Abstract:Informatization Supervision of soil and water conservation for production and construction projects is an important responsibility and key work for strong supervision of soil and water conservation and protection of ecological environment all over the country, the supervision work and the technical method have met the bottleneck restriction such as the heavy workload of artificial check, the difficulty of identification and analysis, the low efficiency of fast and accurate supervision and so on. Based on the analysis of the spectral information and texture structure of remote sensing image, the technology of image feature enhancement, assisted by large data, such as land use of various projects, earth and rock excavation, amount of waste, construction period, degree of influence of soil erosion and water loss, etc. after comprehensive, detailed and intelligent deep learning, and at the same time using relevant information and big data from development and reform, land and resources, urban and rural construction, environmental protection, forestry, water management, transportation, electric power and other departments, through related analysis, realization of intelligent identification of production and construction projects. Through the intelligent correlation analysis of the special necessary facilities of the project, the relevant map spots of the same project to merges. Apply High and new technologies such as artificial intelligence, big data, cloud computing, Internet of things, we will improve the rate of intelligent and accurate discrimination against illegal and illegal activities, such as "construction before approval", "Put into production before acceptance check" and "discard before approval". In order to improve the efficiency and effectiveness of precise supervision, it is necessary to strengthen the intelligent support of big data, the intelligent tracking of key supervision projects, and the supervision of key issues of soil erosion and water loss hazards in important sensitive areas of soil and water conservation, detailed monitoring of key soil and water conservation measures during the three periods of project start-up, construction process and project completion, so as to provide more timely and effective support for soil and water conservation inspection, supervision and law enforcement, and comprehensively enhance the supervision efficiency and level, to promote ecological priority and green development, to provide important support and guarantee for the country's high-quality development.

Abstract:Vegetation cover can effectively protect the ground surface, inhibit the process of runoff and sediment production, and then affect the process of nutrient migration on slopes. Typical Bothriochloa ischaemum and Artemisia gmelini grasslands in the Loess Plateau were selected and simulated rainfall experiments (rain intensity 60 mm/h, duration 60 min, slope 15°) were used to study the slope runoff and sediment nutrient characteristics under different coverage conditions (10%, 20%, 30%, 45%, 60%, 80%). The results showed that: (1) The contents of soil organic matter, total nitrogen and total phosphorus increased linearly with the increase of coverage (R²≥0.63). Compared with Artemisia gmelini plot, the contents of soil organic matter and total phosphorus in Bothriochloa ischaemum plot increased by 28.8%~107.1% and 10.6%~25.0% respectively, while the contents of total nitrogen decreased by 2.6%~42.5%. (2) With the increase of vegetation coverage, the concentrations of organic matter, total nitrogen and total phosphorus in runoff decreased by 0.6%~63.7%, but there was no significant difference between the two species (P>0.05). The amount of organic matter, total nitrogen and total phosphorus in runoff decreased by 1.9%~83.9%, and when vegetation coverage was ≥20%, the amount of organic matter, total nitrogen and total phosphorus in runoff in Bothriochloa ischaemum sample decreased by 28.4%~66.4%, 10.7%~55.8% and 3.3%~64.7%, respectively, compared with Artemisia gmelini sample. (3) The contents of organic matter, total nitrogen and total phosphorus in the sediment decreased by -59.5%~65.1% with the increase of vegetation coverage, with an average decrease of 5.8%. The nutrients amount of the sediment Bothriochloa ischaemum were generally lower than those of Artemisia gmelini. The amount of Bothriochloa ischaemum and Artemisia gmelini sediment organic matter, total nitrogen and total phosphorus showed an exponential function (R²≥0.78) and a downward trend with the increase in coverage, respectively. The nutrients amount in the sediment were significantly reduced by 69.9%~99.3%. (4) The total organic matter, total nitrogen and total phosphorus of runoff sediment in Bothriochloa ischaemum and Artemisia gmelini showed an exponential function (R²≥0.53) and a decreasing trend with the increase of vegetation coverage, respectively. When the vegetation coverage was ≥45%, the total organic matter, total nitrogen and total phosphorus in Bothriochloa ischaemum decreased by 33.7%~71.8%, 50.1%~53.6% and 48.1%~64.3%, respectively, compared with Artemisia gmelini plots. (5) The enrichment ratios of soil organic matter, total nitrogen and total phosphorus of two typical vegetation decreased linearly with the increase of coverage (R²≥0.56). The migration of soil organic matter and total phosphorus of two typical vegetations occurred mainly in sediment, and the migration of soil total nitrogen occurred mainly in runoff. The research results provide a theoretical reference for the effect of vegetation coverage on the nutrients migration mechanism of slopes.

Abstract:In order to study the influence of engineering disturbance on the soil anti-erodibility and anti-scourability of loess, taking Beishan, Chengguan District, Lanzhou City as the study area, the undisturbed soils were sampled from four plots: 1-year filled plot (T1a), 5-year filled plot (T5a), 7-year dug plot (W7a) and natural grassland plot (C). In the laboratory, the dry-wet sieve method was used to determine the soil aggregate related indicators to study the soil anti-erodibility, and the anti-scour trough was used to study the soil anti-scourability, and the factors affecting the soil anti-erodibility and anti-scourability were analyzed. The results showed that the mean weight diameter of soil water-stable aggregates (MWD_w) and the proportion of aggregates>0.25 mm (w_(δ>0.25)w) of the surface layer (0—10 cm) of each sample surface showed C>W7a>T5a>T1a. The soil percentage of aggregates destruction (PAD) showed T1a>T5a>W7a>C. The average of soil water stable aggregates fractal dimension (D_w) in the surface layer of dug and filled plots was 2.82, the D_w of C plot was 2.74. The anti-erodibility of the surface layer soil of the C was significantly stronger than those of the dug and filled sites. The MWD_w and w_(δ>0.25)w of the middle and lower soil (10—20 cm and 20—30 cm) of the T5a and W7a plots were significantly lower than those of the surface layer soil. The surface soil anti-erosion coefficients of each sample showed W7a>C>T5a>T1a, and the values of W7a and C sample plots were relatively close. Soil electrical conductivity, organic matter and root system were the main factors affecting soil anti-erodibility and soil anti-scourability. In addition, soil biological crusts could also affect soil anti-scourability. These factors are closely related to the shelving years of dug and filled plots. This means, these factors gradually change as the shelving time of dug and filled plots increases, which is beneficial to the increase of MWD_w and w_(δ>0.25)w,and the decrease of PAD of disturbed soil, and the scouring intensity of surface soil is close to that of natural grassland. Engineering disturbance would significantly reduce the soil anti-erodibility and soil anti-scourability of loess, and necessary water and soil conservation measures should be taken to reduce the risk of soil erosion.

Abstract:Rainfall is one of the main dynamic factors that cause soil water erosion. In order to explore the effects of different levels of rainfall on the characteristics of soil water erosion in Shaoguan City, the daily rainfall data of Shaoguan City from 1951 to 2018 were selected, the daily rainfall erosivity model was used to calculate the rainfall erosivity, and the variation coefficient and trend coefficient were used to analyze the changes of rainfall erosivity indifferent time scales. The results indicated that: (1) The average annual rainfall erosivity of Shaoguan City in 68 years was 9 314 (MJ·mm)/(hm²·h·a), and the variation coefficient was 0.29, which was a medium variation. (2) The annual rainfall, rainfall days, erosive rainfall and rainfall days showed an upward trend, while the non-erosive rainfall and rainfall days showed a downward trend, and heavy rainfall volume and rainstorm erosivity showed an obvious upward trend, indicating that rainfall was more concentrated and rainfall erosivity increased in Shaoguan City. (3) The proportion of rainfall days and rainfall over heavy rain to total rainfall days and total rainfall was 43.91% and 51.15%, respectively, while the proportion of rainfall erosivity caused by heavy rain to total rainfall erosivity was 77.05%. The results could provide reference for soil erosion monitoring and soil and water conservation in Shaoguan City.

Abstract:Slope topography changes are the important factors that affect the characteristics of eroded sediment particles. A deep understanding of the relationship between topographic factors and eroded sediment particle size composition and sorting characteristics is the basis for studying slope soil erosion dynamics. In this study, field rainfall experiments and particle size analysis experiments were used, combined with ArcGIS system identification and extraction to obtain topographic factor data, to study the characteristics of erosion and sediment particles in the low mountain and hilly areas and their relationship with topographic factors. The results showed that: (1) Under the test conditions, the total contents of clay and silt particles in the eroded sediment were much higher than that of sand particles. The content of coarse particles had a significant positive correlation with the slope factor (p<0.01), and a significantly negative correlation (p<0.05) with the accumulation of depressions. (2) In this study, the average mass diameter (MWD) of the test plot varied from 0.031 to 0.164 mm, and the fractal dimension (D) varied from 2.021 to 2.778. The determining factor of the MWD and D size was the content of coarse particles. From an overall point of view, rain intensity had a significant impact on the sediment particle sorting characteristic parameters. MWD increased with the increase of rain intensities, and D decreased with the increase of rain intensities. The two have a significant correlation with the slope factor (p<0.05). (3) The regression results show that the MWD and D had the significant power function relationships with the slope factor and the accumulation of depressions (R²>0.5). Combining the results of the correlation study, the slope factor was suggested as the preferred choice for the study of erosion and sediment particle size models. This study aimed to reveal the effect mechanism of topographical factors on slope erosion and sediment particles, and provide a scientific reference for the construction of soil erosion models.

Abstract:In order to reduce the staining method of slope flow velocity measurement error, improve the dyeing method of measurement accuracy, according to the characteristics of color change caused by the diffusion of dye tracer in water, a shallow water flow velocity measurement system based on photoelectric sensor technology was developed by combining diffuse reflection analog photoelectric color sensor and data acquisition card to collect signals, and wavelet transform was used to denoise the signal. Taking the discharge method as a reference, the optimal data acquisition distance of the sensor of the system was determined to be 0.6~0.8 m. When the sensor data acquisition distance was 0.7 m, the minimum relative error of the measured data of the system was only 0.48%, and the coefficient of variation was less than 15%. Compared with the dye tracing technique, the fitting coefficient of the system and the discharge method was more than 0.90, which is greater than the dye tracing technique's coefficient of 0.75. The results show that the measuring system is superior to the dye tracing technique and can be used in the experimental study of shallow overland flows.

Abstract:The effective implementation of the "grain-for-green" project has rapidly restored vegetation on the Loess Plateau, which will inevitably trigger the changes in plant roots and soil physical and chemical properties, and further affect the shear strength of root-soil system. To investigate the potential impacts of vegetation restoration age on shear strength of root-soil system, six abandoned farmlands with different restoration age (5, 12, 20, 27, 37 and 46 years) and a slope farmland were selected as testing sites in Zhifanggou small watershed in Ansai, Shaanxi province. The in-situ shear tests were conducted in five different soil depths (0—10, 10—20, 20—30, 30—40, 40—50 cm), and root characteristics and soil physical and chemical properties were measured simultaneously. The results showed that the average shear strength of 0—50 cm soil layers increased as a sigmoid curve from 51.80 J/m² to 124.01 J/m² with the increasing of vegetation restoration age. Compared with slope farmland, the shear strength of root-soil system increased by 2.5%, 54.6%, 48.7%, 86.5%, 139.4% and 129.3% for abandoned farmlands with different restoration ages, respectively. The root density decreased significantly with the increasing of soil depth in the abandoned farmlands, which induced decrease in the shear strength of root-soil system. The shear strength of root-soil system was logarithmically positively correlated with organic matter content, root length density and root mass density, and linearly positively correlated with aggregate stability and root density. Path analysis showed that aggregate stability, root mass density and organic matter content were the key factors affecting the shear strength of root-soil system. The results could provide a theoretical basis for evaluating water and soil conservation benefit and ecological service functions of vegetation restoration, and revealing the dynamic mechanism of changes in shear strength of root-soil system with the vegetation restoration age.

