Abstract:Vegetation restoration is one of the key processes affecting the dynamic change of soil organic carbon pool.To elucidate the soil organic carbon sequestration dynamics and its driving mechanism in the process of vegetation restoration is a hot and frontier issue in the study of carbon cycle under global change.This paper reviewed the published studies on the dynamics of soil organic carbon sequestrations in the process of vegetation restoration and its driving mechanism in recent years at home and abroad,analyzed the dynamic of soil organic carbon sequestration and its influencing factors in vegetation restoration,explored the influencing mechanism of plant carbon input on the dynamics change of soil organic carbon,and revealed the physical,chemical and microbial driving mechanisms of soil organic carbon sequestration in vegetation restoration.Furthermore,the review summarized the problems existing in the current research,and then the urgent research on soil organic carbon sequestration during the vegetation restoration process in the future was proposed to further strengthen the aspects of soil organic carbon component dynamics,microbial structure and function,and the synergistic mechanism of plant-soil-microorganism on soil organic carbon sequestration.This review can point out the future direction for the study of vegetation restoration and soil carbon sequestration stabilization mechanism,and then provide scientific reference for promoting soil carbon cycle of vegetation restoration,scientific evaluating the potential of soil carbon sequestration and effective implementing measures in ecosystem carbon sink management.

Abstract:The erosion of gully head forward,gully bank expansion,and gully bed cutting seriously affect regional grain production and environmental quality.Taking the gully head,gully bed,and gully bank of three stable eroded gullies in Yuwa Watershed of Pengyang County,Ningxia as subjects,this study combined field survey sampling with laboratory experiment.The soil physicochemical properties and erodibility K values of different parts of erosion gully (gully head,gully bed and gully bank) were analyzed.The 0—10,10—25,25—40,40—55,55—70 cm soil,soil mass water content (θ),soil bulk density (ρ),soil total porosity (φ),soil clay (CLA),soil silt (SIL),sand (SAN) content,＞0.25 mm water-stable aggregate content (R_0.25),soil mean weight diameter (MWD),soil geometric mean diameter (GMD) and soil organic matter (SOM) content were collected,and EPIC model was used to calculate K value of soil erodibility.The results showed that:(1) The quality of each part of the erosion gully average moisture content,total porosity,organic matter,silt content,aggregate content of water stability > 0.25 mm,average weight diameter and geometric mean diameter of the size of the order of gully bed > gully bank > gully head,the average soil bulk density and sand content of each part were gully head > gully bank > gully bed,the average soil clay content was gully bank > gully head > gully bed,the mechanical composition of the soil in each part was silt > sand > clay.(2) The K value of soil erodibility in each part of the erosion gully ranges from 0.032 9 to 0.039 5(t·hm²·h)/(MJ·mm·hm²),which belonged to the medium erodibility.The average K value of erodibility was gully head > gully bank > gully bed.(3) The K value of soil erodibility was significantly negatively correlated with soil silt and clay content,and significantly positively correlated with soil sand content,organic matter and mass water content.Soil erodibility K value in gully bed was significantly negatively correlated with R_0.25,MWD and GMD (p<0.01).As the most active part of erosion gully,the number and stability of aggregates were increased by increasing soil organic matter content and silt content,thus reducing soil erodibility.The results can provide basis for ecological stability and evaluation of erosion gully.

Abstract:Rock surface flow is ubiquitous in karst rocky desertification area exposed to bedrock,and it is easily affected by the shape of rock surface to scour soil at the rock-soil interface in the way of aggregation or dispersion,which is an important physical process of soil erosion/leakage in the karst rocky desertification area.In order to analyze the effect of rock surface flow on the soil particle distribution at rock-soil interface under different rock surface shapes,and reveal the erosion effect of rock surface flow on the soil at rock-soil interface,the fallow farmland (1-year erosion of rock surface flow) with typical rocky desertification characteristics was selected in this study,in which three typical rock surface shapes (flat,convex and concave) as the research objects.The distribution characteristics of soil particles at different horizontal distances (0~2,2~4,4~6,6~8,8~10,20 cm) and different soil layers (0—10,10—20 cm) from rock-soil interface were analyzed by laser particle size analyzer.The results showed that:(1) The influence of rock surface flow on soil erosion under different rock surface shapes is in the order:concave＞flat＞convex.The clay content of soil at the concave rock-soil interface was the lowest,and that at the convex rock-soil interface was the highest.(2) The erosion effect of rock surface flow on the soil at the rock-soil interface was mainly concentrated in the horizontal distance of 0~2 cm from the rock-soil interface.Within the range,the sand content of the soil at the concave rock-soil interface was significantly higher than that of the convex and straight type,while there was no significant difference in the distribution of soil particles at other horizontal distances from the rock-soil interface.(3) Under the influence of rock surface flow,the average fractal dimension of soil particles at rock-soil interface was in the order of convex type＞flat type＞concave type,which was proportional to the content of clay in soil and inversely proportional to the sand content.The results could provide scientific reference for further understanding the occurrence process of soil erosion/underground leakage in bedrock exposed rocky desertification areas.

Abstract:To study the vegetation root systems of the arid inland river bank slope erosion quantitative influence of the process,taking the tarim river as the research object,the BSTEM model was adopted to simulate the scour process of 8 typical bank slopesin two successive hydrological years 2016—2017.The quantitative effects of the root systems of six typical desert vegetation species (Alhagi sparsifolia(AS),Tamarix ramosissima(TR),Phragmites australis(PA),Glycyrrhiza uralensis(GU),Populus euphratica(PE),Nitraria tangutorum(NT)) on the riverbank scour were analyzed.Results demonstrated that:(1) The collapse of the Tarim River bank basically occurred in recession period and dry period.The stability of bank slope changed periodically in hydrological years.The safety factor F_s fluctuated slightly between dry period and level rising period,and was stable on the whole and riverbank.F_s increased briefly at the high-water level during the flood period.Subsequently,with the erosion of water flow and the decline of water level,F_s continued to decline until the riverbank collapses,and then entered the cycle of the next hydrological year.(2) The improvement effect of vegetation root systems on the stability was different at different water level periods,which was as follows:flood period > level rising stage > dry period > recession stage.(3) There was a significant difference in stability enhancement among different vegetation types,as follows:NT > AS > GU > TR > PE >PA.(4) At different water lever periods,the reduction effect of vegetation root systems on the amount of riverbank flushing was different,recession stage > flood period > level rising stage > dry period.The root system reduced the amount of riverbank flushing by 0.77% to 49.36%,and the effect of different vegetation on the amount of riverbank flushing was different,which was as follows:NT > GU > TR > AS > PE > PA.The effect of different vegetation on the stability of safety factor and the reduction of bank slope washing volume was basically the same.The results can provide theoretical reference for the ecological management of Tarim River.

Abstract:Contour tillage is one of the typical agriculture tillage measures,which affects the soil erosion process of sloping farmland by affecting the slope filling and infiltration.In this study,the rainfall intensity (90 mm/h),five surface slopes (3°,5°,10°,15°,20°) and two types of slop treatments (contour tillage and flat slop) were designed through artificial simulated rainfall experiments,comprehensive comparison and analyses of indicators such as runoff rate,sediment rate,runoff sediment concentration and runoff reduction and sediment reduction benefits were carried out,compared with the flat slope,the effects the contour tillage on soil erosion process of slopeing farmland on the Loess Plateau were explored.The results showed that:(1) Compared with flat slope,the initial runoff producing time on the slope was significantly delayed by 11.58~31.91 min under contour tillage.With the increase of slope,the effect of prolonged the initial runoff producing time under contour tillage was gradually weakened.(2) The runoff rate and sediment rate were weakened under contour tillage.Compared with flat slope,the slope runoff rate,sediment rate and runoff sediment concentration under contour tillage were reduced by 11.77%~94.92%,20.69%~99.27% and 2.46%~88.40%,respectively.However,the ability of contour tillage to reduce runoff and sediment production is limited,and the runoff tate,sedimeat rate and runoff sediment concentration under contour tillage slope may be closed to or greater than that of the flat slope if ridge breaking occurs on the slope.(3) In the process of rainfall,the relationship between the accumulated sediment production and the accumulated runoff meet the linear positive correlation,and the increase of the accumulated sediment production with the accumulated runoff under contour tillage is always smaller than that of flat slope.(4) The contour tillage has good benefits of runoff and sediment reduction on different slopes,the benefits can reach 45.35%~100% and 58.92%~100% respectively,and the sediment reduction effect is obviously better than the runoff reduction effect.The results revealed the influence mechanism of contour tillage on slope erosion process,and provided a scientific basis for soil erosion control in slope farmland.

Abstract:Vegetation is an important factor affecting slope soil erosion process,thus exploring the response of slope sediment yield and sediment connectivity to vegetation spatial distribution is of great significance to reveal the mechanism of soil erosion process and predict slope erosion.In this study,based on the indoor scouring experiment,the sediment reduction efficiency of three common slope vegetation distributions (upper slope,middle slope,lower slope) under different flow discharge (3.2 and 5.2 L/min) and vegetation cover (0,30%,50% and 70%) were analyzed.And a sediment connectivity index (the index of potential sediment yield) was used to explore the characteristics of sediment connectivity influenced by vegetation.The results showed that:(1) The sediment reduction efficiency of vegetation distribution varied with the coverage.According to the average and variable amplitude of sediment reduction efficiency,the effect of vegetation distribution on the lower slope was best compared with other vegetation distribution.However,its gap in different vegetation distribution was reduced with the increase of the flow discharge.(2) The effects of flow discharge on sediment yields were slightly greater than that of vegetation when the vegetation cover was smaller (≤30%).But the role of vegetation enhanced gradually and became the dominant influencing factor with the increase of vegetation cover.(3) The index of potential sediment yield was significantly different under varied vegetation cover and distribution.As the vegetation cover increased,the index decreased and the sediment connectivity weakened.And the index of vegetation distribution on the lower slope was smallest and its sediment connectivity was worst compared with that on the upper or middle slope.In addition,there was significant positive correlation between the index of potential sediment yield and sediment yields,that is,the greater potential of sediment yield meant the stronger sediment connectivity and thus the greater sediment yields.The results can provide scientific basis for the exploration of soil erosion mechanism and ecological benefits of vegetation,and further provide reference for ecological construction in the Loess Plateau.

