Abstract:Water erosion processes are the focus of soil erosion research driven by disciplinary development and social demands. By summarizing and analyzing the studies of water erosion, this paper discussed: (1) the concept and study methods of water erosion;(2) the main content and achievements of water erosion processes studies, mainly including detachment-transport-deposition on hillslope, erosion-transport-accumulation in watersheds, and water erosion models. Finally, research challenges and future directions were also provided, including water erosion mechanisms, multi-scale features of water erosion, and the mechanisms of soil and water conservation practices.

Abstract:In order to study runoff movement process and its hydraulic characteristics on composite slopes, runoff velocity was measured for 7 runoff rates (10, 15, 20, 25, 30, 35 and 40 L/(min·m)) and 25 combinations (5 uniform linear slopes, 10 concave slopes, and 10 convex slopes) of slope gradients (5o, 10o, 15o, 20o and 25o) by a series of simulated soil flume experiments in laboratory, and corresponding runoff depth, Reynolds number, and Froude number were calculated as well. Total experimental treatments were 175. Results indicated that runoff velocity on uniform linear slope increased with flow path and progressively tended to be steady, and it increased with the slope gradient or runoff rate. Runoff velocity on the downslope segment of convex slope was greater than that on the upslope segment, while the runoff velocity on the downslope of concave slope was smaller than that on the upslope segment. Runoff depth on uniform linear slope decreased with flow path and tended to be steady, and it increased with the runoff rate or decreased with slope gradient. Runoff depth on the downslope segment of convex slope was smaller than that on the upslope segment, but an opposite tendency existed for concave slope. The Reynolds number (Re) of runoff was a constant value along with flow path, and it increased significantly with the increase of runoff rate but was less affected by slope gradient and the combination of slope gradients. The Froude number (Fr) of runoff increased with flow path, and it increased significantly with the increase of slope gradient or runoff rate. Under experimental conditions, Re value was ranged between 200～800, and Fr value was smaller than 2.5. Runoff belonged to laminar flow when runoff rate was smaller than 25 L/(min·m), otherwise it was turbulent flow. The runoff on upslope segment of convex slope was subcritical flow while that on its downslope segment was torrent flow, and the runoff on concave slope usually belonged to torrent flow status in most cases.

Abstract:To clarify the runoff characteristics of sheet erosion during maize growing season, change characteristics of runoff and hydrodynamic parameters of sheet erosion processes were studied on cross ridge sloping farmland with different slope gradients during whole maize growing stage in purple soil area based on the combining method of micro-plot and artificial simulated rainfall. The results showed that: (1) The time of sheet erosion occurrence was after 8 minutes of the rainfall on slope gradient with 15°at the jointing stage and tasseling stage, and the time of sheet erosion occurrence had the significant difference between the jointing stage, tasseling stage and seedling stage, mature stage. The time of sheet erosion occurrence was after 6 minutes of the rainfall on slope gradient with 20°at the jointing stage and tasseling stage, and the time of sheet erosion occurrence had the significant difference between the jointing stage, tasseling stage and seedling stage, mature stage. (2) On slope gradient with 15°, the runoff amount and runoff rate showed that mature stage＞seedling stage＞tasseling stage＞jointing stage, and the runoff amount and runoff rate was 31.25 L and 1.04 L/min respectively at the mature stage. However, on slope gradient with 20°, the runoff amount and runoff rate showed that seedling stage＞mature stage＞tasseling stage＞jointing stage, and the runoff amount and runoff rate was 34.62 L and 1.44 L/min respectively at the seedling stage. The runoff amount ascended with the increasing slope gradient during whole maize growing stage. (3) On slope gradient with 15°, runoff shear stress had no significant difference among the growing stages of maize, and the other hydrodynamic parameters showed the minimum at tasseling stage. On slope gradient with 20°, unit stream power had no significant difference among the growing stages of maize, and the other hydrodynamic parameters showed the minimum at tasseling stage or jointing stage. Stream power and section flow energy were the best parameters closely related to the runoff rate of sheet erosion process on cross ridge sloping farmland. Runoff characteristics of the cross ridge sloping farmland could be well described by stream power and section flow energy on the condition of our experiment. This results would provide theory basis for the effective prevention and control of sheet erosion in purple soil area.

Abstract:A field experiment was conducted to investigate the effects of six fertilization treatments, no fertilization (CK), conventional fertilization (CF), 90% of CF (90%CF), 80% of CF (80%CF), fertilization with slow release complex fertilizer (CRF), and organic-inorganic fertilization (MF), on runoff and leaching losses of nitrogen in paddy field. Major results were as follows: Application of fertilizers sharply increased the concentrations of total nitrogen (TN) and ammonium nitrogen (NH4+-N) in surface water. The concentrations reached peak values in 2 days and then rapidly decreased and stabilized at below 15% of the peak values in 7 days after fertilization. It was the critical period to control runoff losses of nitrogenin one week after fertilization. Reducing fertilization could significantly reduce the concentration of nitrogen in surface and leaching water. Except for CK, the amount and rate of TN losses from different treatments through runoff were 8.81～15.78 kg/hm2 and 2.58%～4.96% of applied N, respectively. The losses of runoff TN from 90%CF, 80%CF, CRF, and MF were 22.05%, 34.16%, 44.17% and 33.52% lower than that from CF. Similarly, the amount and rate of TN losses from different treatments through leaching were 18.86～40.39 kg/hm2 and 3.55%～11.77% of applied N, respectively. The TN losses from 90%CF, 80%CF, CRF, and MF were 24.57%, 26.52%, 53.29%, and 26.97% lower than that from CF. Reducing 20% of fertilizer N not only could reduce the runoff and leaching losses of TN, but also could ensure rice yield and improve utilization of nitrogen.

Abstract:Splash broke soil surface structure and provided abundant material for subsequent erosion. Rainfall simulation experiments on Lou soil were performed to study its splash erosion characteristics. Using the rate of splash erosion, the soil particle composition before and after rain and the surface intensity to describe the splash erosion characteristics. Results indicated that the splash erosion process could bedivided into three stages according to splash erosion rate. First, the splash erosion rate decreased rapidly, splashed out particles were mainly the loose particles on the surface. Second, splash erosion rate decreased slowly, and the raindrop kinetic energy was mainly used to destroy the soil structure. Finally, the splash erosion rate became constant, the formation of compact layer composed by fine particles formed in aggregate made the splash erosion rate tend to be stable. Under the rainfall intensity of 90 mm/h, the threshold particle size of enrichment and consumption was 0.05 mm. If the particle size was more than 0.05 mm, the function of raindrop was separation. If the particle size was less than 0.05 mm, the function of raindrop was transport. When the moisture content was equal, the longer the rainfall duration the shallower the penetration depth of soil. The surface intensity of Lou soil was continuously increasing. With the rainfall duration, and 0 to 30 min was the critical period of crust formation. Splash erosion process of Lou soil was a process that surface soil particle composition changed constantly and surface strength improved gradually.

Abstract:The characteristics of runoff and sediment, nitrogen and phosphorus losses under soil management measures in sloping farmland in purple hilly region were studied by the method of field runoff plot observation. Soil management measures were humic acid (HA), polyacrylamide (PAM), green manure (GM), and one control group (CK) was set. The results showed that: A-type (small rainfall, short duration, low rainfall intensity) rainfall occurred more frequently in the study area, which accounted for 71% of the total number of rainfall recorded. However B-type (large rainfall, long duration, moderate rainfall intensity) and C-type (moderate rainfall, moderate duration, high rainfall intensity) rainfall were more likely to produce runoff and sediment. Critical rainfall of erosive rainfall of soil management measures were quite approximate, which meant that the sloping farmland began to produce runoff and sediment when rainfall was more than 10 mm. The runoff yield of A-type rainfall: CK (123.49 L)＞HA (60.67 L)＞GM (53.67 L)＞PAM (32.15 L), the difference was significant among soil management measures（P＜0.05）. Sediment yield: CK (30.91 g)＞HA (10.49 g)＞GM (5.50 g)＞PAM (5.12 g), the sediment yield of control group was significantly different from that of GM and PAM. The difference of runoff and sediment yield among the measures were not significant under B-type rainfall. The runoff yield of A-type rainfall: CK (375.45 L)＞HA (26 L)＞GM (239.00 L)＞PAM (182.10 L), the runoff yield of control group and PAM was significantly different. No significant difference was found in sediment yield among soil management measures. The nitrogen loss of several conservation practices varied significantly, the total nitrogen loss of control group was 2.1～2.6 times of that green manure and polyacrylamide, hydrolysis nitrogen loss was about 2.7 times of that green manure and polyacrylamide. The general trend of phosphorus loss in the runoff:The control group＞green manure＞humic acid＞polyacrylamide, however no significant difference was found among them（P＞0.05）. The loss of phosphorus in runoff is mainly in the form of water soluble phosphorus. Polyacrylamide, humic acid and green manure significangtly benefit of the reduction of runoff, sediment and nitrogen and phosphorus loss, and the polyacrylamide was most effective under the condition of A-type rainfall.

Abstract:In order to better understand the effects of different fertilization methods on black soil region slopes nutrient loss, exploring different fertilization methods on black soil nutrient loss of slope law, this test used indoor artificial simulated rainfall method systematically to study the influence of surface spraying and mixed fertilization on nutrient loss in black slope under five different soil bulk densities. The results showed that: Surface spraying and mixed fertilization on the black soil had no significant effect on slop runoff process, two fertilization methods, runoff intensity changes were basically the same, the cumulative rainfall runoff also increased with duration extended linear growth relationship. Fertilization of NPK concentration changed in runoff, had a very significant impact. Regardless of soil bulk density increased or decreased in the early runoff, solute concentration at the surface spraying process was much higher than the corresponding mixed fertilization processing, surface runoff spraying nitrate, soluble phosphorus and potassium ions initially runoff concentrations corresponded to 2.6～3.2, 2.1～2.6 and 1.7～2.1 times the combined application process. The total amount of nutrient loss from the point of view, under the same conditions nitrate density, soluble phosphorus, potassium loss volume mixed fertilization were 9～11, 7～10 and 3～6 times at the surface spraying conditions. And with the increase of soil bulk density, surface spraying and mixed fertilization and potassium nitrate loss of two fertilization methods gap narrowed, while the gap between the amount of phosphorus ions loss increased. When the soil bulk density was less than 1.2 g/cm3 the power function fit factors in surface spraying was higher than that in mixed fertilization, when the slope soil bulk density was greater than or equal to 1.2 g/cm3, the mixed fertilization fitting coefficient was higher than the surface spraying.

