黄土高原人工扰动生境中蜗牛组合特征及其对人类活动影响程度的指示

The impact of human activities on ecosystems has become an important area of global change research in recent years. However, the characteristics, extent and process of the impact of past and modern human activities on flora and fauna are still controversial. To date, assessing impacts of human activity on community have solely been based on limited biologic taxa, short time scale, and few research areas. Finding new indicators and assessing the degree of impact is a fundamental and important approach for accurate assessment of current and past human activities. Land snails, which are widely distributed and abundant in fossil records, are particularly sensitive to changing habitats caused by human activity. But until now, little is known of their characteristics of assemblages among different human-disturbed habitats and its relationship with the intensity of human activity. This project intends to investigate the assemblages, diversity, abundance of snail community in different human-disturbed habitats, based on the new surface snail samples from different human-disturbed habitats and existing database of extant land-snail. The objectives are to 1) compare the differences of snail assemblages in disturbed habitats and natural habitats; 2) identify characteristics of snail community under the background of human disturbance; 3) examine the extent of human activity on snail community by comparing the differences in different types of disturbances. On the basis of these efforts, we will try to reconstruct the history and progress of human activity in Guanzhong area since the Holocene. This project will contribute greatly to our knowledge of the influence of human activity on invertebrate community, and will also provide scientific evidence for a better understanding of how human activity affects community assemblages in the past, and predict future changes in biodiversity.

人类活动对生态系统的影响已成为近年来全球变化研究的重要领域，但过去和现代人类活动对动、植物群落影响的程度如何还存在争议。由于涉及生物类群、研究区域及时间尺度有限，如何识别过去人类活动信息仍具有很大不确定性。寻找人类活动信息新指标、评估人类活动对生物群落的影响程度是研究的突破点。陆生蜗牛因其迁徙能力弱、生态敏感性且具统计意义等特征，有望成为揭示人类活动影响程度的新手段。本项目计划对黄土高原不同扰动生境下（耕地、经济林、郊地、荒地、自然保护区和近原始生境等）蜗牛组合和群落结构进行系统分析，建立黄土高原人工扰动生境表土蜗牛组合数据库；甄别扰动生境和原始群落蜗牛结构的相似性和差异性，提取对人类活动有指示意义的蜗牛种类和组合特征；采用统计方法构建不同扰动背景下蜗牛群落组合与人类活动影响程度的关系，尝试分析并探讨过去人类活动对生物群落显著影响的时间、程度和过程，为预测未来生物群落的变化趋势提供依据。

人类活动对生态系统的影响已成为近年来全球变化研究的重要领域。我国北方黄土高原生态系统较为脆弱，对人类活动影响比较敏感，是早期农业起源与发展的重要中心地区。黄土高原人类活动从何时起显著影响生物群落？影响程度如何？一直是学术界关心的科学问题。有学者认为是5千年，有的认为是3千年和2千多年。这些认识主要来自考古记录和历史文献，缺少量化的、能明确反映人类活动影响的生物-地质记录。利用生物-地质记录来揭示人类活动影响过程，建立生物群落与人类活动影响程度的量化关系是研究的关键。本项目以黄土蜗牛为主要研究手段，通过对139个人类活动影响生境的表土蜗牛组合和189个蜗牛化石组合及其它指标的系统研究，获得以下新认识：1）完善采集中国北方自然生境和人类活动生境（耕地、经济林、定居地等）表土蜗牛样点，建立了中国北方人类影响-蜗牛组合数据库，甄别了自然生境与人类活动影响生境的不同蜗牛组合特征，通过典型对应分析（CCA）识别出与人类活动影响密切相关的蜗牛种类是C. fasciola, B. ravida, V. tenera等组合；2）采用加权平均偏最小二乘法（WAPLS）建立了蜗牛组合-人类影响指数（HII）定量转换函数，运用到泾川剖面蜗牛化石组合、重建了全新世以来黄土高原人类活动影响强度的变化过程，揭示了人类活动至少两千年前已经对无脊椎动物群落显著改造的影响过程；3）比较不同生物类群（蜗牛-植物群落）响应末次盛冰期以来环境变化过程，查明特征蜗牛属种的出现与特定的落叶乔木类（如榛属、栎属）组成密切相关，揭示了人类活动、气候变化通过食物网和栖息地环境间接影响陆生无脊椎动物群落的可能方式和过程。项目研究成果为认识过去人类活动（特别是农业活动）对自然生态系统的影响过程提供了有力证据。已在Quaternary Science Reviews、Palaeogeography, Palaeoclimatology, Palaeoecology、Science of the Total Environment、Global Ecology and Conservation、第四纪研究等刊物上发表成果5项。