The natural flow regime is considered the “master variable” in lotic systems, controlling structure and function at organismal, population, community, and ecosystem levels. We sought to estimate forested headwater stream metabolism across two dominant flow regimes ( Runoff and Groundwater ) in northern Arkansas and evaluate potential differences in, and drivers of, gross primary production, ecosystem respiration, and net ecosystem metabolism. Flow regimes differed in intermittency, substrate heterogeneity, hyporheic connectivity, and dominant water source (subsurface runoff vs. groundwater), which we expected to result in differences in primary production and respiration. Average daily gross primary production (GPP) and ecosystem respiration (ER) estimated from field data collected from May 2015-June 2016 tended to be greater in Groundwater streams. Respiration was positively related to discharge (R 2 = 0.98 p< 0.0001) and net metabolism became more heterotrophic with increasing average annual discharge across sites (R 2 = 0.94, p= 0.0008). Characterizing ecosystem-level responses to differences in flow can reveal mechanisms governing stream metabolism and, in turn, provide information regarding trophic state and energy inputs as efforts continue to determine global trends in aquatic carbon sources and fates.

中文翻译：

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欧扎克森林小溪中河道流量的适度增加与生态系统呼吸正相关

自然水流被认为是抽水系统中的“主要变量”，可以控制有机体，种群，社区和生态系统的结构和功能。我们试图估算阿肯色州北部两个主要流动流态（径流和地下水）中的森林源头水流代谢，并评估初级生产总值，生态系统呼吸作用和净生态系统代谢的潜在差异及其驱动因素。流动方式在间歇性，底物非均质性，水流连通性和主要水源（地下径流与地下水）方面有所不同，我们预计这会导致初级生产和呼吸的差异。根据2015年5月至2016年6月收集的实地数据估算，地下水流中的平均每日初级总产值（GPP）和生态系统呼吸（ER）往往更高。呼吸与流量呈正相关（R 2 = 0.98 p <0.0001），并且随着各站点的年平均流量增加，净代谢变得更加异养（R 2 = 0.94，p = 0.0008）。表征生态系统水平对流量差异的反应可以揭示控制河流新陈代谢的机制，并随着努力确定水生碳源和命运的全球趋势，提供有关营养状态和能量输入的信息。