Eight Mile Lake Research Watershed, Carbon in Permafrost Experimental Heating and Drying Research (DryPEHR): Growing season NDVI 2011-2015

This drying and warming experiment addresses the following questions: 1) Does ecosystem drying, warming and permafrost thaw cause a net release or uptake of C from the ecosystem to the atmosphere?, 2) Does the decomposition of old C that comprises the bulk of the soil C pool influence ecosystem C loss? 3) How do drying and warmign affect plant communities and ecosystem properties? We are answering these questions using a combined warming and drying experiment (DryPEHR), which is situated with the Carbon in Permafrost Experimental Heating Research (CiPEHR) project and located in an upland tundra field site near Healy, Alaska in the foothills of the Alaska Range. Warming treatment here refers to growing season air temperature warming (~1C) using open top chambers (OTC) combined with soil 'warming' using snow fences during the snow covered months. Drying is achieve using an automated pumping system that lowers the water table in the dry plots. Soil warming began in 2008; OTCs and drying in 2011. The Normalized Difference Vegetation Index (NDVI) was measured using a specialized handheld camera at individual plots throughout the 2011-2015 growing seasons.

本干湿与增温实验旨在解答以下科学问题：1）生态系统干旱化、增温与永久冻土融化，是否会引发碳元素从生态系统向大气的净释放或净吸收？2）占土壤碳库主体的老碳分解过程，是否会对生态系统碳流失产生影响？3）干旱化与增温会如何作用于植物群落与生态系统属性？本研究依托联合增温与干旱实验（DryPEHR）解答上述问题，该实验与永久冻土碳实验加热研究（Carbon in Permafrost Experimental Heating Research, CiPEHR）项目共同部署于阿拉斯加山脉山麓、阿拉斯加希利附近的高地苔原野外研究站点。本实验的增温处理方案为：在生长季利用开顶箱（open top chambers, OTC）实现空气温度增温（约1℃），在积雪覆盖期则通过雪栅栏实现土壤‘增温’。干旱处理则通过自动化抽水系统实现，用以降低干旱样地的地下水位。土壤增温实验始于2008年，而开顶箱安装与干旱处理则于2011年启动。归一化植被指数（Normalized Difference Vegetation Index, NDVI）于2011-2015年的每个生长季，通过专用手持相机在各实验样地中完成测定。