Abstract:In order to further study the effect of vegetation measures on soil and water conservation under different rainfall regimes,this study takes the typical ecological restoration watershed in Danjiangkou reservoir area as the research object and adopts the slope runoff plot observation method,to study the effects of typical vegetation restoration measure on runoff coefficient,sediment concentration and soil erosion amount in the slope under different rainfall regimes based on the rainfall,runoff and sediment data monitored in situ of long term field taking bare land as the control.The response characteristics of soil and water conservation effects of vegetation measures to different rainfall regimes were analyzed.The results are as follows:(1) Rainfall regime Ⅲ characterized by medium-duration,medium-rainfall and low-intensity was the most common type in the study area,while short-duration,low-rainfall and high-intensity rainfall (Rainfall regime Ⅰ),and long-duration,high-rainfall and medium-intensity rainfall (Rainfall regime Ⅱ) occurred relatively infrequently.But the soil erosion caused by Rainfall regime Ⅰ was the most serious,accounting for more than 46.79% of the total erosion.Besides,the rainfall depth and maximum rainfall intensity of 30 min (I₃₀) were the key rainfall factors controlling soil erosion in the study area.(2) All vegetation measures had significant effects on soil and water conservation,and the benefits of runoff and sediment reduction were in the order of MS＞CF＞EJ.Compared to the bare land,MS decreased the runoff coefficient,sediment concentration and soil erosion by 54.07%,50.80% and 65.47%,respectively,while EJ reduced the runoff coefficient,sediment concentration and soil erosion by 30.60%,36.21% and 45.42%,respectively.The soil and water conservation effect of vegetation measures was the best under rainfall regime Ⅲ,with the best effect of MS,the reduction of soil erosion reached 87.98%;while it was slightly weaker under rainfall regime Ⅰ,among which the effect of CF was relatively better,with the reduction of erosion was 65.25%.Furthermore,the reduction benefit of runoff coefficient for vegetation measures gradually decreased with the increase of rainfall depth,the reduction benefit of sediment concentration decreased with the increase of I₃₀.The Medicago sativa measure had the better sediment reduction effect at I₃₀＜41 mm/h,while CF had the better sediment reduction effect at 68.8 mm/h＞I₃₀＞41 mm/h,but lower than 41.55%.The results have important guiding significance for soil and water conservation and sustainable utilization of resources in the Danjiangkou reservoir area.

Abstract:Selecting a suitable allowable sprinkler intensity is one of the important measures to avoid soil and water erosion under sprinkler irrigation conditions.Field experiments were conducted to determine the dynamic changes of soil crust thickness,surface soil bulk density and soil infiltration property with spraying duration under different sprinkler working pressures and nozzle diameters.The experimental treatments included two texture soils (loamy sand and silty clay loam),three sprinkler working pressures (103,138,and 172 kPa) and three nozzle diameters (3.97,5.95,and 7.94 mm).The results showed that the soil crust thickness and the bulk density of surface soil decreased with the increase of sprinkler pressure,while the steady soil infiltration rate increased.The greater the nozzle diameter was,the greater the soil crust thickness and the surface soil bulk density were,while the smaller the steady soil infiltration rate was.Soil crust thickness and surface bulk density increased significantly with the increase of spraying duration,while the steady soil infiltration rate decreased logarithmically.The specific power of spraying droplets was an optimal parameter to describe the impact of spraying kinetic energy on soil infiltration rate.The results provide a scientific basis for the determination of allowable sprinkler intensity.

Abstract:The study on soil infiltration characteristics and model adaptability under vegetation restoration can provide scientific basis for watershed ecological management and benefit evaluation.Taking Zhifanggou small watershed of Yanhe River as the study area,the field single-loop infiltration method and numerical simulation method were used to study the variation characteristics of water infiltration below the surface layer and below 20 cm soil of robinia pseudoacacia forest land,caragana korshinskii shrub land,secondary grassland and farmland under different restoration years,and the adaptability of four common infiltration models in the region was evaluated.The results showed that:(1) The infiltration process of soil below the surface layer of different vegetation restoration areas were significantly different in the infiltration and leakage stages,and the maximum difference was more than 4 times.The infiltration process below 20 cm was significantly different in the penetration stage after the infiltration stability,and the maximum difference was more than 5 times.(2) Different vegetation types and restoration years had significant effect on soil infiltration characteristics,showing the law of forest land > grassland > farmland as a whole.With the increase of restoration years,the infiltration capacity of caragana korshinskii land and secondary grassland increased,while the infiltration capacity of robinia pseudoacacia forest land decreased.(3) Philip equation,Kostiakov equation,Horton equation and Jiang Dingsheng equation all had good applicability to the soil water infiltration process in the region.Philip equation had the strongest applicability,and the determination coefficient R² could reach 0.931~0.985,the root mean square error RMSE was relatively minimum,which was in the range of 0.057~0.283,followed by Kostiakov equation,but Horton equation and Jiang Dingsheng equation had deviation in individual cases.In conclusion,vegetation restoration will significantly affect soil infiltration capacity and show different laws with the increase of restoration years.Among various infiltration models,Philip equation has the best applicability to the soil water infiltration process in this area.

Abstract:In order to explore the horizontal diffusion characteristics of different soil types of in the grassland open-pit mining area,three different soil types including undisturbed soil,mine accumulation soil and ecological transformation soil in Wujiata mining area of Yiqi,Ordos City and Inner Mongolia were taken as the objects.The soil texture,diffusion rate and water content were measured,and the infiltration characteristics of undisturbed soil,mine accumulation soil and ecological transformation soil were numerically simulated by HYDRUS-1D software,so as to analyze the influence of various factors on the soil infiltration law in mining area,and to explore the influence and variation law of horizontal diffusion process of different types of soil in grassland open-pit mine area.The results show that under the condition of one-dimensional horizontal infiltration movement,the wetting front migration distance and time curve of three different particle sizes of undisturbed soil,accumulated soil and ecologically modified soil show similar changes as a whole:with the increase of infiltration time,the wetting front migration distance increases rapidly at first and then slowly advances.Under the same soil type,the time required for the wetting front to reach the end of the soil column is inversely proportional to the soil depth:with the increase of soil depth,the time required decreases gradually,and the average diffusion rate is faster;under the same infiltration time,the wetting front migration distance is proportional to the soil depth:with the increase of soil depth,the wetting front migration distance also increases accordingly.The Boltzmann parameter λ decreased with the increase of soil moisture content,and the λ~θ relationship curve of each soil showed a decreasing trend with the increase of soil moisture content.When θ reaches a certain critical value,λ decreases sharply,and the critical values of θ in each soil layer of undisturbed soil,accumulation soil and modified soil are slightly different.The critical values of θ in each soil layer of undisturbed soil are 0.29,and those in each soil layer of accumulation soil are 0.24,0.28,0.30,respectively.However,the θ critical value in the ecological transformation soil except 60—90 cm is 0.31.The soil hydraulic parameters were inverted by HYDRUS-1D model combined with the change of water content in horizontal soil column profile.The changes of water content in three kinds of soil surface were simulated.The R² was greater than 0.91,The NSE was greater than 0.95,and the RMSE was less than 0.20.Using HYDRUS-1D model to invert soil hydraulic parameters to simulate the horizontal infiltration process of poor quality soil in mining area can better simulate the infiltration process,describe the dynamic changes of soil moisture in different land types in mining area,and provide reference for dynamic supervision and ecological management of soil moisture in mining area.

Abstract:In this study,the effects of Robinia pseudoacacia litter cover and roots on soil erosion was explored in the Loess Plateau.Five slope gradients (8.7%,17.6%,26.8%,36.4% and 46.6%) and three flow discharges (0.5,1.0 and 2.0 L/s) in vegetation covered with litter removal and bare slope plots,respectively,were used to investigated the effects of Robinia pseudoacacia litter cover and roots on soil erosion.The results indicated that litter cover and roots had significant effect on soil erosion,the reduction degree of soil erosion tended to be stable when the litter thickness was more than 3 cm and the root density was more than 0.5 kg/m³.Soil erosion amount of Robinia pseudoacacia was reduced by about 55% compared with the bare slope,and the contribution rate of litter cover and roots to soil erosion amount reduction was 66% and 34%,respectively.Moreover,the combination of litter cover and roots can reduce soil erodibility and increase soil critical shear stress,and consequently strengthen soil resistance capacity to erosion.Compared with the bare slope,soil erodibility was decreased by 80% and 66%,and soil critical shear stress was increased by 285% and 237%,respectively,in the plots with and without litter cover.These results provide a new idea for revealing the soil erosion mechanism of forest vegetation and have certain guiding significance for improving vegetation construction in the Loess Plateau.

Abstract:By setting vegetation survey transect along the increasing direction of groundwater table depth (GTD) in Yuxi River basin,and based on the data of vegetation coverage,GTD and soil water content,the spatial scale represented by vegetation coverage and its influencing factors was obtained by Multivariate Empirical Mode Decomposition (MEMD),the driving factors of vegetation coverage spatial distribution were analyzed by structural equation,then the spatial pattern change characteristics of natural restoration and succession of vegetation communities were divided combining cluster analysis.The results showed that:(1) MEMD decomposed the multivariate spatial data into three intrinsic mode functions.After Hilbert's transformation,the corresponding spatial scales of each modal part were 14,27,and 38 km,respectively.(2) The maximum represent scale correlation analysis of structural equation model and MEMD after decomposition showed that the GTD had a significant negative correlation with vegetation coverage at the whole transect scale (R²=-0.95,p<0.001);taking GTD 5 m as the cut-off point,the correlation between soil moisture content and vegetation coverage was significantly positive in the GTD less than 5 m (Path coefficient is 0.68,p < 0.001),and significantly negative in greater than 5 m (Path coefficient is-0.43,p<0.01).(3) On this basis,combined with the results of systematic clustering classification,vegetation coverage was divided into the core area (GTD 0~3 m),transition area (GTD 3~4 m),stability area (GTD 4~5 m),peripheral area (GTD 5~10 m) sand marginal area (GTD 10~15 m).The results showed that the response of vegetation coverage to subsurface water had multi-scale characteristics in space,which can provide scientific basis for ecological restoration of sandy land and the protection and utilization of groundwater resources.

