Abstract:The fingerprinting technology is an effective method to quantify sediment sources in watershed. How to apply it to burned areas is still worth discussing. Based on the review of relevant literature, the mechanisms of forest fire aggravating soil erosion through vegetation, soil and ash was summarized. This paper introduced the case of applying fingerprinting technology to study the source of sediment in the fire basin. The content and property variations of fingerprint factors such as fallout radionuclides, mineral magnetics, physical indexes, geochemical elements and organic compounds in the burned area were analyzed emphatically. The applicability of various fingerprinting tracers in the study of sediment sources in burned areas was discussed. Additionally, some key investigation directions were provided, including the physical basis of fingerprinting technique, the spatio-temporal variation of burned soil properties, the stability verification of fingerprint tracers, the impact of burning ash, and the identification of large sediment particles. This review paper could provide a theoretical basis for promoting the research of the fingerprinting technique in burned areas, understanding the impact of forest fire on sediment yield patterns, and improving the effectiveness of water and soil conservation and ecological restoration in burned watershed.

Abstract:Vegetation has good function of soil and water conservation. Careful understanding the relationship between the structural characteristics of vegetation and the production of runoff is the basis for studying the erosion control function of vegetation. In this paper, the effects of five vegetation structures (shrubs, herbs, litter, shrubs + herbs, shrubs + herbs + litter) and erosive rainfall (60, 90, 120 mm/h) on the process of erosion were investigated by artificial simulated rainfall experiments with typical forest vegetation in Central Hubei. The results showed that: (1) The runoff and sediment yield increased rapidly at first, then increased slowly with the rainfall time, and finally reach a stable trend. Rainfall intensity was the dominant factor of slope erosion and sand production, and showed a significant positive correlation with flow production time, flow production rate and sand production rate (p < 0.01). (2) With or without litter, vegetation coverage and plant density were the main factors affecting runoff and sediment yield on the slope. The sediment concentration of runoff under different covering structures was as follows: herb > shrub > litter > herb+shrub > shrub and grass withered. (3) The priority of structural characteristic parameters on runoff and sediment yield was: coverage, biomass, plant density, diversity index, that was, horizontal structure > vertical structure > species composition > spatial pattern. The results of the study aim to reveal the mechanism of the role of vegetation structure on slope erosion, and provide scientific reference for the construction of soil erosion models in southern woodlands.

Abstract:“Grain for Green” Project is one of the main measures to control soil and water loss on the Loess Plateau. Discussing the impact of returning farmlands to forests on the stability of soil aggregates and soil erodibility could provide a scientific basis for ecological restoration and benefit evaluation of soil and water conservation on the Loess Plateau. In this study, the Robinia pseudoacacia L. forests with different planting years (5 years, 10 years, 15 years, 20 years, 25 years and 30 years) were selected as the research object, and the farmland was used as the control to study the dynamic changes of soil aggregate stability and soil erodibility in 0-30 cm soil layers after returning farmlands to forests, and the study also explored the relationship between soil erodibility and soil aggregate stability. The results showed that: (1) The content, mean weight diameter and geometric mean diameter (GMD) of water-stable aggregates＞0.25 mm increased with the increasing of planting years, which increased by 32%~79%, 32%~98% and 2%~60%, respectively, compared with that of farmland. (2) The fractal dimension of soil aggregates decreased with the increasing of restoration ages, which decreased by 0.6%~6.0% compared with that of before returning farmland. Soil organic matter increased with the increasing of restoration ages, increased by 8.4%~38.9% compared with that of farmlands. (3) Soil erodibility factor K increased with the increasing of soil layer, but decreased gradually with the increasing of restoration ages, and decreased by 1.0%, 2.7%, 3.6%, 3.9%, 5.0% and 7.9%,respectively, with the increasing of restoration ages. (4) After the conversion of farmland to forest, the fractal dimension of soil aggregates and the content of water-stable aggregates＞0.25 mm were the main driving factors for the change of soil erodibility. The aboveground biomass indirectly affected soil erodibility through affecting the fractal dimension of soil aggregates and the content of water-stable aggregates＞0.25 mm, and the total effect was the largest. The study suggested that the increase of soil aboveground biomass after returning farmlands to forests played an important role in the formation and stability of soil aggregates and the reduction of soil erodibility, and returning farmlands to forests significantly improved the stability of aggregates and reduced soil erodibility.

Abstract:The study aims to establish a soil loss prediction model in spoil heaps of production and construction projects for different regions in our country. A series of indoors artificial simulated rainfall tests were carried out on the spoil heaps with different soil texture, slope length and gravel content. The soil loss prediction model of spoil heaps was established in the framework of Universal Soil Loss Equation (USLE), and the factor parameters were revised. The study clarified the definition of the standard plot of the engineering spoil heaps and the methods to calculate each factor and proposes to use the soil-rock factor to replace the traditionally used erodibility factor, as to be more consistent with the actual situation. The results showed that the power function is used to calculate the spoil heaps slope degree and slope length factor, and the soil and rock factor is calculated by the exponential function combined with the gravel mass fraction, which can effectively predict the rainfall events erosion of the spoil heaps. The calculation method of the model was to multiply rainfall erosivity, slope degree, slope length and soil and rock factor. The calibration and verification showed the model prediction effect is good, which can be applied to different soil types of engineering spoil heaps. The parameters of each factor of the model were easy to obtain and had physical meaning, and the field operability and practicability were strong. Results provide technical guidance and scientific basis for the soil and water conservation work of production and construction projects and the supervision and law enforcement of water administrative departments, and have great scientific significance and production application and guiding value.

Abstract:In order to analyze the origin of water and sediment in the Yellow River and predict the future water and sediment situation, two typical watersheds (Xinshui River and Zhujiachuan watershed) in the middle reaches of the Yellow River were selected as the study area. Based on the measured data of water and sediment from 1956 to 2018 at the hydrological station and rainfall station, the Mann-Kendall trend, the change-point analysis, the cumulative anomaly method and the Morlet wavelet method were used to analyze the variation trend of water and sediment in typical watersheds. Furthermore, the attribution of water and sediment changes were analyzed by using the double mass curve method, and the relative contributions of climate change and human activities to water and sediment change were quantified. The results showed that from 1956 to 2018, the average annual runoff in the Xinshui River and Zhujiachuan watershed was 11.9×10⁷ and 1.7×10⁷ m³, respectively, and the average annual sediment discharge was 12.3×10⁶ and 9.8×10⁶ t, respectively. The runoff and sediment discharge showed a significant decreasing trend. The abrupt change year of runoff in the Xinshui River and Zhujiachuan watershed was 1980 and 1984, respectively, and the abrupt change year of sediment discharge was 1980 and 1972, respectively. The changes of water and sediment in the watersheds had obvious periodicity, and the first main cycle of runoff change was 45 years and 16 years, and the first main cycle of sediment transport change was 9 years and 15 years, respectively. The contribution rate of rainfall to the reduction of runoff in Xinshui River and Zhujiachuan watershed was 19% and 8%, respectively, and the contribution rate of rainfall to the reduction of sediment discharge was 25% and 35%, respectively. The Contvibution rate of rainfall is far lower than that of human activities, which are the leading factor of the sharp decrease of runoff and sediment discharge. The research results can provide scientific suggestions for water and sediment control of the Yellow River.

Abstract:In order to reduce soil erosion during the period from sowing to emergence of crops in sloping farmland, the effects of microtopography formed by different sowing patterns on soil and water erosion were studied by simulating rainfall. A total of six treatments were set up, among which T1 treatment was deep ditching sowing (20 cm deep), T2 treatment was shallow ditching sowing (10 cm deep), T3 treatment was pond sowing, T4 treatment was high ridge sowing (20 cm high, 30 cm wide), T5 treatment was low ridge sowing (10 cm high, 15 cm wide) and T6 treatment was flat sowing (blank control). 27 simulated rainfall experiments were carried out under 40 mm/h, 80 mm/h and 120 mm/h rainfall intensities on 10°, 15°and 20° slopes for each treatment. The results showed that both ditching and ridging sowing treatments could effectively reduce soil and water erosion. The soil and water conservation effects of each treatment followed the order of T1＞T4＞T2＞T5, and there was no significant difference between T3 and T6. Among them, the soil and water conservation effect of T1 treatment was the best. Under each slope and rainfall intensity, compared with T6 treatment, the time of surface runoff generation was delayed by 65.9%~178.1%, the infiltration rate increased by 102.6%~195.1%, the surface runoff and the soil erosion reduced by 75.6%~82.6% and 95.3%~99.1%, respectively, in T1 treatment. T1 and T4 could well retain rainwater in ditch or ridge, and could effectively prevent water from crossing ridge or flowing out of ditch. Among them, T1 treatment had the best effect in preventing water from flowing out of the ditch, which only occurred in rare cases. The study on the influence of microtopography formed by different sowing patterns on soil and water loss was of reference significance for soil and water conservation in the early stage of crop growth in sloping farmland.

Abstract:As one of the important surface coverings in arid and semi-arid regions, biocrusts can promote the restoration and stability of ecosystems by stabilizing soil surface to resist soil erosion and degradation. However, the specific mechanism of this process needs to be further studied. In order to investigate how biocrusts improve soil physical properties and thus water and soil conservation, we measured the soil pore characteristics and penetration resistance of biocrusts and bare soil using high-resolution X-Ray computed tomography (CT) scanner and high-precision soil penetrator in the Loess Plateau. In addition, structural equation model (SEM) was established to analyze the effect pathway of biocrusts on soil porosity and penetration resistance. The results showed that moss-dominated biocrusts changed soil pore characteristic parameter, and significantly increased the total soil porosity of 0-2 cm layer (p＝0.01). Compared with bare soil, the total soil porosity of moss-dominated biocrusts on aeolian sand and loess soil increased by 1.62 and 2.12 times, respectively. Moreover, the porosity of moss-dominated biocrusts decreased exponentially with the increase of soil depth. The plane porosity of moss-dominated biocrusts was significantly higher than that of bare soil (p＜0.001), both of them decreased sharply within 0-1 cm. The penetration resistance of moss crusts improved with the increase of soil depth, but obvious mutation of penetration resistance was found in the middle of crust horizon, while it basically stabilized in the subcrusts layer. On both aeolian sand and loess soil, the plane porosity and penetration resistance of moss crusts were log negatively correlated, and they were linearly positively and log negatively correlated in bare soil, respectively. The effect of biocrusts on soil penetration resistance was mainly realized through indirect ways such as particle composition and porosity. In Loess Plateau, moss crusts significantly increase the penetration resistance of topsoil through indirect means such as changing porosity and particle composition, which was conducive to improving soil surface stability and providing strong conditions for regional soil and water conservation and ecological restoration.

