青海省天然草地退化及其环境影响分析

根据青海省"三江源地区"和"环青海湖地区"典型生态区域1987-2004年代表性牧草观测站植被监测资料和地面气象数据,结合NOAA/AVHRR卫星遥感数据以及调查数据,分析了两区域十几年来草地退化特征.结果表明:中度以上退化草地面积平均以20×104hm2.a-1的速度递增,草地生产力<750 kg.hm-2的草地面积占全省面积的26.99%.三江源地区牧草产量以4.48～16.48 kg.a-1趋势减少,高度以0.16～0.80 cm.a-1的趋势降低,优势牧草株数的线性递减率分别为11株.a-1和16株.a-1,莎草科牧草开花期和籽粒成熟期的发育百分率下降25～50个百分点;环青海湖地区牧草产量以3.05～4.64 kg.a-1趋势减少,高度以0.75～1.28 cm.a-1趋势降低,以禾本科牧草为代表的优良牧草在群落中的比重分别下降了1%～3%,位于青海湖以南地区的温性草原类和温性荒漠类,递减率分别为0.25%.a-1和0.38%.a-1.青海省天然草地退化主要是在自然和人为因素等作用下发生的,在自然因素中气候的暖干化趋势是草地退化的重要因素,表现在影响牧草的生育期、产量以及草地的群体结构的变化,而20世纪90年代以来极端天气、气候灾害的增多,进一步加剧了草地的退化;人为控制因素中,表现在草畜季节不平衡造成的超载过牧、人口增长以及草地不均匀的放牧压力等,进一步加剧天然草地生态功能的退化.

Natural Grasslands Degradation and Environmental Driving Factors in Qinghai Province

The Three River Sources areas and the regions around Qinghai Lake are the two important ecosystems in Qinghai Province.Based on the typical vegetation monitoring data and surface meteorological data from 1987 to 2004,combining with the remote sensing data of satellite NOAA/AVHRR and investigated data,the main degenerative characteristics of natural grasslands are analyzed.The main characteristics are: degenerative pasturelands area with moderate severity increasing with a speed of 200,000 square kilometers per annum in average;the area with productivity less than 750 kilogram per square kilometer accounting for 26.99% of the total area of the province.Output and height of grass in the Three River Sources areas decrease with the tendencies of 4.48 to 16.48 kilogram per annum and 0.16 to 0.80 centimeter per annum.The linear descending rate of dominant plant numbers are 11 and 16 plants per annum,respectively. The growth percentage of Cyperaceae kind's pasture in anthesis and seed autumn period decreases 25% to 50%.Pasture output and height in the regions around Qinghai Lake decrease with a speed of 3.05 to 4.64 kilogram per annum and 0.75 to 1.28 centimeter per annum;the proportion of Poaceae as an eminent representative kind decreases 1% to 3%.The descending rate of temperate steppe and temperate desert,which lie in south of the Qinghai Lake,are 0.25% and 0.38% per annum,respectively.According to the above mentioned,the degeneration of pasture in Qinghai Province might attribute mainly to environmental controlling mechanisms of nature and human activity.In this paper,the grassland degenerative mechanism and eco-process degeneration are analyzed.On one hand,among all the natural controlling factors,the tendency of drying and warming is the first important factor for the degeneration.It affects the growing season,pasture output and the community structure of pasture.Besides,pasture degeneration is aggravated owing to the increase of various extreme weather phenomena and climatic disasters since the 1990s;on the other hand,human controlling factors,such as overloading of livestock,population increasing and uneven grazing,further aggravate eco-functional degeneration of nature pastureland.