Effects of vegetation structure and spatial arrangement on soil Erosion in loess plateau

Karst rocky desertification is a kind of serious land degradation. And it is the third-largest ecological and environmental problem compared with China northwest desertification and soil erosion in loess plateau. Besides, fractal geometry theory is mainly used to explore the regularity, hierarchy and scale invariance hide in complex natural phenomena. And it is a new research angle that the fractal geometry theory is applied to rocky desertification land degradation research. In this study, to explore the fractal characters of rocky desertification, we selected Pingguo County as a case study area. And the data sources include TM data in 2005 growth season, 1:100 thousand land use data, and 30-meter DEM data of ASTER. Above all, vegetation coverage, gradient and land use mode were selected as critical indications of rocky desertification. Subsequently, with the help of ENVI, ARCGIS, SPSS, etc., we have got the perimeter and area of the three types of polygons. And on the basis of above period results, fractal dimension and stability coefficient were obtained by linear regression analysis fit method. In conclusion, different karst rocky desertification landscape mosaic structures show different stability. Firstly, from the aspect of vegetation coverage, low vegetation coverage, no vegetation coverage, middle vegetation coverage and high vegetation coverage display an increasing sequence. Secondly, from the aspect of land use mode, it shows a decreasing trend in stability as wood land, dry hill, middle coverage grassland, plain dry land, dry mountain, water area, paddy hill, thin stocked land, (urban and rural, mining, residential areas), other thin stocked land, high coverage grassland, shrub land and paddy field. Finally, from the aspect of gradient, the landscape of 0°-15°, 15°-18°, 25°-30°, 22°-25°, 18°-22°, 30°-90° displays an increasing tendency in stability. Generally speaking, it is from a new angle that the fractal dimension and stability coefficient are put forward as a reflection of the characters of the rocky desertification land.

One of the core problems in soil erosion research is the estimation of soil erosion. It is a feasible method and technical approach to estimate soil erosion in Loess Plateau region by using USLE model, GIS and RS technology and using DEM data, meteorological data and land-use type data. With the support of GIS and RS technology, the USLE factors and soil erosion in Loess Plateau region were estimated, and the soil erosion intensity was classified according to the Chinese soil erosion intensity classification standard. The results can provide reference for the development of soil erosion control measures in the Loess Plateau.

Soil erosion is one of the key research topics in the world today, and it is a serious hazard to the natural environment and economic and social development. The researcher has found that soil erosion in China is regional, widespread and high-intensity. Of all the erosion areas, the Loess plateau is the most severe and the most representative. Therefore, this paper investigates the current situation of soil erosion in China and focuses on the erosion on the Loess Plateau, for its causes and remediation measures. Loess plateau has an inferior erosion-carrying capability, so the gully slopes and hilly areas of the Loess Plateau are prone to landslides and crumbling phenomena. Other erosion reasons include the fragmented high loess terrain with a lot of gorges and ravines, heavy rainfall, and low vegetation coverage. This study also proposes remediation measures by analyzing the different natural characteristics that cause soil erosion on the Loess Plateau. It is found that soil erosion control has a regional dimension and control measures should be closely related to the regional environment and the causes of soil erosion. Practice shows that the erosion control measures proposed in this paper greatly improve erosion in the Loess Plateau region, but the current state of soil erosion on the Loess plateau remains bleak.

The potential for using the radionuclide caesium-137 as an environmental tracer to indicate sources of soil erosion in the Chinese Loess Plateau is introduced. The caesium-137 contents of soil profiles have been used to estimate soil erosion losses from different topographic and land use conditions at Lishi, Shanxi Province, and Luochuan, Shaanxi Province. At uncultivated sites the caesium-137 has accumulated in the upper soil profile, whilst it has been mixed within the plough layer of cultivated soils. Eroded soils contain relatively less caesium-137, and simple calibration techniques are applied to quantify soil loss. Preliminary results suggest that caesium-137 may be of considerable value in assembling data on the rates and spatial distribution of soil loss and in identifying the source areas of eroded sediment.

Impacts of topography on sediment discharge in Loess Plateau, China

Objective The present study is to analyze the vegetation changes in areas with severe soil erosion on the Loess Plateau since the implementation of forestry ecological projects such as the Three-north (northwest, north and northeast) Shelterbelts and Conversion of Farmland to Forests, so as to provide basis for formulating reasonable ecological restoration and management countermeasures. Method Taking Ansai District of Yan’an City in Shaanxi Province as an example, the vegetation coverage in 2000 and 2017 was estimated by pixel dichotomy based on Landsat TM/OLI image, and topographic differentiation characteristics were analyzed in combination with altitude, slope and slope direction. Result (1)Vegetation coverage significantly increased from 24.98% in 2000 to 53.34% in 2017. (2)The proportion of vegetation coverage with extremely significant increase in the study area accounted for 44.70%, which was concentrated along rivers. (3)In 2000, the vegetation coverage gradually decreased with the increase of altitude. In 2017, the vegetation coverage increased first and then decreased with the increase of altitude. In 2000 and 2017, the vegetation coverage increased first and then decreased as the slope increased, and reached its maximum value at the slope of 25°−35°. The order of vegetation coverage from large to small with the change of slope direction was shady slope, semi shady slope, semi sunny slope, and sunny slope. (4)When the altitude was less than 1 300 m and the slope was 15°−35°, flat land, shady and semi shady slopes had good water and heat conditions, with easy vegetation recovery and the largest proportion of high vegetation coverage area. Conclusion The vegetation in Ansai District showed a trend of improvement from 2000 to 2017, with differences under terrain conditions such as altitude, slope, and slope aspects. Ecological restoration countermeasures should be formulated based on local conditions. [Ch, 2 fig. 6 tab. 27 ref.]

