植被-侵蚀动力学模型参数的确定及在黄土高原的应用

植被-侵蚀动力学是研究流域植被与侵蚀在人类活动影响下演变规律的一门新的边缘学科。由植被-侵蚀动力学模型可绘制植被-侵蚀状态图,以预测停止人为干扰后植被及侵蚀变化趋势,评价水土保持措施成效,提出小流域优化治理方略。植被-侵蚀动力学模型4个参数a、c、b、f是流域重要特征参数,其值的确定是进行植被-侵蚀动力学模拟及绘制植被-侵蚀状态图的前提和基础。它们依赖于流域气候、土壤和地形地貌。本文以黄土高原典型小流域为例,采用试算法确定了它们的取值,通过相关分析发现参数a与P、T,参数c、b、f与D50、S之间存在明显的相关关系,并得到了相关关系式。将其用于吕二沟小流域植被-侵蚀动力学模拟,结果与实际情况符合较好。绘制了各参数的取值分布图。最后以燕儿沟小流域为例,将以上相关关系式用于植被-侵蚀状态图的绘制,及小流域自然状况、植被-侵蚀状态及水土保持效果的评价。

Vegetation-erosion dynamics model: parameter estimation and application in the Loess Plateau of China

Vegetation-erosion dynamics is a new interdisciplinary science that studies the laws of evolution of watershed vegetation and erosion under the action of various ecological stresses. A vegetation-erosion chart is derived from a vegetation-erosion dynamics model, with which the development trend of vegetation and erosion can be predicted, the effects of water and soil conservation measures can be evaluated, and the most effective management strategies can be selected. There are four parameters, a, c, b, and f, to be determined with data for the model. The vegetation-erosion chart for a watershed may be obtained if the four parameters are de- termined. The parameters depend on the climate, soil, and topography characteristics, but independent of human activities. The cor- relations between the parameters and the climatic, soil, and topographic characteristics of different small watersheds in the Loess Plateau of China are studied in this paper. First, the 4 parameters are calculated by iteration for each of 13 watersheds. Second, the correlation between the 4 parameters and suitable climatic (temperature, T, and precipitation, P), soil (median diameter, D50), and topographic (average slope, S) parameters are determined by correlation analyses and discussed for each parameter. Relations are found between parameter a and T and P, and between c, b, and f, and D50 and S. The calculated values of vegetation coverage and erosion in the Lv'ergou Watershed agree well with the measured values with the parameters in the model determined by the correla- tion relations. The distributions the parameters a, c, b, and f are derived using the correlation expressions. Finally, as a case study, the vegetation-erosion chart of the Yan'ergou Watershed is plotted to estimate the natural vegetation-erosion development and the effi- ciency of some water and soil conservation measures based on the parameters calculated using the correlation relations.