植被覆盖度的时间变化及其防风蚀效应

VEGETATION COVER CHANGES OVER TIME AND ITS EFFECTS ON RESISTANCE TO WIND EROSION

在防治风蚀过程中过去人们只关注植被覆盖度的空间特性,但对其随时间变化的特性未引起足够的重 视。该文着重强调了植被覆盖度随时间变化的特性,并对不同类型植物覆盖度的动态变化特征进行了研究。通过 调查研究与理论分析,在土壤风蚀量与植被覆盖度及风蚀气候侵蚀因子三者之间建立了随时间变化的定量关系, 并利用该公式计算和比较了不同类型植物防风治沙性能的动态差异、总植被覆盖度及相应的总土壤风蚀量的动态 变化。结果表明在防风蚀的作用效应中灌木>多年生牧草>林木>作物>一年生牧草;总时空植被覆盖度与总土 壤风蚀量呈"反相位"的动态变化;风蚀季节总植被覆盖度较低,介于0.11-0.14之间,低于20％的临界覆盖度,这 也是该地区风蚀危害严重的一个重要原因所在。

Vegetation cover characteristics have both spatial and temporal components. In the past, researchers have paid particular attention to spatial characteristics of vegetation cover in protecting soil from wind erosion, but temporal changes in vegetation have been ignored. In this study, we examined both the spatial and temporal characteristics of vegetation cover. The monthly changes of different plant cover types were studied from June, 2002 to June, 2003 in Wuchuan County of the Inner Mongolia of China using sample thread and random step distance measures combined with photography to compare and correct possible errors. Quantitative relationships for vegetation cover types, the amount of wind erosion, and a wind erosion climatic factor were determined by field investigation and theoretical analysis. Using a wind erosion formula for different plant types, the total wind erosion was calculated. The results indicated that the effectiveness of different plant types in increasing soil resistance to wind erosion were: perennial shrubs > perennial pasture > forest > annual pasture > forage crops. The dynamic annual change in total vegetation cover was inversely related to the amount of soil wind erosion. The results indicate that low vegetation cover is one of the primary causes of serious soil wind erosion in this region. Planting annual pasture and forage crops instead of perennial pasture will result in a loss of protection from wind erosion and require more land reclamation efforts in the future. Our results also suggest that the current reclamation practice of converting wind eroded landscapes to woodlands is not ecologically sound and planting shrubs or perennial pastures offers greater protection to wind erosion, especially in the more arid and semi arid regions.