Abstract:Special features resembling internal hollows (niches-like ephemeral gully head) are common in the collapsing walls of granite Benggang erosion in southern China. This study investigated the material conditions and drivers of niches occurrence by describing the morphological evolution of the niches, and combined with moment analysis methods to construct mechanical models to evaluate the stability of collapsing walls and niches. Studies have shown that niches morphology evolves through three stages of "embryonic-development-formation". Soil heterogeneity in the profile is the underlying condition for niche development, with hydrodynamics and gravity acting together as external factors to drive niche development. The stability of the niche decreases as its height increases and its angle decreases. The development of niches may be a sign of the initiation of headcut erosion of the Benggang, and the containment of niche formation is conducive to improving the stability of the collapsing wall. The results of the study provide a theoretical basis for Benggang erosion management.

Abstract:In order to compare the hydraulic characteristics of sheet flow and rill flow on saturated purple soil slope and clarify their critical hydraulic characteristics, indoor artificial simulated rainfall experiments were conducted under the combined conditions of five slope gradients (SGs: 2°, 5°, 10°, 15°, 20°) and three rainfall intensities (RIs: 30, 60, 90 mm/h). On the basis of measuring the velocity of sheet flow, rill flow and critical velocity of shee flow transform to rill flow, the corresponding hydraulic parameters were calculated, including water depth, Reynolds number, Froude number and Darcy resistance coefficient. The results showed that: In different erosion stages, the velocity of sheet flow was between 0.064 and 0.151 m/s and rill flow was between 0.175 and 0.350 m/s. The influence degree of SGs and RIs on velocity and water depth of sheet and rill flow was different. The sheet flow was all laminar and was tranquil when the slope gradient was < 10°. The sheet flow was mostly in the state of tranquil laminar flow. The rill flow was transitional under the conditions of moderate and heavy rain and was rapid when the slope gradient was > 5°. The rill flow was mostly in the state of rapid transitional flow. The Darcy resistance coefficient of sheet flow was negatively correlated with SGs and RIs, while that of rill flow was positively. The critical velocity of sheet flow transform to rill flow was between 0.100 and 0.165 m/s. The velocity would change the slope shape, resulting in the difference of the critical flow pattern and flow resistance with SGs and RIs. This study is of great significance to understand the hydraulic characteristics of sheet flow and rill flow on saturated soil slope, and to further clarify the critical hydraulic conditions for the sheet flow to rill flow transition.

Abstract:In order to explore the characteristics of slope surface microtopography(SSM) change of slope farmland under different artificial management measures, and clarify the response of SSM change to seepage, so as to provide a scientific basis for the effective prevention and control of soil erosion and the reasonable layout of artificial management measures, this study took the flat slope (CK), artificial digging slope (AD) and ridge tillage slope (RT) as the research object. Based on simulated seepage experiment, the variation characteristics of SSM on 5° and 15° purple soil slopes were studied. The results showed that (1) The semivariogram of SSM on the three slopes showed a central symmetric distribution in the directions of 0~135° and 180°~315° before and after the seepage test, and the distribution range gradually decreased with the increasing of slope gradients and exhibited obvious directivity. Under seepage condition, the variation trend of SSM anisotropy on CK and AD was relatively consistent, while the spatial variability of SSM on RT was strong. (2) Under seepage condition, the range of elevation variation on the three kinds of slopes was mainly concentrated in -20 mm to 0 mm, and the distribution of slope elevation of relative rough slopes (AD and RT) was more dispersal compared with CK. (3) Compared with 5° slope, the response of soil surface roughness (SSR) change to seepage was more obvious on 15° flat slope. The change rate of SSR followed the order of CK>AD>RT. Under seepage condition, the SSR varied greatly at the midslope and downslope. The more intense the initial fluctuation of slope surface was, the more obvious the abrupt change response of SSM to seepage erosion. In this study, soil surface roughness could be used as an indicator for describing the response of SSM changes to seepage condition, which could efficiently characterize the spatial distribution of soil erosion-deposition at the middle and downslope, so as to provide a theoretical basis for clarifying the coupling relationship between the variation of SSM and seepage erosion on purple soil slope.

Abstract:In order to explore effect of the enclosure of shrub grassland on soil preferential flow, typical desert area in Ningxia province, Wuzhong city was taken as the study area, field infiltration dyeing test and image processing analysis were used. The results showed that: (1) In the fenced and enclosed plots, the infiltration staining images showed obvious difference. In the fenced and enclosed plots, grassland, natural Caragana korshinskii forest and artificial C. korshinskii forest showed uniform distribution at 0-125, 0-115 and 0-105 cm, respectively, and branching at 125-240, 115-150 and 105-140 cm. While in the grazing management plots, the infiltration staining images of grassland, natural C. korshinskii forest and artificial C. korshinskii forest showed uniform distribution in 0-80, 0-70 and 0-80 cm, respectively. The depth of soil preferential flow was deepened due to fencing. (2) The area ratio of soil profile staining was as follows: fenced grassland > fenced natural C. korshinskii forest > fenced artificial C. korshinskii forest > grazing management artificial C. korshinskii forest > grazing management natural C. korshinskii forest > grazing management grassland. The depth of soil staining was as follows: fenced grassland > fenced natural C. korshinskii forest > grazing managed grassland > grazing managed natural C. korshinskii forest > fenced artificial C. korshinskii forest > grazing managed artificial C. korshinskii forest. Fenced management would lead to the increase of soil profile staining area ratio and depth. (3) Soil preferential flow variation coefficient of performance was as follows: grazing management natural C. korshinskii woodland > grazing management artificial C. korshinskii > enclosure cultivating natural C. korshinskii woodland > grazing management grassland > grazing management cultivating artificial C. korshinskii forest land > enclosures fence grassland. Grazing management will lead to increment of soil preferential flow. Cultivating and enclosures will reduce the degree of preferential flow shrub forest and grass. Therefore, in arid and semi-arid areas such as desert steppe, fencing can be an important management method to improve the uniform infiltration depth of soil water, reduce the occurrence of preferential flow, and improve the efficiency of soil water use.

Abstract:In order to explore the characteristics and mechanism of soil water erosion driven by biological crust development, five coverage grades (1%~20%, 20%~40%, 40%~60%, 60%~80%, 80%~100%) were designed for the abandoned farmland plots with moss development as the dominant species in Wulongchi small watershed in Danjiangkou Reservoir area, and the bare soil was used as the control to collect samples. Soil detachment text was studied under different flow shear forces (6.12~19.64 Pa). The results showed that: The development of biocrusts significantly affected soil nutrient content, and nutrient surface aggregation was more obvious under the high coverage of crust; The development of biocrusts significantly affected the soil detachment capacity. The soil detachment capacity of bare soil was 3.58~348.95 times that of biological crust . The rill erodibility of bare soil (0.293 5 s/m) was 3.57~293.50 times that of biological crust (0.001 0~0.082 2 s/m). The relative soil detachment ability and rill erodibility decreased exponentially with the increase of crust coverage, and the crust breaking time increased exponentially with the increase of crust coverage. Nonlinear regression analysis showed that the soil detachment ability could be simulated by water flow shear force, biological crust coverage and soil bonding force (NSE=0.749). In conclusion, the development of biocrusts significantly improved soil erosion resistance. The results can provide scientific basis and theoretical reference for soil and water loss control and biocrusts management and utilization in subhumid area.

Abstract:To reveal the distribution pattern of soil particle composition in vertical and horizontal directions, soils from 0-100 cm layer profiles of typical slopes in the Pisha sandstone area were collected and their particle composition was determined by using classical statistics. Results showed that the soil texture of 0-100 cm layer on the slope was mainly sandy loam (59.21%) and loamy sandy soil (36.40%). With the increase of soil depth, the content of sand increased, the content of silt and clay decreased, and the soil gradually showed a trend of coarse graining. On the slope scale, the sand content in the soil surface layer of 0-10 cm were weakly variable, and the variability of all grain classes in the remaining layers was moderate, and the variability increased with depth, and the coefficients of variation of different grain classes showed that sand < silt < clay. Along the slope contour direction, the coarseness of sample zone B was the weakest, and below the 10 cm layer, the coarseness of sample zone B was the strongest. Along the vertical slope contour direction, the content of sand (73.60%) increased by 6.90% (p<0.05) and 11.66% (p<0.05) in the middle of the slope compared with the top and bottom of the slope, respectively, while the content of silt (31.85%) and clay (3.10%) increased by 13.13% (p<0.05), 23.59% (p<0.05) and 4.36%, 51.70% (p<0.05) in the bottom of the slope compared with the top and middle of the slope. The coarse granulation was the strongest in the middle of the slope, and the bottom of the slope was the main area for the accumulation of fine particles. The results of the study can strengthen the understanding of the spatial distribution pattern of soil particles on the slope of Pisha sandstone area.

