Abstract:Exploring the composition, source of soil organic carbon (SOC) and its stabilization mechanism is key to deeply understand the carbon sink function of terrestrial ecosystem. Compared with the fruitful achievenents of "increasing soil carbon sink", the "stabilizing soil carbon sink" are poorly understood, especially the SOC stabilization mechanism drived by soil microbial under vegetation restoration in eroded areas has not been fully revealed becaused of low SOC accumulation efficiency with the SOC loss under soil erosion. Based on a brief summary of the benefits and influencing factors of SOC accumulation in the process of vegetation restoration in eroded areas, the effects of vegetation restoration on the stability of SOC and its active components were reviewed; Based on the brief introduction of the important role of soil microorganisms in regulating SOC stability, the study progress of SOC stability based on soil microbial carbon pump (MCP) theory were summarized. The main research directions in this field in the future were also suggested, including research objects (especially the rocky desertification area in Southwest China and red soil hilly area in South China), research contents (soil microbial mediated SOC stability and regulation mechanism), research methods (combining field typical sample investigation with indoor microbial culture based the MCP concept) and soil layer (deep soil below 20 cm).

Abstract:In recent years, biochar as a soil modifier has responded well in improving soil quality and crop yield. In this paper, the responses and feedbacks of soil physical and chemical properties, crop growth and yield to biochar application were summarized based on the comprehensive and latest review of biochar application effects. The results showed that: (1) The source, acidification, application years and application amount of biochar determine the change range of soil properties and crop yield after application. Generally speaking, as the application amount increases, soil bulk density decreases, soil porosity increases, soil hydraulic properties and infiltration performance are improved, and soil temperature also increases. (2) Due to the changes of soil physical properties, the biochar application eventually reduces the soil surface salt accumulation. The effect of biochar on soil pH depends on the difference of pH between biochar and soil. In addition, with the increase of biochar application rate, organic matter content increased linearly, while available nitrogen, available potassium and available phosphorus increase firstly and then decrease. (3) Suitable application of biochar can make crops grow better and yield higher. However, the excessive application amount is not economic, which increases the cost, and contribute less to the improvement of crop yield. The appropriate application amount of biochar are recommonded to be in the range of 10 to 40 t/hm². (4) In general, although the response and feedback of soil properties and crop growth to biochar application vary with experimental conditions, soil texture and crop type, and climatic conditions, most of the results confirm that soil properties and crop growth have positive responses to biochar application. In future, the scientific understanding and production practice of biochar application should be formulated according to local conditions.

Abstract:In order to explore the effects of different configuration patterns of shrub and grass on soil erosion from cinnamon soil, a simulation rainfall experiments was conducted on cinnamon soil slopes planted with shrub (Lespedeza bicolor Turcz.) and the herbs (Medicago sativa L.). Three kinds of rainfall intensity (30, 60, 90 mm/h), three kinds of vegetation coverage (ratio of shrubs and herbs coverage was 1∶2 (Ⅰ), 2∶1 (Ⅱ), 1∶1 (Ⅲ)) and three kinds of vegetation patterns (shrubs were located on up-slope (US), middle-slope (MS), low-slope (LS)) were designed to analysis the characters of runoff generation and sediment yield and the benefit of runoff and sediment reduction with the interaction between the vegetation coverage and vegetation patterns under rainfall conditions. The results showed that: (1) Runoff generation and sediment yield on slope increased greatly at the beginning of rainfall, and then the trend of increase gradually slowed down, and finally stabilized. When the shrubs were located at the low slope (LS) and the vegetation coverage was Ⅱ, the runoff generation and sediment yield were the least. (2) The relationship of the effect of runoff reduction and sediment reduction between different vegetation coverage was Ⅱ＞Ⅰ＞Ⅲ. The relationship of the effect of runoff reduction and sediment reduction between different vegetation patterns was LS＞MS＞US. (3) A double factor variance analysis showed that vegetation coverage and vegetation patterns exhibited a significant effect on runoff generation and sediment yield (p＜0.05), but the interaction between the vegetation coverage and vegetation patterns became insignificant on runoff generation and sediment yield. (4) When the shrubs at the low slope with 50% shrub cover and 25% herbs cover, this configuration pattern had the best runoff and sediment reduction efficiency. The results of the study could provide support for the deployment of soil and water conservation measures in cinnamon soil area of Beijing.

Abstract:In order to scientifically understand the effect of the construction of check dams on the erosion dynamics and the ability to reduce gully erosion in the wind-water cross erosion area, in this study, the Xiliugou Basin, one of the ten tributaries, was taken as the research area, and the differences of flood process, erosion dynamics and energy in gully after the construction of check dams were simulated and quantitatively calculated by coupling the distributed hydrological model MIKE SHE and the one-dimensional hydrodynamic model MIKE 11. The reduction of gully erosion by check dams was also estimated. The results showed that: (1) The check dams decreased the flood peak and flood volume of the outlet section by 40.90% and 35.85%, respectively. (2) The average flow velocity, runoff shear force and runoff power along the main gully of the watershed were dropped by 21.66%, 22.02% and 34.31%, respectively. (3) During the planned operation period of the project, the check dams reduced the amount of gully erosion by 33.094 9 million tons under the condition of multi-year average precipitation. The construction of check dams has significantly changed the flooding process of Xiliugou Basin, which alleviated the erosion dynamics along the main channel as well as provided effective erosion mitigation effects.

Abstract:The simulated rainfall experiments were conducted under different slopes (15°, 20° and 25°) combined with different Polyacrylamide (PAM) application rates (0, 0.4, 0.8 and 1.6 g/m²) and different rainfall intensities (60, 90 and 120 mm/h) in this research. The process of runoff and erosion for the sheet erosion of purple soil slopes under different PAM application rates, the influence degree of PAM on the erosion and runoff and their main influence factors were analyzed. Also, the interrill soil erodibility under different PAM application rates was also evaluated. The results showed that the processes of runoff rate and erosion rate increased at first and then was stable with fluctuation, and decreased rapidly at first and was stable with fluctuation, respectively. PAM did not affect the runoff and erosion process of sheet erosion. The runoff amount and erosion amount decreased by 7.71%, 35.16% and 21.12% and by 35.80%, 49.39% and 17.85% for the PAM application rate of 0.4, 0.8 and 1.6 g/m², respectively, when compared with the no PAM application condition. The runoff reduction benefits of different PAM application rates followed the sequence of 0.8 g/m² > 1.6 g/m² > 0.4 g/m² for different rainfall intensities, while the sediment reduction benefits were affected by the slope. On the 15° slope, the order of magnitude of sediment reduction benefit of PAM application was 0.8 g/m² > 1.6 g/m² > 0.4 g/m², while the order of magnitude was 0.8 g/m² > 0.4 g/m² > 1.6 g/m² on the 20° and 25° slopes. The application of PAM could effectively reduce the interrill soil erodibility. The order of magnitude of the effect was 0.8 g/m² > 0.4 g/m² > 1.6 g/m², which was reduced by 54.40%, 40.94% and 18.21%, respectively, when compared with the no PAM application condition.

Abstract:Rocky desertification is an urgent ecological problem in karst areas of Southwest China. The control of rocky desertification leads to the transformation of soil carbon and has an impact on land carbon cycle. However, the effects mechanism of soil and water conservation measures on soil organic carbon in rocky desertification areas is not clear. Three soil and water conservation measures—Nested Ladder (NL), Fish Scale Pit (FSP) and Terrace (TR) in typical rocky desertification area were selected, and compared with natural slope (CK) to study the distribution law of soil organic carbon content. The results showed that the organic carbon content of FSP was 1.4 and 6.2 times higher than that of NL and TR respectively. The organic carbon storage in the 0—20 cm soil layer of the FSP was higher than that in NL and TR by 30.78%, 444.44% respectively. The soil active carbon content of FSP was also significantly higher than that of the other two water and soil conservation measures, so its carbon sequestration effect was the best. The storage of organic carbon was significantly positively correlated with the easily oxidized carbon, soluble carbon and microbial biomass carbon (p < 0.01), the easily oxidized carbon was significantly positively correlated with soluble carbon and microbial biomass carbon (p < 0.01), and the soluble carbon was significantly correlated with microbial biomass carbon (p < 0.05). The increase of carbon nitrogen ratio in FSP and NL would promote soil organic carbon sequestration. The study shows that FSP can be used as a priority control measure in the ecological restoration and construction of rocky desertification areas in the future.

Abstract:Shallow landslides caused by extreme rainfall have resulted in serious environmental damage and losses. In order to explore the effects of land use, vegetation types and topographic factors on shallow landslides under extreme rainfall conditions, this study conducted a field investigation on shallow landslides caused by extreme rainfall from October 3 to 6, 2021 in Caijiachuan Watershed of Ji County, Shanxi Province, and analyzed the characteristics and process of extreme rainfall, the number and damaged area of shallow landslide under different land uses, vegetation and terrain conditions. The results showed that: (1) The extreme rainfall was 31.2% of the annual average rainfall, reaching 161.3 mm, the duration of rainfall was 84 hours, the peak rainfall intensity was 7 mm/h, the average rainfall intensity was 2.1 mm/h, and the frequency of rainfall of this degree was 0.16%. (2) A total of 479 shallow landslides occurred in the small watershed of farmland, plantation and secondary forest in Caijiachuan basin, with the damage area of 183 881 m², and 90% of the shallow landslide area was less than 885 m². (3) The number and damage area of shallow landslides per unit area were as follows: small watershed of agricultural land (214 /km² and 109 241 m²/km²) > small watershed of plantation forest (163 /km² and 48 779 m²/km²) > small watershed of secondary forest (42 /km² and 17 176 m²/km²). At the small watershed scale, the effect of forest vegetation on shallow landslide prevention was significantly higher than that of agricultural land, and the effect of secondary forest was better than that of artificial forest. (4) The slope of shallow landslide was 10°~80°, the number of shallow landslide and the damaged area increased with the increases of slopes, and reached the peak in the range of 40°~50°. When the slope was greater than 50°, the number of shallow landslide and the damaged area decreased with the increases of slopes. Slope was the dominant factor affecting shallow landslide. (5) Shallow landslides mainly occurred on the slope with slope aspect of 22.5°~337.5°. The number and damage area of shallow landslides did not show obvious regularity with slope aspect, and slope aspect had little influence on shallow landslides.

