Modelling Responses of Savanna Grass Species to Water Supply and Competition

J. Segarra, J. Raventós, M. Acevedo, and J.F. Silva (USA)


soil moisture, niche differentiation, fire, phenology, plant architecture


Neotropical savannas are one of the largest biomes in the world. These ecosystems are composed basically of trees and codominant grasses. In this paper we simulate the effect of soil moisture on the growth of three different phenological and architectural savanna grasses when these species grow alone and in pairs. Rainfall simulation is performed based on historical data. We also examined the effect of soil moisture potential decrease to 20% of the usual soil moisture. The results show that when growing alone Andropogon semiberbis (A), a late erect species, is the one most affected by this soil moisture decrease. When growing under competition we found a clear relation between phenology and competition ability of these grasses. The late species (A) is the best competitor, and displays a larger decrease in the number of shoots than the other two species Elionurus adustus (E) and Leptocoryphium lanatum (L), and is less affected by these two other species. The contrary is true for the precocious species (L). There seems to be a trade off between the ability of competition and the ability to withstand a decrease of soil moisture of these codominant grass species. This trade off could be a key point explaining the coexistence of these three different phenological and architectural savanna grasses.

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