Abstract:Studies on soil nutrient responses to soil erosion and deposition at watershed scale can provide important scientific basis for soil erosion risk assessment. The Binzhou watershed, a typical thin layer Mollisol region in Northeast China, was selected as the study area. Based on soil sample collection and laboratory analysis, and combined with ¹³⁷Cs tracer method, the soil nutrient contents between erosion-dominant sites and deposition-dominant sites were compared, and the spatial distribution of soil nutrients at watershed scale and their responses to soil erosion and deposition rates were explicated. The results showed that soil erosion-deposition processes obviously affected soil nutrient contents at watershed scale. Comparing with soil deposition-dominant sites, the contents of soil organic carbon (SOC), total nitrogen (TN), NO₃—N and available phosphorus (AP) at the soil erosion-dominant sites were reduced by 27.4%, 21.1%,29.2% and 54.1%, respectively. Meanwhile, the SOC and TN contents between both in soil deposition and erosion sites had extremely significant differences, and the AP contents at both sites had significant difference; while there was no significant difference in NO₃—N contents at the both sites. The contents of SOC, TN and AP had significant negative correlations with soil erosion rates. Moreover, the spatial distributions of SOC and TN contents at the watershed scale were opposite to the spatial distribution of soil erosion rate, which indicated that soil erosion was the key driving factor for soil quality degradation in the study area.

Abstract:In order to explore the effects of two types of ecological projects (Sophora moorcroftiana (Benth.) Baker shrub and Populus alba L. plantation) on the water holding capacity of sandy land in the Yarlung Zangbo River Valley terraces, the water holding capacity and soil physicochemical properties of 0—30 cm soil layer in 6, 12 and 30 years ecological projects plots in this area were measured. The soil quality indexes of aeolian sandy lands in different projects areas were calculated by fuzzy mathematics method. The influencing factors of water holding capacity of aeolian sandy lands were analyzed, and the main influencing factors were determined by multiple stepwise regression method. The results showed that: (1) The saturated water holding capacity, capillary water holding capacity and field water holding capacity of 0—10 cm soil layer of S. moorcroftiana (Benth.) Baker shrub and P. alba L. plantation increased by 5.81% to 9.19% and 51.47% to 71.48% from 6 to 30 years, respectively, and each water holding index of P. alba L. plantation was 1.02 to 1.60 times of that of S. moorcroftiana (Benth.) Baker shrub. (2) P. alba L. plantation promoted better structural changes in mechanical particle, bulk density, porosity and had higher nutrient contents such as organic matter and total nitrogen in the 0—10 cm soil layer of aeolian sandy lands than S. moorcroftiana (Benth.) Baker shrub. With the increase of implementation years, the overall change of the above soil indicators in the 0—10 cm soil layer of S. moorcroftiana (Benth.) Baker shrub was best in 12 years, while that of P. alba L. plantation was 30 years>10 years>6 years. (3) The average value of soil quality index of the 0—30 cm soil layer of the two ecological projects showed an increasing trend with the increasing of implementation years. The results of correlation analysis and multiple stepwise regression analysis showed that the water holding capacity of sand lands was significantly correlated with the mechanical particle, bulk density, porosity, organic matter, total nitrogen and total phosphorus, and the main influencing factors were capillary porosity, total nitrogen and very fine sand. In conclusion, P. alba L. plantation, as a local introduced tree species, had better effect on improving water holding capacity and sustainability than native shrub of S. moorcroftiana (Benth.) Baker, which could promote the restoration of aeolian sandy lands. The research results could provide data reference for understanding the change of regional sand ecohydrological function and ecological projects construction.

Abstract:Tamarix chinensis sand dunes are specific bio-geographical landscape in Gurbantunggut Desert, which play an important role in maintaining the stability of regional ecological environment. Based on field investigation and indoor analysis, the soil grain size characteristics of 0—500 cm soil layer in T. chinensis sand dunes in the southwest of Gurbantonggut Desert were analyzed. The results showed that: (1) Soil grain size composition of T. chinensis sand dunes was dominated by silt and very fine sand, and the content was more than 80%, furthermore, the content of soil particle below 50 μm accounted for more than 57%. (2) With the increasing soil depth, the content of clay and silt, average particle size and sorting coefficient showed the trend of increase-decrease-increase. In general, the content of very fine sand and fine sand,skewness and kurtosis showed the trend of decrease-increase-decrease. The overall sorting ability of soil was poor. Kurtosis was generally mesokurtic peak, and the grain size distribution was positive skewness. The fractal dimension and average particle size were significantly positively correlated with clay and silt, and negatively correlated with very fine sand and fine sand, indicating that fractal dimension and average particle size could better reflect the characteristics of soil particle size composition of T. chinensis sand dunes. (3) Soil particle size of T. chinensis sand dunes was affected by soil water content, pH, total phosphorus, organic matter and electrical conductivity. The average particle size and fractal dimension could well reflect the characteristics of soil particle distribution in the profile of T. chinensis sand dunes, and soil grain size composition of T. chinensis sand dunes was a potential material basis for soil formation in the desert-oasis transition zone.

Abstract:The research on the temporal and spatial change of soil erosion in the upper reaches of the Yellow River is of great significance to maintain the ecosystem service function and protect the water tower in the upper reaches of the Yellow River. Taking Huangshui watershed in the upper reaches of the Yellow River as the research area, based on the Revised Universal Soil Loss Equation (RUSLE), the spatial and temporal variation of soil erosion in Huangshui watershed from 2000 to 2015 were quantitatively evaluated, and the spatial variation of soil erosion with or without terraced fields were analyzed, so as to quantify the impact of terrace construction on slope soil erosion. The results showed that from 2000 to 2015, the soil erosion intensity in the Huangshui watershed showed a decreasing trend, and the erosion modulus decreased from 1 183 t/(km²·a) to 940 t/(km²·a), with a decrease rate of 20.54%. The soil erosion intensities on different land use types and different slopes all decreased, among which the maximum reduction was 20.58% on cultivated land. The erosion modulus of the slope with 15° to 20° gradient decreased most significantly by 23.11%. Through scenario simulation with or without terrace measures, it was found that the soil erosion modulus in 2015 in the Huangshui watershed decreased from 940 t/(km²·a) to 837 t/(km²·a) with terraced fields, with a decrease of 11.00%. The research results could provide a scientific basis for the prevention and control of soil erosion and the protection of ecological environment of the basin.

Abstract:In order to clarify the characteristics of soil priority path and the influence of root on the formation of soil priority path under the cultivation of Pu'er tea in southern Yunnan, we took the typical Pu'er tea producing areas as the research object and shrub grassland as the control, and the relationship between root characteristics of Pu'er tea tree and soil priority path was quantitatively analyzed based on the staining tracer method and image processing technology, and the influence of root on the formation of soil priority path was explained. The results showed that: (1) With the increasing of soil depth, the width of dyeing path in tea field and shrub grassland decreased in different extent. The connectivity of priority path in tea field was worse than that in shrub grassland, and the development degree of priority path in tea field was less than that in shrub grassland. (2) The root mainly distributed in the surface of soil, with the increasing of soil depth, root weight density and root length density of different diameter classes all decreased, and the root length density of diameter class ≤1 mm contributed the most, reaching 84.08%. (3) The width of staining path was significantly correlated with root weight density, root length density of diameter class ≤1 mm and 1~3 mm (P<0.05). The width of staining path of shrub grassland was significantly correlated with root length density of diameter class ≤1 mm (P<0.01), and the correlation coefficient was 0.986. (4) The staining path width had a better fitting effect with the root length density of diameter class ≤1 mm, and the R² was as high as 0.970 6. The fine roots with diameter class ≤1 mm had a greater influence on the formation of priority path. Root is one of the important factors that affect soil priority path. The research on the influence of Pu'er tea tree root on soil priority path in southern Yunnan can provide some scientific basis for soil erosion control and water resources management.

Abstract:Evapotranspiration (ET) plays an important role in agricultural irrigation and water resources management. ET can be accurately estimated by the FAO-Penman-Monteith method (ET_FPM). The ET_FPM method is the standard reference method for ET estimation. This method needs to provide more detailed meteorological data. For the estimation of ET, it is necessary to find an alternative method that uses less input data without affecting the accuracy of the prediction. This study used 5 radiation-based models, including Makkink (ET_MAK), Priestley and Taylor (ET_PT), Abtew (ET_ABT), Jensen-Haise (ET_JH), McGuinness and Bordne (ET_MB), and 3 temperature-based models, including Hargreaves and Samani (ET_HS), Hamon (ET_HAM) and Linacre (ET_LIN), and a model Penman (ET_PEN) based on aerodynamics. Using the long-term data from 6 meteorological and hydrological stations in the Hancang River Basin, the selected model were evaluated by comparing them with ET_FPM on a monthly and growing season scale. The statistical analysis revealed that ET_JH and ET_HAM are the best forecasting methods for monthly ET in 67% and 33% of the study area respectively. In the study area, the radiation-based methods were better than temperature-based methods. The cumulative values of ET during the vegetation growth periods showed that the Jensen-Haise method and Hamon method perform best in the warm season and autumn and winter growing seasons, while the best prediction method for the spring growing season only included the Jensen-Haise method. However, divergence between estimations of the best alternative methods and the reference method showed that the best ET alternative methods might be unreliable in some regions. Accordingly, the spatiotemporal variability in predictability performance of ET models should be taken into account prior to use.

Abstract:The objective of this paper is to reveal the influence of human trampling on infiltration characteristics of various forest soils in karst mountain lands. Inside the forest, central areas of forest path, edge areas of forest path, and bare lands were selected as test plots. The unsaturated hydraulic conductivity (K₉, K₆, K₃, K_0.5), saturated hydraulic conductivity K_s, contribution rate of water flow and Gardner α were determined via disc infiltrometers under different pressure heads (-0.5, -3, -6, -9 cm). The dye coverage (DC), uniform penetration depth (UniFr) and preferential flow percentage (PF-fr) were estimated through in-situ dye tracer experiments and digital image processing. Based on a series of dye tracer experiments, the effects of human trampling on the soil preferential flow were analyzed. The results showed that the K_S values in central areas of forest path (45.800×10^-3 cm/min) was 55% lower than that of the inside the forest (101.000×10^-3 cm/min). The drastic reduction in values of the Gardner α and the soil pores number explained the reduce of soil infiltration capacity in forest paths. The percentage of preferential flow in the center areas of the forest path (71.955%) was significantly higher than that in the forest lands (36.734%), and this result indicated that the soil preferential flow was largely enhanced by trampling activities from humanity. The average contribution rate of water flow exceeded 95% in soil macro-pores under the four levels of artificial trampling. The soil infiltration channels were mainly macro-pores in karst mountain forests. Soil infiltration capacity and soil preferential flow can be effectively enhanced and inhibited by forest vegetation cover. These results can provide an experimental basis to set up a negative list for economic development in karst mountain lands.

