Simulated geographic variations of plant species richness, evenness and abundance using climatic constraints on plant functional diversity
Among the most pronounced large-scale geographic patterns of plant biodiversity are the increase in plant species richness towards the tropics, a more even distribution of the relative abundances of plant species in the tropics, and a nearly log-normal relative abundance distribution. Here we use an individual-based plant diversity model that relates climatic constraints to feasible plant growth strategies to show that all three basic diversity patterns can be predicted merely from the climatic constraints acting upon plant ecophysiological trade-offs. Our model predicts that towards objectively 'harsher' environments, the range of feasible growth strategies resulting in reproductive plants is reduced, thus resulting in lower functional plant species richness. The reduction of evenness is attributed to a more rapid decline in productivity from the most productive to less productive plant growth strategies since the particular setup of the strategy becomes more important in maintaining high productivity in harsher environments. This approach is also able to reproduce the increase in the deviation from a log-normal distribution towards more evenly distributed communities of the tropics. Our results imply that these general biodiversity relationships can be understood primarily by considering the climatic constraints on plant ecophysiological trade-offs.
- Environmental Research Letters, 4: 014007.
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Figure 1: Geographic patterns of the richness of plant growth strategies simulated with a generic, ecophysiology-based plant model forced with present-day climatic conditions. Richness is expressed as a percentage of the maximum value of species richness found in any locality in the model.
Figure 2: Simulated relative abundance versus proxy species rank for four classes of proxy species richness D. On the x-axis, proxy species are ranked according to their abundance, which in turn is plotted on the y-axis.
Figure 3: Simulated relative abundance distributions of plant growth strategies for four classes of proxy species richness D. The dotted lines show two log-normal distributions that closely match the respective relative abundance distributions for comparison.
Figure 4: Simulated relative productivity versus proxy species ranked by their productivity for four classes of proxy species richness D. Productivity is expressed relative to the maximum productivity of all proxy species at a given grid point and averaged over all grid points within a given class.