Abstract:The flow of ecosystem services has been a hot topic in the comprehensive research fields of ecology, economics and geography since the 1990s. Water supply service has obvious flow characteristics and occupies a central position among many ecosystem services. It is a bridge connecting the ecosystem (supply area) and human production and life (demand area or beneficiary area), and is an important way to regulate water flow, water circulation, and water quality. Analyzing the flow of water supply services (conveyor area) from the perspective of supply and demand, and simulating the flow path, play a key role in realizing the benefits of water supply services. It also emphasizes the coordination and cooperation of social economy and ecological environment. It has important theoretical and practical significance for establishing the relationship between ecosystems and socio-economic systems. Therefore, research on the spatial flow of domestic water supply services needs to be carried out urgently. This research attempts to build a framework for the analysis of ecosystem water supply services, identify the scope of supply and benefit, determine the service flow mode, flow and flow path, and explore the causal relationship between water supply and demand. The literature analysis method is used to systematically sort out the research progress of the spatial flow of water supply services, and the vertical and horizontal comparisons are carried out respectively. The results show that:(1) According to the time sequence, it can be divided into three periods the basic germination period, the theoretical development period and the spatial correlation research period. (2) According to the functional area, it can be divided into three parts, water supply area, demand area and transportation area, and the quantitative analysis methods of each area are compared and analyzed. (3) Comprehensive analysis results, foreign research has developed rapidly, mainly based on model simulation. The research on domestic water supply services as a whole is in its infancy, and stays at the research level of the respective temporal and spatial patterns of ecosystem supply and demand. There is a lack of in-depth research on the relationship between water supply and demand services and spatial paths.

Abstract:To elucidate the roles of angle between rock and slope in affecting the processes of runoff and sediment yield in the Karst Trough Valley Area of Southwest China, the combined conditions of 6 angles between rock and slope (30°, 60°, 90°, 120°, 150°, 180°), 3 slope gradients (10°, 15°, 20°), and 3 flow rates (5, 7.5, 10 L/min) were employed in laboratory scouring simulation experiments. Results showed that:(1) Surface runoff rate increased to be stable with scouring duration, while sediment concentration and sediment yield rate both increased first and then decreased with the scouring duration; (2) Surface runoff rate showed non-significant differences among different angles between rock and slope (P>0.05). Sediment concentration and sediment yield both displayed non-significant differences among the angels of 30°, 60° and 120° (P>0.05),which were significant higher than those angels of 90°, 150° and 180° (P<0.05); (3) Surface runoff rate presented significantly positive power relationships with sediment concentration under the angles of 60°, 90° and 120° (R²=0.32~0.56, P<0.05), while exhibited non-significant relationships with sediment concentration at other angles (P>0.05). Similarly, surface runoff rate was significantly linearly correlated with sediment yield at the angles of 60°, 90°, 120°, 150° and 180° (R²=0.35~0.86, P<0.05). Our results show that a certain angle between rock and slope in the slope of the Karst Trough Valley area can accelerate the sediment yield and change the relationship between runoff and sediment yield.

Abstract:In order to understand the spatial distribution of sediment and nutrient under the impact of human activities, taking Yalong River and its first tributary Anning River as the research object, selecting the parallel section of Yalong -Anning River as the research area, six across sections along the river were selected, and the sediment concentration, nitrogen and phosphorus concentration were monitored vertically and transversely. The variation of sediment and spatial distribution characteristics of nutrient in different basins along the way were analyzed. The results showed that:(1) The sediment concentration of the Anning River was greater than that of the Yalong River, and the sediment concentration of the middle and lower reaches of these two rivers was higher than that of the upper reaches, and increased along the river. In the vertical distribution of sediment sections, there was no obvious stratification in Yalong River, while the stratification phenomenon of Anning River was remarkable,and the sediment concentration followed the order of bottom>surface>middle layer. In the transverse distribution of sediment section, except the middle and lower reaches of Anning River, the Yalong River and the upper reaches of the Anning River showed the right edge distribution. Generally, sediment uniformity of the cross section of Yalong River was better than that of Anning River. (2) TN and TP of Yalong River were significantly less than those of Anning River basin, and there were significant differences in spatial distribution of TN and TP of the parallel section of Yalong-Anning River in both vertical and horizontal sections. (3) There was a positive linear correlation between the concentrations of TN and TP and sediment in the parallel section of Yalong River. The fitting degree of transverse section was better than that of vertical section, and the correlativity between TN concentration and sediment was higher than TP. While for Anning River, the fitting degree of vertical section was better than that of transverse section, and the correlativity between TP concentration and sediment was higher than that TN.

Abstract:In order to study the soil anti-scourability and its relationship with soil physical properties in different land use types in karst area, taking Pinus Massoniana plantation land (PMP), Osmanthus fragrans plantation land (OFP), mixed forest land of natural arbor and shrub (ASL), natural grassland (NGL), abandoned land (AL) and cropland (CL) as research objects, the erosion test method of undisturbed soil flume was adopted, combining soil physical properties (bulk density, porosity, water-stable aggregates, mechanical composition, etc.), soil anti-scourability and its relationship with soil physical properties under different land use were quantitative analyzed. In the experiment, 3 slopes of 5°, 15°, 25° and 3 scour flows of 3.2, 4.8, 6.4 L/min were set up. The results showed that:(1) During the whole process of erosion test, the sediment concentration of runoff was the highest in the first 2 minutes of erosion, and then decreased gradually, and tended to be stable after 3~11 minutes. (2)The soil anti-scourability coefficient of each land use was NGL > PMP > ASL > AL > OFP > CL. The soil anti-scourability coefficient decreased with the increase of slope and erosion discharge, and the effect of slope on soil anti-scourability was more obvious than that of erosion discharge; (3) Soil anti-scourability was significantly positively correlated with soil bulk density, sand content and water-stable aggregate content (P < 0.01), and negatively correlated with total porosity and clay content (P < 0.05), which could be expressed by power function (R²>0.78). The results can provide scientific basis for soil erosion research and soil and water conservation control in karst area.

Abstract:This study focused on wind-water erosion that wind direction and runoff direction were opposite (i.e., windward slope) for understanding the interactions between wind and water erosion in the wind-water erosion processes using artificial simulated rainfall and wind tunnel experiments. Results showed that:(1) The prophase wind erosion resulted in the advanced runoff and increased intensity in water erosion compared with the single water erosion without wind erosion. (2) Water erosion rates were increased by the prophase wind erosion, yet rather than its changing tendency. Water erosion rates increased gradually and then tended to be stable over time during rainfall experiments regardless of whether the prophase wind erosion occurred or not. Particularly at relatively large wind velocities (12 and 15 m/s), an increase occurred in the water erosion rates, which could reach up to 4.6 times of the water erosion only. (3) The proportion of water erosion in wind-water erosion was always larger than that of water erosion in the sum of water erosion only and wind erosion only. This indicated that the prophase wind erosion obviously intensified water erosion. However, the contribution of water erosion to wind-water erosion decreased significantly (from 93% to 0.5%) with the increase of wind speed. Future research should consider the impacts of multiple occurrence of wind and water, and typical windward-leeward slope topography on crisscross erosion, to further explore the complicated interactions between wind and water erosions.

Abstract:In order to study the effect of slope and vegetation on the hydrodynamic characteristics of overland flow, a non-submerged rigid vegetation slope flow model based on the Navier-Stokes equation was established. The effectiveness of the model was tested by some experimental data. The calculated results were basically consistent with the experimental results. Based on the model and the actual situation of Southwest Mountain area, the hydraulic characteristics of overland flow were studied under 216 combined conditions of 6 slopes, 6 unit discharges, and 6 coverage degrees. The results showed that the relationship between flow velocity and slope, discharge and vegetation coverage is exponential, and the correlation is 0.987. Under the same flow, with the increase of slope, the growth rate of flow velocity decreased gradually, and the effect of vegetation on the slope flow slowed down gradually. The resistance coefficient was affected by slope, discharge, and vegetation cover, and there was a critical coverage. Below the critical coverage, the resistance coefficient was negatively correlated with discharge, and above the critical coverage, the resistance coefficient was positively correlated with discharge. The critical coverage was affected by the slope, the greater the slope, the greater the critical coverage. The results can provide theoretical reference for the prevention of soil and water loss and the study of the coupling mechanism of flood and sediment.

Abstract:To reveal the influence of long-term straw mulching and no tillage (NT) on soil structure and soil and water conservation of Mollisols sloping farmland, two 14 years long-term experiments, including NT and conventional tillage (CT), were conducted to compare soil structure, water conservation capacity and soil retention effect. The results showed that compared with CT, the soil bulk density of NT did not increased significantly (P>0.05). The total porosity and non-capillary porosity of NT were lower than those of CT in 0-20 cm layer, while NT increased the capillary porosity and content of water stable aggregate (WR_0.25), and the differences in WR_0.25 and mean weight diameter of soil aggregate (MWD) between the two treatments were significant (P<0.05). Meanwhile, NT increased the initial infiltration rate and stable infiltration rate of ridge platform by 28.8% and 24.7%, respectively. And in 0-10 cm layer, the differences in saturated water content and field capacity between the two treatments were significant (P<0.05). In addition, the number of runoff production, runoff and soil loss decreased by 11 times, 86.6% and 98.9% in NT, respectively. This study indicated that long-term continuous NT was an effective practice to stabilize soil structure and prevent soil erosion in Molliosls.

Abstract:The effects of different halophyte species and configurations on reducing agricultural non-point source pollution were studied by constructing a lakeside vegetation buffer zone on the ninth trunk canal shoreside of Wuliangsuhai Lake, Wulate Front Banner, Inner Mongolia. The results showed that the blank buffer zone without plant had no obvious reduction law of TN, TP and COD in runoff and seepage water. The reduction rates of the Phragmites australisbuffer zone, Suaeda glaucabuffer zone, Tamarix ramosissimabuffer zone, Phragmites australis and Suaeda glauca mixed buffer zone increased first and then slowed down with the increasing of the buffer zone width. The reduction effect of pollutants in seepage water was better than that of runoff water. Among them, P. australis had the best reduction effect on TN and TP in runoff and seepage water,with the reduction rates of 53.56%, 79.17% and 62.37%, 83.25%, respectively. S. glauca had the best reduction effect on COD in runoff and seepage water, with the reduction rates of 50.53% and 67.34%, respectively. Through calculation, the optimal width of the four vegetation buffer zones were 19~29 m, among which the width of S. glauca buffer zone was 19 m. Considering comprehensively, the true halophyte S. glauca could be selected as the preferred plant for the reconstruction of theWuliangsuhai Lake salinized lakeside, and the vegetation buffer zone could be expanded and applied in this area.

