Managed forests generally produce high water quality, but degradation is possible via sedimentation if proper management is not implemented during forest harvesting. To mitigate harvesting effects on total watershed sediment yield, it is necessary to understand all processes that contribute to these effects. Forest harvesting best management practices (BMPs) focus almost exclusively on overland sediment sources, whereas in‐and‐near stream sources go unaddressed although they can contribute substantially to sediment yield. Thus, we propose a new framework to classify forest harvesting effects on stream sediment yield according to their direct and indirect processes. Direct effects are those caused by erosion and sediment delivery to surface water from overland sources (e.g., forest roads). Indirect effects are those caused by a shift in hydrologic processes due to tree removal that accounts for increases in subsurface and surface flows to the stream such that alterations in water quality are not predicated upon overland sediment delivery to the stream, but rather in‐stream processes. Although the direct/indirect distinction is often implicit in forest hydrology studies, we have formalized it as a conceptual model to help identify primary drivers of sediment yield after forest harvesting in different landscapes. Based on a literature review, we identify drivers of these effects in five regions of the United States, discuss current forest management BMPs, and identify research needs.

中文翻译：

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森林采伐对美国森林流域沉积物产量的直接和间接影响

人工林通常会产生较高的水质，但是如果在森林采伐期间未进行适当的管理，则有可能通过沉淀而导致退化。为了减轻收获对流域沉积物总产量的影响，有必要了解导致这些影响的所有过程。森林采伐最佳管理实践（BMP）几乎完全集中于陆上沉积物来源，而近内流源虽然可以大大增加沉积物的产量，但却没有得到解决。因此，我们提出了一个新的框架，可以根据森林采伐对溪流沉积物直接和间接过程的影响进行分类。直接效果是由陆上水源（例如林道）向地表水中侵蚀和沉积物造成的。间接影响是指由于树木砍伐而导致水文过程发生变化而造成的影响，这种影响解释了流入河流的地下和地表水量的增加，因此水质的变化不是基于陆上沉积物向河流的输送，而是基于河流的过程。尽管直接/间接区别通常在森林水文学研究中是隐含的，但我们已将其正式化为概念模型，以帮助识别在不同景观下森林采伐后沉积物产量的主要驱动因素。根据文献综述，我们在美国五个地区确定了这些影响的驱动因素，讨论了当前的森林管理BMP，并确定了研究需求。