Abstract:Water conservation is one of the most important service functions of the ecosystem, and the outline of the Yellow River Basin Ecological Protection and High-quality Development Plan emphasizes focusing on key areas and restoring important ecosystems, which puts forward new requirements for strengthening water conservation capacity. We collected and analyzed meteorological and subsurface data of the Yiluo River basin from 1975 to 2019, calculated the water yield of the basin for a total of nine time periods in every five-year period during 1975 to 2019 using the water yield module of the InVEST model, and the water conservation was obtained by using the flow rate coefficient and soil saturation conductivity to correct the water yield. This study specifically analyzed the characteristics and correlations between precipitation, water yield and water conservation in the Yiluo River Basin.The results show that from 1975 to 2019, the annual average water conservation in the Yiluo River Basin is 11.3 mm, and the annual average water yield is 143.2 mm, and the overall water yield and water conservation show a trend of first increasing and then decreasing, reaching a peak from 1980 to 1984. The spatial distribution of water conservation capacity in the river basin is characterized by abundant vegetation in the upstream and strong water conservation capacity in mountainous areas of earth and rock, while the middle and lower reaches are relatively weak. The results of single-correlation and complex correlation analysis of meteorological elements in the basin show that the water conservation capacity is significantly positively correlated with precipitation, but not with evapotranspiration of reference crops. To a certain extent, the change of land use in the river basin affects the spatial distribution of water conservation capacity, and the areas with high value of water conservation in the upper reaches and the areas where farmland is returned to forest and grassland are significantly affected. The results can provide a reference for the assessment of water conservation capacity in similar river basins.

Abstract:Taking two small watersheds in the first sub-zone (Zone-1) and the fifth sub-zone (Zone-5) of the Loess Plateau as examples and based on UAV image (0.15 m) and DEM (1 m), this paper aimed to analyze the characteristics of gully network, extract and analyze the quantitative characteristics of gullies as well as to compare morphological parameters of normal gullies and big gullies were based on random sampling. The results showed that: the gully channel system in Zone-1 is more complicate than that in Zone-5. The ratio of main gully channel to branches in the watershed in the first sub-zone was 1∶35.6, which was far larger than that in the fifth sub-zone (1∶22.0), and densities of channels in Zone-1 was higher than that in Zone-5. Normal gullies were dominant in both zones with density of normal gully was 9.72 km/km² in Zone-1 and 14.22 km/km² in Zone-5. The number of big gullies were less than normal gullies, with density was 4.27 km/km² in Zone-1 and 4.23 km/km² in Zone-5. Most of normal gullies were grade 1 of channels in both zones, big gullies were belong to grade 1~3, and dry channel were mostly grade 3~5. Except for longitudinal gradient, other morphological parameters of normal gullies in Zone-1 were all smaller than the counterparts in Zone-5, while there was no obvious differences in big gullies in the two zones. Significant power function relationship between the gully volume and area were found for both normal gullies and big gullies in both zones. However, higher determinant coefficients implied that the morphology is more similar for same type of gullies in Zone-1 than that in Zone-5. The results can provide reference for accurate statistics of erosion gullies in the Loess Plateau and comprehensive management of soil and water conservation in small watersheds.

Abstract:To explore wind erosion and deposition features on surfaces in Jilantai salt lake protection system. This study used the plugging-brazing method to observe the actual surface conditions of different protection function areas of the salt lake protection system. Our results showed: The monthly variation of surface erosion and deposition showed obvious fluctuation in different protective function zone of Jilantai salt lake protection system. Fixing shifting-sand zone and fencing dune for grass recovery zone were mainly wind erosion. Surface sediment material tended to be finer from outside to inside. Fixing shifting-sand zone and fencing dune for grass recovery zone are mainly composed of fine sand and medium sand; preventing wind and stopping sand zone and salt lake protection forest zone is mainly composed of very fine sand and fine sand. The average particle size, sorting coefficient, kurtosis and skewness of salt lake protection system ranged from 1.66 to 3.32, 0.99 to 2.91, 1.23 to 2.05 and -0.08 to -0.89. The average grain size, sorting coefficient, kurtosis and skewness of surface sediments increased gradually with salt lake protection system from outside to inside. In general, it appeared that the construction of the salt lake protection system tended to refine in surface sediment, which is conducive to the deposition of fine-grained soil material and played a protective role for the surface.

Abstract:In recent years, due to the dual impact of climate change and human activities, the runoff in many domestic and foreign rivers has been strongly affected. The control basin of Lixian Hydrologic Station in the Xihanshui River basin of the upper reaches of Jialing River was taken as the study area. On the basis of abrupt change point analysis and trend analysis of annual runoff from 1960 to 2016, eight water balance equations of climate elasticity based on the Budyko frame were used to analyze the attribution of runoff changes. The results showed that: (1) The potential evapotranspiration in the study area showed a significant increasing trend (p＜0.01), the runoff showed a significant decreasing trend (p＜0.01), and the precipitation showed a non-significant decreasing trend (p＞0.1). The abrupt change of runoff occurred in 1994, and the study period was divided into the base period and the change period. (2) The contribution rate of climate change to runoff reduction by 8 methods based on Budyko hypothesis ranged from 40% to 50%, the contribution of human activities is between 50% and 60%, taking the leading role. In climate change, the sensitivity coefficient of precipitation obtained by the eight methods is between 2 and 3, and the sensitivity coefficient of evapotranspiration is between -1 and -3. (3)The main effect of human activities on the reduction of runoff is represented by changing the underlying surface. Due to the implementation of vegetation protection measures, the forest area in the study area increased by 68.42 km² from 1990 to 2010, the largest change among all land types, indicating that the significant impact of human activities on the underlying surface.

Abstract:To evaluate the wind erosion climatic erosivity and its response to regional climate change in Northeast China, based on the weather data at the 66 meteorological stations in Northeast China from 1981 to 2019. The spatio-temporal characteristics of wind erosion climate erosivity and its response to climate change were analyzed by using the calculation method proposed by FAO. The results showed that in the past 39 years (1981—2019), the wind speed and relative humidity in Northeast China showed the downward trends, the precipitation showed a fluctuating increase trend, and the temperature showed an increasing trend. The overall trend of wind erosion climate erosivity was high in the west and low in the east, with a spatial average of 18.8 and a spatial range of 0.9 to 63.8. The wind erosion climatic erosivity in spring, summer, autumn, and winter were 10.4, 1.4, 4.1, and 2.9, respectively. The annual wind erosion climatic erosivity in the whole region decreased by 3.71 per decade on average, and decreased by 2.05, 0.24, 0.96 and 0.44 per decade in spring, summer, autumn and winter, respectively. The wind erosion climatic erosivity had obvious spatial character (high in the west and low in the east) and seasonal character (high in spring and low in summer). In the past 39 years, the annual and seasonal wind erosion climatic erosivity all showed the downward trends. This study provides theoretical basis for soil wind erosion control in different agricultural planting areas.

Abstract:Extracting terraces accurately is very necessary for soil and water conservation monitoring and establishing a method of terraced field extraction in small watershed could provide technical support for soil erosion prevention and control on Loess Plateau. Taking Jianjiashan sub-watershed of Tianshui City, Gansu Province Water and Soil Conservation Scientific Experiment Station as the study area, this study tries to use object-oriented classification method to extract terraces by using Unmanned Aerial Vehicle (UAV) image data, which works by determining the optimal segmentation scale parameters based on the scale parameter evaluation tool with texture features of images as the input layer and selecting spectral features and visible vegetation index as the classification features. The results showed that: (1) when the local variance change rate is 101, the terraces boundary is obvious, which shows that the spectral, texture and shape features have great potential for depicting the boundaries of the terraces; (2) the single vegetation indices Color index of vegetation (CIVE), Excess green (EXG), Excess green minus excess red (EXGR), Green/Blue reflectance ratio (GBRI), Green/Red reflectance ratio (GRRI), Normalized green-blue difference (NGBDI), Visible difference vegetation index (VDVI) and Woebbecke (WI) were used as the classification features for terraces extraction, respectively. Among them, EXG vegetation index had the highest accuracy on terraces extraction, with an accuracy of 72.60%. And a method of terrace extraction based on nearest classifier was proposed in this study, which took the composite index (CIVE, WI, EXG, and EXGR) as classification feature to established classification threshold. The accuracy of new method proposed in this study was 91.20%, which was 18.60% higher than that of the classification method with single vegetation index. The object-oriented method based on multi-scale segmentation of UAV images can be applied to the extraction of terraces in loess hilly area, and the comprehensive vegetation index can significantly improve the classification accuracy.

Abstract:Taking Gaxigou Village, Mizhi County, Yulin City, a typical village in northern Shaanxi Province, as an example, the changes of land use landscape pattern and its driving factors under soil and water conservation measures were explored, and it had guiding significance for soil and water conservation, landscape pattern optimization, beautiful countryside construction and ecological sustainable development in the loess hilly region. Based on the remote sensing images of Gaoxigou in 1986, 2004 and 2022, with the help of ArcGIS, ERDAS and FRAGSTATS software, the land use change was analyzed by using the dynamic degree, transfer matrix and landscape pattern index, and the driving factors were discussed. The results showed that: (1) Forestland and grassland were the dominant land types, accounting for about 80% of the total area of Gaoxigou. Arable land and unused land showed a decreasing trend, while water area and construction land had no significant change. The comprehensive dynamic degree of land use gradually decreased and the change of land use tended to be stable. (2) The change area of forestland in the study area was the most significant, mainly change from arable land, and the overall increase area of forestland was 112 hm². The arable land was mainly changed from grassland, while the unused land changed to grassland. (3) Forestland was the most dominant patch in Gaoxigou land use landscape pattern, with the highest degree of fragmentation, and the patches of various landscape types in the study area formed a relatively stable connection with good landscape connectivity. The overall landscape pattern evolved dispersedly, and the area gap of each landscape type was becoming larger and larger. The dominant landscape was obvious, and the overall fragmentation degree was high. (4) Land use change in Gaoxigou was affected by soil and water conservation, industrial structure and related policies. Soil and water conservation was the main driving factor for the reduction of cultivated land, the development of unused land and the increasing of forest and grass area in Gaoxigou. The adjustment of industrial structure and national policy and financial support were the auxiliary influencing factors for the optimization of land use landscape pattern in Gaoxigou.

