Ants Under Climate Change at Harvard Forest and Duke Forest 2009-2015

Experimental field studies are needed to understand the consequences of global
climatic change for local community structure and associated ecosystem processes. We
are using 5-m diameter open-top environmental chambers and 1m pvc minichambers to
simultaneously manipulate air and soil temperatures at the Harvard Forest and at the
Duke Forest in North Carolina. These field manipulations are designed to reveal the
effects of temperature increases on the populations, communities, and associated
ecosystem services of assemblages of ground-foraging ants. Ants are a model taxon for
studying effects of global climatic change because they comprise the dominant
fraction of animal biomass in many terrestrial communities and because they provide
essential ecosystem services, including soil turnover, decomposition, and seed
dispersal. The experiment is designed to test three predictions: 1. Projected
atmospheric warming will lead to declines in ant species’ abundances at the warmer,
southern extent of their ranges in the US. Conversely, projected atmospheric warming
will lead to increases in abundance or range extensions of ant species at the cooler,
northern extent of their ranges in the US. 2. Warming will change the relative
abundance and composition of ant communities, and will lead to the loss of ant
biodiversity. 3. Warming will potentially diminish ecosystem processes and services
provided by ants, particularly with respect to the dispersal of seeds. To explore
these, we are conducting two experiments. In one experiment, twelve open-top chambers
at each site which will each be exposed air temperatures ranging from 1.5 to 7 deg C
above ambient; soil temperatures will be increased simultaneously from 0 to ~ 2 deg
C. After an initial year of pre-intervention measurements, the experiment will run
for 3 consecutive years of continuous warming. In the second experiment, shade cloth
and plastic greenhouse sheeting will be used to increase or decrease temperature by
0.5 deg C in sixty minichambers. The minichamber experiment was conducted in 2009 and
will continue into 2010. The response variables measured in both experiments include
ant activity, population densities and colony sizes of focal species, ant community
diversity and species composition, and rates of seed dispersal and predation as
mediated by ants.

为阐明全球气候变化对本地群落结构及关联生态系统过程的影响，亟需开展野外实地实验。

本研究采用直径5米的开顶式环境箱（open-top environmental chambers）与1米长聚氯乙烯（PVC）微型温室，同步对哈佛大学森林（Harvard Forest）及北卡罗来纳州杜克森林（Duke Forest）的空气与土壤温度进行人工调控。此类野外调控实验旨在揭示温度升高对地表觅食蚁类集合体的种群、群落及相关生态系统服务的影响。

蚂蚁是研究全球气候变化效应的模式类群（model taxon），因其在多数陆地群落中占据动物生物量的主导份额，且可提供土壤扰动、有机质分解与种子传播等关键生态系统服务。本实验旨在验证三项核心预测：
1. 预估的大气升温将导致美国境内蚁类物种在其分布范围南部较温暖区域的种群丰度下降；反之，升温将促使美国境内分布范围北部较凉爽区域的蚁类物种丰度提升或分布范围扩张。
2. 升温将改变蚁类群落的相对丰度与物种组成，并引发蚂蚁生物多样性丧失。
3. 升温可能削弱蚂蚁所提供的生态系统过程与服务，尤以种子传播相关的服务为甚。

为探究上述预测，本研究开展两项平行实验：其一为开顶箱实验：两处研究站点各设置12个开顶式环境箱，各箱将接受比环境空气温度高1.5至7℃的升温处理，同时同步将土壤温度提升0至约2℃。实验将先开展为期1年的干预前基线测量，随后连续开展3年的持续升温处理。其二为微型温室实验：使用遮阳布与塑料温室膜，在60个微型温室中将温度调控至较环境偏高或偏低0.5℃。该微型温室实验于2009年启动，并将持续至2010年。

两项实验均测量以下响应变量：蚂蚁活动强度、目标物种的种群密度与巢群规模、蚁类群落多样性与物种组成，以及蚂蚁介导的种子传播与捕食速率。