Abstract:In view of the contradiction between the declining of groundwater table and the demand of high yield, to clarify the yield and water use efficiency (WUE) of wheat-maize double cropping system in the different precipitation years under different irrigation scenarios, the results would provide important scientific decision-making basis to balance the sustainable of groundwater utilization and grain production. Based on the field experiment data, the crop biomass, LAI and soil water content under different irrigation treatments, the genetic parameters and parameters related with the soil water were calibrated and validated by using long-term meteorological data in the APSIM wheat-maize cropping model. Using the calibrated and validated APSIM model, the water deficit index (CWDI) was analyzed in different precipitation years, the crop yield, water use efficiency (WUE), and the irrigation water use efficiency (IWUE) of 8 irrigation scenarios under the dry, medium, and rainy years were simulated. The results showed that CWDI was high in each growth stage of wheat in different precipitation years, which indicated that water requirement of wheat in dry, medium, and rainy years was much higher than precipitation, especially from jointing to maturity stage. Maize was not affected by drought stress before tasseling, but was in medium or severe drought after tasseling. Considering both yield and water use efficiency in this region, when the total irrigation water was 225 mm (75 mm at wheat sowing + 75 mm at jointing + 75 mm at flowering), the total yield was high, and the WUE and IWUE was maximal. The average total yield and WUE were 17 357.6 kg/hm² and 29.6 kg/(hm²·mm) in dry years, were 18 827.9 kg/hm² and 25.9 kg/(hm²·mm) in the medium years, and were 19 685.2 kg/hm² and 25.8 kg/(hm²· mm) in rainy years. Under this irrigation scenario, the yields of wheat and maize were high, and the WUE were also at the high level. So, this irrigation scenario was an important irrigation strategy and practice for water-grain trade-off in this region.

Abstract:Ecosystem services assessments determine regional sustainable development and are critical to human well-being. This study took the Loess Plateau as the research area, based on the CASA, InVEST and RUSLE model, combined with the data of land use types, normalized vegetation index, meteorology and so on, analyzed the spatial and temporal distribution characteristics of the three key ecosystem services (NPP, soil conservation, and water conservation) in 2000, 2005, 2010 and 2015; and identified the hot spots of three ecosystem services, analyzed the trade-offs between different ecosystem services on the Loess Plateau and different climatic regions (arid, semi-arid, plateau and semi-humid climate zone) based on the correlation coefficient method. The results showed: (1) From 2000 to 2015, land use types in the Loess Plateau region changed drastically, among which forest land (2.8%) and construction land (43.1%) increased significantly, and cultivated land (-2.7%) decreased significantly. (2) From 2000 to 2015, all the average unit area of net primary productivity (NPP), water conservation and soil conservation showed an increasing trend, increased by 14.1%, 5.3% and 101.3% respectively. (3) The areas occupied by the four types of hotspots in the Loess Plateau (non-hotspots, first-type hotspots, second-type hotspots, and third-type hotspots) had not changed significantly, but the distribution had the obvious zonal distribution, that was non-hotspots, first-class hotspots, second-class hotspots, and third-class hot spots respectively from northwest to southeast. (4) Across the Loess Plateau, there was a synergistic relationship between soil conservation and NPP, soil conservation and water conservation. And there was a trade-off between NPP and water conservation. However, soil conservation and water conservation was trade-off in semi-arid and semi-humid regions, and the relationship between NPP and water conservation also was trade-off in arid and semi-arid regions. In order to promote the sustainable management of regional ecosystems, the relationships between ecosystem services should be considered in the land planning process, and trade-offs should be minimized and synergies should be maximized.

Abstract:Incorporated wheat straw returning can change soil properties, which in turn affects soil erosion resistance. In order to clarify the response of soil erosion resistance after incorporated wheat straw returning to the field, this study took cinnamon soil in the earth-rocky mountain areas of northern China as research object. The orthogonal design table of L₉ (3⁴) was used to arrange the treatments with factors of straw length (2, 5, 8 cm), straw returning amount (2 000, 4 000, 8 000 kg/hm²), pure nitrogen application amount (100, 140, 180 kg/hm²), and pure polyphenol application amount (0, 40, 80 kg/hm²) at three gradients. Totally, the study had 10 treatments including a controlled trial. The soil erodibility and critical shear stress were measured by the JET equipment. The results showed that the soil critical shear stress of all returning treatments increased compared with the controlled trial, but the difference was not significant (P>0.05). The effect of nitrogen fertilizer on the soil critical shear stress was significant, and the critical shear stress firstly increased and then decreased with the increase of nitrogen fertilizer amount. The straw length, straw returning amount, nitrogen fertilizer, and polyphenol had significant influence on soil erodibility. The contribution rates of straw returning and polyphenol were 50.61% and 23.84%, with negative and positive effects, respectively. Under the condition of incorporated wheat straw returning to the field, the soil erodibility could be fitted linearly with soil saturated water content and >0.25 mm aggregate content (R²=0.81, P<0.01). The change of critical shear stress could be simulated with the content of water-stable aggregate of >0.25 mm and soil erodibility (R²=0.76, P<0.05). The results maybe helpful to understand the change and mechanism of soil erosion resistance after incorporated straw returning and provide data for soil erosion modeling.

Abstract:The input of phosphorus (P) along with stemflow and throughfall is an important supplement for P loss in subtropical forest ecosystems, but the dynamics of these processes in different type of forests remain elusive. Here, based on field monitoring experiments in middle subtropical Cunninghamia lanceolata (Lamb.) Hook. Plantations and Castanopsis carlesii (Hemsl.) Hay. Secondary forests from June 2015 to August 2018, we assessed P concentrations of stemflow and throughfall among different forest types and seasons, and the associated controlling factors. The results showed that P concentrations of stemflow and throughfall in C. lanceolata plantations varied from 0.002 to 0.026 and from 0.003 to 0.024 mg/L, respectively, and those in C. carlesii secondary forests varied from 0.003 to 0.024 and from 0.003 to 0.031 mg/L, respectively, P concentrations of stemflow and throughfall varied significantly between forest types in summer. Stemflow P concentrations were higher in summer than that in winter, regardless of forest type. Throughfall P concentrations were higher during summer and autumn in C. carlesii secondary forests, but did not differ among seasons in C. lanceolata plantations. Rainfall amount of stemflow in both forest types significantly varied among different seasons, with an average of higher stemflow but similar throughfall in C. carlesiisecondary forests compared with C. lanceolata plantations. P concentrations were negatively correlated with water amounts of both stemflow and throughfall in C. lanceolata plantations, but positive correlations were found in C. carlesii secondary forests. Our results suggested that forest type that was represented by canopy structure and phenology features was an important controlling factor affecting rainfall P distribution in subtropical forest ecosystems, which could provide useful basal data for better understanding the dynamics of P along with hydrology process in forest ecosystems.

Abstract:In order to explore the litter characteristics of different vegetation types in the engineering accumulation, the water holding capacity and retention capacity of the engineering accumulation vegetation, litter of the native vegetation and 0—20 cm soil layer were studied by indoor immersion method and cutting ring method respectively. The results showed that: (1) There were significant differences in litter’sthickness and volume among different vegetation types (P<0.05). The litter’sthickness of primary arbor forests, arbor forests, shrub forests, and grassland were 3.76, 2.89, 2.67, 1.23 cm, and the litter’s volume amount were 5.95, 3.86, 3.19, 0.65 t/hm². The thickness and volume of the undecomposed layer were larger than that of semi-decomposed layer. (2) The soil bulk density and capillary porosity of different vegetation types ranged from 1.19 g/cm³ to 1.25 g/cm³ and 41.58% to 46.13% respectively. The soil bulk density of the primary arbor forests was lower than that of arbor forests, while the soil capillary porosity was higher than that of arbor forests. The order of soil capillary porosity of different vegetation types in the accumulation body was grassland, shrubs forests, and arbor forests. (3) The maximum soil water holding capacity and capillary water holding capacity of different vegetation types were significant different (P<0.05). The maximum soil water holding capacity and capillary water holding capacity ranged from 44.31 to 46.23 and 34.07 to 37.98 g/cm³, and the primary arbor forest was the highest and the arbor forest was the lowest. (4) The water holding capacity of litter showed logarithmic relationship with time. The water absorption rate was the highest at 0.5 h, and decreased at 4.0 h. The maximum water holding capacity reached saturation at 12 h, and the water absorption rate was close to 0. (5) The maximum water holding rate and effective interception rate of the primary arbor forests litter were higher than those of the arbor forests. The maximum water holding rate and effective interception rate of each vegetation type of the engineering accumulation body were grassland>shrub forests>arbor forests. From the perspective of litter and soil water holding capacity, the combination made of grass and shrub can be used as a pioneer vegetation for the construction of stable community ecological structure at the initial stage of the accumulation. The research results can provide a theoretical basis for the soil and water conservation measures and vegetation restoration.

Abstract:The Yellow River Basin has an important strategic position and is an important ecological barrier in China. Quantitative assessment of the impact of climate change and human activities on vegetation change in the Yellow River Basin is of great significance to government management and decision-making. Taking the Yellow River Basin as the research area, the temporal and spatial dynamic changes of normalized difference vegetation index (NDVI) from 1982 to 2019 were analyzed, the contributions of climate change and human activities on NDVI were quantitatively calculated, and the influencing factors of NDVI were mapped. On this basis, the impact of ecological construction project on vegetation change was discussed, and its effectiveness was evaluated. The results showed that: (1) From 1982 to 2019, the NDVI of the Yellow River Basin showed a significant increasing trend, with a change trend of 0.002 4/a. The regions with significant degradation in NDVI were distributed in the west and south of the basin, and the regions with significant increase in NDVI were distributed in the middle and north of the basin. (2) Vegetation change in the Yellow River Basin was the result of the joint action of climate factors and human activities. The contribution of climate factors to NDVI change was 82.74%, and the contribution of human activities was 17.62%. Climate factors were the dominant factors of vegetation change in the Yellow River Basin, but the influence of human activities in vegetation change was gradually increasing. (3) The vegetation restoration of the three ecological construction projects followed the order of the Three-North Shelter Forest Program>Shelter Forest Belt Project in Middle Reach of the Huanghe River>Afforestation of Taihang Mountain, and the ecological construction project played a significant role in promoting vegetation restoration.

