Long‐term monitoring reveals forest tree community change driven by atmospheric sulphate pollution and contemporary climate change

Abstract

Aim Montane environments are sentinels of global change, providing unique opportunities to assess impacts on species diversity. Multiple anthropogenic stressors such as climate change and atmospheric pollution may act concurrently or synergistically in restructuring communities. Thus, a major challenge for conservation is untangling the relative importance of different stressors. Here, we combine long‐term monitoring with multivariate community modelling to estimate the anthropogenic drivers shaping forest tree diversity along an elevational gradient. Location Camels Hump Mountain, Vermont, USA. Methods We used Generalized Dissimilarity Modelling (GDM) to model spatial and temporal turnover in beta diversity along an elevational gradient over a 50‐year period and tested for spatiotemporal shifts in density and elevational distribution of individual species. GDMs were used to predict community turnover as nonlinear functions of changes in elevation, climate and atmospheric pollution. Results We observed significant shifts in elevational range and density of individual species, which contributed to an overall reduction in the elevational gradient in beta diversity through time. GDMs showed the combined effects of sulphate deposition and temperature as drivers of this temporal reduction in beta diversity. Spatiotemporal changes differed among species, with shifts observed both up‐ and downslope. For example, in a reversal of a previous upslope range contraction, red spruce (Picea rubens Sarg.) increased in density and shifted downslope since the 1990s, occupying warmer, drier climates. Main conclusion Our results demonstrate that global change is impacting the stratification of forest tree diversity along elevational gradients, but the responses of individual species are complex and variable in direction. We suggest abiotic drivers may directly impact individual species while also indirectly altering species interactions along elevational gradients. Our approach modelling the drivers of compositional turnover quantifies the rate and amount of change in beta diversity along environmental gradients and serves as a powerful complement to studying species‐specific responses.

From common gardens to candidate genes: exploring local adaptation to climate in red spruce

“…One such species is red spruce ( Picea rubens Sarg.) – a temperate conifer endemic to north‐eastern America with a distribution that spans 13° of latitude, and 800 m of elevation (Verrico et al ., 2019 ), making the species a good candidate for climatically‐driven divergent selection. However, as red spruce colonized its current range from a southern refugium after the Last Glacial Maximum (LGM), it followed a south–north expansion route (T. Capblancq et al ., unpublished) such that the climatic gradients that drive local adaptation strongly covary with neutral population structure and geographic distance.…”

Effects of warming on seed germination of woody species in temperate secondary forests

“…The observed species‐specific responses may have consequences for plant communities in the expected warmer environments (Verrico et al . 2019). Some species may expand their niches to a new habitat and improve competitive capacities in warmer future conditions, while others may be subjected to exclusion or expulsion.…”

Changes in the potential distribution of valuable tree species based on their regeneration in the Neotropical seasonal dry forest of north-western Argentina

“…This result is alarming given that C. multiflorum and P. rhamnoides are the species that define the environmental unit of the Piedmont Forest . Temperature change has been proposed to be the most significant driver of restructuring tree communities by modifying the spatial organization of species (Serra-Diaz et al 2016, Verrico et al 2020, and this may very well be the case in the Piedmont Forest.…”