Lawrence Berkeley National Laboratory, Berkeley, United States of America.
Lawrence Berkeley National Laboratory, Berkeley, United States of America.
Sci Total Environ. 2019 Feb 1;649:284-299. doi: 10.1016/j.scitotenv.2018.08.251. Epub 2018 Aug 21.
There is significant spatial and temporal variability associated with greenhouse gas (GHG) fluxes in high-latitude Arctic tundra environments. The objectives of this study are to investigate temporal variability in CO and CH fluxes at Barrow, AK and to determine the factors causing this variability using a novel entropy-based classification scheme. In particular, we analyzed which geomorphic, soil, vegetation and climatic properties most explained the variability in GHG fluxes (opaque chamber measurements) during the growing season over three successive years. Results indicate that multi-year variability in CO fluxes was primarily associated with soil temperature variability as well as vegetation dynamics during the early and late growing season. Temporal variability in CH fluxes was primarily associated with changes in vegetation during the growing season and its interactions with primary controls like seasonal thaw. Polygonal ground features, which are common to Arctic regions, also demonstrated significant multi-year variability in GHG fluxes. Our results can be used to prioritize field sampling strategies, with an emphasis on measurements collected at locations and times that explain the most variability in GHG fluxes. For example, we found that sampling primary environmental controls at the centers of high centered polygons in the month of September (when freeze-back period begins) can provide significant constraints on GHG flux variability - a requirement for accurately predicting future changes to GHG fluxes. Overall, entropy results document the impact of changing environmental conditions (e.g., warming, growing season length) on GHG fluxes, thus providing clues concerning the manner in which ecosystem properties may be shifted regionally in a future climate.
在高纬度北极苔原生态系统中，温室气体（GHG）通量存在显著的时空变异性。本研究的目的是调查阿拉斯加巴罗地区 CO 和 CH 通量的时间变化，并使用新的基于熵的分类方案确定导致这种变化的因素。具体来说，我们分析了哪些地貌、土壤、植被和气候特性在连续三年的生长季节中最能解释 GHG 通量（不透明室测量）的变化。结果表明，CO 通量的多年变化主要与土壤温度变化以及生长季早期和晚期的植被动态有关。CH 通量的时间变化主要与生长季植被的变化及其与季节性解冻等主要控制因素的相互作用有关。在北极地区很常见的多边形地面特征也表现出 GHG 通量的显著多年变化。我们的研究结果可用于确定田间采样策略的优先级，重点是在能够最大程度解释 GHG 通量变化的地点和时间收集测量数据。例如，我们发现，在 9 月（开始冻结期）的高中心多边形中心采样主要环境控制因素，可以对 GHG 通量变化提供重要约束——这是准确预测未来 GHG 通量变化的要求。总体而言，熵结果记录了环境条件变化（例如，变暖、生长季长度）对 GHG 通量的影响，从而提供了有关生态系统特性在未来气候中可能在区域范围内发生变化的线索。
