Department of Natural Resources and the Environment, University of New Hampshire, Durham, NH, 03824, USA.
Department of Biology and Wildlife and Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, 99775, USA.
Nat Commun. 2022 Mar 9;13(1):1230. doi: 10.1038/s41467-022-28630-z.
River networks regulate carbon and nutrient exchange between continents, atmosphere, and oceans. However, contributions of riverine processing are poorly constrained at continental scales. Scaling relationships of cumulative biogeochemical function with watershed size (allometric scaling) provide an approach for quantifying the contributions of fluvial networks in the Earth system. Here we show that allometric scaling of cumulative riverine function with watershed area ranges from linear to superlinear, with scaling exponents constrained by network shape, hydrological conditions, and biogeochemical process rates. Allometric scaling is superlinear for processes that are largely independent of substrate concentration (e.g., gross primary production) due to superlinear scaling of river network surface area with watershed area. Allometric scaling for typically substrate-limited processes (e.g., denitrification) is linear in river networks with high biogeochemical activity or low river discharge but becomes increasingly superlinear under lower biogeochemical activity or high discharge, conditions that are widely prevalent in river networks. The frequent occurrence of superlinear scaling indicates that biogeochemical activity in large rivers contributes disproportionately to the function of river networks in the Earth system.
河流网络调节着大陆、大气和海洋之间的碳和养分交换。然而，河流处理的贡献在大陆尺度上还没有得到很好的限制。累积生物地球化学功能与流域大小的比例关系（异速缩放关系）为量化河流网络在地球系统中的贡献提供了一种方法。在这里，我们表明，累积河流功能与流域面积的异速缩放关系从线性到超线性，其缩放指数受到网络形状、水文条件和生物地球化学过程速率的限制。由于河流网络表面积与流域面积呈超线性缩放，因此在很大程度上独立于基质浓度的过程（例如总初级生产力）的异速缩放呈超线性。对于通常受基质限制的过程（例如反硝化作用），在具有高生物地球化学活性或低河流流量的河流网络中呈线性，但在生物地球化学活性较低或流量较高的情况下，异速缩放变得越来越超线性，这种情况在河流网络中广泛存在。超线性缩放的频繁发生表明，大河中的生物地球化学活性对地球系统中河流网络的功能贡献不成比例。
