Ecology. 2014 Jan;95(1):44-55. doi: 10.1890/12-1628.1.
The magnitude of cross-ecosystem resource subsidies is increasingly well recognized; however, less is known about the distance these subsidies travel into the recipient landscape. In streams and rivers, this distance can delimit the "biological stream width," complementary to hydro-geomorphic measures (e.g., channel banks) that have typically defined stream ecosystem boundaries. In this study we used meta-analysis to define a "stream signature" on land that relates the stream-to-land subsidy to distance. The 50% stream signature, for example, identifies the point on the landscape where subsidy resources are still at half of their maximum (in- or near-stream) level. The decay curve for these data was best fit by a negative power function in which the 50% stream signature was concentrated near stream banks (1.5 m), but a non-trivial (10%) portion of the maximum subsidy level was still found > 0.5 km from the water's edge. The meta-analysis also identified explanatory variables that affect the stream signature. This improves our understanding of ecosystem conditions that permit spatially extensive subsidy transmission, such as in highly productive, middle-order streams and rivers. Resultant multivariate models from this analysis may be useful to managers implementing buffer rules and conservation strategies for stream and riparian function, as they facilitate prediction of the extent of subsidies. Our results stress that much of the subsidy remains near the stream, but also that subsidies (and aquatic organisms) are capable of long-distance dispersal into adjacent environments, and that the effective "biological stream width" of stream and river ecosystems is often much larger than has been defined by hydro-geomorphic metrics alone. Limited data available from marine and lake sources overlap well with the stream signature data, indicating that the "signature" approach may also be applicable to subsidy spatial dynamics across other ecosystems.
生态系统间资源补助的规模已得到广泛认可，但人们对这些补助能在多大程度上进入受补助的景观区域却知之甚少。在溪流和河流中，这个距离可以界定“生物溪流宽度”，与通常定义溪流生态系统边界的水-地貌措施（如河道两岸）形成互补。在这项研究中，我们使用元分析来定义一个与距离相关的陆地“溪流特征”，用以表示溪流-陆地补助与距离的关系。例如，50%的溪流特征确定了景观中资源补助仍处于最大（溪流内或附近）水平一半的点。这些数据的衰减曲线最符合负幂函数，其中 50%的溪流特征集中在河道两岸（1.5 米）附近，但仍有很大一部分（10%）的最大补助水平在距水边缘 0.5 公里之外被发现。元分析还确定了影响溪流特征的解释变量。这提高了我们对允许空间广泛的补助传输的生态系统条件的理解，例如在高生产力的中等级溪流和河流中。从该分析中得出的多元模型可能对管理者实施缓冲区规则和保护溪流及河岸功能的策略有用，因为它们有助于预测补助的范围。我们的研究结果强调，大部分补助仍在靠近溪流的地方，但补助（和水生生物）也有能力长距离扩散到相邻的环境中，而溪流和河流生态系统的有效“生物溪流宽度”通常比水-地貌指标单独定义的要大得多。从海洋和湖泊来源获得的有限数据与溪流特征数据很好地重叠，表明“特征”方法也可能适用于其他生态系统的补助空间动态。
