Root dynamics influence tree–grass coexistence in an Australian savanna
Article first published online: 27 MAR 2012
© 2012 The Authors. Austral Ecology © 2012 Ecological Society of Australia
Volume 38, Issue 1, pages 66–75, February 2013
How to Cite
FEBRUARY, E. C., COOK, G. D. and RICHARDS, A. E. (2013), Root dynamics influence tree–grass coexistence in an Australian savanna. Austral Ecology, 38: 66–75. doi: 10.1111/j.1442-9993.2012.02376.x
- Issue published online: 23 JAN 2013
- Article first published online: 27 MAR 2012
- Accepted for publication February 2012.
- root biomass;
- root decomposition;
- rooting depth;
- soil carbon;
- tree grass coexistence;
Both resource and disturbance controls have been invoked to explain tree persistence among grasses in savannas. Here we determine the extent to which competition for available resources restricts the rooting depth of both grasses and trees, and how this may influence nutrient cycling under an infrequently burned savanna near Darwin, Australia. We sampled fine roots <2 mm in diameter from 24 soil pits under perennial as well as annual grasses and three levels of canopy cover. The relative proportion of C3 (trees) and C4 (grasses) derived carbon in a sample was determined using mass balance calculations. Our results show that regardless of the type of grass both tree and grass roots are concentrated in the top 20 cm of the soil. While trees have greater root production and contribute more fine root biomass grass roots contribute a disproportional amount of nitrogen and carbon to the soil relative to total root biomass. We postulate that grasses maintain soil nutrient pools and provide biomass for regular fires that prevent forest trees from establishing while savanna trees, are important for increasing soil N content, cycling and mineralization rates. We put forward our ideas as a hypothesis of resource-regulated tree–grass coexistence in tropical savannas.