宁夏盐池荒漠草原步甲物种多样性

Species diversity of carabid beetles in desert-steppe in Yanchi of Ningxia,China

采用巴氏罐诱法于2009年3月到10月对盐池四墩子3种不同类型荒漠草原的步甲物种组成、数量分布进行了系统调查,共获得步甲标本1318号,分属于9属15种,其中直角通缘步甲Pterostichus gebleri、蒙古伪葬步甲Pseudotaphoxnus mongolicus、径婪步甲Harpalus salinus和短翅伪葬步甲Pseudotaphoxnus brevipennis为优势种,个体数量分别占个体总数的33.08%、19.73%、15.94%和8.04%。多样性分析表明适度干扰荒漠草地的Shannon-Wiener多样性、丰富度和均匀度均高于低干扰和强干扰荒漠草地。群落相似性分析显示猪毛蒿和甘草混交带与围栏放牧带及柠条带有较高的相似性,蒙古冰草带和苜蓿与柠条混种带相似性较高。从时间动态上看,步甲群落的个体数量在8月份达到最高。4种优势种季节性变化分别是直角通缘步甲盛发期为8月,径婪步甲发生的高峰期为8、9月,短翅伪葬步甲在5月和8月,蒙古伪葬步甲7—10月个体数量均多;不同物种在不同类型荒漠草地出现的高峰期是不一致的。典范对应分析(CCA)分析表明土壤含水量是影响步甲分布的最重要环境因子,植物生物量和植被密度次之;土壤含水量与步甲的Shannon-Wiener多样性、均匀度显著负相关,与优势度呈显著正相关。

Little is known about how desert-steppe systems contribute to the conservation of functionally important insect groups,including carabid beetles.Carabids are frequently used in terrestrial ecology on account of their well-known autecology,wide distribution,sensitivity to environmental changes.Many ecological studies have used diversity indices to assess the impact of environmental disturbance.In particular,ground beetles have been advocated as a good group for assessing disturbance.The aim of this study was to evaluate the influence of desert-steppe structure and type on carabid biodiversity.Habitat distribution and seasonal occurrence of carabid beetles were determined using pitfall traps from March to October in 2009 in a desert-steppe in Sidunzi of Yanchi,Ningxia,Northwestern China.Six transects differing in the vegetation and disturbance were selected so as to represent three habitat types： minimal disturbance（Stipa bungeana grassland）,moderately-disturbed（Caragana microphylla shrubs grassland with Artemisia blepharolepis and Clycyrrhiza uralensis,fence grazing dominated by Caragana microphylla and Cynanchum komarovii） and severely-disturbed desert-steppe（Agropyron mongolicum grassland and mixed plantation with Artemisia scoparia and Clycyrrhiza uralensis）.During the field research,a total of 1318 carabid beetles were collected,belonging to 15 species and 9 genera.Of these beetles,four species dominated,i.e.Pterostichus gebleri,Pseudotaphoxnus mongolicus,Harpalus salinus and Pseudotaphoxenus brevipennis accounting for 33.08%,19.73%,15.94% and 8.04% of the total,respectively.Shannon diversity,species abundance,and evenness were significantly higher in the three transects of the moderately-disturbed desert-steppe than in the three other transects of the minimaly and severely-disturbed desert-steppes.Based on species composition and abundance,cluster analysis grouped carabid beetles according to the level of habitat disturbance.The carabid assemblage in Caragana microphylla shrubs was more similar to that of grassland with Artemisia blepharolepis and Clycyrrhiza uralensis and fence grazing dominated by Caragana microphylla and Cynanchum komarovii,that of Agropyron mongolicum grassland was similar to that of mixed plantation with Artemisia scoparia and Clycyrrhiza uralensis.Monthly catch of carabid abundance reached a peak in August,with monthly variation in species recorded between transects.Pterostichus gebleri peaked in August,Harpalus salinus in August and September,Pseudotaphoxenus brevipennis in May and August,Pseudotaphoxnus mongolicus from July to October.Canonical correspondence analysis（CCA） explained 100% of the correlation between species and five environmental variables,suggesting that the occurrence of many species was related to changes in ecological conditions.Among the five factors,the soil water content,the plant biomass and plant density were the major factors affecting on the composition and spatial distribution of carabid beetles in the desert steppe.According to the correlation analysis,we also found that some environmental characteristics,i.e.,soil water content,plant biomass and plant density,significantly affected species composition and abundances.Additionally,soil water content was negatively correlated to Shannon diversity and evenness,and positively correlated to Simpson′s dominance.Based on these results,we conclude that the appropriate pressure of human disturbance has significantly contributed to the reestablishment and maintenance of the diversity of carabid in the studied area.