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Biological traits explain bryophyte species distributions and responses to forest fragmentation and climatic variation

Löbel, Swantje, Mair, Louise, Lönnell, Niklas, Schröder, Boris, Snäll, Tord
Thejournal of ecology 2018 v.106 no.4 pp. 1700-1713
Bryophyta, asexual reproduction, biodiversity, broadleaved trees, climate change, climatic factors, competitive exclusion, dead wood, forest ecosystems, forests, habitat destruction, habitat fragmentation, habitats, landscapes, life history, models, prediction, reproductive traits, sexual reproduction, temperature, Sweden
Forest ecosystems have been subjected to intensive exploitation, and on top of these land use‐driven habitat alterations, there is an ongoing and rapid climate change. Understanding why environmental responses differ across species and how differences are mediated by species’ traits is crucial for predicting the complex effects of global change on forest biodiversity. We used (1) single‐species distribution models and (2) multispecies predictive fourth‐corner models of varying complexity to identify critical response traits of dead wood inhabiting bryophytes and to quantify species’ relationships with climatic and forest landscape variation. We hypothesized that reproductive and life‐history traits would be mainly linked with forest connectivity, whereas morphological traits would mostly relate to (micro‐)climatic variation. The inferred trait–environment relationships based on the different fourth‐corner models were consistent. Unexpectedly, reproduction modes were more closely linked to climatic and habitat factors than to forest connectivity. Sexual reproduction was positively related to high temperatures and broadleaf trees, but negatively to high amounts of precipitation. The opposite was true for species which predominantly, or additionally, reproduce asexually. Bryophyte life‐forms were related to both habitat and climatic conditions. The positive relationship of shoot length with both high temperatures and high amounts of precipitation suggested that competitive exclusion is important in determining trailing edges of dead wood inhabiting bryophytes. Synthesis. Differences in physiological tolerances obviously play a much greater role in shaping the distributional pattern of bryophyte species with different reproductive systems than previously thought. Evidence suggests that current geographic ranges were primarily determined by physiological tolerances and competitive abilities. Species’ relationships with forest connectivity were complex and determined by the combination of reproductive traits with other critical species’ properties. Given the different species’ relationships with climatic gradients, and the varying species’ dispersal and competitive capacities, we expect clear changes in metacommunity composition following climate change and an overall decrease in the diversity of dead wood inhabiting bryophytes in Sweden.