Abstract:In order to explore the correlation mechanism between preferential flow and soil mechanics in the gully area of the dry-hot valley of Jinsha River and reveal the characteristics of soil shear strength under the influence of priority flow,to enrich the mechanism of gully erosion in the development area of hot and dry river valleys and provide theoretical basis for further gully erosion control in this area,the intact gully in the typical gully development area were selected as the study object,and based on staining tracer,soil physicochemical and intact soil straight shear experiments,the correlation between priority flow and soil mechanical indexes were analyzed by statistical methods such as RDA,and to clarify the relationship between preferential flow and shear strength.The results showed that:(1) Due to the development of ditch,the preferential flow development degree from the catchment area to the bottom of the ditch was gradually reduced.The soil moisture content,bulk density,total porosity and organic matter content in the preferential flow area were higher than that the matrix flow area,and the fractal dimension of mechanical composition in the matrix flow area (2.680~2.874) was greater than that in the preferential flow area (2.746~2.893).(2) The preferential flow area in the gully area affects the soil cohesion and strength,which will reduce the soil shear strength to a certain extent.The shear strength of the water catchment area and the trench head was greater than that of the ditch bed and the ditch bottom.The cohesive in the preferential flow region (1.24~2.65 kPa) was smaller than that in the matrix flow area region (1.91~4.27 kPa),the internal friction angle in the preferential flow region (19.52°~22.47°) was slightly larger than that in the matrix flow area region (17.68°~22.35°),and the shear strength of the preferential flow area region (36.66~43.68 kPa) was generally smaller than that of the matrix flow area region (38.74~47.32 kPa).(3) The preferential flow had different degree of correlation with soil cohesion and internal friction angle.Soil cohesion was significantly negatively correlated with dyeing area ratio and stroma flow depth,while internal friction angle was negatively correlated with the percentage of the preferential flow and dyeing area ratio of preferred flow area.The shear strength was inversely correlated with the ratio of staining surface,the maximum dyeing depth,the percentage of preferential flow and the dyeing area of the preferential flow area.

Abstract:The population surge and climate change have stressed regional ecological environment.The dynamic quantitative assessment of ecological environment quality can provide research support for the strategy development about regional ecological environment protection and civilization construction.The existing ecological quality assessment studies in Shaanxi Province are mostly based on the statistical data at the district and county scale,but there are generally problems such as small time span and difficulties to reveal the internal driving forces.MODIS data from 2001 to 2018 were used to calculate the remote sensing ecological index (RSEI) during the growing season in Shaanxi Province.Trend analysis,Hurst index method and partial correlation analysis were used to explore the spatio-temporal evolution of ecological quality and its response to climate and human activities in Shaanxi province from 2001 to 2018 at pixel scale.The results showed that:(1) The ecological quality of shaanxi province has been continuously improved in the past 20 years.The RSEI value increased at a rate of 0.34%/a,and the area with excellent ecological quality increased continuously.(2) The variation trend of RSEI was significant and the trend of obvious improvement is dominant.The overall spatial distribution pattern of RSEI is'high in the south and low in the north’,and the MK test (p<0.05) pixels accounted for 77.89%,66.75% of the pixels significantly improved,and mainly distributed in Yan'an City and Yulin City in northern Shaanxi Province,while significantly degraded pixels accounted for 11.08%,mainly distributed in Guanzhong Plain,Qinba Mountain and other places.Hurst index showed that the future trend of RSEI was mainly anti-persistence,46.04% of pixels would change from improvement to future degradation,and 29.33% of pixels would continue to improve.(3) RSEI was positively correlated with both air temperature and precipitation,and the influence of precipitation was greater than that of air temperature.The regions with negative correlation with human activities were concentrated in Xi'an urban agglomeration and central urban region of northern Shaanxi,and the correlations was significant (p<0.05),among the pixels,night light index (36.83%)> Precipitation (18.38%)> Temperature (7.65%).Among all land use conversion types,RSEI increased at the highest rate (0.84%/a) in the area of returning farmland to forest or grassland,while RSEI continued to decrease (0.23%/a) in the area of converting farmland to construction,reflecting the positive and negative correlation of human activities on ecological environment quality.The results fill the gap of long-term ecological environment dynamic monitoring in Shaanxi Province,and provide the basis for ecological governance and green development of the Yellow River basin.

Abstract:Using the remote sensing images and meteorological data of the Yunnan-Guizhou Plateau in 2000,2010 and 2018 and combining with the calculation method of ecosystem resilience,the ecosystem resilience of the Yunnan-Guizhou Plateau was calculated,the spatial and temporal distribution characteristics of the ecosystem resilience in 25 cities of the Yunnan-Guizhou Plateau were analyzed.,and the main influencing factors of its changes were also explored.The results showed that the ecosystem resilience of the Yunnan-Guizhou Plateau increased steadily from 2000 to 2018,indicating that the self-regulation and anti-disturbance capabilities of the ecosystem in this region were continuously enhanced.Spatially,the distribution of ecosystem resilience in the Yunnan-Guizhou Plateau was high in the southwest,low in the northwest,relatively lower in the middle,and relatively higher in the eastern.The ecosystem resilience was divided into four grades,among which the proportion of weak and medium grades showed a decreasing trend;the proportion of strong and very strong grades increased year by year.The driving factor analysis showed that rainfall and temperature were the main factors affecting the spatial distribution of ecosystem resilience.The results can provide a certain scientific basis for ecosystem protection in the Yunnan-Guizhou Plateau.

Abstract:By using the methods of trend analysis,correlation analysis and multiple linear regression,this paper systematically studied the temporal and spatial variation characteristics and the main driving factors of normalized vegetation index (NDVI) of different vegetation types changed in the establishment of Xarxili Nature Reserve before (1990—2005) and after (2006—2018).The results showed that:(1) At different altitude gradients,the annual mean of NDVI after the establishment of the nature reserve was higher than that before.(2) The trend of NDVI before and after the establishment of the NDVI was mainly increased.After the establishment of the reserve,the increasing trend of NDVI was 0.05 to 0.10/10 years,the number of pixels was significantly increased compared with that before the establishment.(3) The NDVI in most areas showed a significant negative correlation with air temperature and a significant positive correlation with precipitation (p＜0.05).(4) Temperature inhibited the growth of grassland at low altitude (500~1 500 m),precipitation promoted the growth of vegetation at middle altitude (1 500~2 000 m),and soil organic carbon and air temperature jointly drove the growth of vegetation at high altitude (2 000~3 000 m).

Abstract:To improve the accuracy of karst agricultural drought monitoring and further reveal its driving mechanism,a downscaling study of GLDAS soil moisture was conducted based on MODIS-NDVI/LST data using a geographically weighted regression model;agricultural drought was identified based on SSI,and the spatial and temporal evolution and joint probability characteristics of agricultural drought at different time scales were analyzed;finally,the driving mechanism of karst agricultural drought was revealed by geographic detector.The results showed that:(1) The drought intensity at different time scales in Guizhou Province showed an overall weakening trend over the 20-years period,and the drought area also showed a decreasing trend;the drought intensity and drought frequency showed a spatial distribution pattern of high in the west and low in the east.(2) The joint characteristic values of drought showed a pattern of autumn > winter > growing season > summer > year-round > spring,indicating that agricultural drought of higher intensity and larger area was prone to occur in autumn and winter in Guizhou Province.(3) Karst development intensity,rainfall and elevation were the main driving factors of agricultural drought in karst agriculture,and there was a strong coupling relationship with their spatial distribution;the interaction of different factors showed both two-way enhancement and non-linear enhancement of SSI,and there were few combinations without significant differences among factors,indicating that agricultural drought was the result of synergy among factors.The results can provide a reference basis for the monitoring of agricultural drought in karst agriculture and the formulation of drought prevention and anti-drought measures.

Abstract:Extreme precipitation events have important impacts on the sustainable development of ecological-water-resource-agricultural on the Qinghai-Tibet Plateau.Based on the daily precipitation datasets of General Circulation Models (GCMs) released by CMIP6(coupled model intercomparision project phase),the ability of GCMs to simulate the characteristics of historical extreme precipitation over the Qinghai-Tibet Plateau was systematically evaluated,and the future extreme precipitation was predicted.The results showed that multi-model ensemble (MME) exhibited a better performance of capturing spatio-temporal variation characteristics of extreme precipitation.Specifically,the variation trends of R95p,SDII,R1mm,CWD,and PRCP were consistent with those of observed values in different altitude zones,while the ability of CMIP6 MME to reproduce the variation trends of extreme precipitation indices decreased increasing altitude.The predicted extreme precipitation characteristics over the Qinghai-Tibet Plateau during the future near-term,mid-term,and long-term periods under different combination scenarios of shared socioeconomic pathways and the representative concentration pathways (SSP) were implemented.With the process of time and the increase of greenhouse gas emission concentration in the future period R95p,SDII,R1mm,CWD,and PRCP all showed a significantly increasing trend compared with the baseline period.While the most significant increase of SDII occurred in the southeast,the variation patterns of R95p,R1mm,CWD,and PRCP exhibited a relatively consistent spatial distribution characteristics of decreasing from northwest to southeast.The increase in extreme precipitation intensity is most significant in the southeast.In addition,the future variability of each extreme precipitation index compared to the base period showed the most remarkable variability in lower altitude regions (<2 000 m),with the maximum variability exceeding 200%.SDII showed a consistent increasing trend with rising elevation,and the relative changing rates of SDII under the SSP5-8.5 scenario were-0.06%,14.45%,and 17.95% at low (<3 500 m),middle (3 500~4 500 m),and high (>4 500 m) elevation zones,respectively,indicating that the increase of extreme precipitation intensity was more significant at higher elevations.

