Abstract:Gully erosion is one of the significant soil erosion types and it is the key sediment source in small watershed. It is the foundation to analyze and summarize the dynamic processes of gully formation and development, geometry properties, measuring methods and prediction models for demonstrating the dynamic mechanism of gully erosion, gully control and land resource conservation. The concepts of gully and gully erosion, geometry properties and measuring methods, the key influencing factors, the dynamic processes of gully development, and erosion models were fully reviewed. The concepts were clarified and different methods for gully monitoring were compared. The key factors affecting gully formation and development were quantified. The dynamic mechanism were identified for each sub-process of gully erosion. The structure and main influencing factors of representative gully erosion models were compared. The urgent issues need to be studied in the future were proposed. This review paper is helpful for understanding the generation of gully erosion and the dynamic processes of gully development, promoting the effectiveness of gully erosion control.

Abstract:In order to realize the ecological restoration of sandy river course in Beijing section of Yongding River, through the field runoff plot drainage and scour test, the effects of different ecological riverbank protection measures on hydrodynamic characteristics, runoff and sediment yield during slope erosion process were studied. In the test, five kinds of bank protection materials (ecological bag, coir blanket, 3D-geomat, pine pile and pebble) were used, and the runoff and sediment yield of each treatment were analyzed under three kinds of water discharge flow rate (0.5, 1.0 and 1.5 m³/ h) and 10° slope. The results showed that: (1) Under the three release flows, the average runoff velocities of the five bank protection materials were all smaller than that of the bare slope, and the average runoff velocity of the five ecological bank protection materials followed the order of pebble > pine pile > 3D-geomat > ecological bag > coir blanket. The Froude numbers of the five ecological bank protection materials were all less than 1, and the Reynolds numbers were all less than 500. (2) Ecological riverbank protection measures could effectively intercept runoff and slow down the runoff production process, and the runoff production showed a significant logarithmic increase trend with time. The average runoff interception rate of the five ecological bank protection materials followed the order of ecological bag > coir blanket > 3D-geomat > pebble > pine pile. (3) The average sand production rate on the slope surface increased with the increasing of water discharge flow, and the ecological bank protection measures could effectively intercept the slope sand production, and the sediment interception effect of ecological bank protection material gradually decreased with the increasing of the water discharge flow. The research results were of great significance for the bank slope management of different sections of the Yongding River, the selection of ecological bank protection materials, and the construction of the green corridor of the Yongding River, and also provided a reference for the quantitative evaluation of the water and sediment reduction benefits of different bank protection materials.

Abstract:Under the background of global climate change, the frequency of extreme rainstorm events increases. It is of great significance to study the formation mechanism of flood peak in small watershed for rainstorm flood prediction, disaster prevention and mitigation. Based on the extraordinary rainstorm event caused by Typhoon "Lekima" in Linqu County, Weifang City, Shandong Province in 2019, 17 small watersheds near the rainstorm center were selected, and the response characteristics of the flood peak intensity and sensitivity of the small watersheds to the vegetation and terraces were studied by the methods of field investigation, remote sensing interpretation and correlation analysis. The results showed that in this rainstorm event, the peak discharge of small watershed was 2.36~56.50 m³/s, the peak modulus was 8.00~48.89 m³/(s·km²), and the flood index was between 3.61 and 4.55. Under the condition of similar rainfall, the flood peak modulus, flood index K had significant positive correlation with proportion of sloping farmland (p<0.05), and the flood peak modulus had a significant negative correlation with the proportion of forest grassland and terrace (p<0.05), the flood index K had negative correlation with the proportion of forest grassland and terrace. With the increasing of individual rainfall, the influence of vegetation and terraces on flood peak in small watershed presented a nonlinear feature of increasing first and then decreasing. Under the condition of extreme rainstorm, the sensitivity of surveyed watershed to flood was "Average". The ability of small watershed to cope with extreme rainstorm could be improved by increasing the area of forest, grassland, terrace and other land types.

Abstract:Mountainous area accounts for about 94% total land area of Yunnan province. The special topographical characteristics can easily cause slope soil erosion and nutrient loss, which seriously affects agricultural sustainable production. It is necessary to take effective agronomic measures to reduce soil nutrient loss in sloping land. Based on the 4-year experiment, compound agronomic measures for two tillage directions, vertical ridge (VR) group (2 treatments) and horizontal ridge (HR) group (2 treatments) were in location monitoring. Results showed that runoff generation time of red soil on slope land in Yunnan was mainly from June to September, and the rainfall of producing runoff accounted for 65.62%~75.82% of the annual precipitation. The rainfall of producing runoff had same trend with annual precipitation. The relationship between rainfall of producing runoff and runoff depth were linear (R_NVF²=0.597 7,R_OVF²=0.415 1,R_OHF²=0.378 2, R_OHFR²=0.335 5).The correlation order was that vertical ridge (VR) group was greater than horizontal ridge (HR) group, non-fertilizer application treatment was greater than fertilizer application treatment, and mulching treatment was greater than the mulching removal treatment (P<0.01). Heavy rain and rainstorm caused most of the annual runoff and nutrient loss. Surface runoff produced by HR tillage was (177.13±28.87) to (182.28±33.75) mm, TN (7.66±2.51) to (7.85±1.92) kg/hm², TP (0.91±0.26) to (1.09±0.27) kg/hm². Average reduction rate (ARR, %) of runoff and nutrients were 49.57% to 52.13% and 33.16% to 53.88% significantly, compared with conventional treatment (OVF) of VR tillage group(P<0.01). Under different tillage measures, OHFR had best effect of intercepting runoff and nutrient losses. The results of RDA analysis show that compared with rainfall, runoff was the main environmental factor affecting the change of nitrogen and phosphorus nutrient (P<0.01). The correlation between runoff and the nitrogen nutrient loss (except NH₄⁺-N) was higher than that of phosphorus, which indicating nitrogen was more easily loss with runoff than phosphorus. NVF and OVF treatments of vertical ridge (VR) group were positively correlation with environmental factor runoff and nutrient losses of TN、TDN、NO₃^--N、NH₄⁺-N、TP、TDP, while OHF and OHFR treatments of horizontal ridge (HR) group were negatively correlation with it.

Abstract:Freeze-thaw has an important effect on wind erosion by changing soil physical properties in the agricultural field of Chinese Mollisol region in late spring. The research analyzed the effects of previous freeze-thaw on wind erosion in agricultural fields based on simulated freeze-thaw and wind tunnel experiments. The experimental treatments included three initial soil moisture contents (16.5%, 24.8% and 33.0%), three wind speeds (9, 12 and 15 m/s), one freeze-thaw cycle, and non previous freeze-thaw experimental treatment was taken as a control. During the experiment, the soil box filled by tested soil samples with different initial moisture contents was firstly placed in the refrigerator to simulate freezing and thawing effect, and then it was air-dried in room temperature until its soil moisture content was approximately 6.0% to 7.0%. Late on, the soil box was placed into the wind tunnel to simulate soil loss by different wind speeds, respectively. The results showed that previous soil freeze-thaw significantly increased wind erosion rate and sediment delivery rate. At the experimental conditions, wind erosion intensity increased by 23.5%~404.2% (P<0.05), and the average sediment delivery rate increased by 59.1%~305.3% (P<0.05), compared with the control treatment; and both increments were related to initial soil moisture content and wind speed. Meanwhile, the wind erosion and sediment delivery rates increased significantly with an increase of wind speed with/without previous soil freeze-thaw action, and the wind erosion intensity followed the power function with increasing of wind velocity. For the previous soil freeze-thaw treatment, the order of increments of wind erosion and sediment delivery rates under three initial soil moisture contents was 16.5% > 33.0% > 24.8%. Moreover, the sediment delivery rate decreased exponentially with an increase of surface height, the wind erosion material was mainly concentrated in the range of 40 cm above the surface; and the previous soil freeze-thaw action increased the sediment delivery height.

Abstract:In order to further study soil erosion mechanism of sloping farmland in low mountain and hilly region of western Liaoning Province, we selected cinnamon soil and brown soil as research object, periodic variation of water and sediment in rill erosion was studied under three slopes (5°, 10° and 15°) and three rainfall intensities (40, 60 and 80 mm/h) by using artificial simulated rainfall system. The results showed that the erosion process of cinnamon soil and brown soil slope could be divided into three stages, which were the pre-rill erosion stage, the development of drop sill stage and the rapid development of rill erosion stage. At the surface erosion stage before rill erosion, the flow velocity of cinnamon soil and brown soil increased with the increasing of rainfall intensity under the same slope condition. However, the effect of slope on flow velocity was not obvious under the same rainfall intensity. At the rill erosion stage, the flow velocities of in and between rills of cinnamon soil and brown soil increased with the increasing of rainfall intensity under specific slope. The flow velocity between rills of cinnamon soil and brown soil increased with the increasing of slope gradient under specific rainfall intensity. At the rill erosion stage, the flow velocity followed the order of in rill > on slope > between rills. At the rapid development of rill erosion stage, the runoff of cinnamon soil and brown soil accounted for more than 80% of the total runoff, and the soil erosion accounted for more than 70% of the total erosion. The contribution of brown soil to total erosion was more stable, and rill erosion was more likely to occur. The erosion pattern of the whole rainfall was the transformation from surface erosion to rill erosion. Once slope surface erosion occurred, rill erosion contributed more to the total erosion.

