Application of spatial Markov chains to the analysis of the temporal–spatial evolution of soil erosion

2016 ◽  
Vol 74 (5) ◽  
pp. 1051-1059 ◽  
Author(s):  
Ruimin Liu ◽  
Cong Men ◽  
Xiujuan Wang ◽  
Fei Xu ◽  
Wenwen Yu
Keyword(s):  
Soil Erosion ◽  
Markov Chains ◽  
Water Conservation ◽  
Remote Sensing Data ◽  
Three Gorges Reservoir Area ◽  
The Three Gorges ◽  
Neighboring Region ◽  
Xiangxi River ◽  
Severe Erosion ◽  
Surrounding Areas

Soil and water conservation in the Three Gorges Reservoir Area of China is important, and soil erosion is a significant issue. In the present study, spatial Markov chains were applied to explore the impacts of the regional context on soil erosion in the Xiangxi River watershed, and Thematic Mapper remote sensing data from 1999 and 2007 were employed. The results indicated that the observed changes in soil erosion were closely related to the soil erosion levels of the surrounding areas. When neighboring regions were not considered, the probability that moderate erosion transformed into slight and severe erosion was 0.8330 and 0.0049, respectively. However, when neighboring regions that displayed intensive erosion were considered, the probabilities were 0.2454 and 0.7513, respectively. Moreover, the different levels of soil erosion in neighboring regions played different roles in soil erosion. If the erosion levels in the neighboring region were lower, the probability of a high erosion class transferring to a lower level was relatively high. In contrast, if erosion levels in the neighboring region were higher, the probability was lower. The results of the present study provide important information for the planning and implementation of soil conservation measures in the study area.

scholarly journals Ecological Construction Mode of Soil and Water Conservation in the Three Gorges Reservoir Area

2021 ◽  
Vol 272 ◽  
pp. 01007
Author(s):  
Xi He
Keyword(s):  
Soil Erosion ◽  
Water Conservation ◽  
Yangtze River ◽  
Three Gorges Reservoir ◽  
Three Gorges Reservoir Area ◽  
Three Gorges ◽  
Urbanization Process ◽  
Reservoir Area ◽  
The Three Gorges Reservoir ◽  
The Three Gorges

The Three Gorges Reservoir Area is an important ecological barrier and an important area of water conservation in China. Due to natural and man-made factors, the regional urbanization process is accompanied by soil erosion. In recent years, by actively implementing measures such as tree planting and afforestation, water and soil conservation projects, the forest coverage rate in the Chongqing Three Gorges Reservoir area has increased significantly, and soil erosion has been initially controlled. But the task of environmental protection in the Three Gorges Reservoir area is still arduous. This research analyzed the causes of soil erosion caused by the urban process, by collected and combed the data of soil erosion in the Three Gorges Reservoir area of Chongqing over the years. The causes of soil erosion in the Three Gorges Reservoir area caused by the urbanization process were deeply analyzed, we proposed to improve legislation and supervision; strengthen publicity and education of soil and water conservation; adopt new technology and technology and other governance countermeasures. The Three Gorges Reservoir is an important ecological barrier in the upper reaches of the Yangtze River. The control of soil erosion in the area has important ecological and social benefits for protecting the ecological environment of the Yangtze River Basin in China.

Benefit evaluation and annual change of soil and water conservation after converting farmland to forest in Lanlingxi watershed

2020 ◽  
Author(s):  
Zhilin Huang ◽  
Liang Ma ◽  
Tian Wang ◽  
Lixiong Zeng
Keyword(s):  
Soil Erosion ◽  
Total Phosphorus ◽  
Water Conservation ◽  
Nitrogen Loss ◽  
Arable Land ◽  
Soil Nutrient ◽  
Three Gorges Reservoir Area ◽  
Chinese Government ◽  
Soil Erosion Rate ◽  
Severe Erosion