Abstract:In the reservoirs eliminating danger and reinforcement engineering in severe soil erosion area of the Loess Plateau in southern Ningxia of China, the construction technique of "raising earth dam from upstream deposited mud" is generally adopted. And the distribution rule of deposit layers is very important to evaluate the stability of the dam foundation. In order to investigate the profile stratification and spatial distribution characteristics of the upstream silted soil, the ground penetrating radar (GPR) was used to detect the silted soil in front of Dashahe reservoir in Xiji County, Guyuan City. In the selected detection area of the silted soil in front of the dam, 10 survey lines were laid. First, the number of superimpositions for the best image effect of radar detection was determined, and then detection was carried out at 0.5 m intervals (a total of 794 detection points) on all test lines. At the same time, a 1.5 m deep trench was excavated to observe the profile of the silting layer. And soil samples were taken from different depth profiles for laboratory experiments of basic physical-mechanical properties. The results showed that the optimal number of superpositions of radar detection was 512. Radar spectrum showed that there were six obvious sedimentary bedding layers in the range of 0 to 2.5 m. In the depth range of 4 m to 9 m, there was a clear and continuous outline of the river-bed profile, and the sedimentary thickness of the silt on each survey line ranged from 3.7 m to 8.2 m. Obvious sandy silt-clay silt bedding could be observed at the depth of about 50 cm in the trench, which was consistent with the image analysis of GPR at this position. These findings could provide a basis for the settlement calculation and engineering treatment measures of the silting layer in front of the earth-filled dam.

Abstract:In order to explore the application of biochemical fulvic acid (BFA) in soil structure improvement, the influence of BFA on soil physical properties and water movement characteristics under different concentrations was studied by adding BFA to soil. The results showed that: (1) As the proportion of BFA increased, the number of water-stable aggregates>0.25 mm in soil increased significantly. When the proportion was 20 g/kg, R_0.25, mean weight diameter (MWD) and geometric mean diameter (GMD) increased by 284.98%, 105.64%, and 35.06%, respectively, the fractal dimension decreased by 2.17%. (2) Under the influence of temperature and pH change, the absolute value of Zeta potential first increased and then decreased as the application ratio increased. When the application ratio was 20 g/kg, the absolute value of Zeta potential increased by 11.77% and 59.70%, respectively. (3) Applying BFA to soil could enhance soil infiltration capacity, increase cumulative infiltration and infiltration rate, and accelerate soil moisture front migration. Moreover, with the increase of application ratio, soil moisture infiltration capacity was significantly enhanced. Cumulative infiltration and was increased by 28.83%. The three infiltration models could simulate the soil water infiltration process well.

Abstract:In order to compare and analyze the similarities and differences between global hectare and national hectare in water resources ecological footprint accounting, based on the theory and method of water resources ecological footprint, two calculation models of water resources ecological footprint in Shanxi Province with "global hectare" and "national hectare" were constructed, and the water resources ecological footprint of Shanxi Province in 2007—2018 were calculated. The results showed that: (1) The change trends of the per capita water resources ecological footprint, per capita water resources ecological carrying capacity and per capita water resources ecological deficit of Shanxi Province during the past 12 year obtained by the two models were similar, and the overall trends of all above indexes were upward. However, the results obtained by the national hectare method were all greater than the results obtained by the global hectare method in the same year. (2) Two different algorithms both showed that the water resources ecological footprint per 10 000-yuan GDP in Shanxi Province from 2007 to 2018 was declining, indicating that water resource utilization rate was improving in the past 12 years. (3) Two different methods showed that the ecological pressure index of water resources in Shanxi Province was far greater than one in the past 12 years, indicating that development and utilization of water resources was in an unsafe state. The research thought that: (1) The main reasons for the differences between the two algorithms were the differences in the water resources equivalence factor, water resources yield factor and the average production capacity of regional water resources. Compared with the global hectare method, the national hectare method could better reflect the development and utilization situation of water resources at the spatial scale below the national level. (2) According to different research purposes, it was necessary to construct the corresponding calculation models to calculate and analyze the water resources ecological footprint, which was not only conducive to better reflect the development and utilization situation of regional water resources on different spatial scales, but also was conducive to the comparison of the water resources ecological footprint on the same spatial and regional scale.

Abstract:Surface water and groundwater are the main components of water resources. It is of great theoretical significance to study the mutual transformation process of surface water and groundwater in arid areas for the rational development, utilization, and evaluation of water resources. Based on surface water and groundwater in Ebinur Lake basin, the stable isotope composition characteristics, distribution law, and the recharge relations of different water types were discussed. Results showed that: (1) The δ²H and δ¹⁸O values of precipitation in the Ebinur Lake basin showed significant seasonal variation, presenting dilution in winter and enrichment in summer through the whole year.(2) In the Ebinur Lake basin, the stable isotopes values of lake were significantly higher than that of river, which reflects the strong water evaporation concentration of lake. In Bortala river and Jinghe river, the δ²H and δ¹⁸O from upstream to downstream tended to enrichment, but it showed different features among the areas of mountain, oasis and plains. The δ²H and δ¹⁸O of groundwater presented the minimum in mountainous part, the middle in plains, and the highest surrounding the Ebinur Lake. (3) In Bortala river, the exchange proportion of groundwater and river water in the upper reaches was large, which was 63.0%. The exchange ratios in the middle and lower reaches were relatively low, which were 5.0% to 33.0% and 2.5% to 26.0%, respectively. In Jinghe river, the deep groundwater was replenished by shallow groundwater and river water, the recharge ratios were 73.3% and 26.7%, respectively. In the vicinity of Ebinur Lake, the diving flow was cut off and exposed to spring water, which supplies the lake with the river water. The study revealed the exchange relationship between surface water and groundwater in Ebinur Lake basin, which can provide scientific support for water resource management and ecological environment construction of the Ebinur Lake basin.

Abstract:Weihe River basin, as the largest tributary of the Yellow River basin, is one of the key ecological protection built-up areas. The study on ecosystem services is conducive to the realization of the balance between high-quality development and ecological protection in the basin, to the maintenance the ecosystem service function of the basin, and to the promotion the restoration of the basin ecosystem. Based on the InVEST model, this paper analyzed the spatial-temporal dynamic changes of land use and ecosystem services of main and tributaries in the Weihe River basin from 2000 to 2018, and used correlation analysis to analyze the trade-offs and synergies among the balance of water conservation, soil conservation, and biodiversity. The results showed that the land use in the study area was mainly cultivated land, grassland, and forest land, accounting for more than 95% of the total area. Water conservation in the basin showed a trend of "increasing first and then decreasing", with an average grid unit yield of 542.9 mm. The water conservation in the Weihe River basin was higher than that in Jing River basin and Beiluo River basin, which were 6.88×10⁸, 5.04×10⁸, 3.36×10⁸ m³. The soil in the basin remained patchy and the overall soil erosion status of the basin was slight. Moreover, the soil erosion in the main stream of Weihe River basin was greater than that in Jing River basin and Beiluo River basin, which were 6.67×10⁸, 3.13×10⁸, 6.22×10⁸ t. The biodiversity showed that the areas with high habitat quality were concentrated in the forest ecological protection areas with good ecology and the habitat quality was poor in the areas with dense human activities. During the study period, there was a highly synergistic relationship between water conservation, soil conservation, and ecological quality in Weihe River basin, while other ecosystem services were not significant. It can be seen from the correlation that different land use types have different values of tradeoffs and collaborative contributions to ecosystem services.

Abstract:A 120-day indoor culture experiment was conducted by collecting soils with different carbon sources combined with nitrogen fertilizer in a field experiment set in Lijiabu Town, Dingxi City, Gansu Province since 2014. The Stanford batch elution culture method was used to study the effects of four fertilization methods, including no carbon and nitrogen addition (N0), only nitrogen application (N100), straw combined with nitrogen (SN100) and biochar combined with nitrogen (BN100), on soil nitrogen mineralization. The fertilization was applied to experimental fields in the dry farmland of the Loess Plateau in central Gansu. The results showed that compared with nitrogen application only, straw and biochar combined with nitrogen fertilizer significantly increased nitrogen mineralization in surface soil by 16.5% and 15.4% respectively. Soil nitrogen mineralization showed a rapid increase and then a rapid decrease, and the decreasing rate gradually leveled off. The nitrification rate and ammonification rate reached their maximum at 7 and 15 days, and stabilized at 45 and 30 days, respectively. The nitrogen mineralization rate of the upper soil was significantly increased by straw and biochar combined with nitrogen fertilizer. The nitrification rate and ammonification rate were in a relatively balanced state. The redundancy analysis between the changes of soil organic nitrogen fractions before and after culture and the amount of soil nitrogen mineralization showed that the largest contribution to soil mineralized nitrogen was amino nitrogen, followed by acid unknown nitrogen. Mineral nitrogen was negatively correlated with unacidolyzed nitrogen and positively correlated with all fractions of acidolyzed organic nitrogen. In addition, compared with no nitrogen application, adding straw and biochar under nitrogen application increased the variation of organic nitrogen fractions in the surface soil. These results indicated that the addition of straw and biochar could increase the content of easily mineralized nitrogen by changing the proportion of organic nitrogen fractions to total nitrogen, thus subsequently promote the mineralization of organic nitrogen fractions and improve the potential of soil nitrogen supply.

Abstract:An indoor soil column simulation experiment was conducted to examine the effect of adding straw and biochar on the nitrogen leaching loss of Hainan tropical paddy soil under different moisture conditions. Four treatments were set up: control (CK), addition of biochar (B), biochar + rice straw (BCS), and rice straw (CS) at two moisture condition: 75% field water holding capacity (WHC, simulated dry farming soil) and flooding conditions (simulated paddy field). The results showed that both biochar and straw addition could increase soil pH, soil organic matter, total nitrogen, available potassium and available phosphorus contents. Under 75% WHC conditions, compared with CK, BCS and CS treatments significantly increased soil NH₄⁺—N leaching by 16.30% and 48.56% respectively, and no significant difference was found in B treatment. The treatment of CS increased soil NO₃^-—N leaching compared with CK, and BCS treatment reduced soil NO₃^-—N leaching, while there was no significant difference in B treatment. BCS and CS treatments significantly increased soil nitrate-ammonium nitrogen (S) leaching compared with CK, while there was on significant effect in B treatment. Under flooding conditions, compared with CK, the leaching loss of NH₄⁺—N and S in the soil was reduced by 16.30% and 12.81%, respectively, but had no significant effect on the NO₃^-—N leaching loss in B treatment. CS treatment significantly decreased the leaching loss of soil NH₄⁺—N, NO₃^-—N and S by 19.26%, 33.96% and 22.37%, respectively. BCS treatment reduced the leaching loss of soil NH₄⁺—N and S by 14.52% and 14.19%, respectively, but had no influence of NO₃^-—N leaching. In summary, returning straw to the field under dry farming conditions would increase soil leaching loss of NH₄⁺—N and NO₃^-—N, but biochar had no effect on nitrate ammonium leaching under the rice-vegetable rotation planting model in tropical areas of Hainan. In the paddy field, biochar could reduce the leaching loss of NH₄⁺—N, but had no effect on NO₃^-—N, while the straw could decrease the leaching loss of NH₄⁺—N and NO₃^-—N.