Abstract:In order to reveal the influence of rain intensity on nutrient losses from Karst bare slope, characteristics of runoff nutrient loss on Karst bare slope under different rainfall intensities were studied through artificial rainfall experiments based on simulating Karst bare slope in a steel tank with the adjustable slope and degree of underground holes (cracks). In each experiment, the tank was filled with soils and rocks. Results indicated: (1)Surface runoff didn’t generated on karst bare slope under 15 and 30 mm/h rainfall intensities, however, the surface runoff was yielded when rainfall intensity increased to 50 mm/h, and the underground holes (cracks) produced runoff under any rainfall intensity. (2)In the case of surface runoff, the amount of total nitrogen (TN) and total potassium (TK) loss increased with the rainfall intensity, however, the amount of total phosphorus (TP) loss first increased and then decreased, in the case of underground holes (cracks) runoff, the amount of TN loss first increased and then decreased with the rainfall intensity increasing, the amount of TK loss was positive correlation with rainfall intensities while the amount of TP loss was insignificant correlation with the rainfall intensity. (3)When rainfall intensities were 30 and 50 mm/h, the nutrient loss was dominated by underground hole (crack) loss, and its contribution was 100%, the contribution of TN loss in underground hole (crack) runoff presented the order as 15 mm/h＞30 mm/h＞50 mm/h＞70 mm/h＞90 mm/h, and the order of TP and TK was 15 mm/h＞30 mm/h＞50 mm/h＞90 mm/h＞70 mm/h. (4)Both the runoff volume, TN loss, TK loss in surface runoff and the TK loss in underground holes (cracks) runoff had significant positive correlation with rainfall intensity and its correlation coefficient were 0.926, 0.919, 0.982 and 0.955 respectively. Runoff nutrients loss only through the underground holes (cracks) when the rainfall intensity was 15, 30 mm/h, as the rainfall intensity≥50 mm/h, accompanied with surface runoff loss, and the amount of underground nutrient loss was greater than that of surface nutrient loss.

Abstract:To study the loss characteristics of sediment and total nitrogen (TN) by runoff in a typical watershed of the Southern Shaanxi area under natural rainfall events, Hougou agricultural watershed was selected to examine runoff, sediment and TN in natural rainfall events of rainy seasons during 2011 to 2012. The results showed that the best regression equation was S curve equation between sediment loss flux and runoff of slope land, returning farmland, garden field, and linear functional relation was the best regression equation for orchard field. The reciprocal equation model could describe the relation of TN concentration and runoff in slope land and garden field, linear functional relation could express the relationship of TN concentration and runoff in returning farmland and orchard field. The order of sediment and TN loss flux in different land use in rainy season was: Garden field (4 011.7 kg/hm2)＞slope land (1 720.0 kg/hm2)＞returning farmland (1 606.3 kg/hm2)＞orchard field (776.3 kg/hm2), garden field（15.29 kg/hm2）＞returning farmland（7.20 kg/hm2）＞slope land（4.92 kg/hm2）＞orchard field（1.37 kg/hm2）. The linear equation and power function equation could show the relation of runoff kinetic energy and sediment loss, and the logarithmic function curve and power function equation could explain the relation of runoff kinetic energy and TN loss. The risk of the loss of sediment and TN was the highest at the later stage of rainy season in the Southern Shaanxi area.

Abstract:Characteristics of soil nutrients loss under different land use patterns in Beijing during course of rain were studied. The results indicated that: (1) The surface runoff under different land use patterns had a logarithmic change tendency with the increasing of rain, which ordered grassland＞farmland＞woodland＞orchard. (2) The increasing range of soil erosion of grassland was larger, and farmland, woodland, orchard was lower, which ordered grassland＞farmland＞woodland＞orchard. (3) The surface runoff and interflow of grassland and farmland were significant higher than woodland and orchard (p＜0.05), which ordered grassland＞farmland＞orchard＞woodland. (4) The sediment accumulation under different land use patterns had a exponential function change tendency with the increasing of rain, which ordered grassland＞farmland＞woodland＞orchard. (5) The nitrogen and phosphorus loss in water, sediment nitrogen and phosphorus loss and the total loss of nitrogen and phosphorus ordered grassland＞farmland＞orchard＞woodland. (6) The loss of nitrogen in runoff water, and the loss of phosphorus in erosive sediment under different land use patterns. (7) The total content of nitrogen and phosphorus under different land use patterns antecedent rainfall ordered grassland＞farmland＞woodland＞orchard. The sediment ratio of N/P was higher than that of ratio of N/P antecedent rainfall which indicated that erosion and sediment had an effect of nitrogen and phosphorus enrichment, and the nitrogen enrichment was higher than phosphorus enrichment, which the grassland had the most highest nutrients enrichment. (8) The sediment had a significant or extremely significant positive correlation with the nutrients of sediment, and had a different positive correlation with the nutrients of soil, which implied that the sediment yield could cause the increase of various kinds of nutrients.

Abstract:Fen River watershed was located in the middle reaches of the Yellow River. The variation of runoff volume and sediment load in this area especially the upper watershed had an indicating significance to the change of water-sand regime of the Yellow River. The Lancun station was the most important hydrological monitoring station on the upper Fen River. Based on runoff, suspended sediment load data observed at Lancun station in rainy season from 1954 to 2013, the characteristics and driving factors of suspended sediment load variation were analyzed by using linear trend analysis. The results showed that the declined trend of sediment and runoff were obvious in recent 60 years. But the changes of them not synchronous which the former’s trend was stronger than the latter’s. The precipitation showed no trending variation. However, the precipitation and runoff (P＜0.01), precipitation and sediment load (P＜0.01) showed a significant linear correlation. Floods had a decreased tendency, and this trend was the most evident in the beginning of the 21st century. Using the analysis of double-mass curve, the effect of driving factors on the variation in suspended sediment load had been studied. The double-mass curve showed three breaks (1959, 1981 and 2002) which divided the evolution process of suspended sediment load into four typical periods. The suspended sediment load was mainly affected by rainfall and runoff. Then it decreased significantly after 1959 which might be explained by Fen River reservoir construction. During the period from 1981 to 2002, the runoff and suspended sediment load decreased again. It could be related to the rainless, large-scale mining, urban construction, soil and water conservation measures. The runoff and sediment yield decreased significantly since 2002. In addition to the above reasons, reduction in precipitation especially storm and the second Fen River reservoir trapping sediment were the major cause for sediment reduction in the upper Fen River．

Abstract:The Wenchuan earthquake led to a lot of landslide deposit. It was triggered more serious secondary geological disasters under the condition of rain washing out. In this article, the landslide deposit was chosen to be the research object in the Wenchuan earthquake area, an artificial rainfall device was used to conduct indoor rainfall-interflow production observation experiment at different rainfall intensities (1.0,1.5,2.0 mm/min) and soil-rock ratios(1︰1,1︰2,1︰4). The results indicated that: (1) The interflow increase rapidly in the beginning, then stabilized gradually until the rainfall stopped under the different rock-ratio. (2) The interflow yield presented a significant positive correlation with the rainfall time (R2=0.946 5～0.999 6). (3) Except for the soil-rock 1︰4 of landslide deposit, the time of the interflow production process showed significantly different laws between the soil-rock 1︰1 and 1︰2 is opposite under the increase of rainfall intensity. (4) The soil-rock 1︰4 of landslide deposit only produced interflow yield; Except for the time of interflow production was a little longer than the time of surface runoff when the soil-rock 1︰1 of landslide deposit under the conditions of 2.0 mm/min rainfall intensity, the other’s interflow production was shorter than the time of surface runoff within 10 min.

Abstract:To prove salt transport in roadside soil of low roadbed highway, Heda highway (G11) low roadbed roadside soil was selected as the research object. The preferential flow principle was used to explore the salt transport in the soil water movement process. Analyzed soil profile preferential flow horizontal and vertical distribution characteristics by using brilliant blue dye tracing and image analysis method. The results showed that: Staining area and non-staining area of soil properties had significant differences, staining area had more pore. In the horizontal profile, the number of preferential flow paths with different influence radius decreased with the increase of soil depth. The number of preferential flow paths with 1.0~10.0 mm influence radius in the same layer were far more than the number of paths >10.0 mm influence radius. In the vertical profile, the preferential flow characteristic index as dye coverage (DC), uniform infiltration depth (UF), preferential flow fraction (PF-fr), length index (LI) and peak (PI) were 40.10%, 4.10 cm, 801.96 cm2, 74.44%, 543.6 and 5 respectively. There was obvious preferential flow in roadside soil of low roadbed highway which played an important role in the transportation of salt in soil. The proposed indices provided a good research method to quantify the occurrence degree of soil preferential flow in the future.

Abstract:In order to study the soil water movement characteristics of the slope collapse erosion, the author collected red soil from granitearea of collapse gully erosion in Hubei Tongcheng County and studied the preferential flow and impact factor. The collection of 1 kind of clay and 3 kinds of sand layer were loaded in transparent PVC soil box, 60 cm long, 11 cm wide, and 110 cm high, respectively, in accordance with the order of "sand under the red soil". Rainfall infiltration was simulated using three soil boxes in different initial moisture content (12.2%～23.6%) and rainfall (0.7,1.2 mm/min), and the instantaneous dynamic soil moisture of 20 positions of the soil mass was monitored by the time domain reflectometry (TDR) in high frequency. Thus, according to the spatio-temporal variations of the water content, the soil preferential flow characteristics were recognized. The results showed that the infiltration of precipitation was not uniform infiltration, and when the soil saturated hydraulic conductivity was larger and the path condition of marcropore was better, the preferential flow was more likely to occur, and its scope of influence was more extensive. The greater the rainfall intensity, the more obvious effect the preferential flow and the surrounding matrix, the greater the preferential flow rate. The rainfall intensity of 1.2 mm/min had a preferential flow rate 1.8～4.0 times of that by the rainfall intensity of with 0.7 mm/min. When the treatment of initial moisture content was smaller, the initial flow time was later and the flow rate was smaller. The results showed that the preferential flow was affected by precipitation and initial water content, but the effect of soil properties was greater.

Abstract:Vegetation construction was an important approach to control soil erosion, especially in the slope soil erosion. Converting cropland to forest and grassland was a largest vegetation construction project in loess Plateau and even the whole country. In this study, the effects of revegetation on soil erosion under implementation of the Grain for Green Project were evaluated for five single years (1984, 1996, 2006, 2012 and 2014) using the revised universal soil loss equation (RUSLE) supported by ARCGIS 10.2. Daily rainfall data of three decades (from 1984 to 2014, excluding 1999) of Yan’an weather station was used to calculate the rainfall erodibility (R). Values of topographical factor (LS) were extracted from digital elevation model, which was generated by applying interpolation based on topographic map with a scale of 1∶5 000. The K factor was obtained using physical and chemical properties of soil samples of study area. C and P factors were generally derived from previous studies on the Loess Plateau. Results showed that areas of moderate high, high and very high erosion declined sharply, and most of them transferred to very low, low and moderate. The average soil erosion rate decreased from 15 327.57 t/(km2?a) in 1984 to 3 270.19 t/(km2?a) in 2014. Slope belts of 15°～25°, 25°～35° and ＞35° were the main areas of severe soil erosion. These three slope belts accounted for 44.93%，42.65%，35.78%，23.23% and 22.98% of total study area from 1984 to 2014. Furthermore, the areas with very low, low and moderate erosion occupied 26.53%, 44.24% and 43.47% of the total area of the watershed in 2006, 2012 and 2014, respectively. Generally, the soil erosion in Yangjuangou watershed reduced significantly. It was indicated that revegetation had positive effects on soil and water conservation and soil erosion, and the Grain for Green Project led to a success in soil erosion control.