Abstract:In order to explore the response of interception and sediment reduction effect of grass-based vegetation filter strip to incoming water flow and sediment concentration, different incoming water flows (0.77, 0.9, 1.08, 1.26 L/s) and sediment concentrations(0.04, 0.06, 0.08, 0.1 g/cm³) were set up in a agro-pastoral ecotone in the central Inner Mongolia. The effect of river closure and sediment reduction of stem spacing in vegetation filter strip under different inflow conditions was studied. Based on VFSMOD model simulation, the relevant parameters of vegetation filter strip in this area were optimized. The results showed that VFSMOD model could well predict the sediment and runoff yield in the filter strip of agropyron cristatum and Leymus chinensis. The runoff interception of vegetation in the early stage mainly depended on soil infiltration, and the runoff outflow time was shortened with the increases of inflow intensities. The outflow time of 0.77 L/s inflow intensity was 1.3, 1.6 and 1.6 times of 0.9, 1.08 and 1.26 L/s. The sediment discharge under 0.77 and 0.9 L/s tended to be stable, while the 1.08 and 1.26 L/s increased with time. The inflow sediment content and inflow intensity have significant influence on the outflow sediment quantity (p<0.05).

Abstract:In order to further clarify the difference of riparian landscape scale and its impact on river phosphorus (P), the relationship between landscape and river P at riparian scale was analyzed quantitatively. Based on long-term hydrological and water quality monitoring data, this study used redundancy analysis to clarify the relationship between landscape pattern characteristics at different riparian scales and river P concentrations in different hydrological seasons. Change point analysis was used to quantify the threshold range of the core landscape metrics leading to the abrupt change of river P concentrations in wet and dry seasons. The results showed that:(1) The effects of landscape pattern buffer zones on river P concentration have significant spatial scale characteristics, 300 and 400 meters are the critical scales affecting river P concentration in wet season and dry season, respectively. (2) SPLIT of farmland patches (SPLIT_farm) and LPI of residential land patches (LPI_res) were the core landscape pattern characteristic indexes that affect river P concentration in dry season and wet season respectively. When the SPLIT_farm exceeded 15.76~23.83 and LPI_re was less than 28.8%~36.5%, the abrupt probability of P concentrations in wet and dry rivers can be reduced respectively. The results can provide important theoretical basis for land use and landscape planning aiming at mitigating P non-point source pollution.

Abstract:We selected catchment area above typical gully in the loess region of western Shanxi Province to study effects of gully on soil water content in the catchment area above in the Loess Plateau. The soil water content in a profile of 10 m was measured by soil core method and we discussed the soil moisture status of different landforms in the catchment area. The results showed that:(1) The soil moisture status in the catchment area was affected by the distance from the gully and the landform. (2) Soil water storage at 1 m from the head of the gully was significantly lower than that at 3 and 6 m. Soil water storage was higher in the depression than in the slope. (3)The shallow soil water content of 6 sampling points changed sharply with time, and the deep layer had little changes. (4)The horizontal influence distance of gully on soil water content in catchment area was 1~3 m, for gully in catchment area, 7 m for influence depth. It was suggested that drought-tolerant shrubs and herbs with low water consumption should be densely planted near the gully to increase the surface roughness and reduce the water flow velocity. And the plant roots could hold the soil and increase the anti-impact property to control gully erosion.

Abstract:In order to further understand the weathering and pedogenesis effects of biocrusts, we conducted this study to explore the effects of biocrusts development on base cations release and mineral weathering of aeolian sandy soil. The biocrusts developed on aeolian sandy soil were selected as research subjects, and the simulated leaching experiments were carried out to compare the release regularity of soil base cations under different biocrusts (cyano crust, mixed crust, and moss crust) covering. The variation amount of base cations in leachate with different pH values of leaching solution were explored. We also quantified the weathering rate of soil minerals under biocrusts covering. The results showed that:the leaching amount of base cations in the stage of mineral weathering reaction remained relatively stable. The total amount of different base cations in the leachate of biocrusted soil were Ca²⁺ > K⁺ > Mg²⁺ > Na⁺. The total amount of base cations in cyano crusted soil leachate was the highest. Compared with bare soil, mixed crust, and moss crust, the total amount of base ions in the leachate of cyano crusted soil increased by 112.0%, 31.2% and 27.1%, respectively. Additionally, the pH value of the leaching solution significantly affected the leaching of base cations, and its effect varied with the types of cations and biocrusts. According to the mineral weathering characteristics indicated by the release of base cations, biocrusts covering could increase the content, weathering degree and rate of easily weathered minerals in the soil. Compared with bare soil, the weathering rate of soil covered with cyano crust, mixed crust, and moss crust increased by 61.2%, 27.1% and 152.6%, respectively, and the weathering rate increased with the decrease of leaching solution pH value. All the above findings showed that biocrusts covering can significantly promote the mineral weathering process of aeolian sandy soil, which is of positive significance to the improvement and restoration of aeolian sandy soil.

Abstract:As an important ecological corridor in China, the Yellow River Basin (YRB) plays an important role in maintaining China's ecological security. Understanding the spatial interactions between urbanization and ecosystem services is the basis for sustainable regional development. Based on the characteristics of urbanization development and the spatial distribution pattern of ecosystem services in the YRB from 2000 to 2018, the spatial and temporal interaction relationship and evolutionary characteristics of urbanization and ecosystem services in the YRB were further revealed using Pearson correlation coefficient and bivariate spatial autocorrelation. The results showed that:(1) The urbanization of the YRB had a significant spatial heterogeneity, and the comprehensive urbanization index increased from 2000 to 2018, with a growth rate of 102.60%, among which the development of economic urbanization was generally faster than that of land urbanization and population urbanization. (2) Food production, carbon sequestration services and soil conservation in the YRB increased by 65.32%, 59.47% and 46.27%, respectively, while water yield decreased by 21.15%. (3)The relationship between urbanization and ecosystem services in the YRB from 2000 to 2018 showed a weakening of the positive effect and an increase of the negative effect at both spatial and temporal scales, and the areas where the development of urbanization is not coordinated with ecosystem services are expanding.

Abstract:To understand the temporal and spatial distribution and variation of slope soil water in different microtopography. In this study, the Beijing Jiufeng National Forest Park slope forest was taken as the research object. Based on detailed investigation, 30 soil water observation points that with 10 cm intervals were arranged on the slope of 40 m×50 m, and the observation depth ranges from 50 to 70 cm. We conducted a total of 20 soil water observations from April 2015 to October 2015. The results showed that:(1) Slope soil water has the same temporal change trend, and it generally changes with the fluctuation of the rainfall. (2) The soil water changed with the change of the slope position, for horizontal step, the upper slope position < the middle slope position; for gentle slope, the middle slope position < the down slope position. (3) The overall slope soil water content increased with soil depth. Soil and water conservation engineering measures could effectively improve the soil water status. The microtopography mainly affected the soil layer larger than 30 cm.Soil water content of different microtopography was shown as: level bench > gentle slope > steep slope > scarp, soil water content of level bench was significantly higher than that of other microtopography (P<0.05). (4) Redundant analysis results showed that microtopography was the main factor affecting soil water content, with relative contribution rates of 81.2%. Microtopography factors weakened the influence of altitude and slope position on soil water content. This study could provide a basis for the assessment of the impact of ecological restoration of rocky mountainous areas on hydrology and water resources.

Abstract:In order to explore the effect of adding desulfurized gypsum on the water movement parameters of saline-alkali soil, and improve and increase the soil productivity in the Yinbei Plain area, through an indoor one-dimensional soil column absorption test, 6 desulfurized gypsum treatments were selected:0, 1.5%, 3%, 4.5%, 6% and 7.5%, to study the horizontal infiltration characteristics and water movement parameters of saline-alkali soil. The results showed that the addition of desulfurized gypsum slowed down the process of soil moisture infiltration. As the proportion of desulfurized gypsum increased, the cumulative infiltration amount and the movement distance of the wet front of each treatment gradually decreased. Power function and Philip model could better fit the water movement characteristics of saline-alkali soil under different desulfurized gypsum addition ratios, and the absorption rate decreased with the increase of the desulfurization gypsum ratios, and the capillary force's water holding effect weakened. As the proportion of desulfurized gypsum increased, the saturated water content of the soil increased and the saturated hydraulic conductivity decreased, the soil water holding capacity was significantly improved. The shape coefficient h_d in the Brooks-Corey model gradually decreased, and the intake suction h_d gradually increased, and soil aeration was enhanced. Under the same moisture content, the soil unsaturated water diffusivity gradually decreased with the increase of the desulfurization gypsum ratios. The addition of desulfurized gypsum increased the soil water holding capacity, changed the soil moisture distribution, and had a significant impact on soil water movement parameters. This study could provide theoretical support for the rational use of desulfurized gypsum to improve saline-alkali land.

Abstract:The Zhifanggou watershed in the loess hilly and gully region was selected as the study area in this study. By high-precision remote sensing images (resolution 0.068 m) and DEM (resolution 0.34 m) data, combined with field investigations, the collapse, slide, landslide, creep and sinkhole were analyzed. The spatial distribution of different types of instability bodies were analyzed by using statistics and sensitivity coefficient methods. The main controlling factors of instability bodies were further clarified. The results showed that:(1) The instability bodies was obtained using high-precision remote sensing images, mainly in the form of small-scale and shallow shedding, collapse and slide. The total area of the three was 0.417 km², accounting for 5.04% of the total watershed area. (2) Among the evaluation factors, the red clay of the soil parent material, the natural shrubland and grassland of the land use, the ditch slope of the landform, the slope of > 35° and RF of 0.74~3.34 m, were the highly sensitive areas where slope instability occurred. They are also the common sensitive area for collapse, slide, shedding, and sinkhole. (3) The weights of the main controlling factors affecting the stability of the slope were as following from large to small soil parent material, RF, slope, land use and aspect. The main controlling factors of collapse, slide and shedding were the same as the overall slope stability, but their internal weights of the factors were different. The order of the weights of the main controlling factors of collapse was consistent with the overall slope stability. The weights of the main controlling factors of landslide were as follows:soil parent material > RF=slope > land use > slope aspect > landform position. The weights of the main controlling factors of shedding was soil parent material > land use > RF > slope=slope aspect > landform position. The main controlling factors of landslide were slope andRF. The weights of the main controlling factors of caverns was soil parent material > RF > slope > slope aspect.

