Abstract:In order to study the dynamic characteristics of overland flow under the combined effects of rigid vegetation coverage and surface roughness, the hydraulic flume experiment was carried out. The experiment included 10 discharges (0.33～1.95 m3/h), five different coverage levels (0, 0.5%, 1%, 1.5%, 2%), four different surface roughness levels (Ks=0.01, 0.18, 0.25, 0.38 mm) and one angle level (15°). The results show that: (1) The flow velocity fluctuated from 0.06 to 0.59 m/s, the average flow velocity was negatively correlated with the vegetation coverage and the surface roughness. When the vegetation coverage increased, the average flow velocity which increased with the discharge would reduce the level of increase. The correction factor (α) coefficient had a positive correlation with the vegetation coverage, and a negative correlation with the surface roughness. (2) The Reynolds number ranged 153~910, the flow pattern was mainly concentrated in the transition zone and the virtual laminar zone, and the flow regime was mainly concentrated in the rapids zone. With the increases of vegetation coverage and surface roughness, the flow pattern gradually extended to the slack zone (Fr＜1). (3) The total flow resistance coefficient was exponential with Reynolds number, and positively correlated with surface roughness and vegetation coverage. (4) The influence index of resistance showed that when the flow rate was less than 1.05 m3/h, the influence of surface roughness was greater than the vegetation coverage, otherwise the vegetation coverage became into the prominence. The total resistance was significantly different with the linear superposition value of grain resistance and surface object resistance through t-test, indicating that the linear superposition could not be used to calculate the total resistance, when the grain resistance and surface object resistance existed.

Abstract:In order to study the hydrodynamic mechanism of soil erosion on earth-rock mixed colluvial deposit slopes, scouring tests were conducted in the laboratory. In the tests, four the gravel contents (mass content) (0, 20%, 40% and 60%), four flows (2, 4, 8 and 16 L/min) and four slope gradients (10°, 20°, 30° and 40°) were set. Results showed the following: (1) soil erosion rate decreased with the increasing of gravel content when the slope gradient or flow was low, while when the flow or slope gradient increased, erosion rate first decreased and then increased with the increasing of gravel content; erosion rates of different earth-rock mixtures could be expressed by power function of slope and flow. (2) Flow shear stress, stream power and unit stream power were all linearly related to erosion rate, while by comparison, shear stress and stream power were the optimal hydrodynamic parameters to simulate the erosion process on the earth-rock mixed colluvial deposit slopes. (3) Soil erodibility parameter and critical erosion force both increased with the increasing of gravel content. These results of this study could provide a reference for further understanding the erosion mechanism of colluvial deposit.

Abstract:In this study, simulated rainfall was conducted to mainly investigate and analyze organic carbon content of sediment and its dynamic change during the rainfall on the outdoor runoff plot under random conditions. The sediment organic carbon content, which was significantly higher than that of the soil organic carbon (p＜0.01), decreased gradually during the early stage of the rainfall, then tended to be stable in the later stage. The organic carbon was obviously enriched in sediment, and the maximum of enrichment ratio was 1.780. The content and enrichment ratio of organic carbon in sediment decreased obviously with the increasing of erosion rate, and tended to be stable. The loss process of sediment organic carbon showed a unimodal distribution during the rainfall, which increased first with the rainfall, then decreased after reaching the maximum value, and finally tended to quasi stable. There was a significant linear relationship between soil organic carbon loss and soil erosion amount (p＜0.01), indicating that soil erosion amount determined the organic carbon loss during the erosion process, so accurate estimation of soil erosion intensity was the basis of estimating organic carbon loss on the slope.

Abstract:Based on the combination of baseflow nutrient load recession analysis and meteorological factors, and digital filtering technology was used, a recursive filter loading separation algorithm (RFLSA) based on the daily load fraction of baseflow nutrient was proposed and established. Quantitative analysis of the total nitrogen (TN) and total phosphorus (TP) loss of baseflow was carried out in the Changle River Basin of Zhejiang, Shengzhou. The results showed that The R2 of baseflow TN daily load simulation was 0.86, and the simulation efficiency coefficient NSE was 0.72, and the above parameters for baseflow TP were 0.65 and 0.63. The mean annual TN and TP loss through baseflow in the studied watershed from 2003 to 2012 were 1 317.6 t (15.25 kg/hm2) and 51.8 t (0.60 kg/hm2), respectively, and accounted for 61.82% and 56.92% of the TN and TP loss in annual total runoff. Along with the increasing of precipitation during 2003 to 2012, the baseflow TN and TP losses showed a significant upward trend, and has become an important pollution source of non-point source pollution of rivers.

Abstract:Soil phosphorus loss is one of the sources of agricultural non-point source pollution. In the study, the characteristics of total phosphorus loss and the effects of vegetation coverage, fertilization and slope length on total phosphorus loss were examined. The red soil of slope land in hilly area of Zhejiang Province was studied with different vegetation coverages (0, 15%, 30%, 45%, 60%, 75% and 90%) and slope lengths (1, 2, 3, 4 and 5 m) and fertilization treatments (CK, CF and OF), and the experiment was designed under simulated rainfall condition of 30 min, rainfall intensity of 120 mm/h and fixed slope of 20°. The main conclusions were showed as follows: (1) In the condition of different fertilization treatments and slope lengths, total phosphorus loss in per unit projected area decreased with the increase of vegetation coverage. The decreasing trend on the 1 m slope length was not obvious, while the trend on the 5 m slope length was fairly obvious. Total phosphorus loss in per unit projected area was the least when the vegetation coverage was 90%, and the maximum occurred on bare land. (2) In the condition of different fertilization treatments and the same vegetation coverage, the increment of total phosphorus loss between adjacent slopes was the lowest at 3～2 m and the highest at 4～3 m. The results showed that the critical slope length was 4 m and the optimal slope length was 3 m. (3) In the condition of different fertilization treatments and slope length, eroded phase phosphorus accounted for 30.24%～94.61% of total phosphorus output, and the proportion were all higher than 50% except for the 1 m slope length, indicating that erosive phosphorus were the main form of total phosphorus loss. (4) In no fertilization condition, the ratio of erosive phosphorus to total phosphorus output was higher than that treated with inorganic fertilization or organic fertilization. Compared with the application of inorganic fertilizer, the ratio of erosional phase to total phosphorus output was higher under the condition of organic fertilizer.

Abstract:In order to provide scientific basis for rational fertilization, a field experiment was conducted to evaluate the effects of different fertilization methods on runoff nitrogen (N) and phosphorus (P) loss in double cropping paddy field. Six treatments were designed: without N (WN), chemical fertilizer (HF), pig manure alternative 20% N fertilizer (ZF), biogas slurry and biogas residue alternative 20% N fertilizer (ZYF), compost alternative 20% N fertilizer (DF), and green manure in early rice and straw in late rice alternative 20% N fertilizer (LDF). The results showed that total N, NO3-, NH4+, total P and water soluble P in runoff water were decreased after base fertilizer and topdressing application. In double cropping rice field, total N, NH4+and NO3- contents in runoff water under HF reached 5.91 mg/L, 3.65 mg/L and 0.82 mg/L respectively, which were higher than other treatments. Compared with HF, total N, NH4+and NO3- contents in runoff water were significantly decreased when chemical fertilizers were partially replaced with organic materials, and the reduction of DF reached up to 1.18 mg/L, 0.71 mg/L and 0.14 mg/L respectively. Moreover, the treatments with organic materials alternative 20% N fertilizer significantly increased total P and soluble P content in the runoff water with the exception of DF. Compared to HF, other organic-inorganic fertilizers treatments decreased runoff N loss. In addition, total N, NH4+and NO3- loss of DF treatment was 10.25 kg/hm2, 6.17 kg/hm2 and 1.71 kg/hm2 respectively, which were nearly equal to those of HF. In conclusion, DF could significantly decreased runoff N and P loss, and was of great importance in protecting environment and controlling non-point pollution.

Abstract:To study the influence of contour reverse-slope terrace on runoff and sediment production, nitrogen and phosphorus loss in sloping farmland, the loss of runoff, sediment, nitrogen and phosphorus of sloping farmland were monitored from 2009 to 2015 through conducting the standard runoff plots in a typical Yizhe small watershed in Water Source Area of Songhua Dam in Kunming City. The results showed that the reduction effect of contour reverse-slope terrace on runoff and sediment was significant, the annual average reduction rate of runoff was 50.64% and the annual average reduction rate of sediment was 74.99%, the latter was significantly greater than the former. The reduction effect of contour reverse-slope terrace on nitrogen, phosphorus in runoff and sediment was significant, it reduced 68.75% of nitrogen loss and 82.16% of phosphorus loss every year, the annual reduction rates of total nitrogen in runoff and in sediment were 59.51% and 76.43% respectively, and the values for total phosphorus were 64.22% and 83.73%, respectively.

Abstract:In order to determine the reduction of nitrogen and phosphorus losses among different stand improvement patterns, Taxus mairei, Torreya grandis, Illicium henryi, Ardisia crenata were chosen as four different stand improvement tree species to improve Phyllostachy edulis forest structure, and the volumes of runoff and concentrations of nitrogen and phosphorous were measured from January 2013 to October 2014. Results showed that the total runoff of five forest stands were 3.06～9.22 m3 in 15 runoff events. The losses of total nitrogen were 7.6 times of the losses of total phosphorus, and the losses of ammonium nitrogen were 2.5 times of the losses of nitrate nitrogen. Stand improvement could reduce the ratio of ammonium nitrogen to nitrate nitrogen. The runoff was reduced by 40.0%～66.8% in these four stand improvement patterns in two years compared with Phyllostachy edulis pure forest. The accumulative losses of total phosphorus were reduced by 64.0%～83.8% in four stand improvement patterns compared with Phyllostachy edulis pure forest, and the corresponding values were 49.1%～78.8% for total nitrogen, 37.4%～76.2% for nitrate nitrogen, and 42.8%～80.4% for ammonium nitrogen. The Taxus mairei + Phyllostachy edulis forest had greatest reduction effect on runoff and nitrogen and phosphorus losses among four forest stand improvement patterns.

