河西走廊天然固沙植被区地表甲虫多样性及其对沙漠化的指示作用

干旱、半干旱区沙漠化强烈影响动植物分布及多样性，地表甲虫是荒漠中主要的动物类群，它们对沙漠化引起的植被和土壤环境变化响应十分敏感。鉴于此，以河西走廊中部张掖绿洲外围的天然固沙植被区作为研究区，依据沙漠化发育程度选择流动沙丘（ASD）、丘间低地（IL）、半固定（SFSD）和固定沙丘（FSD）4种生境，调查了地表甲虫群落组成及影响甲虫分布的植被和土壤环境。研究发现，4种生境地表甲虫群落组成明显不同并存在季节变异，5月ASD与IL、SFSD和FSD生境地表甲虫群落的相异性大于8月。5月和8月SFSD生境地表甲虫活动密度均显著高于其他生境，8月FSD生境地表甲虫多样性指数显著高于其他生境。不同大小甲虫对沙漠化的响应模式不同，大中型甲虫对沙漠化的响应较小型甲虫敏感，这在5月表现尤为明显。地表甲虫与环境因子的RDA分析结果表明，12个植被和土壤环境因子解释了49.8%的地表甲虫群落变异，其中植被环境解释了甲虫群落变异的16.3%，土壤环境解释了甲虫群落变异的4.2%，植被和土壤环境相互作用解释了甲虫群落变异的29.3%。pRDA分析结果表明，草本物种丰富度、灌木盖度、土壤有机碳含量和粗砂含量是影响地表甲虫分布的主要环境因子，它们解释了43.7%的地表甲虫群落变异。Pearson相关分析表明，草本物种丰富度与地表甲虫活动密度呈显著正相关，而与地表甲虫均匀度呈显著负相关；灌木盖度与地表甲虫多样性呈显著正相关；地表甲虫物种丰富度与灌木盖度和草本物种丰富度均呈显著正相关。此外，研究还发现戈壁琵甲、克氏扁漠甲、中华砚甲和甘肃齿足象可以用于指示FSD生境，东鳖甲属昆虫可以用于指数SFSD生境，谢氏宽漠王可以用于指示IL及ASD生境。

Ground beetle diversity and their value as bioindicators for desertification in a natural desert of the middle of the Hexi Corridor, Northwest China

Sandy desertification strongly affected the distribution and diversity of plant and animals in arid and semiarid areas. Ground beetles were mainly animals in the sand ecosystems, and very sensitive responses to vegetation and soil environmental change derived from sandy desertification. In this study, we select a natural desert adjacent to Zhangye oasis of the middle of the Hexi Corridor as a research region. The active sand dunes (ASD), interdune lowlands (IL), semi-fixed sand dunes (SFSD) and fixed sand dunes (FSD) were conducted depending on the degree of desertification development. Ground beetles in four habitats collected by pitfall trapping, and environmental aspects related to the scattering of beetles were explored. We found that ground beetle communities were significant difference among the four habitats and seasonal variation on ground beetle assemblage. The average dissimilarity of beetle community among ASD, IL, SFSD and FSD habitats in May was greater than that in August. The activity density of ground beetles in SFSD habitats was significantly higher than that in other three habitats in May and August, and diversity of ground beetles in FSD habitats was significantly higher than that in other three habitats in August. The response patterns of ground beetles to desertification were different with body sizes. The large and medium beetles response to desertification was more sensitive than small beetles, especially in May. The results of redundancy analysis (RDA) show that twelve vegetation and soil factors contributed to 49.8% of the variation in the ground beetles. Moreover, we found that vegetation, soil and the interaction between them are explained 16.3%, 4.2% and 29.3% of the variation in the ground beetles, respectively. The results of pRDA show that herbaceous species richness, shrub cover, soil coarse sand, and soil organic carbon content were fundamental environmental factors affecting the distribution of ground beetles, which contributed to 43.7% of the variation in the ground beetles. The Pearson correlation analysis shows that herbaceous species richness were significantly positive correlations with the activity density of ground beetles, and an opposite pattern was observed on the evenness index; the shrub cover was significantly positive correlation with diversity index of ground beetles; species richness of ground beetles was significantly positive correlation with herbaceous species richness and shrub cover. In addition, a strong indication of ground beetles for habitat type was found. Blaps gobiensis, Cyphogenia chinensis, Deracanthus potanini and Sternotrigon kraatzi were indicator taxa for FSD habitats. Anatolica spp. were indicator taxa for SFSD habitats. Mantichorula semenowi can be used as indicator taxa for IL and ASD habitats. In short, community structure and species identity of ground beetles in the sandy desert can be used as indicator species for sandy desertification derived from vegetation and soil degradation.