Abstract:To explore the water conservation capacity of vegetation in the forest park and provide a reference for vegetation configuration and management, six typical stands in Tianlong Mountain Forest Park were selected to investigate and analyze the litter thickness, accumulation, water holding and other indicators inside the forest. Soaking methods were used to measure the hydrological effect of litter.(1) The interference and thickness of litter ranged from none to moderate and from 0.57 to 2.63 cm, respectively, among which, Populus davidiana gave the largest, and the mixed forest of Platycladus orientalis-Pinus tabuliformis-Armeniaca sibirica gave the smallest. The accumulation range was 7.20~16.30 t/hm², among which, Pinus tabuliformis-Platycladus orientalis mixed forest was the largest, and Platycladus orientalis-Pinus tabuliformis-Armeniaca sibirica mixed forest was the smallest. (2) Except for Populus davidiana, the maximum water holding capacity of the semi-decomposed layer was greater than that of the undecomposed layer, among which, Pinus tabulaeformis-Platycladus orientalis was the largest and Platycladus orientaliswas the smallest. The maximum water holding rate of undecomposed layer was larger than that of semi-decomposed layer, the largest was found under Robinia pseudoacacia and the smallest under shrub. The range of maximum water holding capacity was 20.02~27.90 t/hm², and the range of maximum water holding rate was 187.40%~277.89%. The water holding rates of coniferous and broad-leaved mixed forest were comparatively higher. (3) The maximum effective storage capacity of tree species was found in Populus davidiana with its value of 15.05 t/hm²; the minimum was Pinus tabuliformis of 12.33 t/hm². Platycladus orientalis-Pinus tabuliformis-Armeniaca sibirica mixed forest had the maximum storage rate. (4) The relationships of litter water holding capacity and water holding rate with time could be fitted by logarithmic and power functions, respectively. Both of them reached the peak values within two hours of soaking in water. Based on the comprehensive comparison of six forests, light disturbed Populus davidiana had the best hydrological benefits; oppositely, moderate disturbed Pinus tabuliformis-Platycladus orientalis mixed forests had the worst. The broad-leaved species had better hydrological effects than coniferous species, and the mixed coniferous and broad-leaved species were better than a single species. These consequences can provide references for the vegetation configuration and hydrological benefit evaluation of forest parks.

Abstract:In order to reveal the effects of forest succession and climate warming and their interactions on soil autotrophic respiration and plant root respiration at different forest levels, 4 natural secondary forests (Poplar-birch broad-leaved deciduous forest, Pinus tabulaeformis conifer broad-leaved mixed forest, Larix principis rupprechtii forest and Picea asperata forest) at different succession stages in Guandi Mountain were studied. From 2016 to 2019, Li-6400 portable analyzer was used to observe the changes of plant root respiration and soil autotrophic respiration rates at different levels of each forest type during the growing season. Greenhouse heating method was used to simulate the effects of temperature increase on autotrophic respiration and its components. The results showed that:(1) The root respiration rate and soil autotrophic respiration rate decreased with succession, and the contribution rate of soil autotrophic respiration to total soil respiration increased significantly with succession. The contribution rate of root respiration to soil autotrophic respiration increased significantly in arbor layer, but decreased significantly in shrub layer and herb layer. (2) Warming significantly increased soil autotrophic respiration ranging from 8.48% to 8.76% in different successional stages, and soil autotrophic respiration gradually increased with the successional process. The response of root respiration rate to warming was different in different forest layers. Warming significantly increased root respiration rate in herb layer (10.88%~14.00%) and shrub layer (8.37%~15.26%), but it had no significant effect on root respiration rate of arbor layer. Increasing temperature decreased the contribution rate of soil autotrophic respiration and root respiration in arbor layer, while it increased the contribution rate of root respiration in herb layer. (3) Warming and succession did not change the variation law of soil autotrophic respiration and its components in the growing season, but it had significant coupling effects on soil autotrophic respiration, herb layer and shrub layer plant root respiration. In conclusion, soil autotrophic respiration rate and root respiration rate of shrub layer and herbaceous layer had significant response to temperature increase, and had significant coupling effect on the interactive process of succession and temperature increase, which provide data support and theoretical basis for the study on the effect of forest regeneration process on forest soil carbon emission under the background of climate warming.

Abstract:This research calculated vegetation coverage on the Loess Plateau from 2000 to 2020 by using the MODIS-NDVI vegetation index, analyzed its relationship with rainfall, temperature, slope and soil by using the transfer matrix and other methods. The results showed that:(1) The vegetation coverage increased from 0.39 to 0.61, and increased rapidly after 2017. (2) The area ratio of significantly improved and extremely significantly improved reached 37.93%. The coverage was dominated by low and middle-low before 2009, and dominated by medium and higher coverage after 2010. The proportion of middle-high coverage was the highest after 2019. (3) The conversion ratios of low, medium-low, medium and medium-high cover to the higher cover were 93.10%, 96.57%, 82.99%, 43.34% respectively. The conversion ratios of medium-low, medium, medium-high and high cover to the lower cover were 0.30%, 2.21%, 7.83%, 12.47% respectively. (4) The changes of vegetation coverage were sensitive to the changes of temperature and rainfall. The vegetation coverages of slope, steep slope and leached soil were higher. Human interventions, such as policies and soil conservation measures, played an important role in vegetation coverage improvement.

Abstract:Soil and water loss is serious in the Wuding River Basin, so soil conservation service becomes the primary ecosystem service. Based on SWAT model and GIS, the balance between supply and demand of soil conservation service and spatial flow path were analyzed to reveal the spatial matching characteristics and spatial flow mechanism of soil conservation service in the Wuding River Basin. The results showed that there was a strong consistency between the supply and the demand of soil conservation service in the Wuding River Basin, and both of them showed a trend of fluctuant increase and had a strong correlation with precipitation. The supply and demand in August 2001, July 2013 and July 2017 reached the larger value in all the months from 2000 to 2020, with the supply exceeding 2.5×10⁸ t and demand exceeding 3.5×10⁸ t. Correspondingly, the monthly average precipitation also reached a large value in these three months. From 2000 to 2020, the deficit months were more than the surplus months, and the deficit was increasing. The middle and upper reaches were in surplus, with the supply slightly greater than the demand, while the middle and lower reaches were in deficit, with the demand far greater than the supply. The spatial flow path of sediment reduction service was simulated. On this basis, the flow and benefit of sediment reduction service in each subbasin were obtained. The fluctuation of sediment reduction service flow increased from 2000 to 2020, especially in the downstream area in 2020. The benefit of sediment reduction service had accumulative benefit in the basin and showed an increasing trend during the study period. The results could provide a new perspective for the control of soil erosion in watershed, and have important reference value for ecological restoration and policy making of soil and water loss control.

Abstract:The purpose of this paper is to understand the present situation of agricultural water resources utilization in nine provinces of the Yellow River Basin and to clarify the obstacles to improve agricultural water resources utilization efficiency. Based on entropy weight Topsis model, 9 provinces of the Yellow River Basin were taken as evaluation units, and 14 evaluation indexes were selected from resource utilization efficiency, economic benefit and ecological benefit to construct a comprehensive evaluation index system of agricultural water resources utilization efficiency. The agricultural water resource utilization efficiency was evaluated by the comprehensive evaluation index system and its obstacle factors were diagnosed in 2004, 2009, 2014 and 2019. The results showed that:(1) From 2004 to 2019, the agricultural water resource utilization efficiency in Qinghai, Inner Mongolia, Henan, and Shandong was relatively high, while that in Shaanxi, Gansu, and Shanxi was relatively low. (2) From 2004 to 2019, the agricultural water resources utilization efficiency of the nine provinces increased on the whole, and the difference of agricultural water resources utilization efficiency among the nine provinces gradually decreased. (3) The main obstacle factors of Shanxi, Shandong, Henan, Sichuan, Shaanxi, Gansu, and Ningxia were per capita water resources (A6) and per capita ecological water consumption (A13); per capita ecological water consumption (A13) and agricultural water resource utilization efficiency (A4) were the main obstacles in Qinghai. Average water resources occupancy (A6) and total agricultural production value (A9) were the main obstacles in Inner Mongolia. Therefore, water resources endowment and ecological water consumption are the main factors affect the agricultural water resources utilization efficiency in the nine provinces.

Abstract:To study the effect of nitrogen addition on the non-structural carbon of species in different ecological niches, we conducted a three-year nitrogen addition experiment on typical abandoned grasslands on the Loess Plateau and analyzed the soluble sugar, starch and non-structural carbon content of species in different ecological niches. The nitrogen gradients were N0 (0 g/(N·m²·a)),N3 (3 g/(N·m²·a)),N6 (6 g/(N·m²·a)) and N9 (9 g/(N·m²·a)). Our study showed that the nitrogen addition mainly affected the storage of non-structural carbohydrates in Bothriochloa ischaemum andStipa bungeanathat occupied the higher niches, while it had little effect on Artemisia sacrorumand weeds. The N6 and N9 treatments significantly increased the storage of non-structural carbon, soluble sugar and starch of Bothriochloa ischaemum andStipa bungeana, especially for the aboveground part. Besides, the relative importance value had significantly positive correlation with the belowground non-structural carbon and starch contents, but had significantly negative correlation with the aboveground soluble sugar content and the ratio of soluble sugar to starch. Our findings are helpful to strengthen our understanding of the carbon storage and distribution characteristics of species in different ecological niches under the background of nitrogen deposition.