Abstract:In order to evaluate the characteristics of soil erosion and its driving factors in the Xiaolangdi Reservoir area in the past 30 years, this study estimated the soil erosion modulus in the Xiaolangdi Reservoir area from 1990 to 2020 based on the Revised Universal Soil Loss Equation (RUSLE), and analyzed the spatial-temporal variation characteristics of soil erosion. Then combined with geographic detector, the effects of vegetation coverage, land use type, altitude, slope and rainfall on soil loss patterns were quantitatively analyzed. Results showed that: (1) The soil erosion modulus in the Xiaolangdi reservoir area decreased from 3 150 t/(km²·a) in 1990 to 1 554 t/(km²·a) in 2020, and the total soil erosion decreased by 50.00%. The intensity of soil erosion also changed from high level to lower level. From 1990 to 2020, the area of extremely severe, very severe, severe, moderate and slight erosion decreased by 53.92%, 64.51%, 55.65%, 39.68% and 3.28%, respectively. While the area of very slight erosion increased by 41.13%. At the present stage, the main erosionintensity was very slight erosion, followed by slight erosion, which accounted for 60.02% and 24.08% of the total erosion area, respectively. (2) Serious soil erosion in the Xiaolangdi Reservoir area was mainly distributed in the southwest (Pinglu County, Shanzhou District), southeast (Jiyuan City, Mengjin County) and central (Yuanqu County) of the reservoir area where human activities are concentrated, but it tended to shrink and gather in time and space. (3) Vegetation coverage and land use type had higher explanatory power than other factors, vegetation coverage could explain up to 42.09% of soil erosion, while land use type could explain up to 28.64% of soil erosion, and the interaction of different factors enhanced the explanatory power of soil erosion risk. Low altitude (< 718 m) and gentle slope (8°~16°) areas were high risk areas for soil erosion due to the high accessibility of human activities and low vegetation coverage. Ecological restoration and soil and water conservation measures in these areas should be strengthened.

Abstract:In order to investigate the ecological carrying capacity and sustainable development of the Ningxia Yellow Diversion Irrigation Area, based on the ecological footprint method, the ecological service value equivalent was used to localize the general equilibrium factor and yield factor in the ecological footprint model to quantitatively evaluate the ecological carrying capacity of different land uses in the Yellow Diversion Irrigation Area from 2010 to 2019, and the ecological carrying capacity results were compared with the results of the general factor. The results showed that: (1) the average value of the optimized equilibrium factor was waters (11.735) > forest land (1.561) > grassland (0.901) > cropland (0.785) > building land (0.073) > unused land (0.027), and the mean value of the yield factor is cropland = building land (1.701) > watershed (1.681) > forest land (1.680) > grassland (0.684), which better reflects the ecosystem of Ningxia Yellow River Diversion Irrigation Area capacity to provide production services and differences in national levels. (2) From 2010 to 2019, the overall trend of the ecological carrying capacity and ecological footprint of the Ningxia Diversion and Irrigation Area was to first decline and then increase, and the ecological footprint was always smaller than the ecological carrying capacity. (3) The ecological carrying capacity per capita in the study area had been increasing, the ecological surplus had been expanding, and the ecological quality had been improving. The study of the ecological carrying capacity and ecological footprint of the Ningxia Yellow River Irrigation Area provides theoretical support for the ecological construction of the region, and is of great significance in promoting ecological protection and high-quality development in the Yellow River Basin by leading from a single point.

Abstract:To reveal the change of regional water consumption caused by the hydrological process evolution of evapotranspiration in the Ningxia oasis plain, this study investigated the spatial and temporal evolution characteristics of evapotranspiration in the Ningxia oasis plain and analyzed its driving factors under the platform of Google Earth Engine using MOD16A2 evapotranspiration data from 2001 to 2020. The Sen trend, rescaled range analysis, and multiple regression residual analysis were used as the main methods in the study. The results showed that: (1) The annual average evapotranspiration of overall pixels over the oasis of Ningxia plain was 355.37 mm from 2001 to 2020 and showed a significant increasing trend of 6.75 mm/a (p<0.01). The annual evapotranspiration of cultivated land was 443.50~605.47 mm, which is obviously higher than the regional average evapotranspiration. The annual average evapotranspiration over the oasis of Ningxia plain was much higher than its precipitation in the same period. Therefore, a large amount of irrigation water was needed to maintain the water balance of the oasis ecosystem in Ningxia plain. (2) There was a spatial heterogeneity of evapotranspiration in the oasis of Ningxia plain, which is induced by the differences in land cover types, showing that the cultivated area is higher in evapotranspiration, while the grassland and urban built-up area are lower in evapotranspiration. (3) 77.60% of the areas showed a significant increase in evapotranspiration in the oasis of Ningxia plain. But 93.90% of the areas will had a reverse trend of evapotranspiration after 2020 when compared with the present trend. (4) Human activities strongly drove the increase of evapotranspiration over the oasis of Ningxia plain, and 53.96% of the areas were positively driven by both human activities and climate change. (5) With the gradual increase of evapotranspiration, the water budget in the oasis of Ningxia plain was significantly reduced, which induced the decreasing water supply for photosynthetic production, and soil water remediation in the ecosystem is decreasing. Based on the above results, it can be concluded that human reclamation activities in recent years in the oasis of Ningxia plain have significantly increased the water consumption of the ecosystem, which brought pressure on the regional water balance. In the future, the agricultural reclamation in the oasis of Ningxia plain should be controlled at a reasonable range and the agricultural structure adjustment should be strengthened to mitigate the water resource shortage.

Abstract:In order to study the dynamics of soil water potential of plantations in Bashang area, in this experiment, Zoysia japonica was taken as control, Populus simonii Carr. and Pinus sylvestris var. mongolica, which were typical plantations in Bashang area, were selected to study the soil water potential value and variation coefficient in different time and space in growing season, and the soil water potential variation under sunny days and rainfall in growing season. The results showed that: (1) The change trend of the soil water potential of plantation and grass was the same, the soil water potential was higher at the early and late stages of growing season, and the soil water potential entered the fluctuating and declining period at the middle stage, but different vegetation entered the fluctuating period at different time, and that of P. sylvestris var. mongolica was later than that of P. simonii Carr. and Z. japonica. In addition, the lowest soil water potential of P. simonii Carr. was -1 257.24 kPa at 70 cm, that of P. sylvestris var. mongolica was -747.97 kPa at 10 cm, and that of Z. japonica was -830.11 kPa at 30 cm. The maximum variation coefficient of soil water potential of P. simonii Carr., P. sylvestris var. mongolica and Z. japonica appeared at 10 cm in September, 10 cm in July and 30 cm in July, with values of -155.9%, -208.0% and -183.6%, respectively. On the whole, the variation coefficient was greater in the middle of growing season than that at early and late stages, and that in surface layer was greater than that in deep layer. (2) In sunny days, there was a significant correlation between the maximum value of soil water potential difference of plantations and grasslands and the daily mean temperature. With the increasing of daily mean temperature, the maximum of soil water potential difference also increased. In typical sunny days, the atmospheric temperature fluctuated up and down in the day, and the soil water potential fluctuated with a lag, which was most obvious in the shallow soil during the growing season. (3) There was a correlation between different rainfall and soil water potential difference. With the increasing of rainfall, the soil water potential difference also increased. Under typical rainfall events, the soil water potential of moderate and heavy rainfall profiles rose rapidly, and fluctuated under light rainfall events. From the perspective of different vegetation, grass was more intense than artificial forest. To sum up, the soil water potential of P. sylvestris var. mongolica in the growing season entered into the fluctuating period at the latest, with the largest fluctuating range. The response of soil water potential of Z. japonica was the most sensitive to atmospheric temperature and rainfall. The results were of great significance for guiding the construction of local plantations and efficient management of water resources.

Abstract:The Hanjiang River basin in Shaanxi Province is the main water source of the middle route project of "South to North Water Transfer", and belongs to the national key ecological functional area. The study of the spatial and temporal characteristics of landscape pattern, the correlation between ecosystem service value and landscape ecological risk in the basin has guiding significance for maintaining ecosystem service function in the basin and ensuring ecological security in the basin. Based on the five phases of land use data of the Hanjiang River Basin in Shaanxi Province in 2000, 2005, 2010, 2015 and 2020, the spatio-temporal evolution mechanism and correlation of ecosystem service value and landscape ecological risk under landscape pattern change were studied by using the methods of landscape pattern index calculation, ecosystem service value assessment, landscape ecological risk assessment, etc. The results showed that: (1) From 2000 to 2020, the fragmentation of landscape patches in the watershed was reduced, heterogeneity and connectivity were weakened, and diversity was increased, and various types of landscape developed towards complexity; (2) In the study time domain, the ESV in the study area had increased by 523 million yuan in general, of which the value of climate regulation is the highest, accounting for 41.70%, mainly in low and medium value grades, accounting for about 61.62%; (3) In the study time domain, the ESR in the study area decreased slightly by 1.40%, mainly at low and medium ecological risk levels, accounting for 61.55%; (4) There was a negative spatial correlation between ecosystem service value and ecological risk in the Hanjiang River Basin of Shaanxi Province. The change of landscape pattern makes the ecosystem service function of the Hanjiang River basin in Shaanxi Province increases, the ecological risk decreases, and the spatial autocorrelation between them weakens.

