Interaction of Fire and Rainfall Variability on Tree Structure and Carbon Fluxes in Savannas: Application of the Flames Model
From an Australian perspective, the analysis by Sankaran et al. (2005) of the interactive effects of precipitation and disturbance on vegetation structure of African savannas raises a range of questions. These authors concluded on the basis of data from savannas across Africa that below 650 mm mean annual precipitation (MAP), African savannas were stable, in that rainfall constrained woody cover below about 70%, which allows the persistence of grass. For MAPs above this value, and in the absence of fire and other disturbances, woody cover could increase to levels that exclude grass, and thus savannas defined by the coexistence of trees and grass were not stable. Both above and below 650 mm mean annual precipitation (MAP), disturbance by fire and herbivory and stresses from edaphic conditions could and mostly did lead to woody cover being below the climatic optimum.