<p>As the population has grown and human activities have intensified (predominantly agriculture) in the Three Gorges Reservoir area (TGRA) since the 1980s, the substantial areas of arable land on the steep slopes are the main living and farming space for people. Chinese government implemented the Conversion of Cropland to Forest Program from 2001, because of increasing erosion hazard by excessive cultivation and over-felling. To investigate the efficiency of a range of widely recommended program for soil conservation, long-term monitoring in the Heigou watershed was initiated from 2009. Surface runoff, sediment and nutrient transport were measured at watershed. Monitoring has been done to collect sufficient baseline data about soil erosion rate, runoff rate and quantity of soil nutrients (the sum of nutrients in sediment and runoff) in the watershed. The results showed that the soil erosion modulus varied from 138.26 to 355.28 t·km<sup>-2</sup>·a<sup>-1</sup> among between 2016 and 2019, while average soil erosion modulus was 265.8 t·km<sup>-2</sup>·a<sup>-1</sup>, lower than the allowable soil loss in this area. The average runoff coefficient, average loss load of total nitrogen and total phosphorus were 53.9%, 11.24 t·km<sup>-2</sup>·a<sup>-1</sup> and 0.19 t·km<sup>-2</sup>·a<sup>-1</sup>. Runoff contributed more than 90% of nitrogen loss, and sediment contributed 82.7% of total phosphorus loss. The soil erosion modulus decreased significantly from 2054.06 t·km<sup>-2</sup>·a<sup>-1</sup> to 265.8 t·km<sup>-2</sup>·a<sup>-1</sup> by returning farmland to forest, which was a severe erosion before. Loss load of soil nutrient diversion was high, and TN was excessive for surface water. The ratio of nitrogen to phosphorus would encourage algae growth and eutrophication in TGRA.</p>

scholarly journals Mechanized and Optimized Configuration Pattern of Crop-Mulberry Systems for Controlling Agricultural Non-Point Source Pollution on Sloping Farmland in the Three Gorges Reservoir Area, China

2020 ◽  
Vol 17 (10) ◽  
pp. 3599
Author(s):  
Shouqin Zhong ◽  
Zhen Han ◽  
Jiangwen Li ◽  
Deti Xie ◽  
Qingyuan Yang ◽  
...  
Keyword(s):  
Soil Erosion ◽  
Three Gorges Reservoir ◽  
Three Gorges Reservoir Area ◽  
Three Gorges ◽  
Point Source Pollution ◽  
The Three Gorges ◽  
Contour Hedgerow ◽  
Sloping Farmland ◽  
Contour Hedgerows ◽  
Non Point Source Pollution

High-intensity utilization of sloping farmland causes serious soil erosion and agricultural non-point source pollution (AGNSP) in the Three Gorges Reservoir Area (TGRA). Crop-mulberry systems are important agroforestry systems for controlling soil, water, and nutrient losses. However, there are many different mulberry hedgerow planting patterns in the TGRA. In this study, soil structure, nutrient buildup, and runoff nutrient loss were observed in field runoff plots with five configurations: P1 (two longitudinal mulberry hedgerows), P2 (two mulberry contour hedgerows), P3 (three mulberry contour hedgerows), P4 (mulberry hedgerow border), and P5 (mulberry hedgerow border and one mulberry contour hedgerow), as well as a control (CT; no mulberry hedgerows). P1 had the smallest percentage of aggregate destruction (18.8%) and largest mean weight diameter (4.48 mm). P5 led to the greatest accumulation of ammonium nitrogen (NH4+–N) and total phosphorus (TP) (13.4 kg ha−1 and 1444.5 kg ha−1 on average, respectively), while P4 led to the greatest accumulation of available phosphorus (AP), nitrate nitrogen (NO3−–N), and total nitrogen (TN) (114.0, 14.9, and 1694.1 kg ha−1, respectively). P5 was best at preventing soil erosion, with the smallest average annual runoff and sediment loss of 112.2 m3 ha−1 and 0.06 t ha−1, respectively, which were over 72.4% and 87.4% lower than those in CT, respectively. P5 and P4 intercepted the most N in runoff, with average NH4+–N, NO3−–N, particulate N, and TN losses of approximately 0.09, 0.07, 0.41, and 0.58 kg ha−1, respectively, which were 49.7%, 76.2%, 71.3%, and 69.9% lower than those in CT, respectively. P5 intercepted the most P in runoff, with average TP and total dissolved phosphorus (TDP) losses of 0.09 and 0.04 kg ha−1, respectively, which were 77.5% and 70.4% lower than those in CT, respectively. Therefore, the pattern with one mulberry hedgerow border and one mulberry contour hedgerow (P5) best controlled AGNSP, followed by that with only a mulberry hedgerow border (P4).