Abstract:In order to deeply analyze the characteristics and driving factors of runoff and sediment variation in watershed, and reveal the mechanism of runoff and sediment variation, the Lianshui watershed located in southern Jiangxi province was selected as the research area. Based on the hydro-meteorological and land use data from 1965 to 2020, at the annual scale and single rainstorm scale, we used the Mann-Kendall test method, cumulative anomaly method, runoff-sediment relationship curve and empirical statistical analysis method to analyze the characteristics of runoff and sediment variation, then established runoff-sediment relationship in different periods, and quantitatively evaluated the contribution rate of precipitation variation and human activities to the change of runoff and sediment. The results showed that at the annual scale, the runoff depth and sediment discharge showed a non-significant downward and extremely significant upward trend, respectively, and the abrupt change years were 1998 and 1995, respectively. Compared with the baseline period, the runoff depth and sediment discharge in different time scales of the changing period fluctuated more greatly, and the correlation between runoff and sediment was increased. The parameter a representing external human interference and the parameter b representing the sediment transport capacity of the river were increased. At the annual scale and single rainstorm scale, the contribution rate of precipitation variation and human activities to the decrease of runoff were -1.1%, 101.1% and 30.2%, 69.8%, respectively, while to the increase of sediment discharge were 0.5%, 99.5% and -2.0%, 102.0%, respectively. The research results could provide a basis for reasonable regulation of runoff and sediment, as well as the sustainable ecological development of watershed.

Abstract:To investigate the availability of soil phosphorus under different vegetation types in red soil erosion area, in this paper, four planting cover types of bare land (CK), coniferous forest (CF), coniferous and broad-leaved mixed forest (CB) and broadleaved forest (BF) were selected from the National Positioning Observation and Research Station of red soil Hilly Ecosystem in Changting, Fujian Province. The forms of iron oxides and phosphorus (P) were determined, and the P solubilizing bacteria (PSM) were determined by high-throughput sequencing technology. The results showed that with the change of vegetation type, the content of moderately active P increased, the content of low active P decreased, and the content of free iron oxide (Fe_d) decreased gradually. The richness and diversity of P solubilizing bacteria increased with the change of vegetation type. At the level of phylum classification, the dominant groups were mainly Proteobacteria, Actinobacteria, Deinococcus-Thermus and so on. The contents of Proteobacteria and acid P increased with the change of vegetation type, and there was a extremely significant positive correlation between Proteobacteria and ACP. In conclusion, with the change of vegetation type, stable P gradually transforms to available P, and soil potential P sources increase. The reduction of free iron oxide content is beneficial to the desorption and mineralization of organophosphorus, which increases the availability of P. The changes in the community structure type and diversity of P solubilizing bacteria are affected by the physical and chemical properties of soil. Phosphorus solubilizing microorganisms can hydrolyze organic compounds and degrade inorganic P fixed in soil by secreting acid P, thus improving the availability of P.

Abstract:In order to study the spatial variability of soil organic matter and its main influencing factors, 193 soil profiles from the second soil survey in Guizhou province were used, based on the meteorological data, land use type map and soil type map of Guizhou province, geostatistics and multiple regression were used to analyze the explanatory ability of each factor to the spatial variability of topsoil organic matter. The results showed that: (1) The organic matter content of surface soil in Guizhou Province ranged from 0.05% to 36.68%, with an average of 5.23%±4.96% and a coefficient of variation of 94.90%. (2) The spatial distribution of topsoil organic matter was higher in the northeast and lower in the southwest. (3) According to the results of semi-variational function analysis, soil organic matter in Guizhou province was mainly affected by natural factors. The comprehensive explanatory ability of altitude, CEC, tillage and soil texture for the variation of organic matter content was 35.9%, and altitude, as the most important influencing factor, could independently explain 25.6% of the variation. CEC and farming methods could explain 11.3% and 7.4%, respectively. There was a negative correlation between surface soil organic matter and average annual temperature and a positive correlation between surface soil organic matter and altitude. There was a correlation between the distribution of surface soil organic matter and the distribution area proportion of carbonate rocks in the study area. On the whole, the distribution area proportion of karst increased with the influence of natural factors. The areas with 0~10% karst distribution area were mainly affected by human activities such as agricultural cultivation and fertilization, 11%~30% were mainly affected by altitude, 31%~50% were mainly affected by average annual temperature and CEC, and 51%~100% of the areas were more affected by elevation, average annual temperature, precipitation, CEC and pH. The results are helpful to understand quantitatively the spatial distribution of organic matter in Guizhou, and provide scientific basis and reference for soil fertility regulation and ecological management.

Abstract:The human activity impact index (HAII) was calculated based on the potential NPP and the actual NPP. Seven natural factors, such as vegetation type, elevation and slope, were further selected and analyze the spatial differentiation combined with HAII, so as to reveal the influence rules of multiple factors at a more detailed seasonal scale. The results showed that the explanatory power and significance of HAII were better than that of human activities in describing the spatial differentiation of vegetation NPP in the Qinghai-Tibet Plateau. In terms of the spatial differentiation of NPP affected by multiple factors, both natural factors and man-made factors showed obvious seasonal differences. The explanatory power of human activities was the highest in summer, weakened in spring and autumn, and was mainly affected by natural factors in winter. Among them, slope, temperature, normal direct radiation and scattered radiation showed a single driving influence in spring, autumn and winter, in summer when vegetation living conditions were better, the factors appeared obvious inflection point, precipitation factor limit threshold changed with the season. In the interaction of factors, the interaction among human activities, precipitation, temperature, and vegetation types was the main driving force which affect NPP in the Qinghai-Tibet Plateau. Combining HAII and multiple natural factors, in the construction of vegetation ecological engineering on the Qinghai-Tibet Plateau, four factors (human activities, precipitation, temperature, and vegetation type) should be mainly considered, and the dominant factors were different in different seasons. In arid and rainless areas, human activities should be given priority. The study aims to provide a reference basis for regional ecosystem management in areas under different vegetation habitat conditions.

Abstract:In order to explore the solidification effect of microbially induced calcium carbonate precipitation (MICP) and plant technology on contaminated mining areas, Lysinibacillus fusiformis, Suaeda salsa and Reamuria songarica were used to carry out the solidification experiment of tailings pollution in arid and semi-arid high wind erosion area. The response effect of contaminated mining area was characterized by plant root tension and root-soil composite shear strength. The results showed that the root tensile strength of R. soongorica and S. salsa increased by 59.9% and 19.7%, and the shear strength decreased by 7.4% and 22.5% after MICP treatment. Compared with before MICP treatment, the shear strength of red sand and S. salsa complex increased by 62.7% and 45.9% at 100 kPa. 200 kPa increased by 130%, 122%; 26.8%, 30.6% at 300 kPa. After cementation, the contents of hemicellulose, cellulose and lignin in the roots of R. soongorica and S. salsa increased significantly (p < 0.05), and the roots of R. soongorica increased by 64%, 74% and 153%, respectively. Suaeda salsa roots increased by 24%, 46%, 95% respectively. In summary, MICP synergistic vegetation provides an efficient and feasible new way for pollution remediation in arid and semi-arid high wind erosion tailings areas. Secondly, the research results can improve the natural environment of the mining area.

Abstract:Based on the monitoring values of seven heavy metals in the sediment of 8 State-controlled Sampling Sites in Huiwanzhong, Luojiaying, Guanyinshandong, Guanyinshanzhong, Guanyinshanxi, Baiyukou, Haikouxi and Dianchinan of Dianchi outer Lake during the ‘13th Five-Year Plan period’(2016—2020), the pollution characteristics and ecological risk assessment of heavy metals were carried out by using the methods of geoaccumulation index and potential ecological risk index, with Origin, ArcGIS, SPSS and other software. The results showed that the average contents of As, Hg, Cr, Pb, Cd, Cu and Zn exceeded the soil background values of Yunnan Province by 0.46, 4.70, 0.47, 0.73, 3.47, 1.17 and 1.13 times respectively, and the spatial and temporal distribution was different. In terms of time variation, the contents of As, Cd, Cu and Zn showed a general downward trend, among which As decreased significantly and showed a linear decreasing trend. In spatial distribution, the high contents of As, Hg, Cr and Pb were concentrated in the southern part of Dianchi outer Lake. Cd and Cu were higher in the eastern waters, while Zn showed a trend of higher in the north and south. The results of geo-accumulation index method and potential ecological risk index method showed that the heavy metal pollution degree and potential ecological risk were high in Dianchinan, Huiwanzhong and Guanyinshanxi of 8 sites, Hg, Cd and Cu were the main indicators of pollution accumulation and potential ecological risk. The results of heavy metal source analysis showed that As, Hg, Cr and Pb were similar pollution sources, preliminary inference as industrial pollution source; Cu and Cd were mainly from agricultural pollution sources.

Abstract:In order to explore the effects of different cultivation methods on soil moisture status, yield, and quality of different genotypes of winter wheat, and to provide a basis for water-suitable planting and agricultural green and sustainable high quality production of dry winter wheat. The soil water status, yield, water use efficiency, and main quality indexes of winter wheat under different cultivation practices were systematically studied by using two planting methods of mulching materials, common polyethylene film covered burrowing (PE) and biodegradable film covered burrowing (BM), compared with traditional open field burrowing (LD). The results showed that under the influence of arid climate and crop water consumption, the average soil moisture in 0-300 cm soil layer was reduced by mulching compared with LD, and the soil moisture in 0-300 cm soil layer was significantly reduced by BM compared with PE. The water consumption BM of winter wheat during the whole growth period increased by 22.0 mm and 23.0 mm, respectively, compared with LD and PE, and the soil water consumption BM > LD > PE during the whole growth period. The mulch yield of LJ 110 in two planting seasons was significantly higher than that of open-field cultivation. In 2018-2019 planting season, LJ 111 PE and BM increased by 40.3% and 29.7% compared with LD. In 2019-2020 planting season, due to severe lodging, PE and BM decreased by 2.5% and 3.5% compared with LD. Compared with LD, plastic film mulching reduced the grain quality of winter wheat, BM significantly increased the dough stabilization time and dough formation time compared with PE, and the average protein content, wet gluten content and weakening degree of LJ 110 grains were increased by 10.6%, 11.1% and 10.3% compared with LJ 111 grains, respectively. Therefore, biodegradable film mulching can play a similar role as polyethylene film in water storage and water conservation, but in winter wheat production in dryland area, biodegradable film mulching should be selected according to the water consumption characteristics of varieties and film cultivation adaptability.