Abstract:High weathered soils in arid and semi-arid area are characterized by low soil fertility and high erosion potential. This paper evaluated the influences of nano-carbon on nitrate nitrogen transport on the sloping land (15°) of the Chinese Loess Plateau. Simulated rainfall experiments were performed on a natural, fallow loessial slope in the Shenmu Erosion and Environment Research Station, Institute of Soil and Water Conservation, Chinese Academy of Sciences, which locates in the Liudaogou watershed, Shenmu County, Shaanxi Province. Five application rates (i.e., 0.0%, 0.1%, 0.5%, 0.7%, and 1.0%) of nano-carbon were selected under the simulated rainfall experiments (rainfall intensity of 90 mm/h, and rainfall duration of 40 min). A constant-intensity rainfall method was adopted under natural conditions. Field plots were established on the slope that had been fallow for 5 years. The rainfall simulator came from the independent design of Xi'an University of Technology. Under the 90 mm/h rainfall intensity, the simulated rainfall experiments were carried out for 10 times in the 5 different pretreated plots in order to analyze the nitrate nitrogen loss for all the treatments. The main results were as follows: The application of nano-carbon in soil could effectively reduce the runoff and sediment yield, and the cumulative runoff and accumulated sediment yield had negative correlation with the amount of carbon applied in the soil. The application of nano-carbon could also reduce the nitrate nitrogen content in runoff and sediment, and the amount of nitrate nitrogen loss in runoff and sediment decreaseed with the increase of nano-carbon content. Compared with the change of nitrate nitrogen in soil profile, the application of nano-carbon could reduce the loss of nitrate nitrogen in the surface layer and increase the nitrate nitrogen content at 10—15 cm soil layer. By analyzing the effective depth of transport by runoff, the EDR under the control was max. With the increase of the amount of nano-carbon content, the EDR of each treatment decreased in turn. The results provide a guide for controlling soil water and nutrient loss on the sloping land.

Abstract:The black soil of Northeast China is an important grain production base in China. Soil and water losses in the area in recent years become crucial limiting factor of agricultural sustainable development and food security. Aiming at the mitigation of soil and water losses in the sloping farmland, two years experiments in 2015 and 2016 was conducted in Harbin to explore the influence of different N fertilization strategies and tillage measures on the water, soil and Nitrogen losses, 9 treatments were designed, including T1(bare land), T2(fallow land), T3(optimized N fertilizer: 180 kg N/hm2, longitudinal ridge), T4(optimized N fertilizer: 180 kg N/hm2, horizon ridge), T5(control N fertilizer: 210 kg N/hm2, longitudinal ridge), T6(reduced N fertilizer: 90 kg N/hm2, longitudinal ridge), T7 (organic manure partial substitution for chemical fertilizer: 150 kg/hm2 chemical N and 30 Kg organic N/hm2, longitudinal ridge), T8(optimized N fertilizer: 180 kg N/hm2, horizon ridge, clover maize hedgerow), T9(reduced N fertilizer: 90 kg N/hm2, longitudinal ridge, straw mulching and no-tillage). The results showed that the annual averaged surface runoff of T1 was 151.0 m3/hm2. Compared with T1, annual averaged runoff of T2, T3, T4, T5, T6, T7, T8, T9 decreased by 80.9%, 64.4%, 83.0%, 65.2%, 68.0%, 60.4%, 93.8%, and 88.1%, respectively. The annual averaged soil erosion of T1 was 9.5 t/hm2. Compared with T1, annual averaged soil erosion of T2, T3, T4, T5, T6, T7, T8, T9 decreased by 98.8%, 57.3%, 88.4%, 60.7%, 50.6%, 56.6%, 99.2%, and 94.4%, respectively. The annual averaged inorganic nitrogen loss of T1 with surface runoff was 207.6 kg N/hm2. Compared with T1, annual averaged inorganic nitrogen losses of T2, T3, T4, T5, T6, T7, T8, T9 decreased by 43.0%, 24.7%, 35.5%, 20.0%, 36.8%, 20.2%, 75.6%, and 55.9%, respectively. It was not ignore for the inorganic nitrogen losses of snowmelt runoff for sloping land. The performances of runoff retaining and reduced nitrogen losses for single-tillage measure on sloping land under spring corn system, of which hedgerow was the best ,followed by the straw mulching, and finally horizon ridge; combining horizon ridge and hedgerow technology performed the best for multi-tillage measures. When we adopted the conventional tillage measure with different fertilization strategies, it was much more runoff for organic manure partial substitution resulted from weaker aboveground growth; reduced N treatment performed high soil erosion and low surface-flow inorganic nitrogen losses resulted from less inorganic nitrogen concentration. The surface runoff and daily rainfall had linear positive correlations (R2: 0.213 9～0.543 8) except T2 and T9; the soil erosion, inorganic nitrogen losses and runoff had linear positive correlations (R2: 0.338 0～0.728 0, 0.618 4～0.895 2) except T1. When the annual ratio of NO3-—N/(NO3-—N+NH4+—N) decreased, the annual inorganic nitrogen loss with surface runoff also decreased.

Abstract:In order to explore long term evolution of soil erosion from Benggang-derived sediment deposits, indoor simulated rainfall experiment was conducted with a 30。slope of the Benggang deposit and rainfall erosion intensity of 3.33 mm/min, which represented a typically higher rain intensity in the study region. The experiment was repeated with 20 times and the erosion processes of the deposit was carefully recorded. Under the experimental conditions, the average contribution rate of rainfall splash and runoff flush to sediment yield was 47.6% and 52.4%, respectively. The sediment yield of colluvial deposits decreased exponentially in the process of erosion. The sediment yield was correlated with Froude number, Runoff power and Darcy-weisbach resistance coefficient, and these parameters could be used to quantitatively describe the efficiency of runoff sediment yield when the source of sediment was sufficient. Four stages of the erosion process from the colluvial deposits were founded, including (1) sheet erosion stage on the whole slope, the sediment concentration was 0.099 kg/L, and the sheet erosion was dominant, but the slope surface was not coarsening; (2) Initial formation stage of rill erosion, the sediment concentration was from 0.052 to 0.101 kg/L, mainly with rill erosion, but the slope coarsening was not obvious; (3) Stage of frequent expansion of rills with coarse slope, the sediment concentration was from 0.011 to 0.064 kg/L, mainly with rill erosion, and the coarsening of slope surface appeared; (4) The stage with frequent collapsed rills even forming ephemeral gully, the sediment concentration was from 0.008 to 0.036 kg/L, and there was no obvious dominant erosion mode, and the slope surface continued to coarsening. The separation and transportation of colluvial deposits by rainfall and its runoff results in the coarsening of the slope, and the coarsening of the slope, which in turn reduced the rainfall and runoff sediment yield.

Abstract:In order to explore the effect of freezing and thawing on the rainfall erosion on the slope, a freezing and thawing experiment was conducted in Xi'an, and the characteristics of rainfall erosion on slopes with different water content were studied in the experiment. The results showed that the emergence flow time increased first and then decreased with the increase of the initial water content, and the emergence flow time was delayed by freezing and thawing, specifically, the lag was up to 62.50% when the water content was 20%. The runoff flow on the completed thawed slope with 20% water content was 9.14% lower than that of unfrozen slope（P＜0.01）；the sediment yield on the completed thawed slope with 20% and 25% of the water content decreased by 28% than that of the unfrozen slope（P＜0.01）.In summary, it can be concluded that the effect of freezing and thawing on the runoff time and runoff process was the most obvious when the water content was 20%, while the effect of freezing and thawing on the sediment yield and erosive K value was the most obvious when the water content was 20% and 25%. When the water content was 20%, the sediment yield was the smallest and the erosibility was the lowest, hence, 20% can be used as the optimal water content of loess.

Abstract:Based on the laboratory rainfall simulation experiments, three rill morphological indexes including rill density, rill dissection degree and rill width-depth ratio were chosen to analyze the rill morphological evolution on loessal soil slope in western Shanxi Province, and explore the effect of rill morphology on the regularity of runoff and sediment yield in different slope length during rainfall. The results showed that the rill morphology evolution process was as follow: The drop sill formed firstly, then it developed into rill and then formed rill nets, and finally the rill collapsed. The rill density and dissection degree increased with the increasing of slope length and rainfall intensity, while rill width-depth ratio decreased with the increasing of them. The impacts of slope length on rill density and rill width-depth ratio were stronger than those of rainfall intensity, while the effect of rainfall intensity on rill dissection degree was stronger than that of slope length. The relationship of average runoff rate and slope length could be described with a linear function (R2＞0.95), and the relationship of average sediment yield rate and slope length could be described with a power function (R2＞0.96). Average runoff rate and sediment yield both increased with the increasing of slope length and rainfall intensity. The correlation analysis showed that there were significant positive correlations between the rill dissection degree and the rates of runoff and sediment yield at the 0.01 level, and the correlation coefficients were greater than 0.97, and rill density was significant positive correlation with the rates of runoff and sediment yield at the 0.05 level, and correlation coefficients were greater than 0.70.

Abstract:Based on the data of individual rainfall, runoff and sediment yield of hedgerows sloping farmland from 2012 to 2016 in Suining Soil and Water Conservation Experimental Station, the effect of hedgerows on runoff and sediment yield and microtopography of sloping farmland was analyzed. The results showed that the total runoff depths of the hedgerows were 80% to 84% of the control plots. Meanwhile, the total sediment yields of the hedgerows were 34% to 44% of the control plots. Hedgerow’s effects on sediment yield were better than that on runoff. The runoff depths and sediment yield of the control plots (plot Ⅱ and plot Ⅴ) were significantly correlated with the average rainfall intensity and rainfall (P <0.01). In the hedgerows plots (plot Ⅰ, plot Ⅲ and plot Ⅳ), the runoff depths and sediment yield were positively correlated with the average rainfall intensity and rainfall. Especially, there were highly significant correlations between runoff depths and rainfall. For three rainfall patterns, there were no significant differences in the runoff depths and sediment yield among different plots. The hedgerows effect on runoff and sediment reduction of rainfall A (short duration, heavy rainfall) was better than that of rainfall B (moderate duration, moderate rainfall) and rainfall C (long duration, light rainfall). After planting the hedgerows, there was sediment accumulation zone near hedgerow lines. The average slope of plot Ⅰ, plot Ⅲ and plot Ⅳ turned to 11.97°, 7.73°, and 7.89° from 15°, 10°, and 10°, respectively. Finally, hedgerows made sloping farmland benching.

Abstract:In order to explore the spatial distribution and variation characteristics of soil water in coal mining subsidence in Mu Us sandy land, and provide theoretical basis for the restoration of the mining area, experiments based on a linear sampling and classic statistical and geostatistical methods were conducted. Spatial distribution characteristics and variation law of soil water in the typical 0 to 100 cm dune area in the subsidence and the non-collapse (control) were studied. The results showed that in the typical sand dune location of non-collapse (control), the probability distribution curves of soil water changes in all layers along vertical and horizontal directions were all normal distribution, and it was consistent with the temporal and spatial variation characteristics of soil water in conventional dunes in Mu Us sandy land. In contrast, two years after the coal mine collapsed, the variations of soil water in different layers along vertical and horizontal directions were different, and soil water loss was more serious than that of control dune by nearly 10% to 30%, and the standard deviation varied from 0.54 to 1.05, increasing by 52.08% compared with the non-subsidence area (control). The probability of positive and negative deviation greater than 1 was over 50%, and the coefficient of variation varied from 0.14 to 0.28, which was 80% higher than that of non-collapse area (control). After collapsing, the average level of soil water, standard deviation, variance and variation coefficient had great changes, and influence of coal mining subsidence on soil water was the most in the middle layer (30—70 cm), and was not obvious in the surface (0—20 cm) and lower (80—100 cm). In coal mining subsidence, the dispersion degree of soil water in different layers along the vertical and horizontal direction was greatly improved, which enhanced spatial variation of soil water.