Abstract:To study the erosion reduction effect of a check dam on the landslide, the variation of motion parameters, dynamic parameters, and energy parameters of loess landslide with the rising elevation of the erosion base level were analyzed by Voellmy model based on three-dimensional continuum model. The results showed that the mean velocity, frontal velocity, erosion volume, and total kinetic energy of the landslide masses all increased sharply during the gully-slope motion. As a result, the frontal velocity fluctuated and severely eroded at the slope’s foot, which was extremely destructive. Landslide running time and mean velocity varied within the sigmoidal function distribution range, frontal velocity and landslide moving distance varied within the linear function distribution range, and erosion mass volume and total kinetic energy varied within the exponential function distribution range with the rising elevation of the erosion base level. The motion space and erosion space of the landslide were gradually reduced, which only reduced the landslide velocity to a certain extent, but it could effectively inhibit the erosion effect of the landslide and sharply reduce the mass of eroded materials, thereby effectively reduced the total kinetic energy of the landslide, and reduced the disaster intensity largely with the rising elevation of the erosion base level. The information indicated that the check dam could reduce erosion by the rising elevation of the erosion base level, and the results could be useful for better understanding the erosion reduction mechanisms of a check dam on loess landslide.

Abstract:The arsenic sandstone area with extremely severe hydraulic erosion was selected as the research object. Based on continuous monitoring experiments of runoff plots in the field, 3D laser scanning, UAV aerial photography and variance-mean ratio method were used to compare and analyze the characteristics of flow and sand production and the evolution of slope microtopography under three typical natural vegetation patterns (aggregated distribution, uniform distribution and random distribution) on arsenic sandstone slopes. The results showed that: (1) The uniform distribution pattern had the most obvious effect on mitigating soil erosion on arsenic sandstone slopes under hydraulic erosion conditions, with a flow reduction rate of 64%, a sand reduction rate of 72%, and the lowest soil loss of 0.05 kg/m² compared was bare slopes. There was a polynomial curve relationship between runoff and sediment volume, and its fitting function was y=-0.0462X²+0.5355X-0.865, R²=0.736. (2) The erosion area of the uniform distribution pattern was the smallest, which was 12.28 m², and the deposition area was the largest, which was 3.44 m², and the soil erosion intensity was weaker than other slopes, mainly light erosion. (3) The correlation between runoff sediment volume and average deposition depth of uniform distribution pattern was strong, with a significantly positively correlated with runoff volume (p<0.05), and the correlation coefficient was 0.603, and had a highly significant positive correlation with sediment volume (p<0.01), and the correlation coefficient was 0.771.

Abstract:Taking the soil composite erosion process of Haifeng karst basin in eastern Yunnan province as the research object, the distribution characteristics of comprehensive soil erodibility index (CSEI) were analyzed, and the correlation, variation trend and influencing factors of soil erodibility between surface and underground soil were discussed, so as to deeply understand the soil erosion mechanism in karst area and control rock desertification. Through field investigation and sampling, soil hydrometer, wet screening of aggregates and other methods, the physical and chemical properties and erodibility change characteristics of soils in different erosion fields on the surface and underground of karst fault basin in eastern Yunnan were analyzed. The results showed that: (1) Soil physical and chemical properties changed with the erosion process. Clay, SOC and large aggregate (>0.25 mm) in the soil showed a decreasing trend, while silt and small aggregate (<0.25 mm) showed an increasing trend. There were significant differences in soil characteristics among different erosion processes. The content of soil clay (20.91%~45.62%), sand (44.96%~64.59%), SOC (4.93~88.72 g/kg) and large aggregate (17.82%~99.86%) in surface erosion process was higher than that in underground leakage process (15.30%~30.86%, 43.63%~64.59%, 3.57~19.05 g/kg and 16.81%~85.94%). The content of silt (4.85%~30.84%) and small aggregates (0.14%~82.18%) was less than that of underground leakage process (16.03%~25.86% and 14.06%~83.19%). (2) CSEI was closely related to soil physical and chemical properties. CSEI was negatively correlated with clay, sand, large aggregates, SOC, MWD and GMD (p<0.01), and positively correlated with silt and small aggregates (p<0.01). The main influencing factors of CSEI were SOC and soil aggregates stability. Clay, sand, SOC and water-stable aggregate contents had greater influence on CSEI of surface erosion process, while other factors had greater influence on CSEI of underground loss process. (3) CSEI had applicability to evaluate soil erodibility in the process of surface and underground erosion in karst basin, the CSEI of underground leakage was higher than that of surface erosion, both of which rose with the change of erosion process and soil depth. And the underground leakage process had secondary erosion effect. The soil erosion process was a compound and continuous process of surface erosion and underground leakage. The synergistic restoration of vegetation-soil could enhance soil erosion resistance.

Abstract:The purpose of this study was to explore the migration path and loss characteristics of runoff and dissolved organic carbon (DOC) in sloping farmland of yellow soil at each maize growth period under different tillage measures. Taking the down slope ridge planting, flat planting and cross ridge planting as the research object, the surface runoff, interflow and DOC loss under natural rainfall were discussed by combining field runoff plot and laboratory analysis. The results showed that: (1) The slope runoff and DOC flux at each growth stage of maize were significantly affected by rainfall levels, and increased with the increase of rainfall levels and the losses were the largest at maturity. (2) The surface runoff, interflow of 0-20 cm and interflow of 20-40 cm accounted for 78.98%, 9.05% and 11.97% of the total runoff respectively, and DOC flux accounted for 74.90%, 11.97% and 13.13% of the total loss flux respectively. (3) The amount of DOC loss on the slope of cross ridge planting was significantly less than that of down slope ridge planting, and the runoff of cross ridge planting was 0.93 times that of flat planting and 0.86 times that of down slope ridge planting. The DOC flux of cross ridge planting was 0.85 times that of flat planting and 0.79 times that of down slope ridge planting. The increase of rainfall levels would significantly aggravate the slope runoff and DOC loss. Surface runoff and DOC flux had the largest loss during maize maturity in the study area and the surface runoff was the main way of slope runoff and DOC loss, the cross ridge planting could effectively reduce slope runoff and DOC loss.

Abstract:Erosive rainfall is the main dynamic factor causing soil and water loss on the karst yellow soil slope. Using the measured data of 92 erosive rainfall runoff and sediment yield from 4 runoff plots from 2018 to 2020 at Huyangshui watershed in Zunyi City of Guizhou Province, this paper studied the response of runoff and sediment yield to bare slope and rocky outcropping plots under single rainfall events. The results showed that: (1) Erosive rainfall could be divided into three types A, B and C. A rainfall was the main type causing soil erosion on karst yellow soil slope. The standard of erosive rainfall was single rainfall＞6.6 mm or I₃₀＞3.6 mm/h. (2) On the bare slope, totally 63.27% of the erosive rainfall runoff depth was less than 0.4 mm, and 66.30% of the erosive rainfall soil loss was less than 1 g/m², and the soil erosion was mainly contributed by some single rainfall events. Contrasting the three types of rainfall, the law of runoff and sediment yield was as type A＞type C＞type B. (3) Soil loss amount was mainly determined by runoff depth, which directly determined the sediment yield on slope. 20 mm was a mutation value in type A rainfall leading to the apparent increase in runoff depth and soil loss on karst yellow soil slope. (4) Under the three types of rainfall, the plot runoff yield increased with the outcrop rate. That is to say, rock outcrop increased the runoff yield of the slope. But the change of sediment yield was complicated. In case of type A rainfall, sediment yield increased obviously with the outcrop rates of rocks. These results have great significance for the management of soil erosion and the establishment of soil erosion prediction model on karst slopes.

Abstract:Runoff and sediment yield is the main form of soil erosion in sloping farmland. In order to explore the soil and water conservation benefit of Rosa sterilis S. D. Shi on slope farmland in karst mountainous area of central Guizhou, using field location observation method in runoff plot and correlation analysis method, this study analyzed the field measured data of runoff and sediment under six natural runoff plots, which were natural restoration land (NRL), R. sterilis S. D. Shi land (RSSDSL), R. sterilis S. D. Shi + natural grassland (RSSDSL+NGL),on 15ånd 25° slope under 15 erosive rainfalls from June to September 2016. The results showed that:(1) Under the same slope, rainfall and maximum 30 min rainfall intensity(I₃₀), the RSSDSL had better water and sediment retention ability than NRL, and RSSDSL+NGL pattern was better than the single RSSDSL pattern.(2) The runoff and sediment reduction effect of R. sterilis S. D. Shi planting pattern with a slope of 25° was better than that of 15°, and the sediment reduction effect was better than runoff reduction. The RSSDSL+NGL had the best runoff and sediment reduction effect. Under the four rain types of light rain, moderate rain, heavy rain and rainstorm, when the slope was 15°, compared with NRL, the average runoff reduction of RSSDSL+NGL were 59.08%, 65.23%, 56.96% and 54.87%, respectively, and the average sediment reduction were 87.32%, 71.64%, 51.10% and 74.69%, respectively. While, when the slope was 25°, the average runoff of reduction were 53.11%, 76.09%, 76.72% and 46.12%, respectively, and the average sediment reduction were 85.40%, 86.87%, 71.55% and 73.99%, respectively. (3) Runoff and sediment yield in the study area was highly correlated with rainfall parameters (P, I₃₀) and was significant at the 0.01 level. R. sterilis S. D. Shi had obvious effect on runoff and sediment reduction under different rain types, and the best effect was achieved in light rain and moderate rain. In conclusion, R. sterilis S. D. Shi planting in the study area could effectively control the rainfall erosion of all rain types, and could be used as an excellent economic choice for ecological restoration in karst mountainous areas of Guizhou Province.

