Temporal biodiversity change following disturbance varies along an environmental gradient

Abstract

AimThe diversity and composition of natural communities are rapidly changing due to anthropogenic disturbances. Magnitude of this compositional reorganization varies across the globe, but reasons behind the variation remain largely unknown. Disturbances induce temporal turnover by stimulating species colonizations, causing local extinctions, altering dominance structure, or all of these. We test which of these processes drive temporal community changes, and whether they are constrained by natural environmental gradients. Moreover, we assess to what degree identity shifts translate to changes in dominance structure.LocationFinland.Time periodObservations 1985–2006, disturbance history > 140 years.Major taxa studiedVascular plants.MethodsWe investigated temporal turnover of boreal forest understorey in response to disturbance, here forest management, along a soil fertility gradient. We disentangle the roles of species gains, losses and abundance changes in driving temporal turnover in response to and after disturbance by comparing turnover rates in different forest age categories along a fertility gradient. We quantify temporal turnover using richness‐based complement of Jaccard’s similarity index and proportional‐abundance based dissimilarity index. We also test whether disturbance history or fertility influence the relationship between identity shifts and dominance structure.ResultsWe found that the impact of disturbance on temporal turnover depends on soil fertility. The greatest turnover occurred in the most fertile forests immediately after disturbance. There, species gains and losses strongly altered dominance structure leading to high turnover, whereas undisturbed old forests and nutrient‐poor habitats were characterized by stable dominant species even when the majority of species shifted their identity.Main conclusionsOur results suggest that human impacts on temporal biodiversity change vary along environmental gradients. In boreal forests, the fertile habitats have a higher probability than nutrient‐poor sites of changing their composition in response to anthropogenic disturbances. Resource availability and disturbance history may thus influence consequences of temporal turnover for ecosystem functioning.

Trait‐based responses to land use and canopy dynamics modify long‐term diversity changes in forest understories

“…Forest management effects on turnover and diversity were mostly direct, that is, not mediated by management effects on canopy cover and composition, as evidenced by the small difference between management effects in models that included versus excluded canopy variables. The finding of higher turnover in managed forests agrees with previous studies from boreal forests (Brice et al., 2019; Kaarlejärvi et al., 2021) and other biomes (Barlow et al., 2016; Lake et al., 2000) reporting accelerated biodiversity change following human disturbance. Taken together, our results suggest that species richness changes in vascular plant communities in response to forest management do not seem to be driven by a filtering of species based on plant height or leaf traits.…”

Trait-based responses to land use and canopy dynamics modify long-term diversity changes in forest understories

“…not mediated by management effects on canopy cover and composition, as evidenced by the low difference between management effects in models that included vs. excluded canopy variables. The finding of higher turnover in managed forests agrees with previous studies from boreal forests (Brice, Cazelles, Legendre, & Fortin, 2019;Kaarlejärvi, Salemaa, Tonteri, Merilä, & Laine, 2021) and other biomes (Barlow et al, 2016;Lake et al, 2000) reporting accelerated biodiversity change following human disturbance. Taken together, our results suggest that species richness changes in vascular plant communities in response to forest management do not seem to be driven by a filtering of species based on plant height or leaf traits.…”

Climate change reshuffles northern species within their niches

“…While some taxa showed stronger rates of turnover in the northernmost zone (birds and moths, in particular), the direction of such trends varied considerably between zones and taxa (see also refs. 23,24 ). Such asynchronous responses are consistent with species emerging as winners or losers, as climate change can either reduce or impose constraints on species fitness, abundance and distributions 8,[11][12][13]25 .…”

“…In addition, future work is needed to determine whether species' niches have expanded, contracted or shifted altogether 32 , and how such responses may eventually translate into changes in abundance 15 or potentially affect species capacity to respond via plasticity or adaptively to climate change. Finally, the observed changes may partly reflect the effects of land-use change 15,24,33 , which may have more direct impacts on species occurrences and community composition. Our approach uses spatial latent variables and thereby accounts for the spatial autocorrelation that may arise from, for example, environmental covariates left unmeasured 18 .…”