Abstract:By the experiments of simulated rainfall, the effects of straw mulching on nitrogen and phosphorus loss and runoff shear force were studied. Soil plots (1.5 m length × 0.5 m width × 0.3 m height) and rainfall intensity (2.0 mm/min) and slope gradient (20°) were established. Latosolic red soil was selected. The results showed that: (1) Straw mulching significantly decreased sediment yield and runoff volume, the benefit was 69.3% in sediment yield, and 99.2% in runoff volume. The infiltration rate of soil was improved at 32%, so straw mulching could conserve soil and water significantly. (2) Straw mulching significantly decreased the loss of runoff-associated total nitrogen, particulate nitrogen, dissolved nitrogen and total phosphorus, dissolved phosphorus, particulate phosphorus, and the loss benefits were more than 74% in nitrogen more than78% in phosphorus. The runoff-associated dissolved nitrogen and phosphorus loss were greater than the particulate nitrogen and phosphorus loss. Straw mulching reduced the runoff-associated phosphorus loss greater than that of nitrogen. (3) Cubic equations were established between runoff shear force per unit area per unit time and runoff-associated nitrogen and phosphorus loss rates and sediment yield rates, and the preliminary inference indicated that runoff shear force was the main dynamic factor of soil erosion. (4) The critical starting runoff shear force was 2.8 N m-2 under straw mulching, and 1.5 N m-2 under non-straw mulching.

Abstract:This study was conducted in the upstream watershed of Du River, central China, and ASTER GEDM was processed in the system for Automated Geoscientific Analyses (SAGA GIS) package in the R-platform. On the basis of obtaining watershed soil topographic index (STI) and its threshold setting, using Python module programming, three different scenarios (STI≥9, STI≥10, and STI≥11) were selected to delineate and understand the land use types and their areas and spatial distributions within hydrologically sensitive area (HSAs) in the watershed. The results showed that STI technique improved the identification of HSAs, which could reasonably predict the spatial differentiation of runoff in the watershed. Forest land was the major land use in the HSAs under all three scenarios, and about 50% of water was identified as HSAs. Under the three scenarios, the agricultural landscape and development landscape in the HSAs should be prohibited from carrying out intensive land development, and should arrangement priority vegetation buffer zones to protect water quality.

Abstract:In order to study the interception effect and hydrodynamic mechanism of vegetation filter strips (VFS) during runoff and sediment yield progress on slope surface, a simulated vegetation filter belt was set up on the inner soil trough, and the muddy water erosion tests were carried out. After getting the runoff and sediment yield and related hydrodynamic parameters under the situation of with or without vegetative filter strip through the tests, the vegetation filter intercepting effect of runoff and sediment was quantitatively analyzed and the relationship between sediment production rate and hydrodynamic parameters was explored. The results showed that VFS could effectively intercept runoff and sediments during the tests, and the interception rate was better under smaller flow. When the flow was 200 L/h, the interception rate was 33.2% for runoff and 96.9% for sediments. During the scouring process, the sediment yield rate had significant correlation with flow shear stress and flow power under the situation of with or without VFS, which were positive exponential function relationships (R2=0.67, R2=0.83) with flow shear stress and power function relationships (R2=0.70, R2=0.87) with flow power, respectively. Using a nonlinear regression equation Rs=1.184×10-6τ-4.114ω3.839（R2=0.73）with flow force and flow power to predict the sediment yield rate could get better effect.

Abstract:In order to obtain the best application method of super absorbent polymers (SAP) on soil and water conservation of the granite slope of red soil, the effect of SAP (mixed, layered, and furrowed) application on the erosion process of the granite slope of red soil was compared with the method of simulated rainfall experiment and lab analysis. The results indicated that: (1) the application of SAP can reduce the runoff and sediment yield and delayed the flow time on the granite slope of red soil. The mixed application of SAP and soil had a great influence on reducing the runoff and sediment yield on the granite slope of red soil in the rain intensity of 1.0 mm/min. Compared with the control slope, the cumulative runoff respectively decreased 34% and the cumulative sediment yield decreased 48% by the mixed application of SAP and soil. While layered application of SAP and soil had extremely significant effects on the runoff and sediment yield in the rain intensity of 1.5 mm/min. Compared with the control slope, the cumulative runoff respectively decreased 46% and the cumulative sediment yield decreased 67% by the layered application of SAP and soil. (2) The application of SAP had increased slope infiltration rate and soil water content, and reduced the runoff and sediment yield on the granite red soil slope. The mixed application method of SAP and soil had played a good role on soil and water conservation. (3) The effects of different application methods of SAP had significant on the runoff and sediment yield on the granite slope of red soil P＜0.05. The power function model of the cumulative runoff and cumulative sediment on the granite slope of red soil was concluded based on statistical analysis. Those results provided the theoretical basis for the runoff and sediment yield on the granite red soil slope.

Abstract:Antecedent rainfall plays an important role in the triggering mechanism of debris flow. The glacial debris flow triggering experiments of different original soil water content were carried out to simulate the washed glacial drift triggering process under varieties of antecedent rainfall. The results showed that：(1) The evolution type of glacial debris flow in study area preliminarily could be defined as slope-slide model. (2) Seepage played a leading role at the low original soil moisture content. A large number of fine particles were occurred, leading to the intergranular porosities increased to the original two times when grain-contact stress falling; then the rearrangement of the soil structure and enlargement of the pore-water pressure lead to the soil particles failure. It could be shown in the pore-water pressure as a “fall-uprush-fall” form. (3)Both Seepage and scour were key factors at higher original moisture content. The starting process of debris flow was intermittent, and the triggering moment that was the peak moment of pore-water pressure. (4) Both pore-water pressure and the volumetric soil water content showed periodical curves. The original soil water content was negatively associated with the debris flow starting time. (5) Based on the experiment phenomenon and the characteristics of curves, debris flow could be divided into four steps in this study. And the mechanism could be concluded to seepage erosion, soil front end framework and runoff scouring.

Abstract:The simulated rainfall method was applied, and three rainfall intensities (60, 90 and 120 mm/h) of representative erosive rainfall and three common slope gradients (3°, 5° and 7°) were chosen in the black soil region to analyze the effects of rainfall intensities and slope gradients on runoff, soil erosion, runoff rates and sediment concentrations of farmland unpaved road. The results showed that the total runoff mainly varied between 56.3 and 61.8 mm for different treatments. However, soil erosion rates increased 1.8～11.0 and 1.2～10.0 times, respectively with increasing rainfall intensities and slope gradients. Additionally, the mixed impacts of rainfall intensity and slope gradient on soil erosion were greater than those of the individual impact of the influencing factors. There was a mutual stimulation among the factors upon soil erosion. Furthermore, the effects of rainfall intensities on runoff rate patterns were obvious, while the effects of slope gradients were small. As rainfall intensities and slope gradients were increased, sediment concentrations obviously increased, and the fluctuation ranges also strengthened. Therefore, rainfall intensity and slope gradient showed notable effects on soil erosion of farmland unpaved road in the black soil region, and controlling rainfall and runoff erosivity, or changing pavement characteristics could effectively prevent soil and water loss on hillslopes.

Abstract:To explore the effects of acid environment on the disintegration characteristics of purple parent rocks, the similarity principle and the correlation fractal dimension calculation formula were used to investigate the fractal dimension features of purple mudstone disintegration of the Suining group (J3S), the Saximiao group (J2S) and the Penglaizhen group(J3P) under different pH conditions. Therefore, 24 times of static disintegration tests were carried out for these rock samples. The results showed that the pH played an important role in the disintegration of purple mudstone. The lower the pH value was, the stronger the disintegration was. The fractal dimension of J3S and J2S under different pH approached to 3 after 24 test cycles, and the lower the pH, the fewer cycles to obtain the stable fractal dimension, while that of J3P didn’t reach the stable fractal dimension. Fractal dimension had no significant differences among different acid treatments in the preliminary stage (p＞0.05), but had significant differences (p＜0.05) in the middle-later period. Furthermore, the differences of the fractal dimension under different acid treatments of each mudstone group varied with the disintegration stage. The disintegration rate of purple rock increased with increasing acidity, resulting from that most of the mineral composition of purple rock could not dissolve in water but chemical reaction in acid solutions and produced soluble salts.

Abstract:Selecting Hengnan County as the experimental area, runoff plots with the same slope and the same cropping pattern were set up, and the control experiments of different soil and water conservation measures were carried out. We studied the soil erosion modulus of sloping farmland and the benefits of soil and water conservation measures through observing and analyzing the annual rainfall runoff and sediment. The results showed that：(1) In 2016, 19 rainfalls with runoff were observed, and the rainfall was 1 145 mm, which was belonged to normal rainfall year; (2) The soil erosion modulus of bare slope without any protective measures was 4 450.57 t/(km2?a), reaching moderate erosion; (3) Compared with the bare slope, farmland had the effect of soil and water conservation, and different measures had significant difference in reducing runoff and sediment yield. Water conservation effect (decrease ratio of annual surface runoff) from large to small listed in the order of stone dike terraces (85.07%)＞slope terraces (81.50%)＞earth dike terraces (64.57%)＞hedgerow (57.96%)＞slope farming (37.49%). Soil conservation effect (decrease ratio of annual sediment yield) followed the order of stone dike terrace (98.74%)＞slope terrace (98.66%)＞earth dike terrace (97.39%)＞hedgerow (86.16%)＞slope farming (61.98%). Stone dike terrace and slope terrace showed better effect in soil and water conservation. In this study, the background value of soil erosion was observed accurately, and the benefits of the main soil and water conservation measures were evaluated quantitatively.