Abstract:The purpose of this research was to explore an irrigation pattern taking into account the yield and quality of forage in the alpine desert area, and to promote the application of micro-sprinkler irrigation and regulated deficit irrigation in artificial grassland production. A field experiment was conducted to compare and analyze the effect of 2 cropping patterns and 7 irrigation patterns on forage yield, quality (stem-leaf ratio, crude protein content and yield, acid detergent fiber content, and neutral detergent fiber content) and water use efficiency. The 2 cropping patterns were mono-sowing oats and mixed sowing of oats and peas, and the 7 irrigation patterns were mild water deficit at jointing stage (65%~75%), moderate water deficit at jointing stage (55%~65%), severe water deficit at jointing stage (45%~55%), mild water deficit at flowering stage (65%~75%), moderate water deficit at flowering stage (55%~65%), severe water deficit at flowering stage (45%~55%), and full irrigation during the whole growth stages (75%~85%). In addition, the methods of analytic hierarchy process and entropy weight were used to empower the multiple indicators of forage, and an evaluation system was constructed based on the TOPSIS model to obtain the optimal irrigation pattern. The results showed that: (1) With the increasing of water deficit, the forage yield showed a decreasing trend. Under the same irrigation condition, the forage yields of mixed sowing of oats and peas (7 811.1~14 490.1 kg/hm²) were higher than those of mono-sowing oats (7 022.3~12 242.7 kg/hm²). (2) Under the same cropping pattern, the contents of NDF and ADF decreased first and then increased with the increasing of irrigation deficit. However, the content and yield of crude protein, WUE, and IWUE increased first and then decreased with the increasing of irrigation deficit. (3) The comprehensive evaluation showed that mixed sowing of oats and peas with full irrigation at jointing stage and moderate water deficit at flowering stage could achieve better water-saving, yield-increasing, and quality-improving effects (forage yield, crude protein content, WUE, and IWUE were 14 330.2 kg/hm², 10.66%, 31.49 kg/(hm²·mm), and 80.96 kg/(hm²·mm), respectively). It was a suitable production management pattern of artificial grassland using micro-sprinkler irrigation in alpine desert grassland.

Abstract:In order to explore the variation of soil salinity and groundwater during crop growth period in semi closed irrigation area of Hetao irrigation district, the typical saline soil area in Wuyuan County, Bayannaoer, was selected as the study area. Based on fixed monitor of the regional soil-groundwater information, 149 sampling points and 30 groundwater observation wells were selected to collect data. Combined with classical statistics, spatial interpolation, and correlation regression analysis methods, the relationship between soil salinity and groundwater spatial dynamics, soil salinity, and groundwater depth was studied. The results showed that from April to October, the soil salt content of each soil layer decreased by 5.53% on average. The 1 m deep soil in the study area was desalinated, and the surface salt migrated to the deep soil. The main influencing factors of groundwater depth were irrigation water volume from the Yellow River, evaporation, and topography distribution in the study area. During the spring irrigation period (April to June), the average groundwater salinity decreased from 2.81 to 2.38 g/L, and the average groundwater salinity increased to 2.66 g/L from June to October. The groundwater mineralization was low during the spring irrigation period, increased after autumn harvest, and was high in the early spring irrigation from April to May. Due to the influence of irrigation and crop growth, the average soil salinity of 0—20 cm after autumn harvest decreased by 32.08%. During the growth period of crops, soil salinity migrated to deep soil (40—100 cm), and soil salinity was inversely proportional to depth, As the depth increases, the change in soil salt distribution gradually weakened. The area of 0—20 cm and 20—40 cm soil that had salinity greater than 4.0 g/kg in the same period was 85.63% and 9.71% in April, 42.37% and 15.86% in October. With the increase of soil depth from 40 cm to 100 cm, the decreasing trend of soil salinity tended to be gentle. With the increase of shallow groundwater depth, soil salinity gradually decreased, and effective measures should be taken to reduce the groundwater depth by 0.2 m, which is better to control within from 1.8 to 2.2 m.

Abstract:Nitratia tangutorum nebkhas is a desert landscape which was shaped by aeolian sand. Study on response of morphological characteristics and distribution of Nitraria tangutorum nebkhas to sand supply can provide a basis for further study of its formation and evolution. This study was conducted at an area where had a massive Nitratia tangutorum nebkhas at the southern margin of the Badain Jaran Desert. The morphological characteristics and distribution pattern of the nebkhas were investigated and analyzed. The results showed that the nebkhas in early stage and developmental stage accounted for 24.0% and 42.2%, respectively, of the total nebkhas. The mean distance between adjacent nebkhas was only 9.8 m. Along prevailing wind direction, the distances between adjacent nebkhas changed rapidly from big to small, keeping it for a distance and then enlarged slowly. The densities changed conversely. Under the influence of high sand supply and resulted strong soil erosion and deposition transformation, the stabilization process of Nitraria tangutorum Nebkhas was slowed down, the parameters of all the morphological characteristics were small. Correlation analysis showed that there were significant correlations between nebkhas height, length, width, windward slope length, leeward slope length, and basal area (P < 0.01). The results indicate that under the abundant supply of sand, the Nitratia tangutorum nebkhas in this area were in its early and middle stage of the whole growth phase, and showed big density with small shape landscape traits.

Abstract:In order to clarify the spatial and temporal distribution of soil nitrogen and phosphorus and their influencing factors in the riparian zones of Fenhe River, the purpose of this study was to discuss the stoichiometric characteristics, spatiotemporal distribution characteristics of soil nitrogen and phosphorus and their correlation with soil and hydrological characteristics in natural riparian zone and strong artificial-disturbance riparian zone. The results showed that: (1)There serves of total nitrogen (TN) and total phosphorus (TP) in the strong artificial-disturbed riparian zone were bigger than those in the natural riparian zone, and the coefficients of variation in natural riparian zone were smaller than those of the strong artificial-disturbed riparian zone. The ecological stoichiometry of nitrogen and phosphorus in soil of natural riparian zone were weakly stable in each water period. (2) As for the riparian zones in Fenhe River during each water period, the contents of TN and TP in the soil of riparian zones showed a trend of first decreasing and then increasing with the period to dry season-normal season-wet season. In the lateral direction along the riparian zone, the contents of nitrogen and phosphorus in the soil of near-bank part were significantly higher than those in the far-bank part. While the contents of TN and TP in the depth direction of the soil decreased with the increase of depth. (3) River water quality, soil bulk density and soil porosity were the correlation factors affecting soil TN content in riparian zones of Fenhe River, while soil bulk density, soil porosity and ratio of nitrogen and phosphorus were the correlation factors affecting soil TP content in riparian zones. The results showed that the distribution of soil nitrogen in riparian zones of Fenhe River had a certain response relationship with river hydrological characteristics, while the distribution of soil phosphorus had no obvious response relationship with the river hydrological characteristics.

Abstract:A field experiment was conducted to study the effects of different fertilizer treatments on soil nutrients, yield, quality and nutrient utilization of muskmelon in the Hetao Irrigation District of Bayannur city, Inner Mongolia. The traditional planting mode of fertilization and irrigation was that after all fertilizers was added and mulched with plastic film, flood irrigation was applied to leach salt, then the seeds were sowed. Six treatments were set up, including CK treatment without any fertilizer (CK), conventional fertilization treatment (CF, N 445.5, P₂O₅ 399, and K₂O 54 kg/hm²), reduced and optimized fertilization treatment (RF, N 240, P₂O₅ 150, and K₂O 120 kg/hm²), reduced controlled-release fertilization treatment (RSF, controlled-release urea, N 240, P₂O₅ 150, and K₂O 120 kg/hm²), reduced and optimized fertilization combined with organic manure treatment (RF+OM, combined with organic manure 15 t/hm²), reduced controlled-release fertilization combined with organic manure treatment (RSF+OM). The results showed that the soil nitrogen content of RSF treatment was higher during the growth period of muskmelon. Treatments added with manure (RF+OM, RSF+OM) maintained the level of soil organic matter, therefore increased soil fertility, as compared with the treatments only added the chemical fertilizers. Compared with no fertilization (CK), the yield of muskmelon in all fertilization treatments increased significantly (P<0.05). The yield of RSF+OM treatment was significantly higher than that of CF treatment; and there were no significant differences between the yield and quality of RF, RSF and RF+OM treatments compared with the CF. Compared with CF treatment, RF and RSF treatments increased the nitrogen use efficiency by 15.1% and 21.5%, respectively. Compared with CF, RF and RSF treatments increased the phosphate use efficiency by 20.4% and 18.8%, respectively. Reducing the application of chemical fertilizer and applying controlled release fertilizer had important ecological and environmental significance for reducing nitrogen loss from muskmelon field in the Hetao Irrigation District into the Wuliangsuhai Lake.

Abstract:Taking the seedlings of the dwarf rootstock M9T337 as the test material, 4 nitrogen (N) levels (N 0, 150, 300, 450 mg/kg, represented by N0, N1, N2, N3, respectively) and 2 phosphorus (P) levels (P₂O₅ 100, 200 mg/kg, represented by P1 and P2, respectively) was set up to study the effects of combined application of N and P fertilizer on the growth of apple rootstock seedlings, the transformation of soil inorganic P forms and its absorption and utilization, in order to provide a reference for the efficient use of P fertilizer in orchards. The results showed that different N and P treatments significantly affected the biomass and root morphology of M9T337 seedlings, and N2P2 treatment performed best, followed by N1P2 treatment. P accumulation and P fertilizer utilization efficiency in seedings reached the maximum under N2P2 and N2P1 treatments, respectively. Under the same P level, appropriate N addition could promote the absorption of P by seedlings and effectively improve the P fertilizer utilization efficiency of plants. High N treatment (N3P1, N3P2) significantly inhibited the uptake of P in soil by seedlings, which was not conducive to the growth of rootstock seedlings. The soil available phosphorus (Olsen—P) content was mainly affected by the amount of P applied, and reached the maximum value of 27.86 mg/kg under N2P2 treatment. The maximum alkaline phosphatase activity reached at 2.12 mg/(g·d) under N2P1 treatment. Compared with P applied alone, combined application of N and P increased the proportion of Ca₈—P and Al—P in the soil P pool that could be absorbed and utilized by plants, and reduced the proportion of Ca₁₀—P that was difficult for plants to absorb and utilize, and the proportion of Ca₂—P was also reduced. With the increase of N application rates, Ca₈—P and Al—P showed a trend of firstly increasing and then decreasing, and both reached the maximum under N2P2 treatment. Ca₁₀—P showed a gradually decreasing trend with the increase of N application rates. There was a stable trend of Fe—P and O—P content under different N application rates. Reasonable N and P combination could improve the availability of P in soil by changing the composition of soil inorganic P pool, and promote the growth of rootstock seedlings and the absorption of P in soil.

Abstract:High fixation and low shifting ability of phosphorus in calcareous soil often caused low use efficiency of phosphorus fertilizer in North China. This study examined the effect of different kinds of phosphorus fertilizer on maize growth and soil inorganic fractions in order to improve the utilization efficiency of P fertilizer. Pot experiment was carried out with 6 treatments of monammonium phosphate (MAP), superphosphate (SSP), ammonium polyphosphate (APP), nitrophosphate (NiP) and ammonia sulfate+superphosphate (SA+P). The biological characteristics and phosphorus uptake of maize were measured after 60 days, soil available phosphorus contents and inorganic fractions were measured as well. The results showed that biological performance, phosphorus accumulation and phosphorus use efficiency of maize performed as the trend of APP>MAP, NiP>SSP, SA+P>CK; APP, MAP and NiP significantly increased maize height, leaf area, ground and root biomass compared with the control (CK) by 23.3~35.1 cm, 57.1~89.0 cm², 265%~420% and 171%~218%, respectively. Maize in APP treatment accumulated P 49.02 mg/pot in total with 36.75% of phosphorus recovery efficiency, which significantly different from 21.43% of NiP and 19.42% of MAP. Ca₂—P、Ca₈—P and Fe—P contents significantly increased in APP and MAP treatments compared with the control, which had significant relationships with plant uptake (p<0.001). APP is a kind of suitable phosphorus fertilizer for maize in calcareous soils, which is important for securing food safety and achieving high phosphorus use efficiency under background of reducing phosphorus fertilizer input in farmland.

