Browsing by Author "Peel, Michael John Stephen."

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Recovery, resilience and stability of piospere systems in the Kruger National Park.
(2010) Matchett, Katherine Jean.; Kirkman, Kevin Peter.; Ward, David Mercer.; Peel, Michael John Stephen.; Morris, Craig Duncan.
Water provision is an important tool in the management of savanna ecosystems. Artificial water sources are a potential focus for degradation (biodiversity and loss of ecosystem resilience at a range of spatio-temporal scales), because they alter plant-animal interactions and soil function and stability, through the creation of piospheres. This study was undertaken as part of a drive by the Kruger National Park (KNP) to enable managers to integrate artificial waterhole management (e.g. waterhole closure or rotation) when setting goals for heterogeneity and biodiversity conservation in the park. The over-arching goal was to quantify the relationship between water provision and different attributes of heterogeneity, as part of a broader initiative to place water provision and piospheres within an ecosystem threshold framework. Herbivore utilisation gradients (piospheres) around artificial waterholes in the KNP, described in 1990, were resurveyed in 2006-2007, against a backdrop of waterhole closure in the KNP, to contribute to an understanding of the factors governing recovery and resilience in grazing systems. The responses of the plant community and soil parameters to a relaxation of herbivore utilisation pressure around closed waterholes (recovering piospheres) were examined, as were changes in the same parameters at sites that have remained open (active piospheres). These ecosystem properties were considered in relation to structural and functional ecosystem thresholds, and the piospheres surveyed incorporated a range of rainfall and edaphic gradients in the KNP. Herbaceous basal cover and soil infiltration capacity both increased significantly between 1990 and 2006/7, regardless of waterhole status. This was linked to higher rainfall in 2006/7, compared to 1990. The only vegetation variables to respond consistently to distance from water were the remote-sensed Normalized Difference Vegetation Index (NDVI) and herbaceous species composition. NDVI increased with distance from water, and annual grasses and forbs were most abundant close to water. Perennial, disturbance-sensitive climax species increased in abundance further from water. Soil analyses (N, P, pH, organic matter, and texture) and field measurements (infiltration, compaction) revealed no systematic piosphere patterns. Waterhole closure did not result in soil or vegetation recovery, but piosphere intermittency and the increases of basal cover and infiltration rate indicated that ecosystem resilience has not been compromised vii by long-term artificial water provision in the KNP. This study has shown that the traditional piosphere model is of limited use in sub-humid savanna ecosystems like the KNP during above-average rainfall periods.
Towards a predictive understanding of savanna vegetation dynamics in the eastern Lowveld of South Africa : with implications for effective management.
(2005) Peel, Michael John Stephen.; Zacharias, Peter John Kenneth.; Biggs, Chara.
The purpose of this study was to develop and test a predictive understanding of the vegetation dynamics of the Lowveld of South Africa (30°35'E to 30°40'E and 24°00'S to 25°00'S). The study covered about 5000 km2 in Adjacent Private Protected Areas (APPA) adjoining the Kruger National Park (KNP). Data gathering (800 sites; 23 properties) commenced in 1989 and those recorded up to 2004 are reported here. The value, both ecological and economic, of the wildlife and tourism industry dependent on this savanna region is discussed in both historical and current perspectives. A range of land-use objectives and anthropogenic interventions were exposed. The properties ranged in size from 30 to 800 km2 and formed an effective and extensive manipulative experiment for investigating interaction of bush density, animal stocking, use of fire and landscape-scale processes. The first descriptive classification (at 1:250 000) of the area was developed using Inverse Distance Weighted interpolations. This confirms similar landscape/vegetation patterns in the KNP and Mocambique. The current mode of determining stocking density or carrying capacity was interrogated and indices suitable for complex multi-species systems developed. This was done in the context of equilibrial/disequilibrial paradigms. Application of the original indices resulted in drought-related declines in animal biomass of 4000 kg km2 over 20 years due to overestimation of carrying capacity. The model proposed here uses rainfall, animal type, biomass and vegetation parameters to determine stocking density for both coarse (regional) and ranch-specific scales. Principal driving determinants (rainfall, geology, soil type, tree density canopy cover, animal numbers, feeding classes and fire) of vegetation structure and their influence on the herbaceous layer were investigated. Groupings on ecological potential showed 'high' potential areas are less sensitive to animal impact than those classified as 'low' potential. Sustainability, embedded in a forward-looking component viz. Strategic Adaptive Management (SAM) with well-articulated endpoints viz. Thresholds of Potential Concern (TPCs) was used to study fluctuations in animal populations with Connochaetes taurinus (Blue wildebeest) as the case study. The TPC approach provides strong pointers for proactive management aimed at maintaining the system within bands defined by TPCs supporting operationally practical and periodically reviewed objectives.