Direct and Indirect Drivers of Energy and Nutrient Availability in Freshwater Ecosystems Across Spatial Scales
Direct and Indirect Drivers of Energy and Nutrient Availability in Freshwater Ecosystems Across Spatial Scales
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DOI：
10.1029/2022gb007580
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发表时间：
2023-05
影响因子：
5.2
通讯作者：
Hannah M. Fazekas;J. Brun;A. Wymore
中科院分区：
文献类型：
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作者：
Hannah M. Fazekas;J. Brun;A. Wymore
淡水生态系统反映了它们所处的景观。这些系统的生物地球化学从根本上与气候和分水岭过程有关，这些过程控制着水的通量和能量和营养物质的调动，在溪水化学中留下了不同的印记。解开这些过程是困难的，因为它们在不同空间的多个尺度上运行。我们研究了气候、土壤和流域特征在调节直接和间接途径中的相对重要性，这些途径影响了小溪和河流在空间尺度上的碳和氮有效性。我们的数据集包括景观和气候变量，以及横跨美国大陆的459条小溪和河流的37995个碳和氮化学测量数据。模型解释了大陆尺度的一小部分碳和氮浓度(分别为25%和6%)，但在较小的空间尺度上分别解释了61%和40%的碳和氮浓度。水文气象过程在调节溶质有效性方面一直很重要，但其机理影响在空间尺度上是不同的。水文气象对浓度的影响往往不是直接的，而是由土壤特性对碳和流域特性对氮的影响。例如，降水的季节性在确定碳浓度方面往往很重要，因为它在生物地理气候空间尺度上对土壤水分有影响，而在大陆尺度上它对浓度有直接影响。我们的结果表明，水文气象强迫仍然是能量和养分浓度的始终如一的驱动因素，但影响模式的机制在广泛的空间尺度上有所不同。
Freshwater ecosystems reflect the landscapes in which they are embedded. The biogeochemistry of these systems is fundamentally linked to climate and watershed processes that control fluxes of water and the mobilization of energy and nutrients imprinting as variation in stream water chemistry. Disentangling these processes is difficult as they operate at multiple scales varying across space. We examined the relative importance of climate, soil, and watershed characteristics in mediating direct and indirect pathways that influence carbon and nitrogen availability in streams and rivers across spatial scales. Our data set comprised landscape and climatic variables and 37,995 chemistry measurements of carbon and nitrogen across 459 streams and rivers spanning the continental United States. Models explained a small fraction of carbon and nitrogen concentrations at the continental scale (25% and 6%, respectively) but 61% and 40%, respectively, at smaller spatial scales. Hydrometeorological processes were always important in mediating the availability of solutes but the mechanistic implications were variable across spatial scales. The influence of hydrometeorology on concentrations was often not direct, rather it was mediated by soil characteristics for carbon and watershed characteristics for nitrogen. For example, the seasonality of precipitation was often important in determining carbon concentrations through its influence on soil moisture at biogeoclimatic spatial scales, whereas it had a direct influence on concentrations at the continental scale. Our results suggest that hydrometeorological forcing remains the consistent driver of energy and nutrient concentrations but the mechanism influencing patterns varies across broad spatial scales.