Critical slope gradient for compulsory abandonment of farmland on the hilly Loess Plateau

1998 ◽  
Vol 43 (5) ◽  
pp. 409-412 ◽  
Author(s):  
Keli Tang ◽  
Keli Zhang ◽  
Aling Lei
Keyword(s):  
Loess Plateau ◽  
Slope Gradient ◽  
Critical Slope ◽  
Hilly Loess Plateau ◽  
Critical Slope Gradient

Effects of Hydrological Processes on Surface and Subsurface Nitrogen Losses from Purple Soil Slopes

2021 ◽  
Author(s):  
Meixiang Xie ◽  
Pingcang Zhang ◽  
Yuanzhi Shi ◽  
Dalin Hong
Keyword(s):  
Ammonia Nitrogen ◽  
Surface Flow ◽  
Hydrological Processes ◽  
Purple Soil ◽  
Slope Gradient ◽  
N Loss ◽  
N Losses ◽  
Critical Slope ◽  
Study Laboratory ◽  
Critical Slope Gradient

Abstract Relationships of hydrological processes via surface flow (SF) and subsurface flow (SSF) to nitrogen (N) losses from sloping farmlands have been rarely researched. In this study, laboratory experiments were conducted to investigate ammonia nitrogen (NH4-N), nitrate nitrogen (NO3-N) and total nitrogen (TN) losses from purple sloped soils due to SF, SSF and sediment (S). Effects of rainfalls and slope gradients on N losses were also studied. Three rainfall intensities (0.4 ± 0.02, 1.0 ± 0.04 and 1.8 ± 0.11 mm min-1) and four slope gradients (5°, 10°, 15° and 20°) were designed in experiments. Larger SF discharges occurred with increasing rainfall intensities while SSF was prone to happen under low rainfall intensities. Although r2 of regression results were low, both N loss concentrations and loads coincided positively with discharges except for a negative relation between N concentrations and SF discharges. In comparison, smaller SSF discharges produced substantial N loads with higher N concentrations especially for NO3-N. NH4-N, NO3-N, and TN losses were dominated by S, SSF and SF, respectively. Furthermore, linear increases in loss loads with increasing discharges revealed that distributions of N loss loads were compatible with flow distributions in stormwater. 10° may be a critical slope gradient for SSF discharge and nutrient export.

scholarly journals Spatial heterogeneity of surface roughness on tilled loess slopes in erosion stages

2018 ◽  
Vol 13 (No. 2) ◽  
pp. 90-97
Author(s):  
Q. Zhang ◽  
J. Wang ◽  
F. Wu
Keyword(s):  
Surface Roughness ◽  
Spatial Heterogeneity ◽  
Loess Plateau ◽  
Chinese Loess Plateau ◽  
Strengthening Effect ◽  
Methodological Framework ◽  
Rill Erosion ◽  
Slope Gradient ◽  
Chinese Loess ◽  
Relief Effect

The main soil erosion areas of the Chinese Loess Plateau are tilled slopes. The knowledge of their spatial heterogeneity will contribute to the understanding of erosion mechanisms on a microtopographic scale. In this study, the spatial heterogeneity of four conventionally tilled slopes was examined under simulated rainfall conditions using a semivariogram-based methodological framework. Results show that all tilled slopes have a relatively stable spatial structure and the erosion stages of all tilled slopes have a similar spatial variability. The rainfall in the splash, sheet, and rill erosion stages has a degree of relief effect, strengthening effect, and relief effect on the surface roughness, respectively. However, the effects of tillage practices and slope gradient on the spatial heterogeneity are much larger than those of the rainfall. The spatial heterogeneity decreases with increasing slope gradient. The general autocorrelation scale of the tilled slopes is 3.15 m and their fractal dimension ranges from 1.59 to 1.85. The tilled slopes have certain anisotropy with respect to the slope direction from 10° to 22.5° while they show isotropy or weaker anisotropy in other directions. In this work, a semivariogram-based methodological framework was established for the spatial heterogeneity of microtopographic-scale slopes. The results also provide a theoretical foundation for future tillage measures on sloping fields of the Loess Plateau.

