Abstract:In order to reveal the effect of slope gradient and surface roughness on soil erosion on the Loess Plateau, indoor simulated rainfall experiments were conducted. The five slope gradients in the experimental design were 9°, 12°, 15°, 20°, and 25°, the rainfall intensity was 1 mm/min, and the rainfall duration was 60 min. The results showed that: (1) The volume of overland runoff increased first and then decreased under all five slope gradients, with significant difference being found between the 20° and 25° slope; the drop rate of variation in surface roughness was in the order of 12°＞9°＞25°＞15°＞20°. (2) Volume of runoff was in significant exponential function relationships with slope gradient and surface roughness (ln Mw=-0.012S-0.005?Rcv+3.78, R2=0.66). (3) The yield of sediment increased first and then decreased under all five slope gradients. Sediment yield was significantly different at slope gradient of 3° slope and between the 20° and 25° slope gradient, indicating that slope gradient had a significant impact on sediment yield. (4) Yield of sediment was in significant linear relationships with slope gradient and surface roughness (Ms=0.014S-0.008Rcv+1.173, R2=0.82). (5) The regression relationship between the yield of the secondary rainfall, sediment yield and the variation of the degree of variation in roughness and the slope gradient was superior to that of relationships built using the above-mentioned parameters singly. The results provided references for revealing the mechanism of the effects of slope gradient and surface roughness on soil erosion during the process of water erosion.

Abstract:Through choosing the developing typical collapse in Tongcheng as the research object, we analyzed the condition of runoff and sediment yield and the discipline of particle size of the different soil layers in granite collapse region under the simulated rainfall experiments. The results showed that the differences between the infiltration rate and accumulative infiltration of the different soil layers were significant in the whole rainfall period; With the extension of rainfall duration ,the infiltration rate of the different soil layers decreased at first and then kept stable, and the accumulative infiltration had relatively large difference; The infiltration rate of illuvial horizon was the highest of 328.75 ml/min, which was 1.13 times of that of eluvial horizon, and 1.76 times of that of parent material horizon; Horton model could describe the infiltration rate of the different soil layers well (R2＞0.922), and the fitting results confirmed the variation process of infiltration rate of the different soil layers under the simulated rainfall conditions. The difference between the sediment yielding rate and cumulative sediment of the different soil layers was significant in the whole rainfall period. With the extension of rainfall duration, the sediment yielding rate of parent material horizon was the highest of 40.43 g/(L·min), which was 1.79 times of that of illuvial horizon, and 3.11 times of that of eluvial horizon; The cumulative sediment of eluvial horizon increased rapidly, while that of illuvial horizon showed relative slow growth; The cumulative sediment of parent material horizon increased in the whole rainfall period, which was greater than that of eluvial horizon and illuvial horizon. The particles of ＜0.2 mm showed the highest loss in different soil layers, followed by particles of 0.2 to 1 mm, 1 to 2 mm and ＞2 mm. With the extension of rainfall duration, the loss of all particle sizes of eluvial horizon decreased gradually, while that of the illuvial horizon gradually increased, and that of the parent material horizon tended to be stable. This study has important significance in theory and practice to reveal the mechanism of runoff and sediment and the research about erosion law of the different soil layers in granite collapse region. The results obtained in this paper set up the basis of the physical model in water erosion process of collapse gully.

Abstract:There are more literatures related to sheet erosion on the loess sloping and sand loess soil sloping, but there are little information on sheet erosion on the clay loess sloping. Therefore, the purpose of this study was to investigate effects of rainfall intensity and slope gradient on sheet erosion at the clay loess sloping by using simulated fainfall. The experiment treatment included two rainfall intensities (90 mm/h and 120 mm/h) and four slope gradients (10°, 15°, 20° and 25°). The results showed that under the same rainfall, effects of rainfall intensity and slope gradient on runoff rate had no significant difference; while both of them on sheet erosion had significant difference. Under the same slope gradient, when rainfall intensity increased from 90 mm/h to 120 mm/h, the sheet erosion increased 76.2%—128.0%. As slope gradient changed from 10° to 25° under both of 90 and 120 mm/h, the sheet erosion increased 29.3%—72.1% and 1.8%—75.4%, respectively. Under the same rainfall duration, when rainfall intensity increased from 90 mm/h to 120 mm/h, the runoff rate and sheet erosion increased 19.5%—26.0% and 103.8%—162.2%, respectively. A slope gradient shifted from 10° to 25°, the sheet erosion under the both of 90 mm/h and 120 mm/h increased 25.1%—67.4% and 1.8%—75.0%, respectively. The relative contribution of rainfall intensity to stable-stage sheet erosion rate was above 82%, which was much higher than that of slope gradient.

Abstract:2 typical soil in the Loess Plateau (Loess and Lou soil), 2 different rainfall intensities (45.5 mm/h and 95.5 mm/h) and 2 slope gradients (8.7% and 25.9%) were used to qualify the impact of 3 water quality (deionized, tap and saline water) on runoff and soil erosion in rainfall simulation. The results showed that the runoff rate acted differently between 2 types of soil. Tap water and saline water delayed the time of runoff yielding, but the runoff rate of deionized water grew more slowly than tap water and saline water under Loess. For Lou soil, deionized water always showed the highest runoff rate, while tap water and saline water were similar in ion amount, and did not differ in runoff rate. Water quality influence the runoff indirectly by the formation and development of crust. When precipitation was 45.5 mm, runoff amount significantly decreased with the increasing electrical conductivity, tap and saline rainwater decreased runoff depth by 5.7 mm and 1.7 mm for Loess, and by 7.2 mm and 9.8 mm for Lou soil, compared with deionized rainwater. The sediment yielding rate had significantly difference under different rainwater conditions and it was closely related to the runoff rate. Deionized water had a maximum sediment yield, while tap and saline rainwater decreased runoff depth by 45.9% and 35.8% for Loess, and by 65.6% and 68.3% for Lou. It should be noted that runoff and erosion was significantly affected by the quality of water in simulated rainfall. Deionized water was recommended for rainfall simulation to improve the accuracy and comparability of results.

Abstract:Taking the slope-farmland of purple soil in Hechuan, Chongqing and Chuxiong, Yunnan as samples, the study analyzed the soil water storage, soil stability and tilth characteristics based on field survey and lab tests. The results showed that: (1) Soil infiltration rate decreased with the increasing depth of cultivated-layer of purple soil in slope-farmland, and the soil stable infiltration rate of the 0—20 cm, 20—40 cm, 40—60 cm cultivated layer was 5.80 to 9.58 mm/min, 2.81 to 4.35mm/min, and 0.98 to 1.96mm/min, respectively. The maximum effective water storage capacity of soil was 49.93 to 66.26, 46.04 to 59.05, and 37.42 to 43.55 mm at corresponding soil depth. (2) Soil stability of cultivated-layer was significantly different among purple soil farmlands. The＞5 mm, 5 to 3 mm, and 3 to 0.5 mm fractions were dominant soil aggregate structure, and the content of ＞0.25 mm fraction of water stable aggregates decreased with increasing cultivated-layer depth significantly. Soil stability index of the 0—20 cm cultivated-layer varied and followed the order of high-yield tobacco cultivated-layer (2.96)＞high-yield maize cultivated-layer (2.55)＞low-yield tobacco cultivated-layer (2.45)＞low-yield maize cultivated-layer (2.38). Compared with that of the 0—20 cm soil layer, the stability index of the 20—40 cm and 40—60 cm layer of maize and tobacco decreased by 0.44, 0.64 and 0.66, 0.71, respectively. (3) The soil shear strength and the penetration resistance of cultivated-layer on different slope-farmland was significantly different (p＜0.05), and the soil shear strength was in the order of low-yield maize cultivated-layer (36 kPa)＞high-yield maize cultivated-layer (29 kPa)＞low-yield tobacco cultivated-layer (25 kPa)＞high-yield tobacco cultivated-layer (21 kPa), with the peaking value appearing in the 20—40 cm layer. Soil penetration resistance of high- and low-yield cultivated-layer was 0.3 to 1.9 Mpa and 0.5 to 2.5 MPa, with the peaking value appearing in the 40 to 50 cm layer. The high-yield cultivated-layer of purple soil slope-farmland presented high stable infiltration rate, large storage capacity, strong soil water holding capacity, high soil structure stability, low soil anti-shear strength and penetration resistance.

Abstract:The aims of the present study were to maximize the reduction of nitrogen loss from farmland and protect the main source of drinking water and stream water quality for Hexi reservoir. Site-specific observation was carried out in the present study, plots for nursery land with six fertilization management modes were selected, including broadcast placement (contrast), plastic mulching, straw mulching, setting buffer for planting grass around nursery land, band placement and hole placement, to explore the influence of different fertilization management mode on nitrogen losses in surface runoff and screen the best fertilization management mode in the catchment area of Hexi reservoir. The results showed that: under different fertilization management modes, the order of the concentration of annual nitrogen loss in the runoff was: broadcast placement (contrast)＞plastic mulching＞band placement＞hole placement＞setting buffer for planting grass around nursery land＞straw mulching. The mean annual runoff load of total nitrogen from broadcast placement (contrast), plastic mulching, band placement, hole placement, setting buffer for planting grass around nursery land and straw mulching was 35.61, 18.30, 15.86, 12.94, 8.18, 3.44 kg/(hm2·a), respectively. The results indicated that hole placement, setting buffer for planting grass and straw mulching were better fertilization management modes, which would significantly reduce nitrogen runoff from non-point source output of nursery land and weaken the potential impact on water quality of Hexi reservoir by optimum combination of the above-mentioned better fertilization management mode in nursery land in the catchment area of Hexi reservoir in Changxing county. In addition, particulate nitrogen was the dominant form of nitrogen loss in the runoff, followed by nitrate nitrogen under all fertilization management modes. Furthermore, for the management mode of broadcast placement(contrast), plastic mulching, straw mulching, setting buffer for planting grass around nursery land, band placement and hole placement, annual loss of particulate nitrogen in the runoff accounted for about 69.11%, 68.87%, 68.04%, 61.89%, 61.17% and 65.09% of the total nitrogen losses, respectively; annual loss of nitrate nitrogen in the runoff accounted for about 23.18%, 23.36%, 20.21%, 27.20%, 32.02% and 28.71% of the total nitrogen losses, respectively.

