Epsilon Archive for Student Projects

Abstract

Introduction. Climate is a well-known and well-studied abiotic driver of the natural world working through e.g. physiological alterations in species, changes in species’ ranges and growing season, reduction in growth or causing mortality. Besides influencing vegetation zonation, climate is vital for plant functioning such as evapotranspiration, net primary productivity (NPP), nutrient cycling; as well as for vegetation structure, all of which are essential for ecosystem functioning and provisioning of ecosystem services to humans. Biodiversity is an important constituent of optimal ecosystem functioning and it is broadly accepted that diversity of plant functional traits, the characteristics of plants related to growth, dispersal, persistence, is what makes up ecosystem functioning and ecosystem response to environmental factors. Climate is often defined in terms of the mean and variability of atmospheric variables such as temperature and precipitation, which I will be using in my research.
Aims. The aim of my study is to investigate the effect of the Swedish spatial climatic gradient on plant functional diversity. I want to know how temperature and precipitation variation in Sweden affect a) functional richness (FRic; the richness of different plant functional traits within a community), b) species richness (number of species), c) community mean specific leaf area (SLA), d) community mean seed mass and e) community mean canopy height. Community trait means are mean values of functional traits in a given plant community or plot.
Methods. The data I used are species occurrence data (8193 unique species), functional trait data (13 functional traits), temperature, precipitation and land-use data across 6153 plant communities of 5x5 km each. Using them I performed a functional diversity analysis calculating FRic and community trait means, which I later analyzed with linear mixed models in R.
Results. Results for FRic indicate that in areas of high temperatures, the number of functional traits tends to be high, as well as in areas where high % forest cover and high temperatures. Species richness tends to be high in high temperature and precipitation areas, and low in areas with high forest cover and areas with high forest cover and precipitation. Seed mass is on average smaller in areas of increased temperature and precipitation. With high temperatures and % forest cover, seeds also tend to be smaller. Along the climate gradient in areas of higher temperature and precipitation, SLA tends to be larger. Likewise, in areas with more forest cover and higher temperatures, SLA is larger. In areas of high temperatures, canopy height was greater.
Discussion. My results show higher species richness and higher FRic in warmer areas across the present-day climate in Sweden. The functional traits examined (seed mass, SLA and canopy height) are all significantly affected by at least one and often both of the climate drivers. Additionally, as climate is undeniably changing, numerous species distributions and geographical range changes have been documented, as well as species extinctions and ecosystem functioning alterations. This leads to a possible and plausible conclusion that Swedish species and functional diversity will experience consequences of climate change. These changes are likely to have large implications for evolution of new suites of traits, unprecedented changes in ecosystem functioning and species gain in Sweden, as well as potential loss.