Exploring the interaction of surface roughness and slope gradient in controlling rates of soil loss from sloping farmland on the Loess Plateau of China

2019 ◽  
Vol 34 (2) ◽  
pp. 339-354
Author(s):  
Taotao Li ◽  
Longshan Zhao ◽  
Hongteng Duan ◽  
Yifan Yang ◽  
Yu Wang ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Loess Plateau ◽  
Soil Loss ◽  
Slope Gradient ◽  
The Loess Plateau ◽  
Sloping Farmland

Soil quality indices and their application in the hilly loess plateau region of China

Soil Research ◽  
2006 ◽  
Vol 44 (3) ◽  
pp. 245 ◽  
Author(s):  
Mingxiang Xu ◽  
Yunge Zhao ◽  
Guobin Liu ◽  
Robert M. Argent
Keyword(s):  
Soil Quality ◽  
Quality Indicators ◽  
Loess Plateau ◽  
Quality Index ◽  
Shaanxi Province ◽  
Soil Quality Indicators ◽  
Soil Quality Index ◽  
Plateau Region ◽  
Significant Difference ◽  
Hilly Loess Plateau

Soil quality in the hilly Loess Plateau region of China is seriously degraded due to hillside cultivation and severe soil erosion. No established methods are available for evaluating the regional soil quality nor has integrated soil quality assessment been conducted in the region. Our objectives were to (i) develop soil quality models and assessment methods, (ii) verify the representativeness of selected soil quality indicators, and (iii) evaluate landuse effects on regional soil quality. The research was conducted on 707 km2 of typical hilly Loess Plateau in Shaanxi province, China. Soil samples (total 208) were taken from 5 catchments under 10 different landuse types. Two integrated evaluation methods (weighted summation and weighted product) and 2 indicator sets (a whole and a minimum set) were tested, each producing a soil quality index. Quantitative evaluation of soil quality in different landuse types was also performed. The results showed that the weighted product method provided better differentiation of soil quality between landuses. The minimum indicator set of 8 soil quality indicators, selected by factor analysis from a complete set of 29 soil attributes, reflected all or most of the information of the whole set in assessing regional soil quality. Soil quality index (SQI) values under different landuse types ranged from 0.842 for natural woodland to 0.150 for orchard. Index values for orchard, cropland, revegetated grassland, and planted grassland were significantly less than those for 6 other landuse types, whereas planted shrubland, planted woodland, and natural grassland indices were significantly less than those for greenhouse, natural shrubland, and natural woodland. No significant difference in SQI was found between orchard, cropland, revegetated grassland, and planted grassland, or between planted shrubland and planted woodland. Overall, it was found that soil quality was generally poor across the region, except for natural woodland, shrubland and greenhouse areas.

scholarly journals Effects of vegetation cover and slope on soil erosion in the Eastern Chinese Loess Plateau under different rainfall regimes

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11226
Author(s):  
Congjian Sun ◽  
Huixin Hou ◽  
Wei Chen
Keyword(s):  
Soil Erosion ◽  
Loess Plateau ◽  
Water Conservation ◽  
Vegetation Cover ◽  
Interactive Effects ◽  
Chinese Loess Plateau ◽  
Slope Gradient ◽  
Chinese Loess ◽  
Sediment Yields ◽  
Erosion Processes

Soil erosion is a critical environmental problem of the Chinese Loess Plateau (CLP). The effects of vegetation cover on soil erosion reduction under different rainfall types are not well understood especially in the eastern Chinese Loess Plateau (ECLP). In this study, we monitored runoff and sediment yield at the Fengjiagou water and soil conservation station with five types of vegetation cover (arbor trees (ARC), shrubs (SHC), arable (ABC), natural vegetation (NVC), and artificial grass (APC)) and three slope gradients (10°, 15°, and 20°) in the ECLP. Based on long-term monitoring data, five rainfall types were classified by the maximum 30 min rainfall intensity (I30). We also quantitatively revealed the interactive effects of different types precipitation, vegetation cover and slope gradients on regional soil erosion. The results showed that (1) The RII (13 times) and RIII (eight times) type are the most threatening erosive rainfall in this region. (2) The ARC and SHC type were most beneficial for soil and water conservation in the ECLP; The APC and ABC are not conductive to the prevention of regional soil erosion. (3) Runoff and sediment yields increased with the slope gradient. The farmland is vulnerable to soil erosion when the slope gradient exceeds 10°. The results of this study can improve the understanding of regional soil erosion processes on the ECLP and provide useful information for managing regional water and land resources.

Automatic extraction of valley boundary from dems in the hilly Loess Plateau

2000 ◽  
Vol 10 (3) ◽  
pp. 238-244 ◽  
Author(s):  
Ya-dong Qian ◽  
Guo-nian Lu ◽  
Zhong-ming Chen
Keyword(s):  
Loess Plateau ◽  
Automatic Extraction ◽  
Hilly Loess Plateau
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