DroughtNet: Establishing the International Drought Experiment at Cedar Creek tIDE (trait IDE): Aboveground Biomass

Droughts are forecast to become increasingly frequent and intense in many regions worldwide, likely impacting community structure, ecosystem functioning, and ecosystem services. The International Drought Experiment (IDE) is a coordinated, multi-site drought experiment requiring only a moderate investment of time and resources by investigators. This coordinated, distributed experiment will quantify the impacts of extreme drought across a wide range of terrestrial ecosystems based on a common experimental design and a comparable suite of measurements. We aim to establish two stand-alone experiments following the IDE design at Cedar Creek. Precipitation reduction shelters will be established during spring 2017 to simulate a 1 in 100 year dry event, which at our site corresponds to removing 43% of annual precipitation. The tIDE (trait IDE) study will be established in e248 plots in the Big Biodiversity experiment field. The three precipitation treatments described above will be applied at the subplot level and fully crossed with the two current irrigation treatments (ambient or ambient plus ~2 cm per week of irrigation) and with two of the current fertilization treatments (unamended or 14 g N m-2), with six true replicate plots for each of the 12 treatment combinations, for a total of 72 subplots. Standard measurements across these two experiments and all other DroughtNet sites will include peak aboveground biomass clipping, soil carbon and nitrogen content, plant community composition from % cover, plant traits, and meteorological measurements (daily precipitation, air temperature). Many sites will also measure light availability, root biomass, soil moisture, and decomposition rates of tea bags and tongue depressors. Pre-treatment data will be collected during 2016. The experiment is expected to have minimal impacts on Cedar Creek and on other projects.

全球诸多区域的干旱预计将愈发频繁且强度加剧，很可能会对群落结构、生态系统功能以及生态系统服务产生影响。国际干旱实验（International Drought Experiment, IDE）是一项协同开展的多站点干旱实验，研究人员仅需投入适度的时间与资源即可参与。这项分布式协同实验将基于统一的实验设计与可比的标准化测量方案，量化极端干旱对各类陆地生态系统的影响。我们计划在雪松溪（Cedar Creek）依照IDE框架搭建两个独立实验。2017年春季将架设降水减少遮蔽装置，以模拟百年一遇的干旱事件——在本研究区域，该装置对应移除43%的年降水量。tIDE（性状IDE，trait IDE）研究将设于大型生物多样性实验田的e248样地中。前述三种降水处理将在亚样地级别实施，并与当前两种灌溉处理（自然降水或自然降水外加每周约2厘米的灌溉）以及两种现有施肥处理（未施肥或每平方米施加14克氮）进行完全交叉组合；12种处理组合各设置6个真实重复样地，总计72个亚样地。本实验与所有其他DroughtNet站点的标准测量内容包括：地上峰值生物量刈割取样、土壤碳氮含量、基于盖度百分比的植物群落组成、植物性状以及气象监测数据（日降水量、气温）。众多站点还将测量光照可用性、地下生物量、土壤湿度以及茶包与压舌板的分解速率。实验前的基线数据将于2016年完成采集。本实验预计对雪松溪区域及其他研究项目的影响极小。