Abstract:In order to explore the applicability of plant fiber blankets and its soil and water conservation benefits with different plant growth periods in the hilly and gully regions of the Loess Plateau, an artificial rainfall simulation experiment was conducted in Qingshuihe County, Inner Mongolia, to study the runoff and sediment yield in direct-seeded herbaceous slopes and plant fiber blanket slopes with 58, 81 and 132 days plant growth periods. The results were as follows: (1) Plant fiber blanket slope protection measures could significantly extend the slope runoff time, and the runoff time increased with the increases of plant growth periods. When the plant growth period was 58, 81, 132 days, the plant fiber blanket slope runoff time was 86, 110, 243 s, which was significantly longer than the bare slope (50, 70, 111 s) and the direct-seeded herbal slope (73, 83, 123 s). (2) With the increases of plant growth periods, the runoff of the slope of plant fiber blanket decreased from 13 125 mL to 5 478 mL; sediment yield decreased from 73 g to 22 g; the runoff of the direct seeding herb slope decreased from 25 573 mL to 14 340 mL, and the sediment yield decreased from 201 g to 82 g. (3) The runoff reduction of plant fiber blanket slope protection measures were 55%~78%, and sediment reduction were 71%~89%. (4) Slope vegetation height and coverage were the main factors affecting runoff and sediment yield in vegetation growth conditions. There were multivariate linear functions relationships among runoff, sediment yield, height and coverage. The plant fiber blanket could effectively reduce soil erosion and reduce runoff in the gully slope of loess hilly and gully region.

Abstract:Taking Manshuihe watershed, Beijing as the research object, the characteristics and abrupt change point of the annual precipitation and runoff coefficient from 1956 to 2016 were analyzed. Principal Component Analysis was used to analyze the influence of hourly rainfall and annual rainfall on annual runoff coefficient based on runoff coefficient under the underlying surface condition of 2000-2016. A linear principal component regression model and BP neural network model based on LM Algorithms for annual runoff coefficient and main rainfall factors was established. The results showed that annual runoff coefficient had been declining significantly in the past 61 years, and had three sharp downward trends from 1956 to early 1970s, late 1970s to late 1980s, 2000 to present. The short-term rainfall had a great influence on annual runoff coefficient under the current underlying surface. The correlation coefficient, Mean Absolute Error (MAE) and Root Mean Squared Error (RMSE) were 0.99, 0.002 6 and 0.005 respectively between annual runoff coefficient predicted by neural network model and measured value. Compared with regression model, the neural network model gave a better result in simulating annual runoff coefficient.

Abstract:This paper studied the differences and variation of soil anti-erodibility between sedimentation zone in front of hedgerows and ridge behind hedgerows on purple soil slopping land. We collected soil samples form three runoff plots (10° Leucaena leucocephala hedgerows plot (T1), 10° and 15° Vetiveria zizanioides hedgerows plots (T2 and T3)). These plots were selected from Soil and Water Conservation Experimental Station in Suining as the research object. The plots were provided with up, middle, and down hedge belts, and surface soil samples from the zone in front of hedgerows and ridge behind hedgerows were collected to determine the organic matter content, water-stable aggregates and micro-aggregate composition. Combined with the principal component analysis, we obtained the following results: The soil organic matter content, degree of aggregation and state of agglomeration of sedimentation zone in front of hedgerows were better than those of ridge behind hedgerows in the same hedge, and water stable aggregate content and the comprehensive index of soil anti-erodibility were opposite. The comprehensive index of soil anti-erodibility of ridge behind hedgerows was 1.48~3.17 times higher than that of sedimentation zone in front of hedgerows. The organic matter content, degree of aggregation and state of agglomeration of sedimentation zone in front of hedgerows showed the largest in the down slope, followed by the middle slope, and the smallest in the up slope, while that of ridge behind hedgerows showed the largest in the up slope and followed by the middle slope, and the water-stable aggregate content and the comprehensive index of soil anti-erodibility had no significant difference between the slope positions. In the same slope position, the soil organic matter content, degree of aggregation, state of agglomeration and water stable aggregate of Vetiveria zizanioides hedgerows plot were better than that of Leucaena leucocephala hedgerows plot. The higher the slope, the worse the soil organic matter content, status of agglomeration and water stable aggregate in Vetiveria zizanioides hedgerows. It was discovered by principal component analysis that the index of water stable aggregate could better reflect the strength of soil anti-erodibility in purple soil slopping land, and the best soil anti-erodibility was given by T2, followed by T1 and T3 in sequence.

Abstract:Karst valley area is prone to soil and water loss during rainfall, which destroy the ecological environment of the area. This study taken the karst valley area as the research object, through indoor simulation of its typical bedding/inverse layer slope characteristics and the development degree of underground hole crack and using artificial rainfall test, the characteristics of the surface underground runoff production under different rainfall conditions were studied, thereby revealing the production mechanism of surface and underground runoff in karst valley. The results showed that: (1) The surface underground runoff yield and discharge in the karst valley area was affected by rain intensity, and the underground runoff yield and discharge was greater than the surface runoff under light rain (30 mm/h), and the surface runoff yield and discharge increased under moderate rain (60 mm/h), meanwhile it was greater than underground runoff under the condition of large and bare slope. Under the condition of heavy rain (90 mm/h), the surface runoff yield and discharge were both greater than the underground runoff on bare slope and bedding slope. (2) The development degree of underground pore fissures impacted the distribution ratio of surface underground runoff yield and discharge. The larger the degree of underground pore fissure was, the greater the underground runoff yield and discharge would be, and the distribution proportion of surface underground runoff yield and discharge would change when the underground hole fissure degree was 2%~3%. (3) Under different strata tendencies, the surface runoff yield and discharge and its distribution ratio were the highest on bare slopes, and the lowest on reverse slopes, while the underground runoff yield and discharge and its distribution ratio were the highest on reverse slopes, and the lowest on bare slopes. (4) Under different strata inclination angles, the surface runoff yield and discharge was the maximum on the bedding layer of 30°, and the lowest on the bedding layer of 90°, while the underground runoff yield and discharge was opposite. For the reverse slope, the surface runoff yield and discharge was the maximum on the slope of 90°, and the minimum on the slope of 60°, the underground runoff yield and discharge was the highest on the slope of 60°, and the lowest on the slope of 90°. The results could provide scientific basis for further understanding of the production mechanism of surface and underground runoff in the karst valley area.

Abstract:In order to control soil and water loss of sloping land in Earth-rocky Mountainous Area in North China, and to propose the optimal layout pattern of slope grass belt was put forward, the typical soil limestone parent material developed cinnamon soil in this area was taken as the research object. Under the condition of 9° slope and 90 mm/h rainfall intensity, the indoor artificial rainfall test was used to analyze the layout pattern of grassland filter belt (upslope, downslope, sheet, strip) on the slope The results showed that: (1) The strip layout under the slope could effectively delay the initial runoff generation time of the slope, which was 1.3~1.6 times longer than the other three layout. And the strip layout under the slope could increase the runoff inflow and infiltration of the slope and reduce the runoff generation. As for the cumulative discharge, the upslope > strip > sheet > downslope. (2) The cumulative sediment yield under the arrangements on the slope was 10~23 times that under the arrangement on the slope. The sediment yield under the arrangement on the slope fluctuated obviously with time, and the sediment yield under the arrangement on the slope was 3~35 times that under the arrangement on the slope. The sediment reduction was the best when the grass filter belt was laid under the slope. (3) The layout under the slope could inhibit the development of rill erosion, and the strip layout under the slope could effectively control the number and length of rills, and the benefit of slope protection was the best.

Abstract:Rainfall simulation experiments were conducted to study the effects of different residue coverage on soil and water conservation of the black soil on 4° slope. Three parallel conditions were set up in the experiment, which were five residue coverage (bare, 15%, 35%, 55% and 75%), four rainfall intensities (30, 60, 90 and 120 mm/h), two initial soil moistures (8% and 30%, corresponding to dry and wet operation). The results showed that residue cover had positive effects on reducing the soil erosion and the runoff and sediment production of the black soil, and the higher the coverage, the more obvious the inhibition. The water conservation benefits under the 15%, 35%, 55% and 75% residue coverage could reach 30%, 27%, 57% and 72%, respectively. The soil conservation effects under the four residue coverages could reach 36%, 53%, 89% and 94%, respectively. Exponential functions were established between the soil and water conservation benefits and the residue coverage. Compared with the water conservation benefit, the soil conservation benefit of residual cover was more obvious. Residue cover could not only increase the nutrient contents, but also an effective way for the black soil protection.

Abstract:In the field plot experiment of the Chaohu Paihe small watershed, four treatments, including T1 (conventional compound fertilizer), T2 (bio-organic fertilizer replacing 30% nitrogen fertilizer), T3(loss-of-control fertilizer replacing 30% nitrogen fertilizer), and T4 (bio-organic fertilizer and loss-of-control fertilizer replacing 15% nitrogen fertilizer respectively) were set up to study the effects of dynamic changes of nitrogen and phosphorus concentrations in the surface water, nitrogen and phosphorus loss in the runoff, and rice yield under several different fertilization modes. The results showed that the average concentrations of total nitrogen and total phosphorus in the surface water of treatment T1 were 10.30 and 0.45 mg/L, respectively. Compared with treatment T1, the average concentrations of total nitrogen in the surface water of treatment T2, T3, and T4 decreased by 12.2%, 6.5%, 5.3%, the average concentrations of total phosphorus in the surface water decreased by 26.7%, 15.6% and 13.3%, respectively.The total loss of total nitrogen and total phosphorus in the runoff with treatment T1 reached 17.68 and 1.60 kg/hm². Compared with treatment T1, the total loss of total nitrogen in the runoff of treatment T2, T3, and T4 decreased by 35.0%, 30.8% and 25.5%, the total loss of total phosphorus in the runoff of treatment T2, T3, and T4 decreased by 16.3%, 21.9% and 22.5%, respectively. The yield of grain of treatment T1 was 8.95 t/hm². The yields of treatment T2 and T4 increased by 7.8% and 6.5%, respectively, showing a significant difference with T1. The yield of treatment T3 decreased by 2.2% compared with T1, and the difference was not significant. The experimental results show that compared with treatment T1(conventional compound fertilizer), T2(bio-organic fertilizer replaces 30% nitrogen fertilizer), and T4(bio-organic fertilizer and loss-of-control fertilizer replacing 15% nitrogen fertilizer respectively) can significantly increase crop yield, and at the same time, reduce the risk of nitrogen and phosphorus loss from paddy fields effectively. The research results provide a theoretical basis for the prevention and control of non-point source pollution in rice fields of Chaohu Basin.