Abstract:Satellite precipitation products play a vital role in supporting hydrometeorological researches and runoff simulation in ungauged regions.However,the accuracy in satellite precipitation products might have an effect on streamflow simulation.A variety of statistical indicators and VIC models were adopted to assess the performance in the Yarlung Zangbo River basin and their hydrological application in Lhasa River basin for each of the five satellite precipitation products (Climate Prediction Center Morphing technique (CMORPH) satellite-gauge merged product (CMORPH-BLD),Global Satellite Mapping of Precipitation Gauge (GSMaP-Gauge),China Meteorological Forcing Dataset (CMFD),Multi-Source Weighted-Ensemble Precipitation (MSWEP),and Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Climate Data Record (PERSIANN-CDR)).Results showed that:(1) CMORPH-BLD and GSMaP-Gauge underestimated the observed data in the low rainfall season,while CMFD had a good agreement with the observed values in the low rainfall season.MSWEP and PERSIANN-CDR overestimated the observed data in the high rainfall season and low season.In terms of precipitation,CMORPH-BLD and CMFD were close to the gauge observations,whereas other datasets produced overestimation to varying degrees.(2) In daily comparison,all satellite products except CMFD produced a small linear correlation with the gauge observations (0.26~0.45),CMORPH-BLD and CMFD had a better agreement with the gauge observations,and the ability of CMFD and MSWEP had better skill than GSMaP-Gauge in detecting low precipitation events (0.1,0.5 and 1 mm/d).Satellite precipitation products were less capable of detecting intense precipitation (2,5 and 10 mm/d).The daily precipitation threshold of 2 mm/d was considered the point of change in the rate of the contingency statistics.(3) In monthly comparison,all the precipitation products had a strong linear correlation with CC values in the range of 0.73~0.99.The accuracy of CMFD and CMORPH-BLD was relatively high,while the other products were slightly lower.(4) CMFD hydrological simulation results were the best,followed by CMORPH-BLD.MSWEP produced satisfactory simulation results,while GSMaP-Gauge and PERSIANN-CDR performed poorly.CMFD and CMORPH-BLD could provide valuable precipitation estimates in hydrometeorological studies and runoff simulation in the Yarlung Zangbo River basin.The results have important implications in regarding hydrometeorological studies and water resource studies in the study area.

Abstract:There are few related studies on the evolution mechanism of water conservation function driven by landscape pattern in karst areas,and water conservation function is one of the key indicators of ecological benefits of ecological restoration projects such as the central of karst rocky desertification,which has important research significance.Taking the Yeji River Basin located in the center of the Southwest Karst as the research object,based on the InVEST model,partial least squares model (PLSR),landscape ecology theory,etc.,this paper explored the spatial and temporal variation of water conservation function and its coupling relationship with landscape pattern in the Yeji River Basin from 2005 to 2020.The results showed that:(1) The landscape types of the Yeji River Basin were mainly dryland,grassland and shrubbery,and the mutual transformation between each type is relatively frequent.The general characteristics were the conversion among dryland,shrubbery and grassland and the squeezing of construction land on other land types.(2) During the study period,dryland landscape tended to be fragmented,the construction land showed an agglomerative expansion trend,and other landscape types were relatively stable.In general,the landscape pattern showed a fragmented development trend,and the landscape connectivity showed a slight upward trend.(3) The interannual variation of water conservation in the study area showed a continuous growth trend,and the spatial distribution showed a trend of low in the middle and high in the north and south.The order of water conservation depth from high to low was shrub forest > forest land > sparse forest land > grassland > dryland > construction land > paddy fields > lakes > reservoirs and ponds.(4) The increase of landscape fragmentation and the improvement of patch quality could improve the water conservation function of karst basins,but the excessive degree of landscape fragmentation may lead to the decline of water conservation function.In general,during the study period,the landscape pattern of the Yeji River Basin showed a trend of fragmented development,and the water conservation function showed a continuous increasing trend.The impact of landscape pattern on the water conservation function was complex.The research results can provide important scientific basis for landscape planning and water resources protection in karst watershed.

Abstract:For improving plain irrigation efficiency of summer maize and optimize the allocation of agricultural resources in the Huang-Huai-Hai,based on the statistical data of 70 a of experiments at 27 plain site,the crop water requirement model,rainfall frequency analysis and crop coefficient,on the basis of relevant theories,the spatial and temporal distribution of water demand and water deficiency (i.e.water needed for supplementary irrigation) of summer corn in different hydrological years were analyzed.Firstly,according to the annual rainfall data of each representative point,four hydrological annual patterns with rainfall frequency of 25%,50%,75%,95% and their corresponding effective rainfall were determined by using the Pearson-Ⅲ curve.Secondly,the Penman-Monteith model was used to calculate the reference crop water requirement,and the crop coefficient approach was used to estimate the crop water requirement,and then the water requirement,water deficiency and irrigation demand indexes of summer maize under the four hydrological year patterns were obtained.Finally,interpolation analysis of each water demand factor of summer maize was carried out based on ArcMap10.7,and spatial and temporal distribution characteristics of water demand,water deficiency and irrigation demand index of summer maize in Huang-Huai-hai Plain were visually described.The results showed that from 1951 to 2020,the distribution of the high value area of summer maize water requirement in Huang-Huai-hai Plain was not affected by the annual variation of hydrological pattern,and mainly distributed in the central region of the plain with a zonal distribution.The distribution characteristics of water deficiency index and irrigation demand index were similar.The range of high value area increased with the increase of drought degree (hydrological year pattern changes from wet to drought),and mainly distributed in the north of central plain.The high-value area of effective rainfall was mainly concentrated in the southeast of the plain,and the overall distribution showed a decreasing trend from south to north.The water deficiency of summer maize in western Shandong,southern Hebei and northern Henan was high,so the aim of production should be to improve water use efficiency.Correspondingly,in southern Shandong,Northern Jiangsu and Anhui,the dependence of summer maize on irrigation was low,so the planting area of summer maize can be expanded appropriately and the yield should be taken as the target.

Abstract:In order to analyze the influence of vegetation cover on soil and water loss on the Loess Plateau slope and quantify the threshold of vegetation cover of soil erosion,the mechanism of vegetation cover on soil erosion was analyzed based on simulated rainfall data,and the observation data of field runoff plots in typical areas of the Loess Plateau such as Suide,Xifeng and Tianshui were used.The effectiveness of vegetation cover in controlling runoff and soil erosion under different cover types was discussed,and the lower threshold and upper threshold of vegetation cover in regulating runoff and preventing soil erosion under different cover types were determined.The results showed that:(1) The increases of vegetation coverage increased soil infiltration,reduced runoff,delayed runoff velocity,and increased soil resistance to erosion.(2) Slope runoff decreased with vegetation coverage as a power function or exponential function,and soil erosion decreased with vegetation coverage as an exponential function,power function or a logarithmic function.(3) In general,the lower threshold and upper threshold of soil erosion control by vegetation in different regions were 20%~30% and 50%~70% respectively.(4) Soil texture,vegetation type and even root characteristics of vegetation had important effects on the benefits of vegetation in controlling runoff and soil erosion.The results provide a research basis for soil and water conservation on the Loess Plateau.

Abstract:The Huangfuchuan River Basin was taken as the study area to explore the quantitative relationship between the sediment discharge reduction and rainfall variation,as well as soil and water conservation measures in tributaries of the middle Yellow River.Based on the data of daily precipitation at the Jungar meteorological station and annual runoff and sediment discharge at the Huangfu hydrological station from 1960 to 2015,the precipitation parameters affecting the annual runoff and sediment discharge in the Huangfuchuan River Basin were analyzed.Three typical periods of sediment discharge variation were Per1(1960-1986),Per2(1987-1999),Per3(2000-2015) using the double mass curve analysis and the Pettitt test,and the contribution rate of rainfall change,vegetation restoration and soil and water conservation measures to the variation in sediment discharge in different periods is calculated.The results showed that:(1) During the period of 1960-2015,the daily rainfall intensity exceeded 25mm/d reduced in Huangfuchuan River Basin,and the runoff and sediment discharge also displayed a decreasing trend (with the parameter Z＜0 and P<0.01 using the M—K trend tests);(2) Due to the change in the underlying surface caused by water and soil conservation measures,when the years with similar rainfall in Per3 and Per1 periods,the sediment discharge in these years in Per3 period was significantly reduced compared with that in Per1 period,with a reduction range of 50.2%~98.6%;(3) During the period of 1987-1999,the contribution rates of vegetation restoration and soil and water conservation measures to the reduction of sediment discharge were 73.0% and 38.4%,respectively.during the period of 2000-2015,the contribution rates of rainfall change,vegetation restoration and soil and water conservation measures were 11.5%,69.8% and 18.7%,respectively.The results of this study quantitatively calculate the contribution rate of rainfall variation and soil and water conservation measures to the reduction of sediment discharge in the Huangfuchuan River Basin,which is helpful to identify the causes for the sharp reduction of sediment discharge in the middle Yellow River.

