XU Yunfei, JIN Guofeng, DANG Wei, WANG Xijin, LI Chunjiang
Effects of nitrogen and phosphorus fertilizers on vegetation restoration in the towers of the power transmission and transformation project in the Horqin Sandy Land
[Background] The Horqin Sandy is characterized by its fragile ecosystem and high susceptibility to desertification, exacerbated by human activities such as infrastructure development. The construction of transmission towers in this region has disturbed the local environment, making soil and vegetation restoration a challenge. Previous studies have shown that nutrient supplementation, particularly nitrogen and phosphorus fertilizers, can play a crucial role in promoting plant growth in degraded lands. However, the effectiveness of these fertilizers in restoring vegetation in sandy, nutrient-poor soils like those in the Horqin Sandy remains unclear. [Methods] In order to investigate the effects and mechanisms of fertilizer application ways and dosage on vegetation restoration at the tower base of the transmission line in eastern Inner Mongolia, the experiment selected seeds of three herbaceous plant species: Medicago sativa, Elymus nutans, and Leymus chinensis. Three nitrogen levels (0, 100, and 160 kg/hm2) and three phosphorus levels (0, 120, and 180 kg/hm2) were set for the fertilization treatments. The aboveground and belowground biomass of the plants as well as the specific root length, diameter, tissue density, and nitrogen and phosphorus content of the roots were measured. We further analyzed the effect of root changes on plant biomass. [Results] 1) The combined application of nitrogen and phosphorus fertilizers was more beneficial for the aboveground and belowground growth of the three plant species. However, the responds of each species to the application rates of nitrogen and phosphorus fertilizers were different. The optimal nitrogen and phosphorus application rates for M. sativa growth were 100 and 180 kg/hm2 respectively. The optimal nitrogen and phosphorus application rates for E. nutans growth were 160 and 120 kg/hm2 respectively. The optimal nitrogen and phosphorus application rates for L. chinensis growth were 100 and 120 kg/hm2 respectively. 2) According to the structural equation model, fertilization primarily affected belowground biomass by regulating root traits, such as specific root length, nitrogen content, and phosphorus content, thereby influencing aboveground biomass. [Conclusions] Therefore, during the fertilization process, it is crucial to pay more attention to root-related traits of the plants. This research may provide theoretical and technical references for the rapid restoration of vegetation in the ecologically fragile areas of the power transmission line project in eastern Inner Mongolia.
WU Weiting, LIU Zhenting, GAO Guanglei, SUN Zhe, ZHANG Jinxin, WANG Tianbo, CAO Hongyu, DING Guodong
Effects of Bacillus subtilis on the seed germination and seeding growth and physiological characteristics of psammophytes
[Background]Bacillus subtilis is an emerging microbial material which potentially contribute to desertification combating. However, as a typical plant growth-promoting rhizobacteria, its effects on the plant colonization and growth in a desert environment still remain unclear. This study is aimed to investigate the effect of B.subtilis on the physiological characteristics of seed germination and seeding growth of psammophyte. [Methods] The controlled experiments were conducted to determine the seed germination, seeding growth and physiological characteristics of Ammopiptanthus mongolicus and Caragana korshinskii using different bacterial application amount (0, 1, 3, 5, 7 and 10 g/kg). The changes of seed germination and the physiological characteristics of seeding growth were investigated, including contents of chlorophyll, malondialdehyde and proline. [Results] 1) B. subtilis increased the seed germination rate of A. mongolicus and C. korshinskii, and the optimal dosage were 3 and 10 g/kg, respectively. Meanwhile, it had no significant effect on the seedling crown (P>0.05), only 10 g/kg dosage significantly impacted the height of C. korshinskii seedings (P<0.05). 2) B. subtilis significantly affected the physiological and biochemical characteristics of A. mongolicus and C. korshinskii (P<0.05). The chlorophyll content of A. mongolicus significantly increased (P<0.05) and the malondialdehyde and proline of A. mongolicus and C. korshinskii significantly decreased (P<0.05), and the optimal dosage was 5 g/kg. [Conclusions]B. subtilis improves the plant physiological and biochemical characteristics therefore promotes the seeding growth, but this effect is limited with a lagging performance. Moreover, it varies with the bacterial application amount and plant species, the C. korshinskii is more impressionable than A. mongolicus. This improved information will provide theoretical basis and scientific support for desertification combating technology exploration using B. subtilis.