Abstract:Soil erosion and its induced rocky desertification, as the most serious ecological problem in Karst Plateau, is the biggest obstacle and threat to the construction of ecological civilization. In this study, taking a typical karst plateau mountainous City, i.e. Guiyang City, as the object, using RUSLE model, adopting the global and local spatial autocorrelation, and Getis—Ord G_i^* methods based on Exploratory Spatial Data Analysis (ESDA—GIS), the soil erosion of Guiyang City in 2008, 2013, and 2018 was assessed. The spatial-temporal distribution and changes were analyzed, and the impact of vegetation coverage factor and rainfall factor on the change of soil erosion was revealed. The results showed that: (1) The soil erosion of Guiyang City was effectively controlled from 2008 to 2018, and the average soil erosion modulus decreased from 819.11 t/(km²·a) in 2008 to 70.14 t/(km²·a) in 2018. The soil erosion intensity was mainly slight erosion at present, showing a deterioration trend in 2013—2018. (2) The spatial distribution and evolution of soil erosion in Guiyang City displayed an obvious spatial aggregation effect. The Global Moran’s I index ranged from 0.125 to 0.280, but the aggregation trend was characterized by "overall weakening and small diffusion". The erosion hotspots was mainly distributed in Qingzhen City, Huaxi District, Kaiyang County and Xiuwen County, as well as areas with an altitude of 1 200~1 300 m or a slope of 8°~15°. (3) The contribution of vegetation cover factor to the changes of soil erosion area was about 74%~92%, which was the leading and controlling factor of soil erosion, while the contribution of rainfall erosivity factor was only about 7.5%~26.0%. This research could provide the important scientific basis for the comprehensive control of soil erosion and rock desertification, the optimization of land space, and the construction of ecological civilization city in the Karst region.

Abstract:The loss of soil phosphorus has become an important threat to the eutrophication of surface water. Red soil is widely distributed in China, and its distribution area is large. The study on phosphorus accumulation and loss in red soil can provide scientific basis for controlling agricultural non-point source pollution and preventing regional surface water pollution. In this study, 5 common land use patterns including pasture, leisure land, dry land corn, vegetable land, and greenhouse were selected, and using artificial rainfall simulation method, the forms of phosphorus accumulation, the characteristics of phosphorus transfer with surface runoff and the environmental threshold under different land use types in red soil region were studied. The result showed that: (1) Soil Olsen-P contents of red soils ranged from 6.81 to 178.17 mg/kg, CaCl₂-P contents ranged from 0.29 to 8.26 mg/kg, and NaOH contents ranged from 30.34 to 369.81 mg/kg, P accumulated in red soil among the different land use patterns; (2) The PSI ranged from 31.95 to 47.05 in red soil under different land use patterns, and the mean values were as follows: Grassland > Corn field > Vegetable field > Leisure area > Greenhouse; (3) The concentration of TP in surface runoff of red soil was 0.245~2.073 mg/L, TDP was 0.023~0.308 mg/L, and PP was 0.223~1.826 mg/L under different land use patterns. The average concentrations and losses of TP and PP in surface runoff of different rainfall events were consistent with the Olsen-P content in the soil surface layer, the average concentrations and losses of TDP in the order of greenhouse > Vegetable field > Corn field > Grassland > Leisure area and Greenhouse > Vegetable field > Grassland > Leisure area > Corn field, respectively. PP was the dominant form of TP in runoff under different land use patterns, which account for 82.46%~90.15% of TP; (4) There was a very significant positive correlation between soil Olsen-P and NaOH-P and CaCl₂-P. As the content of Olsen-P increased, the NaOH-P and CaCl₂-P increased, and there was an obvious "Change-point", 36.17 mg/kg was determined as the red soil phosphorus environmental threshold. It was also pointed out that there was a significant positive correlation between the runoff TP concentration or loss and soil NaOH-P content.

Abstract:Based on the centimeter-resolution Unmanned Aerial Vehicles (UAV) image, the Object-Based Image Analysis (OBIA) was applied to identify the soil and water conservation (SWC) measures, including contour ridges, ridge plants, ecological restoration forest, ecological restoration grassland, in the Chuanzigou catchment of Yitong district, Jilin province. Spectral indices including Excess Green Index (ExG), Excess Red Index (ExR), Normalized Difference Index (NDI), shape features including principal direction and shape index, and texture features including mean, variance and contrast were used to extract the features of SWC measures. Finally, the overall accuracy and Kappa coefficient of the identification of SWC measures in the study area was 91.24% and 0.87, respectively. The overall accuracy of the identification of linear SWC measures such as ridges and ridge-furrows was 72.33% with a Kappa coefficient of 0.63. The research showed that the centimeter-resolution UAV image, combined with the OBIA methods had the ability to accurately identify SWC measures in black soil area. They can also identify linear measures such as ridges and ridge-furrows automatically. The research can provide a reference basis for the dynamic monitoring of the implementation scope and integrity of SWC measures.

Abstract:To explore the change characteristics of rill flow velocity on the soil-rock mixed colluvial deposit, the scouring experiment was carried out. Four flow rates (2, 4, 8, 12 L/min) and four gravel mass contents (0, 10%, 30% and 50%) were set up. The change characteristics of rill flow velocity on the soil-rock mixed colluvial deposit were analyzed, and the response of flow velocity to flow rate and gravel content was studied. The results showed that the velocity decreases exponentially with scouring time, and the velocity attenuation trend of pure soil is larger than that of gravel-containing slope. The velocity of flow increased as a power function with the increase of flow velocity and decreased as a logarithmic function with the increase of gravel content. The effect of flow velocity and gravel content on flow rate was significant, and the effect of flow rate was greater than that of gravel content. Flow rate can be expressed by binary logarithm of flow rate and gravel content (NSE=0.78). The research results deepen the understanding of hydrodynamic process of rill erosion on colluvial deposit slope.

Abstract:Preferential flow is a rapid infiltration form of soil moisture which occurs widely in paddy fields. This paper concentrated on typical farmland of paddy fields with straw mulching and non-cover conditions in the Karst region of Guangxi, using the methods of brilliant blue dye and the morphological image analysis technology to present the soil preferential flow features of two tillage types. The results showed that under the same water supply condition, the soil dyeing morphology of straw mulching paddy fields was mainly uniformly distributed, while the non-mulching conditions paddy fields showed obvious branch-like dyeing morphological and throughout the soil space. The average dyed patch shape coefficient of non-mulching conditions paddy field was 13.96, and the dyeing morphology showed a significant irregular differentiation. The average distribution density of dyeing water in soil space was 0.117, which was larger than that straw mulching paddy field, showing a concentrated distribution condition of dyeing water. The soil infiltration capacity of straw mulching field was higher than that of non-cover conditions paddy field, with its the average total dyeing area ratio was 46.69%. There was significant difference between them (P<0.05). But the time rate of preferential flow of straw mulching paddy field was later than the non-mulching conditions paddy field, which the average matrix flow depth was 16.92 cm. The preferential flow fraction of straw mulching paddy field was 27.47% less than the straw mulching rice paddy (49.55%). There was significant difference between them (P<0.05). Straw mulching method can affect the process of soil water movement in the field. At the same time, its increase the amount of water infiltration in the field to a certain extent and reduce the occurrence of preferential flow. Compared with the non-cover conditions of paddy field, the straw mulching method also promote the maintenance of soil water in the paddy field, and reduce the loss of water and fertilizer in the field.

Abstract:Karst depression is a common landform type in karst areas of Chongqing. Small depression watershed is an important place for agricultural activities. Studying the characteristics of erosion and sediment yield of different land uses in the watershed is of great significance for understanding the laws of erosion and sediment production and controlling soil and water loss. A small karst depression basin with a reservoir was selected, and 39 geochemical properties of the sediment source as well as sediment samples were analyzed. The composite fingerprint and multivariate mixed model were used to calculate the erosion and sediment contribution rate of each sediment source. The results showed that the best fingerprint factor combination screened by the catchment was U, χ_lf, Rb, Li, ¹³⁷Cs, χ and Mn. The cumulative rate of correct discrimination was 99.93%, and the total correct discrimination rate of the six sediment sources was 91.49%, which accorded to the application conditions of compound fingerprint method. The relative contributions to sediments in the basin of carbonate arable land, carbonate woodland, carbonate grassland, clastic rock forest, clastic grassland and trench/fissure soil were 16.29%, 41.16%, 13.03%, 16.67%, 4.48% and 8.37%, respectively, the goodness of fit of the model was 93.57%, and the average relative error was 8.26%, indicating that the model result was credible. Among all sediment source areas, the sediment contribution per unit area of carbonate rock farmland was far higher than that of other sediment source areas, which was 1.98 times that of carbonate forest land, 2.07 times that of carbonate grassland, 2.13 times that of clastic rock forest land, and 2.21 times that of clastic rock grassland. The soil corrosion resistance of carbonate rock farmland per unit area was the weakest.

