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Highlights • Streams in Fennoscandian production forests are subject to number of disturbances. • Operations during the forestry rotation cycle introduce stressors to small streams. • Individual stressors interact in time and space causing multiple stressor phenomena. • Aquatic multiple stressors are not well understood in forestry dominated landscapes. • Future research should focus on multiple stressors using experimental approaches. In this paper we describe how forest management practices in Fennoscandian countries, namely Sweden and Finland, expose streams to multiple stressors over space and time. In this region, forestry includes several different management actions and we explore how these may successively disturb the same location over 60–100 year long rotation periods. Of these actions, final harvest and associated road construction, soil scarification, and/or ditch network maintenance are the most obvious sources of stressors to aquatic ecosystems. Yet, more subtle actions such as planting, thinning of competing saplings and trees, and removing logging residues also represent disturbances around waterways in these landscapes. We review literature about how these different forestry practices may introduce a combination of physicochemical stressors, including hydrological change, increased sediment transport, altered thermal and light regimes, and water quality deterioration. We further elaborate on how the single stressors may combine and interact and we consequently hypothesise how these interactions may affect aquatic communities and processes. Because production forestry is practiced on a large area in both countries, the various stressors appear multiple times during the rotation cycles and potentially affect the majority of the stream network length within most catchments. We concluded that forestry practices have traditionally not been the focus of multiple stressor studies and should be investigated further in both observational and experimental fashion. Stressors accumulate across time and space in forestry dominated landscapes, and may interact in unpredictable ways, limiting our current understanding of what forested stream networks are exposed to and how we can design and apply best management practices.

Due to the directional flow of water, the study of streams is an inherently spatial undertaking. Since early in its emergence, stream research has emphasized the connection between the ecology of channels and the valleys they drain, as well as the connections between small headwaters and the larger rivers they become. Stream ecology has thus connected and contributed intermittently to spatial concepts derived from ecology in general. In this chapter, we consider three broad connections between streams and landscapes. First, streams are spatial systems in and of themselves, potentially conceptualized, both as gradients and as mosaics of distinct patches, at scales ranging from individual reaches to whole river networks and basins. Second, streams play distinct roles within the landscapes, serving as habitat and corridors for biota, and as locations for transformations of pollutants and other chemicals. Third, the ecological character of river networks varies dramatically across regions and continents, due to variation in climate, geology, and terrestrial vegetation, but increasingly due to regional patterns of alteration by human society.

Final ecosystem services (i.e. services that directly benefit humanity) depend fundamentally upon the various processes, regulated by organisms, which underpin ecosystem functioning and maintain ec ...