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Investigating the life history strategy of an African savanna tree, Sclerocarya birrea subsp. caffra (marula)
| Content Provider | Semantic Scholar |
|---|---|
| Author | Helm, Chantal Vinisia |
| Copyright Year | 2011 |
| Abstract | Lack of understanding of the life history attributes and responses of savanna woody plants to disturbances, as well as the observation of unstable population structures in a keystone, savanna tree, Sclerocarya birrea subsp. caffra (marula), prompted this study. This study employed a combination of empirical, experimental and model formulation techniques, aimed at achieving its ultimate purpose of understanding the life history strategy of marula in the face of disturbance. Four main population structures were identified for marula in the low altitude savannas of South Africa: 1) adult dominated, 2) juvenile dominated, 3) with a “missing size class” and 4) stable (negative J-shaped). Spatial variability in structure indicated different drivers affecting different populations. High annual mortality rates of up to 4.6% in adult trees, no recruitment out of the fire trap and little regeneration were observed in the Kruger National Park (KNP) between 2001 and 2010, and consequently even greater instability in the structure of these populations already observed earlier in the decade. Growth rates of saplings between 2 and 8 m in height and 2 and 30 cm in stem diameter in the field were monitored between 2007 and 2010. Annual growth rates of up to 11 mm in diameter and up to 22 cm in height were observed. Annual relative growth rates ranged between 1.9 and 4.8% across sites. Growth rates were positively linked with rainfall and plant size. Growth rates, biomass allocation patterns, as well as storage and defence allocation in 3 to 28 month old marula seedlings were assessed under glasshouse conditions. Relative growth rates were highest directly after germination (20%), but did not exceed 5% thereafter. Allocation to roots (already 65% of the overall biomass at 3 months of age and >80% when older) was high regardless of soil type or provenance. Provenance affected height gain, and plants germinating from seeds collected at higher rainfall sites had faster height growth rates than those from seeds collected at lower |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://wiredspace.wits.ac.za/bitstream/handle/10539/10808/CV%20Helm%20PhD%20Abstract%20for%20final%20submission.pdf?sequence=2 |
| Alternate Webpage(s) | https://globalrangelands.org/sites/globalrangelands.org/files/dlio/38000/helm.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