Abstract:The purpose of this study was to evaluate the soil carbon sink effects of long-term vegetation restoration on the Loess Plateau. A commonly method of spatial and temporal substitution was applied to study the change characteristics of soil organic carbon content and corresponding reserves of eight vegetation succession sequences in the Ziwuling area among nearly 150 years, also analyzed vegetation factors affecting the soil organic carbon reserves changes. The results showed that from slope farmland to Quercus wutaishanica Mary. communities, which was in its highest climatic stage, soil organic carbon contents and corresponding reserves increased significantly, showing a rapid increase in the early stage of succession (grassland communities) and a stable change in the later stage (arbor communities). Soil organic carbon content decreased rapidly as the soil layers deepened in profile. The soil organic carbon content in 0-5 cm soil layer differed significantly from those in 5-20 and 20-40 cm soil layers (P < 0.05), indicating a significant surface aggregation effect of soil organic carbon accumulation. Both litter biomass and fine root biomass were increased with succession time, while litter biomass was more conducive to increasing soil organic carbon reserves. A highly significant power function relationship was found between soil organic carbon reserves and vegetation restoration time for 0-5 and 0-20 cm soil layers, also soil organic carbon storage in different soil layers showed a significant linear correlation (P < 0.001). Long-term vegetation succession had a significant soil carbon sink function. The forests and grasslands restoration in the Loess Plateau should be premised on the distribution patterns of natural vegetation zones and promote its natural succession in the future, thus could further enhance the potential of soil carbon sinks capacity in the region.

Abstract:This study aimed to reveal the spatial-temporal variation of evapotranspiration (ET) in the loess Plateau during the past two decades and clarify the effects of climate and underlying surface changes on ET. Based on the data of 295 meteorological stations on the Loess Plateau, PML_V2 ET products and MOD13A1 EVI products, this study used trend analysis and multiple regression statistical methods to study the spatial-temporal variation characteristics of ET from 2000 to 2018, and the relative contributions of rainfall, temperature, sunshine duration, vapor pressure difference, vegetation and non-vegetation underlying surface were also quantitatively evaluated. The results showed that:(1) From 2000 to 2018, the annual change rate of ET on the Loess Plateau was 4.47 mm/a. The ET increased significantly in Shanxi, Qinghai and northern Shaanxi Provinces, accounting for 62.8% of the total area. The contribution of different land covers to ET was forest, farmland, grassland and shrub in descending order. (2) The significant increase of vegetation was the leading factor of ET changes in the Loess Plateau, and its relative contribution rate was the largest (32.1%). The relative contribution rates of different meteorological factors to ET from high to low were rainfall (14.6%), saturated vapor pressure difference (13.2%), temperature (12.4%) and sunshine duration (10.0%). The influence of non-vegetation underlying surface change (such as soil and water conservation engineering measures) on ET change could not be ignored.(3) The effects of meteorological factors and enhanced vegetation index on ET of forest and grass cover were greater than that of farmland cover, while non vegetation underlying surface elements had a greater impact on ET of farmland cover. The research results are expected to provide scientific support for water resources consumption, restoration and sustainability evaluation of ecological construction in the Loess Plateau.

Abstract:Rainfall partitioning by forests is one of the important processes in forest eco-hydrological and biogeochemical cycles. In this study, the characteristics and main influencing factors of rainfall partitioning of two typical forest types (Robinia pseudoacacia plantation and Quercus liaotungensis natural secondary forest) were investigated by field monitoring during the growing season in the loess hilly region. The results showed that during the experiment, the components of rainfall partitioning in R. pseudoacaciaplantation and Q. liaotungensis forest were in the order of throughfall (325.0 and 295.1 mm) > canopy interception (39.8 and 73.6 mm) >stemflow (25.8 and 21.9 mm), and throughfall rate (83.2% and 75.6%) > canopy interception rate (10.2% and 18.8%) >stemflow rate (6.6% and 5.6%). Rainfall amount was the key factor affecting rainfall partitioning. A highly significant linear relationship was observed between throughfall and stemflow and rainfall amount, while the relationship between canopy interception and rainfall amount exhibited a highly significant logarithmic function. A significant logarithmic relationship existed between throughfall rate and stemflow rate and rainfall amount, while a highly significant exponential relationship was found between canopy interception rate and rainfall amount. Throughfall processed when rainfall exceeded 1.0 and 1.3 mm for R. pseudoacacia plantation and Q. liaotungensis forest, respectively. Stemflow processed when rainfall exceeded 5.9 and 5.4 mm for R. pseudoacacia plantation and Q. liaotungensis forest, respectively. The throughfall and stemflow generated by R. pseudoacaciaplantation were larger than that of Q. liaotungensis forest,while the canopy interception was smaller than that of Q. liaotungensis forest. This study provides basic data for the research of eco-hydrological processes in the loess hilly region, and has guiding significance for the selection of vegetation types in the process of vegetation restoration in this area.

Abstract:In order to master the effects on soil infiltration performance of different vegetation cover types around Dianchi Lake Basin in Central Yunnan Plateau, double ring infiltration method was used to explore soil infiltration characteristics. Taking the typical vegetation cover types ofPinus armandiiFranch.+ Keteleeria evelynianaMast.mixed forest, Pinus yunnanensispure forest, Alnus nepalensisD. Don + Quercus acutissimaCarruth.mixed forest, Eucalyptus robustaSmith artificial forest and shrub forest in Dianchi Lake Basin as the research objects, soil infiltration characteristics and its influencing were studied through field investigation and experimental measure. The results showed that:(1) Compared with P. yunnanensis pure forest, A. nepalensisD. Don + Q. acutissimaCarruth.mixed forest and E. robustaSmith artificial forest and shrub forest, P. armandiiFranch.+ K. evelynianaMast.mixed forest had the lowest soil bulk density, the highest content of organic matter, the most water stable aggregates, and the proportion ofporosity and non capillary porosity. (2) Soil infiltration performance significantly differed under different vegetation cover types, which listed in the following order:P. armandiiFranch.+ K. evelynianaMast. mixed forest > A. nepalensisD. Don+ Q. acutissimaCarruth.mixed forest > shrub forest > P. yunnanensispure forest > E. robustaSmith artificial forest. (3) Kostiakov formula, Horton formula, and Philip formula were selected to simulate the soil infiltration process of forest land under five typical vegetation types. Through data comparison, it could be seen that Philip model had the best fitting effect on the soil infiltration process of Dianchi Lake Basin. (4) Correlation analysis showed that there was a significant negative correlation between soil infiltration characteristics and soil bulk density under five typical vegetation types (P<0.05), and there were significant positive correlations between initial infiltration rate and non-capillary porosity, >5 mm water stable aggregate content, and >2 mm water stable aggregate content (P<0.01). Principal component analysis showed that the five main influencing factors of soil infiltration were >2 mm water stable aggregate content, >5 mm water stable aggregate content, bulk density, organic matter, and non-capillary porosity. The research results could provide a basis for soil erosion control and soil erosion control in the study area.

Abstract:After Beijing implemented plain afforestation projects in the riparian zones of major rivers, the vegetation types and soils in the riparian zones have been affected to varying degrees. The study of soil ecological stoichiometry characteristics of the original and reconstructed vegetation types in the riparian zone provides scientific basis for the soil carbon (C), nitrogen (N) and phosphorus (P) balance and the improvement of the C sequestration potential of the riparian ecosystem. Total 3 original vegetation types (arbor forest, arbor-shrub mixed forest and grassland) and 2 reconstructed vegetation types (arbor forest and shrub forest) were selected as experimental samples at 15 sites of Beijing Wenyu River Changping riparian zone. Soils were sampled at 3 layers (0-10, 10-20, 20-30 cm), and analyzed for the contents and measurement ratios of C, N and P. The results showed that the ranges of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) of the original and reconstructed vegetation types were 3.810~10.320, 0.223~0.700, 0.551~0.692 g/kg respectively, C/N, N/P, and C/P were 11.592~25.373, 0.373~1.022, 5.662~15.493 respectively. Both SOC and TN were concentrated in the surface layer, and like N/P and C/P, they decreased with the increases of soil depth, while the C/N was on the contrary. TP was less affected by the change of soil depth. The SOC and TN in the original vegetation types (arbor forest) were higher than the others. The C/N and C/P at 10-20 and 20-30 cm soil layers were significantly lower than the others (P< 0.05). The N/P of original vegetation types (grassland) was the lowest at 0-10 cm soil layer. The soil TP content of reconstructed vegetation type (arbor forest) was significantly lower than those of the other vegetation types. The C/N of reconstructed vegetation types (shrub forest)was significantly higher than the others. The study revealed that the soil N was the limiting factor for plant growth. Arbor and arbor-shrub mixed forest released more soil organic matter, had the higher levels of P availability, and had strong carbon sequestration potential. The re-vegetation types had the slower organic matter mineralization and stronger phosphorus fixation capacity. Thus, it's recommended that the mixed mode of pure forest and arbor-shrub mixed could accumulate soil organic matter and improve the soil quality and carbon sequestration potential of riparian ecosystems in the Wenyu River riparian zone.

Abstract:In order to explore the variation characteristics of the three phase composition of soil "solid-liquid-gas" in alpine meadow at different altitudes and slope aspects, the alpine meadow in eastern Qilian Mountain was taken as the research object, and the vegetation characteristics and soil physical characteristics of alpine meadow at the different altitudes (2 800, 3 000, 3 200, 3 400, 3 600, 3 800 and 4 000 m) and aspects (sun slope, shady slope) were analyzed. Combined with vegetation index fitting, the optimal composition ratio of the "solid-liquid-gas" three phase of alpine meadow was explored. The results showed that the vegetation coverage, grass layer height and aboveground biomass increased first and then decreased with the increasing of altitude, and reached the maximum at 3 200 m. At the same altitude, the vegetation coverage, grass layer height and aboveground biomass on the shady slope were higher than those on the sunny slope. The variation law of soil bulk density with altitude and slope aspect was opposite to that of vegetation coverage, while the variation laws of soil water content, porosity and water holding capacity were similar to that of vegetation coverage. After equation fitting, the productivity of the alpine meadow was the best when the soil "solid-liquid-gas" three phase ratio was 31:33:36. In conclusion, 3 200 m was the central typical area of the distribution of alpine meadow in the eastern Qilian Mountains. The altitude and slope aspect were important environmental factors affecting the soil physical quality of the alpine meadow and the "solid-liquid-gas" three-phase composition. The optimum ratio of "solid-liquid-gas" in meadow soil in this area was 31:33:36.