Abstract:Phenolic acids can have a significant allelopathic effect on plants, threaten plant growth and processing product quality. Trichosanthes kirilowii Maxim. was used as the study object. Through the indoor pot experiment, five different concentrations (0, 50, 100, 150, 200 mg/kg, designated as CK, T1, T2, T3, T4) of p-Hydroxybenzoic acid (pHBA), Benzoic acid (BA), and Cinnamic acid (CA) treatment solutions were added to the soil to study their effects on the physiology and soil characteristics of T. kirilowii, and the intensity and law of the allelopathic effect of phenolic acid were elucidated. The results showed that: (1) pHBA at T1 concentration can promote the elongation of the root system of T. kirilowii, and the growth rate of root fresh weight can reach 19.25%; BA affects the biomass accumulation of T. kirilowii, and at T4 concentration, it can inhibit the fresh weight and root fresh weight to 35.17% and 58.38% of the control group; under T4 concentration, CA have the most obvious inhibitory effect on plant height and root length, with the largest decrease of 66.19% and 63.13%. (2) Low concentration of pHBA could enhance root vigor, while high concentration inhibited it, the maximum inhibition rate was 33.55%; the allelopathic effect of BA on root vigor was positively correlated with the concentration, and the maximum inhibition rate was 47.41%. The effect of phenolic acid on transpiration rate and root vigor were slightly different, but the treatment of 150-200 mg/L showed obvious allelopathic inhibitory effect. (3) pHBA and CA improved SOD and POD activity and downregulated CAT activity; BA inhibited the activity of SOD, POD and CAT, which decreased by 47.42%, 59.07% and 45.43%, respectively. The degree of lipid peroxidation of the T. kirilowii membrane increased under all three phenolic acid stresses, but the damage was relieved as the stress time prolonged. (4) Phenolic acid stress significantly changed the soil microecology, and the activities of urease and invertase in the soil were more sensitive to it, and the microbial structure changed from "bacterial" to "fungal". The same concentration of benzoic acid had the deepest allelopathic effect on T. kirilowii cultivation, followed by p-hydroxybenzoic acid and the weakest was cinnamic acid. Therefore, reduction of the phenolic acid content in the soil is conducive to alleviate the allelopathic effect of the T. kirilowii, enhance the viability of the T. kirilowii, and thus improve the yield and quality of the T. kirilowii.

Abstract:In order to explore the effects of water and nitrogen coupling on the yield, quality and water and nitrogen utilization of mountain apples under different irrigation technologies, a three-factor three-level orthogonal experiment was used with a total of 9 treatments, and each treatment was repeated 3 times. The three irrigation technologies were surge-root irrigation (S), ceramic infiltration irrigation (P) and surface drip irrigation (D), the three irrigation volumes were high water (H₁), medium water (H₂) and low water (H₃), and the three nitrogen application rates were high nitrogen (N₁), medium nitrogen (N₂) and low nitrogen (N₃). The response of mountain apple yield and water nitrogen use efficiency to water nitrogen regulation under different irrigation technologies was analyzed. The results showed that irrigation technology had a significant effect on fruit weight, vitamin C and fruit color (p＜0.05), and irrigation water volume and nitrogen application rate had significant effects on apple yield, fruit weight, fruit hardness, color, soluble solids, titratable acid, soluble sugar, vitamin C, sugar-acid ratio, nitrogen fertilizer partial productivity and irrigation water use efficiency (p＜0.05). Mountain apples treated with T₂ (SH₂N₂) had the highest yield (30 490.02 kg/hm²), T₅ treatment (PH₂N₃) had the highest nitrogen fertilizer productivity (104.66 kg/kg), and T₉ treatment (DH₃N₂) had the highest irrigation water use efficiency (70.81 kg/m³). The principal component analysis method showed that the optimal mode of water nitrogen coupling under different irrigation technologies was the combination of surge-root irrigation, medium irrigation volume (65%~80% θ_<em>f), and medium nitrogen application rate (400 kg/hm²) (T₂). The results of this study can provide scientific theoretical basis and technical support for the water and nitrogen management of apples in mountainous areas of northern Shaanxi.

Abstract:The root morphology of the main shrub species in the arsenic sandstone area was quantitatively studied to explore which soil and water conservation plants could effectively resist the composite erosion of the arsenic sandstone area, and the shrub species Hippophae rhamnoides L.、Ziziphusjuba M.、Forsythia suspensa V.、Xanthoceras sorbifolium B.,Rosaxanthina L. and Amygdalus mongolica R. was the research object, and the root distribution range, geometric morphology, topological index, mechanical characteristics of a single root, and dimensionality reduction were comprehensively analyzed, and shrub plants with good soil consolidation effect in arsenic sandstone area were screened. The results showed that: (1) Oblique roots were the main ones for Xanthoceras sorbifolium B. and Forsythia suspensa V., while horizontal roots were dominated by Hippophae rhamnoides L., Ziziphusjuba M., Rosaxanthina L. and Amygdalus mongolica R.; Thin roots and long roots,Xanthoceras sorbifolium B. (2 368.54 cm)＞Hippophae rhamnoides L. (1 746.12 cm)＞Rosaxanthina L. (1 463.15 cm)＞ Amygdalus mongolica R. (1 162.81 cm)＞ Ziziphusjuba M. (928.69 cm)＞ Forsythia suspensa V. (817.45 cm), longythia topological index of 0.54 and fork-shaped branch structure, forsythia topological index of 0.71 and fishtail-shaped branching structure. (2) Average tensile strength of roots, Xanthoceras sorbifolium B. (30.45 MPa)＞Rosaxanthina L. (18.21 MPa)＞Forsythia suspensa V. (17.03 MPa)＞Amygdalus mongolica R. (16.62 MPa)＞Ziziphusjuba M. (16.34 MPa)＞Hippophae rhamnoides L. (15.35 MPa). Based on the principal component analysis method, the root soil consolidation effect of different shrub species was compared, and the comprehensive principal component index of theXanthoceras sorbifolium Bunge.reached 2.28, which was the best comprehensive soil consolidation effect, which could selectsuitable soil conservation shrubs for sandstone areas and provide theoretical reference for the sustainable development of shrub forests in this area.

Abstract:In order to study the changes of nitrogen and phosphorus stoichiometry in soil and runoff under long-term fertilization and tillage, five treatments (three replicates were set in each treatment) were set up on the sloping land of purple soil∶ downslope tillage without fertilization (CK), downslope tillage with mixed application of chemical fertilizer and organic fertilizer (T1), downslope tillage with chemical fertilizer (T2), downslope tillage with 1.5 times increment of chemical fertilizer (T3), and contour tillage with fertilizer (T4), to analyze the change characteristics of soil total nitrogen (TN_S), soil total phosphorus (TP_S) and TN_S∶TP_S, runoff total nitrogen (TN_W), runoff total phosphorus (TP_W) and TN_W∶TP_W in 83 runoff-producing events during 2008-2017. The results showed that the contents of TN_S and TP_S in CK treatment were not significantly different from those in T1 treatment, but significantly lower than those in T2, T3 and T4 treatment. The main reason was that the application of chemical fertilizer significantly increased the content of nitrogen and phosphorus in soil. The mean value of TN_S∶TP_S was 3.55~4.79, and the CV value was 0.39~0.94, indicating that fertilization had no significant effect on N/P ratio. The concentration of TN_W in CK treatment was significantly higher than that in other fertilization treatments, and the concentration of TN_W in T1 treatment was not significantly different from that in T2 treatment, but significantly higher than that in T3 and T4 treatment. The TP_W concentration of CK treatment was not significantly different from that in T2, T3, T4 treatment, but significantly lower than that in T1 treatment. The TN_W∶TP_W of CK treatment was significantly higher than that in fertilization treatments, but there was no significant difference in TN_W∶TP_W among fertilization treatments. The mean values of each treatment was 25.48~56.83, and the CV value was 1.11~1.80. Fertilization significantly reduced the N/P ratio in runoff and stabilized the difference between rainfall events. Annual mean TN_W and TP_W were both significantly positively correlated with annual mean TN_S and TN_S∶TP_S, indicating runoff N loss concentration was significantly affected by soil N content, while annual mean TN_S∶TP_S and TN_W∶TP_W were not significantly correlated. Fertilization and tillage could decouple the relationship between nitrogen and phosphorus stoichiometry in soil and runoff. The results can provide theoretical basis for the prevention and control of agricultural non-point source pollution.

Abstract:A 2-year experiment was conducted to investigate the effects of different lateral spacing and mulching methods on soil moisture, soil NO₃^- concentration, soil water spatial distribution uniformity (CU_w), soil NO₃^- spatial distribution uniformity (CU_N), shoot-root growth, grain yield, and harvest index (HI) of spring maize in Hetao Irrigation District. The experiment included two lateral spacing (A1: 1 m; A2: 0.5 m) and two mulching methods (M1: fully mulched; M2: partially mulched). Results showed that soil moisture was consistent with CU_w in root zone, however, the increased soil NO₃^- concentration did not lead to an increased CU_N under high-frequency mulched drip fertilization. The improvement of soil water (and CU_w) and NO₃^- (and CU_N) did not significantly influence crop root length (or weight) density, but it increased leaf area, and finally reduced root-shoot ratio. Compared with laterals layout, mulching methods imposed more effects on crop yield and HI. Under low-frequency irrigation condition, compared with partial mulching, full mulching increased soil moisture and NO₃^- concentration in root zone and resulted in higher crop yields and HI; however, grain yields and HI in full mulching were lower than that in partial mulching under high frequency irrigation condition. In this study, grain yields and HI were the highest when the ratio of root surface area and leaf area (RSA/LA) was equal to 4, the too high or too low RSA/LA reduced crop yield and HI. Based on high grain yield, HI, and low costs of drip taps, A1M2 was recommended under high fertigation frequency, while A1M1 was recommended under low fertigation frequency.