Abstract:This study used quantitative remote sensing method, in combination with RUSLE model, and GIS software, utilizing a series of data such as digital elevation model (DEM), rainfall and soil properties, the characteristics of spatial-temporal differentiation of soil erosion of Zuli river basin from 1995 to 2015 was estimated. By analysis of the temporal variation of the erosion modulus, temporal variation of erosion intensity and spatial pattern of erosion intensity, the results of this research were summed as follows: The erosion modulus was 2 877.87 t/(km2·a）in 1995, 3 372.24 t/(km2·a） in 2005, and 3 713.23 t/(km2·a） in 2015, respectively, suggesting the increasing erosion rates. In the case of the spatial pattern of soil erosion, the erosion modulus was high value on the high side place in the middle of the study area and low value in the south and north. Besides, the soil erosion mounts was high on the side in the mountains and low near the river valley. Four types of simulation were proposed according to the characteristics of study area. The results showed that the efficient governance model (EGM) was the best governance model area, which could effectively control soil loss, the average modulus properties was 2 656. t/(km2·a）.

Abstract:With field survey and laboratory experiment, the relationship between the shear strength under different land uses and its influential factors were studied to provide a scientific basis for different land use assessment of regional soil erosion. Five land use patterns, i.e. conifer-broadleaf mixed forests, shrubs lands, gardens, slope farmlands, wastelands were selected as samples to conduct observations upon these values: The soil shear strength index, bulk density, moisture content and dry density, as well as the porosity, MWD of soil aggregate and clay/silt value. Then the influential factors were analyzed with the method of the grey correlation, and the results revealed that the soil cohesion on a same slope gradually decreased from the higher parts to the lower ones under the same land use pattern. Meanwhile, the shear strength, in different lands, changed like this: Sloping farmlands＞gardens＞conifer-broadleaf mixed forests＞wastelands＞shrubs lands. Finally, the soil bulk density had the greatest correlations with the soil cohesion (C) and internal friction angle (φ), while the MWD had smallest correlations with them. To sum up, there were linear relations between the soil shear strength and soil bulk density, total porosity, moisture content and dry density respectively.

Abstract:Based on issues like instability of collapsing gully wall caused by the development of granite exposed areas which vulnerable to the impact of wet and dry cycles, by a series of unconfined compressive strength test, we determined variation patterns of the unconfined compression strength under wet and dry cycle at different layer soils in collapsing gully, and established a predictable model of unconfined compressive strength combined of soil depth ratio and dry wet cycles at different levels of soil collapse. The results showed that: The unconfined compression strength at surface soil layer, red soil layer, speckle layer, detritus layer decreased most after 1st wet and dry cycle, of 26%, 15%, 40% and 49%, respectively; the decrease slowed down after the 2nd to the 4th wet and dry cycle; the unconfined compression strength remained stable after the 5th wet and dry cycle; with the increase of wet and dry cycles, the unconfined compression strength of dilapidated granite at different soil level generally performed as surface soil layer＞red soil layer＞speckle layer＞detritus layer; under different wet and dry cycle times, the stress-strain relationship curve tended to soften and reached the peak at 2% strain, but at red soil layer, the fluctuation tended to be intense after the 3rd wet and dry cycle; the predicted value of the unconfined compression strength correlated with measured value significantly (R2=0.91), the model had certain value forecasting wet and dry cycles on unconfined compressive strength of different layer soils in collapsing gully in Tongcheng areas.

Abstract:The objective of this paper was to illustrate the mutual influence of runoff & sediment characteristic as well as its hydraulic parameters under different slope gradients (5°, 10°, 15°, 25°), tillage measures (no treatment, artificial backhoe plowing, artificial digging plowing, contour tillage) and rainfall intensities (60 mm/h,120 mm/h). Successive rainfall of 90-minutes duration was performed in the rainfall simulation laboratory of the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau. Runoff and sediment were collected once per two minutes when runoff came forth. Results showed that the amount of runoff and sediment of slopes with different tillage measures were in an order: no treatment＞artificial backhoe plowing＞artificial digging plowing＞contour tillage. This behavior illustrated that their soil & water conservation effects enhanced sequentially. At loess slopes with same tillage method, their runoff increased significantly from 1.04 kg/min to 3.02 kg/min under the rainfall intensity of 120 mm/h when compared with the rainfall intensity of 60 mm/h, and the rainfall intensity had a great impact on runoff. Simultaneously, runoff and sediment amount were logarithmically increased with rainfall duration. Under the same rainfall duration, overland flow transformed from the transitional and subcritical flows to the turbulent and supercritical flows with the increase of rainfall intensity and slope gradient, thereby exacerbating the soil erosion. Tillage, rainfall intensity and slope gradient were critically important factors which affected slope erosion process, sediment yield and its hydraulics features. Thus, the adoption of effective conservation tillage, weakness of slope effect will contribute to the soil and water conservation at the loess sloping land on the Loess Plateau.

Abstract:The effect of different shrub grassland on soil anti-erodibility in alpine areas in eastern Qilian Mountains was studied by the method of field investigation and laboratory analysis. In this research, three alpine shrub grasslands were selected in the experimental area, which were Potentilla fruticosa shrub grassland，Salix shrub grassland and Rhododendron shrub grassland. The results showed that large-aggregate (＞0.5 mm aggregate) was the main composition of water-stable aggregate in different shrub grassland. The order of soil structure damage rate of different alpine shrub grassland was Salix shrub grassland>Rhododendron shrub grassland＞Potentilla fruticosa shrub grassland. Soil aggregate survival rate of Rhododendron shrub grassland was the lowest. The order of soil water stable index of different alpine shrub grassland was Rhododendron shrub grassland（97.1%）＞Salix shrub grassland（96.9%）＞Potentilla fruticosa shrub grassland（95.8%）. The soil water stability index of Rhododendron shrub grassland was the biggest（95.0%）.Otherwise, Potentilla fruticosa shrub grassland was the smallest（92.9%）. So the soil anti-erodibility of Rhododendron shrub grassland was the best, Potentilla fruticosa shrub grassland was the worst. Through the grey correlation method, ＞0.5 mm machinery aggregate content, ＞0.25 mm aggregate content, ＞0.25 mm water-stable aggregate content, ＞0.5 mm water-stable aggregate content, soil structure damage rate, mean weight diameter of water-stable aggregate, organic matter, soil disintegration rate, soil water stable index and soil anti-erodibility were selected to evaluate soil anti-erodibility. The results showed that the main factor influencing soil anti-erodibility in alpine shrub grassland was the water stable index, ＞0.25 mm stable aggregate and water stability aggregate average diameter.

Abstract:This study was aimed to explore the sand-fixing mechanism of the mixing soil with Feldspathic Sandstone and Sand in the Mu Us Sand Land. This paper analyzed the texture of Feldspathic Sandstone and Sand, holding water retention, soil crusts and freeze cap using combination technical methods of experiment, simulation and field observation. The results showed that: (1) sandstone and sand distribution ranges were 0.317～709.0 μm and 0.564～2 000.0 μm respectively, when mixed, that could expand the sand composition, improve the texture of sand and surface roughness;(2) The moisture content of the sand reduced rapidly when it changed over the time, it could be reduced from 15.90% to 3.26% within 54 h, and the moisture content of the Feldspathic Sandstone, mixture with Feldspathic Sandstone and Sand were 21.39% and 15.87%, the rate of moisture content declined slowly. The capillary porosity of Feldspathic Sandstone was higher than it of sand. When the Feldspathic Sandstone and sand were mixed, they could improve porosity of sand and reduce the saturated hydraulic conductivity. So, the Feldspathic Sandstone improved water retention properties of sand;(3)Under the action of water, it formed physics crust on the surface quickly after the Feldspathic Sandstone and sand mixed, but it was difficult to form at the anhydrous state. There was significant effect on the thickness of crust formation at the different ways of mixing proportions crust formation. The formation of sandy crust effectively prevented the occurrence of sand dunes and sand flow, so it achieved the role of sand fixing.

Abstract:Sand flux structure，the distribution of sediment runoff in the vertical height，was the product of the combined effects including the mechanical composition of sand，the degree?of?sorting，the feature of near surface airflow，the air humidity，the underlying form，the structure of vegetation，and so on. It could directly characterize the movement of sand，analyze the situation of surface erosion and deposition，master the morphological development and evolution of aeolian landform. It played an important role in the theory and practice. Based on these，it was very necessary to carry out the characteristics of sand motion in the hinter land of Taklimakan desert. In order to reveal two-dimensional spatial distribution of the sand flow and the sand of different?particle，bare sandy land and sand barriers were selected. Two kinds of sand collectors (one was set to observe sand flow in the vertical height，the other was set to observe sand flow in the horizontal direction) were installed to measure the features of sand flow movement. In-situ observation was performed from April 2015 to June 2015. Then differentiation process between sand flux structure and sand particle?size distribution and nylon net checkerboard barrier were researched. The results were as follows：(1) The sand flux structure exhibited an exponential decay distribution at the bare sandy land，took on unique effect of elephant nose in the front of the barrier and exhibited obsequent effect of elephant nose in the middle of the barrier. Sand-barrier obviously reduced the sand transport rates of the near-surface (0～42 cm). (2) At the bare sandy land，the vertical mass flux profiles of the very fine sand and coarse silt groups exhibited exponential decay distribution，the vertical mass flux profiles of silt，fine silt and the very fine silt exhibited exponential increase distribution with appearing exponential decay distribution in the away-bed region. Going across the sand barrier，the vertical mass flux profiles of sand and the vertical distribution patterns of sand had changed in the near-bed region (0～32 cm). (3) Sand barrier not only changed the spatial distribution of the sand flow，but also changed the spatial distribution of different size sand. All of those，the spatial distribution of fine sand had change the most.

Abstract:To reveal the characteristics of dust emission caused by wind erosion of soil in the cultivated land, an indoor simulated wind tunnel experiment was conducted. In this study, we used soils sampled from the different cultivated land in the northern and middle Ningxia Autonomous Region to investigate the effect of wind speed on the dust emission. The PM10 concentration was monitored and then the PM10 flux was calculated basing on the concentration to compare capability of dust emission. The results showed that dust emission in the cultivated land was a instantaneous process which completed as soon as soil exposed to the wind. The trend of accumulated max PM10 flux was complicated since the largest increase of PM10 flux of PL occurred when the wind speed increased from 6 to 9 m/s, while the largest increase of PM10 flux of TX and YC occurs when the wind speed increased from 15 to 18 m/s. The accumulated average PM10 flux of every soil increased with wind speed in a similar trend which are quadratic functions. There was a logarithmic regression between average PM10 flux and amount of wind erosion. The capability to dust emit of four soils listed in the order of PL＞TX＞YC＞YN when the wind speed higher than 9 m/s.

