Magnus Lindh: Evolution of plants in a water limited environment

Plants depend critically on water for their photosynthesis. Water deficit will initially lead to lower plant growth rate, then to hydraulic failure, and ultimately to death. Plants have evolved complex strategies to withstand long periods of drought such as a high wood density, a plastic reproduction time, and deep roots. Understanding plant responses to drought is important in forestry as well as in climate modelling.
We devised an evolutionary model with plants competing for water, coupled with a dynamic soil water model including precipitation, evaporation and transpiration. Specifically, we focused on how the plants birth and death rates are influenced by the functional response of soil water content. We also investigated spatial effects with an evolutionary cellular automaton.
Our results suggest that plants have evolved strategies that are not maximizing plant density or soil water content. We also find that gradients in soil water content could promote plant diversity, but this depends critically on the functional response of soil water content.