This study is part of the OPTIMASS, an interdisciplinary project funded within the SPACES-programme of the BMBF with the aim of implementing sustainable management of savanna ecosystems.
There is yet no consensus about the main mechanisms that drive shrub encroachment in southern African savannas, and thus recommendations regarding management are difficult to make. Much work has been done on effects of fire, grazing, water and nutrient availability on rangeland productivity but the role of climate change, namely changes in CO2 concentrations, temperature, and rainfall and their potential interaction with manageable factors (grazing, fire) is not understood. A unique feature of tree-grass interactions in savannas is the fact that the two life forms are characterized by two different photosynthetic pathways (C4 grasses vs. C3 trees and shrubs). Therefore, CO2 should play a key role in shrub encroachment, but experimental evidence is missing in the field and rare in common gardens, and interactions between CO2 and factors amenable to manipulation (i.e. adaptive management of fire, grazing, and nutrients) are unknown.