Abstract:In order to optimize the drip irrigation technical parameters of winter wheat under drip irrigation in northern Henan province,the effects of different dripper discharges (2.0,4.0,6.0 L/h) and the spacing of drip irrigation lateral springs (40,60,80,100,120 cm) on soil distribution of irrigation water,winter wheat yield and water use efficiency were studied in a field experiment.The result showed that:In terms of the drip irrigation uniformity,reducing the distance between drip irrigation lateral spacing and increasing the dripper discharge could improve the distribution uniformity of irrigation water in the root zone of winter wheat.Under the experimental conditions in this study,the yield and composition of winter wheat were affected by the spread of drip irrigation lateral spacing over 80 cm,and the yield of winter wheat increased with the increase of the dripper discharge with the same drip irrigation lateral spacing.In terms of water use efficiency,the appropriate combination of drip irrigation lateral spacing and dripper discharge could effectively reduce water consumption and improve water use efficiency under the same irrigation condition.The present results suggested that the parameter combination of drip irrigation lateral spacing of 60 cm and dripper discharge 2.0 L/h had the highest yield (10 626.45 kg/hm²) and the highest water use efficiency (2.42 kg/m³).Through the comprehensive analysis of irrigation water uniformity,winter wheat yield and water use efficiency,the parameter combination of 60 cm drip irrigation lateral spacing,dripper discharge 2.0 L/h,80 cm drip irrigation lateral spacing,and dripper discharge 6.0 L/h were the optimal technical parameters for winter wheat drip irrigation.

Abstract:In order to explore the suitable water-heat regulation method for the orchard and farmland intercropping system in the loess area,the typical apple (Malus pumila)-soybean (Glycine max) intercropping system in this area was selected as the object.The effects of different water-heat regulation methods on water consumption,soil temperature and root distribution of the intercropping system were analyzed.Three upper limits of irrigation amount were set:50%(W1),65%(W2) and 80%(W3) of the field water capacity,and two mulching periods:soybean sowing to podding stage (M1) and whole growth period (M2).The results showed that the water consumption of the irrigation treatment was positively correlated with the irrigation amount,and its water consumption was increased by 1.02%~79.11% compared with the control.The soil temperature increased first and then decreased with the increase of soil depth at branching and podding stages,and the maximum value appeared at 15 cm,while it showed a decreasing trend at filling stage.The soil temperature was increased by 1.13~3.09℃ in the early stage of growth though mulching,and decreased by 0.05~2.36℃ in the late growth stage.In the intercropping system,the crop roots were mainly distributed in the vertical directions of 0-80 cm depth and the horizontal directions of 0.3~1.8 m away from the tree row.The soil effective accumulated temperature and root competition intensity generally increased first and then decreased with the increase of irrigation amount,and the maximum value appeared in W2.The root competition intensity of M1 group was 12.69% higher than M2.Correlation analysis showed that there was a significantly negative correlation between soil moisture and root.Moderate level of irrigation combined with film mulching from sowing to podding stage could maximize root density and improve soil physical properties.Therefore,it is recommended that half-growth mulch (M1) combined with 65% of field water capacity should be used as the upper irrigation limit (W2) in young apple-soybean intercropping systems.

Abstract:To clarify the influence of different sand-soil mixtures on the soil evaporation process,on the basis of soil evaporation theory and micro-lysimeter field experiment,the dynamic changes characteristics of soil evaporation intensity and its action mechanism under six mixed sand-soil mulching patterns (1.0,0.8,0.6,0.4,0.2,0,denoted by M1~M6,respectively) were deeply explored.The results showed that the theoretical simulation of soil evaporation could realistically reflect the soil water evaporation under the mixed cover of sand and soil,and its cumulative evaporation could be quantitatively expressed by the mixing volume ratio of sand and soil evaporation time.There were only two prominent evaporation stages with significant evaporation inhibition when the the sand mixing ratio increased to above 0.8.When the mixing volume ratio of sand was decreased to below 0.5,the peak of soil evaporation stability stage under M3~M6 treatment had been concentrated in the first 2.53~2.66 d,and the main moisture dissipation duration was increased by 6.49,6.49,6.49 and 7.09 d compared with M1,respectively.However,when the sand mixing volume ration was between 0.5 and 0.8,the mulch layer was easily induced and could form the dense mulch dry layer earlier,while the overall moisture conservation effect was prominent instead.Under the influence of soil evaporation stage characteristics and mulching patterns,the supply of underlying net radiation flux mainly limited the first evaporation stage.In the second and third evaporation stages of evaporation,the role of sand layer structure came to the fore,and the regulating function of soil hydraulic properties gradually prevailed.In summary,the deterioration of sand layer structure would accelerate the soil evaporation process and intensify the ineffective water loss of farmland.When the mixing volume ration of sand was less than 0.5,the effect of evaporation and soil moisture retention would gradually lose,which has practical significance for revealing the degradation mechanism of gravel-sand mulched fields and its sustainable and healthy development in Northwest arid region.

Abstract:In order to clarify the effects of tillage methods on soil pore structure and soil water movement characteristics during agricultural production,sugarcane field in Guangxi was taken as the research object,soil pore structure characteristics of sugarcane field under two typical tillage methods of no-tillage and ridge tillage were studied based on soil slicing technique,combined with simulated infiltration test of soil column,the influence of soil pore structure on soil water movement was explored,and the interaction between pore structure and soil water movement characteristics was further revealed.The results showed that with the increase of soil layer depth,the pore morphology of no-till sugarcane field was dominated by aggregated clumps,while the pore morphology of ridge tillage sugarcane field was dominated by strip distribution.Compared with no-till sugarcane field,the total porosity and porosity of the soil with > 2.5 mm pore size increased by 32.5% and 21.9%,respectively,in ridge tillage sugarcane field.In the range of local soil depth,the ridge cultivated land significantly increased the porosity variation of the upper and lower soil layers (p<0.05),and significantly decreased the connectivity of soil pores (average proximity index was 0.448)(p<0.05),the soil pore morphology was relatively regular (average pore roundness was 0.335).As for the soil water movement characteristics,compared with the ridge tillage sugarcane field,the overall soil saturated hydraulic conductivity and mass flow rate in no-till sugarcane field were significantly higher (p<0.05),while the initial water content was significantly lower (p<0.05).The change intensity of mass flow rate over time was relatively large,which improved the water infiltration capacity.Compared with no-tillage,the ridge tillage of sugarcane field reduced the connectivity of soil pore structure and resulted in water separation and storage in the surface soil,thus could reduce the infiltration of soil water to a certain extent,which was helpful to improve the soil water condition of sugarcane field.

Abstract:In order to explore the feasibility of supplementing soil water and groundwater by using rainfall and flood resources in flood season,the experiment was carried out in maize field plots from June to October 2020,monitoring the characteristics of soil water dynamic changes under one-time deep storage irrigation with different planned water storage depths (T1:H_p=60 cm;T2:H_p=90 cm;T3:H_p=120 cm;T4:H_p=150 cm;T5:H_p=180 cm) and saturated water content as the upper limit of irrigation,and studying the quantitative farmland water dynamics of groundwater replenishment,so as to provide the basis for formulating the deep storage irrigation system for effectively replenishing soil water storage.The results showed that deep storage irrigation could effectively replenish the farmland soil moisture.After 10 days of irrigation,the average water content of 0—200 cm soil layer of each treatment increased by 11.90%~40.85%,and the water content of T5 treatment had the highest water content increase.With the increase of the planned water storage depths,evapotranspiration of summer maize farmland increased first,then decreased,and finally rose to the highest level,and the treatment reached the maximum in the 90 cm planned wetting layer.When the planned water storage depths were 60 cm and 90 cm,the supplementary water was mainly used to recharge shallow soil and farmland evapotranspiration,which was not conducive to soil water storage.When the planned water storage depths were more than 120 cm,the water supply of deep soil by irrigation and rainfall was more than 243.39 mm,accounting for more than 27.29% of the total water supply.In conclusion,deep storage irrigation was an effective irrigation method to replenish soil water,and selecting the planned water storage depths above 120 cm for deep storage irrigation could effectively optimize the water resources allocation and replenish shallow soil water storage and even groundwater.

Abstract:In view of the difference of soil water and solute migration between transverse ridge planting and along-slope ridge planting modes in sloping farmland,a field simulation experiment was conducted to monitor soil water distribution and Br-concentrations distribution in different ridge planting modes,including ridge beds,ridge sides and furrows,taking the soybean sloping land with a slope of 7° as the research object and Br-as the tracer.To explore the effects of transverse and along-slope ridge planting modes on soil water migration and soluble nutrient distribution in sloping farmland.The results showed that the maximum soil water content of the two modes was distributed between the 10—20 cm soil layer in transverse ridge cropping and between the 5—15 cm soil layer in the along-slope ridge planting mode,which proved the effect of transverse ridge planting mode on rainwater storage.The maximum soil water storage was found in the ridge side on the upper side of the ridge under the transverse ridge planting mode,and that in the ridge and furrow under along-slope ridge planting mode.The variation coefficient of soil volumetric water content in each soil layer under different ridge planting patterns was larger in the range of 0—5 cm,50—60 cm,and was between 8.97 and 11.90.The variation coefficient of soil volumetric water content in the middle layer was smaller,and fluctuated between 0.91 and 8.76.The Br-ions migration along the slope direction was obvious in the soil layer of 20—60 cm under the ridge planting along the slope,while Br-ions migration occurred in the soil layer of 40—60 cm under the ridge planting on the transverse slope.The ratio of soil Br-ions total amount in the ridge of the furrow and the lower part of the slope (transverse ridge planting:side of the ridge;along-slope ridge planting:among the plant) was 3∶7 in the two ridge cultivation modes.The total amount of Br-ions in the center of ridge bed under the along-slope ridge planting modes was only 54.33% of that under transverse ridge planting mode,which could reduce the migration of Br-ions in soil along the slope.Based on the results of this study,it can be concluded that applying non-absorbable nutrients on the ridge side can reduce their migration and loss,which is beneficial to improve the utilization efficiency of nutrients by crops.