Abstract:In order to understand the effects of planting modes and agriculture drainage ditches, nitrogen and phosphorus concentration, and suspended solids characteristics of the runoff in different types of agriculture drainage ditches from different planting area (vegetable area, corn field and greenhouse area) in the Chaihe watershed were analyzed based on the survey and monitoring of water samples under natural rainfall. The main results are as follows: (1) The average total nitrogen(TN) and total phosphorus(TP) contents (27.16 mg/L and 17.18 mg/L) in runoff were much higher than class V surface water quality standard limits in China, and the dissolved nitrogen (DN) and particulate phosphate were the main pollutants; (2) Rainfall was one of the most important factors influencing runoff pollutant contents, and planting mode also had the significant effect on TN, DN, and dissolved phosphorus (DP) (P＜0.05); (3) When the rainfall was the same (18.05 mm), the higher contents of nitrogen in runoff from vegetable area and greenhouse area (TN: 32.26 mg/L, 29.02 mg/L; DN: 21.33 mg/L, 17.46 mg/L) and the higher phosphorus contents from vegetable area (TP: 17.46 mg/L, DP: 2.16 mg/L) were found. In addition, we also found that natural ditches would significantly decrease the contents of total phosphorus, dissolved nitrogen, and dissolved phosphorus (P＜0.05). In conclusion, planting mode was one of the main factors influencing non-point source pollution in the same rainfall. Though ditch can decrease effectively non-point source pollution, the contribution of ditch was less than the planting mode. Based on the above results, the planting structure of the watershed should be optimized at first, and then the transform of the existing ditches and the promotion of the ecological level are also needed to increase the control efficiency of the non-point source pollution.

Abstract:A conservation tillage experiment was carried out in the sloping fields in Chongqing in order to explore the influence of conservation tillage on water loss and soil erosion, so as to provide some suggestions for soil and water conservation in Chongqing area. The field experiment was carried out in 2015 in Shizhu, Chongqing. The flue-cured tobacco variety Yunyan 87 was planted in the whole testing area, and sloping ridging was used. There were four treatments, i.e. T1, in which Lolium multiflorum Lam. was not grown, T2, in which L. multiflorum was grown between ridges, T3, in which L. multiflorum was grown on the rdiges, and T4, in which L. multiflorum was grown both between ridges and on the ridges. The results showed that growing L. multiflorum between ridges could effectively reduce runoff by 58.66% to 65.79%, sediment yield could be reduced by 62.50% to 68.78%, and the loss of NO3--N, NH4+-N, phosphorus and potassium in runoff could be reduced by 52.05% to 57.22%, 51.03% to 59.98%, 51.47% to 65.88%, and 66.93% to 69.33%, respectively. When L. multiflorum was grown on the rdiges, the runoff, the sediment yield, the loss of NO3--N, NH4+-N, phosphorus and potassium in runoff could be reduced by 54.32% to 61.59%, 52.95% to 62.98%, 63.73% to 77.49%, 59.12% to 67.81%, 62.84% to 76.22%, and 75.17% to 77.84%, respectively. When L. multiflorum was grown both between ridges and on the rdiges, the runoff, the sediment yield, the loss of NO3--N, NH4+-N, phosphorus and potassium in runoff could be reduced by 92.09% to 98.25%, 86.43% to 95.91%, 87.89% to 94.99%, 90.19% to 97.06%, 81.99% to 91.94%, and 91.52% to 93.88%, respectively. Overall, growing L. multiflorum both between ridges and on the rdiges is the best way of soil and water conservation.

Abstract:We tried to compare the soil and water conservation effects of plastic film mulching with some traditional measures for controlling the soil and water erosion in economic forest, such as green manure mulching, grass coverage, biological hedge, and paraquat application. We tried to explore the feasibility of plastic film mulching on preventing soil and water erosion in Castanea henryi plantation, using erosion needles and observation in runoff plots at the same time. The results showed that the soil erosion and nutrient loss of 5 different treatments were all significantly less than the control treatment as the extension of processing time. The liquid runoff of green manure mulching and paraquat application measures were both less than the other 3 treatments. The liquid runoff of plastic film mulching was more than the other measures when soil loss was the least for low level of rainfall infiltration, and soil loss of paraquat application was less than the other traditional measures. We also analyzed the spatial heterogeneity of soil erosion on the slopes. We found that net sediment on the slopes of green manure mulching, biological hedge and paraquat application reduced gradually as the extension of processing time. But all the different slope positions of grass coverage and plastic film mulching showed net deposition obviously. On the other hand, so much liquid runoff of plastic film mulching did not take too much nutrient away because the mulch could separate nutrient from rainfall. Only the content of total phosphorus, total potassium and ammonium nitrogen in liquid runoff in May and June were more than the control treatment when the liquid nutrient loss were less than the control treatment significantly from July to October. The soil nutrient loss of plastic film mulching was also less than the other measures. Moreover, plastic film mulching could reduce the labor costs by reducing the time to harvest. Therefore, we think that plastic film mulching had significant effect in reducing slope soil erosion and nutrient loss, and it had certain superiority in soil and water conservation of Castanea henryi. But it had a tendency to increase erosion for liquid runoff on the film, so practical use of this measure should be restricted. In our opinion, we can set up the proportion of mulch, using a porous membrane or micro-engineering on slopes to reduce liquid runoff, to achieve the best effect of plastic film mulching.

Abstract:To clarify wind erosion condition and impact factor, based on wind erosion theories and GIS technologies, this article selected opencast mine area of east Junggar Basin (Zhundong) as the study area, took the environment conditions of the study area into consideration, used field observation data and combined with meteorological data, the land use data, DEM, and remote sensing image to analyze the influence of soil wind erosion from 4 aspects: climate, soil, landform and vegetation coverage. In addition, the paper carried out a quantitative research on 4 impact factors, and used WEQ model in the study area with impact factors to evaluate and analyze the erosion grade. The results showed that: influenced by various factors, the wind erosion classification was obvious in study area, and erosion intensity showed a trend of increase from south to north. Severe erosion was the main erosion degree, accounting for 43.02% of the area. The average erosion modulus was 4 470.64 t/(km2·a), with wind erosion amount reaching 99.695 3 million tons. In order to verify the accuracy of the models, 137Cs trace method was used to comparatively analyze the model value. The verification results showed that the average relative error between 137Cs tracer method and the model value was 7.78%, proving that the model in the study area had good applicability.

Abstract:In order to provide theoretical basis for scientific prevention and control of sand dune hazard, in this paper, lab analysis and wind tunnel simulation were used to study the effects of sand moisture content on surface roughness length, wind velocity profile and structure of drifting sand flux in the Hobq Desert. According to the real dynamics of wind tunnel, the inlet wind speeds were set to be 6, 8, 10, 12, 14, 16 m/s. In addition to dry sand, artificially mixed sand, of which the moisture content was 0.25%, 0.5%, 1%, 1.5%, 2% and 2.5%, was also used for the wind tunnel simulation experiment. The results showed that the surface roughness length increased with the increasing wind speed and overall showed a trend of decrease with the increasing moisture content. Wind velocity profile showed a logarithmic distribution with height. As the wind speed increased, the logarithmic rule of wind velocity profile became better, wind velocity gradient decreased. When the moisture content increased, the absolute sand transport rate with the increase of wind speed decreased, but the relative value increased. As a whole, sand transport rate decreased with increasing moisture content. Under all moisture conditions, sand transport rate decreased with increasing height; when the moisture content reached 2.5%, the wind erosion process almost stopped, regardless of the height. About 80% of dry sand transport occurred within the first 5?cm near the surface, but when the moisture content increased, a higher proportion of sand transport occurred below 5 cm; when the moisture content was between 0.25% and 1.5%, sand transport occurred in the 5 cm to 8 cm layer near the surface accounted for more than 30% of the total sand transport. Our results indicated that the mechanical sand prevention measures which can increase the surface roughness length should be used in the Hobq Desert, and the height of the sand fixing measures should be higher than that in other deserts.

Abstract:To explore the changes in rill erodibility (K value) among soils in waste dump land, shrub grassland and cultivated land, soil samples were collected in the shrub grassland and cultivated land without mining, and waste dump land of Hongge Longmang Mine of Yanbian County, Panzhihua City. A series of scour experiments were carried out to simulate rill erosion process under water discharge rates ranging from 100 ml/min to 600 ml/min in the study area. Changes in soil detachment rate under drainage, saturated and seepage conditions were also measured. Results showed that a significant exponential relationship between flow shear stress and soil detachment rate appeared (P＜0.01). Meanwhile, a significant exponential relationship between flow discharges and soil detachment rates was also observed (P＜0.01). For the soil of shrub grassland, K values were estimated at 0.000 2 m/s, 0.000 5 m/s, and 0.000 9 m/s under drainage state, saturated state and seepage state, respectively, while the K values for soil of cultivated land were estimated at 0.000 3 m/s, 0.000 9 m/s, and 0.001 8 m/s, respectively. Meanwhile, for the soil of waste dump land, K values were estimated at 0.002 3 m/s, 0.066 9 m/s, and 0.094 6 m/s under drainage state, saturated state and seepage state, respectively. Those results indicated that K values for the soil of waste dump land were higher than those for the cultivated land and shrub grassland. Significant differences in the rill erodibility were observed among soils in the 3 land use types due to different soil particle sizes. For all soils, soil K values were the highest under seepage condition due to high vertical hydraulic pressure, while soil K values were the lowest under drainage condition due to low vertical hydraulic pressure. At the same time, K values for soil under saturated condition was higher than that under drainage condition, which may be because higher vertical hydraulic pressure appeared under saturated condition than under drainage condition. These results indicated that K values of rill erosion varied among different vertical hydraulic conditions and impacts of hydraulic gradient of groundwater on soil erosion process should be paid more attention in further studies.

Abstract:In order to quantitatively analyze and reveal the present spatial distribution of soil erosion sensitivity, identify key areas for the loss of water and soil in Leishan county which belongs to the key ecological function area, and provide theoretical basis for comprehensive prevention and control of soil and water loss and ecological environment, this study selected the ALOS images in Oct 2010, and 1:50 000 topographic map which covers the whole Leishan county as the data source. Through using the geospatial information technology (RS and GIS) combined with 3D analyst grid calculation function, Leishan County’s DEM, slope gradient, slope aspect, land use and other main factors were extracted. By using ENVI software, combined with the normalized difference vegetation index model, the vegetation coverage was extracted. The spatial overlay analysis in ArcMap was used to divide water and soil erosion sensitivity level, quantitatively analyze its sensitivity in present situation, and reveal its spatial distribution. The results showed that: the slightly and highly sensitive area of soil erosion was 812.29 km2, accounting for 67.45% of total area in Leishan country, and the sensitivity of soil erosion was mainly slight in most areas of the county. The highly sensitive area of soil erosion was small, accounting for 5.96% of the total area. At the same time, there was a significant relationship between different elevation, slope aspect, slope gradient, vegetation coverage level and the sensitivity of soil erosion in the study area. The slightly and highly sensitive soil erosion area appeared single peak distribution which increased at first then decreased. The sensitive soil erosion area occurred mainly in the altitude range of 800 to 1 400 m, with the southeast and the northwest slope and the slope degree of 15 to 35, and the vegetation coverage level in 30% to 45%.

