Amannisa KUERBAN, Mansuer SHABITI, Aikedan YISAKE, Asiya AOBULITALIPU, Kunbike BAHETUERHAN
Spatiotemporal evolution of arable land use in Aksu River Basin, Xinjiang in recent 19 years
[Background] Regional agricultural development particularly food and economic crop yield depends on arable land entirely. So the change of arable land area affects the regional socio-economic development. This paper aimed to analyzing of the spatial-temporal change characteristics of arable land in Aksu River Basin for past 19 years.[Methods] Based on remote sensing and GIS technology, the spatial-temporal variation trend of arable land area in the study area was analyzed by using the remote sensing data of 2000, 2005, 2010, 2015 and 2018. Transfer matrix was used to analyze the transfer characteristics of arable land and other land use types in each period. Finally, using spatial Gini coefficient method, The degree of arable land fragmentation in Aksu River Basin was discussed.[Results] The results show that:1) The area of arable land in Aksu River Basin increased significantly from 2000 to 2018.Specifically, the arable land area was 5 553.4 km2 in 2000, accounting for 8.7% of the total area of the study area, and increased to 8 541.9 km2 in 2018, accounting for 13.4%, with an annual change rate of 2.99%.2) The characteristics of arable land transfer in the study area are obvious. The arable land area in Aksu River Basin was mainly transferred, and the transferred area was 4 666.38 km2, among which the transferred area and transferred area were 3 827.55 km2 and 838.83 km2 respectively.Grassland, woodland and unused land were mainly transformed into arable land, while grassland, woodland and construction land were mainly transformed out of arable land.In addition, during the study period, the area of arable land converted to construction land was 271.51 km2, and the area of construction land converted to arable land was 140.07 km2. 3) The degree of arable land fragmentation in the study area showed a fluctuating trend. From 2000 to 2010, the spatial Gini coefficient of arable land increased, and the degree of aggregation of arable land increased, and the degree of fragmentation intensified in 2015, and then gradually increased. However, in general, the spatial Gini coefficient of arable land in all periods of the study area was less than 0.04, indicating that the degree of fragmentation was high and the degree of aggregation was low.[Conclusions] With the increase of arable land area in the study area, Aksu River Basin in grassland, forest land, water area gradually reduce, arable land fragmentation degree is high, cause the land desertification, soil erosion and arable land security problems become more and more outstanding. This research may provide reference for promote the adjustment of industrial structure, effectively improve the ecological environment and agricultural production base.
SUN Kunjun, WANG Zhao, CHEN Shengjun, LONG Yihui, ZHANG Qingfeng
Rapid measurement of UAV height and viewport calibration
[Background] With the rapid development of civil small drone photogrammetry technology, a large amount of field work has been gradually shifted to internal work in the field of soil and water conservation monitoring.Inthis article,a simple and efficient area measurement method with certain accuracy was explored based on UVA photography, aiming to solve the time-consuming problem to obtain digital orthophoto (DOM) in production with a relatively large storage capacity.[Methods] A surface soil storage site in a soil and water conservation monitoring project on a highway in Guangxi province was selected as the experiment area, and the DJI Phantom 4 Pro drone was used to conduct surface observations at different altitudes. The relationship between the viewport area, the viewport length and the viewport width were quickly determined the scale of a single low-altitude aerial image, so as to achieve the purpose of quickly measuring the length and area of points of interest, eliminating the need to generate DOM.[Results] The UAV flying height had a strong correlation with the viewport area, viewport length, and viewport width. R2 was both 0.999, and the flight height was approximately equal to the viewport width.Using the regression equation formula and according to the law of the benchmark length and the height was approximately equal to the viewport width, the length information of the point of interest was calculated and the accuracy was verified. The accuracy of the 3 methods was:Benchmarking method (94.03%) >law of flying height=viewport width (93.97%) > formula method (92.18%), the data accuracy rate is >90%.[Conclusions] The method of using UAV to quickly measure the area proposed in this paper is of high feasibility. In actual operation, it reduces working time and data redundancy, and thus improves work efficiency. It is also provide a feasible method reference to calibrate the related parameters of UAV. The research results provide a reliable method reference for UAV photography technology in the field of soil and water conservation monitoring.
ZHANG Junjiao, HU Yang, SHI Changqing, ZHAO Tingning, WU Chuan, LIU Xiaoyong, LIU Bingru
Changes of vegetation and soil water, temperature and nutrient under different remediation modes in a dump
[Background] It is necessary to carry out vegetation restoration through manual intervention in open-pit coal mine dumps of arid areas, while vegetation, soil water, temperature and nutrient are important indicators to evaluate the effectiveness of restoration. Therefore, the changes of above indicators under different remediation modes are analyzed to provide reference for vegetation restoration in open-pit coal mine dump.[Methods] Five modes of ecological bag block (C-S), honeycomb lattice room full cover (C-F), vegetation blanket cover (J-C), vegetation blanket cover + ecological bag block (J-S) and vegetation blanket cover + honeycomb lattice room full cover (J-F) were set in Rujigou open-pit coal mine dump, CK was the plot with only grass seeds sowed without any renediation and vegetation, soil water, temperature and nutrient under above remediation modes were compared by one-way ANOVA analysis.[Results] 1) The vegetation coverage under CK, C-S, C-F, J-C, J-S and J-F were 0,0,0,10.00%,19.67%, and 16.33% respectively, and the vegetation coverage under J-S was significantly higher than that under other modes (P<0.05). Plant height was mainly related to plant species, and the height of Halogeton glomeratus, Agropyron desertorum and Lespedeza bicolor were nearly 20.0, 3.5 and 4.0 cm respectively. The growth of H. glomeratus and L. bicolor was good, while that growth of A. desertorum was poor. 2) During the observation period, the soil water content under C-S, C-F, J-C, J-S and J-F were 3.12%, 3.86%, 5.88%, 6.66% and 5.98% higher than that under CK, respectively. The average soil temperature under J-C, J-S and J-F decreased by 2.10, 2.68 and 1.95℃, and the daily soil temperature differences decreased significantly by 1.64, 1.37 and 1.54℃ (P<0.05). The changes of soil pH and organic matter content were slight under different modes, while the contents of soil hydrolyzable nitrogen and available phosphorus were significantly lower than those under CK (P<0.05). The soil total nitrogen content under J-C, J-S and J-F increased by 8.11%, 10.81% and 8.11%, and soil available potassium content increased by 54.22%, 38.36% and 64.97%.[Conclusions] There are differences in vegetation coverage, soil water, temperature and nutrient under different repair modes. The effectiveness of repair modes for vegetation restoration are not ideal, mainly related to poor water and nutrient condition of test dump. The change of vegetation coverage, soil water content, total nitrogen and available potassium content are significant under J-C, J-S and J-F, and the vegetation coverage under J-S increases the most among designed repair modes.
LI Song, SUN Xiangyang, LI Suyan, MA Qixue, ZHOU Wenjie
Effects of green waste compost on the seed germination of pakchoi cabbage under cadmium stress
[Background] Cadmium (Cd) is considered to be a highly toxic and non-biodegradable pollutant, which is easily absorbed by plant roots and transferred to other parts, and stored in leafy vegetables. Seed germination and seedling root development are important stages of plant growth cycle, while Cd significantly inhibits the seed germination and seedling growth of pakchoi cabbage. Green waste compost (GWC) was used as remediation material to alleviate the inhibition of Cd on the seed germination and seedling growth of pakchoi cabbage, so as to provide theoretical basis for preventing early damage of pakchoi cabbage by Cd and controlling Cd contaminated soil.[Methods] Pakchoi cabbage seeds were treated with different Cd2+ concentration solutions and GWC adsorption solutions (0, 5, 10, 25, 50, 100 and 200 mg/L). The characterization of GWC before and after adsorption of Cd2+ by GWC and its effect on the adsorption efficiency and adsorption capacity of Cd2+ were determined. The seed germination potential, germination rate, germination index and vigor index, root and shoot growth and root and shoot inhibition rate, Cd accumulation and transfer coefficient of pakchoi cabbage were determined.