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BackgroundRiparian forests surrounding streams host high biodiversity values, but are threatened by clear-cut logging. Narrow buffer strips of about 15 m are commonly left between the stream and the clear-cut, but studies suggest that the buffer width should be at least 30 m to protect riparian plant communities. Moreover, selective logging is often allowed on the buffer strips in order to increase economic gain. We used an experiment of 43 riparian sites where buffer strip width and selective logging within the strip were manipulated and supplemented with unlogged control sites. We report the short-term changes in the community composition of vascular plants and mosses near the stream (0–15 m distance).Results15-meter buffers are not enough to protect the vascular plant communities from changes caused by a clear-cut irrespective of the selective logging on the buffer strip. For moss communities 15-m buffers were not enough if they were selectively logged. Relative to the control sites, we observed no significant changes in community composition of vascular plants or mosses in the sites with 30-m buffer strips, whether selectively logged or not.ConclusionsWe conclude that buffer strips of 15 m are not sufficient to protect streamside plant communities even in the short term, but that buffers of 30 m should be left on both sides of the stream. Selective logging appears not to have effects on buffers that are at least 30 m wide. Thus, it may be more reasonable to increase buffer width and to allow selective logging on the wider buffer in order to compensate for the economic losses than to leave all trees on a narrow and ecologically insufficient buffer.Electronic supplementary materialThe online version of this article (10.1186/s12898-019-0225-0) contains supplementary material, which is available to authorized users.

Riparian forests have cool and humid microclimates, and one aim of leaving forested buffer strips between clear-cut areas and streams is to conserve these microclimatic conditions. We used an experimental study set up of 35 streamside sites to study the impacts of buffer strip width (15 or 30 meters) and selective logging within the buffer strips on summer-time air temperature, relative air humidity and canopy openness 12 years after logging. The buffer strip treatments were compared to unlogged control sites. We found that 15-meter buffer strips with or without selective logging and 30-meter buffer strips with selective logging were insufficient in maintaining temperature, relative humidity and canopy openness at similar levels than they were in control sites. In contrast, 30-meter buffer strips differed only little from control sites, but they did have significantly lower mean air humidity. Microclimatic changes were increased by southern or southwestern aspect of the clearcut, and by logging on the opposite side of the stream. We also tested how the cover of three indicator mosses (Hylocomium splendens, Pseudobryum cinclidioides and Polytrichum commune) had changed (from pre-logging to 12 years post-logging) in relation to post-logging air temperature, relative air humidity and canopy openness. We found that each of the species responded to at least one of these physical conditions. Air humidity was the most significant variable for explaining changes in the cover of the indicator moss species, suggesting that the changes in this microclimatic component has biological impacts. We conclude that to preserve riparian microclimatic conditions and species dependent on those, buffer strips should exceed 30 meters in width, and not be selectively logged. Wider buffer strips are required if the clear-cut is towards south or southwest, or if the two sides of the stream are logged at the same time or during subsequent years.

Questions How does the presence of grazers impact plant diversity at various spatial scales? What are the effects on plant β‐diversity and its two components, species turnover and nestedness? Are the effects caused by defoliation, trampling or defecating? Location Twenty‐four currently grazed and 24 abandoned wood‐pasture sites in Central Finland. Methods The species richness of vascular plants and bryophytes was studied at four spatial scales: within 4‐m2 subplots (α1), within 100‐m2 plots (α2), within sites (α3) and within the landscape (γ). β‐Diversity was studied between subplots within plots (β1), between plots within sites (β2) and between sites within the landscape (β3). Results Currently grazed sites had higher species richness at all of the spatial scales (α1, α2, α3, γ) and higher within‐plot and within‐site β ‐diversities (β1 and β2). At the within‐plot scale (β1) plant β‐diversity was increased primarily by variation in defoliation. At this scale both turnover and nestedness were increased by grazers. At the larger within‐site scale (β2) only turnover was increased, and it was mostly caused by variation in trampling intensities. Within the landscape (β3) currently grazed sites had higher between‐site turnover and lower nestedness than abandoned sites. Conclusions Grazing creates and maintains high species richness and β‐diversity of vascular plants and bryophytes, mostly due to high species turnover between patches. Defoliation, dunging and trampling are all important turnover agents, although their relative importance varies with spatial scale. At the landscape scale the currently grazed sites had high species turnover between them, and thus the conservation of all grazing‐dependent species requires continued management at various sites, while high nestedness between abandoned sites implies that their biodiversity can be efficiently conserved through protecting the most species‐rich sites.