人工柠条-荒漠草地交错带拟步甲昆虫群落多样性

选取宁夏东部盐池县人工柠条灌丛-荒漠草地交错带为研究样地,以距离梯度形式,利用巴氏诱罐法对拟步甲科昆虫群落多样性进行了调查,研究了边缘效应对拟步甲昆虫群落多样性的影响。共采集拟步甲昆虫1405只,分属8属13种。结果表明,克小鳖甲和弯齿琵甲个体数量分别占总个体数的32.74%和43.27%,为该地区的优势种类。拟步甲昆虫在人工柠条灌丛-荒漠草地交错带的分布可分为3种类型,优势种克小鳖甲和弯齿琵甲属于栖息地广布型,但二者并没有表现出十分均匀的适应性,而且他们在各样带的分布呈显著负相关,克小鳖甲的分布趋向于沙生荒漠环境,弯齿琵甲的分布趋向于柠条灌丛;常见种蒙古漠王、小皮鳖甲的分布偏向于喜好荒漠草地;异距琵甲、奥氏真土甲、网目土甲和淡红毛隐甲的分布则偏向于喜好柠条灌丛。拟步甲昆虫丰富度与Shannon-Wiener多样性沿边缘分别向柠条灌丛和荒漠草地内部降低,个体数量总体上沿柠条灌丛、交错带向荒漠草地内部降低,但各样带差异不显著。从季节动态看,荒漠草地和柠条灌丛物种多样性季节变化相似,3种生境拟步甲活动密度季节变化相似。边缘效应强度分析呈现边缘正效应。CCA排序图显示分类地位相近的物种在生态适应上具有趋同性。多元回归分析表明,植被密度影响拟步甲昆虫群落的优势种和个体数量,植被盖度和高度分别影响拟步甲群落的均匀度和丰富度。主坐标分析(PCo A)排序表明人工柠条灌丛-荒漠草地交错带的拟步甲昆虫群落组成与柠条灌丛内部没有明显分化,但趋于向柠条灌丛生境演替。

Diversity of darkling beetle community in the artificial cultivation Caragana intermedia shrub-desert grassland ecotone in Yanchi County, Ningxia, China

Forty-five percent of darkling beetle species recorded in China occur in the northern arid and semi-arid areas. Some ecological studies have suggested that tenebrionid beetles can be used as effective indicators of vegetation degradation and soil desertification in desert ecosystems because they are well-adapted desert conditions. Large areas of artificial shrubland have been established on China''s desert steppe, but little is known about how this shrubland influence ground-dwelling arthropods. We studied the distribution of darkling beetles (Coleoptera: Tenebrionidae) across the ecotone between man-made Caragana intermedia shrubland and natural desert steppe to evaluate the effects of desert vegetation restoration on ground-dwelling beetle assemblages in Northwestern China. Using pitfall traps, beetles were sampled along five transects crossing the boundary between the artificial shrubland and natural desert steppe. The study was conducted from June to October in 2012 in Yanchi, Ningxia, Northwestern China. A total of 1405 tenebrionid beetles were collected, belonging to 13 species and 8 genera. Of these species, Microdera kraatzi and Blaps femoralis femoralis were the most common, accounting for 32.74% and 43.27% of all individuals, respectively. Darkling beetles were divided into three groups by habitat: (1) habitat generalists, which were numerous in all habitats, e.g., M. kraatzi and B. femoralis femoralis (M. kraatzi was most abundant in sandy steppe, while B. femoralis femoralis occurred mostly in shrubland); (2) desert steppe specialists, e.g., Platyope monglica and Scytosoma pygmaeum; and (3) shrub specialists, e.g., Blaps kirishenkoi, Eumylada oberbergeri, Gonocephalum reticuluatum, and Crypticus rufipes. Species richness and Shannon-Wiener diversity were higher at the boundary between shrubland and desert steppe than in either habitat, and abundance was greatest in shrubland, declining towards the desert steppe. However, there were no statistically significant differences between these three indices among the three habitats. Seasonal variation in Shannon-Wiener diversity in the desert steppe was similar to that in shrubland. Activity density in the three habitats were shown with the similar seasonal changes. Analysis of the intensity of edge effects showed positive effects at the edge. Canonical correspondence analysis (CCA) suggested that related species occupied similar habitats. Multiple linear regression showed that vegetation density was related to the activity density of the dominant species, and the vegetation cover and height were important factors associated with beetle evenness and richness indices. Principal coordinate analysis (PCoA) showed that beetle assemblages at the ecotone between the artificial Caragana shrubland and desert steppe showed no significant difference with those in the interior of the artificial Caragana shrubland, suggesting that the community structure of darkling beetles at the ecotone was changing to resemble the assemblages in shrubland.