青海省“三江源”地区植被退化原因及其保护策略

Vegetation degradation and protection strategy in the "Three rivers fountainhead"area in the Qinghai province

对治多县32年的降水和气温变化资料的分析表明,自20世纪90年代以来,由于出现了较明显的增温减水现象,大气干旱加重,空气中相对湿度呈明显的波动减少趋势,因而造成了该地区的气候干旱化,不利于该地区草地生态系统生产力的提高和维持。同时,由于人口和家畜数量的增加,每个羊单位占有可利用草地从1953年的2.3hm2降低到1994年的1.1hm2,使牧压成倍增加。与60年代相比,平均产草量降低了50%以上,而有毒有害类杂草增加了20%～30%。到目前为止,约有1/3以上的草地处于不同程度的退化状态,约有1万hm2的天然草地已经荒漠化或沙化,主要分布在水边、河岸附近、滩地、坡麓和居民点周围即冬季牧场,是局部的退化;但夏季牧场牧压较小,牧草利用率较低,因而保持相对良好状态。由此可见,草地退化的主要原因是超载过牧。但气候的干旱化给过牧对草地的影响起到了推波助澜的作用,其叠加效应加速了草地的退化沙化。同时,由于气候的干旱化可能导致高寒草甸面积的缩小,使高寒草原及荒漠草原的面积有扩大的趋势,从而导致该地区草地总生产力的下降。

The Zhiduo County is so-called the 'first county' of the 'Three rivers fountainhead' area in Qinghai province. Looking at 32 years of climate data, investigation found trends of annual mean temperature increase and rainfall decrease since 1990. During this time, due to increase in population and numbers of livestock, utilizable grassland per sheep decreased from 2.3 hm^2/sheep in 1953 to 1.1 hm^2/sheep in 1994. Due to grazing pressure doubling, the average aboveground biomass was only 50% compared to 1953. About 33% of the total rangeland area is now degraded to varying degrees, and about 10 000 hm^2 of natural grassland has already become desertified or sandified, particularly along rivers, water sources, and villages. With examination of the places and occurrence times of vegetation degradation, the main reason seems to be overgrazing. Of course, there may be interaction between overgrazing and climate change. The trend of increasing aridity could result in decrease of alpine meadow area and increased alpine and desert rangeland area, which would result in grazing capacity decline. Therefore, the suggestion of immigration should be considered by local government with the construction of a national nature reserve in the region. However, the construction and management of this reserve should be open before the local people, and they should be encouraged to take part in the related activities. The conservation area should become multifunctional in combining conservation, development, research, and education including training, so that both ecological and economic benefits are obtained.