Revisiting the two-layer hypothesis: coexistence of alternative functional rooting strategies in savannas.

ABSTRACT: The two-layer hypothesis of tree-grass coexistence posits that trees and grasses differ in rooting depth, with grasses exploiting soil moisture in shallow layers while trees have exclusive access to deep water. The lack of clear differences in maximum rooting depth between these two functional groups, however, has caused this model to fall out of favor. The alternative model, the demographic bottleneck hypothesis, suggests that trees and grasses occupy overlapping rooting niches, and that stochastic events such as fires and droughts result in episodic tree mortality at various life stages, thus preventing trees from otherwise displacing grasses, at least in mesic savannas. Two potential problems with this view are: 1) we lack data on functional rooting profiles in trees and grasses, and th

SUBMITTER: Holdo RM 

PROVIDER: S-EPMC3741314 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature