祁连山中段植被群落的时空格局变化

Spatiotemporal Distribution Pattern of Vegetation Communities in the Middle Section of the Qilian Mountains

充分了解植被群落时空格局分布特征是开展生态环境恢复工作的前提。选择祁连山中段寺大隆林场为研究区,对1976、1991、2001、2016年的LANDSAT影像进行地物分类,并利用3种景观指数对植被群落生境破碎化程度进行分析,同时运用CA-Markov模型对植被2031年的分布情况作出预测。结果表明：人为因素是导致植被群落变化的主要原因;1976—2016年,祁连山中段寺大隆林场植被群落的分布面积发生了巨大的变化,乔木和草地分布面积分别减少了91 km^2和169 km^2;1976—2001年,乔木、灌木和草地群落的平均斑块面积（MPA）分别减少了1.22 km^2、0.14 km^2和0.16 km^2,聚合指数（AI）分别减少了2.79、0.03和8.77,平均分维数（Fd）分别增加了0.013、0.001和0.005,植被群落生境破碎化严重;2001—2016年,乔木、灌木和草地群落的平均斑块面积（MNA）分别增加了0 km^2、0.13 km^2和0.02 km^2,聚合指数（AI）分别增加了2.38、0.21和6.55,平均分维数（Fd）分别减小了0.005、0.002和0.002,植被生境得到修复;在现行趋势下,预测2031年乔木面积为409 km^2,灌木面积为486 km^2,草地面积为550 km^2,在面积分布上基本与1976年水平相当,植被生境恢复效果显著。

It is a precondition of regenerating ecological environment to fully understand the spatial and temporal distribution pattern of vegetation communities. In this paper,a vegetation classification was carried out based on the LANDSAT images in 4 years of 1976,1991,2001 and 2016. The classified results were used to get three landscape indexes,i. e.,the mean patch area（ MPA）,fractal dimension（ F_d） and aggregation index（ AI）,which were used to analyze the degree and driving forces of vegetation habitat change. Based on the classification for 2001 and 2016,the vegetation distribution in 2031 was predicted by CA-Markov model. The results showed that human activities were the main factors resulting in the change of vegetation communities. The distribution of vegetation communities was changed a lot during the period of 1976-2016,the areas of forests and grasslands were reduced by 91 km^2 and169 km^2 respectively. From 1976 to 2001,the MNAs of forests,shrubberies and grasslands were reduced by 1. 22 km^2,0. 14 km^2 and 0. 16 km^2,the AIs of forests,shrubberies and grasslands were decreased by 2. 79,0. 03 and8. 77,and the Fds of forests,shrubberies and grasslands were increased by 0. 013,0. 001 and 0. 005,respectively.The degree of vegetation community fragmentation was serious. But from 2001 to 2016,the MNAs of forests,shrubberies and grasslands were enlarged by 0 km^2,0. 13 km^2 and 0. 02 km^2,the AIs of forests,shrubberies and grasslands were increased by 2. 38,0. 21 and 6. 55,and the Fds of a forests,shrubberies and grasslands were decreased by 0. 005,0. 002 and 0. 002,respectively. The habitat of vegetation communities was gradually regenerated after2001. The predicted areas of forests,shrubberies and grasslands in 2031 are 409 km^2,486 km^2 and 550 km^2 respectively,which nearly equaled to those in 1976. A significant effect of ecological conservation policy had been achieved.