Abstract:The species and quantity of undergrowth weeds of chestnut forest in the northern Yanshan Mountains were investigated. Based on the field survey data of 2017, 2018 and 2020, Levins niche index and Pianka niche overlap index were used to analyze the niche dynamics of major undergrowth weeds, resource utilization, and interspecific competition of chestnut forest. The results showed that:(1) There were 53 species (48 genera, 27 families), 47 species (43 genera, 24 families), and 44 species (41 genera, 24 families) in the understory weed community of chestnut in 2017, 2018 and 2020, respectively. Among them, there were 15 species of dominant weeds. (2) Among the 15 dominant weeds, Humulus scandensand Chenopodium glaucumL. occupied a wider ecological niche and had a higher degree of diversity in their use of environmental resources. The niche width of Commelina communis, Artemisia argyi, Setaria viridis, Rubia cordifolia, Ixeris polycephala, Chelidonium majus, Viola philippica, Chenopodium glaucum, Digitalis purpurea and Glycine soja. were increasing, and these species had increased resource availability. (3) In the weed community, the number of major species with niche overlap value less than 0.2 decreased significantly, and the interspecific competition was more complex. The main weed species gradually increased their ability to make full use of the surrounding resources and environment. Accurate knowledge of weed occurrence, dominant population and community composition in Chestnut orchard can provide theoretical basis for targeted weed control in chestnut understory in northern Yanshan.

Abstract:Effects of straw returning directly and carbonization returning combined with nitrogen fertilizer on the content of carbon and nitrogen in soil and cotton yield were evaluated through a field positioning experiment for seven consecutive years. Using a two-factor experimental design, three straw returning modes were set up, which were no straw returning (CK), straw returning directly (ST) and straw carbonization returning (BC). Three nitrogen application rates were set up as 0 (N0), 300 (N300) and 450 (N450) kg/hm², respectively. The results showed that the content of soil organic carbon in ST and BC treatments increased year by year, and the increase of BC was greater than that of ST. In the 7th year, under different nitrogen application levels, the soil organic carbon of ST treatment was 33.28%~36.43% higher than that of CK, and that of BC treatment was 58.56%~63.25% higher than that of CK. Straw returning (ST and BC) for many years could improve the content of soil total nitrogen. Under N0 level, the highest of total nitrogen content was found in ST treatment. Under N300 level, the total nitrogen content of BC was significantly higher than that of ST after seven years. Under N450 level, the total nitrogen content of BC treatment was higher than that of ST after five years. Both ST and BC treatments increased soil C/N ratio under N0 level, while only BC treatment increased soil C/N ratio under N300 and N450 levels. Straw carbonization returning combined with nitrogen fertilizer application significantly increased cotton yield. Compared with CK, BC treatment increased cotton yield by 17.43%~17.89% under N300 and N450 levels. Therefore, straw carbonization returning combined with nitrogen fertilizer application could improve soil organic carbon content, nitrogen pool capacity and soil C/N ratio and cotton yield.

Abstract:The aim of current study was to reveal the utility of irrigation and rain water resources in paddy fields. Based on the observation of the field water balance in experimental plots with frequent and shallow irrigation (FI), wet-shallow irrigation (WI), controlled irrigation (CI) and rain-catching and controlled irrigation (RI) treatments, this study established the classification method of consumption fluxes of irrigation water and precipitation and the evaluation index system of utilization utility. The response of irrigation and drainage mode of water resources utilization was analyzed. The results showed that water consumption, effective utilization rate and water productivity were all affected by irrigation and drainage mode. In 2017-2018, the water resources consumption of all treatments varied in the range of 695.9~999.1 mm, among which the water resources consumption in CI treatment were the lowest, and the consumption structure was more reasonable. The irrigation water productivity (IWP, 5.392 kg/m³), the precipitation productivity (PWP, 1.539 kg/m³) and the water resources productivity (WRP, 1.364 kg/m³) in CI treatment all showed the highest water resources production capacity. The irrigation efficiency (IE), precipitation use rate (PE) and generalized water efficiency (GE) were 0.472, 0.406 and 0.693, respectively, which the differences among treatments were less than the differences among treatments about productivity indexes. The water resources utility evaluation index system based on the distinction between irrigation water and precipitation consumption flux could truly measure the performance of water resources in agricultural production, especially in the growing season with frequent precipitation. The results can provide theoretical basis for the evaluation of agricultural water resources utility and the formulation of paddy field irrigation and drainage mode.

Abstract:This study aimed to investigate the effect of biochar application on the soil hydrothermal characteristics and three-phase structure in the cultivated layer of drip irrigated cotton fields during the non-irrigation season. Five biochar application amounts, 15 (B₁), 30 (B₂), 45 (B₃), 60 (B₄) and 0 (B₀) t/hm², were set to analyze their effects on the three-phase structure, total porosity, soil temperature and soil moisture content of topsoil (0-40 cm) in non-irrigation season of drip irrigation cotton field in Xinjiang. After the non-irrigation season, compared with the control, the soil solid volume decreased by 2.58%~10.74% and the total porosity increased by 3.38%~12.05%. At the same time, the soil moisture contents of carbon application treatments increased by 1.07%~2.65% compared with the control. The soil thermal conductivity decreased, and the soil thermal insulation effect increased. The minimum temperature of soil plough layer in non-irrigation season increased by 0.34~2.15℃,and the maximum temperature difference decreasedby 0.47~2.14℃. In addition, based on the above soil structure and hydrothermal characteristics of principal component analysis, the highest comprehensive score was B₃, followed by B₂. In conclusion, biochar application in non-irrigation season was beneficial to improve soil three-phase structure, increase soil total porosity and enhance soil moisture and heat preservation ability. The best application amount of biochar in non-irrigation season of drip irrigation cotton field in Xinjiang should be 30~45 t/hm².

Abstract:In order to determine the effects of different mulching methods on soil water depletion, water consumption patterns, water use efficiency, yield and yield formation in dryland potato fields, five mulching methods, including whole maize straw strip double row mulching (SSM2), whole maize straw strip single row mulching (SSM1), full mulching of maize straw (SFM), plastic film spring mulching (PMS) and plastic film autumn mulching (PMA), were set up in the semi-arid agricultural region of Longzhong, with the traditional bare land as the control (CK). The results showed that compared with CK, Soil water consumption increased by 13.5 and 14.8 mm for the whole maize straw strip mulching and plastic film mulching. The whole maize straw strip mulching could significantly increase the contribution of precipitation to potato water consumption, the highest contribution was found in SSM2 in different rainfall year types, 95.6% and 94.3% respectively in two years. Compared with CK, all mulching treatments reduced water consumption in the early growth stage (from sowing to tuber initiation), the whole maize straw strip mulching increased water consumption in the later growth stage (from starch accumulation to harvest), and the plastic film mulching increased water consumption in the middle growth stage (from tuber initiation to starch accumulation). The whole maize straw strip mulching and plastic film mulching increased drying tuber yield of potatoes by 27.9% and 24.2%, and water use efficiency increased by 23.1% and 19.3%. In conclusion, it can be seen that the whole maize straw strip mulching could significantly increase the soil water storage consumption during the full growth stage of potato, and improve the water consumption in the early and later growth stages, reduce the inefficient water consumption in dryland potato farms, and significantly improve drying tuber yield and water use efficiency of potato.

Abstract:In order to determine the effects of different straw returning amounts instead of some chemical fertilizers on yield, water and fertilizer use efficiency and nitrate accumulation characteristics of winter wheat, from 2018 to 2021, an experiment including four treatments, which were no straw returning (S0), half of straw returning (S1/2), total straw returning (S1) and two times straw returning (S2), was conducted in the Winter wheat planting region in loess dryland of southern Shanxi to study the effects of different straw returning amounts instead of some chemical fertilizers on yield formation of winter wheat, water and fertilizer use efficiency and soil nitrate-N residue. The results showed that on the basis of straw instead of 8.3%~31.9% N and 15.7%~63.2% P₂O₅ in winter wheat growing region of loess dryland, the yield of winter wheat generally increased with the increasing of straw returning amount, and in wet year, increasing the amount of straw returning could produce greater yield effect. The 3-year experiment showed that the average yield of winter wheat in the treatment of S2 was 17.5% (P<0.05), 10.4% (P<0.05) and 4.3% higher than that in S0, S1/2 and S1 treatment, respectively. The spike number per hectare of winter wheat was increased by returning straw to the field for three consecutive years. The average spike number of winter wheat in S2 treatment was higher 17.1% (P<0.05), 12.3% (P<0.05) and 3.6% higher than that in S0, S1/2 and S1 treatment, respectively, but there was no significant difference in Kernels number per spik and thousand kernel weight among different treatments. The 0-2 m soil water storage before seeding gradually increased with the increasing of straw returning amount to the field, and during the experiment, the average soil storage of S2 was 8.3% higher than that of S0 treatment (P<0.05). Water consumption also increased with the increasing of straw returning amount, and the average water consumption of S2 was 10.0% (P<0.05) higher than that of S0 treatment. There was no significant difference in water production efficiency among different treatments, with an average of 14.9 kg/(hm²·mm). Based on straw returning instead of partial fertilizer, the fertilizer use efficiency of winter wheat in loess dryland increased with the increasing of straw increasing amount, and the average nitrogen partial fertilizer productivity of N (PEP_N), agronomic efficiencies of N (AE_N), current recovery efficiencies of N (RE_N) and partial fertilizer productivity of P(PEP_P) of S2 treatment were 66.4%,155.8%,113.5% and 105.2% higher than those of S0 treatment, respectively. After three consecutive years of no straw returning, the soil nitrate-N residue of 2 m soil layer increased by 100.6% compared with that pre-sowing in 2018, and nitrate nitrogen accumulated in deep soil layer with downward leaching of water. The accumulation of nitrate nitrogen in 2 m soil layer of straw returning treatment was lower than that pre-sowing in 2018, and the residue of nitrate nitrogen in 2 m soil treated with S2 was the lowest, 244.8 kg/hm². Comprehensively considered, in the wheat planting region of loess Dryland in southern Shanxi, straw instead of 8.3%~31.9% N and 15.7%~63.2% P₂O₅ could increase soil moisture before sowing, reduce fertilizer residue, improve fertilizer use efficiency and obtain remarkable yield. Among the different treatments, the yield and water and fertilizer effect in the S2 treatment (average straw returning amount 7 477 kg/hm²) were the best. The results could provide theoretical basis for the prevention and control of non-point source pollution and the high-yield and high-efficiency green production of winter wheat in the dryland of wheat area.

