RCR / Projects / A3 Crop Science

A3 - Crop science & Rangeland Ecology


Vulnerability and Resilience of Rangeland Vegetation as Affected by Livestock Management, Soils and Climate

Research Areas:
Crop and Grassland Science, Rangeland Ecology

Principal Investigator:
Prof. Dr. Frank Ewert

In collaboration with several research groups from the Universities of Bonn and Cologne, the INRES Crop Science works in the DFG-funded collaboration research project (Forschergruppe) entitled "Resilience, Collapse and Reorganisation in Social-Ecological Systems of East- and South Africa's Savannahs". The project starts on 1st March 2010.

Our work encompasses the sub-project "Vulnerability and Resilience of Rangeland Vegetation as Affected by Livestock Management, Soils and Climate". In the project we aim to analyse and model changes in rangeland vegetation, with specific emphasis on its resilience and vulnerability as affected by livestock management and environmental conditions. The work will focus on South African savannah and grassland biomes and their system shifts to alternative states under different types of range management.

The vegetation of East and South African savannahs has been shaped by the complex interaction of geo-biophysical processes and human impact. For both regions a controversial discussion in ongoing, as to whether massive degradation threatens the sustainability of livelihoods in these regions. Rangeland vegetation (grassland and savannah used for grazing cattle) its resilience and vulnerability is mainly affected by environmental conditions (soil and climate) and by livestock management. Extent and interaction of these drivers causes or prevents shifts towards unfavourable degraded or bush encroached system states which are not well understood. These states, where either total ecosystem productivity is very low, or where grasses have been largely replaced by inedible shrubs, have profound impacts on local livelihoods that are strongly dependent of rangelands for their livestock production.

Our work links closely to investigations on soil vulnerability and land management strategies by the Soil Science group at the University of Bonn for the same regions. Effects of different livestock systems and associated management factors on rangeland vegetation composition and production will be studied. These factors include type and density of livestock, grazing intensity and timing, and other forms of vegetation management such as wood harvesting for charcoal, or measures to control bush encroachment. Specific attention is given to soil-vegetation interactions to better understand changes in rangeland vegetation as determined by livestock management, soil characteristics and climate, as well as the feedback effects of vegetation change on soil properties. Interactions between these key drivers of vegetation change (disturbances, soil resource dynamics, and stochastic rainfall) and their effects on vegetation structure and production will be studied in multi-factorial natural experiments, and modelled with a dynamic vegetation/grassland model.

Our research areas are arranged along a gradient of aridity and contrasting tenure systems with different range management practices being considered. We will apply the concept of plant functional types to classify plant species to support the analysis and modelling of multi-species systems. Plant production, its intra- and interseasonal variability, and the ability of plant production to recover from disturbances will be used as indicators to assess rangeland resilience as affected by land management. Using the vegetation model we will explore potential thresholds to system shifts for the indicators considered and to assess the impacts of different management strategies on the indicators.