Plants grown in competition produce more leaf, stem, and root tissue than those grown alone. The relatively large production of tissues may be explained by the competitive advantage conferred not only by increasing resource uptake, but by pre-empting resource uptake by neighboring plants. The growth strategy that maximizes the resource uptake and fitness of a plant is known as the evolutionarily stable strategy (ESS). Non-game theoretic models do not account for plant competition and under-predict growth. Game theoretic models, however, predict more realistic ESSs of plants growing in natural settings (i.e. with neighbors).
Existing game theoretic models of plant growth include competition for nitrogen and carbon, but ignore soil moisture. However, precipitation patterns are expected to change over the next century for most regions of the world as air temperature warms. In light of this, it is critical to understand how plant growth and its dependent processes will adjust to changes in precipitation. Here, we present a game theoretic model of plant competition for nitrogen, carbon, and soil moisture which describes the growth of roots, leaves, and stems at the individual level.
Results/Conclusions
Preliminary results from our model predict increasing root production with decreasing nitrogen availability; this effect is greatest when soil moisture is low. Additionally, root production peaks at moderate soil moistures, with extreme soil moisture values inhibiting growth. Leaf production is predicted to increase with soil moisture, leveling off as soil moisture approaches 100%. Nitrogen limitation caused leaf production to decrease, especially when water was also limiting. Generally, low soil moisture exacerbates the effects of nitrogen limitation on all root and leaf tissues.
By modeling ESSs of individual tissue production, plant functional type (PFT) becomes an emergent property of the model. Our model simulates 1) the allocation of root, leaf, and stem tissues; 2) individual-level responses to gradients of soil moisture and nitrogen availability; and 3) trends in total NPP that are similar to those observed in FLUXNET and MODIS data when given environmental parameters for the global biomes. We believe that this model can be used to increase the realism of climate models.