Temporal biodiversity change following disturbance varies along an environmental gradient

Aim The 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.
Location Finland Time period Observations 1985-2006, disturbance history
>140 years. Major taxa studied Vascular plants. Methods We
investigated temporal turnover of boreal forest understory 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
fertility gradient. We quantify temporal turnover 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. Results We found that the impact of disturbance on temporal
turnover depends on soil fertility. The greatest turnover occurred in 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 conclusions Our results suggest that human
impacts on temporal biodiversity change vary along environmental
gradients. In boreal forests, the fertile habitats have higher probability
than nutrient-poor sites to change their composition in response to
anthropogenic disturbances. Resource availability and disturbance history
may thus influence consequences of temporal turnover for ecosystem
functioning.