Abstract:In order to investigate the effects of different sand-gravel mulching amounts on soil water movement, soil water storage, evapotranspiration processes and winter wheat growths, two-year experiments were conducted in 24 soil containers which were put under a rain shelter at four sand-gravel mulching amounts (0, 23, 46 and 69 kg/m2). The soil water dynamic change was observed by a micro-lysimeter which contained a high-precision weighing transducer connected with a data logger. For the no-wheat and with-wheat conditions, when the sand-gravel mulch amounts increased from 0 to 69 kg/m2, the treatments were named NW0, NW23, NW46, NW69 and W0, W23, W46, W69, respectively. The results showed that: (1) Soil water storage increased with the increase of sand-gravel mulch amounts, the monthly soil evaporation, monthly evapotranspiration, cumulative soil evaporation and cumulative evapotranspiration decreased with the increase of sand-gravel mulch amounts. Soil water storages under the with-wheat conditions were lower than the values of the no-wheat conditions. The monthly soil evaporation, monthly evapotranspiration, cumulative soil evaporation and cumulative evapotranspiration under the with-wheat conditions were a little bit higher than the values under the no-wheat conditions, especially at the later winter wheat growth stages. Under the no-wheat conditions, in the first and second years, the total evaporations of the three coverage treatments were less than the non mulching treatment from 11.6% to 18.1% and 28.5% to 47.5%, respectively. Under the with-wheat conditions, in the first and second years, the total evapotranspiration of the three coverage treatments was less than the non mulching treatment from 2.2% to 3.7% and 0.7% to 3.6%, respectively. (2) All of the plant heights, leaf area indexes, productive panicle number, yields and water use efficiencies of the winter wheat increased with the increase of sand-gravel mulching amounts. In the first and second years, the maximum plant height of the three coverage treatments was more than the non mulching treatment from 5.3% to 17.2% and 1.0% to 5.8%, respectively. The maximum leaf area index of the three coverage treatments was more than the non mulching treatment from 17.9% to 74.6% and 7.9% to 28.2%, respectively. The yields of the three coverage treatments were more than the non mulching treatment from 6.6% to 14.2% and 12.6% to 44.6%, respectively. The water use efficiency of the three coverage treatments were more than the non mulching treatment from 8.0% to 16.1% and 15.6% to 67.1%, respectively. From the results, the most suitable sand-gravel mulching amount was 69 kg/m2, the sand-gravel mulch can effectively prevent soil water evaporation, the increased soil water storage at early crop growth stages could be utilized for later stages of crop growth, which highly contributes for improving crop yields and water use efficiency.

Abstract:In order to investigate the effects of maize straw strip mulching on soil moisture and yield in potato field in northwest semi-arid region of China, four trentments (M1: Big ridge black film mulch planting, M2: Maize straw strip mulching on flat planting, M3: Maize straw strip mulching on furrow and ridge planting, CK: Conventional tillage with no straw covered) were conducted to compare the effects of different mulching patterns on the growth index, soil moisture in different layers, potato yield and water use efficiency in two growing seasons field experiment. Results showed that three mulching patterns significantly increased the yield by 11.68%～21.74%, and improved the water use efficiency by 22.82%～48.63% compared with CK. Compared to CK, single plant yield increased 26.02%～48.37%, the height of plant increased 3.18%～12.82%, single plant biomass increased 0.59%～26.49% and water consumption of crops during the whole growth period decreased 55.29～66.21 mm, thus M2 had the best or better effects. In the potato whole growth period, the average soil moisture in 0—200 cm soil layers in black plastic-film mulching big ridge pattern (M1) was lower than CK by 0.89 percentage points in a normal precipitation year, and M1 is higher than CK by 1.30 percentage points in slight drought year. M2 was better than M1 and CK in whether normal precipitation or slight drought year, and it was 0.20～0.89 and 0～1.50 percentage points higher than M1 and CK, respectively. Among them, maize straw strip mulching on flat planting (M2) had good effects on crop growth, yield increase and water use efficiency, which is suitable for promotion in Northwest semi-arid region.

Abstract:Based on the stable isotope method, The water use patterns and strategies of Populus euphratica and Tamarix ramosissima at different ages were studied in Tarim River Basin. The results showed that: (1) precipitation offset of plant and soil water were significantly different from the offsets of groundwater, indicating that there were two?inhomogeneous and incompletely mixed water reservoirs that supply either for the plant water fluxes or the fluxes of groundwater. (2) The δ18O value of surface soil water fluctuated widely, which was affected by evaporation, and the δ18O value of soil water decreased gradually with the increasing soil depth. (3) The water used by the Populus euphratica and Tamarix ramosissima with different ages came from different sources. The deeper soil water could be accessed after the ages increased. There might be water competition at the mature age of Populus euphratica and seedling age of Tamarix ramosissima. Whether seedling or mature, Tamarix ramosissima could use deeper water than Populus euphratica, and therefore, be more adaptable to the arid environment.

Abstract:Based on field sampling, indoor simulation experiment and laboratory analysis, roots density parameters (i.e., root length density, root volume density, root surface area volume) in different roots diameter classes of four typical plants (Sophora viciifolia, Bothriochloa ischaemum, Artemisia gmelinii and Lespedeza davurica) in the hilly area of the Loess Plateau, and their relationships with soil physicochemical properties and soil separation rate were studied in this paper. The results showed that: (1) Root diameter of the four plants were mainly concentrated in the range of 0～1.0 mm, and root with these diameters accounted for 86%～93% of root length and 46%～61% of root surface area. And the root diameter was larger, the root density parameters were smaller. (2) The effect of root density parameters on soil physicochemical properties (bulk density, organic matter, and aggregates) were different among the four plants. Roots density parameters of S. viciifolia were significantly correlated with the soil bulk density and organic matter when the root diameter was 0～1.0 mm. The root density parameters of A. gmelinii were significantly and negatively correlated with soil bulk density, while they were significantly positively correlated with soil organic matter in 0～1.0 mm diameter, there were significantly positive correlations between soil aggregates and roots density parameters in all diameter classes. The root with 0～5.0 mm diameter of B. ischaemum could effectively improve the soil bulk density, and the density parameters of the root with diameter of 0～2.0 mm were significantly positively correlated with soil organic matter and aggregate. The roots with diameter of 3.0～5.0 mm of L. davurica had significantly effect on soil bulk density, and the roots with diameter larger than 1.0 mm had significantly effect on soil water stable aggregate. (3) There was a negative correlation between soil separation rate and the root density parameters. Besides L. davurica, the other plants’ roots density parameters were significantly negatively correlated with soil separation rate when the roots were 0～1.0 mm in diameter.

Abstract:By using a combination of multiple soil fractionation methods which does not destroy the basic structure of organic carbon physics group, a five consecutive years experiment was conducted to evaluate the effects of various types of organic materials, such as milk vetch, rice straw and organic poultry manure on soil organic carbon and its physical componets in paddy fields. The results shows that, soil aggregate was mainly distribution in the grade 2～0.25 mm and 0.25～0.053 mm, and the aggregate particle organic carbon concentration decreased with the decrease of particle size. The organic carbon storage in the 0.25～0.053 mm and ＜0.053 mm particle size aggregates increased by using different organic materials, and the treatment with milk vetch, straw and organic fertilizer all increased the amount of soil organic carbon. The results indicate that the organic material returning to the paddy soil can greatly increase the carbon storage in the soil micro aggregates. Returning organic material to the paddy soil increased the concentration oflight fraction particles and reduced the concentration of the heavy fraction particles in soil. Organic materials application in the paddy soil is helpful for the formation of light fraction particles in soil. Among the different physical fractions in soil used for rice cultivation, light fraction organic carbon correlated significantly with ＞0.25 mm aggregate organic carbon and ＜0.053 mm aggregate organic carbon and highly significantly with aggregate organic carbon in the 2～0.25 mm size fraction. Returning organic material in the paddy soil can promote the formation and development of soil aggregates and the fixation of organic carbon, effectively improve the soil micro aggregates and light fraction content, and increase the soil carbon storage in micro aggregates and light fraction organic carbon reserves, change the composition characteristics of organic carbon in paddy soil.

Abstract:Field experiments were conducted to investigate the effects of sepiolite on the composition and stability of soil aggregates and soil organic carbon content during the processes of in situ immobilization remediation for Cd contaminated vegetable field. The results showed that the amounts of 5～8 mm and ＜0.25 mm aggregates under the sepiolite treatments were decreased compared with the control. However, the contents of 2～5 mm, 1～2 mm, 0.5～1 mm and 0.25～0.5 mm soil aggregates were all significantly increased with the increment of sepiolite (P＜0.05). In 0—15 cm soil layers, mean weight diameter (MWD) and geometrical mean weight (GMD) of soil aggregates increased first and then decreased with the increase of the amount of sepiolite, whereas it was reduced in 15—20 cm soil layers. The concentration of soil organic carbon was reduced under the application of 0.5% sepiolite, with the maximum reduction up to 21.1%, while it was increased when the treatments of spiolite was 1% (H1) and 1.5% (H1.5), with the maximum increase of 2.9% and 70.3%, respectively, when compared with the control. The soil organic carbon contribution rate in 5～8 mm, 2～5 mm and 1～2 mm of soil aggregates was enhanced under different treatments of sepiolite.

Abstract:In order to investigate the composition and stability of soil aggregates and explore the soil structure of Chinese fir plantation, in this study, 0—100 cm soil layers of Chinese fir plantation in different developmental stages were taken as the object, dry sieving was used to determine composition of soil aggregates and wet sieving was used to determine the stability of aggregates. The results showed that under the dry sieve treatment, the soil aggregates of the Chinese fir plantations were dominated by macroaggregates (＞0.25 mm) at each developmental stage, which was above 80%, and the proportion of soil macroaggregates in middle age forest and mature forest was higher than that of young forest in each soil layer, it had significant difference in 0—20 cm soil layers; In each soil layer, for the soil aggregates with clay diameter ＞5 mm, which had a higher proportion and had a significant effect on the composition of soil aggregates with the different developmental stages of Chinese fir. Under the wet sieve treatment, the proportion of water stable macromolecule (＞0.25 mm) was significantly decreased with the increase of soil layer in each developmental stage, for the 0—80 cm soil layers, the proportion of water stable macromolecule of middle age and mature forest was higher than young forest, for the 0—20 cm and 20—40 cm soil layer, the proportion of water stable macromolecule of middle age forest were 41.79% and 39.06% higher than that of the young forest, which had significant difference; The PAD characteristics of soil aggregates displayed an opposite trend as compare to water stable macromolecules in each developmental stage of Chinese fir plantation, MWD and GMD decreased significantly with the increase of soil layer, and the GMD of soil aggregate in middle age forest and mature forest were significantly higher than those of young forest in 0—100 cm soil layers. Therefore, the stability of soil aggregates in Chinese fir plantation decreased with the increase of soil layer, and the soil structure of middle age forest and mature forest was better than that of young forest.

