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In Scandinavia, three gradients (poor-rich, water table, margin-expanse) are considered in vegetation classification of mires. We re-analysed the data of Paavo Havas from 1961 on sloping fens in eastern Finland using NMDS ordination analysis, which also revealed a three-dimensional structure of the classic gradients, with the poor-rich gradient associated with pH. Water table level, and the unstable-stable water regime gradient were also of importance. Our analysis confirmed the interpretation by Havas but further stressed the role of the poor-rich gradient as the main direction of variation in sloping fens. Species richness increased with pH, and from mire expanse to margin vegetation, but decreased towards too wet or seasonally too dry conditions. Eastern Finnish sloping-fen plant communities resemble those in sloping fens elsewhere in Scandinavia, but also those in montane-subalpine-alpine fens in central and southeastern Europe.

Aim Land use is the foremost cause of global biodiversity decline, but species do not respond equally to land‐use practices. Instead, it is suggested that responses vary with species traits, but long‐term data on the trait‐mediated effects of land use on communities are scarce. Here we study how forest understorey communities have been affected by two land‐use practices during 4–5 decades, and whether changes in plant diversity are related to changes in functional composition. Location Finland. Time period 1968–2019. Major taxa studied Vascular plants. Methods We resurveyed 245 vegetation plots in boreal herb‐rich forest understories, and used hierarchical Bayesian linear models to relate changes in diversity, species composition, average plant size, and leaf economic traits to reindeer abundance, forest management intensity, and changes in climate, canopy cover and composition. We also studied the relationship between species evenness and plant size across both space and time. Results Intensively managed forests decreased in species richness and had increased turnover, but management did not affect functional composition. Increased reindeer densities corresponded with increased leaf dry matter content, evenness and diversity, and decreased height and specific leaf area. Successional development in the canopy was associated with increased specific leaf area and decreased leaf dry matter content and height in the understorey over the study period. Effects of reindeer abundance and canopy density on diversity were partially mediated by vegetation height, which had a negative relationship with evenness across both space and time. Observed changes in climate had no discernible effect on any variable. Main conclusions Functional traits are useful in connecting vegetation changes to the mechanisms that drive them, and provide unique information compared to turnover and diversity metrics. These trait‐dependent selection effects could inform which species benefit and which suffer from land‐use changes and explain observed biodiversity changes under global change.

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SUMMARYPatches of intermediate fen, dominated by Molinia caerulea, Trichophorum cespitosum and Loeskypnum badium and resembling low aapa mire strings (lawn strings), were found on a sloping rock outcrop near the summit of Koitelainen Hill, central Finnish Lapland. Using eighteen 56-cm diameter plots and NMSordination we compared the vegetation of the patches to that of (A) corresponding larger fens belonging to a well-known north-Finnish mire site type Loeskypnum badium fen, (B) to that of narrow seepage soaks dominated by Warnstorfia sarmentosa, and (C) to that of a local heath patch. Ordination of the sample plots suggested a 'horizontal gradient' (general wetness) and three 'vertical gradients' (1: stability of the water regime; 2: poor-rich species; 3: frost action). Species richness increased along both the horizontal and the vertical gradient, from wet seepage areas to drier Loeskypnum badium fens, to intermediate fen patches and finally to the heterogeneous heath patch. We regard the fen patches of Koitelainen as belonging to an ecologically extreme group, the water-fluctuating lawn-fens. The water-fluctuating lawn-fens are characterised by a thin peat layer with high humification degree, caused by intermittent aeration during drought periods, as well as by the specific community composition, which is evidently partly structured by the seasonal drought tolerances of individual fen species.