Vegetation Warming Experiment: 15N Uptake Experiment Arctagrostis latifolia Canopy Traits, Utqiagvik (Barrow), Alaska, 2018

This dataset consists of measured Arctagrostis latifolia canopy traits harvested from vegetation warming experiment enclosures and paired control plots located on the BEO, Utqiavik, Alaska. Harvest types include both natural abundance and enriched A. latifolia. Canopy traits measured include leaf area index (LAI), specific leaf area (SLA) and maximum height. Vegetation warming chambers (Zero Power) were deployed on the Barrow Environmental Observatory (BEO), Utqiavik, Alaska. These chambers (Figure 1) consistently elevated air temperatures by approximately 4°C using a self-venting system described by Lewin et al (2017). Five chambers were deployed from June 17, 2018 to September 24, 2018 on the BEO within a 1 km2 area centered on 71.275N, -156.641W. Each chamber was co-located with an ambient plot where temperatures were not manipulated on patches of tundra containing the target species Arctagrostis latifolia. An intensive field campaign in late July investigated the impact of warming had on A. latifolia biomass, chemistry, and uptake of 15N labeled ammonia that was injected into the surface soils for one week. Initial measurements were taken on July 21, 2018. Harvest occurred on July 27, 2018. Water-extractable nutrients in soils were measured in July following harvests of A. latifolia plants and underlying soils. Availability of ammonia, nitrate, and phosphate throughout the growing season was measured by extracting nutrients bound to anion and cation binding resins deployed from July through September. Environmental variables (thaw depth, surface soil temperatures, surface soil moisture) were measured. Leaf traits and root traits of A. latifolia were also measured. This dataset includes one csv file and one pdf file. The Next-Generation Ecosystem Experiments: Arctic (NGEE Arctic), was a research effort to reduce uncertainty in Earth System Models by developing a predictive understanding of carbon-rich Arctic ecosystems and feedbacks to climate. NGEE Arctic was supported by the Department of Energy's Office of Biological and Environmental Research. The NGEE Arctic project had two field research sites: 1) located within the Arctic polygonal tundra coastal region on the Barrow Environmental Observatory (BEO) and the North Slope near Utqiagvik (Barrow), Alaska and 2) multiple areas on the discontinuous permafrost region of the Seward Peninsula north of Nome, Alaska. Through observations, experiments, and synthesis with existing datasets, NGEE Arctic provided an enhanced knowledge base for multi-scale modeling and contributed to improved process representation at global pan-Arctic scales within the Department of Energy's Earth system Model (the Energy Exascale Earth System Model, or E3SM), and specifically within the E3SM Land Model component (ELM).

本数据集采集自阿拉斯加州乌特恰维克（Utqiavik，原巴罗）巴罗环境观测站（Barrow Environmental Observatory, BEO）的植被增温实验围区及其配对对照样地中的宽叶北极禾草（Arctagrostis latifolia）冠层性状实测数据。采集的样品涵盖自然丰度与富集型两类该物种。

本次实测的冠层性状包括叶面积指数（leaf area index, LAI）、比叶面积（specific leaf area, SLA）以及最大株高。该实验使用的植被增温箱（零能耗型，Zero Power）部署于阿拉斯加州乌特恰维克的巴罗环境观测站，其采用Lewin等于2017年报道的自通风系统，可将空气温度稳定提升约4℃（图1）。

2018年6月17日至2018年9月24日，研究团队在以71.275°N、-156.641°W为中心的1平方千米区域内的巴罗环境观测站样地中部署了5台该类增温箱。每台增温箱均配套设置1处未进行温度调控的对照样方，样方内为包含目标物种的苔原斑块。

2018年7月下旬开展的密集野外调查，探究了增温对该物种生物量、化学组分以及注入表层土壤1周的15N标记氨吸收的影响。初始测量于2018年7月21日完成，样品采集工作则于2018年7月27日开展。在采集该物种植株及其下层土壤后，研究人员于同年7月对土壤中的水浸提养分进行了测定。整个生长季内的氨、硝酸盐与磷酸盐有效性，通过7月至9月部署的阴离子与阳离子结合树脂吸附后提取养分的方法进行测定。此外，研究团队还测定了解冻深度、表层土壤温度、表层土壤湿度等环境变量，以及该物种的叶片性状与根系性状。

本数据集包含1个CSV格式文件与1个PDF格式文件。

下一代北极生态系统实验（Next-Generation Ecosystem Experiments: Arctic, NGEE Arctic）项目旨在通过构建对富碳北极生态系统的预测性理解及其对气候的反馈机制，降低地球系统模型的不确定性。该项目由美国能源部生物与环境研究办公室资助。

NGEE Arctic项目设有2个野外研究站点：1）位于阿拉斯加州乌特恰维克（原巴罗）附近北坡的巴罗环境观测站北极多边形苔原沿海区域；2）阿拉斯加州诺姆以北苏华德半岛的不连续永久冻土区域的多处样地。

通过实地观测、控制实验与现有数据集的综合分析，NGEE Arctic项目为多尺度建模提供了更为完善的知识库，并助力美国能源部地球系统模型——能源极端尺度地球系统模型（Energy Exascale Earth System Model, E3SM），尤其是其E3SM陆面模型组件（ELM），在全球泛北极尺度下提升了过程表征精度。