Abstract:In order to investigate the difference of artificial sand-fixation forest models on soil organic carbon (SOC), taking the soil as the research object under the 5 forest models in Zhanggutai sandy land of Liaoning province. We compared the distribution characteristics of SOC, nitrogen, and humus in 0—5 cm, 5—10 cm, 10—20 cm, and 20—40 cm soil layers through statistical methods. The results showed that the change of SOC content was as follows: Pinus sylvestris pure forest (4.72 g/kg)＞Mixed forests of Maackia amurensis and Pinus sylvestris (4.48 g/kg)＞Mixed forests of Elm and Pinus sylvestris (4.38 g/kg)＞Mixed forests of Spruce and Pinus sylvestris (4.21 g/kg)＞Poplar forests (3.95 g/kg)＞CK (1.88 g/kg) in 0—40 cm soil layer; The comparation of organic carbon storage was expressed as: Mixed forests of Maackia amurensis and Pinus sylvestris (20 t/hm2)＞Pinus sylvestris (19.92 t/hm2)＞Mixed forests of Spruce and Pinus sylvestris (19.06 t/hm2)＞Mixed forests of Elm and Pinus sylvestris (17.31 t/hm2)＞Poplar forests (16.61 t/hm2)＞CK (8.44 t/hm2); The analysis of humus components found that soil humus carbon content was expressed as: Mixed forests of Spruce and Pinus sylvestris (2.04 g/kg)＞Mixed forests of Elm and Pinus sylvestris (1.93 g/kg)＞Pinus sylvestris (1.74 g/kg)＞Poplar forests (1.65 g/kg)＞Mixed forests of Maackia amurensis and Pinus sylvestris (1.55 g/kg)＞CK (0.75 g/kg). There were significant positive correlations between SOC and total nitrogen, humic carbon, humic acid, fulvic acid, humic acid/SOC, and fulvic acid/SOC.

Abstract:In order to explore the relationship between the root and leaf growth and yield formation of different nitrogen efficiency rice under different combinations of field drainages and panicle nitrogen fertilizer managements, three field drainage degrees (W1, W2, W3) were set, in which the soil moisture content of 0—20 cm were (53.60±5)%, (40.20±5.00)% and (26.80±5.00)%, respectively, meanwhile three panicle nitrogen fertilizer managements (N1, N2 and N3) were conducted, which mean that applying panicle fertilizer in the first day, the eighth day and the 15th day after the field were rehydrated, respectively. The effects of field drainage and panicle nitrogen fertilizer managements on root morphological characteristics, root dry weight, leaf area index, photosynthetic rate of flag leaves, leaf dry weight, yield and its components of rice were investigated with Dexiang 4103 (nitrogen efficient variety) and Yixiang3724 (nitrogen inefficient variety). The results showed that: (1)The mean yield of Dexiang4103 was 11.57% higher than that of Yixiang3724; (2)The yield of these two varieties had significant positive correlation with the dry weight and LAI of leaf at heading stage, and the yield of Dexiang4103 had significant positive correlation with root dry weight, total root length and root surface area per plant at heading stage and the 15 days after full heading, and the yield of Yixiang3724 only had significant positive correlation with root dry weight per plant at the same stages; (3)Agronomic nitrogen efficiency of Dexiang4103 was significantly positively correlated with root dry weight and root surface area per plant at heading stage, and root length per plant on the 15 days after full heading, the same parameter of Yixiang3724 had significant positive correlation with root length per plant at heading stage, and root dry weight per plant on the 15 days after full heading; (4) In the treatment of W1 and W2, there was no significant difference in total root length and root surface area per plant between nitrogen efficient variety and nitrogen inefficient variety at the heading stage; the total root length of nitrogen efficient variety was significantly less than that of nitrogen inefficient variety on the 15 days after full heading; in the treatment of W3 , the total root length and the root surface area per plant of nitrogen inefficient variety were both greater than those of nitrogen efficient variety at heading stage; and there was no significant difference in total root length and root surface area per plant between these two varieties on the 15 days after heading; (5) At maturity, dry weight and LAI of leaf of nitrogen inefficient variety were both higher than those of nitrogen efficient variety, on the contrary, the leaf area attenuation rate of it was much lower than that of nitrogen efficient variety during heading to maturity stage; (6) Applying with the treatment of W1N3 on Dexiang4103, the leaf area attenuation rate was reduced, and the total root length from heading to maturity, leaf photosynthetic rate and yield were all increased; while applying with the treatment of W2N2 on Yixiang3724 could get the same effect. In summary, the effects of paddy field drainages and panicle nitrogen fertilizer management on the root and leaf characteristics were very obvious during middle to latter growth period for different nitrogen efficiency rice. By optimizing paddy field drainage degree combining with applying the panicle nitrogen fertilizer managements for these two varieties, and constructing reasonable root index and leaf system, we could promote the nitrogen absorption of root, and improve the material production and transport capacity of leaf during the filling stage, and finally improve yield.

Abstract:The dynamic characteristics of soil carbon and nitrogen contents were investigated under four N treatments (N0, no N input treatment; N1, low N input treatment; N2, middle N input treatment; and N3, high N input treatment) in a Suaeda salsa marsh in the high tidal flat of the northern Yellow River estuary from April to November in 2014. Generally, the contents of SOC, TN, NH4+—N and NO3-—N under different N input treatments generally increased with increasing depth. Compared with other N input treatments, the highest contents of SOC and NO3-—N of each soil layer occurred under the N2 treatment and the highest contents of TN and NH4+—N of each soil layer occurred under the N3 treatment. Although the dynamics model of TN and NH4+—N contents in soil were not altered by different N input treatments, they were increased with the increase of nitrogen loading. Different N input treatments could alter the dynamic change model of SOC and NO3-—N contents in soil. The appropriate input (N1 and N2) significantly increased the contents of NO3-—N in soil, while the excess N input (N3) was not benefit for the accumulation of NO3-—N. Furthermore, the surface soil (0—20 cm) from different N input (especially N2 and N3 treatments) showed a significantly higher SOC contents than those from N0 treatment (P＜0.05) after mid-July, indicating that the continuous input of exogenous nitrogen may not be favorable to the chemical conversion of SOC in soil. This study suggest that wetland environment is conducive to soil nitrogen mineralization when the nutrient situation in S. salsa marsh reaches N1 and N2 level in the future, which in turn can improve the supply of soil nitrogen nutrients. This study also highlights the continuous input of nitrogen loading may inhibit the chemical conversion of SOC, which in turn can help to improve the carbon sink function of S. Salsa marsh.

Abstract:To study the effects of water and nitrogen regulation on soil organic nitrogen fractions, total nitrogen (TN) and mineral nitrogen (MN) of greenhouse soil (0-30 cm) in fallow period, a tomato field experiment with mulched drip irrigation was conducted with different irrigation lower limits (W1, W2, W3) and nitrogen application rates (N1, N2, N3). The results indicated that greenhouse soil organic nitrogen was mainly in the form of acid-hydrolyzable nitrogen (AHN), and in general, the AHN content was greater than that of non-hydrolyzable nitrogen (NHN). The distributions of soil organic nitrogen fractions under different treatments were significantly different in AHN and NHN. Generally, the order of the contents and distribution proportions of soil organic nitrogen fractions to total N was: amino acid nitrogen (AAN)/ammonia nitrogen (AN)＞unknown nitrogen (UN)＞amino sugar nitrogen (ASN). Except for the ASN, both the contents and distribution proportions of AHN fractions decreased significantly with the increase of soil depth (P＜0.05). Similarly, the contents of TN, MN and total soil organic nitrogen (TSON) also decreased significantly with the increasing soil depth (P＜0.01). Under different treatments, the differences among TN and soil organic nitrogen fractions besides ASN reached a very significant level (P＜0.01). Only AN and AHN had the significant positive correlation with MN (P＜0.01). The results from two-way ANOVAs showed that all the effects of irrigation, nitrogen fertilization and their interaction on TN, MN and TSON reached very significant level (P＜0.01). Therefore, the change of greenhouse soil nitrogen content was closely related to the regulation of water and nitrogen. AN and AAN were the main forms of soil organic nitrogen, the main components of soil available nitrogen, and also the indicator of nitrogen supply potential in greenhouse soil. Considering the soil nitrogen supply potential, the most reasonable pattern of water and nitrogen application was W2N2 in greenhouse soil.

Abstract:In order to seek the optimal irrigation scheme for high yield and high water use efficiency (WUE) of winter wheat, and provide theoretical and technical support for water-saving and high-yielding cultivation of winter wheat, supplemental irrigation (SI) experiments were conducted to explore the methods for determining the optimal supplemental irrigation amount at critical growth stages of winter wheat according to water consumption and natural water supply. The experiments were conducted from 2007 to 2015 on the basis of the same water and fertilizer management during the sowing period, and the rain-fed treatment during the growing season (without irrigation during emergence to maturity) was taken as the control. Two factors including time and amount of SI were set. Selected the annual rain-fed treatment and the optimal supplemental irrigation treatments with better grain yield and WUE, and the natural water supply, irrigation capacity and grain yield of these treatments during growth period were analyzed statistically. The results showed that the grain yield was significantly correlated with the main water supply (soil water storage in 0—100 cm soil layer +irrigation amount at sowing) at sowing period and the precipitation in different growth stages under rain-fed conditions, but there was no significant relation between them under the optimal SI conditions. The suitable cumulative water supply from sowing to each critical growth stages for achieving high yield and high WUE was basically stable. Appropriate SI could effectively compensate for the lack of natural water supply at different growth stages. Under suitable water supply conditions at sowing stage, there was a significant quadratic curve relationship between the optimal SI amount and the rain-fed grain yield from emergence to jointing, and there was a significant negative correlation between the above two parameters from emergence to flowering stage. In addition, the volumetric soil water content in 0—20, 0—40, 0—60, 20—40, 20—60 cm soil layers were all significantly linearly related to soil water storage in 0—100 cm soil layer at sowing period. It was feasible to predict soil water storage in 0—100 cm soil layer by using 0—40 cm soil water content. 8-year-experimental results showed that the optimum irrigation rate during the whole growth period of winter wheat in Huang-Huai plain was averagely 101.8 mm, ranged from 51.0 to 172.0 mm, and this kind of irrigation rate could achieve high yield (9 000～10 000 kg/hm2) and high WUE (20.3～26.8 kg/hm2/mm) . The data from two experimental sites during 2015—2016 showed that the soil water storage in 0—100 cm soil layer could be predicted by the volumetric soil water content in 0—40 cm soil layers, and the simulated values were consistent with the measured values. Compared with the quota irrigation treatment, on-demand SI treatment not only maintained high grain yield, but also reduced irrigation water by 36.2～57.6 mm, saved water by 20.1%～32.0%, and significantly improved WUE.

