warmXtrophic: plant community responses to direct and herbivore-mediated indirect effects of climate warming across multiple years at Kellogg Biological Station Long-Term Ecological Research Sites (KBS LTER), Michigan, USA, and University of Michigan Biological Station (UMBS), Michigan, USA.

Climate change has both direct and indirect effects on ecological communities. Whereas most climate change ecology experiments manipulate abiotic drivers to measure direct effects of climate on species or communities, fewer quantify the indirect effects through biotic interactions, especially over multiple sites and years. In this factorial experiment we manipulate temperature through open-top chambers, and the level of insect herbivory through insecticide. At two early successional field sites separated by 3 degrees of latitude and 3°C of mean annual temperature (University of Michigan Biological Station, Pellston, MI and Kellogg Biological Station, Hickory Corners, MI), 6 replicate 1-m2 plots per treatment were installed in May 2015. 12 plots per site are at ambient temperature, 12 are warmed with year-round non-UV filtering polycarbonate and wood frame construction OTCs for tall-stature plants (Welshofer et al. 2018 MEE). Insecticide reduces insect herbivory in half the plots (Welshofer et al. 2018 Oecologia). Over the course of the experiment, OTCs warmed the plant communities by 1.9°C-3.0°C on average over the growing season. Each year, through 2021, plant traits and community responses were measured at the species level: plant phenology (green-up, flowering, flowering duration, seed set); plant percent cover (aerial % cover of the 1m2 plot); plant traits (specific leaf area, C and N content), herbivory damage to leaves, and plant species biomass (only in 2021). Further methodological details are found within each response variable metadata. This experiment is ongoing and further data package updates are planned. L0 data is available upon request. R scripts can be found here: https://github.com/SpaCE-Lab-MSU/warmXtrophic. The biotic and abiotic community context and relative strengths of direct vs. indirect effects may yield ecological surprises under climate change unless addressed together. Large-scale experiments like this one can improve our ability to understand and forecast ecological responses to climate change, especially how biotic interactions mediate species responses to climate change across biotic and abiotic contexts.

气候变化对生态群落兼具直接与间接影响。当前多数气候变化生态学实验均通过操控非生物驱动因子，以探究气候对物种或群落的直接影响，但通过生物交互作用量化间接影响的研究相对匮乏，尤其缺乏多站点、多年际尺度的相关研究。
本析因实验通过开顶箱（open-top chambers, OTCs）操控温度，借助杀虫剂调控昆虫植食水平。实验设置于两处早期演替野外样地，两地纬度相差3°、年平均气温差值为3℃，分别为密歇根大学生物站（密歇根州佩尔斯顿）与凯洛格生物站（密歇根州希科里科纳斯）；2015年5月，每处理组设置6个重复的1平方米样方。每个样地中，12个样方维持环境温度，另有12个样方采用适配高大植株的全年非紫外过滤聚碳酸酯木结构开顶箱进行增温（Welshofer等，2018，MEE）。半数样方施加杀虫剂以降低昆虫植食压力（Welshofer等，2018，《Oecologia》）。
实验期间，开顶箱在整个生长季内为植物群落带来的平均增温幅度为1.9℃至3.0℃。截至2021年，实验每年均在物种水平上测定植物性状与群落响应指标，具体包括：植物物候（返青期、开花期、开花持续时长、结实量）；植物盖度（1平方米样方的地上盖度百分比）；植物性状（比叶面积、碳氮含量）；叶片植食损伤程度；以及植物物种生物量（仅2021年测定）。各响应变量的元数据中记载了更多实验方法细节。
本实验仍在进行中，后续将推出数据集包的更新版本。L0级数据可根据申请获取。R脚本可从以下链接获取：https://github.com/SpaCE-Lab-MSU/warmXtrophic。
若未同时考量生物与非生物的群落背景，以及直接与间接影响的相对强度，气候变化背景下的生态过程可能出现难以预料的结果。此类大型野外实验有助于提升我们理解与预测生态系统对气候变化响应的能力，尤其是在生物与非生物背景下，生物交互作用如何调控物种对气候变化的响应这一核心问题。