial vegetation communities and soil improvement on the characteristics of heavy metal loss in the runoff of lead-zinc mine wasteland, in order to provide early restoration ideas for the ecological restoration of mining wasteland. The runoff plot experiment was used to improve the soil by adding organic fertilizer and calcium fertilizer. Under the condition of natural rainfall, different artificial vegetation communities (grass, shrub grass and tree shrub grass) were constructed on the undisturbed soil and improved soil of lead-zinc mine wasteland respectively. The production of surface runoff, the content and loss of sediment, cadmium, lead and arsenic in runoff were analyzed and studied. The results showed that: (1) In undisturbed soil, the cumulative runoff decreased by 11.3% and 0.8% respectively compared to grass communities and irrigated grass communities. Compared with undisturbed soil, the cumulative runoff of improved soil decreased by 3.2%~18.8% in the same artificial vegetation community. In undisturbed soil, the accumulated sediment of shrub grass community decreased by 28.9% and 14.0% respectively compared with grass community and tree shrub grass community. Compared with undisturbed soil, the cumulative sediment of improved soil decreased by 40.0%~63.3% in the same artificial vegetation community. (2) In undisturbed soil, the cumulative losses of dissolved cadmium, lead and arsenic in different artificial vegetation communities were 2.7~7.2, 104.3~295.1 and 1.4~5.4 mg / m² respectively. Compared with the undisturbed soil, the cumulative losses of dissolved cadmium, lead and arsenic in different artificial vegetation communities decreased by 47.7%~61.0%, 43.8%~64.6% and 43.8%~63.8% respectively. (3) In undisturbed soil, the cumulative losses of particulate cadmium, lead and arsenic in different artificial vegetation communities were 2.5~9.0 g/m², 437.5~1 347.2 and 16.2~89.9 mg/m² respectively. Compared with the undisturbed soil, the cumulative loss of particulate cadmium, lead and arsenic in different artificial vegetation communities decreased by 53.7%~72.0%, 55.4%~65.8% and 60.2%~71.1% respectively. (4) The losses of particulate cadmium, lead and arsenic accounted for 99.8%~99.9%, 77.1%~84.1% and 85.1%~96.7% of the total loss respectively. In conclusion, the more complex the artificial vegetation community, the lower the runoff, sediment and heavy metal loss. Adding soil amendment could further strengthen the interception function of vegetation community. Under different plant communities, the loss of particulate heavy metals dominated.