[Results] The SEM-EDS image analysis showed that Cd2+ was adsorbed on GWC. GWC had obvious adsorption effect on Cd2+ with different solubility, and the adsorption efficiency was 97.66%-98.91%. Cd stress reduced the germination potential, germination rate, germination index and vigor index of pakchoi cabbage seeds, and inhibited the growth of pakchoi cabbage seedlings. GWC treatment significantly alleviated the inhibition of Cd2+ stress on seed germination, and improved the germination index of pakchoi cabbage seeds under Cd2+ stress. The results showed that Cd had a "low promotion and high inhibition" effect on shoot growth. Compared with the control, the shoot length of pakchoi cabbage increased by 28% and 29% under 5 and 10 mg/L Cd2+ concentration treatments, but the root and shoot length inhibition rate increased significantly with the increase of Cd2+ concentration (P<0.05). After GWC treatment, the root length of pakchoi cabbage first increased and then decreased, and the root length inhibition rate was -6%-44%; it significantly promoted the shoot length growth of pakchoi cabbage (P<0.05), and the inhibition rate of shoot length was negative. The increase of Cd concentration in roots and shoots of pakchoi cabbage increased, but the translocation factor decreased. After GWC treatment, Cd content in roots and shoots of pakchoi cabbage decreased significantly, and the translocation factor ranged from 0.82 to 1.00.[Conclusions] In the important growth stages of seed germination and seedling root development, the GWC may substantially alleviate the inhibition of Cd2+ stress on the seed germination and seedling growth of pakchoi cabbage, reduce the accumulation of Cd, and prevent the early damage of Cd to pakchoi cabbage. It can available for reference to crop production activities and related basic research in heavy metal polluted farmland.
XIN Zhongbao, CAI Qiangguo, NING Duihu, LIU Baoyuan, YU Xinxiao, LEI Tingwu, ZHANG Keli, ZHANG Guanghui, FANG Haiyan, SUN Liying, HE Jijun
A new English term of ‘Yudiba dam’ and its differences from check dam
[Background] The ‘Yudiba’ is the Chinese Pinyin of an erosion control engineering measure, which has been widely implemented in the Chinese Loess Plateau and plays an important role in reducing sediment discharge and increasing cultivated land area. Although ‘check dam’ has been widely used as the English term to represent the engineering practice for erosion control and become the general English translation of ‘Yudiba’, the ‘check dam’ could not authentically highlight the soil and water conservation engineering of ‘Yudiba’ in the Loess Plateau.[Methods] Here the differences between the ‘Yudiba dam’ and the ‘check dam’ were specifically discussed in aspects of purposes, sizes and main functions. Moreover, the English translations for the ‘Yudiba’ were analyzed by comparing the connotations of the concepts, the different functions of the erosion control engineering in agricultural development and ecological improvement, as well as the simplicity when used in scientific studies.[Results] The ‘Yudiba’ is special soil and water conservation engineering measures, initiated from the Loess Plateau of China, referring to the dam structures built in various levels of gullies for the purpose of blocking sediment into cultivated land. The ‘check dam’ is a small temporary barrier, grade control structure or dam constructed across a swale, drainage ditch, or area of concentrated flow. The ‘check dam’ differed with the ‘Yudiba dam’ in purposes, sizes and main functions. Currently, various English translations were used in the literature, which were hardly accepted widely as either without representativeness or without simplicity.[Conclusions] We recommend the ‘Yudiba dam’ based on Chinese Pinyin as the formal English term in order to distinguish between the ‘Yudiba dam’ in the Loess Plateau and ‘check dam’ in other places. Thus, the ‘Yudiba dam’ is suggested to refer to the erosion control measure, which has been widely built in the Loess Plateau of China with the main functions including trapping sediment, reducing gully erosion and increasing the area of farmland in the sediment rich area.