Abstract:In view of the fact that the global change which was mainly marked by warming resulted in that the climate change rate was increased, the extreme weather and climate events and disasters were more frequent, and the risk of population, agricultural economic production and infrastructure were enlarged. A case on the characteristics of extreme rainfall in Yan’an of 2013 and its severe erosion on the terraces was analyzed which was based on years of daily rainfall data of Yan’an station and terraces erosion field measuring data. The results were showed as bellows: (1) The total extreme rainfall of Yan’an in 2013 reached 959 mm, 448.8 mm higher than the mean annual rainfall (1951—2012). Rainfall from July to September reached 761 mm, which accounted for 79.4 % of the whole year and among which the maximum monthly rainfall happened in July (568 mm), reaching the standard of million years; (2) The number of the erosive rainfall and rainstorm was much more than before and the total amount of rainstorm was large. Meanwhile, the extreme rainfall showed new changes of short duration and moderate intensity, moderate duration and high intensity, long duration, strong erosion and weak sediment transport; (3) The contiguous terraces were eroded seriously in the extreme rainfall. The soil erosion modulus of terrace had significant correlations with relative elevation and catchment area. The erosion of the moderate and lower terraces was serious and the maximum soil erosion modulus reached 54 049.50 t/km2. This study would provide the basis for the design of agricultural soil and water conservation terrace engineering, and also provide support to take permanent and temporary measures to prevent the extreme rainfall under climate change conditions.

Abstract:To explore the effect of litter mulch on preserving soil water and its mechanism in red soil sloping-land, in situ experiments were conducted in sloping-land of red soil derived from Quaternary red clay in De’an County in northern Jiangxi Province, the effects on soil water retention capacity, soil water supplying capability and soil water availability of the 0—60 cm soil layer was studied after the litter mulching measure had been implemented for 15 years, with the bared slope being used as the control. The results showed that soil water retention capacity of red soil in northern Jiangxi Province was low, water supplying capability was weak, and soil water availability was low, i.e from 9.0% to 11.1%. The water retention capacity of the upper layer of the soil (i.e. the soil within 0—30 cm depth) on the red soil slope was higher than that of the bared slope. The water supplying capability of the lower layer of the soil (i.e. the soil within the 30—60 cm depth) of the red soil slope with litter mulch was higher than that of the bared slope when the soil water suction was less than 100 kPa. Litter mulch effectively increased the soil water retention capacity of the red soil, especially for the upper layer, and also enhanced the water supplying capability of the upper layer of the soil under relatively wet conditions, but had relatively weak effects on soil moisture availability. The results of this study can provide guidelines for the optimization of the surface mulching measures of sloping cropland, increasing and maintaining soil water resources, and reasonable exploitation and utilization of red soil slopes in southern China.

Abstract:Based on the profiled soil physical/chemical and hydraulic properties measurement, the characteristics of water percolation and conservation in different aged paddy fields in the Jianghan Plain were investigated, and the paddy fields were of 17 years (new paddy field, NF) and more than 100 years (old paddy field, OF), respectively. The results were as follows: (1) Water percolation was more likely to occur in the NF. The higher average saturated hydraulic conductivity (Ks) in the NF (32.05 cm/d) was observed than that in the OF (17.91 cm/d). The highest Ks was observed in the plow layer, followed by the subsoil layer, and the lowest Ks was in the plough pan. The Ks of plow layer was 6.3 and 5.7 times of the plough pan and subsoil layer for the NF, and 6.9 and 4.0 times for the OF, respectively. (2) Higher water capacity was observed in the OF than that in the NF. The highest water capacity was identified in the plough pan, followed by the subsoil layer, and the lowest was found in the plow layer. However, the macropore distribution showed the opposite law. (3) The available water content decreased with the decreasing soil depth in the NF and OF, with higher values observed in the OF. In addition, higher total water capacity and flooding control capacity were also observed in the OF. The water shortage stress and groundwater pollution risk were increased by the land transformation from the non-irrigated farmland to the paddy field.

Abstract:A series of flume experiments were conducted at the condition of different runoff discharge, slope gradient and slope length. The Purple soil with a clay texture is the typical soil in the upper reaches of the Yangtze river.The flume with the size of 30 cm wide and 10 m long were used.eleven slope lengths including 0.5 m, 1 m, 2 m, 3 m, 4 m, 5 m, 6 m, 7 m, 8 m, 9 m and 10 m were used. The flume were divided into 3 rills and the rill width is 10 cm. Three slope gradients including 5°,15° and 23°and three flow discharges with 5 L/min, 15 L/min, 25 L/min were used in the experiments. All experiments were repeated three times and there were total 297 test sessions. The results showed that rill erosion was affected by flow hydraulic characteristics, soil properties and slope characteristics, with the increase of flow sediment concentration, the rill erosion rate showed a trend of decrease; The greater the flow rate and slope gradient, the bigger rill flow detachment and the rill erosion rate. Under the condition of 5 l/min of small flow discharge, rill erosion rate restricted by detachment rate and had no strict linear relationship with sediment concentration, but under condition of 15 l/min, 25 l/min, rill erosion rate was linear correlation with sediment concentration. At the beginning of the rill, the rill erosion rate is the biggest, with the increases of rill length, the flow energy consumption for sediment transport, so sediment detachment decreased rapidly. The rill erosion rate and the rill length had a exponentially decreasing relationship by correlation analysis, and the correlation coefficient R2 changed between 0.45 to 0.98. By regression analysis, the average purple soil erodibility was 0.005 3 s/m, and the average critical shear stress was 2.92 Pa under experimental condition. The results provide data support for establishment and application of distributed physical model and serve as the further research of slope soil erosion of purple soil.

Abstract:Taken the severe saline-alkali soil of the Yellow River Delta as research soil sample, vertical one-dimensional ponding infiltration experiments were conducted in the laboratory to study the change laws of cumulative infiltration, wetting front depth and infiltration rate with time, soil desalting depth, and desalting rate after irrigation under five distribution proportions between brackish and fresh water. The results showed that: (1) After the first round of brackish water infiltration finished, compared with all brackish water irrigation at the same time, cumulative infiltration, wetting front depth and infiltration rate obviously declined after the second round of fresh water irrigation, in addition, the more fresh water used for the irrigation, the more obviously these parameters declined, but these parameters were still significantly higher than those for all fresh water irrigation. (2) Cumulative infiltration had good linear relationship with wetting front depth, with all coefficients of determination of regression equations being greater than 0.99. Kostiakov formula was more suitable for describing the relationship between infiltration rate and time than Green-Ampt model and Philip model. (3) Distribution proportion between brackish and fresh water had slight effect on soil desalting depth, but it had significant effect on desalting rate within soil desalting depth. Soil desalting rate under successive brackish and fresh water irrigation was far greater than all brackish water irrigation and was slightly different from that under all fresh water irrigation within a certain depth range, but it was obviously less than that under all fresh water irrigation and essentially equal to that under all brackish water irrigation when soil layer depth further increased.

Abstract:In order to explore the redistribution processes of rainfall that were caused by canopy, five typical forest types in the upper reaches of the Hun River, including Korean pine plantation (KP), larch plantation (LP), broadleaf-Korean pine mixed forests (BKMF), broadleaf-larch mixed forests (BLMF) and broadleaved mixed forests (BMF) were studied. Throughfall, stemflow and canopy interception were recorded by automatic data recorder. The results showed that the throughfall, stemflow, and canopy interception in five typical forests increased linearly with an increase of rainfall. The rate of throughfall and stemflow logarithmically increased as rainfall increased. The stemflow in BKMF (32.12%) and BLMF (15.44%) was higher than those in KP, LP, and BMF. The canopy interceptions in KP (80.66%) and LP (77.47%) were higher than those in the other three forest types. This study provides the theoretical basis for the configuration of water conservation forest with the optimal spatial pattern and management strategies in the upper reaches of the Hun River.

Abstract:In this study, surface soil and underground leakage water and soil were monitored and sampled for analysis over 3 caves in rocky desertification area in Guizhou, to research the physicochemical properties of surface soil and cave leakage water and soil under different geological environments. Results indicated that severe surface rocky desertification led to strong connectivity in fissure conduits of karst and large variation in drip rate of underground leakage water and soil, together with low clay content in leakage soil; pH and element contents became higher with more severe rocky desertification under the same lithology condition; mean values of Ca2+, Mg2+, and Sr2+ in leakage water were 31.48 mg/L, 17.65 mg/L, and 0.026 mg/L in Shijiangjun Cave, 58.39 mg/L, 2.49 mg/L, and 0.074 mg/L in Hanjiachong Cave, and 38.29 mg/L, 25.33 mg/L, and 0.037 mg/L in Rongfa Cave, respectively; the concentration of Mg2+ was low and those of Ca2+ and Sr2+ were high in Hanjiachong Cave for the influence of lithology difference, while the concentrations of Ca2+, Mg2+ and Sr2+ in leakage water of Rongfa Cave were higher than those of Shijiangjun Cave, which was influenced by weather condition; pH and element contents in leakage soil were higher than those in surface soil, which was the result of long-term chemical erosion of cave leakage water to leakage soil.

Abstract:Prunus armeniaca is a main shrub species of ecological and economic plantation in semi-arid area in western Liaoning Province. A water use strategy, including the main water source which a plant species utilizes and water use efficiency (WUE), plays an important role in plant survival and growth. Understanding the water use strategies of a shrub plantation can be used to evaluate the sustainability and long-term stability of the plantation. Stable oxygen isotope ratios (δ18 O) of water in rain, well, branch xylem, and in soil at different depth of 5, 11- and 17-year-old P. armeniaca plantation were tested to trace the main water source of P. armeniaca. Root systems were investigated to determine the depth of the main distribution. Leaf carbon isotope ratios (δ13 C) were used to evaluate the long-term WUE of P. armeniaca plantation. The results showed that 5- and 11-year-old P. armeniaca plantations mainly derived soil water from the 0—30 cm layer, which were coincident with the distribution of their fine roots. Conductive root systems of 5- and 11-year-old P. armeniaca plantations were distributed primarily in the 20—50 cm layer. 17-year-old P. armeniaca plantations derived water mainly from the 0—20 cm and 50—70 cm layers, with their fine root and conductive root system being distributed primarily in the 0–30 cm and 10–70 cm layer, respectively. The δ18 O values indicated that these sources of soil water were recharged by rainfall and groundwater. The long-term WUE of 5-year-old plantation (-24.1‰) was greater than those of the 11- and 17-year-old plantations (P＜0.05). The water use strategies suggested that P. armeniaca plantation can adapt to a semi-arid environment of western Liaoning Province by changing its water use strategy over time.

Abstract:Shrubs are important components of the forest in the upper reaches of Bailongjiang River. Previous studies on water holding characteristics in this region were focused more on the arbor forest, but less on shrubberies. By means of field survey and soaking extraction, five typical shrubberies (Viburnum dilatatum Thunb., Salix fargesii Burk., Salix cathayana Diels., Fargesia spathacea Franch., Spiraea schneideriana Rehd.) were selected for the present study. The results showed that litter storage in the five typical shrubberies followed the order of F. spathacea＞S. fargesii＞V. dilatatum＞S. cathayana＞S. schneideriana. The half-decomposed litters had a larger water holding capacity than un-decomposed litters in the five typical shrubberies. The water holding capacity of S. cathayana un-decomposed litters was the highest among different shrubberies, the half-decomposed litters of F. spathacea was the highest among different shrubberies, the un-decomposed and half-decomposed litter layers of S. schneideriana were both the lowest among different shrubberies. The maximum water holding capacity of the whole litter layer was in the order of S. cathayana＞F. spathacea＞V. dilatatum＞S. fargesii＞S. schneideriana. Water holding capacity of the litters of different decomposition degree changed logarithmically with soaking time, and the water absorption rate followed a power function.