LUO Xin, LU Xianghui, ZHANG Haina, HAN Xiaoxue, XIE Rongxiu
The influence of planting density of Cinnamomum camphora on the morphological characteristics of gullies on red soil slopes
[Background] Rill erosion is the main form of soil degradation, threatening ecological integrity. Studies show that adjusting planting density can affect rill formation on slopes and in forest land. Cinnamomum camphora is an important tree in the southern red soil region, but the impact of its planting density on rill morphology is unclear. This study aims to clarify the rill morphological characteristics under different densities and provide guidance for cultivation and erosion prevention. [Methods] The sample plot was selected in the ecological science and technology park of Nanchang Institute of Technology, which has a suitable climate. Three slope plots were set up, namely 5° (S1), 10° (S2) and 15° (S3), and each slope had three planting densities (D1: 1.5 m×1.5 m, D2: 1.0 m×1.5 m, D3: 1.0 m×1.0 m), totaling nine treatments. The data of the sample plot was obtained through UAV aerial photography and analyzed by Agisoft PhotoScan Professional and ArcGIS 10.8 software. Relevant parameters were extracted to characterize the rill features, and SPSS and Origin were used for data analysis and graphing. [Results] The main results show that: 1) A higher planting density leads to a decrease in the length, width and depth of rills. When comparing D3 with D1, they are reduced by 0.34 times, 0.19 times and 0.31 times respectively. A steeper slope will cause them to increase. When comparing S3 with S1, they are increased by 1.24 times, 0.77 times and 1.91 times respectively. 2) The rill density, complexity, dissection degree, volume and width-depth ratio vary within the ranges of 0.19-1.48 m/m2, 1.01-1.42, 0.01-0.23, 0.06-1.70 m3, and 1.63-3.25 respectively. A higher planting density will increase the width-depth ratio (with an average increase of 7.5%), but decrease other indicators (with an average decrease of 24.7%, 3.4%, 33.6% and 37.1% respectively). A steeper slope will reverse this situation, reducing the width-depth ratio (with an average decrease of 22.7%) and increasing other indicators (with an average increase of 126.6%, 14.7%, 219.1% and 513.65% respectively). 3) The cross-sections of rills are mostly U-shaped. A higher planting density will reduce the cross-sectional area and change the V-shape in the middle of the slope to a U-shape. A steeper slope will increase the cross-sectional area, make the V-shape in the middle of the slope more prominent, and make the upper and lower parts of the slope more likely to be V-shaped but still remain U-shaped. 4) The amount of slope erosion is highly positively correlated with the rill density, complexity and dissection degree (with correlation coefficients of 0.975, 0.991 and 0.988 respectively), and highly negatively correlated with the rill width-depth ratio (-0.937). [Conclusions] The analysis indicates that C. camphor play an important role in inhibiting the formation and development of slope rills. Although the impact of slope is significant, the dwarf forests can still impede it on all slopes. The D3 planting density has the best effect. The research results are conducive to the planting management of dwarf forests and the prevention and control of soil erosion in the red soil hilly area, providing a scientific basis.