Abstract:Subsoiling before sowing (PS) is beneficial to improve soil structure and permeable capacity. To explore the effect of PS of winter wheat on soil physical properties and water use efficiency of Summer Maize, field experiment was carried out with traditional rotary tillage as CK. In the study, the soil particle size composition, bulk density, soil compaction, growth index and water use efficiency were observed during summer maize growing stage in north china plain. The results showed that there was no significant difference in soil particle size between PS treatment and CK. During the whole growth period, the soil bulk density of PS decreased by 0.63%～3.85% while the porosity was increased by 0.27%～3.67% compared to CK in 0—40 cm soil layer; Soil compaction of PS was significantly decreased by 37.76% (at 20—30 cm) and 22.26%(at 30—40 cm) compared to CK at jointing stage. In the whole growth period, soil water storage capacity, plant height, leaf area index and dry matter accumulation were all higher than CK. Specifically, the yield was significantly increased by 9.50%, the spike length and grain weight per panicle were increased by 4.18% and 6.50% (p＜0.05), respectively, and the water use efficiency was increased by 5.08%. Effects of the water saving and yield increasing were significant under PS treatment.

Abstract:The aims of this study were evaluating the impact of mixed applying controlled-release urea and conventional urea on matter accumulation, nitrogen uptake and migration, and grain yield of spring maize, and improving the high yield and high efficiency cultivation techniques in southern Ningxia area. And this study could provide theoretical and technical reference to scientific nitrogen management techniques for spring maize in arid and semi-arid rainfall-fed region. Xianyu698 taken as experiment subjects were grown in controlled environments with two nitrogenous fertilizers (controlled-release urea (CRU ) and conventional urea ( U)) in four treatments (T1: applying U as basal fertilizer by N150 kg/hm2 + U topdressing at V12 by N75 kg/hm2; T2: CRU as basal N75 kg/hm2 + U as basal N75 kg/hm2+ U topdressing at V12 N75 kg/hm2; T3: CRU as basal N 150 kg/hm2+U as basal N 75 kg/hm2; T4: CRU as basal N 225 kg/hm2). The treatment without applying nitrogen fertilizer was CK. The results showed that when applying the same amount of nitrogen, compared to conventional urea treatment (T1), reasonable mixed application of controlled-release urea and urea as basal fertilizer (T3) could significantly increase maize yield by 12.63%, and this were mainly due to extremely enhancement of grain number per spike. Reasonable increasing the ratio of controlled-release urea in basal fertilizer could promote the accumulation of dry matter at post-anthesis and the whole growth period, and increase the absorption and accumulation of nitrogen in vegetative organs and grains of maize. The study also found that applying controlled-release urea was favorable to enhance nitrogen agronomic efficiency, nitrogen use efficiency and fertilizer contribution ratio, and the effect of T3 was the best. The nitrogen agronomic efficiency and fertilizer contribution ratio of T3 were 52.12% and 22.96%, 35.39% and 20.53% higher than those of T2 and T4, respectively. This study indicated that it was appropriate to applying reasonable mixed controlled-release urea (two-thirds of the total amount of nitrogen fertilizer) and conventional urea (one-third of the total amount of nitrogen fertilizer) as basal fertilizer.

Abstract:Rhizobox culture method was employed to investigate the effects of biochar and pectin on nutrient and heavy metals migration in soil-plant system irrigated by reclaimed water. The results showed that reclaimed water irrigation did harm to the plant growth. Plant grew better in pectin treatments than biochar though there was no significant difference between the both. When irrigated with reclaimed water, the shoot biomass in pectin treatments were 59.32% higher than CK. Compared with distilled water irrigation, reclaimed water irrigation increased the soil pH. When the irrigation water was same, the soil pH of pectin treatments was a little lower than the biochar treatments. Both the biochar and pectin treatments raised the soil nutrient contents, and pectin performed better for the increase in soil available nitrogen, available phosphorous and organic matter, while biochar resulted in the higher increase in soil available potassium. Biochar enhanced the plant nutrient contents, and pectin improved the transport capacity of nutrients. Bichoar decreased the soil available Fe, Mn, Cu, and Ni contents, but pectin increased the soil available Fe, Mn, Cu, Pb, Ni contents. The heavy metals contents in plant roots under pectin treatments were generally higher than that of biochar treatments. Take the distilled water irrigation for example, the Fe, Mn, Cu, Zn, Pb, Cd, Ni contents in plant roots of pectin treatments were 165.29%, 113.01%, 21.16%, 92.74%, 14.61%, 26.86% and 53.43% higher than that of biochar treatments. Fortunately, the translocation factors of Cu, Zn, Pb, Cd, Ni in pectin treatments were lowest. This study could provide the theoretical basis for the agricultural safe utilization of biochar and pectin in north alkaline soil with reclaimed water irrigation.

Abstract:To investigate the effect of Spartina alterniflora invasion on soil organic carbon fractions and the stability of soil, the soil samples were collected from wetlands of mangroves and invasive species S. alterniflora (before invasion was mangrove forest) in the Zhangjiangkou Estuary, Jiulong River Estuary and Min River Estuary of Fujian, and Yueqing Bay of Zhejiang. The contents of soil organic carbon (SOC), soil organic carbon storage (SOCS), active organic carbon fractions (microbial biomass carbon-MBC, easily oxidized organic carbon-EOC and water soluble organic carbon-WSOC) and chemical bonded organic carbon components (calcium bonded organic carbon (Ca—SOC) and iron-aluminum bonded organic carbon (Fe (Al)—SOC)) were measured in laboratory. These results showed that compared with the mangrove, soil SOC, SOCS, MBC and EOC contents decreased after S. alterniflora invasion, especially SOC and SOCS, their reduction rates were about 9.86%～27.13% and 13.95%～26.29%, respectively. While, soil WSOC content had increased by 5.75%～53.52%. Soil chemical bonded organic carbon components were also influenced by S. alterniflora invasion. The ratio of Ca—SOC/SOC increased, while the ratio of [Fe (Al)—SOC+residual state SOC]/SOC decreased. These results indicated that S. alterniflora invasion not only changed the soil organic carbon pool, but also changed its stability. The chemical bond of soil organic carbon might be the main protective mechanism for the soil organic carbon stability in mangrove wetland, which was important for mangrove carbon sink function.

Abstract:A field experiment was conducted to study the effect of straw and biochar on ammonia volatilization and inorganic nitrogen content of the apple orchard soil using glycerolphosphate double layer sponge ventilation method. This experiment included four treatments, which were CK (N0), N (applied urea 250 kg/hm2), N+S (applied urea 250 kg/hm2+straw) and N+B (applied urea 250 kg/hm2+biochar). The results showed that there were significant differences in ammonia volatilization rate and losses amount among different treatments. Ammonia volatilization rate of the three treatments applied with urea (N, N+S and N+B) were significant higher than that of control (CK) treatment, and it increased quickly after fertilization, and the peak value of it appeared on the third day after applying nitrogen fertilizer, and then gradually declined. There were significant differences in the peak value of ammonia volatilization rate among different treatments, and the maximum peak value of it appeared in N treatment, which was 2.37 kg/(hm2·d), followed by N+S treatment (1.65 kg/(hm2·d)), and then N+B treatment (1.32 kg/(hm2·d)), and the peak value of ammonia volatilization rate of N treatment was 1.44 and 1.80 times of N + S treatment and N + B treatment, respectively. The variation trends of soil ammonium nitrogen content in 0—10 cm soil layer were consisted with those of ammonia volatilization rate, and there was a significant positive correlation between these two parameters. The peak value of ammonium nitrogen content was different significantly among the four treatments, the maximum peak value of it was found in N treatment, followed by N+S treatment, and the value of N+B treatment was the lowest. After removing background value of the CK, the maximum ammonia volatilization loss occurred in N treatment, which reached to 15.29 kg/hm2 and accounted for 6.12% of the total amount of nitrogen applied, and the above two values of N+S treatment and N+B treatment were 9.32 kg/hm2 and 3.73%, and 6.01 kg/hm2 and 2.40%, respectively. Therefore, adding straw and biochar could significantly reduce the nitrogen loss through ammonia volatilization, and adding biochar could get the best effect.

Abstract:The Fuji / M. hupehensis. Biennial plants were selected, and the different doses of vitamin B6 (VB6) and compound vitamin B (COB) were added under pot experiments to study the effects on biological characteristics and physicochemical properties of apple trees. The pot experiments were carried out in 2006. VB6 and COB were added into the soil of Fuji on 26th May. And the doses were 0 (control), 0.02, 0.03, 0.04 g/plant respectively.The plant height, diameter, leaf area, leaf antioxidant activity, chlorophyll content, photosynthetic fluorescence parameters and the growth and distribution of roots were determined. The results showed that different doses of VB6 and COB had different effects on plant height, stem diameter, plant biomass, leaf area and antioxidant activity, photosynthetic fluorescence parameters and root distribution of apple trees.The plant growth was significantly improved by the addition of VB6 and COB. COB of 0.04 g/plant treatment had the most significant effects on aboveground growth, and VB6 with 0.03 g/plant increased leaf area most significantly, i.e. 22%. The plant height, stem diameter and tip length were increased by 24%, 34%and 45% significantly, compared with the control in October, and no significant difference were observed between VB6 of 0.03 g/plant and COB of 0.04 g/plant. The total length, weight, volume and surface area of the underground were significant improved under VB6 of 0.03 g/plant and COB of 0.04 g/plant, and the number of root tip and bifurcation also increased significantly. There was no significant difference in antioxidant enzyme activities of apple leaves under VB6 of 0.02 g/plant and COB of 0.02 g/plant, compared with control. The resistance of plants was significantly enhanced under VB6 of 0.03 g/plant and COB of 0.04 g/plant, with the increased activities of antioxidant enzymes. The chlorophyll contents in apple leaves were significantly improved, and the photosynthetic fluorescence characteristics were also improved remarkably, and there was no significant difference between VB6 of 0.03 g/plant and COB of 0.04 g/plant. The results showed that VB6 of 0.03 g/plant and COB of 0.04 g/plant had the most significant effect on the biological traits and physicochemical properties of apple trees. In view of the higher effective dose and cost of COB, it was recommended to use VB6 to improve soil nutritional conditions.

Abstract:In order to study the effects of biochar application on the soil physicochemical properties, enzyme activities and cucumber yield, and find a scientific basis for the popularization and application of biochar in agriculture, field experiments were conducted in greenhouse demonstration area, Rugao Institute of Agricultural Sciences, Jiangsu province. Biochar was incorporated into the soil at the rates of 0, 5, 10, 20, 30 and 40 t/hm2, respectively. The results showed that biochar application had significant effects on soil physicochemical properties and enzyme activities. The optimal rates of biochar application were 40 t/hm2 and 30 t/hm2 for improving the soil physicochemical properties and soil nutrient content, respectively. Biochar application reduced the soil bulk density by 0.88% to 10.52%, while increased the soil porosity, saturated water content, field water capacity, saturated hydraulic conductivity, organic matter, total nitrogen, the nitrate nitrogen content, ammonia nitrogen content, and available phosphorus by 3.68% to 7.53%, 27.96% to 119.25%, 30.73% to 55.05%, 1.89% to 224.61%, 10.39% to 54.56%, 6.06% to 22.58%, 2.33% to 45.63%, 235.71% to 414.29% and 19.37% to 77.76%, respectively, compared with the control treatment. The activities of soil urease and catalase and the cucumber yield increased at first and then decreased with the biochar application increasing. The activities of soil urease and catalase were the highest when the biochar application amount were 30 t/hm2 and 20 t/hm2, respectively, and they were increased by 104.57% and 15.38% compared with the control, respectively. The cucumber yield increased dramatically by 21.80% compared with the control treatment when the application rate of biochar was 30 t/hm2. The principal component analysis showed that the soil quality with different biochar application rates decreased in the order of C4＞C5＞C3＞C2＞C1＞CK. The applying biochar in soil could not only increase cucumber yield, and improve the physical and chemical properties of soil and the soil nutrient content, but also improve the biological properties (such as: soil enzyme activities).