Abstract:In order to explore the effects of varying thinning intensities on litter hydrology in Larix principis-rupprechtii Mayr plantations, a study was conducted in Haodifang Forest Farm, Taiyue Mountains, Shanxi Province. Sample site investigation and laboratory soaking method were used to analyze litter reserves, litter water retention characteristics, litter water holding capacity and absorption rate and their relationships with soaking time for the un-decomposed litter layers and half-decomposed litter layers under different density regulations. The results showed that: (1) The litter reserves showed an order of low thinning (LT)＞moderate thinning (MT)＞heavy thinning (HT)＞control (CK), indicating that different density control had a positive effect on forest litter production. (2) The maximum water holding rate in CK, LT, MT and HT was 214.30%, 219.28%, 256.95% and 249.50%, respectively. The maximum water holding capacity was 125.24 t/hm2, 186.24 t/hm2, 197.68 t/hm2 and 157.96 t/hm2, respectively. The effective water retaining content was as followed 56.06 t/hm2, 72.46 t/hm2, 82.59 t/hm2 and 58.47 t/hm2. (3) The water holding capacity in half-decomposed litter layers was higher than that in un-decomposed litter layers, but different density control had little effects on water holding process in un-decomposed litter layers. The water holding capacity under MT control was obviously higher than that under LT, HT and CK in half-decomposed litter layers. (4) The absorption rate and soaking time showed a power function. Half-decomposed litter layers had higher water holding capacity than un-decomposed litter layers. There was no significant difference in litter water absorption rate among different density controls.

Abstract:The studies on revision of parameters of SCS-CN model have been done by lots of scholars in China, but most of them focused on using different methods to revise 1 of the 2 parameters. In order to investigate whether the simulated result obtained from revising the 2 parameters at the same time is better than only revising 1 parameter, and also to identify the applicability of SCS-CN model under 4 different kinds of land use, this paper chose Shixia small watershed, which is the upper area of Miyun Reservoir watershed, as the study area, and the monitoring data during 2006 to 2010 of Shixia small watershed was collected. 8 equal interval of initial abstraction ratio value from 0.05 to 0.4 was selected, and by using the arithmetic mean method, the curve number values of 8 different initial abstraction ratios were calculated respectively. This paper also evaluated the applicability of SCS-CN model in study area under 4 different kinds of land use by taking Nash efficiency coefficient as criterion. The results showed that: (1) In the study area, when the initial abstraction ratio values were 0.05 under 4 different types of land use conditions, the Nash efficiency coefficient were the highest, which were 0.75, 0.48, -1.11 and -0.24 under bare land, cropland, grassland and, respectively. (2) When we adopted SCS-CN model to predict runoff in upper area of Miyun reservoir, the recommend values of curve number under bare land, cropland, grass and woodland were 86, 73, 58, and 63, respectively. And the recommend values of initial abstraction ratio under 4 land use patterns were all 0.05. (3) The simulation results of the SCS-CN model could be improved to a certain extent by revising the 2 parameters at the same time. (4) SCS-CN model could be adopted in bare land and cropland in Shixia small watershed, but was not recommended to be adopted in grassland and woodland.

Abstract:Research on effects of fertilization with mulching on water and nitrogen use efficiency in the field and maize yield is of great significance to increasing crop yield. For better understanding the effects of drip fertigation with straw mulching on water and nitrogen use efficiency under heat conditions in the field and summer maize yield in semi-humid regions, field experiments were carried out in Daxing district of Beijing city, China, during the growing seasons of summer maize in 2014 and 2015. In the experiments, six treatments, including no fertilization with straw mulching (T1), no fertilization without straw mulching (T2), middle fertilization with straw mulching (T3), middle fertilization without straw mulching (T4), high fertilization with straw mulching (T5), and high fertilization without straw mulching (T6) were tested. The results showed that: surface soil temperature and air temperature had a high linear correlation, and straw mulching could reduce soil warming rate during the growing season of summer maize. Compared with that in T2, T4 and T6, soil warming rate in T1, T3 and T5 decreased by 23.62%, 13.65% and 11.47%, respectively. During the whole growing season, average daily soil temperature in treatments with straw mulching was 1.75 ℃ lower than that in treatments without straw mulching. Under drip irrigation, straw mulching could affect the distribution of soil moisture in the 0—60 cm soil layer, especially for soil moisture content of the 0—20 cm soil layer. In 2014, average soil water content was increased by 11.73%, and the average increase was 9.56% in 2015. In treatments with straw mulching, E/ET was decreased by 6.99% on average when compared with treatments without straw mulching, and water consumption of summer maize was the highest from the heading to grain-filling stage. The results indicated that T3 had the highest grain yield, being 27.62% higher compared with that of T2, and 15.83% higher than that of T6, T3 also showed optimal water use efficiency and fertilizer partial productivity, which was 23.73 kg/（hm2·mm）and 40.33 kg/kg, respectively. In conclusion, middle fertilization with straw mulching can reduce soil warming rate under drip irrigation, it can increase maize yield and at the same time show optimal water use efficiency and fertilizer partial productivity.

Abstract:Gully morphological characteristic indicators are important parameters to study gully erosion processes quantitatively, but there are only a few reports on the study of gully morphological characteristics at active stage due to the limitation of DEM resolution. 30 typical gullies were randomly selected in different watershed locations and gully orders. Extraction method of gully morphological characteristic indicators was established based on the 3-D laser scanning technique (LIDAR), differences of gully morphological characteristic indicators extracted from 0.1 m and 5 m DEMs were analyzed and transform models of gully morphological characteristic indicators between different resolution DEMs were established. The results showed that gully morphological characteristic indicators extracted from 0.1 m-resolution DEM and manual measurement had no significant difference; gully length, width, depth, surface area and volume extracted from 0.1 m resolution DEM was 94.0%, 109.1%, 107.7%, 80.1% and 109.0% of that obtained by manual measurement, indicating that 0.1 m-resolution DEM could be used to extract gully morphological characteristic indicators accurately. Gully length extracted from 0.1 m-resolution DEM had no significant difference with that extracted from 5 m-resolution DEM, while gully width, depth, surface area and volume extracted from 0.1 m-resolution DEM had significant difference with those extracted from 5 m-resolution DEM. Gully width, surface area and volume extracted from 5 m-resolution DEM was 28.6%,25.6% and 19.7% greater than that extracted from 0.1 m-resolution DEM, respectively, while gully depth extracted from 5 m-resolution DEM was 37% smaller than that extracted from 0.1 m-resolution DEM. Therefore, transform models of gully width, surface area and volume were established. Model validation results showed that the correlation coefficients of gully width, surface area and volume transform model were all greater than 0.6 and effectiveness coefficients were all greater than 0.5, indicating that the accuracies of the three transform models were all acceptable. This study provides an important method for the study of gully erosion characteristics in the loess hilly-gully region.

Abstract:In this study, we uses hydrogen and oxygen stable isotope tracer technique to determine the water isotopic compositions of precipitation, soil water at different depth and stalks of summer corn during the growing season in 2015 in Yucheng, Shandong Province. On the base of these measurements, using direct comparison and multivariate linear regression methods, we analyzed the sources of summer corn root water uptake and their contributions, and further discussed field water movement and transference laws in the precipitation-soil-crop continuum. The precipitation isotope measurements showed that the atmospheric precipitation equation was δD=6.55δ18O-3.03 (R2=0.88) for Yucheng area. The analyses of water source during the growing period showed that summer corn mainly used surface (0—15 cm) soil water during the seedling stage and the contribution rate was 73.9%; during the jointing stage, it mainly imbibed water from the 0—50 cm soil layer (81.8%), and the water from the 30—55 cm soil layer was used relatively more. In addition, the precipitation was also significantly used during this period. In contrast, the water used was mostly from deeper soil layer during the heading stage (30—55 cm, 71%). During this period, the evaporation was high and soil water content decreased rapidly in the shallow soil layer, and water that could be used by plants was less. Because the water content in the deeper soil layer (30—100 cm) was less affected by air temperature and soil evaporation, it could provide water for summer corn during the heading stage stably. During the filling stage, the amount of soil water absorbed from each layer was similar (15—100 cm, 72%); the precipitation was small, the temperature dropt and the evaporation decreased, and soil water content in each layer was relatively stable. During the mature stage, the summer corn mainly absorbed water from the 30—100 cm soil layer and the contribution rate was 70%, indicating that the absorption of soil water of summer corn mainly relied on deeper soil layers when the precipitation was small. Furthermore, the results showed that the water sources of summer corn were significantly affected by soil water content and soil evapotranspiration, meanwhile, precipitation, air temperature and humidity affected soil water content. The water balance model showed that the evapotranspiration of summer corn during the seedling, jointing, heading and filling stage was 35.62, 34.99, 32.4, 22.31, 16.94 mm, respectively. This study presents guidelines for summer corn water-saving irrigation during different growth stage in Yucheng area.

Abstract:Rainfall can be partitioned into 3 parts through the vegetable canopy: throughfall, stemflow, and interception. In this study, an experiment was carried out in Pailugou watershed in Qilian Mountains in the arid region of northwest China. In a Berberis diaphana and Caragana tangutica shrub stand, throughfall, stemflow, and canopy interception of 38 rain events were observed from 1 June to 31 September, 2014. Then, we analyzed the characteristics of rainfall canopy partitioning and their influence factors. The results showed that: (1) The throughfall, stemflow and canopy interception of individual Berberis diaphana shrub were 175.2 mm (46.3%), 20.8 mm (5.5%) and 182.6 mm (48.2%), respectively, while those of individual Caragana tangutica shrub were 239.1 mm (65.0%), 15.1 mm (4.1%) and 113.4 mm (30.9%), respectively. Meanwhile, the interception ratio of Berberis diaphana and Caragana tangutica community were 29.3% and 18.6%, respectively. (2) The amount of throughfall, stemflow and canopy interception of individual Berberis diaphana and Caragana tangutica shrub showed a significant positive linear correlation with rainfall amount (P＜0.01). The relationship of throughfall ratio and interception ratio of shrubs with rainfall amount could be fitted with logarithmic curve (P＜0.05). (3) The critical rainfall amounts for the occurrence of throughfall under Berberis diaphana and Caragana tangutica shrub were 1.2 mm and 0.9 mm, respectively. Meanwhile, stemflow generated when the rainfall in early period was 2.0 mm. (4) The interception ratio for 2 shrubs showed that the maximum values were achieved in September, with the second highest values in July, and the minimum values in June and August. In addition, the stemflow ratio changed slightly from June to August, while it decreased obviously in September.