WANG Bo, WANG Zhongliang, LI Jianxing, LI Kun, CHEN Pingping, CHEN Shengli, DUAN Qingsong
Selection and allocation of suitable plants in the water-level-fluctuating zone around the Huangdeng Hydropower Station in the three parallel rivers area
[Background] Vegetation restoration is an effective way to reduce soil erosion in the water-level-fluctuating zone and ensure the normal function of the reservoir. The Three Parallel Rivers area is rich in hydropower resources, but the ecological environment is sensitive and fragile. The study on the selection and configuration of suitable plants in the water-level-fluctuating zone the reservoir of Huangdeng Hydropower Station on the Lancang River can provide a basis for the vegetation restoration of the water-level-fluctuating zone of the Huangdeng Hydropower Station, and also provide a reference for the ecological restoration of thewater-level-fluctuating zone in the three parallel rivers area. [Methods] Taking 2 species of algae, 14 herbaceous species and 4 species of trees as the research objects, the experimental area was arranged in the subsidence zone of Huangdeng Hydropower Station and observed for 4 years. [Results] 1) Myriophyllum verticillatum, Hydrilla verticillata, Vallisneria natans and Stuckenia pectinata were difficult to survive in the elevation range of 1 605-1 610 m, Cynodon dactylon could survive in the elevation range of 1 610-1 618 m, and seven herbs of Arundo donax ‘Versicolor’, Cyperus involucratus, Canna indica, Acorus calamus, Phragmites australis, C. dactylon and Chrysopogon zizanioides grew well in the elevation range of 1 618-1 620 m, and the plant height, biomass and coverage of A. donax ‘Versicolor’ were the largest. 2) At the elevation of 1 615-1 618 m, the survival rates of Salix hybrid, Taxodium distichum var.imbricarium,Pterocarya stenoptera and Taxodium ‘Zhongshanshan’ were 100%, 41.67%, 36.67% and 16.67%, respectively, and the adaptability was S.hybrid >T.distichum var. imbricarium > P.stenoptera > T. ‘Zhongshanshan’, and S.hybrid is significantly better than the other three trees. 3) The plant configuration mode of the subsidence zone of Huangdeng Hydropower Station is as follows: 1 586-1 605 m elevation area, it is not recommended to plant plants, 1 605-1 615 m elevation is recommended to plant C.dactylon, 1 615-1 618 m elevation is recommended to plant S.hybrid, M.alba, and C.dactylon, 1 618-1 620 m elevation is recommended to plant A.donax ‘Versicolor’, C.involucratus, C.indica, A.calamus, P.australis, C.dactylon, C.zizanioides; and A.donax ‘Versicolor’, C.involucratus, and C.indica is arranged on the outermost side to improve the landscape effect of the subsidence zone. [Conclusions] The suitable plants have good growth characters and good landscape effects after 4 years of planting in the water-level-fluctuating zone around the Huangdeng Hydropower Station. The model can be applied in the water-level-fluctuating zone of the three parallel rivers area.
LI Hua, ZHENG Lu, WU Sida, CHEN Lin, LI Chaoying, MING Angang, MIN Huilin, HAO Jian
Effects of different tending techniques on the soil erosion and water loss in young plantations
[Background] Soil erosion and water loss in the forest land after clear-cutting and control burning were serious, and it is the limiting factor of sustainable management of plantations. The young forest tending is one of the important measures of plantation management, which can promote the growth of young trees and accelerate the closure of young forest. Different tending techniques have different disturbance degrees to soil, can they effectively reduce soil and water loss in forest land? In this paper, the effects of different tending techniques on the soil erosion and water loss in young plantations after control burning were analyzed. [Methods] Two kinds of tending techniques (brush breaking tending and overall tending) were considered in a control burning site of 30-year-old Pinus massoniana plantation in southern Guangxi. Based on the fixed position observation of the 3 runoff plots of each tending techniques, the soil erosion and water loss were measured from 2018 to 2020. We compared the soil erosion and water loss, and analyzed the relationship between rainfall and runoff depth and sediment loss of the two different tending techniques. [Results] 1) In the first two years after control burning in which the soil erosion and water loss was serious occurred, the annual volume of runoff of brush breaking tending plots were 65.4% and 64.5% of overall tending plots, respectively. The annual amount of sediment loss of brush breaking tending plots were 46.9% and 37.2% of overall tending plots, respectively. In rainy months, the soil erosion and water loss were more obvious or significant lower in the brush breaking tending plots than in the overall tending plots (P＜0.05). In the third year after control burning, the brush breaking tending plots still significantly reduced the soil erosion and water loss in tending months and the whole year. 2) Brush breaking tending treatment increased the minimum rainfall for surface runoff. With the increase of daily rainfall amount, the soil erosion and water loss were significantly lower in the brush breaking tending plots than in the overall tending plots. [Conclusions] In the clear-cutting and control burning site of southern Guangxi, it is effective to prevent soil erosion and water loss by changing tending techniques.