Abstract:To explore the optimal model of border strip fertilization for summer maize, the distribution and variation of soil water and nitrate nitrogen in the field with different methods (fertigation and broadcast fertigation), timing and rates of fertilization were investigated. Results showed that 2 days after applying water and fertilizer, the spatial distribution variability of soil water was far less than that of soil nitrate nitrogen, and increasing the inflow rate appropriately could improve the distribution uniformity of soil moisture along length direction. The change of the storage efficiency of soil nitrate nitrogen in the effective root zone of summer maize was not obvious and it was same to soil moisture. Under the same condition of inflow rate, the distribution uniformity of soil nitrate nitrogen along length direction of summer maize with fertigation (between 86.1% and 96.9%) were higher than that with broadcast fertilization (between 89.3% and 89.7%). The border strip fertilization with the inflow rate of 4 L/(s·m) and with applying fertilizer as water advanced at 33% of the border length could produce high proportion of soil water and nitrogen accumulation in the effective root zone and provide optimal distribution uniformity along length direction, then formed a spatial homogeneity distribution of soil water and nitrate nitrogen contribution which was beneficial to crop absorption.

Abstract:Optimizing regulation irrigation schedule，rates and coupling with N fertigation was an effective way for realizing crop production improvement as well as water and nutrient use efficiency enhancement. The effects of drip-irrigation frequency (which controlled soil matric potential at 0.2 m depth immediately under drip emitters controlled higher than -20, -30 and -40 kPa) and nitrogen fertilizer level (0, 180, 225, 262.5, 300 and 345 kg/hm2) on the maize grain yield, water use efficiency and nitrogen use efficiency were studied by the means of using a split plot experiment with two factors. There was an obvious tendency that the plant height and LAI of maize increased with levels of water, but those decreased when the N applied rate beyond 262.5 kg/hm2. The response of dry matter weight of maize in harvest time to irrigation water was: W1 (－20 kPa)＞W2 (－30 kPa)＞W3 (－40 kPa). The effects of nitrogen fertilizer amounts on the amount nitrogen of seed in maize in harvesting dates was : N3 (262.5 kg/hm2)＞N4 (225 kg/hm2)＞N2 (300 kg/hm2)＞N5 (345 kg/hm2)＞N0 (0 kg/hm2). Both irrigation and N supply exerted a significant role on maize yield as well as yield component of kernels per row and 100 grain weight. An obvious positive interaction was obtained between water and nitrogen. Moreover，the effect of N on yield was substantially higher than that of irrigation. N fertilizer use efficiency increased with increasing N level within N supply range of 0～262.5 kg/hm2, and then dropped markedly when N rate above 262.5 kg/hm2．And in this range, it was found that the water use efficiency (WUE) and irrigation water use efficiency (IWUE) increased with increasing N level，while that decreased with increasing irrigation rate. At the suitable irrigation level of W3, the WUE，IWUE of 42.20～49.23 kg/mm and 63.31～78.00 kg/mm could be achieved. The highest yield was obtained in the combination treatments of W2N4 with the value of 20 489.06 kg/hm2. W3N3 combination treatment had the highest WUE, NRE and the yield could achieve 18 730.62 kg/hm2, which decreased 8% compared with the treatment of W2N4. In the present experiment, the optimal combination of nitrogen rate and irrigation frequency was W3N3 for the higher nitrogen fertilizer use efficiency, water use efficiency, and could achieve ideal grain yield, meanwhile, which had lower potential harm for environment.

Abstract:In order to determine the effect of limited irrigation on water consumption and water use efficiency of spring maize field in newly cultivated sandy land in desert oasis of Hexi Corridor, the dynamics of soil moisture at various crop growth stages of maize were continuously monitored using soil neutron probe combined with drying-weighing method, and daily water consumption, soil evapotranspiration, and crop water use efficiency were also analyzed. The results indicated that no significant (P＞0.05) difference was found in daily water consumption among treatments except during sowing to Five-leaves and jointing to booting, and daily water consumption varied from low to high then to low during plant growth, the maximum value appeared during silking to middle filling with 6.8 to 10.0 mm/d. The seasonal evapotranspiration (ET) in treatment MI1 which yielded the highest under the least seasonal irrigation was slightly lower than in MI5 under more irrigation water. Among all the treatments, the ET in CK was 16.0% higher than in MI5, with the lowest in MI3. Water use efficiency (WUE) of maize was the highest in MI1 and MI3, and there were significant (P＜0.05) differences between these two treatments and the others. The lowest WUE was found in MI4, and the WUE was significantly increased by 19.3%, 34.1%, 15.3%, and 25.4% both in MI1 and MI3 than in MI2, MI4, MI5 and the CK. There were significant differences in the irrigation water use efficiency (IWUE) between MI1 and the other treatments and CK, so were between MI3 and the other treatments and CK. The highest IWUE occurred in MI1 with the least seasonal irrigation but the highest grain yield, while the lowest IWUE appeared in MI4. In all the treatments, IWUE was significantly improved by 35.1%, 14.6%, 61.0%, 36.7%and 48.4% in MI1 than in MI2, MI3, MI4, MI5, and the CK respectively, and IWUE was significantly improved by 17.9%, 40.4%, 19.3%, and 29.4% in MI3 than in MI2, MI4, MI5, and the CK, while 17.7% of IWUE was improved in MI5 than in MI4. Therefore, limited irrigation could improve WUE and IWUE of maize in oasis irrigation field. However, the effect of limited irrigation on WUE and IWUE improving was not absolutely stable.

Abstract:In order to reveal the effects of edible fungus residue on vegetation, soil organic carbon and enzyme activities of sandy soil, sandy soil was sampled in the northwest Sichuan as research object by five point sampling method. The results showed that the treatment of mixing 5 kg/m2 edible fungus residue in soil (F1), mixing 10 kg/m2 edible fungus residue in soil (F3) and mixing 15 kg/m2 edible fungus residue in soil (F4) could significantly increase vegetation coverage and height, biomass, soil water content, organic carbon and enzyme activities, and decrease the soil bulk density. Compared with CK, the treatment of F4 increased vegetation coverage and height, biomass, soil water content, organic carbon and enzyme activities by 272.20%, 144.51%, 228.85%, 616.46%, 93.25%, 135.90%, 129.22%, 154.41%, 99.88%, 115.03% and decreased the soil bulk density by 39.04%. It indicated that the mixing of edible fungus residue and soil had a remarkable effect on vegetation, soil physicochemical properties and enzyme activities. The treatment of F2 could increase soil organic carbon, cellulase, amylase, invertase and polyphenol oxidase activity compared with the CK, but it was significantly lower than F1, F3 and F4. This result indicated that the effect of cover the soil was better than that of edible fungus residue mixed application. Correlation analysis showed that the SOC, below biomass and enzymes activities were obviously positive correlation（P<0.01）.

Abstract:To improve the water and fertilizer utilization efficiency of bubbled-root irrigation, the indoor infiltration experiment was conducted to explore the bubbled-root irrigation wetting front movement and soil moisture and nitrogen distribution rules at different fertilizer solution concentration criteria. Results showed that same infiltration time, with the increase of the fertilizer concentration, the wetting front migration distance and the soil water content at the same location in the wet body and the mass fraction of ammonium nitrogen and nitrate nitrogen increased. The relationship between wetting front migration distance and infiltration time was a power function and the coefficient of determination reached 0.99. With the distribution of fertilizer solution infiltration, wet body achieved a sense of stability, uniform moisture content distribution, moisture content of peak position went down gradually. The amount of ammonium nitrogen decreased gradually and the maximum value of nitrate nitrogen was reached in 5 d moist body. Nitrate nitrogen migration regularity and moisture was consistent, along with the moisture loss. The above research results could lay the foundation for further research on efficient bubbled-root irrigation technology of using water and nitrogen.

Abstract:To explore the suitability of grass planting one lawn under backfill conditions as well as the impact of irrigation with reclaimed water on grass growth and soil properties. This paper chooses Lolium perenne as the test subject by setting up three groups, fresh water irrigation, reclaimed water irrigation and fresh+reclaimed water alternative irrigation in the form of indoor pot experiment. It studies the impact of irrigation with reclaimed water on grass growth and soil properties in Hohhot. The results showed as follows: (1) Compared with fresh water irrigation, lawn with fresh+reclaimed alternative irrigation and reclaimed water grows by 23% and 34% respectively. (2) The scores of quality, coverage and evenness of lawns indicate: reclaimed water irrigation＞fresh+reclaimed alternative irrigation＞fresh water irrigation. But the difference is not significant (P＞0.05). (3)When the observation is ended, the salt of soil irrigated by fresh+reclaimed alternative irrigation and reclaimed water increases by 8% and 3% respectively. (4) With different irrigating waters, Lolium perenne’s absorption of soil heavy metals varies and the heavy metal contents are different in the soil. The results showed that reclaimed water irrigation has an obvious role in enhancing the growth rate of the lawn and the color of the lawn irrigated by reclaimed water is visibly better than others (P＜0.05). At the same time, the further analysis of test soil and lawn showed that claimed water irrigation will not impose soil damage on lawns and soil is not affected. It can be seen that it is feasible to irrigate lawn with reclaimed under backfill conditions in the short term.

Abstract:This case takes citrus garden in purple hilly area as the research object, using mechanical deep loosening method, according to the number of ditch irrigation biogas fertilizer (one subsoiling ditch nitrogen 45 t/hm2 biogas fertilizer), we research the effects of biogas fertilizer deep application in citrus orchards soil aggregates, soil nutrient and yield of Citrus, we set 5 pieces of experiment treatment: (1) CK:only fertilizer application; (2) T0: no subsoiling + biogas fertilizer 45 t/hm2; (3) T2:2 subsoiling + biogas fertilizer 135 t/hm2; (4) T3:3 subsoiling + biogas fertilizer 180 t/hm2, (5) T5:5 subsoiling + biogas fertilizer 270 t/hm2. Results show that: Biogas fertilizer improves the number of soil in 0.25～2 mm water stable aggregates, reduces the ＜0.25 mm microaggregate number and 2～5 mm water stable aggregate amount significantly increased with increase of subsoiling ditch and biogas fertilizer application amount; In the 0-20 cm soil layer T3 and T5 treatment aggregate mean weight diameter (MWD) respectively, compared to the control treatment and biogas fertilizer without T0 treatment improves the 27.6%～29.9% and 12.2%～14.2%.The content of organic matter, total nitrogen and total phosphorus in 20 cm soil layer was higher than that of 20—40 cm and 40—60 cm. In 0—20 cm soil layer, soil organic matter content of the T3 treatment were increased 1.46～2.90 g/kg and 5.00～6.44 g/kg compared with the soil organic matter content of CK and T0. The biogas fertilizer deep application of T5 treatment significantly increased the contents of soil total nitrogen content. T3 and T5 treatment can significantly improve the total phosphorus content of 0—20 cm and 20—40 cm and total potassium content of 20—40 cm soil. Compared with conventional fertilization (CK), T3 and T5 treatment significantly improved the yield of Citrus in the test orchard, and the average yield were 3.57 and 3.66×104 kg/hm2 in 2014—2015, the average yield increased 4.20% and 7.02%; Each biogas fertilizer (T0、T2、T3、T5) is significantly higher than the solid acid of CK, the ratio of solid acid level of performance are T3＞T5＞T2＞T0＞CK; T5 treatment significantly increased the content of Vc, two years were increased 4.39 and 4.48 g/100ml respectively. Hilly orchard rows deep application biogas fertilizer (180～270 t/hm2) not only can improve soil structure as well as the nutrient content, and improve the yield and fruit quality for 2 years, so that it can ensure the sustainable development of citrus production. The results provide a scientific basis for improving soil fertility and fruit yield, orchard fertilizer rational management.