Abstract:Soil soluble carbon is the most active part of soil organic carbon pool,which is often used as a sensitive indicator for the initial change of soil carbon turnover,but its content is jointly regulated by plant litter input,forest type,and seasonal variation of water and heat.The monthly dynamics of soil dissolved organic carbon (DOC) and hot water-soluble carbon (HWSC) contents and their responses to litter input during the growing season were analyzed by carrying out a field situ incubation experiment of two plantations (Castanopsis carlesii and Cunninghamia lanceolata/Chinese fir) in subtropical China.The results showed that litter input,forest type and monthly climate significantly affected the content of soil soluble carbon components (p＜0.001).Soil DOC and HWSC contents in Chinese fir plantation were higher than those of Castanopsis carlesii plantation by 15.09% and 13.06%,respectively,but the degree of aromatation of soil soluble organic matter was higher in Castanopsis carlesii plantation.After one growing season of incubation,soil DOC and HWSC contents increased significantly in both plantations.Litter increased soil DOC and HWSC contents in Castanopsis carlesii plantation during the growing season,but which in Chinese fir plantation displayed seasonal difference.These results indicated that soil DOC and HWSC contents were higher in Chinese fir plantation than Castanopsis carlesii plantation,but litter could promoted the DOC and HWSC contents of Castanopsis carlesii plantation,which would be easy to be lost during leaching.

Abstract:In view of the problems of poor soil structure,low fertility and low plant productivity after ammonia nitrogen reduction in abandoned rare earth mining areas,soil improvement becomes the key to rapidly improve vegetation restoration.Field experiments were carried out to compare the effects of single application of different concentrations superabsorbent polymers (SAPs:S1,S2 and S3) and water and fertilizer preserving materials (WFPMs:F1,F2,F3) on soil physicochemical properties,growth of Pennisetum sinese Roxb,evapotranspiration and water use efficiency (WUE).In order to select the best soil amendment,the principal component analysis and fuzzy membership function were employed to comprehensively evaluate the relevant indicators.The results showed that:(1) The WFPMs promoted the growth of Pennisetum sinese Roxb by improving the soil physicochemical properties of the tailings soil in the abandoned rare earth mining area.The relationship between soil physicochemical properties and plant growth showed that the higher the soil pH and nutrient content,the higher the growth indicators such as tiller number,nitrogen and phosphorus content,yield and WUE.(2) Compared with the control,the WFPMs increased the plant yield and WUE by 58.13%~182.63% and 53.81%~181.54%,respectively;The effect of SAPs was limited,and its medium and high dosage of water retaining agent (S2,S3) increased the plant yield and WUE by 19.95%~77.52% and 19.54%~79.50%,respectively.(3) The principal component analysis method was used to screen out 22 soil improvement indicators,and the fuzzy membership function values of each indicator were calculated respectively.The average function value was taken as the evaluation value of soil improvement effect,and the evaluation result was as follows:WFPMs ＞ SAPs (except for S1)＞ CK.Compared with the control,the average function value of the SAPs (except for S1) only increased by 0.32~0.35 times,while that of the WFPMs increased by 0.73~1.72 times,and decreased with the increase of the application amount.Therefore,F1 was the best soil amendment treatment.The result showed that combing materials of WFPMs have a good application effect on the improvement of tailings soil in abandoned rare earth mining area.

Abstract:In order to explore the effects of tillage combined with straw mulching on soil water storage,crop water consumption characteristics and yield formation of upland potato growth period in different precipitation year types,the field experiment was conducted by setting different tillage methods (no-tillage,subsoiling,and ploughing tillage) combined with straw mulching after autumn crop harvest in dryland area for three consecutive years.The results showed that after three years of tillage and mulching treatment,no-tillage,subsoiling combined with straw mulching could significantly reduce soil bulk density and increase soil organic matter content in 0-40 cm layer.Conservation tillage combined with straw mulching could significantly improve soil water storage in 0-200 cm soil layer during potato growth period.The soil water storage in subsoiling with straw mulching treatment was the highest in the whole potato growth period in the relative less water year and the less water year,which was significantly increased by 15.80% and 20.80% than that of ploughing tillage without mulching,respectively.In the normal year,no tillage with straw mulching treatment was the highest,which was significantly increased by 14.78% than that of ploughing tillage without mulching.Among them,subsoiling with straw mulching treatment had the best soil water storage effect in 0—60 cm soil layer in early growth stage and 120—200 cm soil layer in middle growth stage of the relative less water year,20—100 cm soil layer in early normal year and 0—80 cm soil layer in growth stage of the relative less water year.Subsoiling or no-tillage with straw mulching treatment could significantly reduce the water consumption,water consumption modulus coefficient and water consumption intensity at the early stage of potato and significantly increase the water consumption,water consumption modulus coefficient and water consumption intensity at the middle and late stages of potato especially in the less water year.Compared with ploughing tillage without mulching,subsoiling with straw mulching was more conducive to the increase of dry matter mass of potato,especially in the middle growth stage of less water years and in the middle and late growth stages of normal years.In the relative less water year,potato yield and water use efficiency of no tillage with straw mulching treatment were the best,which were significantly increased by 51.82% and 50.52% than that of ploughing tillage without mulching respectively.In the normal year and the less water year,the effect of subsoiling with straw mulching treatment was the best,which were significantly increased by 36.69% and 29.48% than that of ploughing tillage without mulching in the normal year,and significantly increased by 87.46% and 62.31% respectively in the less water year.Subsoiling with straw mulching treatment had the best effect on increasing the commodity rate of potato in the relative less water year and the normal year,and no tillage with straw mulching treatment had the best effect on increasing the commodity rate of potato in the less water year,which was significantly increased by 12.88%,14.58% and 26.18%,respectively,compared with ploughing tillage without mulching.Correlation analysis showed that soil bulk density and organic matter content increased under the tillage with straw mulching,which improved soil water retention performance and the potato yield.The soil moisture characteristics played a crucial role in improving potato yield during the growth period of potato under different precipitation years,especially in the middle and late growth period of potato in relative less water years,soil moisture was significantly or extremely significantly positively correlated with the yield.It could be seen that no-tillage or subsoiling combined with straw mulching could improve the soil moisture status during potato growth period,regulate crop water consumption and increase the dry matter accumulation,which was beneficial to improve the potato yield and water use efficiency,and the subsoiling with straw mulching has the best effect.

Abstract:In order to reveal the influence of different rocky desertification restoration modes on soil structure and physicochemical properties after 20 years of afforestation,the distribution characteristics of soil physicochemical properties under seven rocky desertification restoration modes in central Yunnan Province were studied and multi-index clustering were conducted.The results showed that,except for Keteleeria fortunei,the soil nutrient grade of the other plots were medium and high level;the soil particle composition was more reasonable,the degree of fractal was better,and the resistance to erosion was stronger.The different types of vegetation restoration had obviously different effects on the improvement of rocky desertification soils,and mixed forests were significantly better than pure forests.Due to the influences of soil parent material,topography,and hydrology,there were differences among the same restoration types,the Pinus armandii Franch.and Keteleeria fortunei;were generally poor.The soil erodibility factor K in the study area was characterized by positive variation in relation to the content of powder particles.The Q-clustering of soil physicochemical properties could classify the sample soils into four categories,and Keteleeria fortunei and Pinus armandii Franch.were separated out separately.The results of this research could provide theoretical basis and technical support for the local government to formulate scientific and reasonable ecological prevention and control measures of karst rocky desertification.

Abstract:To understand the response of carbon (C),nitrogen (N) and phosphorus (P) stoichiometric characteristics of the new branches and leaves in natural Pinus tabulaeformis forest to changes in soil nitrogen concentration and differentstand age,and to reveal the response of N and P homeostasis in the new branches and leaves of Pinus tabuliformis at different stand ages to short-term nitrogen addition,taking the natural secondary forest of Pinus tabulaeformis with age V~VII of Xiaowen mountain forest farm in Guandi mountain forest area as the research object,the field in-situ comparative test with different nitrogen application rates was used to set four nitrogen application levels:control (N0,0),low nitrogen (N1,5 g/m²),medium nitrogen (N2,10 g/m²) and high nitrogen (N3,15 g/m²),and the contents of C,N and P in new branches and leaves and their stoichiometric ratios and homeostasis indexes were analyzed under different soil nitrogen concentrations.The contents of C,N and P in the branches and leaves of Pinus tabulaeformis increased significantly with the increase of soil nitrogen concentration,while the contents of C/N and C/P decreased;the contents of C,C/N and C/P in the branches and leaves of Pinus tabulaeformis increased with the increase of forest age,while the contents of N and P decreased with the increase of forest age;according to leaf N/P,the growth of Pinus tabulaeformis in this area was mainly limited by N;the relationship between N,P and N/P in new shoots and leaves with corresponding soil parameters could be adequately simulated by an internal homeostasis model (p＜0.1),the content of P in new shoots was sensitive to the change of soil nitrogen supply level,while the other indexes were stable,and the homeostasis of new leaves was higher than that of new shoots.The Pinus tabulaeformis maintained the internal stability of new branches and leaves by adjusting nitrogen and phosphorus uptake and utilization strategies to adapt to the increase of soil nitrogen concentration and the resulting changes.

Abstract:Global warming has increased the frequency and intensity of cold waves,which changes soil respiration and its components,but studies on the effects of warming and cold waves on soil respiration and its components in subtropical forests are still scarce.Soil respiration was separated by trench method,and the effects of warming on total soil respiration,root respiration and microbial respiration in a subtropical evergreen broad-leaved natural forest during a cold wave were studied by using a soil respiration high-frequency automated observation system.The results showed that:(1) When the cold wave occurred,total soil respiration rate was decreased significantly by 45.93% and 25.68%,and the soil microbial respiration rate was decreased significantly by 51.25% and 35.54% in the control and warming treatments during the cold wave,respectively.However,the cold wave did not affect the root respiration rate in the warming treatment,while the root respiration rate in the control treatment was significantly decreased by 39.72% during the cold wave.(2) Soil warming changed diel patterns of total soil respiration and root respiration during the observation period,with the warming causing the daily peak of total soil respiration and root respiration to occur 1 and 2 h earlier,but the daily peaks of total soil respiration and root respiration were synchronized between the control and warming treatments when the cold wave occurred.(3) The temperature sensitivity (Q₁₀) of total soil respiration,root respiration and microbial respiration was reduced after soil warming during the observation period,respectively,while the Q₁₀ of root respiration was higher than that of microbial respiration.Thus,to accurately understand the changes of total soil respiration,root respiration and microbial respiration and their response to soil warming under extreme weather such as a cold wave is important to improve the prediction accuracy of soil carbon emissions after climate warming.