WANG Shuaibing, XIAO Wenxian, XIA Luanjinyue, LI Lan, PENG Shuxian, WANG Keqin, YANG Shudong
Effects of contour reverse-slope terrace on crop growth and development in red soil sloping farmland
[Background] There is serious soil erosion, poor water and fertilizer conservation capacity and low productive force of land on red soil sloping farmland in central Yunnan. To provide a scientific basis for the prevention and control of soil erosion and the improvement of land productivity in sloping farmland in Yunnan province, the effects of contour reverse-slope terrace (CRT) on crop growth and yield in red soil sloping farmland were studied. [Methods] Taking red soil sloping farmland in central Yunnan as the research object, two standard runoff plots (The size is 20 m×5 m, the horizontal projection area is 100 m2) of field sloping farmland at the soil and water conservation monitoring station of Yizhe small watershed in Songhuaba water source area were selected, numbered CK and CRT respectively, where CK was the undisturbed sloping farmland, and CRT was the sloping farmland with two contour reverse-slope terraces. Differences in seedling emergence rates, major growth indices, yields and water use efficiency of soybean and maize seedlings in 2017 (soybean (Glycine max)) and 2018 (maize (Zea mays)) were monitored, and a range of CRT and CK at the same location were selected for comparative studies. [Results] 1) Compared with the standard runoff plots of CK, the emergence rates of soybean and maize in CRT increased at 4, 7 and 10 d, respectively 73.58% and 72.31%,37.08% and 48.50%,4.39% and 4.27%. 2) The plant height, stem diameter and leaf area index of soybean and maize in CRT were higher than those in the standard runoff plots of CK, and the difference in stem size and plant height reached significant level. 3) Compared with the standard runoff plots of CK, the yield of the soybean and maize in CRT increased by 47.55% and 59.12% respectively. 4) Compared with the standard runoff plots of CK, the water use efficiency of the soybean and maize in CRT increased by 32.65% and 43.51%. [Conclusions] CRT may increase the soil water infiltration rate of red soil slope farmland, reduce soil erosion, effectively promote crop growth and development, and significantly improve crop yield and water use efficiency. Therefore, it is urgent to promote CRT in the vast mountainous areas of central Yunnan.
HU Yuwen, JIA Jianbo, SHEN Xinshan, WANG Ziyi, ZHANG Mengjie
Evaluation of different restoration techniques and their effectiveness on coal gangue slopes in Wuhai city
[Background] The coal mining activities in Wuhai have resulted in a multitude of gangue slope management challenges. The efficacy and practicality of various restoration methods for ecological rehabilitation of these slopes remain undetermined. Identifying suitable restoration techniques for these slopes is crucial, as it can offer valuable insights for analogous slope restoration endeavors. [Methods] Four distinct restoration techniques were implemented on coal gangue slopes, each spanning 26-36 m in length. At various slope positions (upper, middle, and lower), 2 m×2 m plots were established to assess species composition, plant height, and vegetation coverage. Soil samples from the 30 cm were collected, and conventional analytical methods were employed to measure species diversity indices, vegetation water retention, and litter accumulation. The entropy value-TOPSIS model was subsequently applied to assess the restoration techniques. [Results] 1) The restoration of coal gangue slopes in this region has shown that legumes and composites thrive well, suggesting a strong local adaptability. 2) Compared to natural restoration, artificial restoration techniques not only increase vegetation height, coverage, and species diversity index but also enhance the water retention capacity of soil and vegetation and the ability of soil physicochemical properties. 3) The restoration method of covering soil + sowing shrub seeds + honeycomb chamber is the optimal restoration technique in this area. This technique improves vegetation coverage and water retention, having a significant positive effect on vegetation growth. [Conclusions] For future rehabilitation of coal gangue slopes in this area, it is advisable to focus on legumes and composites in plant selection and to adopt artificial restoration methods such as soil covering, grass seed broadcasting, and honeycomb cell matting. These techniques can substantially improve vegetation recovery and soil and water conservation in complex natural settings.