Abstract:In order to study the effects of different planting densities on soil erosion of sloping cropland under the conventional tillage, different planting densities and growth periods of winter wheat were used to simulate the different crop coverages. The artificial rainfall simulation method was used to measure coverage, surface runoff and soil erosion of five different density treatments (0, 1 500 000, 2 500 000, 3 500 000 and 4 500 000 plants/hm²) in different growth periods, and to analyze the effect of crop coverage on soil erosion. The result showed that: (1) The difference of crop planting density on sloping cropland lead to the difference of coverage, which had a significant impact on soil erosion. Crop coverage generally increased with the increasing of planting density, however, if the density was too high, due to poor growth conditions, the coverage became smaller. The coverage was the largest at 75 000 plants/hm², but the coverage of 90 000 plants/hm², which was the highest planting density, was not the largest. (2) There was a good exponential function relationship between erosion and runoff and crop cover, and the function was Y = 44.37e^-0.09x (p < 0.01), Y = 1089.19e^-0.02x (p < 0.01), respectively. That is, with the increasing of crop coverage, runoff and erosion decreased. (3) There was a significant exponential function relationship between soil erosion and surface runoff (R² = 0.96). These conclusions were of great significance for analyzing soil erosion in conventional tillage cropland, quantifying the factors of tillage measures, accurately predicting soil erosion, and guiding cropland water and soil conservation.

Abstract:In the alpine mountains areas of northwest China, the cryosphere environment leads to more complicated soil erosion process. Therefore, taking the Irtysh River Basin in the Altai Mountains of Xinjiang as an example, this study intended to build a model to simulate the soil erosion process under the combined influence of rainfall, snowmelt and land use change (LUCC) and to reveal the amplification of soil erosion under the influence of compound factors. Therefore, the InVEST model was used to simulate the spatial distribution of soil erosion in 2000, 2005, 2010 and 2015 in detail, and three scenarios were established for the analysis of compound impacts, namely rainfall and land use change, rainfall and snowmelt change, and the combined effects of rainfall, snowmelt and landuse change on soil erosion. The results showed that: (1) Compared with 2000, the land use had changed by 1.67%, 2.02% and 4.19% from 2005 to 2015, which made the soil erosion in the whole basin increased by 3.49%, 3.02% and 3.31%, respectively compared with the single rainfall erosion. (2) Although the snowfall only accounted for 30.49%, 23.10%, 38.46% and 35.26% of the annual precipitation from 2000 to 2015, the occurrence of snowmelt increased soil erosion in the basin by 249.00%, 88.00%, 843.00% and 566.00%, respectively, and the annual average erosion amount increased by 20 080 300 tons, and the erosion amount under the rainfall and snowmelt scenarios was 4.2 times that of a single rainfall. (3) In the context of snowmelt, the impact of land use was further considered, soil erosion amount increased by 2.99%, 2.16% and 3.50% from 2000 to 2015, respectively. This study provided new evidence for the impact of snowmelt on soil erosion in cold regions, and provided a basic theoretical understanding for subsequent soil and water conservation in cold regions.

Abstract:As one of the typical ecologically fragile areas in the Yellow River Basin, the Pisha sandstone area is difficult to control soil erosion, meanwhile the distribution of topography and erosion in the slope and gully systems is quite different in this area. Most of the studies on regional soil erosion have focused on the spatial distribution of erosion and the differences in erosion between different land types, but less work has been done on regional erosion from the perspective of slope and gully systems, which can’t provide theoretical support for subsequent refined management. In this study, three typical small basins located in Jungar Banner were selected as the study area, firstly, the slope and gully system were divided according to the shoulder line extracted by visual interpretation, and then the distribution and correlation between topography and hydraulic erosion based on geostatistics were carried out. The Results showed that the distribution characteristics of topographic factors in the selected basins were consistent with the distribution of geomorphological characteristics, the high values were concentrated in the gully system, while the low values were concentrated in the slope system, meanwhile the maximum statistical values of the topographic factors appeared in the gully system of Telagou small basin (covered with sand). There existed differences in the spatial distribution of water erosion between the slope and gully systems in typical basins, in which the slope systems were dominated by slight erosion, accounting for 87% to 97%, and the proportion of slight erosion in gully systems were 54% to 72% lower than that in the slope systems, while the highest average soil erosion modulus occurred in the gully system of Shibuertai small basin (bare rock), up to 97.5 t/(hm²·a). There was a significant positive correlation between slope, roughness, cutting depth and soil erosion modulus (p<0.001). Sunny slopes were the main distribution direction of the units above the intensity erosion, accounting for 56.8% to 75.8%. To sum up, gully systems and their sunny slopes were the parts that need to be strengthened urgently in the subsequent comprehensive management of small basins in this area.

Abstract:Under the background of global climate change,shrub development of alpine meadow has become the main trend of landscape change in Qinghai-Tibet Plateau.In order to better understand the relationship between shrub and alpine meadow ecosystem,this paper taking shrub alpine meadow of Caragana Erinacea Kom and Potentilla Fruticosa in the eastern margin of the Qinghai-Tibet Plateau as an example, characteristics of soil water holding capacity and infiltration capacity during non-shrub, mild shrub, moderate shrub and severe shrub were studied by using ring knife soaking method and double ring infiltration method. The results showed that: (1) Soil bulk density was the lowest and total porosity was the highest in moderate shrub stage. (2) With the increase of degree of shrub, soil water content of two kinds of shrub meadows showed an increasing trend, and it was the highest in heavy shrub stage. Soil capillary water capacity, field water capacity and maximum water capacity showed a parabolic trend, and maximum water capacity was the highest in moderate shrub stage. (3) The initial infiltration rate, stable infiltration rate and infiltration rate of two kinds of shrub meadow showed an increasing trend with increase of degree of shrub, and infiltration rates in moderate and severe shrub stages was significantly higher than that in non-shrub stage. (4) Correlation analysis showed that soil infiltration index was significantly correlated with soil water content and non-capillary porosity. Therefore, changes of soil hydraulic properties usually occur in moderate and severe shrub stages during alpine meadow shrub development.

Abstract:In order to solve the problems of single vegetation type and low ecological function in the riparian zone in the upper reaches of Baiyangdian Lake, starting from the ecological function orientation of intercepting and purifying non-point source pollutants in the riparian vegetation zone, two kinds of herbs and one kind of shrub were selected as the research object to study the purification effect of riparian vegetation zone on nitrogen, phosphorus and sediment pollutants through a simulated runoff scouring test. The results were as follows: (1) Compared with single shrub, the purification efficiency of single herb was better, and the purification efficiency of total phosphorus, total nitrogen and sediment of Cynodon dactylon was the best, which were 10.88%, 6.96% and 34.20% respectively; Lolium perenne had good purification effects on ammonia nitrogen and nitrate nitrogen, which were 10.11% and 9.54% respectively; (2) Among the multiple plant configurations, the purification efficiency of grass shrub combination of Lespedeza bicolor, Cynodon dactylon and Lolium perenne was better, and the average values of various indexes were increased by 13.31%, 10.84%, 9.64%, 12.36% and 46.43% respectively compared with the bare soil; (3) The plant combination of shrub&herbs and mixed herbs had higher purification efficiency for five pollutant indexes, and the removal effect of mixed plant group was better than that of single plant group. In conclusion, riparian vegetation zone had purification effect on surface source pollution, among which the combination of shrub&herbs and mixed herbs had a better purification effect. The combination of grass and shrub plants of Lespedeza bicolor, Cynodon dactylon and Lolium perenne showed the best purification effect.

Abstract:In order to reveal the difference of soil infiltration characteristics between exposed rock-soil interface and non-rock-soil interface in karst rocky desertification area, the ring knife method was used to explore the soil infiltration characteristics of rock-soil interface and non-rock-soil interface, as well as the adaptability of infiltration model. The results showed that: (1) The bulk density of 0—10 cm soil layer and 10—20 cm soil layer soil at rock-soil interface was higher than that at non-rock-soil interface, while the total soil porosity was lower than that at non-rock-soil interface. The water content and capillary porosity of rock-soil interface was generally greater than that of non-rock-soil interface, while non-capillary porosity, clay particles and drainage capacity was generally less than that of non-rock-soil interface. (2) The infiltration capacity of rock-soil interface was generally less than that of non-rock-soil interface, and the initial infiltration rate, average infiltration rate and stable infiltration rate at rock-soil interface was lower than that at non-rock-soil interface (except flat). (3) The initial infiltration rate, average infiltration rate and stable infiltration rate of the 0—10 cm soil layer and 10—20 cm soil layer of the three shapes at rock-soil interface followed the order of flat > convex > concave. The infiltration at non-rock-soil interface was similar to that at rock-soil interface, which was mainly determined by soil bulk density and total porosity. (4) The fitting effects of Horton model on soil infiltration at rock-soil interface and non-rock-soil interface were better than Kostiakov model and Philip model, and it could better simulate soil infiltration characteristics under complex conditions in karst areas. This study was expected to provide new research ideas and scientific theoretical support for the in-depth understanding of water infiltration and soil erosion in karst areas.

Abstract:Soil compaction is one of the problems of farmland soil degradation. Straw returning is an important measure to increase soil organic matter content and improve the soil. However, the effects of straw returning and soil matrix potential on soil compaction are still unclear. The experiment set three treatments with straw addition amount of 0, 3 and 5 g /kg, and three soil matrix potential treatments of 1 000, 100 and 10 kPa. The compression curves of different treatments were measured by the consolidation test and the compression and resilience characteristic indexes were calculated. The results showed that the effects of straw returning, soil matrix potential and their interaction on maximum curvature, pre-compression stress, compression index and resilience index reached significant levels. Pre-compression stress, compression index and resilience index all increased with the increasing of straw addition, while the maximum curvature showed the opposite trend. Soil matrix potential had a positive correlation with the maximum curvature, pre-compression stress and the compression index. With the increasing of soil matrix potential, resilience index decreased first and then increased. Straw addition could improve soil resilience and compression resistance.

