Ant Diversity and Vegetation Composition in Hemlock Removal Experiment at Harvard Forest 2006

Ants comprise a considerable amount of animal biomass in terrestrial ecosystems and play major roles in ecological processes ranging from seed dispersal to soil turnover. Invasion by the hemlock woolly adelgid will transform late-successional hemlock forests into earlier successional mixed hardwood-white pine forests or red-maple wetlands. Understanding how ant assemblages vary in different habitat types allows for predictions of how hemlock decline could alter the composition of ant assemblages, with implications for a wide range of ecosystem processes. An ongoing study at the Simes Tract of Harvard Forest is documenting the effects of invasion and land-use history on ant biodiversity. Surveys from 2003 to 2005 focused on ant structure in hemlock and hardwood microhabitats in the Harvard Forest Hemlock Removal Experiment, in which hemlock forest response to deforestation by the hemlock woolly adelgid (Adelges tsugae) and to selective logging is being examined (Ellison et al. 2005). In the summer of 2006, we surveyed a greater range of microhabitat types with two objectives. First, to collect rare or elusive species in hemlock and hardwood stands that may have gone uncollected in previous years. Second, to sample forest communities not included in previous years - white pine, swamp, and rocky slope - for ant species unique to these microhabitats. We found fourteen newly documented species of ants in the Simes Tract - nine of which were in an open, swamp. Aphaenogaster rudis and Camponotus pennsylvanicus were the only ant species found in all microhabitat types. In a canonical correspondence analysis, A. rudis and C. pennsylvanicus were associated most strongly with hemlock stands and low species richness of understory plants.

蚂蚁在陆地生态系统中占据可观的动物生物量占比，且在从种子传播到土壤周转的诸多生态过程中发挥核心作用。铁杉球蚜（Adelges tsugae）的入侵会将顶极演替的铁杉林转变为处于较早演替阶段的硬阔-白松混交林或红枫湿地。明晰不同生境类型下蚂蚁群落的组成差异，可用于预测铁杉林衰退如何改变蚂蚁群落结构，进而对各类生态过程产生连锁影响。当前在哈佛森林Simes样地开展的一项研究，正记录铁杉球蚜入侵及土地利用历史对蚂蚁生物多样性的影响。2003至2005年开展的调查聚焦于哈佛森林铁杉移除实验中铁杉林与硬阔林微生境中的蚂蚁群落结构；该实验旨在探究铁杉林对铁杉球蚜所致林木衰退及择伐的响应（Ellison等，2005）。2006年夏季，我们针对更多类型的微生境开展了调查，本次调查设定了两个目标：其一，采集此前调查中可能遗漏的铁杉林与硬阔林内的稀有或难捕获蚁类物种；其二，对此前未涉及的林分类型——白松林、沼泽地与岩石坡地——开展采样，以获取这些微生境特有的蚁类物种。本次调查在Simes样地中共记录到14种蚂蚁新记录种，其中9种发现于开阔沼泽生境中。亮毛蚁（Aphaenogaster rudis）与宾夕法尼亚弓背蚁（Camponotus pennsylvanicus）是唯一在所有微生境类型中均被采集到的蚁类物种。在典范对应分析中，亮毛蚁（A. rudis）与宾夕法尼亚弓背蚁（C. pennsylvanicus）与铁杉林分及林下植物低物种丰富度呈现最强的相关性。