Abstract
Abstract. The global geographic distribution of biodiversity and biomes is determined by species-specific physiological tolerances to climatic constraints. Current vegetation models employ empirical bioclimatic relationships to predict present-day vegetation patterns and to forecast biodiversity changes and biome shifts under climatic change. In this paper, we consider trade-offs in plant functioning and their responses under climatic changes to forecast and explain changes in plant functional richness and shifts in biome geographic distributions. The Jena Diversity model (JeDi) simulates plant survival according to essential plant functional trade-offs, including ecophysiological processes such as water uptake, photosynthesis, allocation, reproduction and phenology. We use JeDi to quantify changes in plant functional richness and biome shifts between present-day and a range of possible future climates from two SRES emission scenarios (A2 and B1) and seven global climate models using metrics of plant functional richness and functional identity. Our results show (i) a significant loss of plant functional richness in the tropics, (ii) an increase in plant functional richness at mid and high latitudes, and (iii) a pole-ward shift of biomes. While these results are consistent with the findings of empirical approaches, we are able to explain them in terms of the plant functional trade-offs involved in the allocation, metabolic and reproduction strategies of plants. We conclude that general aspects of plant physiological tolerances can be derived from functional trade-offs, which may provide a useful process- and trait-based alternative to bioclimatic relationships. Such a mechanistic approach may be particularly relevant when addressing vegetation responses to climatic changes that encounter novel combinations of climate parameters that do not exist under contemporary climate.
Highlights
The Earth’s climate determines the geographic distribution of vegetation physiognomy and biomes through speciesspecific physiological tolerances to temperature, water availability and length of the growing season (Woodward, 1987)
Reu et al.: Biodiversity and biomes under climatic change range that can be tolerated by that species, (ii) there is no guarantee that predictions based on these correlation structures are reliable, especially where future climates have no analogues in current climate (Williams et al, 2007), and (iii) it is often impossible to disentangle what aspects of the climate are driving biodiversity change and biome shift (Willis et al, 2007; Carrara and Vazquez, 2010)
3.2 Biome shift under climatic change In Jena Diversity model (JeDi), biome shifts are determined by changes in the functional identity (FI) of a grid cell that are large enough to shift this grid cell in the trait value space such that it becomes closer to the centre of another biome cluster
Summary
The Earth’s climate determines the geographic distribution of vegetation physiognomy and biomes through speciesspecific physiological tolerances to temperature, water availability and length of the growing season (Woodward, 1987). One widely-used approach to predict the global distribution of species richness and biomes is to derive empirical relationships between the climate and the number of species or the presence (dominance) of characteristic plant functional types (PFTs) (Holdridge, 1947; Whittaker, 1975; Box, 1981; Barthlott et al, 1996; Kreft and Jetz, 2007) These relationships are applied to forecast biodiversity changes and biome shifts under various climate change scenarios (Thuiller, 2003; Scholze et al, 2006; Thomas et al, 2008; Sommer et al, 2010). Reu et al.: Biodiversity and biomes under climatic change range that can be tolerated by that species, (ii) there is no guarantee that predictions based on these correlation structures are reliable, especially where future climates have no analogues in current climate (Williams et al, 2007), and (iii) it is often impossible to disentangle what aspects of the climate (i.e., temperature or precipitation, climatic mean or variability) are driving biodiversity change and biome shift (Willis et al, 2007; Carrara and Vazquez, 2010)
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