The Savannas: An integrated synthesis of three major competing paradigms

Abstract

The coexistence between trees and grasses in the savannas is a contentious issue. Al- though necessary scientific efforts have been done, unfortunately such efforts have given rise to contrasting theories and models. This review provides a synthesis of these theories how they influenced our understanding of the savannas over time. The review found that while the equilibrium theory predicts savannas as stable ecosystems regulated by natural mechanisms such as root niche partitioning, such ideas have been disputed in favour of non-equilibrium framework. The latter suggests that savannas are unstable ecosystems largely regulated by stochastic dynamics such as inter annual rainfall variations and episodic environmental shocks such as fire and overgrazing which result in an ecosystem oscillation between grass dominated and woody dominated phases in time and space. On the other hand the disequilibrium paradigm argues that savannas are unnatural ecosystems formed as a result of anthropogenic disturbances such as fire and grazing that buffer the ecosystem from complete domination by either trees or grasses. This review demonstrates that the savannas still lack a unifying theoretical framework. The current one is characterized by conflicting, contradictory, diverging ideas. Such revelations call for a need to develop a unifying theoretical framework for the savannas.