Abstract:In order to determine the variation characteristics of soil moisture after the transformation of karst slope land into the terraced field, the typical karst slope citrus orchard and terraced citrus orchard were taken as the research objects, and the soil water content of different depths soil layers (0-70 cm) was continuously monitored for one year (376 days). The results showed that: (1) The average soil water content of terraced citrus orchard (32.64%) was little different from that of sloping citrus orchard (33.05%). The soil water content (43.35%) in the surface layer (0-10 cm) of terraced orange orchard was significantly higher than that of sloping citrus orchard (34.24%). Both of them demonstrated a violent fluctuation in the rainy season and a relative gentle change in the dry season. In the terraced citrus orchard, there was a substantial difference in soil moisture between the surface soil and the lower layer, while there was no variation in the soil moisture among each soil layer in the sloping citrus orchard. (2) In the rainfall events with different rainfall amounts, the overall increase of soil water content in terraced citrus orchard was greater than that in sloping citrus orchard. Within 24 hours after the rain stopped, the decline rate of surface soil water content in the terraced orchard was slower than that in the sloping citrus orchard, but within a week, the water content of all soil layers in terraced orange orchard declined faster than that in sloping orange orchard. (3) The average relative available water of the terraced citrus orchard and sloping citrus orchard was 0.37 and 0.38, respectively. Compared with the non-karst region, the water conservation effect of terraced fields in karst peak-cluster depressions was relatively insignificant. The results of this study could provide a scientific basis for the quantitative evaluation of water conservation benefits of slope-to-terrace measure in karst area.

Abstract:Under the hydrological processes of soil matrix infiltration, the effect of fertilization measures of eucalyptus plantations during the short rotation period on groundwater needs a new understanding. The surface soil (0-20 cm) of differently aged eucalyptus plantations (1 year, 2 years, 3 years, and 5years) were used as the research object. Filled soil columns were used to simulate the leaching process of ammonium nitrogen, nitrate nitrogen, total dissolved nitrogen, and dissolved organic nitrogen driven by matrix infiltration. The change between the infiltration characteristic parameters and the leaching process of different forms of dissolved nitrogen and their influence factors were studied. Results showed that: (1) The steady infiltration rate and cumulative infiltration showed an increase-decrease-increase trend with plantation age increment, therein the steady infiltration rate (143 mm/h) and cumulative infiltration (279 mm) of on the suface soil of 2-years old eucalyptus plantation were the largest. (2) The concentrations of different forms of dissolved nitrogen in the leachate reached to the peaks at the beginning of leaching process and gradually decreased with the matrix infiltration rate decrease. Also, the matrix infiltration rates and the concentration of four nitrogen forms in the leachates showed the well linear relationships. (3) The nitrate nitrogen and dissolved organic nitrogen were the main forms of nitrogen leaching on the surface soil of eucalyptus plantations. The sand content increment promoted the nitrogen leaching, while the clay content and soil organic matters increment restrained the nitrogen leaching. Simultaneously, the concentrations of ammonium nitrogen at the initial leaching stage were higher than the threshold of groundwater quality, which was a potential threat causing the groundwater pollution in eucalyptus plantations. In summary, soil matrix infiltration was an important factor of nitrogen leaching of topsoil in eucalyptus plantations, and they had the coupling change trend and a linear relationship. The contents of sand, clay, and soil organic matters were the important factors affecting the nitrogen leaching on the surface soil of eucalyptus plantations.

Abstract:In order to explore the nitrogen reducing effect of synergists on dryland wheat in Sichuan, the following 9 treatments were set up in this study: blank control (CK0); Conventional nitrogen application without topdressing (CK1, nitrogen application amount 187.5 kg/hm²); The ratio of basal dressing to topdressing under conventional nitrogen application rate is 6∶4 (CK2, nitrogen application rate is 187.5 kg/hm²); Synergistic auxiliary mixed with conventional compound fertilizer, reducing nitrogen by 20% (jf—20%) and 30% (jf—30%); Synergistic auxiliary chelating urea formaldehyde reduces nitrogen by 20% (jn—20%), 30% (jn—30%) and 40% (jn—40%); Synergistic auxiliary chelated urea formaldehyde fertilizer + lecithin organic fertilizer 3 000 kg/hm² reduced nitrogen by 27% (jny—27%); The dynamics of soil nitrogen, wheat chlorophyll content, leaf area index, growth rate, nitrogen accumulation and transport, yield and its composition, and nitrogen utilization efficiency were analyzed and measured under different treatments. The results showed that each treatment of jf, jn and jny model significantly reduced the content of ammonia nitrogen and nitrate nitrogen in soil at flowering and mature stages, which were 6.8%~9.8% and 8.7%~14.5% lower than that of CK1 at flowering stage, and 14.9%~20.8% and 15.9%~20.0% lower at mature stage, respectively. At 30 days after anthesis, the leaf area index of jn—20% and jny—27% was the highest, 5.3% and 5.8% higher than that of CK1 and CK2, respectively. The leaf area index of jn—20% and jny—27% was 5.83% and 5.24% higher than that of CK1; Each treatment of jf, jn and jny mode significantly increased the post anthesis nitrogen accumulation compared with CK1 and CK2, with the amplitude of 33.7%~73.1% and 29.8%~68.0% respectively, and the post anthesis nitrogen transport increased by 116.1%~217.8% and 107.1%~204.0% respectively. The growth rate of each treatment of jf, jn and jny in flowering maturity stage was higher than that of CK1, and the range was 13.2%~33.8%. Moreover, wheat yield will not decrease after nitrogen fertilizer reduction and synergist application. The yield increase of jf—20%, jn—20% and jny—27% was 0.2%~2.9%, and the yield of jn—20% and jny—27% treatment was the highest, 2.6% and 2.9% higher than that of CK1, however, there is no significant difference with CK1 and CK2. jn, jf and jny modes significantly improved nitrogen utilization efficiency and partial productivity of nitrogen fertilizer, which were 6.7%~24.0% and 10.3%~25.8% higher than CK1 respectively. According to the research, the synergists can improve the fertilizer utilization rate by promoting nutrient absorption and reducing nitrogen residues in the soil, so as to reduce nitrogen without reducing production. The application of synergists to mix fertilizer and synergists to chelate urea formaldehyde can reduce nitrogen by 20%, and synergists to chelate urea formaldehyde with lecithin organic fertilizer 3 000 kg/hm² can reduce nitrogen by 27%.

Abstract:In order to reveal the response mechanism of nutrient cycling and water cycling to nitrogen deposition in forest ecosystem, we conducted a study on a situ decomposition of leaf and twig litters of Pinus armandii forest and Pinus yunnanensis forest in the middle Yunnan Plateau. Four treatments were set up: control (N 0 g/ (m²·a), CK), low nitrogen (N 10 g/ (m²·a), LN), medium nitrogen (N 20 g/ (m²·a), MN) and high nitrogen (N 25 g/ (m²·a), HN). Nylon mesh bag method and laboratory soaking method were used. The response of nutrient element residual rate, water holding capacity, water holding rate and water absorption rate of leaf and twig litters to nitrogen addition were explored. The results showed that: (1) With the continuation of decomposition time, carbon, nitrogen and phosphorus content of leaf and twig litters in two types of forests showed the trends of release, enrichment-release and enrichment, respectively, and the residue rates of C, N and P in leaf litters were significantly lower than those in twig litters (p ＜ 0.05). (2) The maximum water holding capacity and water absorption rate of leaf litters were significantly higher than that of twig litters (p ＜ 0.05). After 24 months of decomposition, compared with CK, the C residual rates of leaf and twig litters in two types of forests, and the N residual rate of leaf litters in P. armandii forest under LN treatment were reduced by 1.98%~7.27% and 10.79%, respectively. The C residual rates of leaf and twig litters in two types of forests, and the N residual rate of leaf and twig litters in P. armandii forest and twig litters in P. yunnanensis forest, the P residual rate of twig litters in P. armandii forest under HN treatment increased by 4.26%~9.08%, 11.94%~44.51% and 42.42%, respectively. (3) After 24 months of decomposition, compared with CK, the maximum water holding capacity and water absorption rate of leaf and twig litters in P. armandii forest and leaf litters in P. yunnanensis forest under LN, MN and HN treatments decreased by 11.44%~25.24% and 5.81%~32.23%, respectively; while twig litters in P. yunnanensis forest increased by 15.48%~24.26%, 17.97%~23.74%, respectively. (4) The water capacity of leaf and twig litters in two types of forests increased with the extension of soaking time, but the water absorption rate decreased. The relationship between water capacity and soaking time was logarithmic function (m=a+bln t), and the relationship between water absorption rate and soaking time was power function (v=at^-b). (5) C content was positively correlated with the water holding capacity of twig litters in P. yunnanensis forest (p ＜ 0.05), N content was negatively correlated with the water holding capacity of leaf litters in two types of forests (p ＜ 0.05). In conclusion, nitrogen addition affects the water holding capacity of litters by changing the residual characteristics of C, N and P nutrient elements during the decomposition process.

