典型黑土小流域侵蚀强度时空变化特征——以海伦市光荣小流域为例

Spatiotemporal Variation of Soil Erosion Intensity in Mollisols of A Small Watershed-A Case Study of Guangrong Small Watershed

为了系统反映黑土区典型水蚀小流域土壤侵蚀特征,基于连续的Landsat TM/OLI影像计算NDVI,并基于优化后的土壤和土地利用参数,结合实地调查,利用中国土壤流失方程(CSLE)、基于单位流量加权侵蚀沉积模型(USPED)分别模拟了海伦市光荣小流域2000—2021年间平均土壤侵蚀模数和侵蚀沉积分布格局,并通过融雪侵蚀模型(SHI)模拟了2017年春季融雪侵蚀空间分布,综合分析了小流域的侵蚀格局成因。结果表明:2000—2021年间CSLE模拟发现,小流域平均土壤侵蚀模数为5.57 t/(hm^(2)·a),平均土壤流失量为0.55 mm/a,坡上侵蚀量较少[0~2 t/(hm^(2)·a)],为微度侵蚀,坡中处于极强烈侵蚀和剧烈侵蚀等级,侵蚀贡献主要来自坡度2°~6°区域,占总侵蚀量的79.56%;USPED模拟发现,小流域78.11%面积发生侵蚀或沉积,其中侵蚀面积占流域面积24.89%,平均侵蚀模数为9.40 t/(hm^(2)·a),且多集中在坡中和坡底侵蚀沟位置;沉积面积占流域面积的53.22%,平均沉积模数为-4.39 t/(hm^(2)·a)。受降雨的变化影响,2000—2021年间小流域平均侵蚀模数整体呈上升趋势,侵蚀性降雨集中发生在7,8月。SHI模型结果显示,小流域2017年春季平均融雪侵蚀模数为1.65 t/(hm^(2)·a),占该年总侵蚀量的32.07%,高于基于降雪量数据计算的融雪侵蚀模数。研究结果可为东北典型黑土小流域水土流失模拟和科学防控提供依据。

In order to systematically reflect the soil erosion characteristics of typical water erosion small watershed in Mollisols region,in this study,NDVI was calculated based on continuous Landsat TM/OLI images.Based on the optimized soil and land use parameters,combined with field surveys,the average soil erosion modulus and erosion deposition distribution pattern in the Guangrong Small Watershed of Helen City from 2000 to 2021 were simulated using the China Soil Loss Equation(CSLE)and the Unit Flow Weighted Erosion Deposition(USPED)model,respectively.Meanwhile,the spatial distribution of snowmelt erosion in spring 2017 was simulated by the snowmelt erosion model(SHI),and the causes of erosion patterns in the small watershed were comprehensively analyzed.The results showed that from 2000 to 2021,the CSLE simulation found that the average soil erosion modulus was 5.57 t/(hm^(2)·a),and the average soil loss was 0.55 mm/a.The erosion on slope was relatively small,belonging to slight erosion[0~2 t/(hm^(2)·a)].The middle of the slope was in the very strong erosion and strong erosion class,and the erosion contribution was mainly from the slope 2°~6°area,accounting for 79.56%of the total erosion amount.USPED simulation found that 78.11%of the small watershed area was eroded or deposited,of which the erosion area accounted for 24.89%of the watershed area,and the average erosion modulus was 9.40 t/(hm^(2)·a),and most of them concentrated in the erosion gullies at the middle and bottom of the slope.The deposition area accounted for 53.22%of the watershed area,and the average deposition modulus was-4.39 t/(hm^(2)·a).Affected by changes in rainfall,the average erosion modulus of small watershed showed an overall upward trend from 2000 to 2021,with erosive rainfall concentrated in July and August.The results of the SHI model showed that the average erosion modulus of the small watershed was 1.65 t/(hm^(2)·a)in the spring of 2017,accounting for 32.07%of the total erosion in that year,which was higher than the snowmelt erosion modulus calculated based on the snowfall data.The results of the study could provide a scientific basis for simulation and scientific prevention and control of soil erosion in typical Mollisols small watershed in Northeast China.