Patterns of hydrologic control over stream water total nitrogen to total phosphorus ratios
Patterns of hydrologic control over stream water total nitrogen to total phosphorus ratios
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DOI：
10.1007/s10533-009-9394-9
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发表时间：
2010-07-01
期刊：
影响因子：
4
通讯作者：
Finlay, Jacques C.
中科院分区：
文献类型：
--
作者：
Green, Mark B.;Finlay, Jacques C.
许多生态学家和生物地球化学家通过解决 N:P 比率来探索氮 (N) 和磷 (P) 循环的相互作用。虽然 N:P 比率被认为对流水生态系统的组成和功能非常重要，但对溪流水 N:P 比率变化的基本控制仍然知之甚少。低 N:P 比（小于 16）的溪流在干旱气候中比在温和气候中更有可能出现，这表明可能存在水文或景观控制。我们探讨了流域水文对溪流水中总氮与总磷（TN：TP）比率变化的重要性，以及基于年平均降水量和观测到的TN：TP比率中值，这种变化在不同流域类别之间是否存在特征差异。非参数散点图分析适用于美国本土 57 个影响最小的流域的归一化 TN:TP 比率和相关流量 (Q) 测量。在季节尺度上，TN:TP比率在半干旱气候中与Q呈负相关，在湿润气候中与Q呈正相关。在风暴事件规模上，TN:TP 比率随着所有流域类别 Q 的增加而下降。结果广泛表明水文学是多个时间尺度上 TN:TP 比率变化的重要驱动因素。我们假设流域类别之间的广泛差异是由景观与溪流的连通性（连接的频率和程度）性质的变化所驱动的。溪流水中 N:P 比率的强烈物理控制与海洋中 N:P 比率的生物控制形成鲜明对比，这表明将利用海洋系统开发的化学计量理论应用于液体系统需要更广泛地考虑控制因素。
Many ecologists and biogeochemists explore the interaction of the nitrogen (N) and phosphorus (P) cycles by addressing N:P ratios. While N:P ratios are recognized as broadly important to the composition and functioning of lotic ecosystems, the fundamental controls on stream water N:P ratio variation remains poorly understood. Low N:P ratio (less than 16) streams appear more likely in arid climates than in mesic climates, suggesting possible hydrologic or landscape controls. We explored the importance of watershed hydrology to the variation of total N to total P (TN:TP) ratios in stream water, and whether such variation is characteristically different across watershed classes based on mean annual precipitation and median observed TN:TP ratio. Nonparametric scatter plot analysis was applied to normalized TN:TP ratios and associated discharge (Q) measurements from 57 minimally-impacted watersheds from the contiguous United States. At the seasonal scale, TN:TP ratios showed a negative relationship with Q in semiarid climates and a positive relationship with Q in humid climates. Over storm event scales, TN:TP ratios decline with increasing Q across all watershed classes. The results broadly indicate hydrology is an important driver of TN:TP ratio variation over multiple time scales. We hypothesize that the broad differences across watershed classes are driven by variation in the nature of connectivity (frequency and magnitude of connections) of the landscape to streams. A strong physical control of N:P ratios in stream water is in stark contrast to the biological control of N:P ratios in the oceans, suggesting that application of stoichiometric theory-developed using marine systems-to lotic systems requires a broader consideration of controlling factors.