ZHOU Yining, ZHANG Zizheng, GUAN Yinghui, LIN Yicheng, ZHOU Jinxing, LIU Yuguo
Spatiotemporal variations and tradeoffs as well as synergies of ecosystem services in Xiaoluan River Basin
[Background] The interactions and spatiotemporal and characteristics of ecosystem services are crucial for maintaining human well-being and achieving regional sustainable development. [Methods] Based on InVEST model, the revised universal soil loss equation (RUSLE) and RDA analysis, this paper systematically evaluated four important ecosystem services in the Xiaoluan River Basin, and identified the trade-offs/synergies of ecosystem services and their driving factors. [Results] 1) Forest land and grassland had the highest habitat quality, with forest land showing significant advantages in soil conservation and water retention services, while cultivated land having a strong capacity for water purification services. 2) From 2000 to 2020, the habitat quality, water retention and water purification in the Xiaoluan River Basin showed an increasing trend, and the relationship between soil conservation and water purification services changed from a synergistic relationship to a tradeoff relationship, while the relationship between soil conservation and water purification services showed a gradually enhanced synergistic relationship. 3) Ecosystem services are influenced by multiple factors. Precipitation, NDVI and forest land proportion have positive effects on water retention, soil conservation and habitat quality services, but negative effects on water purification services. [Conclusions] The Xiaoluan River Basin should comprehensively consider the situation of ecosystem services and economic development, and continuously adjust the land use planning according to the actual situation. The results provide scientific guidance for formulating reasonable ecosystem management measures locally.
LI Xiaoyan, LI Zhiguang, CHENG Hui, WU Juan, LU Shunfa, XIE Jinsheng, ZHONG Xiaojian
Carbon credit accounting method and application in soil and water conservation projects: A case study of comprehensive treatment in the Luodihe watershed
[Background] Promoting the construction of carbon credit assessment methods for soil and water conservation carbon sink projects is an important means to achieve China's carbon neutrality goal, but there is no study on the methodology for the evaluation of soil and water conservation carbon credit benefits. Soil and water conservation management in the Luodihe small watershed in Changting county is a typical comprehensive watershed management project, and the exploration of its carbon credit benefit is typical, which can provide some theoretical reference and technical support for the evaluation of carbon credit benefit in other related areas. [Methods] The carbon sink measurement method under the baseline and project scenarios was used to calculate the carbon sink benefits of the Luodihe Small Watershed Comprehensive Management Project, and the carbon credit accounting method of the soil and water conservation carbon sink project considering the carbon sink benefits, biodiversity measurement and community development benefits was proposed through participatory village assessment, field visits, literature surveys and other methods, and the carbon credit benefits of the comprehensive management of the Luodihe small Basin were analyzed by using this method. [Results] 1) It was found that after 20 years of comprehensive treatment, the carbon sink benefit of the Luodihe small watershed was 30 571.05 t, with an average annual value of 1 455.76 t/a, and the carbon sink benefit of the comprehensive management of soil and water conservation was significant.2) The assessment system of biodiversity and community development benefits of small watersheds was constructed, and the results of biodiversity assessment showed that the comprehensive management project of the small watershed of the Luodihe was a category I project, and its biodiversity was greatly improved. The results of community development benefit evaluation show that the community benefit of the Luodihe small watershed comprehensive management project is significant, and it is also a class I project. 3) The carbon credit benefit and carbon sink benefit of the small watershed of the Luodi River were consistent, which was 30 571.05 t, with an average annual value of 1 455.76 t/a. The carbon credits of the integrated management of the Luodihe small watershed effectively reflect the multiple benefits of comprehensive management activities, such as carbon sequestration, emission reduction, sink increase, diversity restoration, and poverty eradication. [Conclusions] This study constructs a carbon credit accounting method for soil and water conservation projects, which provides a methodology for soil and water conservation carbon credit accounting in the small watershed of Luodihe, and also provides a certain reference for carbon credit accounting for related projects, which is conducive to promoting the value realization and transformation of soil and water conservation carbon sink ecological products.
