呼伦贝尔草原切沟形态发育特征与体积估算模型

呼伦贝尔草原是中国北方极其重要的生态屏障，过度放牧已导致该区域切沟不断形成和发育，加剧了草场退化和破碎化，但尚未见有关该区切沟侵蚀研究的报道。因此，该研究通过对呼伦贝尔草原核心区136.22 km²区域内所有切沟进行逐条野外实测，获取了切沟长度L、宽度TW、深度D、面积A、体积V、横断面积A_c、宽深比R_WD、长宽比R_LW等形态参数，研究了切沟形态特征及其体积估算模型。结果表明：切沟数量密度和沟壑密度G_D分别达1.15条/km²和0.27 km/km²，0.94‰的草场因沟蚀而消失。切沟整体表现为狭长、宽而浅形状，8个切沟形态参数的变化呈中、强度变异，平均L、TW、D、A、V、A_c、R_WD、R_LW分别为231.80 m、3.12 m、1.26 m、820.49 m²、1099.46 m³、3.39 m²、2.68、101.93，坡面沟和谷底沟的数量比为11:9，谷底沟8个形态参数是坡面沟的1.06～4.78倍。切沟TW、D、R_WD接近正态分布，L、A、V、A_c、R_LW呈偏左分布，这8个形态参数分别主要分布在1.0～4.0 m、0.5～1.2 m、1.0～3.5、0～200 m、100～600 m²、30～300 m³、0～3 m²、3.55～60范围，占比分别为77.9%、68%、77.9%、63.5%、56.4%、46.8%、57.7%、46.1%；沟蚀强度显著受地形影响，G_D和地表割裂度G_LD随坡度先增大后减小，9°时沟蚀最严重，阳坡和半阳坡G_D、G_LD分别是阴坡和半阴坡的4.3倍、3.7倍；V-A幂函数关系预测切沟体积优于V-L幂函数关系，建议作为呼伦贝尔草原切沟体积估算模型。研究可为呼伦贝尔草原沟蚀防治及草原可持续利用提供科学支撑。

Morphological characteristics and volume estimation model of the permeant gully in the Hulunbuir Grassland of China

Hulunbuir Grassland is one of the most important ecological barriers in northern China. However, overgrazing has led to the formation and development of gullies in recent years, leading to degrade and fragment the grassland. There are no studies on the gully erosion in this area. In this study, the field test was conducted on the gully erosion. An area of 136.22 km2 was selected from the Ewenki Autonomous Banner in the center of Hulunbuir Grassland. Eight morphological parameters were measured by laser rangefinders and GPS, including the gully length (L), width (TW), and depth (D) of each gully. The area (A), volume (V), cross-sectional area (A_c), width-to-depth ratio (R_WD), and length-to-width ratio (RLW) of the gully were then calculated by ArcGIS software. The gully morphology and distribution were determined to clarify the response of gully erosion intensity to landform change. The volume estimation model was constructed for the gully. The results showed that there was a strong variation in the gully morphology, with a wide range of the eight parameters. The average L, TW, D, A, V, A_c, R_WD, R_LW were 231.80 m, 3.12 m, 1.26 m, 820.49 m², 1099.46 m³, 3.39 m², 2.68, 101.93, respectively. The overall shape of the gully was narrow and long, or wide and shallow. The number density and gully density were 1.15 No/km² and 0.27 km/km², respectively. Correspondingly, 0.94‰ of grassland was lost, due to the gully erosion. The gully TW, D, and RWD were close to the normal distribution. The gullies were distributed mainly in the range of 1.0-4.0 m, 0.5-1.2 m, and 1.0-3.5, respectively, which accounted for 77.9%, 68%, and 77.9% of the total number, respectively. However, the L, A, V, Ac, and RLW were distributed to the left of the frequency curve in a small range. The gullies were distributed in 0-200 m, 100-600 m², 30-300 m³, 0-3 m², and 3.55-60, which accounted for 63.5%, 56.4%, 46.8%, 57.7%, and 46.1%, respectively. The proportions of hillslope and valley-bottom gully were 55% and 45%, respectively. The development dimension of the valley-bottom gully was higher than that of the hillslope gully, and its L, TW, D, A, V, A_c, R_WD, R_LW was 1.06-4.78 times higher than those of hillslope gully, respectively. There was a significant effect of topography on the gully development. The gully density (G_D) and gully lacerative degree (G_LD) increased first and then decreased, as the slope increased. The most serious erosion was found when the slope degree was 9°. G_D and G_LD on the sunny and semi-sunny slopes were 4.3 and 3.7 times those of negative slopes and semi-negative slopes, respectively. There were significantly higher correlations of the V with L and A than the rest. Both V-A and V-L relationships were described by the power function. After comparison and justification with the coefficient of determination (R²), relative mean standard error (RMSE), and Nash-coefficient (Ens), the V-A relationship (V=0.0597A^1.389) was more accurate and effective in predicting the gully volume than V-L relationship. The V-A power function was also suitable for the hillslope and valley-bottom gully, indicating more higher accuracy of estimation. The findings can provide scientific support for the control of grassland degradation caused by gully erosion, particularly in the sustainable development of the regional economy, society, and environment in Hulunbuir grassland.