民勤连古城自然保护区群落结构和物种多样性特征分析

通过物种多样性指数、林地承载力以及土壤水分等指标对民勤连古城自然保护区荒漠群落的结构和物种多样性以及影响因子进行了研究。结果表明:(1)群落的优势层片为灌木层,其物种组成和结构比较稳定,受环境变化的影响较小,而草本层为不稳定层片;(2)荒漠群落的物种多样性指数均偏低,生态优势度较高,群落的生态功能主要由优势种群或建群种群实施,在无外界干扰情况下,优势种群或建群种群的稳定性可以揭示群落的稳定性;(3)土壤水分是影响群落结构的主导因子,而降水是土壤水分的主要来源,对群落结构具有显著影响。土壤异质性对群落结构同样具有显著影响,是第二主导因子,其物种多样性指数为黏性土壤>灰棕荒漠土>风沙土;(4)群落物种多样性与其林地承载力无一定规律的相关性,灌木层片中,二者呈对数相关(y=64.787ln(x) 214.04,R2=0.829,P<0.01),能够比较科学地揭示物种多样性与林地承载力之间的关系,而草本层中二者呈幂指数相关(y=0.3198e6.1654x,R2=0.6999,P<0.01),反映了林地承载力受环境因子变化的影响。

Community Structure and Species Diversity in Liangucheng Nature Reserve of Minqin County

The structures and species diversity and their affecting factors of desert communities in Liangucheng Nature Reserve of Minqin County were studied in terms of species diversity index,forestland bearing capacity and soil water.It was shown that(1) in the communities the shrubs formed the dominating layer whose species composition and structure were stable and less liable to suffer environmental changes and the herbaceous layer was unstable;(2) The desert communities showed a low species diversity index and strong ecological dominance and their ecological functions mainly depended on the dominant populations or edificato populations whose stability could indicate community stability on condition that there were no external influence;(3) Soil water was the dominating factor affecting the community structures and rainfall as the source of soil water exerted significant influences on the community structures;soil heterogeneity exerted significant influences on the community structures as well and was the second dominating factor affecting them,and the species diversity indexes with different soils followed the decreasing order of clayed soil,grey brown desert soil and aeolian sandy soil;(4) The species diversity was not regularly related to the forestland bearing capacity and the two appeared logarithmically correlated in the shrub layer(y=64.787ln(x) 214.04,R~2=0.829,P<0.01),which reasonably revealed the relationship between species diversity and forestland bearing capacities;but the two appeared exponentially correlated(y=(0.3198)e~(6.1654x),R~2=0.6999,P<0.01) in the herbaceous layer,which indicated the impact of environmental factors on forestland bearing capacity.