TANG Yuxiao, LIU Wen, LIU Xueyan, WEI Shaowei, LIU Teng
Mechanical properties analysis of palm fiber reinforced quartz sand
[Background] Sandy soil is more likely to cause soil erosion and stratum deformation because of its loose structure, easy liquefaction, easy erosion and other defects. In recent years, fiber reinforcement technology has been widely used in road and slope protection projects because of its ability to improve soil structure and enhance the mechanical properties of soil as a whole. However, when synthetic fibers are used as reinforcing materials to strengthen the soil, the characteristics of synthetic fibers, such as difficult to degrade and easy to cause environmental pollution, make it difficult to be widely promoted in actual projects. Therefore, this paper investigates the effect of mixing natural palm fiber into quartz sand to simulate the effect of plant fiber reinforcement technology on sandy soil, which is of great significance for analyzing the soil and water conservation effect of plant fiber reinforcement technology. [Methods] Triaxial drained compression tests were carried out on saturated palm fiber reinforced quartz sand. The deviator-strain curve, stress path and volume change under different reinforcement conditions were obtained. According to the test results, the coefficient of enhanced strength of fiber reinforced sand, shear strength and void ratio of the compressed sample were analyzed with the fiber content and fiber length. [Results] 1) The peak deviator stress and residual strength of the reinforced sand sample are higher than that of plain sand samples. The maximum coefficient of enhanced strength is 1.39, while the maximum residual strength of the fiber reinforced sand can reach 2.2 times of plain sand. The fiber mainly strengthens the residual strength of the quartz sand. Therefore, the strain softening behavior of pure sand changes into strain hardening performance of fiber reinforced sand, which has more ability to resist the deformation. 2) It shows that the shear strength of sand samples generally increases with the fiber content, as well as generally increases with fiber length. The shear strength is the highest when the fiber length is 20 mm and the fiber content is 0.9%. 3) The volumes of fiber reinforced sand have a similar trend as the pure sand, but they can reach higher values and keep increasing rather than converging at a stable value. Compared with pure sand, the axial strain of fiber reinforced sand changes greatly when reaching the critical porosity, and the dilatancy rate of the specimen reduces, which proves that palm fibers help sand samples enhance the ability to resist greater strains. [Conclusions] The interfacial stress between palm fiber and quartz sand particles improves the mechanical properties of quartz sand, and the results provide a test basis for the application of plant fiber reinforcement technology in sand fixing engineering.
PU Jian, LIU Renyu, WANG Zhigang, ZHANG Tong, LI Jianming, SHEN Shengyu, XU Wensheng, LIU Jigen
Scene recognition for construction projects based on the combination detection of detailed ground objects
[Background] Construction projects belong to complex semantic scenes, and their automatic recognition is a technical challenge for dynamic monitoring of soil erosion and supervision of soil and water conservation. The construction projects in high-resolution remote sensing images lack a unified semantic concept definition, and their scenes contain a variety of artificial and natural features, with highly unstructured and significantly different image features inside the scenes. Therefore, it is necessary to study the target detection method for Construction projects. [Methods] We proposed a target detection method and theoretical system for complex semantic scenes of construction projects. GF-1 remote sensing image of 2 m resolution was used for annotation. Firstly, based on the construction projects data and its detailed ground object dataset for target detection, we selected high-information detailed ground objects for target detection according to the information content. Then, the Faster RCNN algorithm was used to detect construction projects and high-information detail ground objects separately, and the prediction result frame merging with detail ground objects combination correction was used to jointly increase the confidence of construction projects identification and optimize the detection results. [Results] Wuhan construction projects dataset is built, including construction project, bare land(rock), cover, construction road, prefabricated house, construction structure and built building, which amount is 752, 763, 154, 82, 372, 292, and 278, information content is 18.81, 20.96, 9.93, 44.82, 28.77, and 8.22, respectively. Comparing this method with three other methods under the same experimental conditions, including Faster RCNN, Yolo, and variation of this method. The experimental results show that the accuracy evaluation indexes of the method on the produced Wuhan construction projects dataset are better than other comparison methods, and its AP(average precision) value and F1 score reach 0.773 and 0.417, respectively. The AP values of the three other methods were 0.755,0.693 and 0.754, and the F1 scores were 0.415,0.361, and 0.405, respectively. Compared with the other three methods, all of them have a certain degree of improvement. This method can effectively reduce the rate of wrong detection and improve the coincidence of correct detection results. [Conclusions] Better recognition results for construction projects in complex semantic scenes can be gained by this method. By the application of this method we can accurately and effectively identify the construction project, and by comparing it with the water and soil conservation program that has been reported, it can determine whether the construction project is built before approval and disturbed beyond the approved boundary, so as to achieve full coverage supervision of the construction project.
