Abstract
Arid and semiarid savannas are characterized by the coexistence of trees and grasses in water
limited conditions. As in all dry lands, also in these savannas rainfall is highly intermittent. In this work, we
develop and use a simple implicit-space model to conceptually explore how precipitation intermittency
influences tree-grass competition and savanna occurrence. The model explicitly includes soil moisture
dynamics, and life-stage structure of the trees. Assuming that water availability affects the ability of both
plant functional types to colonize new space and that grasses outcompete tree seedlings, the model is able
to predict the expected sequence of grassland, savanna, and forest along a range of mean annual rainfall. In
addition, rainfall intermittency allows for tree-grass coexistence at lower mean annual rainfall values than
for constant precipitation. Comparison with observations indicates that the model, albeit very simple, is
able to capture some of the essential dynamical processes of natural savannas. The results suggest that precipitation
intermittency affects savanna occurrence and structure, indicating a new point of view for reanalyzing
observational data from the literature.
limited conditions. As in all dry lands, also in these savannas rainfall is highly intermittent. In this work, we
develop and use a simple implicit-space model to conceptually explore how precipitation intermittency
influences tree-grass competition and savanna occurrence. The model explicitly includes soil moisture
dynamics, and life-stage structure of the trees. Assuming that water availability affects the ability of both
plant functional types to colonize new space and that grasses outcompete tree seedlings, the model is able
to predict the expected sequence of grassland, savanna, and forest along a range of mean annual rainfall. In
addition, rainfall intermittency allows for tree-grass coexistence at lower mean annual rainfall values than
for constant precipitation. Comparison with observations indicates that the model, albeit very simple, is
able to capture some of the essential dynamical processes of natural savannas. The results suggest that precipitation
intermittency affects savanna occurrence and structure, indicating a new point of view for reanalyzing
observational data from the literature.
| Original language | English |
|---|---|
| Pages (from-to) | 169–181 |
| Number of pages | 13 |
| Journal | Water Resources Research |
| Volume | 51 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 8 Jan 2015 |
Keywords
- savanna
- tree life-stage structure
- water competition
- precipitation
- implicit-space models