Root Distribution and Soil Properties of Gully Heads and Their Effects on Headcut Migration in the Mollisols Region of Northeast China

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.

Soil Anti-Scourabilities of Four Typical Herbaceous Plants and Their Responses to Soil Properties, Root Traits and Slope Position in Northeast China

“…Our results found that planting grasses significantly improved soil physical structure and hence increased the resistance of soil erosion to runoff (Figure 4). Generally, the penetration of root systems can enhance soil porosity and infiltration capacity [5], which consequently increases the ANS of soil mass by altering the vertical migration of soil moisture and the lateral transport of surface runoff [39,51]. In this study, the soil ANS was positively related to soil TP with a power function (p < 0.05; Figure 6f).…”

“…Soil erosion is a global problem that severely threatens agricultural production and the ecological environment [1,2]. It has caused surface fragmentation, vegetation degradation and soil loss and altered the regional geographic environment by changing the migration and deposition patterns of soil particles [3][4][5]. Overland flow is the main driving force of soil erosion, and soil anti-scourability (ANS) is an effective index that indicates the ability of soil to resist scouring by runoff [6,7].…”

“…The root system, as a fundamental component of vegetation, can promote soil stability (e.g., soil aggregate stability, soil cohesion, and soil infiltration) by physical binding and chemical exudate-bonding effects [5,16,23,24] and hence enhance the soil resistance to erosion. Many studies have suggested that roots play a stronger role in preventing soil erosion than aboveground parts [25,26].…”

“…In addition, soil properties also play an important role in mitigating soil erosion, while the growth of roots typically improves soil structure [5,31]. Many studies have demonstrated that soil bulk density (BD) can increase soil resistance to detachment by flowing water by enhancing soil strength and soil cohesion [32].…”

“…The Mollisol region of Northeast China is essential for ensuring national food security [34,35]. Long-term intensive agricultural practices intensify soil erosion and seriously threaten the sustainability of local agricultural production and the ecological environment [5]. The major topographic features in the Chinese Mollisol region are characterized by long slope lengths and gentle slope gradients, which create topographic conditions for hillslope erosion by influencing soil water infiltration and runoff generation [36,37], and surface runoff is the main external erosive force of hillslope soil erosion in the Mollisol region [38].…”