LI Mingming, XU Guangzhi, YANG Kaicheng, DAI Fuqiang, ZHOU Ping
Effects of ecological soil and water conservation measures on soil erosion control in China’s typical regions: A meta-analysis
[Background] As one of the most serious environmental issues in the world, soil erosion causes water pollution, reservoir siltation, soil productivity decline, thus threatens agricultural systems and even affects global climate. The benefits of ecological soil and water conservation measures (ESWCMs, such as micro basins tillage and contour tillage) are widely understood, including runoff and soil loss reducing to a certain extent when compared with traditional tillage. While few studies have focused on China’s different soil types and erosion characteristics. [Methods] We reviewed literature from Web of Science, Scopus, and China National Knowledge Infrastructure using terms like "Conservation practice" "Contour tillage" "Runoff" "Sediment" "Erosion" and "China" and retained literatures based on criteria such as natural or simulated precipitation, runoff or soil loss data, reported replications and statistics, recorded factors like location and slope, and at least two data pairs per group. Ultimately, 49 literatures were selected to quantify the impacts on different ESWCMs and identify the slope and precipitation for the greatest runoff and sediment reduction by calculating the log response ratio (LRR). [Results] The three regions’ soil and water conservation benefits varied due to the differences in climate, terrain, and soil properties: 1) ESWCMs applied in the black soil region of Northeast China were the most effective in reducing runoff and soil loss (66.65% runoff and 75.83% sediment), followed by those applied in the purple soil region of Southwest China (39.98% runoff and 58.30% sediment) and loess soil region of Northwest China (16.36% runoff and 32.44% sediment). 2) Micro basins tillage (MBT) (71.79% runoff and 87.03% sediment) no-tillage with mulch (NTM) (17.30% runoff and 32.51% sediment), collecting soil to form a ridge with no-till (CSNT) (55.78% runoff and 71.36% sediment reduction) were the most efficient soil and water conservation measures in controlling water erosion in the black soil of Northeast China, the loess soil region of Northwest China and the purple soil region of Southwest China, respectively. 3) The slope gradients ranged from 0-3°, >3°-5° and >10°-15° (0-3°: 97.09%; >3°-5°: 74.62%; and >10°-15°: 39.41%) caused the largest reduction of runoff in the black soil region of Northeast China, the loess soil region of Northwest China, and the purple soil region of Southwest China. Meanwhile, the effects of sediment reduction were the most obvious, ranging from 0-3°, >10°-15°, and >20°-25° (0-3°: 89.32%; >10°-15°: 75.94%; and >20°-25°: 67.25%). 4) The effect of ESWCMs under rainstorms was the most obvious in the black soil region of Northeast China. The effect on runoff reduction under light rain in the purple soil region of Southwest China was the most obvious, but it failed to pass the significance test in sediment reduction. [Conclusions] The results provided optimal conservation tillage measures for three regions, different slopes and different rainfalls, and provided data support for reducing regional soil and water loss in China.