YANG Jiaqi, GUO Jianbin, TANG Minghua, ZHOU Jinxing, WAN Long
Dynamic prediction model of soil moisture in rocky desertification region based on BP neural network optimized by genetic algorithm
[Background] Jianshui county of Yunnan province is a typical karst faulted basin landform, which is an important type area for the comprehensive control of karst rocky desertification in China. Because of the severe seasonal drought and rocky desertification, the barren water holding capacity of soil is poor and heterogeneity is high, and the prediction of soil water dynamic is difficult. It is of great significance for soil and water conservation and ecological restoration to reveal the process of soil water dynamic change and its influencing factors in this area.[Methods] Based on the daily meteorological data from April 16, 2006 to December 1, 2020 and soil moisture data from two different degrees of rocky desertification areas in Jianshui Karst rift basin of Yunnan province, a dynamic prediction model of soil moisture volume based on BP neural network was established for 0-10, 10-20 and 20-30 cm soil layers. Genetic algorithm was used to optimize the weights and thresholds of the model. The default factor method was used for sensitivity analysis to identify the main meteorological factors affecting the prediction of soil water dynamics in this area.[Results] The BP neural network model optimized by genetic algorithm was used to predict the soil volume moisture content of mild rocky desertification area and moderate rocky desertification area from September 13, 2019 to December1, 2020. The results showed that the predicted value of the model was close to the measured value. YMARE increased by 45% and 63%, YRMSE by 3% and 12%, R2 by 27% and 17%, respectively. The simulation accuracy of soil water in 20-30 cm depth was improved most obviously, The sensitivity analysis showed that the sensitivity index of soil moisture to rainfall was the highest (1.317-1.735), followed by the sensitivity index to average temperature (0.880 9-1.071 2), followed by atmospheric pressure and solar radiation.[Conclusions] The simulation result of genetic algorithm optimization was improved obviously. The results show that the BP neural network model optimized by genetic algorithm can be well applied to soil moisture simulation in rocky desertification area, and the simulation accuracy is significantly improved compared with the non-optimized model. It is proved that the prediction accuracy of soil water in moderate rocky desertification plot is higher than that in mild rocky desertification plot, and the prediction accuracy decreases with the increase of soil depth. Sensitivity analysis was used to determine that precipitation was the main meteorological factor, followed by air temperature. The sensitivity analysis showed that the soil at 0-10 cm surface layer was the most sensitive to meteorological factors, while the soil at >10-20 cm middle layer was the most sensitive to meteorological factors.
WANG Shutao, SHI Mingchang, CHEN Chunyang, CHEN Jingtao
Spatial distribution of soil erosion in Hubei province based on deep learning
[Background] Regional soil erosion spatial distribution information plays an important role in ecological restoration and land use optimization decision-making, but the spatial model for its analysis and calculation is not yet mature. Deep learning method was introduced in order to establish the complex relationship between soil erosion and various factors and to obtain high-precision spatial distribution data of soil erosion intensity by using its strong computing ability and good fitting effect. The large area of coniferous forest cover in Hubei leads to serious soil erosion, which was taken as research area to verify the feasibility and efficiency of deep learning in regional soil erosion spatial distribution information acquisition.[Methods] This study introduced machine deep learning method to explore a new way to study the spatial distribution of soil erosion. The framework of UNet++ and BP neural network were constructed, and hyper-parameters were optimized on the Jupyter Notebook platform. Based on the real spatial distribution data of soil erosion in Hubei province, optimization function and loss function were used to train neurons to record the deep information of soil erosion factors. Spatial distribution data of factors were obtained by remote sensing as model input, pixel Windows were randomly extracted as training samples to calculate the spatial distribution data of soil erosion intensity grade.[Results] The results showed that the overall accuracy of the UNet++ neural network model was 95.7%, and that of the BP neural network model was 91.4%. The UNet ++ model achieved the better overall accuracy than BP neural network model. The results of BP neural network model had more "salt and pepper" phenomenon, while the results of UNet++ neural network model were difficult to find. UNet++ neural network model overcame the phenomenon of "pepper and salt" in BP model. The error distribution of UNet ++ model in each erosion intensity was relatively uniform, without obvious error aggregation phenomenon. Compared with the BP model, UNet ++ model better reflected the distribution of soil erosion.[Conclusions] It is proved that when rainfall erosivity, soil erodibility, land cover, vegetation cover, slope and topographic relief are selected as input factors, deep learning model can be used to automatically obtain spatial distribution data of soil erosion intensity accurately and quickly by computer. In addition, compared with the traditional BP neural network, the spatial distribution results of soil erosion intensity obtained by UNet++ model have higher accuracy and better effect.