Abstract:This experiment explored the effects of the application of biochar-based fertilizer on the pH and exchange capacity of the acidic soil in pomelo orchard, and the laboratory culture experiments were conducted for 60 days. In the experiment, no fertilizer control (CK), single application of urea (N), rice straw biochar-based fertilizer (BR) and bamboo biochar-based fertilizer (BB) at four dosage gradients (2.5, 5, 10 and 20 g/kg) were set up, and urea was applied in all treatments. The results showed that with the development of culture experiment, the soil pH value of BR and BB increased first and then decreased, and the contents of exchangeable acid and base ions increased. After 60 days of culture, the improving effects of BR and BB on soil pH, exchangeable acid, exchangeable aluminum, CEC and base saturation became more obvious with the increasing of the dosage of BR and BB, and the effect of BR was better than that of BB. Compared with N treatment, in the BR and BB treatments, the soil pH increased by 0.24~3.43 and 0.21~3.40 units, the exchangeable acid decreased by 45.55%~97.25% and 34.01%~96.70%, the exchangeable aluminum decreased by 46.95%~99.75% and 38.99%~99.00%, the soil CEC increased by 7.02%~170.74% and 6.52%~134.90%, the base saturation increased by 29.40%~51.61% and 32.08%~53.90%, respectively. The application of biochar-based fertilizer could improve the pH of acidic soil, reduce exchangeable acid, greatly reduce exchangeable aluminum, and improve soil CEC and base saturation. Therefore, the optimum amount of biochar-based fertilizer for the acid soil of pomelo orchard was about 2.5~5.0 g/kg, and the effect of rice straw biochar-based fertilizer was better than bamboo biochar-based fertilizer. This experiment provided a scientific basis for the treatment of the acidified soil in pomelo orchard.

Abstract:In order to investigate the effects of nitrogen addition on soil inorganic phosphorus forms in alpine wetland in arid area sensitive to global climate change Field in situ experiments were arranged in the well protected Bayinbuluk alpine wetland Swamp (S), Swamp meadow (SM) and Meadow (M). According to the nitrogen deposition of Bayinbuluk grassland, the nitrogen application rates of 0 (CK), 8 (N1) and 16(N2) kg·N/(hm²·a) were set to study the effect of short~term nitrogen addition on soil inorganic phosphorus forms in alpine wetland. Results showed that:(1) The average total phosphorus content under alpine wetland soil was 1.09 g/kg, and total inorganic phosphorus was 492.71 mg/kg, and total inorganic phosphorus accounted for 45.67% of total phosphorus on average. (2) The soil inorganic phosphorus of the 3 wetland types mainly exists in the form of Ca-P, and Ca₁₀-P is the main form of Ca-P, accounting for 50.27%~64.69% of the inorganic phosphorus content. The contents of soil Al-P and Fe-P in S area were significantly higher than those in SM and M area, the contents of Ca₂-P, Ca₈-P and O-P in SM area were significantly higher than those in S and M area, and the content of soil Ca₁₀-P in M area was significantly higher than those in S and SM area. (3) Nitrogen addition significantly affected the content of various forms of inorganic phosphorus in alpine wetland soil. Compared with CK, the content of soil Al-P in S and SM areas increased significantly by 9.92%~17.35%, and the content of Ca₈-P decreased significantly by 3.18%~9.36%. The content of soil Fe-P in S and M areas decreased significantly by 3.18%~9.36%. The content of soil Ca₂-P in s area decreased significantly by 10.31%. It is worth noting that under the addition of nitrogen, the soil O-P content of the 3 wetland types increased significantly, which was 21.83%~25.94% higher than that of CK. (4) RDA showed that soil pH, organic carbon, available nitrogen and available potassium were important factors affecting the form of inorganic phosphorus. In conclusion, there are significant differences in the content of inorganic phosphorus forms in different wetland types. Nitrogen addition significantly changes the content of inorganic phosphorus forms in the soil, mainly by increasing the content of difficult to use inorganic phosphorus (O-P) in the soil, so as to reduce the phosphorus supply potential of alpine wetland soil. This study is helpful to predict the changes of soil inorganic phosphorus in alpine wetlands under the background of continuous increase of nitrogen deposition.

Abstract:To investigate the evolution of planting years on soil carbon, nitrogen, phosphorus densities, and eco-chemical stoichiometry in Halaxylon ammodendron plantations, an age sequence of H. ammodendron stands (3, 6, 11 and 16 years) were selected in desert area of Jilantai, densities and stoichiometry characteristics of soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP) at soil depths of 0-20, 20-40, 40-60 cm were measured. The results showed that:(1) The contents and densities of SOC and TN in 0-60 cm soil increased with the increase of stand age, whereas the content and density of TP decreased with the increase of stand age. The SOC and TN contents and densities increased with the increase of soil depth in 3-year and 6-year plantations, and the content and density of TP were moving in exactly the opposite direction. The contents and densities of SOC, TN and TP increased with the increase of soil depth in 11-year and 16-year plantations. (2) The C:N, C:P and N:P ratios were 2.24~9.21, 1.59~7.05 and 0.56~0.81 with moderate spatial variation, and the coefficient of variation decreased with the stand age and soil depth, indicating that soil C:N, C:P and N:P ratios tended to remain stable. (3) Stand age, soil depth, and their interaction had a significant effect on SOC content, SOC density, C:N and C:P ratios, but had no significant effect on the N:P ratio and the contents and densities of TN and TP. (4) Soil porosity (STP) had a significant positive correlation with SOC density (P<0.05), indicating that the increase of soil porosity is helpful to increase SOC density and improve soil fertility. Plantation of H. ammodendron can improve soil fertility and soil environment in arid desert area.

Abstract:This study aimed to clarify the characteristics of soil nutrient accumulation and the potential risk to non-point pollution in the basin under eroded environment and long-term fertilizer application on farmland. In table-gully region of the Loess Plateau, soil and sediment samples were collected to analyze the size distribution and C, N, P contents in aggregates and the potential environmental risks in different erosion landforms from Tableland-Slope-Gully system (TSG) and Flatland-Washland-Waterstead system (FWW). The results showed that:(1) The highest weight percentage of small aggregate (< 63 μm) was found in low-lying areas, such as gully and waterstead, and FWW system was significantly higher than TSG system. (2) The contents of SOC, TN, TP, Olsen-P in Tableland were 8.49, 1.19, 1.23 g/kg and 51.80 mg/kg, respectively, which were 1.39, 1.49, 1.76 and 16.27 times of the recorded in the early 1980s; and 6.80 g/kg, 1.00 g/kg, 1.07 g/kg, 27.40 mg/kg for Flatland, respectively, which were 1.12, 1.25, 1.52 and 8.13 times of the recorded in the early 1980s. Moreover, soil phosphorus was accumulated most significantly among all soil nutrients. The SOC, TN, TP, Olsen-P contents in different aggregates showed the same decreasing pattern as follow > 250, 63~250, < 63 μm. (3) The SOC, TN, TP, Olsen-P were significantly reduced along the erosion topographic units under TSG and FWR systems; additionally, soil phosphorus contents in 63 μm aggregate at gully and waterstead plots increased to the value of tableland in the early 1980s. The characteristics of aggregates (< 250 μm) distribution and the mutation point of CaCl₂-P were prominent, and became the potential risk source for the water environment effected by the accumulation of soil nutrients under TSG and FWR systems. Therefore, preventing soil erosion and improving fertilization measures are the basis for ensuring high-quality development of the Yellow River basin.

Abstract:In order to explore the current status and influencing factors of soil organic matter in Northwest China, this paper used ArcGIS and geostatistics to study the spatial distribution of soil organic matter and its influencing factors in Northwest China. The results showed that:(1) The overall soil organic matter content in the study area is at a relatively low level, with grade 3 and below accounting for 68.94%, the organic matter variation range is 1.10~107.5 g/kg, and the average value is 20.13 g/kg; the organic matter is obtained by semivariance function model analysis. The optimal theoretical model was the spherical model. (2) By drawing the spatial distribution map of soil organic matter in the entire northwestern region, it could be seen that the organic matter content in the eastern part of the study area from Ningxia, northern Shaanxi to southern Gansu and southern Shaanxi shows a gradual increase. The central area of the Tarim Basin was distributed in concentric circles increasing to the boundary. The high-value areas of organic matter were distributed in the eastern part of Qinghai and the Tianshan Mountains in Xinjiang; the low-value areas were distributed in Ningxia, northern Shaanxi, and the Tarim Basin in Xinjiang. Such a distribution trend was somewhat similar to the distribution of large topographical areas in Northwest China. (3) There was a positive correlation between soil organic matter content and altitude and precipitation. (4) There were significant correlations between organic matter and soil types and land use patterns. The content of soil organic matter in grassland and woodland was significantly higher than that of cultivated land and unused land, but there was no significant difference between grassland and woodland. Altitude and precipitation were the main factors affecting organic matter, which can explain 49% of changes in soil organic matter. The results of this study will not only help qualitatively and quantitatively understand the spatial distribution of organic matter in Northwest China, but also provide a reference for soil texture for the construction of ecological agriculture and ecological environment protection in this region.

