坝上地区农田和恢复生境地表甲虫多样性

The diversity of ground-dwelling beetles at cultivated land and restored habitats on the Bashang plateau

研究采用陷阱法对河北坝上崇礼县农田、禁牧草地及再造林地3种常见生境中地表甲虫进行了取样调查,分别从鞘翅目分科、步甲分种两个分类水平比较分析了不同生境中的生物多样性状况以评估生境恢复状况及其对生物多样性的影响,并探索在以生物多样性为指标评估生境恢复状况过程中,研究结论是否受分类水平的影响。结果显示,草地和林地具有较为相似鞘翅目和步甲的结构组成,但均显著不同于农田。农田较再造林地和禁牧草地具有更多的鞘翅目科数及步甲物种数,且均显著高于林地;农田中步甲群落的Fisher′sα多样性指数也显著地高于林地,但鞘翅目分科水平上的Fisher′sα多样性指数在各生境中没有差异。结果说明:(1)再造林和草地禁牧的生境修复活动在当前状态下对生物多样性恢复的作用尚不明显,仅是表现出促进了景观尺度上较高的Beta和Gamma多样性,而农田则在维持当地较高的生物多样性中扮演重要角色;(2)在鞘翅目分科和步甲科分种研究数据所反映的不同生境条件下的多样性和组成状况基本相同,因此在需要快速评估生境恢复状况且物种水平鉴定存在困难的时候,可以采用鞘翅目分科的数据替代指示生境恢复的状况并反映生境恢复对生物多样性影响的趋势,从而减少分类的难度并提高工作效率。但是物种水平的多样性状况更能显著反映生境间的差异。

Land degradation is one of the main causes for biodiversity declines.The restoration of degraded habitats by reforestation and decreased management intensity has therefore been proposed as an important measure for biodiversity conservation.A comparison between invertebrate assemblages from different habitats allows an evaluation of the impacts of anthropogenic land-use changes on biodiversity and an assessment of the effectiveness of restoration schemes.In this study,pitfall traps were used to sample ground dwelling beetles on four replicate plots representing three habitats;cultivated fields,replanted woodland and non-grazed grassland,at Chongli county,Bashang plateau in Northern China.The study region has experienced profound degradations due to overgrazing and land reclamation in past centuries and recently became a source area for dust storms affecting Beijing and Tianjing cities.The diversity of beetle families and ground beetle species were compared between habitats to investigate the following questions：（1） Do non-grazed grassland and replanted woodland harbor significantly more diverse beetle assemblages than intensively managed cultivated fields？（2） Do diversity data derived at species（ground beetles） and family level（all beetles） follow the same trends among habitats,and can therefore be interchangeably used to evaluate the environmental impacts of habitat change and the success of restoration schemes？ The results showed that（1） replanted woodland and non-grazed grassland harbored very similar carabid species assemblages and Coleoptera family assemblages,which were significantly different from assemblages on cultivated land;（2） a significantly greater number of both carabid species and Coleoptera families were found on cultivated land in comparison to replanted woodland and non-grazed grassland.For carabid assemblages,Fisher′s α was also significantly greater on cultivated land than at replanted woodland,but no significant differences between habitats were observed for beetle family diversity.The minor differences in beetle assemblages at grassland and woodland habitats might be explained by the fact that the woodland sites had been established on formerly degraded grassland,and hence initially harbored a similar species pool to the grassland plots.The higher productivity,potentially resulting in more diverse food resources,and the open spaces in parts of the cultivated land enhancing the effectiveness of pitfall traps,may be the main causes for the higher diversity in ground dwelling beetles sampled on cultivated land.The short time period of recovery and a complete lack of management could also have led to less diverse ground dwelling beetle assemblages on woodland and grassland sites.Although the diversity patterns at family level for all coleopterans showed similarities to patterns observed at species level in ground beetles,correlations of diversity values between these taxonomic levels were not significant,with the analysis at species level appearing more sensitive in detecting habitat changes.The results indicate that cultivated land in the study area plays an important role in enhancing the overall species pool,as it sustains diverse and unique ground dwelling beetle assemblages.Nonetheless,a diverse landscape mosaic consisting of cultivated land,grassland and replanted woodland is essential to sustain high levels in both beta-and gamma-diversity at larger scales.Moreover,the similarity of trends observed in patterns of carabid species diversity and diversity of beetle families among habitats hints at the feasibility of using family-level data as a surrogate indicator to quickly assess the environmental impacts of habitat change and the success of habitat restoration on beetle diversity at lower taxonomic levels,especially where the taxanomic knowledge at species level is limited.