Abstract:To investigate the response of transpiration characteristics of Betula platyphylla secondary forest to influencing factors in permafrost area,and to provide scientific reference for accurate assessment of the hydrological effects of forest ecosystems in this region.The sap flow of Betula platyphylla was measured using thermal dissipation probes from May to September 2021 in permafrost area,and the influence factors were observed simultaneously.The results showed that the stand transpiration of Betula platyphylla secondary forest showed obvious hourly,daily and monthly changes during the study period.(1) The hourly transpiration characteristics of Betula platyphylla secondary forest was exhibited that dominant trees > intermediate trees > suppressed trees.Furthermore,diurnal variations of daily transpiration performed a single peak curve pattern in sunny days,while the bimodal curve was observed in rainy days.Meanwhile,the daily mean stand transpiration of Betula platyphylla secondary forest was 1.47 mm/d,with the maximum value appeared in July.A significant monthly variation of transpiration was found during the whole observation period and ranked as follows:July > June > August > September > May,which was 65.08,62.43,54.27,22.92 and 19.84 mm,respectively.(2) The cumulative transpiration of the stand was 224.54 mm,accounting for 32.41% of the total precipitation over the same period,and the transpiration of the dominant trees was the main contributors to the stand transpiration,accounting for 62.64% of the stand transpiration.(3) At the hourly scale,transpiration was mainly affected by air temperature and vapor pressure deficit.At the daily scale,transpiration was positively correlation with potential evapotranspiration,air temperature,solar radiation,vapor pressure deficit,leaf area index and soil temperature (p<0.01),which was significant negative correlation with air relative humidity (p<0.01) and no significant correlation with soil water content (p>0.05),and potential evapotranspiration,leaf area index,vapor pressure deficit and air temperature were the main factors driving the daily stand transpiration.At the monthly scale,air temperature had the greatest impact on stand transpiration,which explained 93.90% of stand transpiration.

Abstract:It is unclear whether the soil carbon sequestration capacity of plantation forests can reach the level of natural forests,especially under the declining area of natural forests and increasing the area of plantation forests on a global scale.Taking planted and natural Pinus tabuliformis forests in the Ziwuling Forest Region of Loess Plateau as the research object,the distribution characteristics and correlations of soil aggregate composition,soil organic carbon (SOC),different degrees of labile SOC and Glomalin-related soil protein (GRSP) in 0—20 cm soil layer of different density plantations and natural forests were compared and analyzed.The results showed that:(1) The total SOC content and the content of its composition:very-labile,less-labile,and non-labile SOC in the whole soil of the plantations were significantly lower than those in the natural forests.The total SOC and non-labile SOC contents increased with increasing stand density,while the less-labile SOC content was the opposite.(2) The total SOC and its component contents of each particle size aggregates in the plantations were significantly lower than those in the natural forests.With increasing stand density,the weight percentage of macroaggregates,total SOC content and non-labile SOC content of macroaggregates of plantation forests increased,but were significantly lower than those of natural forests.(3) The SOC content of the plantations increased with the increase of stand density,and its peak value was 17.95 g/kg,which was 65.5% of the SOC content of the natural forests.Among them,the number of macroaggregates and their SOC content was significantly reduced,which was the main reason for the difference.The percentage of labile SOC was negatively correlated with the increase of total SOC content,GRSP increased with the increase of stand density but was lower than that of natural forest,and the total SOC content was increased by increasing the number of macroaggregates.Increasing the plantation stand density can improve its soil carbon sequestration capacity by increasing surface soil biomass,the number of soil macroaggregates,and the GRSP content,and reducing the percentage of labile SOC,but significantly reduces the plant diversity of the plantations.

Abstract:It is a key problem to balance the water demand of shelterbelt and farmland crops reasonably in the construction of shelterbelts forest network system in Hetao irrigation district due to the arid climate conditions.In order to study the influence of typical farmland shelterbelts on the water source of farmland crops in Hetao irrigation district,three typical shelterbelt systems in Hetao irrigation district were selected,and the soil moisture content,hydrogen and oxygen isotope values of soil and crop stem water at 0.3 H,0.4 H,0.6 H and 2 H away from the edge of nearby farmland were measured and analyzed.The results showed that:(1) From July to September,the soil moisture contents of all farmland plots were generally low.The soil moisture contents of 4 and 5 row plots at the near end of forest were lower than that at the far end of forest,and there was no significant difference in the soil moisture content of the 8 row plots.(2) The hydrogen and oxygen isotopes of soil water in all plots were depleted with the increase of soil depth as a whole.Among them,the 40—60 cm soil layer at 0.4~0.6 H away from the edge of farmland in the 8 row plots showed greater isotope enrichment.(3) The soil water of 40—80 cm soil layer was mainly used for maize at 0.3~0.4 H away from the edge of farmland in the 4 row plots,and the soil water of 0—40 cm soil layer was used for maize at 0.6~2.0 H.The soil water of 20—60 cm soil layer was used for maize at 0.3 H and the soi lwater of 0—60 cm soil layer was used for maize at 0.4~2.0 H in row 5 plots.The maize in row 8 at 0.3 H and 2 H mainly used soil water in 0—40 cm soil layer,while the maize at 0.4~0.6 H mainly used more soil water in 20—80 cm soil layer.According to the study,the shelter forest with 8 row configuration had a wider impact on the water use range of farmland crops,while the influence range of 4 and 5 row of shelterbelts on the growth water of farmland crops was smaller on the premise of not affecting the protection effect.The results can provide theoretical reference for the rational allocation of farmland shelterbelt system.

Abstract:Based on 13 years of long-term positioning experiment,and the split plot design was adopted.The main treatment was the roots of grass coverage and clearing,The secondary treatment was four fertilizer treatments,including no fertilizer (CK),single application of organic fertilizer (M),combined application of nitrogen,phosphorus and potassium (NPK) and combined application of organic and inorganic fertilizer (MNPK).The modified Hedley phosphorus classification method was used for extraction and determination of various phosphorus forms.The results showed that the contents of various phosphorus forms in 0—20 cm and 20—40 cm layers of calcareous soil were mainly D.HCl—P and residue—P,and the ratio of water-soluble phosphorus (H₂O—P) to inorganic phosphorus sources of sodium bicarbonate (NaHCO₃—Pi) was low.After 13 years of grass mulching and different fertilization treatments,the combined application of organic and inorganic fertilizers under grass mulching conditions increased the content and proportion of inorganic phosphorus in soil,and the content and proportion of residual phosphorus in 0—20 cm and 20—40 cm soil layers reduced from 68.5% and 66.1% to 75.8% and 69.7%,respectively,the proportion of residual phosphorus decreased from 26.8% and 27.0% to 18.3% and 23.5%,respectively.The combined application of organic and inorganic fertilizers under grass mulch could significantly increase the contents of available P and inorganic P in soil and the proportion of H₂O—P and NaHCO₃—Pi active P in soil.The combined application of organic and inorganic fertilizers under grass mulch could increase the content of active P in soil and maintain a high proportion of available P pool,which was an important measure to improve the utilization rate of P fertilizer in apple orchard.It is very important to ensure the high yield of apple and the efficient utilization of phosphorus fertilizer resources in this area.

Abstract:In order to investigate the effects of long-term application of blended controlled-release urea (CRF) on soil enzyme activities and nutrient status under straw returning condition to the field,soil samples ranging from 0 to 20 cm were collected from the field experiment of long-term positioning fertilization since 2008 at the rejuvenation stage,flag stage,filling stage and maturity stages of wheat in 2021.Without fertilized nitrogen as a control,the effects of CRF and normal urea (BBF),and four application levels that no nitrogen application (N 0 kg/hm²),reduced nitrogen application (N 120 kg/hm²,N1),conventional nitrogen application (N 240 kg/hm²,N2) and increased nitrogen application (N 360 kg/hm²,N3) on soil enzyme activities and soil nutrients in wheat season were studied under straw returning,and the correlation analysis of the indexes was conducted.The results showed that under the same nitrogen application level,soil sucrase activity and cellulase activity were increased by 9.6%~21.0% and 9.0%~31.5% under CRF treatment compared with BBF treatment,respectively.The soil nitrate nitrogen content in CRF treatment was significantly higher than that in BBF treatment at the rejuvenation and maturity stages of wheat,increasing by 23.2%~145.0%.At the rejuvenation stage,the soil NH₄⁺—N content under CRF2 treatment was significantly increased by 148.0% compared with that in BBF2 treatment.At maturity stage,the content of ammonium nitrogn in soil under CRF treatments was significantly higher than that of BBF treatments at all nitrogen application levels.Compared with BBF1 and BBF2,CRF1 and CRF2 treatments increased wheat grain yield by 9.8% and 12.4%,respectively.Soil urease and catalase activities were significantly positively correlated with the contents of soil total nitrogen,organic matter and nitrate nitrogen,while catalase and cellulase activities were significantly negatively correlated with phosphorus and available potassium contents.Straw returning combined with CRF increased soil enzyme activities at the middle and late growth stages of wheat compared with BBF,and was more conducive to the supply of available nitrogen at the early and late growth stages of wheat.Long-term application of straw returning combined with CRF significantly increased soil organic matter content,improved soil fertility retention and buffering,and improved soil fertility.Among them,the optimal treatment was CRF with conventional fertilizer application rate.