Abstract:In order to study the effects of bio-organic fertilizer on the fertility and enzymes activities in fluvo-aquic soil. A field experiment was conducted, and the changes of soil fertility characteristics and enzymes activities were measured in different growth stages of cucumber at 0—15 cm and 15—30 cm soil layers. The bio-organic fertilizer was once applied at rates of 0, 10 and 20 t/hm2, designated as CK, Y1 and Y2 respectively. The results showed that: (1) In the same growth period of cucumber, all the contents of total nitrogen, ammonium nitrogen, nitrate nitrogen, available phosphorus and organic matter increased at 0—15 cm and 15—30 cm soil layers with increasing bio-organic fertilizer application rates. In the mature period of cucumber, Y1 increased the contents total nitrogen, ammonium nitrogen, nitrate nitrogen, available phosphorus and organic matter in soil by 5.99%, 11.21%, 17.48%, 5.98% and 39.30% respectively, while the corresponding values were 6.59%, 25.86%, 21.99%, 10.78% and 61.76% respectively in Y2, compared with CK. Significant differences were found in ammonium nitrogen and organic matter among the three treatments. Under the treatments applied with bio-organic fertilizer at 15—30 cm soil layer, the nitrate nitrogen contents were increased by18.83% to 23.27%, and available phosphorus by 39.30% to 61.76%. (2) In the same growth period, the increased trends of soil urease and catalase activities were found with the increasing bio-organic fertilizer application rates at different soil layers. In the mature period, under the treatments applied with bio-organic fertilizer, soil urease activity was increased by 47.02% to 62.08%, and catalase activity by 14.41% to 23.73% compared with CK at 0—15 cm soil layer, while the values were 49.17% to 67.75% and 40.01% to 63.33% at 15—30 cm soil layer. (3) With the growing season, soil fertility indexes and urease activity decreased, while catalase activity increased first and then decreased. Besides, soil fertility indexes and enzyme activities at 0—15 cm soil layer were significantly higher than those at 15—30 cm soil layer. In conclusion, the soil fertility, urease and catalase activities were obviously increased in treatments applied with bio-organic fertilizer, and the increases in soil fertility, urease and catalase activities were found in fluvo-aquic soil with the increasing bio-organic fertility application rates.

Abstract:In order to evaluate the application of water stress on peanut cultivation under different application amounts of biochar-based fertilizer, pot experiments were conducted in automatic canopy tanks to determine the effects of different water stresses (conventional water control, moderate water control, heavy water control, corresponding soil water contents were 70%～75%, 60%～65% and 50%～55% of field capacity, respectively) and different application amounts of biochar-based fertilizer (0, 750, 1 500 kg/hm2) on peanut yield, water consumption and nutrition absorption characteristics. The results showed that applying biochar-based fertilizer by 750 and 1 500 kg/hm2 could increase the contents ammonium nitrogen and available potassium in the top 15 cm soil, nitrogen and potassium absorption of above-ground plant as well as water productivity. Except heavy water control treatment, soil available potassium content, plant nutrition uptake and peanut yield were all increased in the other two water control treatments. In the treatment of moderate water control, compared with the treatment without biochar-based fertilizer, treatments of applying biochar-based fertilizer by 750 and 1 500 kg/hm2 could significantly increase the above-ground nitrogen and potassium uptake, increase peanut yield by 40.48% and 37.71%, and increase water productivity by 53.8% and 9.9%, respectively. These results could provide theoretical basis for the application of biochar-based fertilizer in peanut cultivation in arid area.

Abstract:The effects of irrigation schedule on photosynthetic characteristics and quality biological characteristics during different growth stages of isatisindigotica were studied in Yimin Irrigation District of Gansu Province in 2016. With the normal water condition in seedling stage and fleshy root maturity stage, the photosynthetic physiological characteristics and quality of Isatis were measured under mild, moderate and severe water deficit treatments in vegetative stage and fleshy root growth stage. The results showed that the leaf net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) of Isatis were decreased most significantly for Moderate and severe water deficit in vegetative nd fleshy root growth stages, and with the higher degree of water deficit, the greater the decrease. The comprehensive quality of WD5 was the best, the Indigo, Indirubin and (R,S)-goitrin contents of WD5 were 9.1%, 5.3%, 9.1% higher than CK respectively, quality of other treatments were improved moderately with the increasing in mild water deficit, but severe water deficit was not conducive to the accumulation of active ingredients. Therefore, water deficit?of Isatis under mulched drip irrigation reduced Pn, Gs and Tr, improved the water use efficiency, and mild-to-moderate water deficit was helpful to improving the quality of Isatis.

Abstract:A potato pot experiment was conducted to study the effects of potassium chloride coated by polymer (PCK) with different dosages on potato yield, quality and soil potassium (K) supply, which set six treatments: no potassium, potassium chloride, 30% PCK, 50% PCK, 70% PCK and 100% PCK dosage (with potassium chloride dosage equivalent). The results showed that the K released by 1.2% amount average of PCK in 25 ℃ water immersion, which met the controlled-release fertilizer industry standards. The K release rate was in “S” trend in the soil and reached the maximum value at 70～90 days, which was consistent with the potato potassium uptake in tuber formation period and beneficial to yield formation. The yields of potato were increased by 13.92%～36.54% under PCK different dosages compared with potassium chloride. The potato Vc, total soluble protein and starch contents of 100% PCK were significantly higher than that of potassium chloride, and the potato total reducing sugar content of 100% PCK was significantly lower than other treatments, the decreased amplitude was 13.9%～36.2%. The PCK released K slowly, which could meet the needs of the potato K uptake at later period. After the tuber formation period, potato K uptake amount of above 50% PCK dosage treatments were significantly higher than other treatments. Compared with potassium chloride, the content of soil available K content of above 50% PCK was significantly higher after the tuber formation period. At the same time, the soil water soluble K and non-specifically adsorbed K contents were increased by 8.4%～25.1% and 9.3%～36.1% respectively, so the soil K supply adequately. In conclusion, above 50% PCK dosage was beneficial to improve potato yield, commercial potato rate and quality, and increase soil K supply.

Abstract:In order to find out the suitable amount of nitrogen fertilizer for rapeseed in phytoremediation, a field experiment was conducted to study the effect of five nitrogen levels (0, 90, 120, 150 and 180 kg/hm2) on the yield, cadmium (Cd) uptake and accumulation of rape (Brassica campestris L.) (Xiangzayou 743 and Fengyou 682). Results showed that the application of nitrogen fertilizer significantly increased shoot biomass of rape. Compared with the control treatment, the shoot biomass of ‘Xiangzayou 743’ and ‘Fengyou 682’ was significantly increased by 473.9%～1 055.5% and 412.4%～1 164.6%, respectively. Nitrogen application increased the uptake of Cd by rape roots and the transport Cd from root to shoot. With nitrogen treatments, Cd concentrations in root of ‘Xiangzayou 743’ and ‘Fengyou 682’ were increased by 1.5%～21.9% and 6.0%～26.3%, respectively, while Cd concentrations in shoot increased significantly by 22.2%～82.8% and 19.5%～45.8%, respectively. Cd accumulation in shoot were increased significantly by 598.5%～1 912.4% and 518.6%～1 547.3%, and the Cd transfer coefficients increased by 1.7%～19.3% and 18.5%～65.1%, respectively. Cd concentration in roots was significantly negatively correlated with soil CaCl2-Cd concentration. The main reason for increasing Cd accumulation in shoot of rape was the increase of bioavailability and the transfer coefficient of Cd. Under this experimental condition, the suitable nitrogen application level for rape in phytoremediation was 150 kg/hm2.

Abstract:A field experiment was conducted to study the effects of partial?substitution for chemical?fertilizer?by?different organic?manure on the growth, yield, quality and nutrient use efficiency of watermelon under equivalent nutrients. Ten treatments were designed, including no fertilizer (CK), conventional chemical fertilizer (CF), chicken manure partial substitution for chemical fertilizer (CM), vermicompost partial substitution for chemical fertilizer (VC) and bio-organic fertilizer partial substitution for chemical fertilizer (BOF) under fumigating with dazomet or not. Results showed that organic manure partial substitution for chemical fertilizer could improve chlorophyll content, photosynthetic performance, yield and quality of watermelon with different degrees. Compared to CF, VC could significantly enhance the leaf photosynthetic performance of watermelon, and the plants under VC were the highest in watermelon yield, soluble sugar, soluble protein, ascorbic acid, i.e. 33.63%, 14.07%, 14.47% and 17.52% respectively, higher than CF. The fertilizer use efficiency was improved significantly under organic manure partial substitution for chemical fertilizer. After watermelon was harvested, the fertilizer utilization efficiencies of nitrogen, phosphorus and potassium in VC treatment were 26.02%, 5.67% and 29.89% respectively. On the other hand, the VC could obviously decline soil nutrient elements dependency, the dependent rate of soil nitrogen, phosphorus and potassium were 20.96%, 20.32% and 31.55% respectively. And biological fumigation had an inhibiting effect on Fusarium wilt disease incidence of watermelon, the disease incidence in VC under fumigation condition was only 4.76%, which was the lowest among all treatments.