Developing an effective approach to rapidly assess the effects of restoration projects on soil erosion intensity and their extensive spatial and temporal dynamics is important for regional ecosystem management and the development of soil conservation strategies in the future. This study applied a model that was developed at the pixel scale using water soil erosion indicators (land use, vegetation coverage and slope) to assess the soil erosion intensity in the Loess Plateau, China. Landsat TM/ETM+ images in 2000, 2005 and 2010 were used to produce land use maps based on the object-oriented classification method. The MODIS product MOD13Q1 was adopted to derive the vegetation coverage maps. The slope gradient maps were calculated based on data from the digital elevation model. The area of water soil-eroded land was classified into six grades by integrating slope gradients, land use and vegetation coverage. Results show that the Grain-To-Green Project in the Loess Plateau worked based on the land use changes from 2000 to 2010 and enhanced vegetation restoration and ecological conservation. These projects effectively prevented soil erosion. During this period, lands with moderate, severe, more severe and extremely severe soil erosion intensities significantly decreased and changed into less severe levels, respectively. Lands with slight and light soil erosion intensities increased. However, the total soil-eroded area in the Loess Plateau was reduced. The contributions of the seven provinces to the total soil-eroded area in the Loess Plateau and the composition of the soil erosion intensity level in each province are different. Lands with severe, more severe and extremely severe soil erosion intensities are mainly distributed in Qinghai, Ningxia, Gansu and Inner Mongolia. These areas, although relatively small, must be prioritised and preferentially treated.

Model-based assessment soil loss by wind and water erosion in China's Loess Plateau: Dynamic change, conservation effectiveness, and strategies for sustainable restoration

As a geomorphic process persistently occurring over the earth’s surface, soil erosion is one of the most serious environmental problems in the world nowadays, seriously threatening agriculture, natural resources, and ecosystem environments. Monitoring surface deformation associated with soil erosion will help to understand the dynamics of erosion process and the erosion mechanism. In this article, an improved small baseline subset interferometric synthetic aperture radar (SBAS-InSAR) technique is proposed to monitor the surface deformation over the wind-water erosion crisscross region in the Loess Plateau, China. In particular, a new deformation model considering both of the internal factors and external factors of soil erosion is introduced into the SBAS-InASR algorithm. The results show that the cumulative deformation is close to −200 mm during the investigated period. The deformation rate caused by precipitation is between −0.03 and 0.02 mm/mm. When the wind erosion factor changes by 1 unit, the deformation range is approximately −0.3–0.2 mm. Also, researchers found that the surface deformation is highly correlated to precipitation and wind. The root mean square errors (RMSEs) of the residual deformations estimated from the proposed model are smaller than those estimated from the conventional linear and period models, demonstrating that the proposed method is more suitable to model and analyze the surface deformation in wind-water erosion crisscross region.

Various land degradation processes have led to land productivity reduction, food insecurity and ecosystem destruction. The Loess Plateau (LP) suffered from severe land degradation, such as vegetation degradation, soil erosion and desertification. This study assessed land degradation changes by considering different land degradation types including vegetation degradation, soil erosion, aridity, loss of soil organic carbon and desertification in the Huangfuchuan watershed of the northern LP. A comprehensive land degradation index (LDI) was developed by combining different degradation processes using the fuzzy logic modeling method. Our results showed significant land use transitions from bare land and sandy area to grass land and forest land from 1990 to 2018, which were consistent with an obvious increase in vegetation cover from 31.24% to 40.72%. The soil erosion rate predicted by the RUSLE model decreased by 51.95% during 1990–2018. The basin-average LDI decreased from 0.68 in 1990 to 0.51 in 2018, suggesting the great success of land degradation prevention in a fragile ecological environment region on the LP during the past decades. This study proposed an integrated framework for land degradation assessment in the high erodible area. The results can provide good references for the improvement of ecological environment in the future.