Abstract:Based on Land Use and Cover Change (LUCC) and meteorological drought, comprehensively analysis of regional Groundwater Depth (GWD) change and its dynamic response, and clarifying the periodic leading factors of GWD change has practical significance for comprehensive management and effective control of groundwater resources in groundwater overexploitation area. Collecting the monthly-scale GWD data of 78 groundwater monitoring wells in the eastern plain area of Changji Prefecture from 2000 to 2020 and five phases of remote sensing image data, and combing with the multi-scale Standardized Precipitation Evapotranspiration Index (SPEI) during the contract period, the dynamic response of GWD at different spatial and temporal scales to LUCC and SPEI were analyzed, and the comprehensive influence of land use change and drought change trend on the change of GWD in the study area was discussed. The results showed that during the 21 years from 2000 to 2020, the GWD in the study area showed the change characteristics of no significant indigenous change (2000-2005)-significant indigenous increasing (2005-2014)-slowing down (2014-2017)-continuous increasing (2017-2020). The overall trend was increasing continuously, the spatial distribution gradually increased from north to south. During the same period, the area of land use types changed significantly. Cropland was the main land use type, and its area increased continuously. The fractal dimension showed the change characteristics of first decreasing (2000-2005) then increasing (2005-2010), and then decreasing (2010-2020). The interannual dynamic change of SPEI showed a significant trend of indigenous drought. The annual-scale sequence mutated in 2012 and 2017, and the frequency of meteorological drought increased since 2016. From 2000 to 2015, the dynamic change of GWD in the study area responded significantly to land use change, especially cultivated land change. From 2016 to 2020, the dynamic change of GWD was a joint response to land use change and meteorological drought factors.

Abstract:Climate warming and humidification has important practical significance for vegetation growth and coverage, as well as rational land development and utilization and ecological environment protection. Taking Mu Us sandy land as the study area, based on the meteorological data (temperature, precipitation and evaporation) from 1959 to 2019, this paper analyzed the characteristic changes of climate warming and humidification by using climate trend change, M-K mutation and wavelet cycle, and explored the response relationship between it and meteorological factors in the study area based on normalized difference vegetation index (NDVI) value in the growing season. The results showed that: (1) During the study period, the annual average temperature, annual average precipitation and annual average evaporation in Mu Us sandy land increased by 1.7 ℃, 11.19 and 33.82 mm, respectively, and showed a significant upward trend. (2) The 1970s was the starting time of the sudden change of meteorological factors, and the sudden change of temperature from cold to warm, precipitation from less to more, and climate from dry to wet occurred from 1970s to 1990s. (3) The annual average temperature, precipitation and evaporation in the sandy land oscillated most obviously in the period of 20~30 years, and reached the peak at 28 years, which was the first main period of the change of meteorological factors in Mu Us sandy land. (4) From 1998 to 2019, NDVI generally showed a fluctuating and increasing trend, which was positively correlated with evaporation and precipitation. The significance of evaporation was greater than that of precipitation. The research results could provide a scientific basis for the effective protection and management of these valuable ecosystems under the current climate change.

Abstract:Accurately understanding the characteristics of land use / cover change (LUCC) in Tibet Autonomous Region and exploring its driving factors are of great significance to scientifically predict the trend of land use change in Tibet and make economical and intensive use of land resources. Based on the five periods of LUCC data from 2000 to 2020, this paper analyzed the characteristics of LUCC in Tibet Autonomous Region from dynamics and transformation trend. The results showed that: (1) LUCC in the study area was mainly grassland, forest land and unused land. The change frequency was the highest from 2015 to 2020, and the change areas of urban and rural construction land, cultivated land and water area were relatively concentrated in space. (2) Urban and rural construction land continued to grow, grassland continued to shrink, and other land types increased in a fluctuating manner. (3) LUCC in the "One River and Three Streams" Basin of Tibet were rich in species and complex in causes. The rest of the areas were dominated by grassland and unused land changes. (4) Over the past 20 years, there have been many driving factors for LUCC in Tibet. Natural factors played a decisive role in the distribution of cultivated land and water areas, while socio-economic and policy factors had a great impact on LUCC in Tibet in recent years. The transformation of land use types was complex, and there were significant differences in the change characteristics of different types, among which the biggest change was the transformation between grassland and unused land. The driving factors of LUCC in Tibet were complex. Climate change and human activities had a significant driving effect on land use changes in the study area.

Abstract:Through evaluating a few existing multi-source products of gross primary productivity (GPP) and evapotranspiration (ET), we constructed combined datasets of GPP and ET for the Qinling Mountains in China. Then, the spatial-temporal variations of water use efficiency (WUE) were calculated and analyzed for the Qinling Mountains. The results indicated that the estimation effects of different products of GPP and ET were very different for different vegetation types. Generally, the products of VPM GPP, RF GPP performed well for GPP estimation, while the products of China ET and PML-V2 ET performed well for ET estimation in China. In the Qinling Mountains, the average annual ecosystem GPP_year was about 1 489.95 g C/m²; the average ET_year was about 588.49 mm; the average WUE_year was about 2.56 g C/kg H₂O; and the change rate of average WUE_year was about 0.156 g C/(kg H₂O·10 years). The values of average WUE_year showed a non-significant rising trend (p > 0.05). The differences of annual average WUE_year were not great among different vegetation types. However, the trends of WUE_year changes were various for different vegetation types. Some vegetation types showed increasing trends, while others showed decreasing trends. The dynamics of average montly WUE_month had two obvious peaks per year. This study provided a reference for data acquirement and selection for the research of carbon-water relationships in different ecosystems. It also deepened our understanding of the temporal and spatial changes of ecosystem WUE in the Qinling Mountains in China.

Abstract:In order to evaluate the water conservation capacity of main forests in Xiaowutai Mountains and provide a new idea for the selection of water conservation tree species, the distribution characteristics and water conservation capacity of litter of seven typical forests in Xiaowutai Mountains were studied by immersion method and simulated rainfall method. The results showed that: (1) The litter thickness and distribution range of broad-leaved forests were greater than those of coniferous and broad-leaved mixed forests and coniferous forests, which were the greatest in pure forest of Populus cathayana Rehd. and pure forest of Quercus mongolica Fischer ex Ledebour, respectively, and the thickness on lower slope were greater than that on upper slope. (2) Litter accumulation followed the order of pure forest of Pinus tabuliformis Carrière > pure forest of P. cathayana Rehd. > mixed forest of P. tabuliformis Carrière and Q. mongolica Fischer ex Ledebour > pure forest of B. platyphylla Suk. > mixed forest of B. platyphylla Suk. and Picea asperata Masters > pure forest of Q. mongolica Fischer ex Ledebour > pure forest of Tiliatuan Szyszylowicz, and the litter accumulation of the semi-decomposed layer was larger than that of the undecomposed layer. (3) The litter holding capacity of the semi-decomposed layer was larger than that of the undecomposed layer, and the litter holding capacity of coniferous and broad-leaved mixed forests and mostly broad-leaved forests was greater than that of coniferous forests. Among them, the maximum water holding capacity, effective storage capacity and the final holding capacity of litter of pure forest P. cathayana Rehd. of were the greatest, which was 1.69, 1.37 and 0.41 mm, respectively. (4) The water holding capacity of litter in all forests was higher in immersion method than that in rainfall simulation method, so if only using the traditional soaking method, the results would be too large. The water conservation capacity of litter in broad-leaved forest, coniferous and broad-leaved mixed forest was better than that in coniferous forest, among which the water conservation capacity of pure forest of P. cathayana Rehd. and pure forest of B. platyphylla Suk. both were the strongest. More broad-leaved trees such as P. cathayana Rehd. and B. platyphylla Suk. should be selected in the selection of tree species for water conservation forest in the future.

Abstract:The study of transpiration change and its relationship with environmental factors at different time scales is of great theoretical significance for understanding the driving mechanism of plant growth and estimating the water consumption of stands. In this study, eight sample trees were selected from Robinia pseudoacacia forest in Caijiachuan from May 2021 to December 2021 and thermal diffusion probe (TDP) was used to measure stem sap flow of Robinia pseudoacacia. Environmental factors such as solar radiation, air temperature, rainfall, soil temperature and soil water content were monitored synchronously. The characteristics of Robinia pseudoacacia transpiration and its response to environmental factors at different time scales (hour, day and month) were analyzed. The results showed that: (1) The relationships between transpiration and environmental factors were different at different time scales, on the whole, with the increase of time scale, soil water content became the main factor affecting transpiration. And the short time scale depended on surface soil water content, while the longtime scale depended on both surface soil water content and deeper soil water content. Hourly scale, the transpiration varied with the variation of solar radiation, air temperature, water vapor pressure deficit and soil temperature, but the peak value of transpiration and the peak value of environmental factors were different in time, and the time difference was up to -180 to 30 min. Among the environmental factors, solar radiation and air temperature had great influence on transpiration. At the daily scale, the transpiration rate increased with the increase of shallow soil water content, and shallow soil water content had a great influence on daily transpiration. At the monthly scale, the effect of shallow and deep soil water content on transpiration was more obvious. (2) In this paper, models of environmental factors and transpiration at different time scales were constructed, and the fitting degree of models at different time scales was high. (3) Based on this study, it is recommended to use instruments to measure plant transpiration at small scales, while plant transpiration can be calculated by monitoring fewer environmental factors at large scales, which can greatly improve efficiency and reduce the cost of monitoring water consumption of transpiration.