Abstract:In order to explore the effects of different ecological management measures on soil carbon (C), nitrogen (N), phosphorus (P) content and their stoichiometry characteristics, thus to provide scientific evidence for ecological management and vegetation restoration of loess hilly region, by combining the means of field sampling and laboratory analysis, Wangmaogou which was the typical watershed in loess hilly region was taken as an example in this study, and the soil C, N and P contents and their stoichiometry of the 0—100 cm soil layer of 5 kinds of sample plots (sloping farmland, woodland, shrub land, grassland and terrace land) were analyzed. The results showed that: (1) Transformed into woodland, shrub land, grassland and terrace land by ecological management measures, soil C and N contents of sloping farmland respectively increased by 1.27, 1.18, 1.24, 1.14 times and 1.64, 1.64, 1.76, 1.57 times; There were significant positive correlation between soil C and N. The vertical distribution of the soil C and N in the 0—100 cm soil profile of woodland, grassland, shrub land and terrace land were quite consistent, showing the same trend of decreasing with soil depth and both appearing enrichment phenomenon in the 0—20 cm soil layer, while soil P did not change much with soil depth. (2) Soil C∶N mean value of sloping farmland was significantly higher than that of other plots (P＜0.05), while the surface soil C∶P of sloping farmland was significantly lower than that of other plots (P＜0.05). Soil C∶N did not change much, while soil C∶P and N∶P showed the trend of decreasing with soil depth. (3) The distribution of soil C, N and P stoichiometry was mainly determined by soil C and N. The correlations of soil C∶P, N∶P and ammonium nitrogen contents, soil clay contents, soil sand contents, soil water-stable aggregates were significant（P＜0.05）. Soil C, N, P contents and their stoichiometry were not only affected by ecological management and soil depth, but also were relevant to soil physical and chemical properties, meanwhile soil C∶N, C∶P and N∶P could indicate soil fertility level.

Abstract:In order to explore the seasonal variations of carbon (C), nitrogen (N) and phosphorus (P) stoichiometric features in leaves of different natural secondary forests and understand the strategies of plant adaptation to the environment, we chose Piuns tabulaeformis and Quercus liaotungensis natural forests in Ziwuling Forest district as study area, and subsequently investigated their C, N and P stoichiometric parameters in leaves from April to October. The results showed: (1) Leaf C, N and P contents and stoichiometric ratios of Q. liaotungensis were 43.16%, 2.10%, 0.19% and 25.47, 380.18, 14.49, respectively, and the same parameters for P. tabulaeformis were 48.06%, 1.15%, 0.11% and 42.58, 473.22, 11.02, respectively. There were less seasonal dynamics in leaf C contents and more seasonal dynamics in leaf P contents than others through the whole growth season. (2) Leaf C content of P. tabulaeformis significantly decreased from April to June, then remained stable, but it significantly increased from August to October, which was almost equal to April; while leaf C content of Q. liaotungensis was almost constant. Leaf N content of P. tabulaeformis remained stable before June, then significantly decreased from June to August, then it significantly increased from August, and in October it was almost equal to April. Leaf N content of Q. liaotungensis significantly decreased from April to June, then remained stable, but it significantly decreased again from August and reached the lowest value in October. Leaf P content of P. tabulaeformis remained stable before August, then significantly increased and reached the maximum value in October. Leaf P content of Q. liaotungensis significantly decreased from April to June, then remained stable. The changes of C/N, C/P of two species were averse to their N, P content. Leaf N/P of P. tabulaeformis significantly decreased from April to June, then significantly increased, and it significantly decreased from August to October. The N/P of Q. liaotungensis increased significantly and reached the maximum value before June and then significantly decreased. (3) Factorial analysis showed that leaf C content and C/N mainly determined by tree species. For other parameters, they were mainly affected by the interaction between tree species and month. (4) Leaf C content of P. tabulaeformis significantly higher than that of Q. liaotungensis, however, leaf N content of P. tabulaeformis was significantly lower than that of Q. liaotungensis, therefore, leaf C/N of P. tabulaeformis was significantly higher than that of Q. liaotungensis. However, leaf N/P of Q. liaotungensis was significantly higher than that of P. tabulaeformis. There was no significant difference in leaf P content and C/P between these two species. The coefficient of seasonal variation of leaf N, P contents and C/N, C/P, N/P of P. tabulaeformis were smaller than those of Q. liaotungensis. The results could enrich the study of ecological stoichiometry in natural forests, and provide a theoretical basis for the forest restoration and management in the hilly and gully region of Loess plateau.

Abstract:With maize as the research object, we conducted a pot experiment to firstly explore the soil improvement effects of desulfurization gypsum, vermicompost, sulfur, furfural residue and zeolite, then designed the appropriate combinations of ameliorants for both improving maize growth and soil properties. The results showed that the average pH value in the 0—20 cm soil layer with desulfurization gypsum, sulfur, furfural residue, vermicompost and zeolite treatments were decreased by 0.05～0.19 units under the slight saline-alkali conditions, and by 0.20～0.33 units under the moderate saline-alkali conditions, compared to the control treatment. In addition, desulfurization gypsum significantly reduced soil water-soluble Na+ content in the 0—20 cm soil layer. According to the improved characteristics of different ameliorants, two combinations ameliorants of T1 (desulfurization gypsum + sulfur + vermicompost) and T2 (vermicompost + zeolite + desulfurization gypsum + furfural residue) with comprehensive improvement effect were designed. These two combinations significantly increased maize biomass by 77.75% and 129.22% under the slight saline-alkali conditions, and by 148.13% and 170.31% under the moderate saline-alkali conditions, respectively. Meanwhile, they reduced the pH value of 0—20 cm surface soil. In conclusion, the application of the comprehensive ameliorants in coastal saline soils could promote crop growth and improve soil properties, which could be used as one of the important measures for the rapid improvement of coastal saline soil in the future.

Abstract:In order to study litter decomposition in Robinia pseudoacacia and Fraxinus velutina mixed forests with different ages in the Yellow River Delta, we selected 7 a, 12 a, 21 a and 30 a mixed forests to investigate litter decomposition characteristics by litter bag technique during two years. The results showed as following: (1)The decomposition coefficients of all mixed forests ranged from 0.44 to 0.60, and it followed the order of 30 a＞21 a＞12 a＞7 a; the half decomposition periods were 1.15～1.58 a and the decomposition periods were 4.96～6.83 a, and they followed the order of 7 a＞12 a＞21 a＞30 a; (2) Litter decomposition rate was significantly positively correlated with nitrogen content of litter, but negatively correlated with C/N ratio; there were significant differences in nitrogen content of litter among four mixed forests, and there was no significant difference in C/N ratio of litter between 12 and 21-year-old mixed forests, but the difference in this parameter between 7 and 30-year-old mixed forest was significant（p＜0.05）; (3) decomposition rate of litter was significantly positively correlated with soil organic matter and soil alkaline hydrolyzable nitrogen; there were significant differences in soil organic matter and alkaline hydrolyzable nitrogen among four mixed forests（p＜0.05）. These results suggested that with the increasing of forest age, the nitrogen content of litter increased, the C/N ratio decreased, and the litter decomposition rate accelerated.

Abstract:In order to reveal the water consumption characteristics of dominant species-Populus beijing ensis in the arid area of north-west Hebei, the stem flow characteristics of different health grades were studied by thermal diffusion stalk instrument. Meanwhile, meteorological factors, water factors and individual growth status were referred to analyses the driving forces. The results show that there were obvious diurnal changes both in the sunny and cloudy days, the stem flow started early and stopped late in the sunny. The contribution rate of nighttime water consumption of healthy Populus beijing ensis was 2.5%～5.6%, while the contribution rate of unhealthy nighttime water consumption was 8.37%～21.20%. The water consumption of Populus beijing ensis in different health grades were significant different (P＜0.01). The daily average water consumption of unhealthy plants was 22.95±5.99 L, which was only 27.9% of healthy plants. It was positively correlated with solar radiation, air temperature, saturated vapor pressure, and negatively correlated with relative humidity specific, air temperature and relative humidity were the most important. There were timelags between the sap flow in stems and the meteorological factors, the stems flow of health and sub-health individual occurred behind the solar radiation 0.5 h, while ahead of the air temperature, humidity, saturated vapor pressure difference 1 h. For Unhealthy individual, it kept pace withair temperature, humidity and saturation vapor pressure,while behind the solar radiation 1 h. Water consumption of healthy, sub-health and unhealthy individuals of of Populus beijing ensis were 11 636.1, 7 254.8 and 425.4 L, respectively. The precipitation of 232.2 mm could not meet the water consumption. It has a stress effect and influences on the grow of Populus beijing ensis because of the lack of water.

Abstract:In order to explore the adaptability of Polygonum capitatum to different understory light conditions, the photosynthetic characteristics and chlorophyll fluorescence parameters of P. capitatum grew in forest gap (FG), under forest canopy (FC) and in forest transition zone (FT) were examined, meanwhile, the response of photosynthetic capacity and chlorophyll fluorescence parameters to different photo intensities were analyzed. The results showed that the apparent quantum yield (AQY) of P. capitatum were higher in FG (0.028) and FC (0.023) than in FT (0.019). There was little difference in light compensation point among three habitats（35.00～66.77 μmol/（m2·s））. The light saturation point (LSP) and the maximum net photosynthetic rate (Pn) were both lower in FG (808.45 μmol/(m2·s), 6.24 μmol/(m2·s)) than those in FT (1 201.43 μmol/(m2·s), 8.86 μmol/(m2·s)) and FC (1 780.42 μmol/(m2·s), 13.72 μmol/(m2·s)), whereas dark respiration rate (Rd) was higher in FG (1.97 μmol/(m2·s)) than those in FT (0.80 μmol/(m2·s)) and FC (1.67 μmol/(m2·s)). The maximum photochemical efficiency of PSII (Fv/Fm) and potential PSII activity (Fv/F0) were both higher in FC (0.803, 4.08) than those in FG (0.801, 0.402) and FT (0.785, 3.65). The yield of photosystem II (φPSⅡ) and photochemical quenching (qP) decreased with increasing of light intensity, whereas the electron transport rate (ETR) and non-photochemical quenching (NPQ) increased. P. capitatum adapted weak light condition under forest by reducing dark respiration rate and improving the photochemical efficiency. At the same time, P. capitatum reduced the qP and increased NPQ to avoid light damage under the bright light conditions. These features of P. capitatum indicated that it has good light adaptability.

Abstract:In this paper, we adopt servo-type strong machine to research the material mechanical properties of straight roots of Artemisia ordosica which is one of the dominant species in the coal mining subsidence area of Ordos. Results showed that the anti-tension force and the anti-fracture force of straight roots of Artemisia ordosica were positively correlated with the diameter of roots with a power function and both of the anti-fracture strength and the anti-fracture strength were negatively correlated with the root diameter with a power function in the 1～5 mm diameter range. Under the action of tension force and fracture force, the straight roots’ ultimate anti-tension elastic force was greater than the ultimate anti-fracture elastic force and its axial elastic deformation was smaller than the radial elastic deformation, it showed the characteristics of elasto-plastic deformation. The σ (stress)—ε (strain) curve under fracture force and tension force of the straight roots were concave and convex respectively, the ultimate strength decreased with the increase of root diameter, and the ultimate strain had no correlation with root diameter under these two kinds of force. The average anti-tension strength of the straight roots was greater than the average anti-fracture strength ((8.32±1.67)Mpa＞(5.39±0.85)MPa) in the 1～5 mm diameter range, it showed that the ability of the straight roots to resist axial tension elastic was better than the ability to resist radial fracture force.