Abstract:The aim of this study was to investigate effects of long-term fertilization on lateritic red soil fertility in cropping-green manure planting system and provided corresponding sustainable management. A long-term field experiment was conducted to study the effects of different fertilization method on soil nutrients, enzyme activities and microbial traits in lateritic red soil. The results showed that : Compared to the control treatment, long-term fertilization significantly increased the soil organic matter, alkali solution nitrogen, phosphorus, rapidly-available potassium nutrient, and improved the soil sucrose invertase, urease and phosphatase activities, and increased the content of soil microbial biomass carbon and nitrogen and microbial community species richness, dominance, evenness. The long-term fertilization increased soil nutrient content by 4.5%～117.2%, enzyme activity by 4.9%～68.1% and microbial diversity by 3.2%～71.9%, respectively. The microbial biomass carbon and nitrogen content were increased by 7.8%~36.9% and 21.4%~65.7%, and the most significant effect was observed as following: Organic manure (M), organic and inorganic fertilizer treatment (NPKM) and straw with inorganic fertilizer treatment (NPKS). The significant correlations were found between soil nutrient, soil enzyme activity, microbial diversity as well as microbial biomass carbon and nitrogen (p＜0.05). In summary, the long-term single organic fertilizer or organic combined with inorganic fertilization was a good measure for fertility improvement in soil of cropping-green manure planting system.

Abstract:Soil fertility was an important component of soil quality. In order to investigate the present statue of sloping farmland soil fertility in the water erosion zone of China, selecting field scale as the research unit, soil samples from the soil layer of 0—20 cm were collected and tested 11 soil physical and chemical indicators for 36 sampling sites. The principal component analysis (PCA) combined with Norm values and correlation coefficients between the 11 indicators were employed to select the key indexes for representing soil quality. The key indexes were soil organic matter, total kalium, pH value, cation exchange capacity and clay content. S-type and parabola-type membership functions were used to transform the indicators into dimensionless dates and to evaluate single indicators. Comprehensive index model was used to calculate integrated fertility index (IFI) for each sampling point, providing the basis for quantitative analysis of sloping farmland soil fertility in the water erosion zone of China. The results showed that: (1)The values of membership functions of the indexes revealed the CEC and clay were the major limiting factors for this region. (2)The IFI for water erosion zone of China varied from 0.17 to 0.72, and the mean value was 0.44±0.15, belonging to moderate fertility level. The proportions of integrated fertility index ranked a slow, middle, high level were 27.8%, 58.3% and 13.9% of the total area of sloping farmland, respectively. (3)There was no significant difference about integrated fertility indexes between the six secondary partition regions. The IFI of the northeast low mountain and rolling hill region was the highest, while the IFI of the Loess plateau region was the lowest. The results of the study had guiding significance for rational fertilization and sustainable utilization of land resources for sloping farmland in the water erosion zone of China.

Abstract:Two typical slopes of 35-year-old Larix principis-rupprechtii plantation (southeast slope A and south slope B) were chosen to be studied in order to elucidate the spatial characteristics of soil moisture under the influence of rainfall and vegetation factors such as canopy leaf area index and litter layer thickness in forest land. Following the principles and methodology of spatial pattern analysis in geostatistics, and took the characteristics of the selected slopes into consideration, the linear sampling method were chosen to measure the moisture of surface (0—20 cm) and subsurface (20—40 cm) soil, canopy leaf area index, litter layer thickness, slope degree and distance from the nearest tree trunk. The spatial variation characteristics of soil moisture before and after raining were analyzed combining with classical statistics and geostatistics methods, the relationship between soil moisture and the main environmental factors before and after raining were analyzed using the Pearson correlation analysis, the spatial distribution of soil moisture before and after raining on the slopes was obtained by Kriging interpolation. Result indicated that there was significant spatial autocorrelation of soil moisture of surface and subsurface layer on both selected slopes. In addition, the soil moisture presented an obvious patchy distribution pattern. Before raining, structural ratio of surface soil water content were 0.20 and 0.16 respectively on slope A and B, indicated that soil moisture of surface layer had a strong level of spatial autocorrelation selected slopes. Meanwhile, the structural ratio of subsurface soil water content was 0.50 on both slope, soil moisture of subsurface layer indicated medium level of spatial autocorrelation on both chosen slopes. The range of the autocorrelation functions of surface soil moisture on slope A and B was from 27.6 m to 23.7 m, and the range of subsurface soil moisture was from 54.9 m to 186.0 m respectively, manifested that spatial autocorrelation of the soil moisture existed in a large range. After raining, the structural ratio of surface soil water content were 0.13 and 0.11 on slope A and B, the ratio of subsurface were 0.28 and 0.20 respectively, the range of the autocorrelation functions of surface soil moisture was from 17.7 m to 17.3 m, and the range of subsurface was from 31.4 m to 42.6 m respectively. Those results indicated a shrinking trend of the range of spatial autocorrelation after rainfall. Pearson correlation analysis revealed that before rainfall, the distance from the nearest tree trunk and litter layer thickness made the main impact factors of the spatial variation of soil moisture on slope A. However, canopy leaf area index and litter layer thickness became more significant variables after raining. So, this precipitation process (11 mm of rainfall amounts) increased the spatial heterogeneity and autocorrelation of soil moisture, in addition, the interception and redistribution of rainfall caused by the tree canopy and litter layers was the main reason of the increase of the soil moisture spatial heterogeneity in the study area.

Abstract:The thermal diffusion sap flow probes were used to continuously measure the sap flow rate of sample trees of Pittosporum brevicalyx growing as subdominant trees species in the Maolan Karst forests from February 2012 to March 2014. Simultaneously, the environmental factors were measured including air temperature, solar radiation, precipitation and soil moisture, etc. The aims of this study are to understand the daily and seasonal variation of the sap flow rate and single tree transpiration of sample trees of Pittosporum brevicalyx, the characters under different weathers, and the relations between sap flow rate and environmental factors. The results indicated that the daily mean sap flow rate of Pittosporum brevicalyx was (3.14±0.10) g H2O/(m2 s), with the rate of (5.20±0.17) g H2O/(m2 s) in daytime and (0.55±0.02) g H2O/(m2 s) in night time, a difference of as high as 9.45 times The mean sap flow rate (g H2O/(m2 s)) under different weather conditions followed the order of sunny days (5.71±0.15)＞cloudy days (1.95±0.10)＞raining days (1.65±0.10). The mean daily transpiration of single trees was (2.10±0.07) kg within the variation range of 0.09 to 8.05 kg, within which (1.94±0.06) kg, transpired in daytime and (0.16±0.01) kg in night time respectively, accounting for 92.38% and 7.62% of the whole day transpiration. The mean daily transpiration (kg/d) of single trees in different seasons followed the order of summer (3.32±0.14)＞autumn (2.18±0.12)＞spring (2.14±0.12)＞winter (0.76±0.05). A correlation analysis showed that the transpiration rate of either the whole day or the daytime and night time under all weather days was significantly and positively correlated (P＜0.01) with the air temperature, VPD and wind speed, and significantly and negatively correlated with the air humidity. Furthermore, the sap flow velocity was significantly and positively correlated with the solar radiation at the whole day and daytime, the precipitation in rain days, the volumetric soil water content at the night time of sunny days and cloudy days and at any time of rain days. The stepwise regression equations were established between mean daily sap flow rate of single trees and the environmental factors according to time scales and weather types. The results of step wise regression analysis showed that the solar radiation and volumetric soil water content in 20 cm layer soil were the major environmental factors influencing sap flow in both daytime and nighttime. The air temperature had a stronger influence on sap flow than other environment factors in both sunny days and cloudy days; while the solar radiation was the major factors influencing sap flow in rain days. The sap flow was main controlled by solar radiation in spring, autumn and winter; while by the VPD in summer. The solar radiation, air temperature and VPD were the main factors influencing the sap flow rate of trees of Pittosporum brevicalyx, and the soil water content was the main driver of the sap flow in night time.

Abstract:In order to quest the effects of Fe oxide on nitrification in soils, a acidic fluvo-aquic soil (pH 4.9) and neutral fluvo-aquic soil (pH 7.2) with low total iron were selected as materials. Indoor incubation method?was used to investigate the time-dependent kinetic of net nitrification after the two soils were amended with 0% (control), 0.5%, 1%, 3%, 5%, 10% Fe oxide by weight. The results showed that, nitrification was best fitted by a first-order kinetic model for neutral soil with less than 3% Fe oxide amendment. However, it was best fitted by a zero-order kinetic model when more than 3% Fe oxide were added. For acid soil, nitrification was best fitted by a first-order kinetic model regardless of the addition amount of Fe oxide. Net mineralization rate of the acid soil increased significantly after the addition of different amount Fe oxide, and the highest mineralization rate was found for 10% Fe oxide amendment (4.12 mg/(kg·d)), which was 7.82 times higher than unamended soil. With the increase of iron oxide addition amount, the net nitrification rate of acid soil significantly increased while the net nitrification rate of neutral soil decreased significantly. The net nitrification rates of acid soil with 3% and more Fe oxide amendment were extremely significantly higher than that of soils with less amendment. Overall, Fe oxide addition stimulated net nitrification rates in the low pH soil (pH 4.9), while the opposite occurred in the high pH soil (pH 7.2), and the greater amount wereadded, the more significant effects were observed. 3% Fe oxide amendment was the critical value that significantly influence nitrification of the acid fluvo-aquic soil and neutral fluvo-aquic soil.

