黄土高原小流域植被特征及其季节变化

植被作为影响水土流失的一个重要因子一直受到广泛关注 ,黄土高原的植被特征随季节发生很大的变化 ,从而对土壤侵蚀发生深刻影响。选择陕北安塞县大南沟小流域 ,于 1998年、1999年和 2 0 0 0年的 5～ 10月 ,每 2周1次对其植被盖度、植被高度和叶面积指数 (L AI)及其季节变化进行了测量和分析。在大南沟流域 ,一半以上的土地是农地 ,种植了玉米、糜子、谷子、马铃署、荞麦和大豆 ,其它土地利用方式有荒草地、休闲地、灌丛、林地和果园。对于农地 ,叶面积指数、作物高度和盖度随季节发生很大的变化 ,农地盖度在春天增长缓慢 ,一般在 8月份才达到其最大值 ;非农地的盖度从 4月份开始增长 ,一般 6～ 7月达到其最大值 ,并保持至 9月甚至 10月份。年降雨总量对植被有很大的影响 ,而单场大降雨对植被特征也有很大的影响

Crop Characteristics and Their Temporal Change on Loess Plateau of China

Plant canopy, one of most important factor influencing soil and water conservation, has been studied for a long time. Crop characteristics, with great seasonal changes through the year, influence the soil loss significantly. The purpose of this study is to measure and analyse the plant characteristics and their seasonal change in the Loess Plateau. A small watershed, Danangou in the Loess Plateau of north China, was selected for this study. Crop characteristics including plant cover, plant height and leaf area index (LAI) had been measured every two weeks in 1998,1999 and 2000. In Danangou watershed, half of the lands are used as cropland for maize, foxtail millet, pearl millet, potato, buckwheat and soybean, and the others are wasteland, fallow, shrub, woodland and orchard.For cropland, LAI, height and cover changed greatly during the measurement season. The cover of cropland increased lately and slowly during the spring, and reached their highest values in August. For non cropland,cover increased from April, arrived the high value in May or June, and kept it to September even October. Annual precipitation has big influences for the crop characteristics. The individual rainfall event also has an important effect on plant characteristics. Because cropland consists of half of the watershed, landuse condition of the Danangou is not very good for soil and water conservation.