Eight Mile Lake Research Watershed, Carbon in Permafrost Experimental Heating and Drying Research (CiPEHR and DryPEHR): Weekly 13C Keeling Plot Signatures of Ecosystem Respiration from CiPEHR, DryPEHR and vegetation removal plots, and auxilliary data, 2015

The Carbon in Permafrost Experimental Heating Research (CiPEHR) project addresses the following questions: 1) Does ecosystem warming cause a net release 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?, and 3) How do winter and summer warming alone, and in combination, affect ecosystem C exchange? We are answering these questions using a combination of field and laboratory experiments to measure ecosystem carbon balance and radiocarbon isotope ratios at a warming experiment located in an upland tundra field site near Healy, Alaska in the foothills of the Alaska Range. How does warming and water table change impact the phenology of dominant plant species? 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 achieved using an automated pumping system that lowers the water table in the dry plots. Soil warming and OTC air warming on CIPEHR plots began in 2008; OTCs and drying on DryPEHR in 2011, though the soil warming effect had legacy since 2008. Vegetation removal was done outside the CiPEHR footprint, in July 2012. All vegetation was clipped at the surface and plots were trenched to 30cm, regrowth was prevented by frequent weeding and by 2015 very little new growth was observed in the plots. Vegetation removal plots were paired with undisturbed, vegetated plots. The data presented here specifically addresses the questions, 1) What is the seasonal signal of ecosystem respiration 13C during the growing season, from snow melt to snow fall, 2) How does permafrost degradation (though soil warming) and moisture trajectory affect the sources of ecosystem respiration, and 3) What is the signal of ecosystem respiration in the absence of vegetation, and how does the signal change seasonally? This data set contains calculated Keeling Plot Reco estimates of 13C used for publication, accompanying environmental and biological data, and R code to calculate Keeling Plot intercepts from high-frequency raw 13C and CO2 data.

多年冻土碳实验加热研究（Carbon in Permafrost Experimental Heating Research, CiPEHR）项目旨在解答以下科学问题：1）生态系统升温是否会导致碳从生态系统向大气发生净释放？2）占土壤碳库主体的老碳分解过程是否会影响生态系统碳损失？3）单独及联合开展的冬季与夏季升温如何影响生态系统碳交换？本项目结合野外与实验室实验手段，在阿拉斯加山脉山麓、阿拉斯加州希利附近的高地苔原实地升温实验站点，测定生态系统碳平衡与放射性碳同位素比值，以解答上述问题。
针对“升温与地下水位变化如何影响优势植物物种的物候”这一问题，本团队依托与CiPEHR项目同址的升温与干旱联合实验（DryPEHR）开展研究，该实验站点同样位于阿拉斯加山脉山麓、阿拉斯加州希利附近的高地苔原实地。此处的升温处理指：在积雪覆盖月份通过雪栅栏实现土壤“加温”，并结合开顶箱（open top chambers, OTC）实现生长季空气温度升温（约1℃）。干旱处理则通过自动化抽水系统降低干旱样地的地下水位来实现。
CiPEHR项目的土壤加温与OTC空气加温实验始于2008年；DryPEHR的OTC安装与干旱处理始于2011年，但其土壤加温效应自2008年便已存在遗留效应。2012年7月，研究团队在CiPEHR实验覆盖区域外开展了植被移除实验：所有植被均在地表处被剪除，样地被开挖至30cm深度，并通过频繁除草抑制植被再生；至2015年，样地中几乎未观察到新的植被生长。植被移除样地与未受干扰的植被覆盖样地采用配对实验设计。
本数据集专门针对以下科学问题：1）在融雪至降雪的生长季内，生态系统呼吸的13C同位素季节信号特征如何？2）多年冻土退化（通过土壤加温实现）与水分动态如何影响生态系统呼吸的碳源？3）无植被覆盖时生态系统呼吸的信号特征如何，且该信号随季节发生何种变化？本数据集包含用于发表文章的13C同位素基林图（Keeling Plot）生态系统呼吸估算值、配套的环境与生物数据，以及用于从高频原始13C与CO2数据计算基林图截距的R代码。