Abstract:This study took Shangnan County, located in the upper reach of the Yangtze River, as the experimental research area, using Quantitative Remote Sensing Model（QRSM. Digital elevation model (DEM) of the research area was constructed with a GIS software platform, with the gradient and slope length factor (SL) derived based on the soil erosion factor algorithm-specific software. The factors influencing the generation of the high precision digital elevation model (DEM) were analyzed. The accuracy and error of the produced DEM were also checked. In particular, the solutions to the derivation of the terrain pixel factor SL of water boundary slope, slope factor, slope length, slope length factor and concave point problem and reflux technology processing were developed. The results indicated that, in Shangnan County, the slope area located on the 15° to 25° degrees was 530.51 km2, accounting for 22.93% of the total area. The slope area on the 25° to 45° degrees was 1 083.32 km2, accounting for 46.82% of the total area. The slope area on the 15° to 45° degrees accounted for 70% of the total area. This area was the main cause driving the serious soil erosion in Shangnan County, this results of this study were consistent with the actual status of the study area. This research extended the application of the QRSM to the upper reaches of the Yangtze River, being meaningful for further monitoring and forecasting of soil erosion across the whole of the Yangtze River Basin. Our study is also valuable for soil erosion monitoring in other small catchments, both theoretically and practically.

Abstract:In order to obtain optimal areal rainfall calculating method of watershed in Loess Plateau, methods of Arithmetic mean (Am), Thiessen (Tsn), Ordinary Kriging (OK), Universal Kriging (UK), Simple Kriging (SK), Simple Kriging with elevation auxiliary (SK_EL), Simple Kriging with elevation and spatial coordinate of rain gauge auxiliary (SK_EXY), as well as Topography Regression (Tr), were employed to estimate areal rainfall of Huanjiang watershed in Loess Plateau from 2006 to 2011. Efficiencies of 9 methods were tested. Results showed that: (1) Areal precipitation from Am method was a value each year without spatial information. Tsn method generated patchy distribution, and IDW resulted in discontinuous trend around the site. Areal precipitation from the other 6 kriging based methods showed similar spatial pattern. All of them were equivalent band decreasing from the southeast to the northwest. Interpolation surface from OK was the smoothest and results from TR and SK expressed the changing trend of precipitation along terrain. (2) Both single-year and multi-year cross-validation based on the 24 rain gauges revealed that Tr and SK_EXY had the higher and SK had the lowest interpolation accuracy. (3) It is suggested that the combination of Am and Tsn method had the advantage when spatial distribution was not necessary, and the value of precipitation were close to the mean value of all methods, but Tr and SK_EXY had obvious advantage when both distribution and value of precipitation were necessary.

Abstract:The aims of this study were to investigate the ecological stoichiometry characteristics during the process of wetland degradation, and clarify the relationship between the changes in C and N sink function of the soil and the balance in soil C, N and P. Soil C, N and P concentrations, storages and ecological stoichiometry in three kinds of wetland landscape with different degrees of degradation, i.e. swamp (SW), swamp meadow (SM) and meadow (ME) in the Zoige Wetland Nature Reserve, were studied by means of field investigation, laboratory analysis, and mathematical statistics. Compared with SW soil, total organic C and N concentrations in the whole soil profile decreased by 29.55% and 6.52% in SM soil, and by 67.53% and 40.04% in ME soil; storages of C and N decreased by 67.49% and 60.10% in SM soil, and by 85.14% and 54.47% in ME soil, respectively. Total P concentration in the soil followed the order of SM＞ME＞SW, and P storage in the soil followed the order of ME＞SW＞SM. Both total organic C and N concentrations in the soil of SW increased obviously with increasing soil depth, while the concentrations of total organic C, N and P in the SM and ME soil decreased with increasing soil depth. For all three types of soil, C, N and P storages in the 40-100 cm layers were generally higher than those in the 0—40 cm layers. For the soil in the SW, SM and ME, C/N was 40.38, 31.70 and 23.26, while C/P was 409.52, 247.46 and 113.07, and N/P was 10.43, 7.90 and 5.02, respectively, with C/N, C/P and N/P declining as the wetland degradation became intensified. When C/P is high and N/P is ＜14, both N and P are limiting factors for plant growth, and N is more limiting than P. In conclusion, degradation of the Zoige Wetland has led to decreased concentrations and storages of C and N in the soil, and the C and N sink function of the soil, in particular the C sink function, has been weakened during the wetland degradation process.

Abstract:In this study, the effects of attapulgite (ATP) on soil water movement and hydrodynamic parameters were investigated by adding different rates, i.e. 0, 10, 20, 30, 40, 50, and 60 g/kg, of ATP into the soil uniformly. The results indicated that soil infiltration rate was reduced and cumulative infiltration decreased with increasing ATP content. When the ATP content was increased, residual water content (θr) decreased, and saturated water content (θs) increased, the reciprocal value of air intake (α) increased, and the form factor (n) decreased. At the same time, soil water holding capacity increased with increasing ATP content. When unsaturated soil hydraulic conductivity, diffusivity and unsaturated soil water retention capacity were calculated according to the relevant parameters of the van Genuchten formula, unsaturated soil hydraulic conductivity, diffusivity and capacity of water all decreased with increasing ATP content. By fitting the unsaturated soil water diffusivity using the empirical formula, relatively high relevance was observed. In summary, adding ATP to the soil has some penetration-retarding effects, it can improve soil water holding capacity and reduce soil macropores, and can improve soil quality to some degree.

Abstract:3 adjacent typical collapse mounds (Ⅰ, Ⅱ and Ⅲ) were selected in Huangniken collapse mound group in Zhuotian Town, Changting County of southwestern Fujian Province, in which vegetation coverage of each collapse mound was 2%, 20% and 95%, respectively; seven plots including upper catchment, collapsing wall (top, middle and bottom part), colluvial deposit (upper and lower part) and channel outlet for each collapse mound were sampled, and the main physical and chemical properties including particle composition, bulk density, water content, pH value, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP) and total potassium (TK) in 3 depths (0—10 cm, 10—20 cm and 20—30 cm) of each plot were measured. Meanwhile, spatial variation of the contents of SOC, TN, TP, TK and their stoichiometric characteristics in each collapse mound with different depth and position were analyzed in this paper. The results indicated that with improvement of vegetation coverage (fromⅠto Ⅲ), the contents of SOC, TN, TP, TK and their stoichiometric ratios increased significantly with the exception of TP content and P/K, and the order of increasing range of soil nutrients was SOC＞TN＞TK＞TP, while that of soil stoichiometric ratios was C/P＞C/K＞C/N＞N/K＞N/P＞P/K. Under different depth (from 0—10 cm to 20—30 cm), the contents of SOC, TN, TK and the ratios of C/N, C/P, C/K and N/P generally decreased, while the content of TP and the ratios of N/K and P/K basically remained stable. Variation of soil nutrient contents and their stoichiometric ratios for different position were greatly obvious in each collapsing hill: the contents of SOC, TN, TK, C/N and C/P, C/K, N/P and N/K showed a down-up-down variation tendency along the runoff routes from upper catchment to channel outlet via collapsing wall and colluvial deposit, while TP content and P/K ratio kept relatively consistent. Besides, soil stoichiometry was closely related to nutrient content, silt content, bulk density, water content and pH value by stepwise regression analysis. In summary, the contents of C, N and P were at very low level, especially P content in the severely eroded context of collapse mound.

Abstract:In order to promote application of the new type fertilizers, increase crop yield and reduce environmental pollution, the research explored effects of humic acid nitrogen fertilizer on corn and wheat yield, nitrogen absorption and utilization, and nitrogen distribution and loss in soil. The results showed that application of activated humic acid fertilizer and conventional mixed humic acid fertilizers could significantly promote corn and wheat yield, increase nitrogen utilization ratio, increase nitrogen residual content, reduce nitrogen loss amount, increase nitrogen surplus and net nitrogen mineralization, and promote soil nitrogen absorption. Activated humic acid fertilizer was better than conventional humic acid fertilizer. The results showed that compared with common urea, the activated humic acid fertilizer and conventional mixed humic acid fertilizers showed these effects: Corn yield were increased by 20.6% and 9.8%, respectively, and wheat yield were increased by 50.5% and 19.2%, respectively; In corn growing season, the nitrogen utilization rates were increased by 5.8% and 3.4%, respectively, while in wheat growing season, the nitrogen utilization rates were increased by 22.7% and 8.6%, respectively; In corn growing season, the nitrogen loss rates were reduced by18.3% and 10.9%, respectively, while in wheat growing season, the nitrogen loss rates were reduced by 20.2% and 6.3%, respectively; In corn growing season, the soil nitrogen residual rates were increased by 12.5% and 7.5%, respectively, while in corn growing season, the soil nitrogen residual rates were reduced by 2.7% and 2.2%, respectively. Application of humic acid fertilizer can improve the distribution of nitrogen in the soil, which therefore can be better satisfy crop root fertilizer characteristics.

Abstract:In order to explore the optimum fertilization model for reducing the loss of phosphorus in farmland and improve the utilization ratio of phosphate fertilizer in the Yangtze River Basin, as well as reduce the threat to the water quality of the Yangtze River, a long-term field experiment and laboratory analysis were carried out to study the effect of phosphate fertilizer and phosphorus element transportation on chemical fertilizer application combined with pig manure and rice straw in purple soil. The results showed that the application of reduced chemical fertilizers combined with organic fertilizer did not significantly affect crop yield, and to some extent it could reduce agricultural phosphorus loss and improve phosphorus utilization. The utilization rate of phosphate fertilizer by rice showed that pig manure+20% reduced conventional phosphorus fertilizer (MDP)＞straw+20% reduced conventional phosphorus fertilizer (SDP)＞pig manure+conventional phosphorus fertilizer (MP)＞straw+conventional phosphorus fertilizer (SP)≈optimal fertilizer (P), with the utilization rate of phosphate fertilizer between 20% to 25% in all treatments. The utilization rate of phosphate fertilizer of rape listed in the order of SDP＞MDP＞MP＞SP＞P, with the utilization rate of phosphate fertilizer between 17% to 29%. In the first month of rice growth period, total phosphorus content in field surface water increased with the increase of the levels of phosphorus fertilizer, and that in the conventional fertilization (P) treatment was 4 times higher than that in no P fertilizer (P0). The phosphorus content listed in the order of P＞MP＞SP＞MDP＞SDP＞P0. Combined application of organic manure in paddy soil could improve the phosphorus fixation and reduce early phosphorus release to the water, and straw showed better effect than pig manure. The critical period of field control of phosphorus loss was 7 to 10 days after adding P fertilizer into the field. The available P content was much lower in bud stage of rape than in seedling stage, but it increase significantly in flowering stage and the later stage of rape. It was the main period of soil phosphorus leaching after flowering period of rape. The application of organic and inorganic fertilizer could significantly increase the content of available phosphorus in soil, and chemical phosphate fertilizer reduction and combined application of organic fertilizer is a good measure to deal with “control source and curb loss” of agricultural non-point source pollution.