Abstract:The research used the soil of Picea crassifolia forest distribution on altitude of 2 500～3 100 m in the eastern of Qilian mountains as the research object, and using the close-top tube at field sampling methods and laboratory analysis method to study on soil NH4+-N and NO3--N net mineralization rate and net N mineralization and mineralization rate, aimed to explore the relationship between the soil net nitrogen mineralization rate and temperature, precipitation, soil nutrient. With a view to improve productivity of Picea crassifolia forest in Qilian Mountain and guide the Picea crassifolia forest ecosystems of sustainable development and management to provide basal reference materials. The results were summarized as follows: (1) There was different significantly about net mineralization rate of soil nitrate with the increase of altitude. The net ammonia nitrogen mineralization rate, soil net nitrogen mineralization rate and mineralization rate as well. Soil net nitrogen mineralization and the mineralization rate showed the "W" word in the altitude gradient, and changes of the same with nitrate net mineralization rate with increasing of altitude, contrary to the law of nitrogen net mineralization rate. At an altitude of 2 800 m, net nitrate nitrogen mineralization rate and amount of soil net nitrogen mineralization and the mineralization rate achieves had the maximum value, which was 0.372, 160.3, 0.44 mg/(kg. d), respectively, the net ammonia nitrogen mineralization rate had minimum value (0.067 mg/(kg. d)); the lowest value appeared at an altitude of 2 900 m, which was 0.155, 94.7, 0.26 mg/(kg. d), respectively. At an altitude of 3 100 m, the net mineralization rate of ammonia nitrogen achieved the maximum 0.13 mg/(kg. d). (2)Regression analysis showed that soil net nitrogen mineralization were very significantly negative correlation with annual average temperature (P＜0.01), R2=0.717 3; which were very significantly positive correlation with annual rainfall (P＜0.01), R2=0.383 5, concluded that climate change affecting the quantity of soil net nitrogen mineralization degree was: the average annual temperature＞annual precipitation. (3) Regression analysis showed that soil net nitrogen mineralization were extremely significant positive correlation with the soil total nitrogen, organic matter, water content and pH value (P＜0.01), the R2 were 0.910 1, 0.906 0, 0.842 8, 0.797 9, respectively; which were very significant negative correlation with the soil bulk density (P＜0.01), R2=0.222 4. By a R2 value size the soil nutrient affecting the quantity of soil net nitrogen mineralization degree was: soil total nitrogen＞soil organic matter＞soil moisture＞soil pH＞soil bulk density.

Abstract:Rainfall was partitioned into three parts through the vegetable canopy: Throughfall, stemflow and interception. This process played a determining role in water balance for forest stands and in regulating processes of this mountainous region. In present study, the experiment was carried out in Pailugou watershed in Qilian Mountains, in the arid region of Northwest China. In a 96-year-old Picea crassifolia forest stand, throughfall, stemflow and canopy interception of 34 rain events were observed from May 1 to September 31, 2015. Meanwhile, the related meteorological factors, including air temperature (T), air relative humidity (Rh) and precipitation (P) were simultaneously monitored by an automatic meteorological station in the outside forest. Then, we analyzed the characteristics of rainfall canopy partitioning and their influence factors. The results showed that: (1)During the total observation period, the total throughfall, stemflow and interception of Picea crassifolia forest were 275.9, 1.8 and 90.0 mm, and accounted for 75.04%, 0.48% and 24.48% of the total atmospheric precipitation, respectively. Meanwhile, their ratios varied significantly under different rainfall grades. (2)The three parts of rainfall canopy partitioning were significantly correlated with rainfall, rainfall duration, maximum rainfall intensity in 10 minutes and relative air humidity. With the increase of rainfall and rainfall duration, throughfall and stemflow would constantly increase and their ratios would become more and more stable. (3)The critical rainfall amounts for the occurrence of throughfall and stemflow were 0.8 mm and 9.6 mm respectively. Therefore, we concluded that meteorological factors were the important factors of rainfall canopy partitioning.

Abstract:Water is not only an important factor limiting the survival and growth of plants, but also a factor influencing the distribution and quantity of vegetation in arid areas. Haloxylon ammodendron is a dominant plant species in the Gurbantünggüt Desert. Researching the water use pattern and seasonal changes is vital for understanding plant adaptation to environmental changes in the arid zone. In our study, the oxygen sable isotope ratios (δ18O) of xylem water and soil water in different soil layers (0—400 cm) were measured, and the water resource of young Haloxylon ammodendron in spring and summer were analyzed with direct comparison method, Iso-Source model and the mean depth of water uptake model. The results show that: (1) surface soil moisture (0—70 cm) in May was significantly higher than the surface soil moisture content in July, the difference of soil moisture content in 70—400 cm soil layer is not significant in Spring and Summer. (2) The δ18O values of surface soil water changed widely. In May, the δ18O value of surface soil water was varied and it’s significantly more negative compared with July. In July, the δ18O value of soil water gradually decreases with depth increases. (3) The mainly water resource of young Haloxylon ammodendron is the soil water in 0—50 cm soil layer in May, the use ratio is up to 67.5%. However, in July, the contribution of surface soil water decreased drastically while that deep soil water increased rapidly, the mainly water resource is the soil water in 250—400 cm soil layer in July, the use ratio is up to 94.2%.

Abstract:In order to reveal the effects of initial soil moisture content on the soil water infiltration property under single point of freedom muddy water film hole irrigation, the test was carried out under different initial soil moisture content. The test studied on the influence of initial soil moisture content on the infiltration characteristics，reduced infiltration characteristics and distribution of soil moisture content of single point of freedom muddy water film hole irrigation, and built film hole irrigation free irrigation model with cumulative time and permeability reducing model. The test results indicated that the infiltration capacity of per unit film hole area had decreasing trend in the same time as the increasing of the initial moisture content of the soil and the initial moisture content of 4.96%, 7.43%, 10.07% and 12.40% decreased by 19%, 33%, 45% and 56%, respectively compared with the dry conditions test. While the permeability reducing affection had increasing trend under the fixed sand percentage of muddy water and the film hole diameter. Near and far away the film hole, the gradient of water content changed in a large and it's about 2%/cm. Less change of the gradient of water content was in the middle part and it's about 0.65%/cm.

Abstract:In order to explore the influence of rainfall on infiltration characteristics and water holding capacity of engineering accumulation，laboratory basic soil physical properties analysis and field double ring infiltration methods were used to study the changes of infiltration characteristics and water holding capacity of engineering accumulation in different rainfall conditions and its influencing factors. The results showed that soil bulk density and soil porosity of engineering accumulation had significant differences in different rainfall conditions and slope positions. In different rainfall conditions, the soil bulk density of engineering accumulation of lower of slope from high to low were: Drought (Ⅰ)＞light rain (Ⅱ)＞moderate rain (Ⅲ)＞heavy rain (Ⅳ). Total porosity, capillary porosity, non-capillary porosity in different slope positions from high to low were: Lower＞middle＞top. In different rainfall conditions, the initial infiltration rate from high to low were: Drought (Ⅰ)＞light rain (Ⅱ)＞heavy rain (Ⅳ)＞moderate rain (Ⅲ), its size in order to 8.91, 5.52, 3.96, 3.25 mm/min. The stable infiltration rate from high to low were: Drought (Ⅰ)＞moderate rain (Ⅲ)＞light rain (Ⅱ)＞heavy rain (Ⅳ), its size in order to 4.40，1.45，1.32，0.53 mm/min. In different rainfall conditions, the maximal effective capacity of engineering accumulation of lower of slope from high to low were: Heavy rain (Ⅳ)＞light rain (Ⅱ)＞drought (Ⅰ)＞moderate rain (Ⅲ), its size in order to 469.03，402.48，378.11，321.88 t/hm2. In different slope positions of engineering accumulation, the field capacity of moderate rain condition was largest. The water-holding capacity of engineering accumulation had a significant positive correlation with total porosity, capillary porosity, non-capillary porosity and infiltration characteristics, while it had a significant negative correlation with soil bulk density. The results could provide important scientific evidence basis for the prevention and control of soil and water loss of engineering accumulation.

Abstract:To explore the spatial distribution of total sulfur (TS) contents in plant-soil system of tidal marshes in the Shanyutan of the Min River estuary, from the land to the sea, two transects (A transect, away from the main tidal channels with no flooding as the tide ebbs; B transect, near the main tidal channels with flooding as the tide ebbs) with different flooding regimes were laid and three typical plants (Cyperusmalaccensis, Spartinaalterniflora and Cyperuscompressus ) of the marsh were studied in July 2015. Results showed that long-term flooding regimes caused same type of marsh top soil TS contents of B transect less than A transect, but also enhanced horizontal variability of 0-40 cm soil TS contents among different types marsh and vertical variability among the same ones. Although the long-term flooding regimes reduced the root TS contents and accumulation coefficient of three kinds of marsh plants in B transect, but increased above-ground organs and standing litter TS contents and accumulation coefficient, also increased the percentages of sulfur distribution in above-ground organs. Comparative studies had shown that the TS contents in soils and plants of the three typical marshes in the Min River estuary were in a high level across the country, and the values were much higher than those in the freshwater marshes of Sanjiang Plain, the salt marshes of Xianghai and the marshes in the Haihe River Basin, but slightly lower than those in mangrove swamps. The study found that flooding conditions and soil moisture were the dominant factors resulting in the differences of TS contents in soils of the same marsh located in A and B transects. Flooding conditions also altered the distribution patterns of TS content in different plants and plants could adjust their S absorption and accumulation traits to adapt to the flooding environment.

Abstract:In order to study the adsorption behavior of lead in sediment and soil, the adsorption of Pb adsorption in sediment and soil were investigated by batch equilibrium studies according to OECD guideline 106, and the influence of the pH, organic matter and N, P concentration on adsorption process were also discussed in this study. The results showed that the adsorption isotherm of Pb was well fitted with the Temkin equation in the soil, the correlation constant were 0.925; the adsorption isotherm of Pb was well fitted with the Freundlich equation in the soil, the correlation constant were 0.971. Study showed that, Pb under the adsorption condition of 15, 25 and 35℃, with the increase of temperature, the adsorption of Pb in sediment and soil would be strengthened, ΔG＜0, ΔH＞0, revealed that the adsorption of Pb in the sediment and soil was a spontaneously endothermic process. Study showed that, under the pH condition of 3～11, the Pb adsorption quantity increased with the increase of pH, after the first increased and then to be gentled. When the pH was equal to 5, the adsorption effect was best. After removal of the organic matter the adsorption amount of Pb in sediment and soil decreased by 121.6, 87.4 mg/kg, respectively. With the increase of N, P, the adsorption amount of Pb in sediment and soil decreased, which might be due to with the carrying of N, P, the K+ was added, and it had a competitive adsorption of Pb led to reducing adsorption capacity of Pb.

Abstract:In order to study the relationships between soil settlement and soil bulk density and surface roughness under natural conditions, this paper used ruler, ring sampler and a chain to determine soil settlement, soil bulk density, surface roughness degree of different soil textures in turned over tillage and ridge culture under natural conditions and analyzed soil bulk density, the changes of surface roughness degree and the relationship between soil settlement quantity and soil bulk density, surface roughness degree under different soil textures with tillage measures were not homogeneous soil subsidence, and constructed the soil bulk density and surface roughness prediction formula. The results showed that：（1）With rainfall energy accumulated, the soil settlement decreased under certain rainfall energy conditions. And the soil settlement under ridge tillage were not less than the soil settlement under flatten culture.（2）Soil bulk density increased after reaching to natural soil bulk density with different levels.（3）Surface roughness under the condition of ridge tillage decreased. And the surface roughness of loam soil was not always less than the surface roughness of sandy soil.（4）A good exponential relationship between soil settlement and variation of soil bulk density, the correlation coefficient more than 0.9. Soil settlement and the variation of surface roughness fitted power function relationship, where the correlation of sand than loam was higher, the correlation coefficients were 0.993, 0.936 respectively. These research results offered a reference for prediction soil compaction degree, surface smooth degree under natural conditions and tillage.

