Dynamic stream network intermittence explains emergent dissolved organic carbon chemostasis in headwaters
Dynamic stream network intermittence explains emergent dissolved organic carbon chemostasis in headwaters
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DOI：
10.1002/hyp.13455
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发表时间：
2019-06-30
影响因子：
3.2
通讯作者：
Godsey, Sarah E.
中科院分区：
文献类型：
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作者：
Hale, Rebecca L.;Godsey, Sarah E.
溶解有机碳（DOC）的浓度各不相同的源头，变化通常与流域面积减少。我们假设，径流阻力可能是一个重要的来源，DOC浓度的变化在整个小流域，通过（a）时间的遗产干燥的有机质积累和生物群落和（B）与DOC源的连接空间格局。为了验证这些假设，我们在早春、夏末和深秋在爱达荷州东南部的一个25.5 km（2）的流域进行了三次天气水化学采样活动。使用变点分析，我们发现，DOC的变异崩溃在一个一致的位置（流域面积1.3至1.8 km（2））跨季节，这正好与流域面积的径流阻力的变异崩溃（1.5 km（2））。为了测试假设的机制，通过可能会影响DOC的不稳定性，我们开发了时间，空间和时空尺度的径流不稳定性和相关的DOC浓度。径流阻力是跨季节DOC的强预测因子，但不同的指标预测DOC取决于季节。季节性变化的影响，DOC的折射率反映了季节性变化，从瞬时到流路控制。一个度量，捕获源的空间连接显着预测DOC在高流量，DOC通常由运输控制。相比之下，当DOC通常由瞬时过程控制并且当干燥的遗留效应（例如，生物群落的减少可能会影响DOC。在某种程度上，不服从对DOC的影响超出了时间遗产。我们的研究结果表明，遗产的影响不传播下游在这个系统中。相反，快照的空间格局的上游河段的渗透性是至关重要的理解DOC的空间格局，通过连接DOC源，这些过程驱动模式的DOC，即使在常年河段。
Dissolved organic carbon (DOC) concentrations vary among headwaters, with variation typically decreasing with watershed area. We hypothesized that streamflow intermittence could be an important source of variation in DOC concentrations across a small watershed, through (a) temporal legacies of drying on organic matter accumulation and biotic communities and (b) spatial patterns of connectivity with DOC sources. To test these hypotheses, we conducted three synoptic water chemistry sampling campaigns across a 25.5-km(2) watershed in south-eastern Idaho during early spring, late summer, and late fall. Using changepoint analysis, we found that DOC variability collapsed at a consistent location (watershed areas 1.3 to 1.8 km(2)) across seasons, which coincided with the watershed area where variability in streamflow intermittence collapsed (1.5 km(2)). To test hypothesized mechanisms through which intermittence may affect DOC, we developed temporal, spatial, and spatio-temporal metrics of streamflow intermittence and related these to DOC concentrations. Streamflow intermittence was a strong predictor of DOC across seasons, but different metrics predicted DOC depending on season. Seasonal changes in the effects of intermittence on DOC reflected seasonal changes from instream to flowpath controls. A metric that captured spatial connectivity to sources significantly predicted DOC during high flows, when DOC is typically controlled by transport. In contrast, a reach-scale temporal metric of intermittence predicted DOC during the late growing season, when DOC is typically controlled by instream processes and when legacy effects of drying (e.g., diminished biological communities) would likely affect DOC. The effects of intermittence on DOC extend beyond temporal legacies at a point. Our results suggest that legacy effects of intermittence do not propagate downstream in this system. Instead, snapshots of spatial patterns of intermittence upstream of a reach are critical for understanding spatial patterns of DOC through connectivity to DOC sources, and these processes drive patterns of DOC even in perennial reaches.