Abstract:Vegetation is an important factor affected soil organic carbon content and soil aggregate stability. In this study, the soil of runoff plots in four vegetation types, which were wasteland, Eucalyptus forestland, Slash pine forestland and Schima superba forestland in the typical granite erosion region of south China, was selected as the research objects. The characteristics of soil organic carbon and aggregate stability in different slope positions and soil depths were analyzed, and the effects of different vegetation types on the distribution characteristics of soil nutrients and the soil aggregates stability were evaluated. The ideal ecological restoration measures for granite erosion and degradation region was identified, so as to provide a scientific basis for the rational use of soil, reconstruction of slope vegetation and the maintenance of soil structure stability. The results showed that the content of soil total organic carbon (TOC), total nitrogen (TN) and dissolved organic carbon (DOC) gradually decreased with the increasing of soil depth, while the soil C/N ratio in the forestland plots was opposite, and the slope coefficient of variation (CV) of carbon and nitrogen elements in the wasteland plot was significantly higher than those in the other three kinds of forestland, among them, the CV in slope distribution of TOC, TN, DOC and C/N in Eucalyptus forest land was 40%, 56.18%, 68.5% and 25.81% lower than those in wasteland; the CV of the slope distribution of TOC, TN, DOC and C/N in Slash pine forestland decreased by 62.73%, 33.71%, 46.46% and 58.06%, respectively, compared to the wasteland; the CV in slope distribution of TOC, TN, DOC and C/N of S. superba decreased by 41.82%, 38.2%, 51.18% and 48.39%, respectively, compared to the wasteland, indicating that the forestland was more conducive to the accumulation of soil carbon and homogenization of nitrogen and carbon on the slope. The mass fraction of aggregates above 0.25 mm grain size on the upper and middle slopes in the grassland and S. superba forestland were significantly higher than that in other vegetation types, while the mean weight diameter (MWD) and geometric mean diameter (GMD) of the S. superba forestland with high biomass of understory vegetation were significantly higher than those of other vegetation types. The MWD of S. superba forest was 20.10%, 19.58% and 23.20% higher than that of wasteland, Eucalyptus and Slash pine forest, respectively; the GMD of S. superba forest was 20.00%, 19.54% and 22.23% higher than that of wasteland, Eucalyptus forest and Slash pine forest, respectively, which indicated that the forest grass model with better spatial structure of forest and grass in the granite erosion region was more conducive to accumulation of soil organic carbon and the stability of soil structure.

Abstract:Vegetation can effectively improve the stability and erosion resistance of shallow slope. In order to make a preliminary quantitative assessment of dynamic changes of vegetation slope consolidation under natural conditions in the loess hilly and gully region where the shallow landslide prone to occur, taking Robinia pseudoacacia, the main afforestation tree species in the loess hilly and gully region as an example, the dynamic changes of roots mechanical and hydrological effects of vegetation slope consolidation under natural conditions in 2017 were studied. The roots cross-sectional area distribution was investigated by digging the root section, the roots tensile strength was tested by single root tensile test, and the roots additional cohesion of R. pseudoacacia was calculated by using the Wu model. Field surveys were conducted to collect the parameters related to the hydrological effects of vegetation and the research plot. Laboratory infiltration experiment and soil centrifugation experiments were conducted to obtain the soil hydraulic parameters. Then the water transport software Hydros-1D was applied to do the transient analysis of the water content of the R. pseudoacacia slope. Finally, the stability of the slope was analyzed based on the infinite slope model under variable saturation conditions, and the dynamic contribution rate of roots mechanical and hydrological effects of R. pseudoacacia to the slope stability were calculated. The results showed that: (1) The mechanical effect of R. pseudoacacia roots on the stability of shallow slope at the depths of 20, 40 and 60 cm increased by 196.56%±28.08%, 106.74%±13.19% and 20.61%±2.43%, respectively. At the same time, the contribution rate of root mechanical function also had some fluctuation. (2) During the growth period of R. pseudoacacia, R. pseudoacacia canopy intercepted 70.2 mm rainfall, transpiration changed the soil water content and suction stress of the slope, so the stability of shallow slope was effectively improved. (3) The contribution of the roots mechanical action existed throughout the year, and the volatility was less than that of hydrological contribution rate. However, the contribution of hydrological action mainly occurred during the growth period of R. pseudoacacia, and most parts of the peak values of hydrological contribution rate were larger than those of mechanical action. The results further revealed the dynamic changes of R. pseudoacacia slope stability in the hilly and gully region of the Loess Plateau under the natural conditions.

Abstract:Evaporation is one of the most important ways for soil water loss of shallow layer from karst areas in Southwest China. The storage of soil water in shallow layer is very important for agricultural production and ecological restoration in these regions. Based on a series of indoor evaporation experiments, four moss crust biomass levels (0, 0.32, 0.64 and 0.95 kg/m²) and three pine needle biomass levels (0, 0.32 and 0.64 kg/m²) were used to estimate the influences of moss crusts and pine needles on the evaporation losses and the temporal and spatial distribution of soil surface temperature. The performances of three different evaporation models (Black, Rose and Bulk) to simulate the evaporation process of carbonate laterite in karst forest were compared. The results showed that the cumulative evaporation and evaporation rate of moss and pine needle coverage were significantly reduced (P<0.05), and the cumulative evaporation of soil treated with moss inoculation (0.95 kg/m²) and pine needle coverage (0.64 kg/m²) was reduced by 36.9% compared with that of bare soil. Soil water content was significantly increased by moss crusts and pine needles (P<0.05). Moss crusts and pine needles increased the average temperature of the topsoil, and the effect of pine needles on soil temperature was stronger than that of moss crusts. Black, Rose, and Bulk models could well simulate the evaporation process of carbonate derived laterite, but Black model had better performance than Rose and Bulk models. Our results can provide theoretical support for the analysis of water balance and strengthen the understanding of surface hydrologic process in karst forests.

Abstract:Taking the secondary broad-leaved forest, Cunninghamia lanceolata forest and Phyllostachys heterocycla forest in the flood disaster disturbed area as the research objects, the change characteristics and main influencing factors of 11 soil physical properties, including soil bulk density, porosity, field capacity and so on, in the process of natural restoration were analyzed. The results showed that: (1) During the process of undestroyed-destroyed-natural recovery, soil bulk density of secondary broad-leaved forest and C. lanceolata forest increased first and then decreased, while that of P. heterocycla forest decreased gradually. The total porosity, moisture content, saturated water-holding capacity, capillary water-holding capacity and field water-holding capacity of secondary broad-leaved forest and C. lanceolata forest decreased first and then increased, while those of the P. heterocycla forest gradually decreased. The soil texture of three forest types became coarse and then fine. (2) According to the results of correlation analysis and principal component analysis, moisture content, capillary water-holding capacity and field water-holding capacity could be used as the main indicators to evaluate the recovery capability of soil physical properties in the damaged area. (3) According to the results of principal component analysis and factor analysis, soil erosion resistance of three forest types decreased first and then increased in the process of undestroyed-destroyed-natural recovery, and the soil erosion resistance at the stage of natural recovery followed the order of C. lanceolata forest > secondary broad-leaved forest > P. heterocycla forest. This study provided a theoretical basis for the study of the change rules of soil physical properties and soil recovery mechanisms in the disaster disturbed area.

Abstract:Taking five kinds of plantations (Pinus massoniana forest, Cunninghamia lanceolata forest, Eucalyptus urophylla×E. grandis forest, Mytilaria laosensis forest and Castanopsis hystrix forest) in Nanning State-owned Gaofeng Forest Farm of Guangxi as research objects, using field investigation and indoor soaking method, the hydrological effects of the litter layers were quantitatively compared and studied. The results showed as the following: (1) The litter accumulations of five kinds of plantations was about 1.96~9.05 t/hm², and the order of litter accumulation was Castanopsis hystrix forest > Cunninghamia lanceolata forest > Pinus massoniana forest > Eucalyptus urophylla×E. grandis forest > Mytilaria laosensis forest. (2) Among the five stand litters, the Cunninghamia lanceolata forest had the largest maximum water-holding capacity (14.23 t/hm²), and the Pinus massoniana forest had the smallest maximum water-holding capacity (6.26 t/hm²). The maximum water-holding rate of litter in Mytilaria laosensis forest was the largest(577.98%), with that in Castanopsis hystrix forest was the smallest(135.46%). (3) The effective water storage capacity of litters in Cunninghamia lanceolata forest was the largest (10.18 t/hm²), while that in Pinus massoniana forest was the smallest (4.07 t/hm²). The most effective interception rate of litter was 436.35% in the Mytilaria laosensis forest and the smallest was 92.38% in the Castanopsis hystrix forest. (4) The regression analysis showed that the relationship between the water-holding capacity of litters and the soaking time conformed to the logarithmic function (Q=aln t+b(R²>0.773)), and the relationship between litter water absorption rate and soaking time conformed to the power function (V=ktⁿ(R²>0.997)). In the water-holding process, the litters in all stands showed that the water-holding capacity increased rapidly with in 1 hour, and the increasing speed slowed down after 1 hour. After 10~12 hours, the litter basically stopped absorbing water. In conclusion, the litters layer of Cunninghamia lanceolata forest and Mytilaria laosensis forest had strong water conservation function.

Abstract:The soil sample survey and indoor soaking method were used to study the hydrological effects of six different stand types in Huluyu Forest Farm, Hongya mountain nature reserve, Yixian County, Hebei Province. The results showed that the accumulations of litter in 6 stand types ranged from 5.25 to 15.70 t/hm², and the accumulations were the largest in broad-leaved robinia pseudoacacia, followed by mixed needle-width forest, and the smallest in coniferous forest. The total volume of semi-decomposed layer of each forest was larger than that of non-decomposed layer (the non-decomposed layer of pure Pinus tabulaeformis, Diospyros Iotus and Pinus tabulaeformis mixed forest was larger than that of semi-decomposed layer). The maximum water capacity range was 10.55~25.04 t/hm², among which Quercus variabilis (25.04 t/hm²) was the largest, Robinia pseudoacacia (23.66 t/hm²) was the second largest, and Pinus tabuliformis (10.55 t/hm²) was the smallest. The range of maximum water holding rate was 171.19%~260.20%, among which Pinus tabulaeformis of coniferous forest was the largest and Platycladus orientalis was the smallest. The range of effective storage was 6.25~17.60 t/hm², among which Quercus variabilis (17.60 t/hm²) was the largest in broad-leaved forest, Robinia pseudoacacia (17.30 t/hm²) was the second largest, Platycladus orientalis (6.25 t/hm²) was the smallest. The effective retention rates were slightly different. The coniferous Pinus tabuliformis forest was the largest with the value of 180.29%, followed by the broad-leaved Quercus variabilis forest (162.98%), the needle and broad mixed forest Diospyros Iotus and Pinus tabulaeformis was the smallest with the value of 77.22%.The comprehensive analysis showed that the water holding capacity of the litter layer of Quercus variabilis and robinia pseudoacacia was better than those of the litter layer of other four stand types.

Abstract:To uncover the eco-hydrological influence of flower and leaf litters of Rhododendron delavayi at the Baili Dujuan Natural Reserve, the litter bag method in the field and indoor soaking method were applied to study the water holding characteristic of flower-leaf mixture during their decomposition. The results were as follows: (1) The cumulative decomposition rates of R. delavayi increased with decomposition time and growing flower ratio, and the cumulative decomposition rates of each flower-leaf mixture rate varied between the pure flower and pure leaf litters; (2) The relation between water holding ratio and soaking time was a logarithmic function (R=a ln t+b, R²>0.80), the water holding ratio increased instantly within two hours, then turned to slowly within 2~8 hours and leveled off after 8 hours; while the absorption speed rates of litters decreases with soaking time in a power function as (V=ktⁿ, R²>0.99), with the highest absorption speed rate within 4 hours and levelled off thereafter; (3) The maximum water holding rate of different flower-leaf mixture litters increased with decomposition time and flower ratios, but the difference among different flower ratios was lowered with decomposition time; (4) The maximum water holding capacity of different flower-leaf mixture was regulated by the decomposition rate and water holding rate. The maximum water holding capacity of different flower-leaf mixture of R. delavayi increased with flower ratio during 0~360 days, while the flower ratio didn’t work after 450 days of decomposition. In a whole, the R. delavayi utilization should not exceed the half of the current flower litter to maintain the litter decomposition rate and improve the water holding rate.

Abstract:In order to study the effect of different fruit-crop compound managements on soil physiochemical properties and soil-water conservation in apple orchard in the gully region of plateau, and to screen dominant factors for soil-water conservation, four fruit-crop compound managements including artificial weeding (M0), Malus-Trifolium (M1), Malus-Wild (M2) and Malus-Zea (M3) were set up as treatments in Mafang plateau, Shaanxi Province. The differences on soil physiochemical characteristics under the treatments of four fruit-crop compound managements were compared and the soil-water conservation function was evaluated. Stepwise regression analysis and path analysis were used to explore the dominant factors affecting soil-water conservation function. The results showed that the soil physiochemical properties, such as soil density, porosity, water-holding capacity, and nutrient content in M1, M2 and M3 were higher than those of the artificial weeding plots. Among them, the soil bulk density scores of M1, M2 and M3 were reduced by 15.13%, 11.84% and 11.18%, respectively, compared with the artificial weeding plot. The organic matter contents increased by 143.76%, 7.14% and 120.46%, respectively. Soil-water conservation function for four fruit-crop managements was ranked as M1 (0.64) > M3 (0.59) > M2 (0.51) > M0 (0.38). Stepwise regression analysis showed that total porosity, bulk density and organic matter content were the main factors affecting soil-water conservation function. Three soil factors could explain 95% of the variation of soil-water conservation function. Path analysis showed that total porosity was the main deciding factor, and bulk density was the main limiting factor of soil water conservation function. The results of this article could provide a scientific basis for the selection of sustainable soil management in apple orchards in the gully region of plateau.

Abstract:Based on field observation and indoor immersion methods, we examined hydrological effects of litter layer and soil layer of six different densities of Cunninghamia lanceolata plantation in Rongshui Beijianghe Forest Farm of Northern Guangxi. The results showed that: (1) The litter thickness and the stock volume of six densities of Cunninghamia lanceolata plantation ranged from 3.9 to 5.7 cm and from 4.3 to 6.4 t/hm², the thickness of litter was consistent with the change of accumulation, and the order from large to small was 1 755, 1 440, 2 025, 2 700, 2 325, 975 plants/hm²; (2)The maximum water holding capacity of litter is 2.40~14.23 t/hm², and the maximum storage capacity was 5.23~11.51 t/hm². The effective storage capacity was 2.45~9.49 t/hm², of which 1 755 plants/hm² was the largest; (3) In the 0—100 cm soil layer, the soil bulk density of different densities of Cunninghamia lanceolata was between 1.19~1.28 g/cm³, and the minimum density is 1 755 plants/hm²; (4) The maximum and effective water holding capacity of six different densities of Cunninghamia lanceolat were 1 755 plants/hm², and the maximum water holding capacity was far greater than the effective water holding capacity; (5) The water holding capacity of litter and its decomposition layers had a logarithmic relationship with soaking time (R²>0.96), and the water absorption rate had a power function relationship with soaking time (R²>0.92). In conclusion, the forest with density about 1 755 plants/hm², Cunninghamia lanceolata forest showed better water conservation ability.

Abstract:Soil evaporation is an important component of soil water balance and energy exchange, and it is also a key link in the hydrological cycle in arid and semi-arid region. In this study, the evaporation rates of the biocrusts and non-crusted soil developed on aeolian sandy soil and loessal soil were measured under simulated and natural conditions by using micro-lysimeters in the wind-water erosion crisscross region on the Loess Plateau of China, the differences of biocrusts soil and non-crusted soil evaporation characteristics were analyzed, and the soil bulk density, soil particle distribution, and organic matter were determined. The results showed that: (1) The process of evaporation could be clearly divided into three stages under simulated evaporation experiment. As compared with non-crusted soil, biocrusts soil decreased the evaporation rate by 3.04%~15.46% (0.21~1.05 mm/day) at atmospheric evaporation control stage; while it was increased by 32.26%~187.07% (0.58~2.54 mm/day) at soil hydraulic conductivity control stage, and by 12.91% to 87.73% (0.05~0.34 mm/day) at vapor diffusion control stage, in addition, the cumulative soil evaporation was expressed as biocrusts soil higher than non-crusted soil under simulated evaporation experiment. (2) Moreover, the evaporation rate of biocrusts and non-crusted soil was low under natural evaporation conditions from June 16 to September 3, and the daily average evaporation of biocrusts soil was 1.12~1.42 times that of non-crusted soil. The evaporation rates of biocrusts soil and non-crusted soil increased rapidly after rainfall. Furthermore, the soil evaporation amount after rainfall was 2.20~8.55 times that before rainfall, biocrusts increased soil water content after rain and promoted soil evaporation. In addition, biocrusts significantly increased soil cumulative evaporation (F=21.85, P<0.01) from August 10 to August 22. Our experiments indicated that biocrusts significantly enhance the evaporation of aeolian and loessal soil, which may play adverse effects on soil moisture retention in the wind-water erosion crisscross region on the Loess Plateau of China. It is, therefore, essential to pay high attention to the effects of biocrust covering on soil evaporation and take necessary methods on the Loess Plateau of China.

Abstract:This study selected Picea crassifolia forest which in the Pailugou catchment of the middle of the northern slope of the Qilian Mountains as objects. Based on the observation data of rainfall interception, meteorological data and forestland investigation data in the growing season (May to September) of 2019, the rainfall interception process was analyzed, and the rainfall interception process of P. crassifolia forest was simulated by using modified Gash model. The results showed that the total amount of atmospheric rainfall outside the forest during the study period was 418.7 mm, and the rainfall was mainly moderate and light rain. The throughfall, trunk stem flow and canopy interception was 284.5, 6.7 and 127.5 mm, respectively, accounting for 67.94%, 1.60% and 30.46% of the total atmospheric rainfall, respectively. According to the simulation results of modified Gash model, the corresponding simulated value of throughfall, trunk stem flow and canopy interception was 302.2, 3.7 and 112.8 mm, respectively, accounting for 72.18%, 0.88% and 26.94% of the total atmospheric rainfall, respectively. Compared with the measured values, the relative errors of the above parameters were 6.22%, 44.78% and 11.53%. According to the parameters sensitivity analysis of the modified Gash model, the influence of the parameters on the canopy interception rate during the change process of -50% to 50% followed the order of E > c > R > S > S_t > P_t. In conclusion, the modified Gash model showed a good fitting effect in the simulation of rainfall interception of P. crassifolia forest in Qilian Mountains. The research results provide references for the research of the water cycle of P. crassifolia forest in Qilian Mountains.

Abstract:The Hetao Irrigation Area is the largest irrigation area of the Yellow River region. Water scarcity is severe, and farmland shelterbelt is playing an important role in the soil water and salt regulation. In order to determine the effect of shelterbelt on soil moisture in farmland, this paper used traditional statistical methods to investigate the variation of soil moisture in four different configurations of farmland shelterbelt systems in early May 2019. The effects of soil evaporation, wind speed, light intensity, air relative humidity, fine root biomass and soil physical and chemical properties on soil moisture content were analyzed. The results showed that the soil water had obvious spatial structure characteristics. Soil moisture in different configurations of farmland shelterbelt system had obvious spatial heterogeneity. In the horizontal direction, soil moisture in farmland at different distances from the main forest belt increased first and then decreased, and the main influencing factors were wind speed, soil evaporation and the distribution of fine-root biomass density with in 1H (H is the height of shelter forest). In the vertical direction, soil moisture increased with the increase of soil depth, and the main influencing factors were fine-root biomass density in 20-80 cm soil layer, soil bulk density and soil evaporation. soil moisture in different configurations of farmland shelterbelt system had an obvious difference, shelterbelt with a permeability of 40% (1 lines of Populus popular’s + 2 lines of Populus gansuensis + 1 lines of Populus popular’s ) had the best protection effect and the highest soil moisture content. This study basically analyzed the soil moisture of different farmland shelterbelts and provided a theoretical basis for rational shelterbelts and farmland construction.