Abstract:The effects of combined application of organic fertilizer and chemical fertilizer on yield, quality, and water use efficiency of dryland wheat were studied, which provided theoretical basis for substituting chemical fertilizer with organic fertilizer and reducing annual yield fluctuation in dryland wheat field in loess hilly region. In 2017—2019, the effects of constant chemical fertilizer (B), constant chemical fertilizer substituted by pig manure (A₁B₁, substituted by 20%; A₁B₂, substituted by 30%; A₁B₃, substituted by 40%) and constant chemical fertilizer substituted by sheep manure (A₂B₁, substituted by 20%; A₂B₂, substituted by 30%; A₂B₃, substituted by 40%) on the yield and composition, grain nutritional quality, flour processing quality, and water use efficiency of dryland wheat were studied. The results showed that, compared with the application of chemical fertilizer only, the combined application of organic fertilizer and chemical fertilizer can improve the yield, grain bulk density, hardness index, protein content, and flour sedimentation value of dryland wheat, and chemical fertilizer substituted by proper amount of organic fertilizer can increase water use efficiency. The effects of pig manure and sheep manure on yield and water use efficiency were different under different years. Compared with sheep manure combined with chemical fertilizer, the spike number and kernels per spike of dryland wheat were increased and the yield and water use efficiency were improved by pig manure combined with chemical fertilizer in wet year, which showed periodic drought in growth period and freezing injury in spring. Compared with pig manure combined with chemical fertilizer, the spike number, yield, and water use efficiency were increased by sheep manure combined with chemical fertilizer in dry years that had precipitation in key growth period and high water storage in fallow period. The proportion of organic fertilizer substituting for constant chemical fertilizer varies with the type of organic fertilizer. Pig manure substitute for 20% chemical fertilizer was the best, increased yield by 39.76% and 2.46% compared with the application of chemical fertilizer only respectively, and increased water use efficiency by 4.91 kg/(hm²·mm) in 2018; sheep manure substitute for 40% chemical fertilizer was the best, increased yield by 18.88% and 2.28% compared with the application of chemical fertilizer only, and increased water use efficiency by 2.57 kg/(hm²·mm) and 12.68 kg/(hm²·mm) respectively. In the two extreme years’ experiment, the reduction of chemical fertilizer combined with pig manure or sheep manure could improve wheat yield and water use efficiency, improve wheat quality, and increase soil organic matter content in topsoil. Considering from the dour qualities and the point of fertilizer saving, 20% chemical fertilizer that substituted by pig manure or 40% substituted by sheep manure is recommended for the wheat production in Southern Shanxi Province.

Abstract:In order to explore the effect of different irrigation amount on soil water and salt transport and growth characteristics of Spring Maize in Hetao Irrigation District (HID) under ridge with film mulching-furrow irrigation system, field experiments were carried out in Shuguang experimental station of HID from April to October, 2019. Five typical irrigation amounts (T1: 200 mm, T2: 275 mm, T3: 350 mm, T4: 425 mm, T5: 500 mm) were arranged to study the characteristics of soil water and salt transport under ridge with film mulching-furrow irrigation and its effects on yield and water use efficiency (WUE) of spring maize. The results showed that the soil water storage of 0—120 cm soil layer in T4 and T5 treatments was close, and the water consumption of maize in T5 treatment was significantly higher than that in other treatments. The average salt storage in T1~T5 treatments were 48.37, 26.84, 19.34, 21.38, and 22.79 t/hm², respectively. The salt storage quantity of T1, T2, and T5 treatments increased by 27.33, 1.54, and 5.88 t/hm² respectively, and T3 and T4 decreased by 10.04 and 3.42 t/hm² so that the salt accumulation showed a "V-shaped" change. With the increase of irrigation amount, WUE first increased and then decreased, and the yield increased first and then stabilized. Under the irrigation amount of 200 mm and 275 mm, the soil was seriously short of water, and the salt storage was high. The soil water and salt environment of 350 mm treatment was suitable, where the yield and water use efficiency were high, and the deep layer leakage of 425 and 500 mm was large, and the salt storage quantity tended to increase gradually. Therefore, on the premise of reducing the amount of water diversion from the Yellow River, the irrigation amount of 350 mm under ridge with film mulching-furrow irrigation can achieve the goal of water saving, salt control and yield increase in HID.

Abstract:The objective of this study was to explore the effects of nitrogen application on spring maize nitrogen uptake and soil biological and chemical properties under drought stresses at seedling stage in Northeast China. The results might provide a basis for regional maize nutrient management and adversity regulation. In this study, a pot experiment was conducted with two factors of water and nitrogen. The soil water level included 30%, 50% and 70% of field capacity (W0, W1 and W2), respectively, and nitrogen application included 0 and 0.24 g/kg soil (N0 and N1), respectively. The shoot dry matter and nitrogen uptake of maize at the seedling stage, soil chemical properties, microbial biomass carbon, nitrogen (MBC, MBN) and soil enzymes activities in the rhizosphere and bulk soil were measured in different water and nitrogen conditions. The results showed that drought stresses significantly reduced maize shoot dry matter and nitrogen uptake at seedling stage, and W0 condition decreased the most (51.1%, 43.8% respectively). Nitrogen application promoted plant growth under different water conditions and had significant interaction with water. The increase in shoot dry matter and nitrogen uptake was the highest (53.7%, 83.2% respectively) under W2 condition. Drought stresses increased water use efficiency (WUE), but decreased nitrogen use efficiency (NUE). Nitrogen application significantly increased WUE under W2 condition, but had no significant effect under drought conditions. The effects of water, nitrogen and their interaction on soil properties were complex. In general, drought stresses at seedling stage temporarily increased the pH value in rhizosphere and bulk soil, and significantly increased the contents of ammonium and nitrate nitrogen (NH₄⁺ and NO₃^-) in[PJ] rhizosphere soil. The responses of MBC and MBN to drought stresses were opposite between rhizosphere and bulk soil. Rhizosphere soil increased with the increase of drought degree, while bulk soil decreased. In terms of soil enzyme activity, drought stresses significantly affected nitrate reductase (NR) and nitrite reductase (NiR) activities in rhizosphere soil. Nitrogen application increased the pH, NH₄⁺ and NO₃^- contents in rhizosphere and bulk soils under all water conditions, and the increase rate of rhizosphere soil was higher than that of bulk soil. Nitrogen application significantly increased MBC, MBN, urease (UR) and NR activities in rhizosphere and bulk soil under various water conditions, but significantly reduced NiR activity in rhizosphere and bulk soils. The interaction of water and nitrogen significantly affected NiR activity in rhizosphere soil, UR, NR and FDA activities in bulk soil. There was a significant correlation between the biological and chemical properties in rhizosphere and bulk soil, and the indexes of rhizosphere soil except NiR activity were positively correlated with plant nitrogen uptake and NUE. Drought at seedling stage significantly inhibited maize plant growth and nitrogen uptake, and significantly affected soil biological and chemical properties. The effects of nitrogen application on plant and soil properties were different under different water conditions, and there was a significant correlation between plant performance and soil biological and chemical properties.

Abstract:In order to reveal the effect of different forests on soil aggregate stability in Xiaolongshan forest region of Gansu province, three typical forest stands (Pinus tabuliformis, Larix kaempferi, Quercus aliena var. acuteserrata) were selected as objects of study. The fast wetting (FW) method in Le Bissonnais was used to determine the mean weight diameter (MWD) of soil aggregates in different soil depths (0—10, 10—20, 20—40 cm), and the effects of soil physicochemical properties (soil mechanical composition, SOC, CEC, pH) and root characteristics (proportions of fine root and very fine root, RLD, RMD, SRL) on soil aggregate stability were further studied. The results showed that the stability of soil aggregates under different forest stands were ranked as Quercus aliena var. acuteserrata>Pinus tabuliformis>Larix kaempfer. Stability of soil aggregates of different soil depths were ranked as 0—10 cm>10—20 cm>20—40 cm. According to simple linear regression models, the soil characteristic factors that contributed the most to the MWD of soil aggregates were CEC (R²=0.55) and SOC (R²=0.54), the root characteristic factors that contributed the most to the MWD of soil aggregates were RMD (R²=0.60) and RLD (R²=0.45), and there was a significant positive correlation between soil aggregate stability and the four factors above. Overall, soil aggregate stability differed in different forest stands, soil aggregate stability decreased with the increasing soil depth, and the factor that influenced the stability of soil aggregates the most was RMD.

Abstract:Gully erosion is a kind of intense soil erosion process, which leads to the surface morphology of gully development area in an unstable state of significant change. Natural restoration of vegetation through prohibition is one of the main modes of gully management in Yuanmou Dry-hot valley. However, under the comprehensive effect of continuous restoration of gully vegetation and significant development of gully, the changing trend of soil carbon and nitrogen content in gully remains to be clearly defined. In this study, a typical gully in Yuanmou Dry-hot valley was selected, and 81 samples of 1 m×1 m were randomly arranged. The vegetation index, elevation changes caused by the erosion/sedimentation process, and soil physical and chemical properties of the 81 samples were measured at the beginning of the dry season in 2012 and 2017, the results showed that: (1) The vegetation conditions in the gully in 2017 were significantly better than that in 2012, and the vegetation changes within the range of runoff erosion on the surface of the gully bed were the most obvious, and the vegetation cover, number, and height increased by 313.61%, 94.29%, and 33.33%, respectively. (2) During the five years, the gully development area was dominated by sedimentation, and the proportions of erosion and sedimentation were 22.22% and 77.78%, respectively. With the increase of vegetation cover, the sand content of the soil showed a decreasing trend, and the silt content showed an increasing trend. (3) Although the vegetation recovered significantly during the period of prohibition, the soil carbon and nitrogen did not improve significantly. Soil carbon and nitrogen were not only significantly positively correlated with vegetation cover and soil particle-size, but also significantly negatively correlated with elevation changes of quadrate points. The severity of topographical changes in the gully was significantly higher than that of surface erosion, and it had a significant impact on the carbon and nitrogen of the surface soil of the gully. This study will help to identify the comprehensive effects of vegetation restoration and gully development on soil carbon and nitrogen, and provide support for the restoration of the degraded gully ecosystem in Dry-hot valley.

Abstract:In this study, the characteristics of nitrogen transformation in tea garden soil of Shandong Province were analyzed by indoor aerobic culture. Soil N transformation and enzymes activities in constant wet and dry/wet cycle conditions were measured. The results showed that: (1) The net mineralization quantity and net nitrification quantity, the activities of urease and nitrite reductase were the highest in the 60%WHC treatment at the end of incubation. The net mineralization and net nitrification rates were seriously inhibited in 20%WHC treatment. (2) In dry/wet cycle treatment, net mineralization quantity, net nitrification quantity and enzymes activities increased and the change of "pulse" pattern appeared. (3) N₂O emission was greater than NH₃ volatilization in both models. N₂O emission was directly proportional to soil water content, while NH₃ volatilization was inversely proportional. Dry wet alternation enhanced N₂O and NH₃ emissions. (4) The structural equation model revealed that soil water content affected soil N transformation (p<0.001); urease significantly improved soil N transformation in constant wet treatment (p<0.001), while nitrate reductase inhibited N transformation (p<0.001) in constant wet and dry/wet cycle models. These results might help to better regulate soil management and the use of N fertilizer in the tea garden ecosystem under different water supply conditions.