Abstract:In order to study the variation of phosphorus forms, sorption capacity and the potential releasing risks, the phosphorus forms and sorption index were analyzed in the barren wetland and Spartina alterniflora invasion wetland of Min River estuary. The results indicated that inorganic phosphorus (IP) was the main form of soil phosphorus, which accounted for 61.40% and 61.01% of total phosphorus (TP) in soils of the barren wetland and Spartina alterniflora invasion wetland, respectively. The concentrations of TP, IP, iron and aluminum-bound phosphorus (Fe/A1-P) and calcium-bound phosphorus (Ca-P) were all significantly higher than those of the barren wetland, and the increase percentage were 12.58%, 9.49%, 11.11% and 5.32% in turn, while the organic phosphorus (Org P) had no significant change. Furthermore, Spartina alterniflora invasion had different impacts on the amorphous phosphorus (Pox), iron (Feox), aluminum (Alox), the phosphorus adsorption index (PSI) and the degree of phosphorus saturation (DPS), and the Feox and DPS were not significantly changed. However, the Pox and PSI were increased significantly, while the Alox was significantly decreased. The potential releasing risk (ERI) of the barren wetland was 12.69, which was belonged to middle risk, nevertheless, the ERI of the Spartina alterniflora invasion wetland was reduced to 9.98, which was belonged to low risk, indicating that Spartina alterniflora invasion could lower the releasing risk of soil phosphorus in wetland.

Abstract:Taking the soils under three different reclamation modes, i.e. reclamation filled by Yellow River sediments, reclamation filled by lake sediments, and beforehand reclamation, in the Jining region as the research objects, spatial distribution characteristics of various forms of inorganic phosphorus (Ca2-P, Ca8-P, Al-P, Fe-P, O-P, Ca10-P) in soils under different reclamation modes were studied, and the reasons for low phosphorus availability in reclaimed soils were investigated. The result shows that: (1) Total phosphorus content in reclaimed soils under different reclamation modes was between 0.42 to 0.77 g/kg, and available phosphorus content was between 0.65 to 5.22 mg/kg, total phosphorus content was higher in reclaimed soils, but plant-available phosphorus content was lower. (2) In reclaimed soils, contents of sparsely plant-available inorganic phosphorus (Ca10-P and O-P) were the highest, and the contents of Ca8-P and Ca2-P, which are plant-available, were the lowest. For the contents of various forms of inorganic phosphorus, there were slight differences among different reclamation modes. Compared with normal soils, the proportion of Ca8-P in reclaimed soils decreased, accounting for about 3% of total phosphorus, but the proportion of sparsely plant-available O-P increased, accounting for about 32% phosphorus. (3) Total inorganic phosphorus and various forms of inorganic phosphorus accumulated in surface soils, phosphorus content and availability decreased with increasing soil depth, with the content and availability in soils under the modes of reclamation filled by Yellow River sediments and reclamation filled by lake sediments being higher than that in soils under the mode of beforehand reclamation.(4) There was a significant negative correlation between plant-available phosphorus and soil compactness, r=-0.554*(p＜0.05), and there was an extremely significant positive correlation between plant-available phosphorus and Ca10-P, r=0.650**(p＜0.01). In reclaimed soils, a greater compactness and a lack of effective source of phosphorus could account for the lower phosphorus availability. In comparison, phosphorus conditions in soils under the mode of beforehand reclamation were worse because this mode got greater mechanical compaction.

Abstract:To find out the effect of different alkaline conditions on inorganic phosphorus components of soda saline soil, this research selected the soda meadow alkaline soil in western Jilin province as the research object, and used the method of indoor simulation experiment combined with indoor analysis to study the dynamic changes of the components of inorganic phosphorus content in soil of different forms under different alkaline conditions. The results showed that reducing alkali soil pH value within a certain range was helpful to increase the contents of Ca2-P, Fe-P, Al-P, and Ca8-P, which increased by 44.8%, 4.1%, 45.9%, and 42.0% in pH 8.3 treatment compare with those in the pH 9.2 treatment, and increased by 44.8%, 4.1%, 45.9%, and 42.0% compare with those in the pH 10.2 treatment; the effect of pH on O-P content was relatively small, and pH change in short term would not affect its content; Ca10-P content in soil increased with the increasing soil pH value, which increased by 15.6% and 51.4% respectively in the pH 10.2 treatment compare with those in pH 9.2 and pH 8.3 treatments. The research showed that different alkaline conditions could affect the conversion between the different inorganic phosphorus, and the decrease of soil pH value was good at the increase of the content of valuable phosphorus, but led to the decrease of the content of potential phosphorus in soil.

Abstract:In order to understand the distribution characteristics of soil aggregate nutrients under different vegetation restoration time, we selected typical eroded red soil sample plots with different restoration time (0 year, 5 years, 10 years, 15 years, 30 years and 80 years), which located in Hetian Town, Changting County, Fujian Province of subtropical China in this paper. Nutrient contents of different soil aggregate sizes (＞5 mm, 2—5 mm, 1—2 mm, 0.5—1 mm, 0.25—0.5 mm and ＜0.25 mm) with different depths of soil layers (0—20 cm and 20—40 cm) of sample plots were measured, and the correlation of nutrient contents between soil and aggregates were analyzed as well. The results are as follow: (1) The contents of organic carbon, total nitrogen, total phosphorus, total potassium, available phosphorus and available potassium within soil aggregates were 2.06 to 27.71 g/kg, 0.54 to 2.12 g/kg, 0.034 to 0.171 g/kg, 2.20 to 6.89 g/kg, 0.31 to 3.30 mg/kg and 7.35 to 85.71g/kg, respectively, with the process of vegetation restoration; (2) the contents of organic carbon, total nitrogen, total phosphorus and available phosphorus generally increased with the decreasing aggregate-size fraction (P＜0.05), but the contents of total potassium and available potassium had no significant difference (P＞0.05); (3) during different aggregate size fractions, the contents of organic carbon, total nitrogen, total phosphorus and available phosphorus within soil aggregate generally increased with the years of vegetation restoration (P＜0.05), while the content of total potassium firstly increased and decreased finally, and the content of available potassium showed a fluctuant increase tendency; (4) at the early period of vegetation restoration (0 and 5 years), the nutrient contents of soil aggregate of 2 layers kept relatively consistent tendency, and soil aggregate nutrient contents in 0—20 cm soil layer were significantly higher than in 0—20 cm layer; (5) the decreasing order of contribute rate of different aggregate fractions to soil nutrient was (＞5 mm)＞(2—5 mm)＞(0.5—1 mm)＞(1—2 mm)＞(0.25—0.5 mm)＞(＜0.25 mm), and the contribute rate of ＞2 mm aggregates were 34.18% to 49.93%; soil nutrient contents were highly related to the ＞0.25 mm aggregates ((P＜0.01). In summary, soil aggregate nutrient content increases obviously associated with the improvement of soil structure and the promotion of nutrient sequestration, while soil erosion were controlled by the measure of vegetation restoration.

Abstract:Through selecting the soil from tea garden in Mengshan as the research object, effect of citric acid on adsorption-desorption of Cu2+ by soil micro-aggregates was investigated using the methods of equilibrium liquid adsorption and the NaNO3 solution as desorption. The results showed that: the adsorption of Cu2+ by raw soil and different sizes fractions of the micro-aggregates increased, with the concentration of Cu2+ increased. Influenced by free ferric oxide, cation exchange capacity and organic matter, the adsorption capacity of Cu2+ was diminishing as the following sequence: (＜0.002 mm)＞（0.053—0.002）mm＞raw soil＞（2—0.25）mm＞（0.25—0.053）mm; The low concentration of citric acid (0 to 1 mmol/L) was beneficial to the adsorption of Cu2+, while the high concentration of citric acid (＞1 mmol/L） inhibited the adsorption. Adsorption capacity reached the maximum when the concentration of citric acid was 0.5 mmol/L. Easy desorption rate increased with the concentration of Cu2+ increased, and the order of desorption was opposite to adsorption. The increase in concentration of citric acid would increase the desorption of Cu2+. The fitting of 3 equations (Langmuir, Freundlich, and Temkin) to the isothermal adsorption process reached a significant level (p＜0.01), and the fitting effect of Langmuir equation was the best. The adsorption of Cu2+ on the soil micro-aggregates after adding citric acid was mainly absorbed by single layer.

Abstract:To ensure the continual growth of mulberry at inferior sites in the area of the Three Gorges Reservoir, an analysis of soil structure stability and water-retention properties was conducted in 4 habitats defined as having stony, skeleton, gravelly and disturbed soils in this paper. Furthermore, the various soil factors acting as obstacles and the ways to improve habitats were discussed. The results showed that: (1) Significant differences (p＜0.05) were found in soil physical properties at the different habitats, and the order of soil bulk density was skeleton soil (1.30 g/cm3)＞stony soil (1.23 g/cm3)＞gravelly soil (1.12 g/cm3)＞disturbed soil (1.08 g/cm3); The sand grain content was in the same order; (2) Resistance to seasonal drought was greatly different among these habitats, and soil total storage capacity was in the order of stony soil (97.185 mm)＞gravelly soil (81.139 mm)＞disturbed soil (66.958 mm)＞skeleton soil (47.353 mm). Moreover, the maximum available capacity was stony soil (54.140 mm)＞gravelly soil (47.552 mm)＞skeleton soil (36.399 mm)＞disturbed soil (11.705 mm); (3) The soil anti-erodibility index (ASI) for different habitats was in the order of skeleton soil (4.57)＞stony soil (2.44)＞gravelly soil (2.36)＞disturbed soil (2.31). Correlation analysis indicated that soil stability was significantly or highly significantly positively correlated with sand content, was highly significantly negatively correlated with powder and clay content, and was not significantly correlated with soil porosity; (4) The soil factors considered as obstacles for mulberry were different in different habitats; soil amendments could be used to increase the soil permeability in gravelly soil habitats, water-retaining agents could be added to improve the soil available capacity in disturbed soil habitats, and nitrogen-fixing plants and green manure could be planted/added to increase soil nutrients in stony and gravelly soil habitats.

Abstract:This experiment aims at researching the change regulation of soil stability under the condition of dry-wet cycles of all layers of soil in collapsing gully erosion area where granite develops. By conducting the experiment of dry-wet cycles for typical development of all layers of the soil (eluvial horizon, illuvial horizon, cambic horizon and parent material horizon) of granite slope in collapsing gully erosion area in Tongcheng, Hubei province, we analyzed the influence of the times of dry-wet alternations on the development of soil cracks, the disintegration characteristics of soil and the shear strength of soil of all soil layers. The results showed that: under the influence of dry-wet cycles, the soil developed cracks gradually; after the second cycle, main cracks arised, and the crack ratio increased significantly; after that, cycles developed small cracks. After 4 times of dry-wet alternations, the size of the crack ratio of the 4 layers of soil listed as illuvial horizon＞eluvial horizon＞cambic horizon＞parent material horizon. With the increasing times of dry-wet cycles, soil cracks developed, soil disintegration characteristics of all layers of soil increased constantly, and the disintegration of eluvial horizon and illuvial horizon was slow, while cambic horizon and parent material horizon could completely collapse in a very short time; With the increasing times of dry-wet cycles, the shear strength of soil attenuated constantly, and the amplitude attenuation of eluvial horizon and illuvial horizon decreased, while the amplitude attenuation of cambic horizon and parent material horizon increased.