Abstract:The change of water conservation function has an important impact on the ecological hydrology of the basin and the safety of water supply, A stable and good water conservation function is the foundation of the high-quality development of the regional economy and society. Based on the InVEST water yield module, the water conservation model and the pixel-by-pixel linear fitting, we simulated the temporal and spatial variation of water conservation in Qinling Mountains and the north and south slopes of Qinling Mountains from 1981 to 2015, analyzed the response of water conservation to climate change, and explored the evolution trend of water conservation under the background of climate fluctuation. The results show that: (1) The water conservation in Qinling Mountains showed a declining trend over the past 35 years, with an annual change rate of -1.44 mm, and the declining trend of water conservation on the northern slope of Qinling Mountains was greater than that on the southern slope of Qinling Mountains. (2) In recent 35 years, the trend of spatial changes in water conservation in Qinling Mountains had spatial heterogeneity, except for the upper reaches of the Yudai River, the upper reaches of the Muma River and the upper reaches of the Chu River on the suoth bank of the Han River, where the average annual water conservation increased slightly, the other river basins showed an overall downward trend, and the downward trend of water conservation in the central Qinling Mountains was greater than that in the peripheral regions. (3) Precipitation reduction and increased reference evapotranspiration were the main factors affecting the decrease of water conservation function in Qinling Mountains. Under the background of warm and dry climate, the water conservation of Qinling Mountains may further decline. Mastering the temporal and spatial variation characteristics of regional water conservation function has guiding significance for scientific assessment of regional water security, prediction of future water resources change trend and water resources management under the background of climate change.

Abstract:In order to understand the temporal and spatial changes of extreme climate in Guizhou Province and its impact on NDVI of vegetation, the extreme climate index of Guizhou Province from 1961 to 2020 was analyzed by combining box chart, correlation analysis, Sen+MK and other methods. The results show that: (1) The change range of night index is larger than that of day index, the extreme high temperature index is increasing, the extreme low temperature index is decreasing, and the climate is warming as a whole. Except that the SU25 (summer days) in Chishui River Basin decreased significantly by -0.08 d/a, the high temperature index increased significantly in other basins, while the low temperature index decreased significantly. (2) The change range of magnitude index is larger than that of intensity index. The annual total precipitation is decreasing, but the heavy precipitation and extremely heavy precipitation events are increasing; The intensity index in the central and southern Panjiang River Basin failed to pass the significance test, and the magnitude index had the largest change rate in the Yuanjiang River Basin. (3) The low values of temperature and precipitation persistence index are concentrated in Niulan River and Hengjiang River Basin; CSDI (cold duration index), WSDI (heat duration index) and CDD (continuous drying index) failed to pass the significance test; GSL (crop growth period) increased significantly at 0.26 d/a. (4) In recent 21 years, extreme high temperature index mainly promoted vegetation growth and was most affected by TN90P (warm night days); The extreme low temperature index was mainly inhibited and was most affected by TN10P (cold night days); The temperature persistence index is mainly promoted and is most affected by WSDI. Among the extreme precipitation indexes, the precipitation intensity and magnitude indexes are mainly promoted and are most affected by R25 mm (days above heavy rain) and R99P (extremely strong precipitation). The precipitation persistence index is mainly inhibited and is greatly affected by CDD (continuous drying index).

Abstract:The SCS-CN model is one of the most widely method for estimating surface runoff, which can quickly assess the effects of different ground covers on precipitation-runoff relationships. To explore the applicability of the Soil Conservation Service Curve Number Model under artificial grazing measures in the Loess Plateau region, to improve the understanding of the impact of vegetation restoration on water resources in the Loess Plateau, and to provide a theoretical reference for the estimation of surface runoff from artificial grazing in the Loess Plateau, this paper selects data from 73 rainfall runoff events in seven runoff plots at the Luoyugou test site of the Tianshui Soil and Water Conservation Experiment Station of the Yellow River Water Conservancy Commission, and uses the step-size method to estimate the runoff from artificial grazing in the Loess Plateau. The runoff curve number (CN) and the initial abstraction ratios (λ) of the standard SCS-CN model were optimized by the step method. The results showed that: (1) The optimal initial abstraction ratios value for artificial grazing was 0.15, while that for control farmland was 0.18; (2) The difference of curve number values for different species of pasture was not significant, about 79, and that for control farmland was 81, indicating that the curve number values recommended by the U.S. Soil Conservation Service were applicable to the calculation of artificial pasture runoff on the Loess Plateau, but the the initial abstraction ratios values needed to be optimized and rate determined according to the actual situation; (3) The S values were modified according to the previous soil moisture S value was corrected according to the previous soil moisture condition, and the simulation effect was more satisfactory, and the modified SCS-CN model was applied to the semi-arid artificial grazing area of Loess Plateau.

Abstract:Soil moisture content of Robinia pseudoacacia plantation was monitored at fixed points to investigate the distribution and deficit degree of soil moisture of R. pseudoacacia plantation at different ages. Using the method of spatial sequence instead of time successional sequence, 10, 15, 25 and 40 years R. pseudoacacia plantations were selected as the research objects, and farmland (0 years) was served as control to investigate and analyze the distribution of soil moisture content in the 0-200 cm soil layer. The results showed that the average soil moisture content was in order of 0 years (18.80%)＞10 years (16.43%)＞15 years (15.47%)＞40 years (13.87%)＞25 years (13.38%). The soil moisture deficit was found in all stands and showed an increase trend with the increasing of stand age. The average degree of soil moisture deficit was 19.38%, the highest value was observed in the 25 years plantation (27.76%), and there was a slight recovery in the 40 years plantation (25.80%). The variation degree of surface soil water was the largest, and it increased with the increasing of stand age. The four levels of rapid change layer, active layer, sub-active layer and relatively stable layer were only observed in the 40 years plantation. The above research results could provide a certain theoretical basis for vegetation ecological restoration and scientific management of plantations on the Loess Plateau.

Abstract:The Grain for Green Project significantly changed the land use in Yan'an City, and then improved the ecological environment of Yan’an City. The evaluation of the ecological environment change of this process is beneficial to the subsequent ecological protection and planning decisions. Based on existing research, the land use types, and the natural and social statistical data from 1990 to 2020, this study explored the spatial-temporal variation and impact factors of ecosystem service value (ESV) in Yan’an City before and after the implementation of the project of Grain for Green by using temporal information entropy model and geographical detector. The results showed that: (1) From 1990 to 2020, the total ecosystem service value of Yan’an City increased by 770 million yuan, with an increase of about 32.42%. The value of forest ecosystem services increased by 1.125 billion yuan, with an increase of 80.54%, which was the main contributor to the growth, and the value of regulatory services accounted for 50%. (2) The overall spatial distribution pattern of ecosystem service value in Yan’an city was "high in the south and low in the north". ESV increased in 25.1% of the region, distributed in the north and south of Yan'an; ESV decreased in 6.4% of the region, distributed in the suburbs of each district and county. (3) Normalized difference vegetation index (NDVI) was the main impact factor of spatial variation of ESV, and the synergistic effect of various factors jointly affected the spatial variation of ESV in Yan’an City.

Abstract:The standardized precipitation index (SPI) and standardized soil moisture index (SSI) were used to calculate monthly precipitation and soil moisture in Guizhou Province from 1980 to 2020. Based on the run-length theory, transmission response rate (Rr) and state transition probability matrix, the changes of agricultural and meteorological drought characteristics and their response relationship were investigated. The results showed that: (1) The duration and intensity of agricultural drought in Guizhou Province were longer than that of meteorological drought, and the spatial variation of drought duration was more significant than that of meteorological drought, but the intensity of drought was single. (2) At the seasonal scale, the response of agricultural drought to meteorological drought was most sensitive in spring, followed by summer and autumn, and weak in winter. Under different geomorphic types, the response degree was higher in semi-karst low mountain in spring and winter, in peak cluster valley in summer, and in non-karst area in autumn. Under different cutting depths, Rr was higher with the deeper surface cutting in spring and autumn. The opposite was true in summer and winter. (3) During 1980s—2010s, different geomorphic types had different degrees of probability transition, in which the seasonal transition was active and low in spring and winter, and the transition was mainly "low to high" in summer and autumn. The transition probability was low in summer and high in autumn. At different cutting depths, the shallow cutting depth and the deepest cutting depth had low transfer activity and high probability in each season, while the other cutting depths had active transfer but low probability.

Abstract:This study aimed to quantitatively reveal the effect of rice straw returning and temperature on soil organic carbon mineralization, priming effect, and temperature sensitivity of karst yellow rendzina in Guizhou Province. Taking the typical karst yellow rendzina in karst region of Guizhou Province as the research object, the rice straw labeled with ¹³C stable isotope and soil culture experiment was used to study the mineralization of rice straw added and original organic carbon, the priming effect of rice straw on soil original organic carbon, and temperature sensitivity coefficient Q₁₀ of soil organic carbon at the temperature of 15, 25 and 35 ℃. The results showed that the peak of mineralization rate of soil organic carbon, total organic carbon, rice straw organic carbon and soil original organic carbon occurred at the first day of the cultivation at temperature from 15 to 35 ℃ and 0 to 60 days. Moreover, the mineralization rates of soil total organic carbon, rice straw organic carbon and soil original organic carbon decreased fast in 1 to 30 days, and gradually flattened out during 30 to 60 days. The increase of temperature significantly increased the mineralization rate and cumulative mineralization amount of soil organic carbon, total organic carbon, original organic carbon, and rice straw organic carbon in soils. Rice straw had a significant positive priming effect on soil organic carbon mineralization during the whole cultivation period, and the positive priming effect was intensified with increasing temperature. Respectively at the end of the soil culture at 15, 25 and 35 ℃, showing that the priming effect increased, decreased, increased and first increased and then decreased respectively with the increases of temperatures, which varied with different characterization methods. At the temperature of 15, 25 and 35 ℃ to total soil organic carbon mineralization rate and cumulative soil organic mineralization amount, respectively, which decreased first, then increased, and then decreased with the increase of culture time, but the inflection points of two characterization methods and at the three culture temperature occurred at different times. The contribution of rice straw to the mineralization rate and cumulative mineralization amount of soil organic carbon at 15 and 25 ℃ were of little difference yet both significantly higher than that at 35 centigrade for the first day; the contribution of rice straw to the mineralization rate and cumulative mineralization amount of soil organic carbon were basically similar at 25 and 35 ℃ and both significantly higher than that at 15 centigrade for the fifth day; it was that those at 25 centigrade were significantly higher than those at 35 ℃, and the same for 35 ℃ than 15 ℃ for others days. The temperature sensitivity coefficients of soil organic carbon mineralization rate Q_10,V were between 1.01 and 2.60 and between 1.39 and 3.12, respectively, and those of soil organic carbon mineralization cumulative amount Q_10,F were between 1.50 and 2.60, and 1.39 and 2.17 for the two temperature systems of from 15 to 25 ℃ and 25 to 35 ℃, respectively, for soil without rice straw addition. Temperature sensitivity coefficients Q_10,V of total organic carbon mineralization rate ranged from 1.09 to 2.18 and 1.05 to 1.90, respectively, and the values temperature sensitivity coefficients of Q_10,F of total organic carbon mineralization cumulate amount ranged from 1.09 to 1.73 and 1.05 to 1.49, respectively, for soil with rice straw addition. The fact that temperature sensitivity of soil organic carbon mineralization increasing with the increase of temperature changed to decreasing with the increase of temperature could buffer the increase of CO₂ emission caused by global warming to some extent. These results and conclusions provide reference for soil straw returning, soil carbon sequestration, soil organic carbon management, and soil organic carbon pool prediction in Karst farmland of Guizhou Province and are of great significance to enrich the characterization and in-depth understanding of soil organic carbon priming effect and temperature coefficient Q₁₀.

Abstract:The status of lake water pollution has an indicative significance for the water function of lakes. In this study, we collected the data of total nitrogen and phosphorus concentrations, human population and economy in 14 typical lakes between 2010 and 2018 across the whole country. The characteristics of the changes in nitrogen and phosphorus concentrations and water quality were analyzed in relation to human activities. The results showed that: (1) In the past 10 years, total nitrogen and phosphorus concentrations in China’s typical lakes tended to have a slightly decreasing trend. (2) The regional differences of lake water quality were significant, the lakes of East Limnetic Region showed poor water quality, the lakes of Tibet-Qinghai Limnetic Region showed the best water quality conditions. In contrast, there were great differences in water quality within the Yungui Limnetic Region. (3) Human activities had a great impact on nitrogen and phosphorus concentrations in China’s lakes. Population density, industry and construction exerted a significant impact on the total nitrogen and phosphorus concentrations. We suggested that controlling industrial wastewater by the government could reduce lake pollution.

Abstract:Taking the soil environment in Mitika Wetland National Nature Reserve as the research object, based on the completion of on-site sample collection and index analysis and determination, the statistical parameters of soil fertility indexes were studied, and then soil fertility of different soil types in the Mitika Wetland National Nature Reserve was studied. The results demonstrated that the comprehensive soil fertility coefficient (F) in the study area followed the order of alpine meadow soils (1.72)＞ alpine shrub meadow soils (1.66)＝frigid desert soils (1.66)＞bog soils (1.56)＞skeletal soils (1.43). Except the alpine meadow soil belonged to fertile grade, the other four types soil belonged to the general grade. The non-parametric test results of multiple independent samples indicated that soil bulk density, organic matter content, cation exchange capacity, TOC, soil moisture and soil salinity in the study had a certain correlation with soil type, however, pH, content of available potassium, available phosphorus and ammonia nitrogen were unrelated to soil type. Overall, the soil fertility of Mitika Wetland located in northern Tibet with high cold and high altitude was comparable to that of cultivated land and artificial afforestation areas in the other regions of Tibet.

Abstract:In order to explore the effects of biochar application on soil moisture storage, heat preservation and fertilizer conservation in saline soil during freezing-thawing period, taking saline soil as the research object, in situ freezing-thawing tests of field plots were carried out in the Hetao Irrigation Area for two consecutive years, the biochar dosages were set as 15 t/hm² (D15), 30 t/hm² (D30) and no biochar (CK). The results showed that under the freezing-thawing conditions, the vertical distribution of water in 0—40 cm soil was more obvious than that in 40—100 cm soil, and the water storage capacity was greater. In addition to the decrease of soil water storage at 0—40 cm by applying biochar in the initial freezing period of the first year of experiment, the water-holding effect of biochar gradually appeared with the increase of application time. Compared with CK, D30 treatment was more beneficial to soil water retention. Applying biochar could suppress the variation of soil temperature in freezing-thawing period and reduce the dispersion degree of soil temperature change in thawing period. Compared with the control, the average soil temperature of 0—40 cm in the freezing-thawing period of 2 years was increased by 0.8~1.6 ℃ under biochar treatment. After two years of freezing-thawing, the soil freezing index of each treatment was CK > D15 > D30, and the melting index was D30 > D15 > CK. In the freezing-thawing period, the application of biochar enriched the soil nutrient content and reduced the soil nutrient loss from 0 cm to 40 cm in various freezing-thawing stages. The contents of available K, alkali-hydrolyzable N and available P increased by 3.1%~38.1%, 1.3%~44.6% and 5.4%~80.4%, respectively. Organic carbon density increased by 2.0%~22.4%, and D30 treatment had the most obvious improvement effect. The application of biochar improved the hydrothermal fertilizer status of saline soil in freezing-thawing period, and provided a good environment for the growth and reproduction of crops in the next year. The application effect was better when the amount of biochar was 30 t/hm².

Abstract:In order to assess the influence of land use on soil carbon pool, natural grassland, artificial woodland (directly converted from natural grassland) and cropland (reclaimed from natural grassland) in Chernozem region of Northeast China, were taken as research objects. A total of 45 soil samples were collected from these three land use types. Five soil pedogenic horizons (A, AB, B_K, BC and C) in 0—100 cm soil were collected. Soil organic carbon (SOC), water soluble organic carbon (WSOC), light fraction organic carbon (LFOC), and heavy fraction organic carbon (HFOC) contents were determined. The results showed that the contents of SOC, LFOC, and HFOC were mainly distributed in horizon A, but the content of WSOC was the highest in horizon B_K, which was 0.27 g/kg. From horizon A to horizon C, SOC and its components contents of the three land use types all showed a decreasing trend, but the decreasing degree was obviously different. The grassland decreased slowly, the woodland decreased sharply, and the cropland decreased gradually. The contents of WSOC, LFOC, HFOC, and SOC decreased by 34% and 48%, 20% and37%, 7% and 5%, 10% and 16%, respectively, after the grassland were converted into woodland and cropland. After grassland was converted to woodland and cropland, WSOC/SOC and LFOC/SOC decreased significantly but HFOC/SOC increased, indicating that the content of active organic carbon decreased rapidly. Land use types and soil horizons had significant effects on SOC, WSOC and LFOC, and had strong superposition effects on SOC and HFOC. At the same time, soil physical and chemical properties also affected SOC, WSOC, LFOC and HFOC to some extent. Rational land use management policies should be formulated to protect natural grassland from destruction, and play an important role in carbon sequestration of grassland ecosystem.

Abstract:In order to explore the regulation effects of straw return replacing the application of potassium fertilizer on dryland summer maize—winter wheat rotation system, four treatments including no fertilizer (CK), nitrogen and phosphorus fertilizer (NP), nitrogen, phosphorus and potassium fertilizer (NPK), nitrogen and phosphorus fertilizer plus straw returning (NPS) were selected based on the long-term located field experiment which started in 2007 at dry farming platform (Luoyang) of Chinese Academy of Agricultural Sciences. We investigated the grain yield, water and fertilizer use efficiency of summer maize and winter wheat rotation system from 2015 to 2020, as well as the content of organic matter, total nitrogen, available phosphorus and available potassium in 0—60 cm soil layer, and soil nitrate accumulation in 0—260 cm soil layer at harvest of winter wheat in 2020. Compared with NP, NPK significantly increased the content of available potassium in the 0—60 cm soil layer, but did not change the grain yield, water and fertilizer use efficiency of summer maize and winter wheat rotation system, while NPS was beneficial to improve soil nutrient, and significantly increased the grain yield, water and fertilizer use efficiency in summer maize and whole year. Compared with NPK, NPS significantly increased the organic matter content by 10.68% in 0—20 cm soil layer, the grain yield, water use efficiency, and the agronomic efficiency of N(P) fertilizer in summer maize and whole year increased by 20.91%, 33.77%, 114.39% and 13.60%, 13.63%, 65.41%, respectively, but significantly decreased the available phosphorus content by 7.43% in 0—20 cm soil layer and the available potassium content by 14.31% in 0—60 cm soil layer. Compared with NP and NPK, the nitrate accumulation in NPS was increased by 37.14% and 25.92% in 0—100 cm soil layer, and decreased by 32.33% and 21.64% in 160—260 cm soil layer. In conclusion, straw return could be used for replacing the application of potassium fertilizer on the basis of N and P fertilizer, because it could not only increase the content of organic matter and total nitrogen in 0—20 cm soil layer and nitrate accumulation in 0—100 cm soil layer, thereby improving the grain yield, water and fertilizer use efficiency in summer maize and whole year, but also reduced the risk of soil nitrate leaching to deep layer. Therefore, NPS was a suitable measure in dryland summer maize—winter wheat rotation system, but it should be paid more attention to the problems of the decrease of available phosphorus and available potassium in soil.