Abstract:In order to explore the cultivation technology mode of high yield and water use efficiency of maize in semi humid area, the method of straw returning combined with soil tillage was adopted, and four treatments were set up, including straw rotary ridge tillage (CK), straw deep ploughing returning (SP), straw mulching returning and no tillage (SC) and straw mulching returning and subsoiling (SS). The effects of different treatments on soil moisture, soil temperature, maize yield and water use efficiency were studied. The results showed that: (1) The change of soil water storage showed a single peak curve and double peaks curve in 2018 and 2019, respectively. The soil water storage of all treatments in 2018 and SS treatment in 2019 increased significantly with the increasing of soil depth. Compared with CK treatment, the soil water storage in SC treatment and SS treatment increased by 7.58% to 18.40% and 9.24% to 21.94% in 2018, respectively. (2) The soil temperature of 0—20 cm plough layer increased first and then decreased with the growth period of maize, and decreased gradually with the increasing of soil depth. Straw returning could regulate soil temperature. Compared with CK, the SP treatment increased ground temperature by 0.46 ℃ and 0.21 ℃ in May and June, SC treatment decreased the ground temperature by 1.72 ℃ to 2.79 ℃ from May to July, and increased the ground temperature by 0.22 ℃ in September. (3) In 2018 and 2019, compared with CK, the maize yield of SS, SP and SC treatments increased by 13.88% and 14.82%, 7.59% and 9.12%, 7.42% and 8.50%, respectively. (4) In 2018 and 2019, the water use efficiency of SS, SP and SC treatments increased by 13.79% and 9.75%, 6.11% and 5.93%, 5.67% and 3.83%, respectively. (5) Soil water storage each growth period (time) and 0—60 cm soil layer (space) had significant effects on maize yield. Soil water storage at 0—60 cm and each period except flowering stage in July and below 15 cm had significant positive correlation with water use efficiency. Soil temperature had no significant effect on maize yield and water use efficiency. Straw mulching and subsoiling technology increased soil water storage, improved soil temperature, increased maize yield and water use efficiency, and provided efficient cultivation technology pattern for rain fed agricultural area.

Abstract:In order to investigate the effect of grass return under different conditions on soil microorganism, enzyme activities and available nutrients in peach orchard, taking the cleaning tillage as the control, grass return naturally, grass return by mowing, grass return by mowing combined with organic matter-decomposing agent were set up in this study with a 3-year experiment. The effect of grass return under different conditions on soil microbial biomass, soil enzyme activities, and different forms of nitrogen and potassium content in soils were studied by collecting rhizosphere and non-rhizosphere region soils in the peach orchard. The results showed that grass return under different conditions could all increase the rhizosphere region soil microorganism quantity. Compared with the other treatments, grass return by mowing combined with organic matter-decomposing agent improved the quantity of rhizosphere and non-rhizosphere region soil bacteria and fungi significantly, which increased by 21.2%~48.2% and 11.7%~17.0% respectively. Grass return by mowing combined with organic matter-decomposing agent accelerated the decomposition and microbial reproduction of straw. Compared with the cleaning tillage, grass return by mowing combined with organic matter-decomposing agent increased soil urease, catalase and sucrose activities by 10.2%~45.4%, 26.8%~56.9% and 20.5%~30.7% respectively. Grass return had a positive effect on the accumulation of soil nutrients in peach orchard, and the result was especially obvious on the grass return by mowing combined with organic matter-decomposing agent treatment, which could not only increase the contents of soil inorganic nitrogen and organic nitrogen, but also reduce the nitrogen loss. Meanwhile, it significantly increased the contents of soil available potassium and water-soluble potassium, which were 12.6%~15.6% and 11.4%~39.1% higher than those of other treatments, respectively. In conclusion, grass return by mowing combined with organic matter-decomposing agent was the better way to improve soil microbial biomass, soil enzymes activities and nitrogen and potassium nutrients supply, which could provide a scientific basis for the better management of orchard grass.

Abstract:Soil enzymes are closely linked with nutrients and chemical properties of soil. Soil enzymes can activate nutrient elements in soil to improve soil quality. Changes in net primary productivity in response to climate change are likely to affect litter inputs to forest soil. However, the effects of altered litter input on soil enzymes activities and their stoichiometry remain poorly understood in Castanopsis carlesii forest. In this study, soil hydrolases β—glucosidase enzyme (βG), cellulose (CBH), β—N—acetylglucosaminidase (NAG), leucine aminopeptidase (LAP), and acid phosphatase (AP) activities and their stoichiometric characteristics under different litter input treatments with root exclusion, viz. no litter (NRNL), double litter (NRDL), control (CK) were measured in a subtropical Castanopsis carlesii forest in Sanming, Fujian, China. The results showed that compared with CK, NRDL significantly improved CBH and LAP activities, and increased the contents of soil total carbon (TC), total nitrogen (TN), mineral nitrogen, dissolved organic carbon (DOC), and microbial biomass nitrogen (MBN), while the content of MBC was only reduced under NRNL. It was also found that the soil enzyme stoichiometric ratio was not affected by litter input treatments. Moreover,the values of ln (βG+CBH)∶ln (NAG+LAP) were 1.25, 1.36, 1.30; the values of ln (βG+CBH) ∶ln (AP) were 0.78, 0.78, 0.83; the values of ln (βG+CBH) ∶ln (NAG+LAP) were 1.25, 1.36, 1.30; ln (NAG+LAP)∶ln (AP) were 0.62, 0.58, 0.64. The correlation analysis showed that TC, TN, mineral nitrogen, DOC, DON, MBC and MBN were significantly positively correlated with βG,CBH,AP and LAP activities. Redundancy analysis indicated that the changes in hydrolases activities and their stoichiometry were mainly driven by soil DOC concentration. Thus, NRDL could improve the hydrolase activity by increasing the concentration of soil DOC. This study could provide a basic theory for soil nutrient management in subtropical forests.

Abstract:In order to clarify the synergistic effect of Paenibacillus mucilaginosus and Rhizobium meliloti on the reclamation of dumping in mining area, the soil of dumping in the mining area was used as the substrate for a pot experiment, and the single inoculation treatments of two bacteria, dual inoculation treatments and control were set up. The dosages of P. mucilaginosus and R. meliloti in treatments were 1.50% and 0.25%, respectively. The alfalfa yield, leaf physiological indexes, soil available nutrients contents, soil microbial indexes were determined. The results showed that inoculant of P. mucilaginosus and/or R. meliloti could improve the yield of alfalfa, and dual inoculation treatment was the highest and better than the control by 110.27% and 124.32% for biomass and nodules index, respectively. As for physiological indexes, the effect of dual inoculation treatment was lower than that of single inoculation treatments, and no synergistic effect was found. In terms of soil nutrients and microbial properties, single inoculation of P. mucilaginosus only significantly increased the soil available potassium content, and single inoculation of R. meliloti had a significant effect on most indicators. Dual inoculation treatment had the best effect. It increased significantly the contents of available nitrogen and potassium of soil by 94.14% and 84.55% respectively compared with the control. The soil microbial indexes, including MBC content, respiration intensity, invertase, urease, phosphatase, and catalase activities, were significantly increased by 204.02%, 65.86%, 212.32%, 91.87%, 30.57% and 51.87%, respectively. The dual inoculation treatment showed a significant synergistic effect on the alfalfa yield, soil nutrient and microbial indexes. Therefore, the dual inoculant of P. mucilaginosus at the dosage of 1.50% and R. meliloti at the dosage of 0.25% could effectively improve the soil reclamation effect of the dumping with a synergistic effect and could be used as an efficient method for the reclamation of the dumping in the mining area.

Abstract:It is an effective way to alleviate the scarcity of fresh water resources to use unconventional water resources. In areas rich in brackish water, the freshwater resources are generally inadequate, but there are abundant reclaimed water resources. In order to explore the reasonable utilization of brackish water and reclaimed water in areas where freshwater was scarce, by using Shanghai green pot experiment, this research studied the soil salt-water dynamics, crop biomass including aboveground biomass and underground biomass, and crop physiological characteristics such as chlorophyll content of leaves, soluble protein content, malondialdehyde (MDA) content, activities of catalase(CAT), superoxide dismutase (SOD), and peroxidase (POD) under mixed irrigation of brackish water and reclaimed water at different ratios. There were four treatments, including reclaimed water irrigation (T1), mixed irrigation of brackish water and reclaimed water at 1∶2 (T2), mixed irrigation of brackish water and reclaimed water at 1∶1 (T3) and brackish water irrigation (T4), taking the fresh water irrigation (CK) as control. The saline degree of brackish water was 3 g/L. The results indicated that: (1) Both soil water content and soil salt content were improved under different mixed irrigation compared with CK, among which, the difference of soil water content under T4 and CK reached a significant level (P<0.05), and no difference between T1, T2, T3 and CK. While, soil salt contents in all mixed irrigation treatments had significant differences with CK. Compared with T1, soil water content and soil salt content (except T2 and T3) gradually increased significantly with the increase of brackish water proportion in the mixed solution. (2) Mixed irrigation with brackish water and reclaimed water affected aboveground fresh weight of crop while mixed irrigation had no obvious effects on aboveground dry weight and underground biomass. Compared with T1, aboveground fresh weights under T2, T3, and T4 decreased by 24.78% to 26.36% significantly, aboveground dry weights reduced by 19.14% to 24.54% insignificantly, and the fresh and dry weight of underground changed slightly. (3) Mixed irrigation with brackish water and reclaimed water promoted the activity of SOD significantly, but had no obvious effects on crop physiological characteristics including chlorophyll content, soluble protein content, MDA content, POD activity and CAT activity. Compared with T1, chlorophyll-a content decreased by 4.98%, 3.82% and 9.26%, chlorophyll-b content reduced by 10.88%, 8,20% and 13.46%, total chlorophyll content decreased by 9.76%, 6.12% and 10.15%, CAT activity improved by 8.51%, 8.51% and -19.15%, POD activity increased by 1.92%, 17.24% and -2.87%, and SOD activity improved by 104.07%, 62.20% and 41.67% respectively under T2, T3 and T4. The soluble protein content decreased first and then increased while MDA content increased first and then decreased with the increase of brackish water proportion in mixed solution. Therefore, considering soil water-salt dynamic, crop physiological characteristics and the limits of reclaimed water, it could be used as an alternative source of fresh water to mix with brackish water (3 g/L), the suitable mixed proportion would be 1∶1 based on the integrated biological response version 2 (IBR_v2). The research results could provide the reference for the utilization of brackish water in the areas where fresh water is short.