HEI Jie, LI Xiande, LIU Jilong, WANG Yafei, XU Jiayi, YANG Xiang, YIN Xiaolei, WANG Weiqi, ZHANG Yongxun
Effects of crop rotation patterns on the soil aggregates and carbon and nitrogen content in farmland
[Background] Soil carbon (C) and nitrogen (N) content plays a key role in nutrient utilization and cycling of farmland crops. The carbon and nitrogen content and stability of soil aggregates are important indicators to characterize soil structure, degradation and stability. Ginger-rice rotation and ginger-vegetable rotation are different patterns of paddy and dry land rotation, which have different carbon and nitrogen protection mechanisms. This work aims to explore the distribution patterns, stability and variation characteristics of C and N content of farmland soil aggregates under different rotation patterns, and to select the optimal rotation pattern.[Methods] In this study, the farmland under the ginger-vegetable and ginger-rice rotation patterns was used as the research object of Tongling city, Anhui province, and soil samples with a depth of 0-20 cm were collected. The contents of soil aggregates with different particle sizes were measured, and the differences of soil aggregates and C and N contents were analyzed by ANOVA. The qualitative characteristics of soil aggregate stability were measured by the soil aggregate stability index mean weight diameter (MWD), geometric mean diameter (GMD), >0.25 mm diameter aggregate (DR0.25) and fractal dimension (D), and the relationship between soil aggregate, aggregate carbon and nitrogen and soil stability index was analyzed by Person correlation.[Results] 1) The content of >0.053-0.25 mm microaggregates in the ginger season under the ginger-vegetable rotation increased by 53% compared with that in the vegetable season (P<0.05). Under ginger-rice rotation, the content of microaggregates ≤ 0.053 mm in the ginger season was 39% lower than that in the rice season (P<0.05), while the content of large aggregates >0.25-1.00 mm was about twice higher than that in the rice season (P<0.05). 2) Compared with the ginger-rice rotation, the ginger-vegetable rotation significantly reduced the C and N content of ≤ 0.053 mm microaggregates in the ginger season by 32% and 33% (P<0.05), and the C and N content of the large aggregates >1.00 mm significantly reduced, respectively, in 39% and 33% (P<0.05). 3) Under the ginger-rice rotation, the contribution rate of ginger >1.00 mm large aggregate C was significantly higher than that of ginger-vegetable rotation by 24% (P<0.05), and the contribution rate of >0.25-1.00 mm large aggregate C and N was significantly lower than that of ginger-vegetable rotation 32% and 25% (P<0.05). 4) GMD and DR0.25 was significantly positively correlated with the content of >0.25-1.00 mm large aggregate (P<0.01). MWD was positively correlated with the content of >1.00 mm aggregates, respectively (P<0.01). MWD, GMD, and DR0.25 were all significantly positively correlated with the C and N of larger aggregates >0.25 mm (P<0.05).[Conclusions] Compared with the dry land rotation under the ginger-vegetable rotation, the ginger-rice rotation pattern under the paddy dry rotation can continuously improve the stability of soil aggregates and maintain the efficient utilization of soil C and N nutrients. It is the optimal rotation pattern to realize the coordinated utilization of soil and water conservation and nutrients in Tongling city, which is conducive to the sustainable production of white ginger.