Abstract:In order to explore the feasibility of straw iso-nitrogen replacement of chemical fertilizer and its effect on soil moisture and dry matter accumulation of maize, field experiments were carried out for six consecutive years. 2020 was the fifth year of fertilization, 2021 was the sixth year of fertilization, and 225 kg/hm² iso-nitrogen amount was maintained. Five fertilization treatments were set up, which were CK (single fertilizer, 100% fertilizer nitrogen), S25 (25% straw nitrogen +75% fertilizer nitrogen), S50 (50% straw nitrogen +50% fertilizer nitrogen), S75 (75% straw nitrogen +25% fertilizer nitrogen) and S100 (100% straw nitrogen), and the effects of straw equal nitrogen instead of chemical fertilizer on soil water storage, water use efficiency, soil water consumption,soil nutrient and dry matter accumulation of maize were studied. The results showed that: (1) In the experiment of 2020, soil water storage in 0-80 cm soil layer was S50>S25>CK>S100>S75 before sowing and during filling stage, it was S50>S25>CK>S75>S100 in trumpet and tasseling stage. At maturity, it was S50>CK>S25>S100>S75. In the test of 2021, soil water storage in 0-80 cm soil layer was S25>S50>S100>CK>S75 in the large trumpet period. At tasseling stage, soil water storage in 0-80 cm layer was S25>S50>CK>S100>S75. (2) In the experiment of 2020 and 2021, during the whole growth period of maize growth, the variation trend of soil water storage in each layer of 0-200 cm in each treatment group with soil depth was consistent, and soil water storage of S25 and S50 treatments were larger than that of CK, while soil water storage of S75 and S100 treatments were smaller than that of CK. (3) In 2020 and 2021, compared with CK, there were no significant differences in soil water consumption and water use efficiency of each straw replacement treatment group, but in 2021, soil water consumption of S50 was significantly higher than that of S100, increased by 5.00%. (4) In the experiment of 2020, the content of soil organic matter and alkali-hydrolyzable nitrogen in each straw replacement treatment group had no significant difference compared with CK, and the content of soil available phosphorus in S100 treatment was significantly lower than that of CK by 50.75%. In 2021, compared with CK, soil organic matter content of S25, S50, S75 and S100 significantly increased by 27.40%, 38.13%, 36.30% and 22.60%, respectively. Soil alkali-hydrolyzable nitrogen content of S50 increased by 27.74% compared with CK. Compared with CK, soil available phosphorus content of S25, S50, S75 and S100 significantly declined by 31.48%, 22.22%, 30.56% and 45.68%, respectively. (5) In the experiment of 2020, in each growth period of maize, there was no significant difference in dry matter accumulation per plant treated with straw instead of chemical fertilizer compared with CK. However, in the experiment of 2021, the dry matter accumulation per plant in S50 treatment was the highest in tasseling stage, filling stage and maturity stage, with a increase by 22.39%, 34.06% and 12.58%, respectively, compared with CK. Compared with CK, the dry matter accumulation per plant of S75 increased by 22.49% and 12.11%, respectively, in the filling stage and maturity stage. In general, dry matter accumulation per maize plant increased first and then decreased with the increasing of proportion of straw replacing fertilizer. In order to ensure soil moisture and nutrient, as well as dry matter accumulation, S50 was a potential way to replace chemical fertilizer under the conditions of this experiment.

Abstract:In order to study the high-yield, high-efficiency and high-quality nitrogen application rate under drip irrigation in the Huang-Huai-Hai Plain, a field trial was conducted using two high-yield varieties Jimai-22 and Yannong-1212 with 4 nitrogen levels, 0, 150, 210 and 270 kg/hm², under field drip irrigation during 2018-2020. The photosynthetic physiological characteristics, grain filling characteristics and grain yield were studied. The results showed that nitrogen application could significantly increase the SPAD value of the upper three leaves of winter wheat. Appropriate nitrogen application could significantly increase the relative chlorophyll content and flag leaf net photosynthetic rate (P_n) in the middle and late stages of grain filling. The SOD activity of wheat flag leaves showed a single peak curve. The SOD activity of each nitrogen treatment reached the maximum at 14 days after anthesis, and the SOD activity of N0 treatment reached the maximum at 7 days after anthesis. Under N2 nitrogen level, the flag leaf SOD activity of the two varieties was the highest in the middle and late filling stages. An appropriate rate of nitrogen application could reduce leaf membrane lipid peroxidation in late growth period and leaf MDA content, prolong leaf function period, and improve photosynthetic performance in late growth period. With the increases of nitrogen application rates, the grain filling rate and maximum theoretical 1000-grain weight of the two varieties increased first and then decreased. The Tm of the non-nitrogen treatments was relatively earlier than that of the various nitrogen treatments. For the maximum grain filling rate and maximum theoretical 1000-grain weight, Jimai-22 and Yannong-1212 appeared as the largest under N1 and N2 treatments, respectively. The yields of the two varieties first increased and then decreased with the increases of nitrogen application rates, and both were the largest at N2 treatment. The yield of Jimai-22 was higher than that of Yannong-1212 under N0 and N1 levels, but lower than that of Yannong-1212 under N2 and N3 levels, indicating that Yannong-1212 was more sensitive to nitrogen fertilizer and had a higher yield potential under high fertility and water conditions while Jimai 22 had a strong adaptability with a better performance under the low and medium fertilization. There were differences in the nitrogen responses on the yield components of the two varieties. The yield of Jimai-22 mainly depended on the number of ears and grains per ear, while the yield of Yannong-1212 was of a synergistic effect of the number of ears, grains per ear, and 1 000-grain weight. Nitrogen application significantly increased the protein, wet gluten, and sedimentation value of the two varieties. The quality of Yannong-1212 increased with the increases of nitrogen application in the range of 0~150 kg/hm², while Jimai-22 increased with the increases of nitrogen application in the range of 0~210 kg/hm². In summary, under this experimental conditions, the 210 kg/hm² of nitrogen applied under drip irrigation resulted in better photosynthetic characteristics, enzyme activity, grain filling characteristics, yield and quality of both cultivars and therefore should be the optimal nitrogen application rate.

Abstract:In this study, the effects of different application positions of starter phosphate fertilizer on seedling growth, root morphological development and the spatial matching degree of soil phosphorus nutrients and root system of drip-irrigated maize were studied through the simulation experiment. The purpose of this study was to provide a theoretical basis for clarifying the best application position of starter phosphate fertilizer and its effect on maize seedling growth. Using root box, four starter phosphate fertilizer treatments were set up, which were (1) simulated drip application (T1), (2) starter fertilizer applied at 5 cm horizontally to seed and 5 cm below the seed, by hole application (T2), (3) starter fertilizer applied at 5 cm horizontally to seed and 12 cm below the seed, by hole application (T3) and (4) no starter fertilizer (CK). According to the field starter phosphate fertilizer application amount (P₂O₅ 30 kg/hm²), the amount of starter phosphate fertilizer was P₂O₅ 0.2 g/kg soil. The effects of different treatments on maize seedling growth, root morphological development, spatial matching degree of soil phosphorus nutrients and root, and evaluation of spatial matching degree of phosphorus nutrients between root and soil were analyzed. The results showed that at 14 and 21 days after maize emergence, the application of starter phosphate fertilizer significantly increased the total root length, total surface area, and the number of primary and secondary lateral roots. The overall performance was the highest in T2, followed by T1 and T3, and the lowest in CK. But there was no significant difference in the number of maize primary roots and main radicle root length among the treatments. At 21 days after maize emergence, the soil available phosphorus mainly distributed in the range of 0—9 cm vertically and 0—18 cm horizontally in T1, in the range of 3—12 cm vertically and 0—11 cm horizontally in T2 treatment, and in the range of 11—20 cm vertically and 0-11 cm horizontally in T3 treatment. The root was mainly concentrated in the 0—9 cm soil layer in T1, and in the soil layer of 5-15 cm vertically and 0-12 cm horizontally in T2 treatment, and in the soil layer of 12—18 cm vertically and 0—9 cm horizontally in T3 treatment. The spatial matching degree of root and soil phosphorus nutrient distribution was T2>T3>T1. At 7 days after maize emergence, there was no significant difference in the dry weight and phosphorus nutrient accumulation of maize among the four treatments. At 14 and 21 days after maize emergence, the dry weight and phosphorus nutrient accumulation of maize in the treatments with starter phosphorous fertilizer were significantly higher than those of CK, and the dry weight and phosphorus uptake of T2 were the highest and significantly higher than those of T1 and T3, but there was no significant difference between T1 and T3. Applying starter phosphate fertilizer at 5 cm below the seed showed the best effect on maize growth. The main reason was that phosphorus nutrient distribution was best fit the root distribution pattern in soil, this was benefit for root absorption of phosphorus. At the same time, it promoted the proliferation of maize lateral roots in fertilizer application area, expanded the contact area between the root and the soil, and increased the phosphorus absorption and biomass of maize. The application of starter fertilizer by drip irrigation could also promote root growth, however, the root distribution was shallow.

Abstract:To investigate the nitrogen absorption and utilization patterns of sunflower under different levels of nitrogen application in saline farmland, a field micro-area experiment was conducted using ¹⁵N isotope tracing technique, and three levels of nitrogen application (N1=150 kg/hm², N2=225 kg/hm², N3=300 kg/hm²) were designed with no nitrogen application treatment (N0) as the control. The ¹⁵N isotope abundance and total nitrogen (TN) content of sunflower and 0-100 cm soil layer were measured at maturity of sunflower to study the fate and utilization mechanism of fertilizer nitrogen in each treatment. The results showed that the nitrogen absorption of sunflower increased with the increasing of nitrogen application, and the nitrogen uptake of the sunflower at maturity increased significantly by 38.7% at the N2 level compared with no nitrogen application. The contribution of soil N and fertilizer N to the nitrogen uptake of the sunflower in the current season was 84.9% and 15.1%, respectively. At the N2 level, the contribution ratio of fertilizer N increased by 35.7% compared with N1, and the contribution ratio of soil N decreased by 4.3% compared with N1. The residual fertilizer N decreased with the increasing of soil depth, and 47.4% of residual fertilizer N in the soil mainly concentrated in the 0-20 cm soil layer. At different N application levels, the fate of fertilizer N showed loss rate > residual rate > utilization rate, and under the nitrogen application level of N2, N utilization rate significantly increased by 22.7% and 14.6% compared with N1 and N3, respectively, and the soil residual rate reduced by 8.5% and 8.6% compared with N1 and N3, respectively. Considering the nitrogen uptake and utilization of sunflower and the nitrogen residue in soil, under 225 kg/hm² of nitrogen application, the nitrogen utilization rate was 27.4%, the nitrogen residue rate was 32.3% and the nitrogen loss rate was 40.3%, which was a more suitable nitrogen application rate for moderately salinized farmland.