Abstract:In-situ passivation is one of the important methods for the remediation of cadmium-contaminated paddy soil, and the selection of passivation agent is critical for efficient remediation. This paper studied the inactivation effect of cadmium in paddy soil by applying limestone and main conditioning agents with three field trials and comparative investigations in demonstration plots, and the effective technical measures was discussed. The results showed that sufficient amount of limestone (≥3.75 t/hm², experiment I), calcium-magnesium phosphate fertilizer (3.75 t/hm², experiment III) and biomass charcoal (9.00 t/hm², test II; 7.50 t/hm², test III)), lime (3.00 t/hm², test III) and other alkaline conditioners can significantly increase soil pH and reduce soil Cd extraction rate (P<0.05); application of diatomaceous earth (8.25 t/hm²) and hydroxyapatite stone (3.75 t/hm²) can also reduce the soil Cd extraction rate. Among them, the application of limestone 11.25 t/hm² could reduce the Cd extraction rate by 21%; the application of diatomaceous earth 8.25 t/hm² (experiment II) and biomass charcoal 9.00 t/hm² (experiment II) could significantly reduce the soil Cd extraction rate (P<0.05) by 10% and 19% respectively; compared with the control in Experiment III, the pH of the soil treated with lime 3.00 t/hm², calcium magnesium phosphate fertilizer 3.75 t/hm², and biomass charcoal 7.50 t/hm² increased significantly (P<0.05). The Cd extraction rate of soil treated with lime, calcium magnesium phosphate, biomass charcoal, and hydroxyapatite 3.75 t/hm² was significantly reduced (P<0.05), and it was found that the pH value of soil treated with lime was significantly higher than that of calcium magnesium phosphate fertilizer, biomass charcoal, hydroxyapatite, and other three treatments, while the soil Cd extraction rate was significantly less than the latter three. Correlation analysis results based on comparative investigations showed that the extraction rate of Cd was significantly negatively correlated with pH, and was significantly positively correlated with effective Cd content (P<0.05). The cluster analysis showed that the passivation effects of different conditioners on soil cadmium can be divided into five categories. The most passivation effects were lime 6.00, 9.00 t/hm² and GSA-4 6.00, 9.00 t/hm², which can be used first. For the actual passivation repair, the sepiolite 4.50 t/hm², zeolite 4.50 t/hm², humus 4.50 t/hm², and hydroxyapatite 3.00 t/hm² with insignificant effects are not recommended.

Abstract:To explore the response of plants at different altitudes to water and the changes of plant adaptability under climate change, we chose the typical tree species, Litsea cubeba, Corylopsis sinensis, Camellia japonica and Symplocos stellaris, in the natural succession at different altitudes in the Lushan Mountain as the research objects. We used hydrogen and oxygen isotope technology, combined with the Iso-source model, to quantify the proportion of water source contribution. The results showed that: (1) The δD value of soil water and plant water showed different seasonal characteristics, and the δD value in the dry season was more depleted than in the rainy season. The altitude effect of soil water and plant water δD value was not obvious, and the δD value of soil water generally presented the surface enrichment and deep depletion. (2) As the altitude increased, the main water sources of plants were different. In the rainy season, the ratio of Litsea cubeba to the surface layer (0—10 cm) soil water gradually increased, and the ratio of Camellia japonica to the lower layer (30—50 cm) soil water gradually increased. During the dry season, the absorption ratio of Corylopsis sinensis to surface soil water gradually decreased. (3) There were seasonal differences in the main water sources of plants, and the performance of the same plants at different altitudes was also different. At the area of 1 287 m above sea level, the contribution rate of surface soil moisture (0—10 cm) to Corylopsis sinensis in rainy season was 68.50%, while only 9.00% in dry season. However, Camellia japonica’s contribution rate changed from 3.10% to 76.50%. At the area of 1 078 m above sea level, with the alternating rain and drought, Litsea cubeba changed from uniform (0—50 cm) absorption of soil water to preferential use of surface layer (82.20%) for soil water, Corylopsis sinensis changed from mainly absorbing and utilizing the upper layer (0—20 cm, 74.40%) soil layer to uniform water, Camellia japonica from the deep layer to the upper layer (66.18%), and Symplocos stellaris from the lower layer to the surface layer (86.40%). At the area of 884 m above sea level, in the rainy season, the main water sources of Litsea cubeba, Camellia japonica, and Symplocos stellaris were 10—40 cm (88.20%), 40—50 cm (91.80%), 0—50 cm; but the surface layer was used first in the dry season. (4) Soil surface water had a certain contribution to Camellia japonica, but its contribution was lower than those of Litsea cubeba, Corylopsis sinensis, and Symplocos stellaris. 40—50 cm soil water was the main water source of Camellia japonica, and it kept coordinated growth with the other three plants; however, the other three tree species had certain water competition, and the competition degree was different at different altitudes. In summary, plant water sources had the altitude differences and seasonal effects to adapt to the constraints of different environmental factors. Camellia japonica had a coordinated water use strategy with Litsea cubeba, Corylopsis sinensis, and Symplocos stellaris. Litsea cubeba, Corylopsis sinensis, and Symplocos stellaris had water competition and the degree of competition varied at different altitudes. This research provides a scientific theoretical reference for the allocation and protection of tree species in the subtropical ecosystem, and the establishment of a coupling model of vegetation eco-hydrology in Lushan Mountain.

Abstract:The purpose of this study was to evaluate the composting efficiency and product fertilizer efficiency of agricultural wastes from different sources and provide the basis for the production of high-quality organic fertilizer. Six kinds of animal manure and seven kinds of plant agricultural wastes were selected as raw materials, and 13 composting treatments were set up to compare the differences of temperature, pH, C/N, humic acid, nutrients and the effects of composting products on the growth of Pakchoi. The results showed that the aerobic fermentation composting could meet the requirements of maturity after 45 days under the conditions of animal and plant material mass ratio of 7∶3, C/N ratio of 25∶1, moisture content of 55%~60%. Among them, TOP4 (peanut bran) and TOM1 (cow dung) treatments had the fastest temperature rise in the process of maturity, TOP1 (soybean meal), TOP3 (rapeseed cake), TOM1 (cow dung) and TOM3 (rabbit dung) treatments had the lowest C/N ratio and the most thorough maturity; TOP1, TOP4, TOM3 and TOM5 (chicken dung) treatments had the highest total nitrogen, alkali hydrolyzable nitrogen and ammonium nitrate nitrogen, and the total nutrient content of nitrogen, phosphorus and potassium was more than 8.9%. The pot experiment of different compost products showed that P4, 5 and M2, 3, 4 treatments significantly improved the quality of pakchoi and reduced the nitrate content compared with CF (equal nitrogen fertilizer). M5 (chicken manure) significantly increased the soluble sugar, soluble protein and vitamin C of pakchoi, and significantly increased the nitrate content of Pakchoi. To sum up, the decomposition efficiency of peanut bran and rabbit manure, as composting materials, was fast, and their nutrients contents were high, composting products significantly promoted the growth of Pakchoi.

Abstract:Taking Platycladus orientalis×Ulmus pumila forest (S1), P. orientalis×Prunus davidiana forest (S2), P. orientalis×Armeniaca sibirica forest (S3), P. orientalis×Robinia pseudoacacia forest (S4) and P. orientalis forest (S5), which has same afforestation period and the similar site conditions, in the Guanshan Forest Farm of Renshoushan Province in Beishan of Lanzhou City, as the research object, the ecological stoichiometric characteristics of soil and leaves and their relationship were studied based on field investigation and indoor analysis. The results showed that: (1) The content of C, N and P in the leaves of P. orientalis in different forests followed the order of S4>S3>S2>S1>S5, and the values of mixed forest were all larger than those of pure forests. The value of C∶N in the P. orientalis leaves showed the opposite trend to that of C, N and P content. The value of N∶P less than 14 indicated that plant growth in this area was generally restricted by N elements. (2) The content of soil C, N and P in different forest stands all followed the order of S4>S3>S2>S1>S5, and the values of mixed forests were all larger than those of pure forests. The soil nutrients decreased with the increasing of soil depth, and the "surface accumulation" characteristics of soil nutrients were obvious. C∶N was slightly higher than the national average level of forest soil, and C∶P and N∶P were lower than the national average level, indicating that the soil in this region was insufficient in the supply of N for plant growth. (3) Correlation analysis showed that there is no significant correlation between the changes of C, N and P content in P. orientalis leaves and the changes of C, N and P content of soil in this area, indicating that the supply of soil C, N and P had little effect on C, N and P content of P. orientalis leaves. In conclusion, the P. orientalis mixed forest had better carbon sequestration capacity and nutrient stability than pure P. orientalis forest in Beishan of Lanzhou City. The mixed forests should be constructed reasonably to promote nutrient balance during vegetation restoration in this area.

Abstract:Ecological stoichiometry focuses on the balance of chemical elements in ecological processes, in which the stoichiometric characteristics of carbon (C), nitrogen (N) and phosphorus (P) in different components are important features of ecosystem functions and processes. At present, it is not clear how the introduction of Hippophae rhamnoides (N-fixing) affects the nutrient cycling mechanism of ecosystem in N-fixing or non-N-fixing pure plantations. Therefore, two kinds of mixed forests (H. rhamnoides + Pinus tabuliformis, H_rP_t; H. rhamnoides + Robinia pseudoacacia, H_rR_p) and the pure forests of P. tabuliformis (P_t) and R.pseudoacacia (R_p) were selected. The C, N and P contents in leaf, litter and 0—100 cm soil layer were quantified, and the effects of mixed afforestation on the synergistic variation of nutrients among different components were explored. The results indicated that:(1) Compared with P_t, the C, N, P contents (p<0.05) and the N∶P (p>0.05) increased, while C∶N and C∶P decreased (p>0.05) in the leaves of P. tabuliformis in H_rP_t, indicating that H_rP_t was helpful to relieve the restriction of N and accelerate its growth rate. Meanwhile, compared with R_p, the C, N, C∶P and N∶P decreased, while P and C∶N increased of R. pseudoacacia in H_rR_p (p>0.05), suggesting that H_rR_p might enhance the absorption of P by R. pseudoacacia, but the sequestration of C and N would be decreased. (2) The C, N, P contents and N∶P of the litters in H_rP_t were significantly higher than those of P_t, and the C∶N and C∶P values were significantly lower than those of P_t, indicating that H_rP_t was helpful to accelerate the decomposition rate of litter and promote nutrient return. Compared with R_p, the C, N, P contents and their stoichiometric ratios of the litters in H_rR_p increased (p>0.05), suggesting that H_rR_p did not significantly promote the decomposition of litter. (3) Compared with P_t and R_p, the soil C, N and P contents in H_rP_t and H_rR_p increased, but C∶N and C∶P decreased (p>0.05), indicating that H_rP_t and H_rR_p were helpful to increase the utilization efficiency of N and P and improve the soil nutrient status. (4) The main stoichiometric indicators between leaf and litter had a strong synergistic effect. In addition, the correlation of N and P elements in leaf, litter and soil was more obvious than that of the C element. In summary, compared with H_rR_p, H_rP_t was more helpful to improve the supply of nutrient limiting factors and accelerate the conversion of nutrients among different components. The research results are of great significance for revealing the nutrients supply potential of the artificial mixed forest ecosystem in the Loess Plateau and formulating a reasonable forest management plan.