Abstract:Through filed sampling and laboratory analysis, the composition and fractal features of profile soil micro-aggregates in purple hilly area with different land use types were studied. The results showed as follows: Among woodland, pepper filed, dry land, paddy and citrus orchard, micro-aggregates of 0.25～0.05 mm was dominant, followed by micro-aggregates of 0.05 to 0.01 mm, which appropriated 18.80% to 35.57% of the total samples, the least were ＜0.001 mm, which proportion was between 0.33% and 2.57%. In 0—20 cm soil layer, the annual mean weight soil surface area (MWSSA) sequence was woodland (161.04 cm2/g)＞citrus orchard (134.49 cm2/g)＞pepper land (117.31 cm2/g)＞paddy (100.67 cm2/g)＞dry land (96.94 cm2/g). In this layer, the MWSSA of woodland micro-aggregates was significantly higher than other land use types,which aggregate state and aggregate degree superior than others as its aggregate state showed a 16.55%, 20.15%, 11.23% and 7.68% higher than pepper filed, upland, paddy and citrus orchard, respectively. In 20—40 cm soil layer, the fractal features D of each land use type is like citrus orchard (2.41)＞woodland (2.40)＞pepper field (2.32)＞paddy (2.31)＞upland (2.12), the D value of upland is significantly lower than other lands. The fractal features of these five land correlate with the result of factor analysis, though some inconsistent exist. Hence, the fractal features of micro-aggregates in different land use type can be, to some extent, seen as an index to characterize superior or inferior of soil physical properties, fertility level and corrosion resistance.

Abstract:In order to reveal the role of human activities on soil quality, 5 land use patterns were examined, including paddy field, dry land, citrus orchard, artificial forest and natural forest. Each land use pattern was evaluated for its effectiveness at retaining soil aggregate stability and its fractal features in Danjiangkou Reservoir area, in China. The rate of ＞0.25 mm macro-aggregates (R＞0.25), the percentage of aggregate destruction (PAD), the mean weight diameter (MWD), and the geometric mean diameter (GMD ) were tested in this study, and the fractal dimension (D) were also compared. Results showed that the wet sieving method was accurate, reliable and reproducible, and the results based on this method could better reflect the composition and stability of soil aggregate compare to those based on dry sieving method. To some degree, each of aggregate stability indexes could reflect the variation of soil aggregates under different land use patterns. The forests (natural forest and artificial forest) had better soil stability and erosion resistance, with relatively high values of MWD and GMD and relatively low D. However, dry farmland (dry land, and citrus orchard) showed an opposite trend. Its soil stability was weak, the MWD and GMD were relatively low and the D was relatively high. The correlation analysis indicated that aggregate content of each size had significant linear relationship to the indexes of MWD, GMD, and D. And in the transformation of soil aggregate from micro-aggregates (＜0.25 mm) to medium aggregates (0.25—5 mm), and to large aggregates (＞5 mm), 0.25 mm, 1 mm and 5 mm particle size were more critical points.

Abstract:It is critically important to study the impacts of chemical and organic fertilizers on soil organic carbon (SOC), because regional carbon sequestration is influenced under long-term farming conditions. We chosed four treatments, i.e. no fertilizer (CK), conventional chemical fertilization (CF), low rate EM compost (EML) and high effective microorganisms compost (EMH) from the long-term experiment (19 a) located in Quzhou County, Hebei Province. Soil samples were taken and separated into different fractions using physical, density and particle size methods for the 0—10, 10—20, 20—60 and 60—100 cm soil layers, and the SOC contents of the whole soil and soil fractions were analyzed. The results indicated that in the 0—10 cm layer, compared with the CK, CF, EML, and EMH all significantly increased SOC content of the whole soil and all fractions by 33% to 63%. In the soil layers deeper than 10 cm, only EML and EMH treatments significantly increased SOC content of the whole soil and all fractions (by 20% to 67%). For the 0–100 cm soil layer, compared with the CK, the SOC stock increasing rate in EMH treatment (1.17 t C /(hm2·a)) was 11.7 folds of that in CF treatment. In the 0—10 cm layer, SOC saturation of the ＜20 μm mineral fraction for CF, EML and EMH treatments (65% to 82%) was significantly higher than that of the CK (64%). In the soil layer deeper than 10 cm, there was no significant difference in SOC saturation among the CK, CF and EML treatment, but EMH treatment had a significantly higher SOC saturation than the other three treatments. We concluded that under long-term fertilization conditions, SOC in soil layers depper than 10 cm should be given more consideration than before. For the North China Plain where has a low level of SOC, there is still much space to improve soil carbon level, and organic fertilizer is one of the most effective farming practices.

Abstract:A 30-year experiment was altered, and aggregate-associated organic carbon fractions based on density fractionation scheme and its δ13C value were measured to study the changes of following-up fertilization reforming on their content and distribution after 3-year fertilization alteration under 7 fertilization treatments, inculding high organic material (HOM), normal organic material (NOM), chemical fertilizer (CF), normal organic fertilization treatment changed from chemical fertilization treatment (C-N), chemical fertilization treatment changed from original normal organic fertilization treatment(N-C), chemical fertilization treatment changed from original high organic fertilization treatment (H-C), and high organic fertilization treatment changed from original normal organic fertilization treatment (N-H), which were analyzed to provide scientific basis for controls of soil fertility and organic carbon management. The results showed that compared with 30-year application of chemical fertilizer,, long term application of organic fertilizer significantly increased the content of total aggregate-associated organic carbon, coarse free particulate organic carbon (cfPOC), fine free particulate organic carbon (ffPOC), occluded particulate organic carbon (oPOC) and mineral-associated organic carbon (MmMOC). The fPOC with the highest magnitude of increase by 67.5% to 150% indicated that it was more sensitive to the fertilizations than other organic carbon fractions. After 3-year following-up fertilization alteration, total aggregate-associated organic carbon, cfPOC, ffPOC, oPOC and MmMOC were improved by 5.2% to 15.5%, 2.8% to 40.2%, 18.9% to 43.9%, 2.8% to 17.6% and 5.1% to 8.2% under the treatment of increasing input of organic fertilizer (C-N and N-H), respectively, while those under the reducing input of organic fertilizer treatments (H-C and N-C) were reduced by 15.8% to 20.9%, 12.6% to 26.9%, 24.6% to 48.4%, 19.9% to 23.9% and 4.9% to 21.9%. The MmMOC, accounting for 50.4% to 59% of total aggregate-associated organic carbon, was the main form for organic carbon sequestration in red paddy soil under all fertilization, while oPOC accounted for 11.3% to 13.4%. The application of fresh organic carbon resulted in the higher content new soil organic carbon content of macroaggregates and all aggregate-associated organic carbon fractions. About 45.6% to 50.1% of fresh organic carbon was transferred to MmMOC, 34.1% to 42.3% to fPOC and 11.8% to 18% to oPOC. As a conclusion, the following-up organic fertilization is necessary to maintain or improve red paddy soil aggregate-associated organic carbon fractions in the southern China.

Abstract:In this study, we studied the spatial distribution of soil salinity in a degraded wetland of Xiaopo Lake based on the combined method of electromagnetic induction (EMI) with semi-variation function in the Geo-statistical methods and the Kriging of the spatial interpolation. Significant correlation between the apparent electrical conductivity and soil salinity content indicated that apparent electrical conductivity could be used to characterize the variation of soil salinity in the degraded wetland. The results of semi-variation function showed that there was a strong spatial autocorrelation (C/(C0+C)＞0.5) for the spatial distribution of soil salinity, which meant that the distribution of salinity was mainly caused by the structural factors. By interpolating soil salinity with Kriging method, we found that the spatial distribution of soil salinity was obviously consistent with the spatial pattern of the degraded wetland, and the areas with high soil salt content were the areas where the grazing activity was strong. Soil salt content of the degraded wetland was higher than that of the non-degraded wetland, so the content of the soil salt could reflect the degree of degradation of the degraded wetland to some extent, which can offer an effective basis for the prevention and control of the wetland degradation.

Abstract:Salinity characteristics of shell sand and adjacent ordinary saline soil was investigated in the shell ridge island of the Yellow River Delta. Spatial variability of salinity in the shell ridge was analyzed. Salinity characteristics of the profiles of two types of soil (shell sand and saline soil) with different groundwater depth were measured, the influence of soil types and groundwater depth on soil salinity was analyzed, and soil salinity characteristics was comprehensively evaluated by performing principal component analysis. The result showed that: (1) All salinity indexes, except Ca2+, showed a gradual increasing trend from surface to lower layer in the shell sand profile (0—120 cm), but Ca2+ showed a gentle decreasing trend in the profile. (2) Content of salt ions had close relationship with groundwater depth in the shell sand profile (0—120 cm), with the fine particle content, water content, salt content, pH value in the seaward profile (groundwater depth 1.5 m) being higher than that of the chenier ridge profile (groundwater depth 2.5 m); content of salt ions showed different trends in the two types of profiles, i.e. K+?Na+?Cl-、SO42- content of each layer (every 10 cm as a layer) in the seaward profile was obvious higher than the content of the same layer in the chenier ridge profile, but Ca2+?Mg2+ content of each layer was similar in the two profiles. (3) Correlation analysis of soil salinity indexes showed that, all indexes, except Ca2+, had significant positive correlations between each other. (4) Results of the principal component analysis showed that the cumulative contribution rate of the first four principal components reached 84.265%, which represented the saline condition, soil Ca2+ content, soil salt content and alkalization characteristic, and K+ content sequentially. Principal component analysis based on the salinity characteristic indexes could well classify and sort soil samples in the shell ridge island.

Abstract:Based on fractal theory, field sampling and laboratory analysis, the fractal dimension of soil waste-grassland after renovation was studied in Hanzhong, correlation of fractal dimension with soil textural, grain diameters and nutrient content were also discussed, and the prediction model of soil fractal dimension after waste-grassland renovation was built. The results showed that as follow: (1) The fractal dimension of plough soil particles was between 2.55～2.95, the mean value and standard deviation was respectively 2.77 and 0.134.The relationship of fractal dimension of soil particles was significant with soil texture (R2=0.978 0), characterized by the fine soil texture was, the bigger the fractal dimension was. (2) The fractal dimension of soil particles was mainly decided by the clay content, the between has significant positive correlation; the forecast model built using the fractal dimension and soil clay (≤0.002 mm) was high precision (R2=0.982 7), it can better predict fractal dimension of soil particles. (3) The positive correlation relationship existed between soil fractal dimension and total nitrogen, effective phosphorus and available potassium (correlation coefficients: 0.914, 0.580 and 0.513 respectively) respectively. Fractal dimension of soil particles can be used as the effective indicators of soil fertility conditions. Studies concluding that soil fractal dimension can be a good characterization of soil texture , particle size composition and nutrient status, it will provide certain reference for the determination of nutrient content and sustainable use of land resources after land renovation.

