荒漠景观破碎化条件下啮齿动物群落beta多样性变化特征

The variation characteristics of the beta diversity of rodent communities in fragmented landscape in the Alxa desert,China

2002～2010年,采用夹日法对内蒙古阿拉善荒漠区禁牧、轮牧、过牧和开垦4种不同人为干扰生境中啮齿动物群落β多样性进行了研究,同时分析不同生境的灌木植物群落特征来探讨人为干扰下的景观破碎化。依据人为干扰下景观破碎的情况将研究区域内生境梯度的变化按照:禁牧到轮牧、轮牧到过牧、过牧到开垦、禁牧到过牧、禁牧到开垦、轮牧到开垦进行划分,分别利用Jaccard指数、Sorenson指数和Cody指数分析景观破碎化条件下啮齿动物群落β多样性变化特征。结果表明,不同生境梯度间3种β多样性指数差异均显著(P<0.05),禁牧到过牧梯度β多样性差异最大。不同干扰生境间的灌木植物群落特征差异极显著(P<0.01),Shannon-Wiener指数、Simpson指数和物种数均表现为轮牧区>过牧区>禁牧区>开垦区。环境变化程度与β多样性变化的程度一致。人为干扰是该区域景观破碎化的主要原因,特别是放牧活动,导致环境异质性显著增加。在荒漠区,这种随环境梯度造成异质性加大而增加的β多样性,并不是由物种增加较大导致,而是由啮齿动物群落物种组成差异和变化增大所致。

This study was conducted in four different habitats of the Alax desert of Inner Mongolia including a grazing-pro- hibited site, a rotational-grazing site, an over-grazing site and farmland. Rodent communities were sampled using snaptraps for a single day each month during April, July and October from 2002 to 2010, and beta diversity of rodent communities in the different habitats was analyzed. The characteristics of shrub communities also were analyzed to investigate landscape fragmentation under different disturbance conditions. The variation of the four habitats along with gradient were divided into six classes based on the amount of landscape fragmentation. The Jaccard＇ s diversity index, Sorenson＇ s diversity index and Cody diversity index were used to analyze the variation in the beta diversity of the rodent communities. The results showed that the three beta diversity indices differed significantly among all gradients between habitats （ P 〈 0. 05 ） , and the variance was the most obvious between grazing-prohibited areas and the over-grazing site in the gradient. The Shannon-Wiener in- dex, Simpson index and the species number in the shrub communities were significantly different among studies sites （P 〈 0. 01 ）, and showed the following trends ： rotational-grazing site 〉 over-grazing site 〉 grazing-prohibited site 〉 farmland. The region was considered a fragmented landscape if the degree of variation for environment conditions and the beta diversity was similar. In addition, the main reason for the landscape fragmentation in the region was the human-caused disturbance, particularly the grazing activities, which drove the heterogeneity of environment significantly. The beta diversity increase a- long with the increase of environment gradient lead to heterogeneity, which was caused by the increase in difference and variation of the species composition between rodent communities rather than the increase of species in arid desert region.