Abstract:In order to study the influence of stand density on soil infiltration performance, five kinds of Robinia pseudoacacia Linn. stands (1 075, 1 300, 1 575, 1 800, 2 150 trees/hm²) in Loess region of Western Shanxi Province were selected as the research object. The soil infiltration process was determined by double-loop infiltration method, and the correlation of infiltration characteristic index and soil physicochemical properties were also analyzed. The results showed that: (1) The process of soil infiltration in Robinia pseudoacacia Linn. with different densities was the same, all of them went through the stages of transient infiltration, gradual infiltration, and stable infiltration. (2) There were significant differences in initial infiltration rates, stable infiltration rates, average infiltration rates and cumulative infiltration amount under different stand densities (P<0.05). With the increase of stand densities (1 075~1 800 trees/hm²), soil infiltration capability increased. After the stand density of Robinia pseudoacacia Linn. was more than 1 800 trees/hm², there was a trend of weakening in soil infiltration. Therefore, it was suggested that the management density of Robinia pseudoacacia Linn. in Loess region of Western Shanxi Province should be 1 800 trees/hm². (3) The soil infiltration process of Robinia pseudoacacia Linn. with different densities was simulated by Kostiakov model, Horton model, Philip model and Universal Empirical model. In terms of R², the Universal Empirical model had the largest R²(0.990), and could be used as a predictive model for the soil infiltration process of Robinia pseudoacacia Linn. in Loess region of Western Shanxi Province. (4) Soil infiltration capability was negatively correlated with soil bulk density (P<0.01), positively correlated with organic matter and > 0.25 mm water-stable aggregate (P<0.01), and positively correlated with pore condition and water content.

Abstract:In order to study the variation of soil organic carbon in small watershed scale, the spatial variability of soil organic carbon contents in 0-10, 10-20, 20-40 cm was studied by geostatistical method. The results showed that the organic carbon contents in different soil layers in the watershed had a moderate intensity variation with strong spatial autocorrelation. The spatial variation of soil organic carbon content was obvious in the directions of 0 and 135°, and the spatial distribution was anisotropic. The results of Kriging interpolation showed that the contents of soil organic carbon in the shady slope were significantly higher than those in the sunny slope, and the contents of soil organic carbon in the high altitude area were higher than those in the low altitude area. Among the different soil layers, the contents of soil organic carbon were represented by Picea crassifolia > shrub > grassland, indicating that the different vegetation types had an important influence on the content and distribution of soil organic carbon. The spatial variability of soil organic carbon content was related to structural factors such as soil properties and topography factors, which provided a scientific basis for the measurement and description of soil information differences in the small watershed of Qilian Mountain.

Abstract:Using TM/ETM images of Inner Mongolia Autonomous Region in 1990, 1995, 2000, 2005, 2010, 2015 and 2018 as data sources, land use data of Inner Mongolia Autonomous Region based on GIS was extracted. Using the calculation method of China Terrestrial Ecological Service Value Table, the land use data of Inner Mongolia Autonomous Region was analyzed and the ecological service value was calculated. The results showed that: From 1990 to 2018, the land use and land types in the Inner Mongolia Autonomous Region as a whole showed a changing trend in space and time. The specific changes were as follows: The cultivated land, forest land, and unused land are on the decline, the grassland and urban construction land are on the rise. The unused land had the largest reduction in area, and the grassland had the largest increase in area. Combined with the land-use transfer matrix, the reduced unused land, forest land, and cultivated land were mainly converted into grassland. In the past 30 years, the value of ecological service in Inner Mongolia had shown an overall growth trend, with the highest value of grassland ecological service and the lowest value of unused land ecological service. Sensitivity index of ecological service value was < 1, and it indicated that the value of ecological services in Inner Mongolia has been relatively stable in the past 30 years and the results were credible.

Abstract:In order to reveal the soil stoichiometric characteristics and their driving factors under the two grassland utilization modes of enclosure and grazing, the enclosed and grazing grassland of the Ningxia Yunwushan in Guyuan were used as the research object, the soil stoichiometric characteristics of 0-30 cm layer and the influencing factors were quantitatively analyzed. The results showed that: (1) Enclosure decreased the soil penetration resistance, bulk density and moisture content, while increased the soil porosity. (2) In the 0-10 cm soil layer of the enclosed grassland, the main water stable aggregates were > 0.25 mm, and of which >5 mm water-stable aggregates accounted for 46%, the mean weight diameter (MWD) and geometric mean diameter (GWD) was 3.78 and 1.70, respectively, which were significantly higher than those of grazing grassland (P<0.05), but there was not significant in fractal dimension between enclosed and grazing grassland. The soil stability of enclosed grassland was improved. (3) The content of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) of the 0-10 cm soil layer in enclosed grassland was 17.714, 2.018 and 0.659 g/kg, respectively, which were all higher than those of grazing grassland, and the difference in TN was significant (P<0.05). (4) The soil carbon and nitrogen ratio (C/N), carbon and phosphorus ratio (C/P), and nitrogen and phosphorus ratio (N/P) of the 0-20 cm soil layer were all higher in enclosed grassland than those in grazing grassland. (5) SOC, TN, C/P and N/P were all significantly negative related to the soil bulk density and fractal dimension (P<0.05), and SOC and TN were significantly positive related to MWD and GWD in enclosed grassland (P<0.05). The correlation between soil stoichiometry and physical characteristics of grazing grassland was lower than that of enclosed grassland. Enclosure ameliorated soil physical properties and aggregate structure, improved soil nutrients. Soil stoichiometry was closely related to soil physical properties, and the soil physical structure might be the main control factor affecting soil stoichiometric characteristics.

Abstract:Soil adsorption of dissolved organic carbon (DOC) has an important effect on the cycling and transformation of soil organic carbon. In order to make clear the soil adsorption law of DOC in the natural saline-alkali paddy fields, 5 paddy fields (P1, P2, P3, P4 and P5) with different saline-alkali degrees in Western Jilin Province were sampled and incubated in the lab for 70 days in a stationary condition. The experiment studied the DOC adsorption characteristics under different solution concentrations and analyzed the effects of physical and chemical properties on DOC maximum cumulative adsorptions. The results showed that the soil adsorption rate was large in earlier period while decreased with time, which could be described by the Elovich equation suitable to DOC adsorption under different solution concentrations. The Freundlich equation, was best fitted with DOC isometric adsorption features, from which the coefficients indicated that adsorption capacity of soils significantly differed from each other and the adsorption capacity of surface soil was greater than the bottom layer. Exchangeable sodium percentage and pH significantly affected DOC maximum cumulative adsorption which increased with the increased content of clay and organic matter. This study was crucial to elucidate the cycling and transformation of DOC on saline-alkali paddy fields.

Abstract:The typical plant species Cinnamomum camphora in the Needle-broad leaf mixed forest in Changsha was used as research object. Based on the stable isotopic composition of precipitation, bulk soil water, and twig xylem water from March 2017 to September 2019, the seasonal variations of water uptake layers of C. camphora was analyzed by the graphical inference, water-line inference, Iso-Source model and MixSIR model. In addition, the advantages and disadvantages of four methods in determining plant water use are compared, in order to provide new perspectives for the following analysis of plant water use. The results show that: four methods of determining the water uptake layers of C. camphora are basically identical. Pronounced seasonal variation of water use of C. camphora is observed during the observation period. During the wet period consisting of March to June 2017, October 2017 to June 2018 and October 2018 to June 2019, C. camphora mainly uses the soil water at 0—20, 0—40 and 0—20 cm depth, respectively. During the dry periods (July to September) in 2017, 2018 and 2019, C. camphora mostly uptakes the soil water at 20—60, 0—60 and 60—100 cm depth, respectively. If there is no obvious difference of the stable isotopic composition of soil water at each depth, the water-line inference could determine the water uptake layers of C. camphora other than others. The main water uptake layers and utilization ratios of C. camphora calculated by Iso-Source model based on different isotopic composition are both different, however, calculated by the MixSIR model based on different isotopic composition are both largely identical. In conclusion, it is appropriate to combine graphical inference and water-line inference in the qualitative analysis of plant water use, and MixSIR model is more reliable than Iso-Source model in the quantitative research of plant water use.

Abstract:Taking the subtropical moso bamboo (Phyllostachys edulis) forest as research object, the soil biochemical properties and enzymes activities were studied using two forms (NH₄Cl and KNO₃) and three levels (0,40 and 120 kg / (hm²·a).The results showed that: (1) The nitrogen input reduces the pH of soil, different forms and levels had a significant effect on soil pH (P=0.001 and P=0.010); (2) Under high nitrogen treatment, nitrate nitrogen of soil NH₄⁺-N、NO₃^--N and DON differ with ammonium nitrogen of 12.33%, 40.06% and 50.10%. Under the same nitrogen form, high-N treatment of soil NH₄⁺-N、NO₃^--N and DON differ with ammonium nitrogen of 24.24%, 47.12% and 78.12%. Nitrogen forms and levels had significant effects on soil biochemical properties; (3) Compared with the CK, soil urease and invertase activities were increased by 14.16% and 8.11% under High-N treatment, and nitrogen forms had no significant effect on soil urease and invertase activities. Nitrogen levels and forms had no effect on catalase activity (P>0.05); (4) Soil enzyme activities (urease, inverse and catalase activities) showed significant seasonal variation in bamboo forest. The highest activities of urease and invertase were found in the summer and the lowest activities of urease and invertase were found in the winter. But the highest activities of catalase activity was found in the winter. However, inputs of extraneous N made little different on temporal variation. Through the Pearson method, Soil enzyme activities were significantly correlated with soil biochemical properties (P<0.05). The above results show that the effects of nitrogen levels and forms on soil biochemical properties and enzyme activities are different, which can provide a theoretical basis for the management of subtropical moso bamboo (Phyllostachys edulis) forest under the background of nitrogen deposition.

