• Energy Research

AbstractAimLand 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.LocationFinland.Time period1968–2019.Major taxa studiedVascular plants.MethodsWe 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.ResultsIntensively 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 conclusionsFunctional 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.

AbstractAimLand 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.LocationFinland.Time period1968–2019.Major taxa studiedVascular plants.MethodsWe 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.ResultsIntensively 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 conclusionsFunctional 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.

Summary Few experimental studies have tested how abundance and diversity of grassland bryophytes respond to global environmental changes such as climate shifts and eutrophication. Because bryophytes in grasslands are low‐statured, and because plant height is a key functional trait governing plant responses to resource gradients, their responses to these factors could resemble those of better‐studied small vascular plants. Alternatively, traits unique to bryophytes could lead to qualitatively different responses than those of small vascular plants. In a semi‐arid Californian grassland system, where bryophytes are at relatively low abundance and their ecology has been little studied, we compared changes in cover and species richness of bryophytes and short‐statured vascular plants in response to 5 years of experimental fertilization, springtime watering and fertilization + watering, which produced strong gradients in vascular plant biomass. Supporting our hypotheses, the cover and richness of both bryophytes and short vascular plants were negatively related to total community biomass and tall vascular plant cover, and declined in response to the fertilization + watering treatment, in which the cover of tall vascular plants most strongly increased. Two divergent responses were also observed as follows: watering alone increased the cover of bryophytes but not short vascular plants, while fertilization alone reduced the cover of short vascular plants but not bryophytes. Bryophytes and short‐statured vascular plants in grasslands both may be expected to decline under projected global changes in climate and nutrient deposition that enhance total community biomass and competitive pressure. However, shifts in either precipitation or eutrophication regimes alone may have differential effects on bryophytes and short vascular plants in grasslands, and organism‐specific plant functional traits must also be considered. A lay summary is available for this article.

Summary Few experimental studies have tested how abundance and diversity of grassland bryophytes respond to global environmental changes such as climate shifts and eutrophication. Because bryophytes in grasslands are low‐statured, and because plant height is a key functional trait governing plant responses to resource gradients, their responses to these factors could resemble those of better‐studied small vascular plants. Alternatively, traits unique to bryophytes could lead to qualitatively different responses than those of small vascular plants. In a semi‐arid Californian grassland system, where bryophytes are at relatively low abundance and their ecology has been little studied, we compared changes in cover and species richness of bryophytes and short‐statured vascular plants in response to 5 years of experimental fertilization, springtime watering and fertilization + watering, which produced strong gradients in vascular plant biomass. Supporting our hypotheses, the cover and richness of both bryophytes and short vascular plants were negatively related to total community biomass and tall vascular plant cover, and declined in response to the fertilization + watering treatment, in which the cover of tall vascular plants most strongly increased. Two divergent responses were also observed as follows: watering alone increased the cover of bryophytes but not short vascular plants, while fertilization alone reduced the cover of short vascular plants but not bryophytes. Bryophytes and short‐statured vascular plants in grasslands both may be expected to decline under projected global changes in climate and nutrient deposition that enhance total community biomass and competitive pressure. However, shifts in either precipitation or eutrophication regimes alone may have differential effects on bryophytes and short vascular plants in grasslands, and organism‐specific plant functional traits must also be considered. A lay summary is available for this article.

AbstractIn the forest‐tundra ecotone of the North Fennoscandian inland, summer and winter temperatures have increased by two to three centigrades since 1965, which is expected to result in major vegetation changes. To document the expected expansion of woodlands and scrublands and its impact on the arctic vegetation, we repeated a vegetation transect study conducted in 1976 in the Darju, spanning from woodland to a summit, 200 m above the tree line. Contrary to our expectations, tree line movement was not detected, and there was no increase in willows or shrubby mountain birches, either. Nevertheless, the stability of tundra was apparent. Small‐sized, poorly competing arctic species had declined, lichen cover had decreased, and vascular plants, especially evergreen ericoid dwarf shrubs, had gained ground. The novel climate seems to favour competitive clonal species and species thriving in closed vegetation, creating a community hostile for seedling establishment, but equally hostile for many arctic species, too. Preventing trees and shrubs from invading the tundra is thus not sufficient for conserving arctic biota in the changing climate. The only dependable cure is to stop the global warming.

AbstractIn the forest‐tundra ecotone of the North Fennoscandian inland, summer and winter temperatures have increased by two to three centigrades since 1965, which is expected to result in major vegetation changes. To document the expected expansion of woodlands and scrublands and its impact on the arctic vegetation, we repeated a vegetation transect study conducted in 1976 in the Darju, spanning from woodland to a summit, 200 m above the tree line. Contrary to our expectations, tree line movement was not detected, and there was no increase in willows or shrubby mountain birches, either. Nevertheless, the stability of tundra was apparent. Small‐sized, poorly competing arctic species had declined, lichen cover had decreased, and vascular plants, especially evergreen ericoid dwarf shrubs, had gained ground. The novel climate seems to favour competitive clonal species and species thriving in closed vegetation, creating a community hostile for seedling establishment, but equally hostile for many arctic species, too. Preventing trees and shrubs from invading the tundra is thus not sufficient for conserving arctic biota in the changing climate. The only dependable cure is to stop the global warming.