Abstract
Previous studies have proved that root distribution along gully headwalls greatly alters soil properties and further affects the soil erodibility of gully heads. However, it is not clear whether the gully headcut migration is affected by root distribution and soil properties. Five representative gullies developed in different land uses were selected to clarify the variations of root distribution and soil properties and their effects on headcut migration in the rainy season (May to October 2021) in the Mollisols region of northeast China. Results showed that the 68.4%–93.3% of root mass density and 65.6–88.5% of root length density were concentrated in 0–30 cm soil layer of gully heads, and the roots of <2.0 mm accounted for >85%. The gullies developed in farmlands had relatively higher soil compactness, shear strength and aggregate stability, but lower organic matter (OMC), disintegration capacity and soil permeability than those developed in woodlands, unpaved roads in farmland and stable gully-beds. Changes in soil properties of gully heads were closely related to root density. The linear, areal, and volumetric migration rate of gully heads varied greatly and were 1.07–35.11 m yr−1, 28.95–562.46 m2 yr−1 and 56.82–6626.37 m3 yr−1, respectively, with the average of 9.07 m yr−1, 156.92 m2 yr−1 and 1503.02 m3 yr−1, respectively. The change in headcut migration rate was significantly affected by root density, soil properties and drainage area, of which soil texture, OMC, soil aggregate structure, and the drainage area were the critical factors influencing headcut migration in the Mollisols region of northeast China.
Highlights
Introduction iationsLand degradation is one of the hot issues of concern of the international community, among which gully erosion is a relatively serious stage of soil erosion and an important embodiment of land degradation
Our result further showed that the soil bulk density (SBD) of gully heads negatively related to root biomass density (RBD) and root length density (RLD), but OMC, sand content, soil hydraulic conductivity (SHC), mean weight diameter (MWD) and geometric mean diameter (GMD) positively correlated to root density, which implied that the presence of roots can effectively enhance soil porosity structure, lower soil compactness, improve soil structural stability and soil permeability and increase organic matter content
We found that the stress strength (SS) and soil disintegration rate (SDR) had no statistical correlations with RBD and RLD, but they were significantly affected by SBD, OMC, and soil texture (Figure 6, p < 0.05), which was mainly because the effect of vegetation on soil properties was affected by various factors and the influence was a long-term process [53]
Summary
Land degradation is one of the hot issues of concern of the international community, among which gully erosion is a relatively serious stage of soil erosion and an important embodiment of land degradation. It has led to land fragmentation, land degradation and regional ecological deterioration, and even seriously threatens food strategic security [1,2]. Erosion has been a great ecological and environmental challenge in the world. Gully erosion has received a lot of attention in recent years [3,4,5,6], but it still lags splash erosion, sheet erosion and rill erosion. The study of gully erosion mechanism and its critical influencing factors and control measures should be the focus of future research.
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