科尔沁和毛乌素沙地灌丛“虫岛”效应比较

选择科尔沙地和毛乌素沙地豆科与非豆科灌丛为研究对象,以灌丛外裸沙地为对照,通过手拣法调查了不同灌丛微生境中土壤动物群落组成与多样性,依据相对相互作用强度指数(RII)分析比较了不同水热地带沙地灌丛"虫岛"差异性及影响机制。结果表明:(1)在科尔沁沙地和毛乌素沙地分别获得36和28个类群,平均个体数分别为76只·m^-2和125只·m^-2。优势类群分别包括拟步甲科及其幼虫和步甲科,蚁科,常见类群分别为12和20个类群,稀有类群分别为22个和6个类群。(2)土壤动物个体数、丰富度和Shannon指数的灌丛"虫岛"RII值,均表现为毛乌素沙地显著高于科尔沁沙地(p<0.05),并且2种类型灌丛均呈现出正向作用(即聚集作用,RII>0)。(3)在2个沙地所有样地中,只有园蛛科、鳃金龟科幼虫和拟步甲科幼虫3个类群完全表征出灌丛"虫岛"现象。园蛛科和拟步甲科幼虫的灌丛"虫岛"RII值不同地带沙地间无显著差异性(p>0.05),而鳃金龟科幼虫RII值则均存在显著差异性(p<0.05)。豆科与非豆科灌丛在不同地带沙地中对"虫岛"表现出相反的作用结果。(4)群落水平上,毛乌素沙地灌丛"虫岛"作用强度高于科尔沁沙地,与水热等沙地气候条件密切相关,而与灌丛功能特性无关。种群水平上,不同土壤动物类群具有不同的灌丛"虫岛"现象,灌丛功能特性、沙地水热条件或者二者交互作用是其原因。

Comparison of "Arthropod Island" of Shrub Effect between Two Sandy Grasslands in Northern China

Taking the non-leguminous and leguminous shrubs as the subject and the adjacent open spaces as the control, an investigation on soil arthropods was carried on by hand-sorting method in summer, 2010, in the Horqin Sandy Land and the Mu Us Sandy Land. Based on the relative interaction intensity(RII), the "Arthropod Island" of shrub effect was compared between the two sandy grasslands. The results were shown that(1) the density and richness in Horqin and Mu Us were 76 individual·m^-2 and 36, and 125 individual·m^-2 and 28, respectively. The dominant groups included adult and larval Tenebrionidae in Horqin, while Carabidae and Formicidae in Mu Us, The number of common groups and rare groups was 12 and 22 in Horqin, and 20 and 6 in Mu Us.(2) The relative interaction intensity(RII) for the total density, richness and Shannon index of soil arthropods were markedly(p<0.05) higher in Mu Us compared with Horqin, regardless of functional traits of shrubs. Also a facilitative effect of shrubs were found on soil arthropods, i.e., RII>0.(3) Only Araneidae, Melolonthidae larvae, and Tenebrionidae larvae indicated the "Arthropod Island" of shrub effect in all the sites set in both desertified regions. The relative interaction intensity(RII) for the density of Araneidae and Tenebrionidae larvae was found to indicate no marked(p>0.05) differences, whereas that for the density of Melolonthidae larvae was found to indicate a marked(p<0.05) differences between the two desertified grasslands. Meanwhile, the non-leguminous and leguminous shrubs were found to indicate a reverse pattern of "Arthropod Island" of shrub effect from one desertified grassland to another.(4) In conclusion, a high level of "Arthropod Island" of shrub effect was found in Mu Us sandy grassland(multiannual rainfall:292 mm) compared with Horqin(397 mm) at the community level, regardless of functional traits of shrubs. At the population level, the difference in "Arthropod Island" of shrub effect on each arthropod taxa depended not only on the inherence of shrubs, but also on the climatic factors in different desertified regions.