Abstract:Selecting the seven small catchments in Jiaodong Peninsula as the study area, the gully system was extracted using the SA model, and the fractal dimensions of the gully system were calculated by boxcounting method. The gully fractal characteristics and the coupling between the fractal dimensions of gully lengths and terrain parameters, and the land use types were analyzed to determine the characteristics of the gully evolution. The results showed that: (1) The fractal dimension of gully length in Mountain Watershed was larger than that in farming area, indicating the fractal feature of gully length was mainly controlled by the geological structure of the basin. (2) The gully-head density, ravine density, surface roughness, profile curvature, and terrain average gradient were found to have significant positive correlation with fractal dimension of gully length in the study catchments, while correlation between the area of catchment and the length of gully was insignificant. (3) There was significant positive correlation between the fractal dimension of gully length and the gully-head density, ravine density, with the correlation coefficients of 0.982 4 and 0.975 3, respectively, indicating that gully-head density and ravine density were the important parameters of the fractal characteristic of the valleys, as a simple indicator for estimating regional gully fractal characteristics and the fractal dimension. (4) There was significant positive correlation between the fractal dimension of gully length and the forest-grassland ratio and hilly area ratio, with the correlation coefficients of 0.893 and -0.919 8, respectively, indicating that the characteristics of the gully evolution was closely related to the large topographic contour under the control of geological structure, while little relation to the micro topography formed by the process of human activity.

Abstract:The distribution characteristics of topsoil particle size can reflect the regional characteristics of the district environment，research on the internal topsoil particle size distribution of small watershed in wind water erosion region could provide a theoretical basis for exploring the mechanism of water and soil erosion. By field sampling and laboratory determination of surface space，study on surface soil particle size distribution characteristics and wind-erosion possibilities of Dong Liu Gou basin which located in the area of wind-water erosion. The results were as follows：soil particle size of Dong Liu Gou watershed was mainly concentrated in the fine sand (50～250μm)，volume fraction between 56.59%～86.65%，belonging to aeolian sandy soil .There was a significant difference between the state of the size among different land use types. The Mz of grassland，farmland and shrub were 77.60μm，81.66μm and 87.85μm respectively，in which the particle size distribution was small. While the Mz of sandy land and river channel was large，which were 126.36μm and 151.80μm respectively in/with coarse particle size. Most of the topsoil particle size showed a positive bias and narrow peaks，particle distribution is more concentrated. The rough phenomenon of the topsoil grain size has been shown obvious from upstream to middle reaches，specific performances：the Mz of the land use in the upper reaches was smaller than that in the middle and lower reaches except the river channel(p＜0.05). While in the middle reaches，there was not significant difference between sandy soil and other land types in Mz except the grassland and river channel. After analysis the possibility of wind erosion of the topsoil in the watershed，we found that the erodible particles content significantly increased from upstream to the middle reaches，which were increased by 44.4%，54.23%，48.84%，33.76% in grassland，cropland，shrub，river，respectively. The conclusion showed that the middle reaches was the region where the topsoil particle size distribution was most complex and the wind erosion was most intense，and also and also the major area where wind and water erosion interacted.

Abstract:This paper focused on the typically collapsing alluvial fan in Wuhua County, Guangdong Province，collected 64 soil samples and points location information by GPS RTK from the top to the edge of the alluvial fan to do the analysis of physical and chemical property. Through the combination of fractal theory, regression analysis and geo-statistics method, the paper aimed to expound the soil fractal dimension characteristic and spatial variability, and the correlation with soil particle composition and nutrient content in collapsing alluvial fan. The result indicated that there were obvious differentiation characteristics in soil particle composition and nutrient content, and presented certain regularity with the spatial distribution characteristics of fractal dimension. From the top to the edge of the alluvial fan, the proportion content of soil silt and clay and nutrient content increased gradually, and fractal dimension was a positive correlation with them. But the proportion content of sand decreased gradually, and presented a negative correlation with fractal dimension. Among them, clay content was the most influential factor to fractal dimension, and the coefficient correlation was up to 0.969.The results proved that the fractal dimension could be used as an important index of soil texture and fertility.

Abstract:To explore effects of liquorice(Glycyrrhiza Uralensis) plantation on soil erosion, texture and contents of organic carbon(OC) and total nitrogen(TN) through measuring vegetation coverage, height above-ground biomass and topsoil(0-5 cm) erosion, texture, nutrient conservation under cover, analysis was done of the liquorice vegetation for characteristic indices and of the topsoil texture and nutrients. Results showed that with the liquorice vegetation growing on, coverage, height and biomass of the vegetation, and silt+clay, very fine sands, OC and TN in the topsoil all significantly increased, while wind erosion significantly decreased(P＜0.05). Correlation analysis indicated that characteristic indices were significantly and positively related to soil silt+clay, very fine sands, OC and TN contents(P＜0.01). Regression analysis demonstrated that for every 1g of increase in biomass, the content silt+clay, OC and TN in topsoil increased 0.048 9 %, 0.012 g/kg and 0.001 1 g/kg; for every 1% of increase in topsoil silt+clay, the content of OC and TN increased 0.220 3 g/kg and 0.018 5 g/kg, respectively. Obviously, the adoption of practice of planting liquorice on farmland of wind erosion of Northwest China, may reduce wind erosion of the surface soil, and increase the amount of fine particulate matter and hence content of OC and TN, and soil fertility could be recovered and improved.

Abstract:In order to explore the biological effect of monosodium glutamate wastewater on forest soil and determine the appropriate application level of monosodium glutamate wastewater and inorganic fertilizer for improving poplar growth, a pot experiment including five treatments, i.e. CK (neither urea nor monosodium glutamate wastewater was applied), N100 (100% of nitrogen was provided by urea), M10N90 (10% and 90% of nitrogen were provided by monosodium glutamate wastewater and urea, respectively), M30N70 (30% and 70% of nitrogen were provided by monosodium glutamate wastewater and urea, respectively) and M50N50 (50% and 50% of nitrogen were provided by monosodium glutamate wastewater and urea, respectively) was performed. The present study was conducted to determine the effects of different treatments on active organic carbon, carbon pool management index (CPMI), microbial respiration and metabolic quotient in soil, as well as growth of poplar seedlings. Results showed that in comparison with N100 treatment, monosodium glutamate wastewater application significantly increased the contents of active organic carbon, mid-active organic carbon and highly active organic carbon. The active organic carbon content and CPMI in M30N70 treatment were obviously higher than other treatments, increasing 34.78% and 42.96 compared with N100 treatment, respectively. The M30N70 treatment also significantly increased the contents of microbial biomass carbon and microbial biomass nitrogen. In the meantime, the microbial respiration was evidently enhanced by the use of M30N70 treatment, while the metabolic quotient was decreased, increasing 81.13%, 35.21%, 17.07% and 5.49% in microbial respiration over the treatments of CK, N100, M10N90 and M50N50, respectively. And the metabolic quotient was reduced by 9.16%, 10.37%, 6.98% and 5.80%, respectively. Additionally, the ground diameter and plant height in M30N70 treatment also reached the maximum and had significant differences with other treatments. However, in M10N90 and M50N50 treatments, less effect on micro-domain environment characteristics and growth was observed than that in M30N70 treatment. Correlation analysis revealed that ground diameter and plant height were significantly or extremely significantly correlated with different degree of soil active organic carbon, carbon pool management index (CPMI) and microbial activity, indicating close inner link among every indicator. These results suggested that monosodium glutamate wastewater combined with inorganic fertilizer, especially M30N70 treatment, was beneficial to increase the active organic carbon content, enhance the microbial activity in soil and promote growth of poplar seedlings.

Abstract:One-year-old Robinia pseudoacacia saplings were subjected to 70% of field capacity (control) and progressive drought stress (treatment) to study the effects of drought stress on non-structural carbohydrates (NSCs) of R. pseudoacacia saplings at the end of the growing season. While leaf biomass, stomatal conductance and net photosynthetic rates of saplings under control generally exhibited no significant differences throughout the experiment (P＜0.05), those under treatment decreased with the intensification of drought stress (P＜0.01). Soluble sugar concentrations and the ratios of soluble sugars to starch in different tissues under treatment all increased with drought progression, but were significantly higher than those under control (P＜0.05). Contrarily, starch and NSC concentrations in each tissue under treatment all decreased with drought progression (P＜0.05). Except NSC in leaves and fine roots, starch and NSC concentrations under treatment were all lower than those under control (P＜0.05). NSC concentrations in branches, stems and coarse roots were 96.6%, 70.5%, and 78.2% of those under control, respectively. At the whole sapling level, NSC concentrations under treatment decreased throughout the experiment, and were significantly lower than those under control (P＜0.05), and were 84.0%, 79.0%, 76.3% and 67.5% of those under control on the 6th, 9th, 12th and 15th days, respectively. Soluble sugar, starch and NSC concentrations and the ratios of soluble sugars to starch in different sapling tissues, except NSC concentrations in branches and fine roots, and NSC concentrations at the whole sapling level were all significantly correlated with soil water content, leaf biomass, stomatal conductance and net photosynthetic rates. Our results suggested that the premature defoliation and decrease of photosynthetic rate of R. pseudoacacia saplings resulted from drought stress at the end of the growing season could facilitate the transformation of starch to soluble sugars and then decrease the accumulation of starch, as a result, would induce the premature consuming of NSC, which would mainly occur to stems and coarse roots.

Abstract:The arbuscular mycorrhiza fungi (AMF) was researched as an object in karst soil of different vegetation restoration stages (tree, bush and herb) of three typical karst sites (Huajiang, Zhijin and Huaxi), which were located in Guizhou Province, China. Some indexes such as species abundance, spore density, relative isolation frequency，important value，species evenness index and sample Shannon-Wiener diversity index were calculated after morphological identification, in order to explore the composition features and AMF species diversity in vegetation restoring process. The results showed as follows: The experimental soil totally contained 68 species of 10 genera, 8 families and 4 orders, and Glomus is the biggest genus by 35 species, and the second was Acaulospora (17 species), when Gigspora, Paraglomus and Archaeospora only have 1 species respectively in this study. Specially, Glomus lamellosum had biggest species abundance, relative isolation frequency and important value in all AMF species, which it was as an dominant species in three sampling sites. At the AMF species level, the abundance presented Tree＞Bush＞Herb in Huajiang,Bush＞Herb＞Tree in Zhijing, Bush＞Tree＞Herb in Huaxi. The evenness index and Shannon-wiener index of AMF species in different stages presented Tree＞Bush＞Herb in Huajiang and Zhijing sites, however the Shannon-wiener index in Huaxi site significantly higher than Tree and shrub stages. We suggested that the differences of heterogeneous conditions may affect on composition and diversity of AMF species.