Abstract:In order to explore the effect of long-term application of different types of exogenous carbon on soil carbon storage and carbon sequestration potential of topsoil ash desert soil, the field positioning experiment, which included 5 treatment as no straw is returned to the field (NPK), NPK+ 1.5 t straw (NPKS), NPK+ 1.5 t organic fertilizer (NPKM), NPK+1.5 t cotton stalk carbon (NPKB1), and NPK+3.0 t cotton stalk carbon (NPKB2) was conducted. Soil collected from 2015 to 2021 was used as the research object. The correlation between soil bulk density (BD), organic carbon density (SOCD), organic carbon accumulation rate, organic carbon storage (SOCR), application years and organic carbon accumulation rate was analyzed. The results showed that (1) From the perspective of BD trend from 2013 to 2021, the application of NPKS, NPKM, NPKB1, and NPKB2 showed a consistent decreasing trend compared with NPK, with an average decrease of 1.84%, 0.86%, 5.03% and 6.66% compared with NPK, respectively. (2) Compared with NPK, soil SOCD increased by 12.21%, 11.04%, 24.14%, and 46.95% in NPKS, NPKM, NPKB1, and NPKB2 treatments, respectively, and cotton stalk carbon significantly improved soil SOCD. The cumulative rate increased by 73.16%, 66.95%, 133.52%, and 247.18%, respectively. (3) SOCR increased by 11.67% to 30.88% and 12.2%~33.24% in NPKS and NPKM treatments, respectively. NPKB1 and NPKB2 had the most significant SOCR improvement, with the highest improvement of 29.28% and 45.44% compared with 2013, respectively. Taken together, straw returned, cotton and organic carbon application is the effective measures to improve soil carbon of gray desert soil, in which addition of cotton carbon is more advantageous in short-term rapid increase soil organic carbon and carbon sequestration. Cotton charcoal itself contains rich nutrients. Long term cotton carbon addition increases soil carbon sequestration, improves soil fertility, alleviates the greenhouse effect, and is an effective way to achieve carbon neutrality.

Abstract:In order to explore the effects of Dicranopteris dichotoma on the monthly dynamics and turnover of soil microbial biomass carbon and nitrogen in the restoration process of Pinus massoniana forest in eroded degraded red soil, the P. massoniana forests with different restoration years were used as the research object. The contents of soil microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN), turnover rate, turnover time and flux in the soil of 12 months in the soil of P. massoniana forest with D. dichotoma, removal of D. dichotoma and bare land were compared and analyzed, and their relationships with soil physical and chemical properties were analyzed. The results showed that : (1) The average content of MBC and MBN in the treatment of retaining D. dichotoma was 26.99%~277.31% and 13.54%~173.39% higher than that in the bare land, while the distribution of the treatment of removing D. dichotoma was 12.29%~27.01% and 5.02%~28.45% lower than that of retaining D. dichotoma. (2) The seasonal dynamics of soil microbial biomass carbon and nitrogen in all treatments showed a trend of higher in spring and summer and lower in autumn and winter, the soil microbial biomass carbon and nitrogen content before entering the growing season can better reflect the average level of the region; (3) In the restoration process of degraded P. massoniana forest, D. dichotoma coverage decreased soil microbial biomass carbon and nitrogen turnover rate, increased turnover time, increased soil microbial biomass carbon and nitrogen content and flux, and promoted soil organic matter accumulation and nutrient release. Correlation analysis and stepwise regression analysis showed that MBC and MBN flux were significantly positively correlated with DOC and DON, respectively, and turnover rate was significantly negatively correlated with NH₄⁺-N and TN, respectively, indicating that soil carbon and nitrogen and their availability were key factors affecting soil microbial biomass turnover.

Abstract:To reveal the evolution of C, N, and P contents and ecological stoichiometric ratios along the litter-soil continuum during the restoration of sand-fixing forests, artificial shrub and arbor stands with 25-56 years restoration in the Mu Us sandy land of Yulin were taken as the study object, we measured and analyzed the dynamics of carbon (C), nitrogen (N), phosphorus (P) contents, and their stoichiometric ratios along the restoration years and continuum profiles in semi-fixed sandy sites, from the litter layer to the humus layer and then to the mineral soil layer. The results showed that the C, N, and P contents and their stoichiometry in the two types of woodland at different restoration years were all in the litter layer > humus layer > mineral soil layer. However, the C content of the litter, humus and mineral soil layers increased significantly with the extension of the restoration period, with an average increase of 1.76, 35.70, and 6.45 times compared with that of the semi-fixed sandy land at 56 years; the P content increased significantly in the humus and mineral soil layers, with an average increase of 1.67 and 2.11 times, respectively; the N content increased significantly only in the mineral soil layer, with an average increase of 4.16 times. The change in stoichiometry of the two woodlands showed a significant increase in C∶N in the humus layer with the increase of restoration years, with an average increase of 18.6 times compared with the semi-fixed sandy land at 56 years; N∶P increased significantly only in the shrub continuum; C∶P did not change significantly. Correlation analysis showed that the C content of all layers in the two woodland continuums reached a highly significant positive correlation, and the C of the mineral soil layer was also highly significantly positively correlated with N and P. The C∶N and C∶P of the humus layer were highly significantly positively correlated with the C∶P of the mineral soil layer. In conclusion, the C content of the litter-soil continuum increased synergistically during the vegetation restoration process in Yulin Mu Us sandy land, while the N and P contents increased significantly only in the mineral soil layer, and C∶P was a relatively balanced and stable stoichiometric feature in the continuum.

Abstract:In order to study the effects of different amounts of calcium and magnesium hydrotalcite on the soil characteristics of cadmium-contaminated rice fields, the yield of double cropping rice and the cadmium accumulation in rice, and to explore the best application mode of calcium and magnesium hydrotalcite in cadmium contaminated double cropping rice fields, in 2021, field experiments were conducted in the heavy cadmium contaminated rice fields (total cadmium content 1.16 mg/kg) in Liangtian Town, Chenzhou City, Hunan Province, using early rice varieties Xiangzaoxian 45 and Luliangyou 996, late rice varieties Chuang Liangyou 669 and Yuzhenxiang as experimental materials, The soil characteristics, yield components and cadmium accumulation of double cropping rice under four treatments of calcium magnesium hydrotalcite (0, CK; early rice basal application of 3 000 kg/hm², T1; early rice basal application of 1 500 kg/hm², T2; early rice basal application of 750 kg/hm²; late rice basal application of 750 kg/hm², T3) were compared. The results showed that: (1) The application of calcium magnesium hydrotalcite could increase the soil pH and the contents of alkali hydrolyzable nitrogen, available potassium, and available phosphorus, respectively by 0~3.06%, 4.30%~13.80%, 6.67%~40.00%, and 25.53%~30.47% at the maturity of early rice, respectively, and 1.56%~4.07%, 11.79%~14.50%, 15.79%~31.58%, 3.73%~17.17% at the maturity of late rice, showing a trend of T1 > T2 > T3. (2) Application of calcium and magnesium hydrotalcite could reduce the content of available cadmium in soil. The content of available cadmium in early and late rice ripening stages was reduced by 5.26%~42.86% and 18.19%~36.84% respectively, with a trend of T1 > T2 > T3. (3) The content of cadmium in brown rice and the accumulation of cadmium in the upper part of plant at maturity were the lowest in T1, the second in T2 and T3, and the highest in CK. The content of cadmium in Xiangzaoxian 45 decreased by 33.33%~44.44% and 4.89%~20.76% respectively, that in Luliangyou 996 decreased by 30.00%~60.00% and 6.00%~30.98% respectively, that in Yuzhixiang decreased by 27.78%~50.00% and 15.93%~34.07% respectively, and that in Chuang Liangyou 669 decreased by 26.67%~60.00% and 12.58%~28.56% respectively. (4) The yield of double cropping rice Xiangzaoxian 45, Chuang Liang You 669 and Yuzhen Xiang was the highest in T1, followed by T2 and T3, and the lowest was in CK; The yield of Luliangyou 996 was the highest in T2 treatment, the second in T1 and T3 treatment, and the lowest in CK treatment. Calcium magnesium hydrotalcite increased the yield of early and late rice by 4.11%~10.79% and 1.69%~11.29%, respectively. This experiment shows that the larger application amount of calcium magnesium hydrotalcite has a better effect on rice yield increase and cadmium reduction, but considering the significance of rice yield and cadmium content difference between treatments and the cost of calcium magnesium hydrotalcite, 1 500 kg/hm² calcium magnesium hydrotalcite is more appropriate under this experiment condition.

Abstract:In order to explore the feasibility of wood vinegar in remediation of heavy metal contaminated farmland soil, a field plot experiment was conducted to study the effects of wood vinegar application on the growth of three local wheat varieties in Cd contaminated farmland, the Cd accumulation and translocation in wheat, and the content and form of Cd in rhizosphere soil. The results showed that the application of wood vinegar significantly increased the biomass of wheat grains and straw (p<0.05), and the Cd distribution coefficients of straw increased from 8.91% to 20.44%, while that of grains and roots decreased from 13.93% to 35.93% and 4.76% to 18.76%, respectively. The bioaccumulation factor of Cd in straw and roots of different wheat varieties all significantly increased, showing that variety C > variety A > variety B. The translocation factor of Cd in root-straw (TF_root-straw) was significantly increased in all wheat varieties, while the translocation coefficients of Cd in straw-grain (TF_straw-grain) was significantly decreased except variety C. Compared with before planting, the Cd content in rhizosphere soil of each variety of wheat decreased by 0.26, 0.23 and 0.21 mg/kg, respectively, and the Cd content in rhizosphere soil treated with wood vinegar decreased by 13.11 %~16.97 %. The forms of Cd in soil were significantly different before and after wheat planting, the exchangeable state and Fe-Mn oxide bound state were significantly increased (p<0.05), while the organic matter bound state and residual state were significantly decreased (p<0.05). Therefore, the application of wood vinegar significantly increased the biomass of each part of wheat, and had no significant impact on the content of Cd in grains, and increased the translocation factor of root to straw, which contributed to the accumulation of Cd in wheat straw, but did not increase the risk of wheat grain exceeding the standard, the Cd could be gradually removed from farmland soil through straw leaving.