Abstract:In 2017-2018, a field experiment of rape-early rice-late rice in red paddy field was conducted in triple-cropping areas (Jinxian of Jiangxi) in the middle reaches of the Yangtze River, to study the effects of higher planting density and lower nitrogen rate with straw returning on crop yield and soil nitrogen storage of red soil with different fertility, providing a reference for the development of resource conservation and environment-friendly production technology in the triple cropping system area. The results showed that under the condition of returning three crop straws to the field, increasing of soil fertility and planting density could significantly promote the increasing of growth and yield of both rice and rapeseed. The treatment of 30% higher planting density with 20% lower nitrogen application rate could meet the nitrogen demand of the three crops growth, ensure the normal growth of the crops, and significantly improve the nitrogen utilization rate. In general, the crops yield of the treatment of high planting density combined with low nitrogen rate could reach or even slightly higher than that of the conventional cultivation, especially under the condition of high fertility. In the short-term, high planting density combined with low nitrogen rate cultivation did not significantly reduce the total content and storage capacity of both total nitrogen and alkali nitrogen in plough layer soil, but significantly reduced the alkali nitrogen content and the storage capacity of the plough layer soil under the condition of low fertility.

Abstract:Fertilization affects the effect of straw returning to the field. To study the effects of different forms of nitrogen fertilizer on the decomposition of straw and the soil organic carbon fractions can provide scientific basis for the rational application of nitrogen fertilizer under straw returning. Based on the 10-year experiment of wheat-maize rotation and location fertilization, the effects of different amounts of controlled-release urea mixed and common urea(CRF)and common urea (CF) (120, 240 and 360 kg N/hm²) on the decomposition of maize straw and soil organic carbon fractions in fluvo-aquic soil were studied. The results showed that compared with the CF treatment, the CRF treatment had a tendency of promoting the decomposition of straw. At the late stage of straw decomposition, CRF treatment significantly promoted the release of nitrogen and phosphorus from straw compared with CF treatment, while different nitrogen fertilizer treatments had no significant effect on the release of potassium from straw. At the later stage of straw decomposition, under the same nitrogen application rates, CRF treatment with conventional nitrogen application and increased nitrogen application significantly increased the content of water-soluble and heat-soluble organic carbon in soil. In terms of increasing soil microbial biomass carbon and nitrogen contents, the promotion of CRF treatment was significantly higher than that of CF treatment at some stages of straw decomposition. In general, compared with CF treatment, CRF treatment has a better effect on promoting straw decomposition and increasing soil organic carbon fractions.

Abstract:In order to solve the problem of specific application of nitrogen fertilizer varying with the regional soil texture types, the light loam and clay loam were respectively set with no application of nitrogen fertilizer, and the ratios of base-topdressing nitrogen (N) fertilizer at 3:7, 4:6, 5:5, 6:4 and 7:3. The yield, water and nitrogen utilization efficiency in wheat, dynamic changes of soil moisture, water storage, NH₄⁺-N and NO₃^--N contents were studied. The results showed that the highest wheat yield, water use efficiency (WUE) and N production efficiency (NPE) of light loam soil with N base-topdressing ratio at 4:6 were 8 265.3 kg/hm², 27.6 kg/(hm²·mm) and 34.4 kg/kg, respectively. The highest wheat yield, WUE and NPE with N base topdressing ratio of 5:5 in clayey soil were 8 363.2 kg/hm², 28.3 kg/(hm²·mm) and 34.8 kg/kg, respectively. The vertical distribution of soil water content in different growth stages of wheat varied greatly. The water content of light loam soil was 9.3%~26.2%, while 9.7%~27.6% in clay soil. During the whole growth period of wheat, the soil water storage capacity increased at first and then decreased. The water storage capacity of clayey soil was higher than that of light loam. The higher the amount of N topdressing, the higher contents of NH₄⁺-N and NO₃^--N in the surface soil, and the contents of NH₄⁺-N and NO₃^--N decreased with the soil depth. Under precipitation, the contents of NH₄⁺-N and NO₃^--N in light loam soil were easier to leach to the soil depth, and the contents of NH₄⁺-N and NO₃^--N in clay loam soil were higher than those in the light loam at maturity. The results showed that the ability of water and N conservation in clayey soil was stronger than the light loam soil, and the ratio of base-topdressing N could be increased appropriately.

Abstract:In order to provide scientific basis for phosphorus fertilizer application in apple orchard in Jiaodong region, total phosphorus, available phosphorus, inorganic phosphorus and inorganic phosphorus fractions in 0-100 cm layer soil of apple orchards with different planting years were analyzed. The average contents of total phosphorus, inorganic phosphorus, and available phosphorus in the 0-40 cm soil layer were 0.76 g/kg, 681.10 mg/kg, 73.05 mg/kg respectively. The planting years had a significant effect on the soil phosphorus contents. The total soil phosphorus, available phosphorus and inorganic phosphorus fractions decreased with the deepening of soil layer. The inorganic phosphorus mainly existed in the form of Al-P and O-P, followed by Fe-P and Ca-P. The planting years significantly affected the composition of inorganic phosphorus fractions, and the proportion of Al-P was the highest in 11~15 years apple orchards, while the proportion of O-P was the highest in 16~20 years apple orchards. The results of correlation analysis and path analysis showed that Al-P was a relatively effective source of phosphorus in this region.

Abstract:This study was aimed to investigate the distribution of soil nutrients along slope on the Loess Plateau and establish the spatial variation of soil nutrients driven by erosion after forestland reclamation. In this study, soils were collected in the Ziwuling forestland and forestland reclaimed for 28 years which was eroded, in the hilly area of the Loess Plateau. The spatial distributions of soil nutrients were analyzed with the methods of classical statistics and geostatistics. We found that the soil pH value increased by 0.24 units in the slopes after reclamation, while the soil organic matter (OM), total nitrogen (TN), total phosphorus (TP), ammonium nitrogen (NH₄⁺), nitrate nitrogen (NO₃^-), available potassium (AP), available phosphorus (AK) decreased by 13.77, 1.14, 0.10 g/kg, and 6.05, 1.63, 4.99, 58.44 mg/kg, respectively. The variation coefficients of soil OM, TN and TP in the forest were greater than those in the forestland reclamation, while the opposite trend was found in the soil pH value. The changes of the nutrients in the middle slope and lower slope was larger, but was smaller in the upper slope after the forestland reclamation. The soil nutrients in the forest and the forestland reclamation had medium or strong spatial self-correlation. The spatial heterogeneity of OM, TN, TP, NH₄⁺, AP and AK in the forestland reclamation was increased, but the spatial heterogeneity of soil pH was decreased, mainly due to the structural factors, such as terrain, dominated the formation of soil nutrients space heterogeneity. After the reclamation of forestland, the effective range of pH, OM, TN and TP were increased, while NH₄⁺, NO₃^- and AK were decreased, and the variation of AP on the two slopes was inconsistent. Our results demonstrated that soil nutrients contents on the slope decreased in the forestland reclamation, but the changes in the nutrients were related to slope position and slope pattern. Moreover, the spatial dependence of OM, TN and TP increased, but decreased in the available nutrients after the forestland reclamation.

Abstract:Based on the analysis of soil total organic carbon, total nitrogen, total phosphorus, ammonium nitrogen, available phosphorus, and available potassium in the typical sub-alpine peat wetland of Dajiuhu in Shennongjia National Park of Hubei Province, the temporal (spring, summer, autumn, and winter) and spatial (surface 15 cm, middle 30 cm, and bottom 45 cm) characteristics were analyzed. The results showed that: (1) The distribution of soil nutrient components, pH, Eh, and bulk density was normal, in which Apo. and Aph. K were medium and strong variability, the mean value was 31.33 and 71.2 mg/kg. TOC, TP, An., pH, Eh, and bulk density were medium and weak variability, and the mean value was 419.2, 1.56 g/kg, 67.57 mg/kg, 5.33, 104.4, 0.155 g/kg; TN is weakly variable, the mean value was 20.13 g/kg. (2) There was no significant difference in soil TOC in season and depth. There was significant difference between TN and TP in the first layer and the other two layers. There was seasonal difference between TP in the first layer and TP in the first and middle layers. Only Aph. was significantly different from the first and the other two layers. (3) TOC, TP, An. and TN, Apo., TP, and An. showed significant positive correlations. TOC and soil bulk density, Apo. and Eh, pH and Eh, showed significant negative correlations. (4) TOC and TN in the study area were higher than other peat wetlands in China, and the content of soil organic carbon decreased with the increase of latitude.

Abstract:In order to clarify the regulation effects of enhanced density combined with reduced nitrogen fertilizer on yield, quality and fertilizer use efficiency of flue-cured tobacco, a field experiment which took flue-cured tobacco cultivar "Yunyan 105" was conducted in rainy areas for two years (2016 and 2018). Three plant densities (low density of 13 890 plants/hm², medium density of 15 150 plants/hm² and high density of 16 665 plants/hm²) and four nitrogen levels (0,84, 94.5 and 105 kg/hm²) were set, and the effects of planting density, reduced nitrogen and their interaction on yield, quality and nutrient use efficiency were studied. The results showed that compared with the conventional planting pattern, moderate density and reduced nitrogen fertilizer significantly promoted fertilizer use efficiency, yield and output, increased the contents of total sugar, reducing sugar and potassium, reduced total nitrogen and nicotine contents, but did not affect water-soluble chlorine significantly, resulting in the more harmonious tobacco chemical components. The chemical components usability index and NPK utilization in flue-cured tobacco were significantly affected by year, density, N application and their interactions, including the interaction of year and N rate, density and N rate, year both density and N rate. Meanwhile, the contribution of N fertilizer on chemical components usability and fertilizer use efficiency of flue-cured tobacco were 42.5%, 38.2%, and that of planting density were 27.3%, 25.4%, and that of the interaction of both planting density and N rate were 18.9%, 23.8%, respectively. Compared with the current cultivated pattern of flue-cured tobacco, the enhanced density combined with reduction of 10%~20% in nitrogen fertilizer significantly affected to yield, quality and NPK use efficiency of tobacco, and the optimal cultivated pattern of planting density and N rate should be 15 150 plants/hm² and 84.0~94.5 kg/hm², respectively.