scholarly journals Temporal and Spatial Heterogeneity of Soil Erosion and a Quantitative Analysis of its Determinants in the Three Gorges Reservoir Area, China

2020 ◽  
Vol 17 (22) ◽  
pp. 8486
Author(s):  
Lin Chu ◽  
Tiancheng Sun ◽  
Tianwei Wang ◽  
Zhaoxia Li ◽  
Chongfa Cai
Keyword(s):  
Land Use ◽  
Soil Erosion ◽  
Spatial Heterogeneity ◽  
Soil Loss ◽  
Three Gorges Reservoir ◽  
Vegetation Coverage ◽  
Three Gorges Reservoir Area ◽  
Land Use Type ◽  
Three Gorges ◽  
The Three Gorges

As the most typical ecologically fragile area in South China, the Three Gorges Reservoir Area (TGRA) suffers from water and soil loss, which has threatened the local ecological environment. Understanding the spatial heterogeneity of soil erosion and exploring its determinants are of great significance in preventing soil erosion and maintaining ecological sustainability in the TGRA. This study investigates the spatial heterogeneity of soil erosion and quantitatively identifies the determinants in the TGRA based on the Chinese Soil Loss Equation (CSLE) and geographical detector method. This study concluded that the soil erosion status generally improved from 1990 to 2015, showing an increasing trend from 1990 to 2000 and a decreasing trend from 2000 to 2010. Slope, land use, and vegetation coverage were the dominant individual factors affecting soil erosion in the TGRA. For the interaction factor, the combinations of land-use type and slope and vegetation coverage and slope were the key determinants, explaining 68.7% and 63.1% of the spatial heterogeneity of soil erosion in the TGRA from 1990 to 2015, respectively. Moderate and higher levels of soil erosion occurred in areas where the slope was greater than 25°. Among the land-use types, dry land and bare land were prone to soil erosion. These findings reveal that land-use type and vegetation coverage should be considered for the effective prevention of soil erosion, and cultivation on sloped farmland should be prohibited, especially on slopes higher than 25° in the TGRA.

Soil erosion in the Three Gorges Reservoir area

Soil Research ◽  
2011 ◽  
Vol 49 (3) ◽  
pp. 212 ◽  
Author(s):  
Xibao Xu ◽  
Yan Tan ◽  
Guishan Yang ◽  
Hengpeng Li ◽  
Weizhong Su
Keyword(s):  
Soil Erosion ◽  
Three Gorges Reservoir ◽  
Storage Period ◽  
Three Gorges Reservoir Area ◽  
Three Gorges ◽  
Reservoir Area ◽  
Modis Ndvi ◽  
The Three Gorges Reservoir ◽  
The Three Gorges ◽  
The Impact

Spatial and temporal change in soil erosion in the Three Gorges Reservoir area since the water storage of the reservoir began filling to 135 m in 2003 is poorly understood. Using a modified soil erosion model, this study quantifies and analyses change in the extent and intensity of soil erosion in the region from 2000 to 2008. MODIS-NDVI remote sensing data (with 250 m spatial resolution) are used in the modelling and analysis of the study. The total amount, area, and intensity of soil erosion in the reservoir region presented a declining trend from 2000 to 2008. Yet there was an anomaly in the trend, in which extreme soil erosion occurred in 2003 and lasted until 2005. The average volume of soil erosion per year decreased by 4.10 × 106 t and the mean area of land experiencing soil erosion reduced by 1129.6 km2 from the pre-storage period (2000–02) to post-storage period II (2006–08). Land suffering soil erosion at high, very high, and severe levels mainly comprises forest and cropland on slopes with gradients ≥15° and is largely distributed in the eastern and south-western sections of the reservoir area. Land experiencing soil erosion at slight or moderate levels mainly involves cropland and forest on slopes with gradients ≥10° in the central section of the reservoir area. The impact of the Three Gorges Project on soil erosion since 2000 has been mainly mediated through three mechanisms: near-resettlement of rural and urban people; increased frequency and severity of geological hazards induced by rising storage of the reservoir; and implementation of ecological projects in the region. Through the former two mechanisms, soil erosion in the affected communities has been exacerbated, while the ongoing ecological projects appear to offset both the extent and intensity of soil erosion in the reservoir region. Other important factors influencing soil erosion include urban reconstruction and expansion, varying intensity of precipitation, and soil degradation.

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