Abstract:The semi-arid (Yanchi,Ningxia) and arid (Urad Rear Banner,Inner Mongolia) desert steppe areas were selected as the research sites,and the Lespedeza potaninii litter was taken as the research object.The mesh decomposition bag method was used to study the effects of soil arthropod decomposition function on the distribution of litter C,N,P and K.Combined with the distribution characteristics of soil organic carbon (SOC),total nitrogen (TN),total phosphorus (TP) and total potassium (TK) in the process of litter decomposition,the influence of soil arthropod decomposition on the distribution of soil nutrient elements was clarified.The results showed:(1) A total of 226 soil arthropods belonging to 14 families (genera) were captured.The individual density of soil arthropods in Yanchi was higher than that in Urat,while there was little difference in species richness,which was higher in shrub canopy than bare soil only in Urat.The Simpson,Shannon and Margalef index of soil arthropods showed no significant differences in different habitats,while Pielou index in bare soil was significantly higher in Urat than in Yanchi.(2) The nutrient elements of litter in different mesh decomposition bags were released in different degrees.The cumulative coefficients of C and N in litter were significantly lower in the 2 mm mesh than in the 0.01 mm mesh in Yanchi,and significantly higher in the 2 mm mesh than in the 0.01 mm mesh in Urat.The accumulation coefficients of P and K in litter were significantly higher in the 2 mm mesh than in the 0.01 mm mesh in Urat and Yanchi,respectively,and soil arthropods showed positive effects on the release of C,N,P and K from litter in Yanchi;the release of C and N from litter in Urat showed a negative effect in shrub canopy and a positive effect in bare soil,the release of P and K from litter showed a positive effect in shrub canopy and a negative effect in bare soil.(3) The increment of TN and TK by soil arthropods was affected by the difference of microhabitats between inner and outer shrub,which showed that the increment of TN and TK in Urat shrub canopy was significantly higher than that of bare soil.Soil arthropods had positive effects on soil SOC increment;the increments of TK and TP had positive effect in shrub canopy and negative effect in bare soil;the effect on TN increment was different in different regions and different microhabitats.(4) Pearson correlation analysis and RDA analysis showed that the distribution of soil arthropods diversity and soil physical and chemical properties significantly affected the nutrient release of litter.Comprehensive analysis showed that soil arthropods accelerated litter nutrient release and soil SOC accumulation in semi-arid areas,while the accumulation of soil TP,TN,and TK in soil was affected by shrub microhabitats.In arid areas,soil arthropods had opposite effects on litter C,N and P,K release in shrub canopy and bare soil microhabitats,and soil arthropods accelerated the nutrients input in shrub canopy and slowed down the nutrients input in bare soil.Soil arthropods enhanced the mobility of litter nutrient elements in the ecosystem,changed the direct relationship between litter nutrient input to soil,and soil had a certain regulatory effect on litter decomposition,which soil TK played a major role.

Abstract:In order to explore the law of soil salinity and ion migration and aggregation under different irrigation and drainage modes in salinized irrigated area,From May to October 2021,soil water and salt monitoring and irrigation and drainage water monitoring were carried out in farmland under the modes of "drip irrigation+open ditch drainage" and "flood irrigation+dark pipe drainage" in the saline-alkali cultivated land improvement demonstration area in Wuyuan County,Bayannaoer City.To analyzed the migration and distribution of soil salt under different irrigation and drainage modes,and to explore the characteristics of soil salt and salt ion accumulation and desalting by equilibrium analysis,so as to provide scientific basis for water-saving planning and salinization prevention and control in irrigated areas.The results showed that the farmland soil was in a state of desalination under different irrigation and drainage modes,and the soil desalting effect was relatively good under "flood irrigation+dark pipe drainage" mode,the desalting rate is 37.73%.HCO₃^- was in a state of accumulation under "drip irrigation+open ditch drainage" mode,and the accumulation was 0.3 t.The accumulation of Ca²⁺ and Mg²⁺ occurred under "flood irrigation+dark pipe drainage" mode,the accumulated amount is 2.962 4 t and 0.577 4 t,respectively.During the whole growth period under "drip irrigation+open ditch drainage" mode,the 0—40 cm soil layer was in a state of desalinization,and the 40—80 cm soil layer appeared salt accumulation.Under "flood irrigation+dark pipe drainage" mode,the 0—100 cm soil layer was in desalinization during the entire growth period.The groundwater depth was the same under different irrigation and drainage modes.The groundwater depth was lower under "flood irrigation+dark pipe drainage" mode.The soil salt accumulation and groundwater quality were negatively correlated under "drip irrigation+open ditch drainage" mode,only HCO₃^- in soil was positively correlated with each ion of groundwater,and HCO₃^- in soil was strongly correlated with Mg²⁺ and HCO₃^- in groundwater,and the correlation coefficients were 0.833,0.759,respectvely.The overall correlation between soil salinity and groundwater quality was not obvious under "flood irrigation+dark pipe drainage" mode.

Abstract:In order to improve the water desalting efficiency of biochar on coastal saline-alkali soil,a granular biochar-polyacrylamide composite (PAM-BC) was obtained by blending biochar (BC),polyacrylamide (PAM),clay minerals in this study,while the effect of different environmental materials on the salt elution of saline soil from Haixing County was studied by a laboratory soil column simulation leaching experiment.The results showed that the treatments of PAM,BC and PAM-BC,CaSO₄(CS) significantly increased the elution amount of salt compared to CK,especially for the PAM-BC treatment with highest increase of 12.3%.The main salt ions in the eluent were further analyzed,the addition of PAM-BC significantly promoted the salt ions leaching of Na⁺ and Cl^- by 11.0%~27.3% and 17.8%~42.3% than other treatments,respectively.Principal component analysis indicated that PAM-BC addition enhanced the elution of major salt ions.The total salt content of soil under PAM-BC treatment was significantly decreased by 6.0%~16.7% compared to other treatments after the leaching of soil column.Moreover,the soil water characteristic curves indicated that PAM-BC promoted the water retention of saline-alkali soil.These findings can provide a theoretical basis for the application of PAM modified biochar in the salt reduction and soil improvement in coastal saline-alkali soil.

Abstract:In order to explore the reasonable amount of brackish water icing irrigation water and the dynamic migration of soil hydrothermal salt during freezing-thawing period under saline freezing irrigation,taking the severe saline and alkali land as the research object,an in-situ freezing-thawing experiment was carried out in Dalat Banner,Inner Mongolia for two consecutive years,and four irrigation gradients was set,with irrigation amount of 140 mm (S1),180 mm (S2),220 mm (S3) and the control (CK) without irrigation,respectively,the salinity of irrigation water was 8~10 g/L.By measuring soil moisture content,soil temperature and salinity distribution during the experimental period,the dynamic migration characteristics of soil hydrothermal salt in saline and alkaline land under saline ice irrigation were analyzed.The results showed that brackish water icing irrigation could significantly increase the soil moisture content after spring ablation,slow down the deep soil temperature variation degree during the freeze-thaw period,reduced the salinity phenomenon caused by soil temperature change,and the larger the irrigation water volume,the greater the increase of soil moisture content and the more significant the thermal insulation effect.After repeated freeze-thaw cycles,soil salinity was reduced under suitable brackish water icing irrigation treatment,and the desalination rate was positively correlated with the irrigation amount when the irrigation water amount was less than 180 mm,and the soil salinity content increased after spring ablation when the irrigation amount was more than 180 mm.During the 2-year experimental period,compared with the control treatment without irrigation,the soil moisture content under the brackish water icing irrigation treatment was increased by 82%~93%;the soil ablation index was increased by 28%~65%;the soil freezing index was reduced by 24%~25%;the desalination rate of 0—40 cm soil layer when the irrigation amount was less than 180 mm could reach up to 59%.Considering the comprehensive consideration,under the premise of not causing soil salt accumulation leading to secondary salinization,soil insulation,moisture preservation and desalination effect under irrigation water of 180 mm is the best,which can provide a suitable soil environment for crop growth in the coming year.

Abstract:In order to study the effect of chemical amendments on fluorine migration in the paddy ecosystem of soda saline-alkali soil,pot experiments were conducted to study the changes of fluorine content in various forms of soil and the migration of soil fluorine to water and aboveground plants under the effects of aluminum sulfate,desulfurized gypsum and organic compound modifiers.The results showed that chemical amendments would affect the migration and bioavailability of fluorine in soda saline-alkali soil-water-crop system.After planting rice,the variation of soil water-soluble fluorine in each amendment treatment ranged from 8.33 to 20.90 mg/kg,which showed a downward trend compared with the control,of which aluminum sulfate treatment decreased the most,by 60.15%;Exchangeable fluorine and organic bound fluorine showed an increasing trend,among which the organic compound modifier treatment increased the most,by 79.54% and 86.37% respectively;The changes of iron manganese oxide bound fluorine before and after rice planting were complex,among which aluminum sulfate treatment had no significant change,the control treatment and organic compound modifier treatment increased by 19.05% and 42.03% respectively,while desulfurization gypsum treatment decreased by 22.79%;The contents of residual fluorine and total fluorine showed a downward trend,among which the residual fluorine decreased the most by 35.50% under the organic compound modifier treatment,the total fluorine decreased the least by 10.47% under the aluminum sulfate treatment,and the other treatments decreased by 12.50% to 12.55%.In the process of rice planting,the total cumulative released amount of fluorine from soil to water was control > organic compound modifier > desulfurization gypsum > aluminum sulfate.Compared with the control,the other three treatments decreased by 3.25%,5.13% and 5.19% respectively.The total migration amount of fluorine in soil migrating to rice stems,leaves and paddy was in the order of organic compound modifier > desulfurized gypsum > aluminum sulfate,the migration amount per unit soil was 0.44,0.40 and 0.25 mg/kg respectively,and the migration rates were 0.16%,0.15% and 0.09% respectively.The results of correlation analysis showed that the total amount of fluorine released from soil to water and transferred to rice stems and leaves in soil were positively correlated with soil pH,soluble salt and various forms of fluorine content,while the fluorine content of rice paddy was not affected by soil properties.Because the absorption of fluorine by rice stems and leaves under the aluminum sulfate treatment was significantly lower than that of other treatments,and the content of water-soluble fluorine in soil and the total amount of fluorine released from soil to water were also less,aluminum sulfate modifier had a better ability to reduce fluorine migration and bioavailability in soda saline-alkali paddy soil.