降水变化对陕北黄土高原植被覆盖度和高度的影响

植被特性及生长模式是土壤侵蚀研究的重要因子，而降水是植被生长的主要限制因素。通过 3年的观测数据，分析了陕北黄土高原地区降水年际变化和年内变化对 6种植被覆盖度和高度的影响，得到如下主要结论：①年降水量对刺槐林、灌木林、荒草地和农地植被的影响较大，平水年份和干旱年份最大覆盖度相差约一倍。而对于植被高度来说，受影响最大的是休闲地和农地植被。②降水的年内分布，尤其是 6～8月份的降水量是限制植被覆盖度和高度的主要原因。对于荒草地、农耕地覆盖度和高度的影响尤为显著。农作物覆盖度、高度甚至每年播种日期和种类都受到生长季降雨量的制约。研究结果对于估计黄土高原地区植被参数的变化，以及对土壤侵蚀模拟和退耕还林还草都具有参考价值。

STUDY ON VEGETATIVE COVERAGE AND HEIGHT VARIATION IN NORTHERN LOESS PLATEAU

Vegetative growing patterns are important factors in soil erosion modeling. Vegetation growth is limited mainly by precipitation. Field measurements of three years were analyzed to study on the influence of interannual and seasonal change of precipitation on the coverage and height of six types of vegetation. The following results are derived: ①Silver chain, shrub, waste-land vegetation and crop of the six types under research are influenced remarkably by annual precipitation with the peak coverage in draught year is only half of that in medium precipitation year. As for vegetation height, fallow-land vegetation and crop are most influenced by annual precipitation. ②The distribution of precipitation in a year, especially the total rainfall from June to August, is a crucial factor for vegetation coverage and height. Present data show that it influences waste-land and cropland very obviously. And Crop canopy and height are determined by the total rainfall in the growth season. The results of this study are useful reference to estimating of vegetation parameters on the Loess Plateau and further to soil erosion modeling and the project of returning cropland to forest and grass.