Abstract:In order to further understand the distribution characteristics and influencing factors of nitrate inorchard soil under farmers' production practice conditions, in this study, the production and management status of 28 orchards in Baoding area of Taihang Mountain piedmont plain in Hebei Province were investigated. The content, accumulation and main influencing factors of nitrate nitrogen in soil of 31vineyards and adjacent farmland from 0 to 200 cm were determined and analyzed. The results showed that the nitrogen application rate was relatively high in grape production, with an average of 297 kg/hm² per season. Excessive nutrient input resulted in nitrogen accumulation in the soil, and nitrate leaching was obvious in 0-200 cm soil layer, with the accumulation up to 1 555 kg/hm². Soil nitrate content varied at different tree ages, nitrogen application rates and irrigation amount, but all showed a tendency to increase with the increase of soil depth, and was significantly higher than that of farmland soil. The correlation analysis showed that the nitrate accumulation was positively correlated with the tree age and the nitrogen application rate, but negatively correlated with the irrigation amount. Path analysis showed that the nitrogen application rate was the most influential factor on soil nitrate accumulation, followed by the tree age and fertilization times, and finally the irrigation amount. The number of fertilization mainly affected nitrate accumulation indirectly through the effect of nitrogen application rate. In conclusion, the nitrogen surplus of vineyards in this region was serious, and a large amount of soil nitrate nitrogen was accumulated and leaching into the deep soil. The main factors affecting nitrate nitrogen accumulation in this region were nitrogen application rate, tree age and irrigation amount.

Abstract:In order to discuss the influence of different organic fertilizers substitute chemical fertilizer nitrogen on wheat yield and soil carbon and nitrogen components in winter wheat area of the Loess Plateau, provide theoretical basis for reducing the application of chemical nitrogen fertilizers, promote wheat quality and efficiency and sustainable agricultural green development in this area, the effects of different ratios of humic acid and organic fertilizers substitute chemical fertilizers on wheat yield and yield composition and soil carbon and nitrogen content were systematically studied. The experiment set up 7 experimental treatments in the winter wheat planting area of Shanxi Loess Plateau in 2019:100% chemical fertilizer N treatment (HF), 10% humic acid N+90% chemical fertilizer N (F1), 30% humic acid N+70% chemical fertilizer N (F3), 50% humic acid N+50% chemical fertilizer N (F5), 10% organic fertilizer N+90% chemical fertilizer N (Y1), 30% organic fertilizer N+70% chemical fertilizer N (Y3), 50% organic fertilizer N+50% chemical fertilizer N (Y5). The results showed that F3, F5, Y3, and Y5 treatments significantly improved 9.7%, 8.0%, 9.2% and 18.2% compared with HF, respectively. At the same time, Y5 significantly promoted the increase of the content of various active organic carbon and nitrogen components in the soil, and the increase range was between 36.8%~114.4% and 27.8%~105.4%; The content of soluble, water-soluble, microbial organic carbon, nitrogen and light organic carbon and nitrogen components under Y3 treatment was significantly increased by 21.1%~156.8% compared with HF. Compared with HF, the soluble, microbial, light organic carbon and the nitrogen content in the soil under F3 and F5 treatments were significantly increased by 25.4%~119.3%. At the same time, soluble organic carbon, microbial organic nitrogen, light group organic nitrogen had very significant positive correlations with grain yield. The soluble organic nitrogen could increase winter wheat yield by promoting the increase of ears per hectare. Total organic carbon, water-soluble organic carbon, and microbial organic nitrogen could increase yield by increasing the number of grains per spike. In conclusion, when 30%~50% organic fertilizer and humic acid were used for substitution of chemical fertilizer in winter wheat growing area of loess plateau, significant yield increase could be achieved, and the effects of active carbon and nitrogen components in soil could be improved. Among them, the 50% organic fertilizer replacement treatment has more significant effects on increasing yield and improving fertility, which is suitable for local promotion and application.

Abstract:In order to explore the effects of nitrogen reduction combined with slow release nitrogen fertilizer on soil enzyme activity and nitrogen absorption and utilization in cotton field, the effects of nitrogen reduction and different proportions of slow release nitrogen fertilizer on soil physical and chemical properties, enzyme activity, inorganic nitrogen content, nitrogen use efficiency and cotton yield were studied. The cotton variety "Xinluzao 64" was used in the experiment. Two nitrogen application methods were set up:The conventional total urea (T2) and slow release nitrogen fertilizer combined with urea (US). The combined application treatments were set at three levels according to the nitrogen application rate, namely, no nitrogen reduction, U_0.8S_0.2 (T3) and U_0.6S_0.4 (T4) (the subscript values refer to the proportion of urea and slow release fertilier in the total nitrogen); nitrogen reduction of 20%, U_0.6S_0.2 (T5) and U_0.4S_0.4 (T6); nitrogen reduction of 40%, U_0.4S_0.2 (T7) and U_0.2S_0.4 (T8); and no nitrogen application (T1) as the control, with a total of eight treatments. The soil physical and chemical properties, enzyme activity, inorganic nitrogen content, nitrogen content and yield of cotton at different growth stages were measured and analyzed, and the nitrogen use efficiency was calculated. The results showed that compared with the conventional total application of urea, the combined application of slow release nitrogen fertilizer could significantly increase the soil water content and total nitrogen content. Among them, the soil water content of T4 was the highest, which was 14.07%, 11.05%, 7.58%, 6.22% and 6.65% higher than that of T2 at the seedling stage, bud stage, flowering stage, boll stage and boll opening stage of cotton, respectively. The soil total nitrogen of T4 was significantly higher than that of T2 at flowering stage, reaching 1.24 g/kg. There was no significant difference in soil urease activity, sucrase activity, catalase activity, alkaline phosphatase activity and ammonium nitrate content between the treatments of T5, T6 and T2 at each growth stage. The soil urease activity and nitrate content in the mature stage of the treatments of T5 and T6 decreased by 28.20%, 26.40% and 11.13%, 8.32%, respectively, compared with the T4. In addition, the nitrogen use efficiencies of T5 and T6 were significantly higher than that of T2, by 62.09% and 62.43%, respectively. But there was no significant difference in yield and its components. In summary, the soil enzyme activity, inorganic nitrogen content and yield of the treatment with 20% nitrogen reduction combined with slow release nitrogen fertilizer (T5, T6) were not significantly different from those of the conventional (T2), and the nitrogen use efficiency was significantly higher, which could ensure the nitrogen supply in the whole growth period of cotton, avoid the nitrogen waste, and achieve the purposes of high yield and efficient utilization of nitrogen fertilizer.

Abstract:Desert steppe belongs to the arid type of grassland, with low nutrient content, fragile ecological environment and sensitive response to disturbance. The gradual increase of global nitrogen deposition changed the process of carbon and nitrogen transformation in the ecosystem and affected soil properties. In order to explore the effects of nitrogen addition on biological properties of soil in desert steppe, we took the desert steppe in Yanchi County as the research object and set up 5 nitrogen treatments as N0, N1, N2, N3 and N4.These treatments were set based on the pure nitrogenaddition levels of 0, 2.5, 5, 10 and 15 g/(m²·a), by applying with urea as nitrogen source. Results showed that:(1) The NH₄⁺-N content in 0-20 cm soil layer of desert steppe increased with the increase of nitrogen application rate, while the NO₃^--N content increased firstly and then decreased. In 0-10 cm soil layer, compared with N0, the NH₄⁺-N contents under N1, N2, N3 and N4 treatments were increased by 109.61%, 136.52%, 197.19% and 198.88%, respectively. The NO₃^--N content was the highest in N2 treatment, which was significantly higher than those in N0, N3 and N4 treatments (P<0.05). (2) Compared with N0, the MBN contents in 0-10 cm soil layer were significantly decreased by N1, N2, N3 and N4 treatments, which were reduced by 37.54%, 38.11%, 28.56% and 29.81%, respectively. (3) With the increase of nitrogen addition, the number of fungi in 0-10 cm soil layer of desert steppe gradually decreased, among treatments, the N0 and N1 were significantly higher than N3 and N4 (P<0.05). PCoA analysis showed that the microbial community structure in amoA and nirK zones of desert steppe soil were significantly changed by high nitrogen addition. Based on this research, the high nitrogen addition (N3, N4) had negative effects on soil microbial community in desert steppe, which were as follows:the number of fungi decreased, NO₃^--N content decreased, α diversity and dominant bacteria abundance of nitrogen-transforming microorganisms decreased, and the microbial community structure of nitrogen-transforming changed significantly.

Abstract:A field experiment was conducted in soda alkaline soil in the Hetao Irritated Area of Inner Mongolia to study the effect of different organic amendments on soil organic carbon (SOC) pool and chemical properties. Five treatments were designed as follows:traditional chemicals fertilizer only (CK), CK+biochar (BC), CK+cow dung (CD), CK+corn straw (SW), CK+goat manual (GM). Soil samples (0-30 cm depth) were collected after maize was harvested in 2019 and 2020, respectively, and the changes of SOC pool, labile organic carbon fractions, main saline and alkaline indexes and the relationship between them were analyzed. The results showed that compared with CK, the average increase of SOC in all organic amendment treatments were 22.7% and 17.2% in 2019 and 2020, respectively. The average increase in organic carbon stock (SOCs) were 22.9% and 18.2%, respectively. Labile organic carbon content increased in organic amendment treatments, among which the increase of CD and GM were higher than those in other treatments. CPMI increased by 53.8%~108.3% in organic amendment treatments compared with CK in 2019, and increased by 71.3%~144.1% in 2020 (P<0.05), and the promotive effect of CD and GM treatments was more obvious. As to the chemical properties, pH decreased apparently in four organic amendment treatments in 2020, exchangeable sodium percentage (ESP) decreased by 36.9% and 29.3% in BC and CD treatments, respectively (P < 0.05). Principal component analysis (PCA) showed that labile organic carbon fractions and ESP were the main factors which affected SOC content in soda alkaline soil. Cow dung and sheep manure had better effect on improving the quality of the organic carbon pool, and biochar had the most obvious effect on improving the chemical properties of soda alkaline soil.