Profile distribution of particle size of sediment at a check dam in small watershed in the Karst hilly region
[Background] The sediments is an important medium for retrieval of soil erosion characteristics, which indicates important information about the environmental process relation to soil erosion and deposition. [Methods] To investigate the characteristics and sources of sediment deposition in small watersheds of karst regions, the distribution characteristics of sediment particle profiles in small watersheds were analyzed and using field sediment stratification and sampling, indoor testing, and mathematical statistics. [Results] 1) The particle size composition of sediment in a check dam is mainly composed of clay and medium silt particles, which account for 68.64% of the total proportion on average and their coefficient of variation is the smallest. The order of other particle sizes according to the average proportion of the total proportion is silt (13.69 %), very fine sand(9.21%), fine silt (5.59%) fine sand(2.02%), coarse sand (0.82%) and large sand (0.05%); 2) The sediment particle size profile of check dam siltation can be divided into three levels: >0-30 cm with relatively uniform sediment particle size dominated by particles finer than fine silt, indicating land use transformation within the small watersheds; >30-60 cm with better sediment particle gradation where all types of particle sizes basically distributed including a small amount of coarse sand and very coarse sand; >60-85 cm with more uniformly distrbuted sediment partical size type compared with the previous layer, showing an increased proportion of coarse sand and large sand,which indicates the existence of rainstorm events in the control watersheds. 3) At the depth of 60 cm, the characteristic particle size parameters and fractal dimension values of check dam silt reaches their maximum values, which is the turning point of the profile. indicating that the hydrodynamic conditions in the control watersheds are changed. The distribution characteristics of sediment particles in a check dam are closely related to land use control and water-sediment transport in small watersheds. [Conclusions] The distribution and variation of sediment particle sizes at different levels can provide insights into changes in land use within the watershed, the intensity of rainfall events, and alterations in hydrodynamic conditions.
TAN Lu, ZHENG Yiling, ZHANG Qiang, ZHOU Lu, LIU Xia, YANG Yihui, ZHANG Xue, WANG Haiyang
Classification of small watershed based on ecology-production-living: Method and empirical study
[Background] With the aim to support coordinated development of ecology, production and living, which is the requirement of soil and water conservation in the New Era, it is necessary to classify the small watersheds into different categories and implement targeted guidance according to local conditions. Current studies on small watershed classification were mainly focusing on the differences of small watersheds in natural conditions and requirements for soil and water conservation, while the synergic relationship between ecological protection and development of production and living condition was not fully considered. [Methods] This paper proposed a small watershed classification system in consideration of both ecological conservation and development of production-living functions. Analytic hierarchy process and step-by-step judgment method were adopted to identify the category of small watershed according to a set of indicators that were selected through literature research. In order to validate the feasibility of the proposed small watershed classification system, an empirical study was conducted in Jiangsu province using data achieved from dynamic monitoring of regional soil and water loss, as well as data collected from public report on natural environment and social-economic development. [Results] 1) A two-level small watershed classification system was proposed. The first-level categories, namely high ecological sensitivity, medium ecological sensitivity and low ecological sensitivity were classified based on ecological security. The second level categories, namely industry agglomeration, green development, urban livable, beautiful village, landscape leisure and ecological conservation, were classified based on the dominant function in production and living. 2) With 14 indicators selected in consideration of ecology, production and living, a multi-criteria decision model of ecological sensitivity and a progressive decision model of dominant function in production and living were constructed respectively. 3) The proposed method was applied to classify the 3909 small watersheds in Jiangsu province as an empirical study. As for the first level classification, the category of low ecological sensitivity was the majority, accounting for 62.98%. As for the second level classification, categories of green development, ecological conservation and landscape leisure accounted for 23.92%, 23.10% and 20.13% respectively, followed by the categories of beautiful village and urban livable, accounting for 17.32% and 10.69%. The category of industry agglomeration was less, accounting for 4.83%. [Conclusions] The small watershed classification method based on ecology-production-living can comprehensively reflect the small watershed characteristics in terms of ecological protection and dominant production-living function. The proposed leading direction and priority of development for comprehensive management of each categories of small watershed could provide a scientific basis for the classified construction of small watersheds.