Abstract:The study area was Shuimo River, a typical urban river in the arid area in Urumqi. Heavy metal contents and distribution characteristics in the riparian soils of the Shuimo River were studied, and heavy metal pollution was evaluated, by combining classical statistics and geo-statistics correlation method. The results showed that the contents of heavy metals differed slightly at different soil depths. From the aspect of land use mode, human activities significantly interfered with the change of heavy metal content in the riparian soils, the correlations between heavy metals reflect the homology and diversity of several heavy metals to some degree. The results of principal component analysis indicated that Cu and Zn were the characteristic heavy metals which were controlled by multiple factors. From the aspect of spatial distribution, the peak value points of the distribution of heavy metals in the surface soil was similar, being mainly at the southern tip of the river. Single factor pollution indices of heavy metals in the riparian soils at different depths were all less than one, indicating that the soil was not polluted. Nemerow integrated pollution index in the riparian soils at different depth was 1.26 (0—20 cm),1.20 (20—40 cm) and 1.32 (40—60 cm), respectively, all with 1.0＜P≤2.0 and at level Ⅲ, indicating slight pollution. The carrying capacity for different heavy metals in different soil layers was relatively high, belonging to the moderate capacity region. In general, the environmental quality in regard of heavy metals in the riparian soils of Shuimo River was in a good condition. In summary, Cu and Zn are the main heavy metals causing pollution, and heavy metal pollution is affected by human activities such as factory distribution, river diversion and reservoir construction. In short, there is yet no pollution or light pollution in the riparian soils of Shuimo River currently, the environmental quality is good.

Abstract:A total of 1 242 soil samples were collected from the main tobacco-growing areas in Xiangxi in 2015, and their soil pH were determined to study the areal distribution and spatial distribution of tobacco-growing soil pH and its influencing factors in order to understand the characteristics of tobacco-growing soil pH . The results were as follows:(1) pH of tobacco-growing soil in Xiangxi was generally suitable for tobacco cultivation with a mean of 6.12, amplitude of 4.17 to 8.17 and variation coefficient of 18.30%. About 34.06% of the soil samples had pH between 5.5 to 7.0, which was suitable for high quality tobacco cultivation. About 20.77% of the soil samples had pH less than 5.0, and 18.20% of the soil samples had pH greater than 7.5. (2) The means of tobacco-growing soil pH in 7 main tobacco-growing counties were between 5.44 to 6.84. There were extremely significant differences among different counties for the tobacco-growing soil pH. (3) IDW interpolation map indicated that the spatial distributions of tobacco-growing soil pH were reduced from the west to the east. (4) The tobacco-growing soil pH was affected significantly by soil forming rock, soil type, soil erosion condition, irrigation capacity, altitude, topsoil depth, organic matter content and soil mechanical composition. (5) The topsoil acidification was easy to occur in the tobacco-planting field of serious erosion, non-irrigation capacity and shallow topsoil, in the soil development by purple gritstone, in red soil and red-yellow soil, and in the soil of high clay particle content. (6) The tobacco-growing soil pH increased with the rise of soil organic matter content and the decrease of altitude.

Abstract:Shixia Basin is located at north of Miyun Reservoir, it is the first level nature reserve as well as an important water source of Beijing area, but suffering from serious soil erosion and debris flow. Slope engineering measures may decrease soil loss of the slope, accumulate aggregates, and increase slope stability. Terrace and horizontal bar are two kinds of engineering measures well adopted in Beijing area. To investigate the effects of engineering measures on slop stability, and understand the effects of soil physical properties (soil bulk density, soil moisture, total porosity, capillary porosity, non-capillary porosity, firmness and liquid limit) on soil shear strength, the changes of soil shear force with depth under different engineering measures, soil shear characteristics and the affecting factors were studied. The results showed that soil critical shear force increased with soil depth. The relationship between soil shear strength calculated by Coulomb formula and soil critical shear force measured in situ fitted with the equation: σ=0.0123τf+0.6308. Cohesion and angle of internal friction on and down the channel of irrigation differed slightly, but shear strength differed significantly. The effects of soil physical characteristics varied, among which soil compaction, volume-weight and moisture content had the most significant effects. The anti-shear ability ranked as follows: terrace＞horizontal bars＞bare land, and the anti-shear ability of the horizontal bars with conifer was better than the one with deciduous trees. In the area of Miyun, Beijing, when carrying out engineering measures, it is important to increase the width of terrace, and establish mingled forest of conifers and deciduous trees.

Abstract:Soil samples under different land uses, including woodland, cultivated dryland and orchard, were collected from profile horizons which derived from main parent materials (including basalt, sand-shale, Quaternary red soil and granite) in Guangdong Province, soil physico-chemical properties such as soil particle-size composition, organic matter, CEC, etc. were determined. The fractal dimension of particle-size distribution (PSD) for soils derived from different parent materials and its relationship with soil properties were studied. The results indicated that, the range of fractal dimension of PSD for soils derived from basalt, Quaternary red soil, granite and sand-shale were 2.923 9 to 2.981 2, 2.858 8 to 2.937 7, 2.769 3 to 2.923 1, and 2.544 6 to 2.885 6, respectively. The fractal dimension of PSD for soils derived from basalt, Quaternary red soil and sand-shale were significantly different. The fractal dimension of soil PSD showed an increasing trend with increasing soil depth, and the fractal dimension of soil PSD was almost the same in deep horizons of soils derived from the same parent material. The fractal dimension of soil PSD had smaller variation between soil at different depth in soil profiles derived from basalt and Quaternary red soil, however, the variation was larger for soils derived from sand-shale and granite. The fractal dimension of soil PSD was significantly negatively correlated with sand content, but was significantly positively correlated with clay content, soil total P, available K, total Fe, CEC, soil organic matter, total N, available N. The fractal dimension of soil PSD could be applied as a quantitative index reflecting soil fertility.

Abstract:In order to find out the impact of the construction of photovoltaic power plants on vegetation and soil in alpine desert steppe, this study selected the Beixiang photovoltaic industry park of Tara Beach in Gonghe Basin as the research object, and conducted consecutive monitoring plots in August of 2013—2015. By choosing 3 typical plots of 10 m×10 m within fenced area, PV+fenced area and natural growth zone, and through using quadrats, this study surveyed vegetation structure characteristics and analyzed soil properties in laboratory. Finally, different indicators that evaluated the effects of photovoltaic plant were combined. The results showed that: Fenced and photovoltaic plants had a significant impacts on the vegetation and soils. Compared with the data surveyed in 2013, the photovoltaic fenced area data of plant species numbers, vegetation coverage, aboveground biomass, richness index, soils water content, organic matter content and nitrogen content respectively increased by 116.7%, 83.9%, 68.7%, 119.2%, 88.6%, 83% and 81.8% in 2015, which showed significant change tendency (P＜0.05). Voltaic panels improved environmental factors of plant growth in alpine desert steppe, especially increased soil water content, which can protect fragile ecosystems and showed sand-fixing effect, promoting the succession development of desert grassland.

Abstract:Using remote sensing data, we estimated sandland vegetation coverage (VC) during the growing season from 2000 to 2014 in the Otindag Sandland, and analyzed the spatial-temporal characteristics of VC. Impacts of climatic factors and land use/cover change on the sandland VC were primarily distinguished by statistical analysis. The results showed that the sandland VC was increased with fluctuations during the growing season in the Otindag Sandland from 2000 to 2014, the average annual VC was 0.423 in the study area with an average increase rate of 0.003 6/yr. For the spatial pattern, the VC in the northern, central and southern fringe regions of the study area showed an increasing trend, but no obvious trend was observed in the eastern and part of the western regions. As a whole, the annual VC variation was positively correlated with precipitation, the correlation coefficient was 0.86, indicating that precipitation was the dominant driving force of vegetation dynamics. The correlation coefficient between VC and temperature is -0.42. The composition of land use structure was evaluated using data derived from the Landsat images obtained in 2000, 2006 and 2013 with the 3S technology. The study area was primarily comprised of grassland, which occupied 85.25% of the total study area. The results revealed that grassland and forest increased more than any other types of land (except for construction land), with their area increasing from 29 637.30 km2 and 58.24 km2 to 30 619.36 km2 and 64.43 km2, respectively, while other types of land decreased to different degrees. Overall, these results indicated that some farmland was transformed to grassland and forest, and some unused land was transformed to grassland and water body. High-coverage grassland, forest and farmland increased in the area. The annual VC variation was correlated with land use/cover change, which was an important factor driving the VC increase in the Otindag Sandland during the study period.

Abstract:To investigate the vulnerability of the roots by exogenetic forces, the anti-fracture force and the anti-tension force of lateral-root branches and adjacent upper straight roots diameters of 1～4 mm of 4 shrub species at the age of 3~4 years were measured with the testing machine in vigorous growing period. The 4 species were Caragana Korshinskii Kom., Salix psammophila C. Wang et Chang Y. Yang, Hippophae rhamnoides Linn. and Artemisia sphaerocephala Krasch. The results showed that the anti-fracture force of lateral-root branches was higher than anti-tension force for C. Korshinskii and S. psammophila, while the anti-fracture force of lateral-root branches were lower than the anti-tension force for H. rhamnides and A. Sphaerphala. The same tendency was observed for the adjacent upper straight roots of 4 plants. The anti-tension strength and anti-fracture strength of lateral-root branches were as follows: C. Korshinskii were (23.70±3.97＜33.66±7.74) MPa, S. psammophila were (14.86±1.28＜17.31±1.91) MPa, H. rhamnides were (10.61±2.40＞3.97±1.23) MPa, and A. Sphaerphala were (5.07±1.25＞2.18±0.39) MPa. The anti-tension strength and anti-fracture strength of adjacent upper straight roots were as follows: C. Korshinskii were 28.02±4.40＜47.06±4.41) MPa, S. psammophila were (20.33±1.76＜27.54±3.82) MPa, H. rhamnides were (15.86±3.90＞8.75±1.71) MPa, and A. Sphaerphala were (8.80±1.74＞6.15±1.01) MPa. For C. Korshinskii and S. psammophila, the roots were be liable to be damaged by anti-tension force in vigorous growing period. For H. rhamnides and A. Sphaerphala, the roots were liable to be damaged by anti-fracture force. The anti-tension strength and anti-fracture strength of lateral-root branches were lesser than those of adjacent upper straight roots with the same diameter. The anti-tension strength and anti-fracture strength between lateral-root branches and adjacent upper straight roots for the 4 species followed the sequence of C. Korshinski＞S. psammophila＞H. rhamnides＞A. Sphaerphala. The roots with 1 to 1.5 mm played a leading role in the soil-fixing of 4 kinds of plants.