Abstract:For the dual purposes of the straw resource utilization and strengthening the biomass carbon basal application, the rushes straw in the Dongting Lake was pyrolysised as biomass substrate. Using the coated and mix granulation technologies, the coated (CT) and mixed (MT) biochar fertilizers were prepared, with modified starch as adhesive, and bentonite, humic acid as supplementary. The ratios of biochar in fertilizers were 10% (T1), 15% (T2), 20% (T3), 25% (T4) and 30% (T5) respectively. All the fertilizers were screened considering the microstructure, nutrient release rate, particle size and compressive strength and other basic properties. A pot experiment was carried out with the screened biochar fertilizers (CT2, CT3, CT4 and MT1, MT2 and MT3), taking common compound fertilizer (NPK) and no fertilizer as the control (CK). The differences of ammonia volatilization and nitrogen leaching and loss in paddy soil were analyzed. The results showed that the larger ratio of biochar resulted in the compacted fertilizer structure and the lower cumulative nitrogen release rate. However, the excessive addition of biochar would cause the uneven particle size and non-standard compressive strength of fertilizer. For CT, 15%~25% biochar was suitable. For MT, 10%~20% biochar was suitable. Compared with NPK, CT2, CT3 and CT4 reduced ammonia volatilization accumulation by 12.95%, 27.96% and 23.82%, and ammonia volatilization loss rate by 16.56%, 35.67% and 30.57%, respectively, among which CT3 had the best effect. The cumulative amount of ammonia volatilization was reduced by 33.72%, 41.48% and 16.06% respectively in MT1, MT2 and MT3, and the loss of ammonia volatilization was reduced by 43.31%, 53.18% and 20.38% respectively. The average concentration of ammonium and nitrogen in surface water decreased by 20.74% (CT4) and 39.90% (MT2), respectively, compared with NPK. Total nitrogen and nitrate nitrogen concentration of MT decreased by 5.50% and 5.09% respectively in MT2, while the difference of CT was not significant. Compared with NPK, CT significantly reduced the average concentration of ammonium nitrogen and total nitrogen by 8.93%~14.00% and 8.84%~16.38%, respectively, while there was no significant difference in nitrate nitrogen treatments. The average concentrations of ammonium nitrogen, nitrate nitrogen and total nitrogen were reduced by 11.16%~12.42%, 3.22%~22.29% and 11.14%~15.86%, respectively. The higher the ratio of biochar was, the more obvious the emission reduction of biochar was. But the effect was not obvious when the excessive biochar was added. In general, the two methods could effectively reduce the loss of ammonia volatilization and reduce the loss risk of nitrogen. Among them, the CT with 20%~25% biochar content was the best, and the MT with 15% was the best.

Abstract:In order to find a feasible method to strengthen the phytoremediation of Cd contaminated soil, indoor culture experiments were conducted to study the effect of wood vinegar on the physical and chemical properties, enzyme activities, and Cd forms of calcareous heavy metal contaminated soils. Seven different dilution concentration treatments of wood vinegar were set up, and the soil physical and chemical properties, enzyme activities, Cd forms, and other indicators were measured and analyzed after adding wood vinegar and cultivation. The results showed that soil pH decreased gradually, and EC (except undiluted treatment) did not change significantly with increasing the concentration of wood vinegar. Comparing with CK, the content of soil organic matter, alkali hydrolyzable nitrogen, available phosphorus, and available potassium were increased by 0.35%~66.64%, 9.74%~96.10%, 31.71%~56.64% and 8.34%~30.87%. The soil enzyme activities (urease, invertase, and catalase activities) were increased significantly in 10-100 times dilution treatments, while soil enzyme activities were significantly inhibited in 5 times dilution and undiluted treatments (P<0.05). Except for the 5 times dilution treatment, the exchangeable Cd content in soil of other treatments was significantly higher than that of CK (P<0.05), increased by 24.69%~72.40%. Comparing with CK, the content of Cd in the carbonate-bound state, iron-manganese oxide state, and organic matter-bound state in all treatments were significantly increased by 6.67%~196.70%, 16.24%~80.09%, 31.51%~70.32%, and the residual Cd content was significantly reduced by 45.88~59.93% (P<0.05). In conclusion, adding appropriate concentration of wood vinegar to soil could increase soil nutrient content and enzyme activity, and promote the transformation of residual Cd in soil to other forms.

Abstract:In order to investigate the effect of vegetation restoration on soil pH, organic matter and main nutrient elements (nitrogen (N), phosphorus (P) and potassium (K)), taking the tidal flat as the control, different mangrove restoration modes (Aegiceras corniculatum, Kandelia obovate and mixed forest) in the Quanzhou Bay estuarine wetland were selected in this study. The results showed that soil pH and organic matter contents varied vertically under different restoration modes. Compared with the control, the restoration of mangrove significantly decreased soil pH (P<0.05), but increased soil organic matter contents (P<0.05). Under different restoration modes, the contents of alkali-hydrolyzable N, available P, available K, and total K increased with the increase of soil depth, while the contents of total P decreased with soil depth. Compared with the control, the mangrove restoration increased the contents of main soil nutrients (N, P, and K) in the surface soil, especially in the mixed forest (P<0.05). Our results indicated that different mangrove restoration modes have significant regulatory effects on soil physiochemical properties and nutrient dynamics. Among them, the mixed forest mode significantly improved soil nutrient dynamics through efficient utilization of aboveground and underground space, improving soil structure and quality, and increasing biomass and nutrient return, which is the optimal model for vegetation restoration in the estuarine area. The results can provide scientific reference for strengthening nutrient management and maintaining nutrient balance of estuarine mangrove wetland.

Abstract:Exploring the difference of particle size characteristics and hydrological effect of reconstructed soil under the different mixture ratio of abandoned slag and farmland soil is of great significance for improving the structural stability, efficient utilization of water resources and utilization of resources in the quarrying wasteland. Taking the abandoned residue of quarry and farmland soil as reconstruction matrix as research objects, the soil column simulation method was used to explore the difference of soil particle size structure and hydrological effect at different both volume ratios of 0:10 (C₁), 3:7 (C₂), 5:5 (C₃), 7:3 (C₄) and 10:0 (C₅) respectively. The results showed that:(1) The higher ratios of abandoned slag resulted in the greater specific gravity of sand, and the smaller of clay and silt. The maximum specific gravity of sand was 61.50%. The characteristic parameters of particle size, such as dispersion, skewness and kurtosis, decreased, increased and increased respectively, and the non-uniformity coefficient decreased significantly, the curvature coefficient fluctuated between 1 to 3, and the fractal dimension showed an insignificant decreasing trend. The soil structure changed in an unstable direction. (2) The increase of abandoned residue in mixed soil would lead to the increase of bulk density, the decrease of the number of capillary pores and total pores, the increase of the number of non-capillary pores, and the decrease of field water holding capacity, capillary water holding capacity and saturated water holding capacity. At the same time, the changes of initial infiltration, stable infiltration, average infiltration and cumulative infiltration basically showed an increasing trend. There was a fluctuating change in the used time of steady infiltration. Under different ratios, the soil infiltration model fitted well with R² ≥ 0.856, RRMSE ≤ 0.153. The grey correlation analysis showed that C₅ had the best infiltration performance. (3) The mixed soil with the abandoned residue:farmland soil of 3:7 gave the best performance in the particle size structure and hydrological effect.

Abstract:In order to investigate the influence of typical vegetation growth to the soil surface electrochemical properties of soil surface in different regions of loess Plateau, Taking three typical regions from south to north on the Loess Plateau (Yongshouliang, Fangta, Liudaogou) and two typical herbaceous plants (Artemisia gmelinii Web., Stipa bungeana Trin.) as research objects, and the abandoned land for one year as the control, the effect of two typical herbaceous plants on soil surface electrochemical properties and their spatial difference were analyzed based on collecting soil samples and measuring the soil surface electrochemical properties. The results showed that:(1) On the Loess Plateau, compared with the abandoned land, the growth of typical vegetation communities increased the contents of clay, silt and organic matter in soil, while decreased the content of pH, bulk density and sand. (2) In the same region, Soil cation exchange capacity and specific surface area increased and surface charge density and surface electric field intensity decreased with vegetation restoration, varying in the range of 6.69~24.34 cmol/kg, 7.29~182.29 m²/g, 0.08~2.04 C/m², 1.23~28.46 10⁸V/m. In different regions, with the influence of the same plant species, soil cation exchange capacity and specific surface area increased the most in Yongshouliang, and the rates of soil surface electrochemical properties change were the greatest in Liu daogou. It indicated that the influence of typical herbaceous plants on soil surface electrochemical properties has spatial heterogeneity, which may be attributed to the climate, soil texture, and other factors. (3) Silt content and organic matter content were the main contributors to soil surface electrochemical properties on the Loess Plateau due to their significant correlation and the change was the main reason for the change of soil electrochemical properties on the Loess Plateau, explaining 61.0% and 11.1% of the changes, respectively.

Abstract:In order to develop a new type of high efficiency and stability urea suitable for rice in black soil and loess, field pot tests were conducted to investigate effects of urea combined by biostimulant laminarin and different biochemical inhibitors on rice in black soil and loess. In this study, blank (CK) and urea (N) were set as controls, and laminarin (L), N-butyl thiophosphate-triamine (NBPT), 3,4-dimethyl-pyrazolate phosphate (DMPP), and laminarin were respectively combined with two biochemical inhibitors to urea fertilizer to form five treatments, nitrogen transformation characteristics, rice growth index, yield and apparent utilization rate of nitrogen fertilizer of different high efficiency and stability urea fertilizers in black soil and loess were studied. The results showed that the addition of laminarin could inhibit soil nitrification to a certain extent, total biomass of rice in black soil and loess increased by 13.88% and 1.21%, grain yield increased by 42.18% and 25.83%, apparent utilization rate of nitrogen also increased. Laminarin and NBPT had a good synergistic effect on soil nitrification inhibition, compared with NBPT alone, total biomass in black soil and loess decreased by 6.87% and 1.30%, grain yield decreased by 8.15% and 4.11%, apparent utilization rate of nitrogen also decreased. Compared with DMPP alone, the addition of laminarin could promote the growth of rice, total biomass and grain yield increased by 0.63% and 2.64% in loess, nitrogen uptake and apparent utilization rate of nitrogen were also increased, however the total biomass and grain yield decreased by 10.52%, 1.50% in black soil, and nitrogen uptake and apparent utilization rate of nitrogen were also decreased, the combination of laminarin and DMPP had a negative effect in black soil. The addition of laminarin and DMPP is recommended for urea fertilizer application on rice in loess areas, and will improve rice yield and apparent utilization rate of nitrogen.