Advance in studies on soil erosion using magnetic susceptibility technique
[Background] Soil erosion is a global environment issue resulting in reduction in the soil properties. Soil erosion not only decreases land productivity and crop yield, but affects eco-agricultural health. Magnetic susceptibility (MS) technique is a simple and rapid skill in high spatial-temporal resolution, which is suitable for several types of environmental carrier.[Methods] According to studies in last 70 years, this paper took two carriers (natural soils and artificial magnetic materials) and two types of measurement (qualitative description and quantitative evaluation) as the main line. The aim of this paper is to review the development of MS technique and provide an effective basis for the study of new soil erosion methods.[Results] 1) Researches of MS technology in soil erosion appeared later than in other fields. The research teams were relatively unitary, and the related results were distributed in pointed-source pattern. The available achievements mainly come from several regions or research teams, but it has not formed a mature research network in the world. However, the studies developed from a single region to the global, while the proportion of Chinese research continues to increase. 2) Based on the magnetic research of natural soil samples, artificial magnetic tracers provide a new carrier for the research under experimental conditions, which makes the soil magnetism in experimental scenes more adjustable and controllable. For the natural soil, the heterogeneity of magnetic susceptibility exists in the farmland slope affected by human tillage activities for a long time, and topography, tillage methods and management measures determine the law of soil migration on the slope. By taking advantage of the strong controllability and easy identification of artificial magnetic materials, the researchers used a variety of magnetic materials to simulate the transport process of soil particles, and specifically applied the magnetic susceptibility technology to simulation experiments at different spatial and temporal scales. 3) MS has been shown to be a reliable, economic and rapid method for tracking soil redistribution. However, the researches of MS technology in soil erosion are almost in exploring the qualitative patterns. Although it reached agreement of MS method in its principle and distribution in soil profile and zonal scale, but most existing results were based on empirical pattern. More case studies are necessary to verify the link between soil movement and magnetic susceptibility. Several studies on estimating soil loss using MS, such as mixing artificial magnetic particles into soil, estimating erosion depth according to soil magnetic indexes and relating MS to radioactive isotopes, is the key of current research.[Conclusions] No direct causal connection has been established between soil loss and magnetic susceptibility, and further quantitative research is needed to link magnetic susceptibility to soil redistribution. The amount of qualitative researches is more than that of quantitative researches, and it requires more quantitative expression to evaluate soil erosion process and mechanism.
Characteristics of soil organic carbon pool at different altitude gradients in eastern China and its influencing factors: A review
[Background] Soil is an important part of terrestrial ecosystem and the main storage and exchange pool in the process of global carbon cycle. The small changes of soil organic carbon will be further fed back into the global carbon balance and the maintenance of soil organic matter. Elevation is one of the important factors affecting the soil organic carbon pool, but there were many uncertainties in the related research, and there was still a lack of general understanding. The effect of carbon dynamics is of great significance on soil organic matter retention, soil aggregate structure stability, and soil and water conservation effects.[Methods] The authors mainly summarized the advances of soil organic carbon pool components and carbon mineralization characteristics at different altitude gradients in eastern China. When the literatures were searched, the keywords included "altitude", "soil organic carbon", etc. The literatures were related to the soil organic carbon pool at different altitudes and the reasons for its dynamic changes. Furthermore, main conclusions were summarized and relevant data were extracted for more in-depth analysis.[Results] The process of input and output of soil organic carbon had significantly impact on the soil organic carbon content. The differences in soil organic carbon content, organic carbon chemical composition, and soil organic carbon mineralization degree were all related to the change of altitude to a certain extent. Altitude gradient variation directly or indirectly caused the changes of soil types, soil enzymes, vegetation types, soil temperature, humidity and other environmental factors. Among them, the degree of fit between vegetation types, soil enzymes, temperature and soil organic carbon at different altitudes were relatively low, indicating the complexity of the interaction among them and soil organic carbon. Soil organic carbon was significantly related with soil water content (R2=0.409, P<0.01), soil microorganisms (R2=0.217, P<0.05), and soil type (R2=0.241, P<0.01).[Conclusions] 1) The content of soil organic carbon was positively correlated with the altitude (R2=0.174, P<0.01), and the differences in the chemical composition of organic carbon and the degree of mineralization of soil organic carbon were related to the change of altitude to a certain extent; Under the condition of altitude, the organic carbon content of the upper soil was higher than that of the lower soil. 2) The degree of soil organic carbon mineralization increases with the elevation. In different soil layers at the same altitude, the soil carbon mineralization rate decreases with the deepening of the soil layer. 3) Under different altitude conditions, soil water content, soil microorganisms, and soil types are the main factors affecting soil organic carbon pool.