Threshold effects of vegetation coverage on runoff and soil loss in the Loess Plateau of China: A meta-analysis

Soil erosion is a major threat to our terrestrial ecosystems and an important global environmental problem. The Loess Plateau in China is one of the regions that suffered more severe soil erosion and undergoing climate warming and drying in the past decades. The vegetation restoration named Grain-to-Green Program has now been operating for more than 10 years. It is necessary to assess the variation of soil erosion and the response of precipitation and vegetation restoration to soil erosion on the Loess Plateau. In the study, the Revised Universal Soil Loss Equation (RUSLE) was applied to evaluate annual soil loss caused by water erosion. The results showed as follows. The soil erosion on the Loess Plateau between 2000 and 2010 averaged for 15.2 t hm−2 a−1 and was characterized as light for the value less than 25 t hm−2 a−1. The severe soil erosion higher than 25 t hm−2 a−1 was mainly distributed in the gully and hilly regions in the central, southwestern, and some scattered areas of earth-rocky mountainous areas on the Loess Plateau. The soil erosion on the Loess Plateau showed a deceasing trend in recent decade and reduced more at rates more than 1 t hm−2 a−1 in the areas suffering severe soil loss. Benefited from the improved vegetation cover and ecological construction, the soil erosion on the Loess Plateau was significantly declined, especially in the east of Yulin, most parts of Yan’an prefectures in Shaanxi Province, and the west of Luliang and Linfen prefectures in Shanxi Province in the hilly and gully regions. The variation of vegetation cover responding to soil erosion in these areas showed the relatively higher contribution than the precipitation. However, most areas in Qingyang and Dingxi prefectures in Gansu Province and Guyuan in Ningxia Hui Autonomous Region were predominantly related to precipitation.

Near soil surface characteristics change significantly with vegetation restoration, and thus, restoration strategies likely affect soil erodibility. However, few studies have been conducted to quantify the effects of vegetation restoration strategies on soil erodibility in regions experiencing rapid vegetation restoration. This study was conducted to evaluate the effects of vegetation restoration strategies on soil erodibility, reflected by soil cohesion (Coh), penetration resistance (PR), saturated conductivity (Ks), number of drop impacts (NDI), mean weight diameter of soil aggregates (MWD), and soil erodibility K factor on the Loess Plateau. One slope farmland and five 25‐year‐restored lands covered by old world bluestem, korshinsk peashrub, shrub sophora, sea‐buckthorn, and black locust were selected as test sites. The old world bluestem was restored via natural succession, while the other four lands were restored by artificial planting. A comprehensive soil erodibility index (CSEI) was produced by a weighted summation method to quantify the effects of vegetation restoration strategies on soil erodibility completely. The results showed that Coh, Ks, NDI, and MWD of the five restored lands were greater than those of the slope farmland. However, the PR and K of the five restored lands were less than those of the slope farmland. CSEI varied greatly under different restoration strategies, from 1 to 0.214. Compared with the control, these indices decreased on average by 68.2%, 78.6%, 72.7%, 75.8%, and 62.8% for old world bluestem, korshinsk peashrub, shrub sophora, sea‐buckthorn, and black locust, respectively. The variation in soil erodibility was significantly influenced by biological crust thickness, bulk density, organic matter content, plant litter density, and root mass density. Shrub‐lands via artificial planting, especially korshinsk peashrub, were considered the most effective restoration strategies to reduce soil erodibility on the Loess Plateau. The results are helpful for selecting vegetation restoration strategies and asking their benefits in controlling soil erosion. © 2018 John Wiley & Sons, Ltd.

Global changes have led to significant changes in soil erosion on the Loess Plateau. Soil erosion leads to the degradation of land resources and a decline in soil fertility, adversely affecting agricultural production and the socioeconomic situation. Therefore, revealing the spatiotemporal evolution patterns of soil erosion in the Loess Plateau region and investigating the influencing factors that contribute to soil erosion are crucial for its management and restoration. In this study, the RUSLE monthly model and the Geodetector model were utilized to reveal the spatiotemporal trends of soil erosion in the Loess Plateau from 2000 to 2020 and to determine the dominant influencing factors in different periods. The main results are as follows: (1) From 2000 to 2020, the soil erosion in the Loess Plateau initially weakened and then intensified, indicating that precipitation and precipitation intensity have different effects on surface soil. (2) From 2000 to 2015, the area experiencing slight and mild erosion increased. This is attributed to the increase in vegetation coverage in the Loess Plateau region, which has alleviated soil erosion in the area. (3) From 2000 to 2020, zones of severe soil erosion were mainly located in the cities of Yan’an and Yulin and their surrounding areas. The gravity center of soil erosion shifted northwestward from Yan’an City overall, indicating an improvement in the soil erosion conditions in the Yan’an area. (4) The predominant level of soil erosion across different land-use types was slight erosion, accounting for over 40%. This may be a result of forestry ecological projects that effectively reduce soil loss. (5) In slope zones of 0–5°, slight erosion accounted for the largest area proportion. As the slope increased, the area proportion of severe and extremely severe erosion also increased. This is attributed to the protective role of vegetation on soil in gentle slope areas. (6) From 2000 to 2020, vegetation was the dominant single factor influencing the spatiotemporal changes in soil erosion, while the interactions between vegetation and land use had the largest explanatory power, indicating that changes in land-use types partially affect variations in vegetation coverage. Our research findings could provide important data support for soil erosion control and eco-environment restoration in the Loess Plateau region.

Modeling vegetation coverage and soil erosion in the Loess Plateau Area of China