Abstract:Observation was performed during the period from April, 2015 to August, 2015 of N2O emissions from long-term irrigation field under different irrigation managements: Drip irrigation (D30), subsurface irrigation (S30) and furrow irrigation (G30) during the tomato season, using the static chamber-gas chromatograph method and Real-time quantitative polymerase chain reaction (Real-time PCR) technique. In order to find the relationship between the N2O emissions and impact factors, soil temperature, soil moisture, soil mineral nitrogen and soil denitrifying bacteria were observed in the meanwhile, which conducted by the combination of field experiments and laboratory analysis. Results showed that N2O emission peaks would obviously occur within 1～8 days after each irrigation. In tomato growth season, soil N2O mean fluxes was highest under furrow irrigation treatment, 52.74% higher than drip irrigation treatment and 50.82% higher than subsurface irrigation treatment; compared with furrow irrigation, the soil N2O total fluxes significantly decreased by 54.31% and 53.30%. Soil N2O emissions were very significant positive correlation with soil moisture (P＜0.01) and nitrate nitrogen concentration (P＜0.05). There was no consistent correlation between soil N2O fluxes and soil temperature, soil ammonium nitrogen content. Abundances of soil denitrifying bacteria had significant difference under different irrigation managements, followed by G30＞S30＞D30. Abundances of soil denitrifying bacteria nosZ were related to the soil N2O emissions (P＜0.01). In conclusion, soil moisture, nitrate nitrogen, denitrifying bacteria nosZ were important factors that affected the soil N2O emissions; choosing drip irrigation and subsurface irrigation could effectively reduce N2O emissions from the greenhouse soil.

Abstract:Based on a long-term experiment during 1979—2014 with various fertilizations in black soil of northeast China, the objective of this study was to research evolution characteristics of soil organic carbon (SOC) content, carbon sequestration and its cooperation with carbon input. The results showed that: Compared to the initial soil condition, SOC content in long-term chemical fertilizers application (N, NP, NPK, N2) decreased by 11.6%～16.1%, while the SOC content in long-term horse manure application significantly increased. Chemical fertilizers application plus horse manure with conventional application rates (MNP, MNPK) or doubleness (M2N2, M2N2P2) could increase SOC content 6.5%, 8.4%, 7.7% and 11.6%, respectively. The carbon sequestration in the treatment of non-fertilization (CK) and chemical fertilizers application appeared deficit, ranged from 3.5～6.1 t/hm2. In contrast, SOC storage in the treatment of chemical fertilizers application plus horse manure showed surplus, and the maximum value was 1.9 t/hm2 (M2N2P2). There was a significantly positive linear correlation between annual average organic C input and C sequestration efficiency, which showed that black soil still had potential carbon sequestration. The calculated annual transform rate of input carbon was about 34.1%, and the least carbon input for maintaining the initial organic carbon level was about 1.416 t/hm2. Therefore, increasing carbon input (manure) was a key to improve carbon sequestration in black soil region.

Abstract:Taking the mild burned area of Great Xing’an Mountains as research objects, the impact of burning on the soil organic carbon fractions in Pinus sylvestris var. mongolica natural forest was investigated through a comparative study. The results showed that the mild burning changed the composition and content of the soil organic carbon of Pinus sylvestris var. mongolica natural forest. After mild burning, the content of soil organic carbon, readily oxidizable carbon and particulate organic carbon decreased by 8.52 g/kg, 1.36 g/kg and 5.85 g/kg respectively at 0—5 cm soil layer, which decreased by 4.78 g/kg, 0.19 g/kg and 2.98 g/kg respectively at 5—10 cm soil layer. The difference reached a significant level between burned and unburned natural forest （P＜0.05）. The black carbon content at soil surface significantly increased after mild burning. The black carbon content of burned area at 0—5 cm soil layer increased by 9.95 g/kg, and the difference reached a significant level with unburned natural forest （P＜0.05）. In 0—5 cm and 5—10 cm soil layer, the proportion of black carbon to soil organic carbon in burned area increased by 25.4% and 6.12% respectively, the proportion of readily oxidizable organic carbon to soil organic carbon decreased by 1.49% and 0.65% respectively, the difference between burned area and unburned natural forest reached a significant level（P＜0.05）. Mild burning had little effect on the proportion of particulate organic carbon to soil organic carbon. Regression analysis showed that the soil organic carbon displayed an extremely significant linear correlation with soil organic carbon fractions both mild burned and unburned natural forest（P＜0.01）.

Abstract:In order to reveal the effect of desertification on soil active organic carbon fractions in Zoige alpine-cold grassland, the soil total organic carbon (TOC), dissolved organic carbon (DOC), easily oxidized organic carbon (EOC) and microbial biomass carbon (MBC) contents during the process of desertification were analyzed by space-for-time substitution. The results showed that the contents of SOC and its active fractions in 0—60 cm depth in alpine-cold grassland significantly decreased during desertification, from potential desertification stage to severe desertification stage, the TOC, DOC, EOC and MBC decreased by 74.76%, 80.24%, 76.02% and 83.24%, respectively. Compared with TOC, the loss of soil active organic carbon fractions were more obvious with the biggest decline observed in MBC, soil organic carbon contents in different degrees of desertification grassland and this variation showed a trend of decrease with the increase of soil depth, TOC, DOC, EOC and MBC decreased most significantly in the 0—20 cm soil layer among all layers within 0—60 cm. In the process of grassland desertification, TOC, DOC, EOC and MBC were highly significant correlation with each other (P＜0.01).

Abstract:In order to investigate the influence of different cementing materials on the stability of macro-aggregate, this study investigated the content and types of organic and inorganic cementation material and macro-aggregate stability in the 0—100 cm soil profile of Quercus wutaishansea community in the Ziwuling forest region by field investigation and laboratory test, and analyzed the relationships between distribution of cementing material and its effect on macro-aggregate stability. The results showed: (1) Organic carbon and calcium carbonate showed completely opposite distribution in profile, and the content of organic carbon decreased with soil depth, the content of organic carbon in 0—20 cm soil layer was significantly higher than that in 20—100 cm soil layers. The content of calcium carbonate increased with soil depth, and the content in the 20—100 cm was significantly higher than 0—20 cm soil layers. (2) The aggregate stability was decreasing with the soil depth. The 20—70 cm layer had the most dramatic changes (compared with the 0—20 cm soil layers, the destruction rate increased by 581.00%). The proportion of aggregates destruction of 40—100 cm soil layer was 7.25 times larger than that of 0—20 cm soil layer, so the aggregate stability of surface was significantly higher than the bottom. While the clay content increased gradually with the increase of soil depth, but the change was not obvious. (3) The improvement of macro-aggregate stability mainly depended on the content of soil organic carbon. Mineral-associated organic carbon had the most direct effect on the stability of macro-aggregates in the organic carbon fractions. The results of this study revealed the distribution characteristics of main cementing materials and made clear that the mineral bound organic carbon was the most powerful cementing material which had a direct impact on the stability of the macro-aggregate of the loess. It provided a scientific basis for the cultivation of fine aggregate structure.

Abstract:By taking clay soil in Binzhou as research objects, pot experiments were conducted in order to evaluate the effects of nutritive soil amendments on compacted soil. Soil bulk density, soil specific gravity, porosity and soil aggregate were investigated, and stability of soil aggregate were calculated to study the effects of NSA on characteristics and fractal dimension of clay soil aggregates. The result showed that NSA could decrease pH, soil bulk density and soil specific gravity, and increase porosity. NSA significantly increased the content of 0.5～1 mm and 0.25～0.5 mm soil aggregate, while significantly reduced the content of ＜0.05 mm soil aggregate. The amount of water-stable macroaggregates (R0.25) of 0.5% NSA and 1.0% NSA were significantly higher than the control (CK), with an increase of 67.14 % and 141.58%. With soil amendments application, larger soil aggregates were formed to improve soil condition. Mean weight diameter (MWD), geometric mean diameter (GMD) and fractal dimension (D) were significantly higher than the control, and the soil unstable aggregate index (ELT) decreased with amount of NSA which was the lowest in T3 treatment. The results indicated that applying NSA could improve surface soil structures through increasing water-stable macroaggregates contents and stability. This research provides academic and instructive bases for developing soil amendments.

Abstract:In order to explore the effects of different restoration approaches on soil aggregates’ formation and it’s cycle carbon of severely burned area in Greater Xing’an Mountains, the artificial restoration (Larix gmelini and Pinus sylvestris var. mongolica) and the natural regeneration of forest in Greater Xing’an Mountains after the severely burned in 1987 respectively were chosen as the research object and analyzed the distribution features of organic carbon, microbial biomass carbon and K2SO4-extractable carbon in soil aggregates under different restoration approaches. The results showed that: (1) There were significant difference (P＜0.05) for the contents of organic carbon, microbial biomass carbon and K2SO4-extractable carbon in soil aggregates among different forest types, which the characteristics were Larix gmelini plantation＞natural secondary forest＞Pinus sylvestris var. mongolica plantation. (2) Under different vegetation restorations, soil organic carbon and microbial biomass carbon presented an increasing trend along with increasing of particle size of aggregate, and the large aggregates were significant higher amounts of both the soil organic carbon and microbial biomass carbon than the micro aggregates（P＜0.05）, the K2SO4-extractable carbon mainly distributed in the 1~0.5 mm particle size and larger size aggregate. (3) The organic carbon and microbial biomass carbon in soil aggregates mainly distributed in soil surface layer (0—5 cm), which the contents decreased with the increase of soil depth. Except ＞2 mm and 2～1 mm aggregates, the contents of K2SO4-extractable carbon in soil aggregates presented a decreasing trend along with the increase of soil depth. (4) Microbial biomass carbon had significant positive correlations (P＜0.01) with soil organic carbon and K2SO4-extractable carbon, revealing that microbial biomass carbon had close relationship with soil organic carbon and K2SO4-extractable carbon.

Abstract:To study the distribution and growth trait of Vitex negundo shrub in the Loess region, three typical regions: the Loess tableland beam gully region, the broken Loess tableland beam gully region and the rocky mountain gully region were selected as the experiment sites. The growth indexes and its correlation with climate factors were determined by using the field survey and the observation of fixed position. The results showed that all of growth indexes of Vitex negundo in the three regions were in the following pattern in a significant level: The rocky mountain gully region＞the Loess tableland beam gully region＞the broken Loess tableland beam gully region. The shrub biomasses in the three regions were 2.66, 1.78 and 1.07 kg/plant, respectively. The branches number in the rocky mountain gully region was 43.8% higher than that in the Loess tableland beam gully region, and 61.7% higher than that in the broken Loess tableland beam gully region. The correlation analysis showed that all of growth indexes responded to the climate changes in the same way, and Vitex negundo shrub had stronger competition ability compared with the annual and perennial herbs in the shrub community. Therefore, Vitex negundo