Abstract:Based on a six-year field experiment, the effects of irrigation lower limits (soil water suction of 25, 35 and 45 kPa, marked as W₁, W₂ and W₃ respectively) and nitrogen fertilization rates (75, 300 and 525 kg N/hm², marked as N₁, N₂ and N₃ respectively) on soil ammonia volatilization flux, cumulative volatilization, tomato yield and ammonia per unit yield cumulative emission were studied in greenhouse by the high-resolution laser spectroscopy. The results showed that the peak of ammonia volatilization flux, cumulative volatilization, ammonia volatilization accumulation, ammonia volatilization loss rate and tomato yield were significantly affected by the irrigation lower limits, nitrogen fertilization rates and their interactions. The peak of ammonia volatilization flux occurred after 6~8 days of nitrogen application. The empirical sigmoidal model could be used to well fit the changes of ammonia volatilization accumulation with time in the basal and topdressing periods. The model parameters of ammonia volatilization were mainly affected by the irrigation lower limit and its interaction with nitrogen in the basal period, and which was mainly affected by nitrogen fertilization and its interaction with irrigation in the topdressing period. Drip fertigation could significantly reduce ammonia volatilization by 94.78%~96.30% compared with the basal fertilization. The nitrogen loss rate of ammonia volatilization ranged from 0 to 2% under the influence of soil pH, soil NH₄⁺-N content and nitrogen fertilization zone proportion. Considering the mitigation of ammonia volatilization and increase of tomato yield, it was concluded that the optimal management in greenhouse was W₁N₂ treatment.

Abstract:The samples of soil profile at four different times (April 2, May 1, May 30 and August 13) of dwarfed apple orchards under drip fertigation in Weibei dry-land were collected to analyze the characteristics of spatial and temporal distributions of moisture and nutrients in soil profile. The results showed as follows: (1) Soil moisture was concentrated around the drip emitter in the early time. Soil moisture presented an obvious accumulation phenomenon with horizontal movement distance of 20 cm and vertical movement distance of 100 cm. At the later stages, the increased drip irrigation and rainfall resulted in the higher soil moisture in the soil layer of 60-100 cm. A significant difference in the distributions of soil moisture was observed in the horizontal direction. (2) Soil nitrate nitrogen showed an obvious movement with water which distributed concentratedly near the edge of the wetting area and the vertical migration distance was greater than the horizontal migration distance. (3) Surface accumulation of available phosphorus and available potassium were observed on the soil profile. Available phosphorus mainly distributed in 0-20 cm in the horizontal direction and 0-30 cm in the vertical direction. Available potassium distributed mainly in 0-40 cm in the horizontal direction and 0-40 cm in the vertical direction. All the results showed that the contents of available phosphorus and available potassium of near drip emitter were higher than those far away from, which showed an obvious spatial distribution difference. In the horizontal direction of 20-40 cm and the depth of 0-40 cm, the contents of available potassium showed a relatively obvious low-value area where appeared far away in horizontal direction later.(4) Therefore, it is recommended that the amount of irrigation should be reduced to control the depth of water infiltration at 0-40 cm and reduce the loss of nitrogen leaching. The distance between the drip emitter and the plant should be adjusted to ensure that the new root system could absorb sufficient nitrogen, phosphorus and potassium nutrients.

Abstract:In order to explore the influence of water temperature and soil temperature on the water and heat transfer of sand mulched soil under the condition of drip irrigation, a numerical model of water and heat transfer of soil with different water and soil temperature was built based on HYDRUS-2D, and the influence of different water and soil temperature on the dynamic change of water and temperature of sand mulched soil was simulated and analyzed. The results showed that the irrigation water temperature has a significant effect on the distribution of soil water and heat. With the increase of temperature, the moisture content in the soil decreased, which shows that the water temperature of 35 ℃<20 ℃<5 ℃. The irrigation water temperature also had a great influence on the distribution of soil profile temperature, and the temperature changed 5~10 ℃ in the range of 0—15 cm in the surface layer. Under the same water temperature, with the increase of soil temperature, the saturated hydraulic conductivity of the soil increased, and the volume moisture content of the wet soil decreased, which showd that the soil temperature of 30 ℃ < 15 ℃ < 5 ℃. The migration distance of horizontal and vertical wetting front of drip irrigation increased with the increase of temperature. The migration distance and time of wetting front accorded with the power function F=at^b, and the determination coefficient R² was between 0.977 4 and 0.999 6. We established the relationship model between the migration distance of horizontal and vertical wetting front and infiltration time and temperature, in order to provide theoretical guidance for the reasonable supplement irrigation of the sand and gravel mulched ecological agriculture in the arid area of Northwest China.

Abstract:Pisha sandstone area is one of the most serious soil erosion areas in China. In order to study the influencing factors of the soil denudation rate and the improving effect of W-OH material on the Pisha sandstone slope, the Pisha sandstone from Zhungeer banner of Inner Mongolia Autonomous Region was used and the effect of the erosion discharge (2, 3 and 4 L / min), slope angle (5°, 7.5° and 10°) and the W-OH spraying concentration (1%, 2% and 3%) on the soil denudation rate and microstructure of Pisha sandstone slope surface were studied by the method of simulated scouring experiment. The results show that: (1) The denudation rate of Pisha sandstone slope decreases gradually along the slope direction (from the top to the bottom), and it increases with the increase of flow and slope angle; (2) When the slope angle and flow are fixed, the denudation rate is improved significantly with the increase of the spraying concentration of W-OH solution. When the concentration is more than 2%, the consolidation effect of slope is more obvious; (3) SEM results show that W-OH solution can effectively wrap the Pisha sandstone particles to protect them from erosion, and the soil anti-scouribility is increased. Additionally, it is closely related to the concentration of solution and the amount of spray, and also to the slope angle and the flow. The research results will provide some theoretical support for the application of W-OH material in Pisha sandstone area.

Abstract:In order to study the effects of combination of super absorbent polymer and microbial fertilizer on soil microbial biomass carbon, nitrogen and enzymes activities, four treatments, including no application of super absorbent polymer and microbial fertilizer (CK), combination of super absorbent polymer and microbial fertilizer (A), single application of microbial fertilizer (B) and single application of super absorbent polymer (C) were set up in the dryland area of the Loess Plateau. The spatial and temporal dynamics of soil microbial biomass carbon, nitrogen and enzymes activities of 0-10, 10-20, 20-40 cm soil layers during oat growth was analysed. The results showed that: (1) During the whole growth period, soil microbial biomass carbon showed a double-peak curve, the peaks appeared at the booting and filling stages. The soil microbial biomass nitrogen showed the trend of first decreasing, next increasing and then decreasing, with the highest content at the seeding stage. All the soil catalase, invertase and urease activities showed a single-peak curve, with the peak activities of soil catalase and invertase at the booting stage, and the peak of soil urease at heading stage. (2) Except CK, all the soil microbial biomass carbon, nitrogen, soil catalase, invertase and urease activities showed 0-20 cm > 0-10 cm > 20-40 cm. The combination treatment (A) had significant effects on 0-10, 10-20 cm soil layer (p<0.05), the single treatments (B, C) had significant effects only on 10-20 cm soil layers (p<0.05). (3) In 10-20 cm soil layer, compared with other three treatments, the combination treatment (A) all had the significant effects (p<0.05). Soil microbial biomass carbon was improved by 4.82%~40.28%, soil microbial biomass nitrogen improved by 8.44%~68.66%, soil catalase activity improved by 13.32%~60.16%, invertase activity improved by 10.45%~39.14% and urease activity improved by 12.40%~55.62%. (4) Combination treatment (A) had significant effects both on grain and biological yield (p<0.05), the increasing range was 8.40%~20.12% and 10.80%~25.09%. So the combination of super absorbent polymer and microbial fertilizer had best effects on improving soil microbial activity and oat yield in the dry farmland of Inner Mongolia Loess Plateau.

Abstract:In order to explore the effects of long-term different land uses on the colloidal complex and acidity of black soil, the soil colloid dispersion complex was extracted by colloid dispersion grouping method based on 10 pairs of long-term soil positioning sampling point (tillage black soil and shelterbelt black soil) in the black soil corn belt of Jilin Province. The results showed that the absolute contents of cultivated black soil and shelterbelt black soil increased in G₀ and G₂ groups, but decreased in G₁ group, and the total amount of complex decreased by 3.88% and 0.28%, respectively. The pH of cultivated black soil and shelterbelt black soil decreased by 12.12% and 3.77% respectively, and the contents of organic carbon in cultivated black soil and shelterbelt black soil decreased by 23.17% and 9.00% respectively. Humic acid, fulvic acid, exchangeable calcium ion and calcium carbonate decreased in the two land uses, and the average decrease in cultivated black soil was 12.18%, 3.53%, 16.29% and 31.53%, respectively. The black soil of shelterbelt decreased by 20.07%, 13.14%, 2.81% and 7.81%, respectively. The G₁ group showed extremely significant positive correlations with pH, HA, Ca²⁺ and CaCO₃, and significantly negative correlations with FA; while G₂ group had extremely significant negative correlations with pH, HA, Ca²⁺ and CaCO₃. Soil pH was significantly positively correlated with HA, Ca²⁺ and CaCO₃, and negatively correlated with FA. After 11 years, the stability of black soil colloid-dispersion complex decreased. Compared with non-tillage black soil, the stability of black soil colloid-dispersion complex decreased more seriously. The total amount of colloid-dispersion complex decreased more, and the acidity decreased more obviously than that of non-tillage black soil. The changes of Ca²⁺ and HA were the main driving factors affecting soil acidification and the stability of soil aggregates in black soil. As a result of soil acidification, the number of soil colloid-dispersion complex decreased and its stability became worse.