Abstract:Phosphorus is a key nutrient element limiting grassland ecosystem productivity. It is of great significance to clarify soil phosphorus distribution and its influencing factors for maintaining sustainable development of grassland ecosystem on the Qinghai-Tibet Plateau. In this study, we collected soil samples from different grassland types (i.e. meadow steppe, typical steppe, and desert steppe) along the horizontal transect of the Qinghai-Tibet Plateau from northwest to southeast. The distribution characteristics and influencing factors of soil total phosphorus, available phosphorus, and inorganic phosphorus and organic phosphorus fractions were investigated. The results showed that the total and available phosphorus contents in soil were the highest in meadow steppe, followed by desert steppe and typical steppe. The inorganic phosphorus fraction of all grassland types was dominated by acid-soluble inorganic phosphorus; the organic phosphorus fraction of meadow steppe soil was dominated by sodium hydroxide organic phosphorus, while acid-soluble organic phosphorus fraction was dominated in typical and desert steppe soils. Among different grassland types, the contents of water-soluble, sodium bicarbonate, sodium hydroxide inorganic phosphorus and various forms of organic phosphorus in the meadow steppe soil were significantly higher than those in the typical and desert steppes, while the content of acid-soluble inorganic phosphorus in the desert steppe soil was significantly higher than that in the typical and meadow steppes. Redundancy analysis showed that soil organic carbon, average annual rainfall were the main factors affecting the total and available phosphorus, average annual rainfall and free iron oxide were the main factors affecting inorganic phosphorus fractions, while pH, average annual temperature, above-ground biomass and average annual rainfall were the main factors affecting the organic phosphorus fractions. Structural equation model indicated that grassland type had a direct effect on both inorganic and organic phosphorus fractions, and annual average temperature and bulk density also had a direct effect on inorganic phosphorus fractions, while altitude, annual rainfall and annual average temperature had indirect effects on inorganic and organic phosphorus fractions through grassland types. The results of this study are of great significance for the effective management of soil phosphorus nutrient and the sustainable utilization of grassland resources on the Qinghai-Tibet Plateau.

Abstract:An in-depth analysis of China's cropland use carbon source / sink can provide data reference in the field of cropland for the realization of the "double carbon" goal. Taking mainland China as the study area while excluding Hong Kong, Macao, Taiwan, and Tibet because of data unavailability, the carbon emission and carbon sequestration of cropland use in 30 provinces (cities and autonomous regions) of China from2000 to 2019 were calculated. and the net carbon effect was analyzed according to the difference between emissions and sequestration, then its spatial and temporal evolution characteristics were described. Furthermore, the coupling coordination degree and the improved Tapio coupling index were used to explore the relationship between net carbon effect and agricultural output value. The results showed that: (1) In the past 20 years, the average carbon emission of cropland use was 2.33×10⁸ t, rising first and then falling, and reaching the peak of 2.63×10⁸ t in 2015. The sequestration increased from 5.19×10⁸ to 7.86×10⁸ t. Accordingly, the net carbon sequestration rose from 3.19×10⁸ to 5.40×10⁸ t, indicating that the cropland use system in China always displayed an increasing carbon surplus, and the carbon sink effect increased over time. (2) In terms of the temporal characteristics, the net carbon sequestration experienced three stages fluctuating, high speed growth and stable growth. From the perspective of spatial pattern, the net carbon sequestration exhibited gradual decline from east to west. (3) In terms of quantity, the relationship between the net carbon sequestration and agricultural economy evolved from overall imbalance to partial coordination. From the perspective of speed, the growth relationship of the two was in economy-leading coupling in most years, and the provincial coupling status of the two evolved from coexistence of several types to the economy-leading coupling. Consequently, it’s necessary to accelerate the transformation of cropland use mode from agricultural materials driven to technology driven. Besides, we should promote the carbon emission reduction of the whole industrial chain of the planting industry, and promote the emission reduction and the increase of sources in large emission provinces by categories and batches.

Abstract:Exploring the characteristics of soil water evaporation after the combination of mine waste residue and farmland soil and the effect of mulch on soil water evaporation is of practical significance to the management and improvement of soil water in mine restoration. Using the abandoned residue of limestone mine wasteland and nearby farmland soil as compound materials, the combination volume ratios of 0∶10 (T1), 3∶7 (T2), 5∶5 (T3), 7∶3 (T4) and 10∶0 (T5) were set. The soil column method was used to simulate the process of soil water evaporation under field conditions to explore the effect of compound ratios on soil water evaporation and the water retention capacity of different mulches. The results showed that: (1) The water content of surface mixed soil before and after the experiment was T1 > T2 > T3 > T4 > T5. The daily evaporation in the middle stage of evaporation and the cumulative evaporation at the end of evaporation decreased significantly with the increase of the volume ratios of abandoned slag. There was no significant difference in daily evaporation between different mixed soils in the early and later stages of evaporation. (2) Among the meteorological factors, the influence of temperature and wind speed on soil water evaporation was greater than that of solar radiation, and the effect of relative humidity was not significant. In soil physical properties, except for capillary porosity and non-capillary porosity, there was a significant correlation between soil water evaporation and other factors. (3) Adding mulch to bare land could reduce water evaporation. According to the analysis of evaporation and evaporation rate, gravel mulch (Diameter 2~4 cm, thickness 5 cm) had the best effect. (4) The best water conservation scheme of soil reconstruction in limestone mine wasteland was abandoned slag∶farmland soil of 3∶7 volume ratio and covered with gravel. The study could provide theoretical support for the local treatment of quarrying wasteland.

Abstract:Cadmium (Cd) and arsenic (As) are the dominant heavy metal pollutants widely existing in the soil environment, which have the characteristics of non-degradability and bioaccumulation. Therefore, remediation of Cd and As pollution should be carried out in time. The study took the farmland soil polluted by medium and light Cd and As in Hunan Province as the object, and selected the local dominant plants. In the field experiment, the compound passivator of biochar and nano-zero-valent iron were added, and the matching planting modes of different plants (rape-broad bean and corn-ramie) were used, and the through the field experiment, the remediation effect of plant rotation and the application of compound passivator on Cd and As pollution in soil was explored. The results showed that: (1) The plant rotation models (fava bean-rapeseed, corn-ramie) were more favorable to the fixation of Cd and As in the soil, and the best fixation effect of Cd and As in the test soil was 45.19% and 19.00% of the original soil, respectively. (2) The compound passivator significantly enhanced the fixation of Cd and As in agricultural soil. The passivation effects on Cd and As were the most obvious when biochar and nano-zero-valent iron were applied in the ratio of 53∶1. (3) Applying compound passivators in intercropping mode could effectively promote the remediation effect of Cd and As contaminated soil. This method was more suitable for the application of remediation engineering of moderate and light Cd and As contaminated soil. The optimal ratio of compound passivators and the use of intercropping pattern provide an experimental basis and theoretical support for the remediation and treatment of Cd and As contaminated soil.

Abstract:The effects of aluminum sulfate and organic materials on the composition and complex of organic carbon in saline-alkali soil were studied by laboratory culture experiments and adding different gradient organic materials (10,20,30,40,50,60 t/hm²) and the same amount of aluminum sulfate (0.2 t/hm²). The results showed that the organic carbon content and active organic carbon content could be significantly increased by applying aluminum sulfate and organic materials. When aluminum sulfate was applied and the amount of organic materials was 30 t/hm², the growth trend of microbial carbon began to slow down, the soil microbial quotient reached the peak, and the Kos value was the lowest compared with other treatments. The application of aluminum sulfate and organic materials can promote the aggregation of soil particles from small to large, and at the same time increase the content of organic carbon in the composite body of each particle. When the application amount of organic materials is 30 t/hm², the soil structure can be obviously changed. In other words, when aluminum sulfate is applied and the amount of organic materials is 30 t/hm², the soil fertility and soil structure of saline-alkali soil can be improved effectively, and the saline-alkali soil can be improved economically and reasonably.

Abstract:It is a big problem that the accumulation of heavy metals in wheat grains from in farmland soil contaminated with cadmium (Cd) and arsenic (As). Using biological simulation method, taking the soil in Cd and As compound polluted area as the research object, the experiment was conducted to explore the effects of biochar addition (C1 and C2 represented 3% and 6% biochar added in contaminated soil) on the accumulation and transport of Cd and As in the system contaminated soil-wheat/maize. The results showed that the addition of biochar significantly reduced the availability of Cd and As in the rhizosphere soil or non-rhizosphere soil in wheat season. And the average contents of Cd and As in wheat grains decreased by 19.25% and 50.70% compared with CK, but the difference was not significant for Cd. For the maize, the biochar treatments of C1 and C2 significantly reduced the contents of Cd and As in the ears, with a decrease of 85.67%, 61.28% and 98.36% and 96.48%, respectively. Furthermore, the biochar addition decreased the translocation and accumulation of Cd and As in the system of wheat-maize, but the treatments had no significant effect on the transport of Cd from straw to grain and Cd accumulation in wheat grains. In conclusion, adding 3% biochar in contaminated soil alleviated the contents of Cd and As in wheat grains and maize ears, and had a more obvious effect on the reduction of heavy metals Cd and As in maize ears. It was better pathway to reduce the translocation and accumulation of Cd and As in the system of contaminated soil and wheat/maize through addition of 3% biochar in soil.