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The many forms of thirst : investigating forest constraints in the Cape Floristic Region
Identifying the primary determinants of forest distribution has been a considerable challenge for ecologists. Although focus was traditionally directed towards climatological variables, predictive models showed that suitable forest conditions were far more extensive than the actual forest distributi...
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| Format: | Thesis |
| Language: | English |
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Department of Biological Sciences
2015
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| Summary: | Identifying the primary determinants of forest distribution has been a considerable challenge for ecologists. Although focus was traditionally directed towards climatological variables, predictive models showed that suitable forest conditions were far more extensive than the actual forest distribution. This study investigated the primary constraints of forests in the Cape Floristic Region (CFR), in South Africa. Based on a study by Lehmann et al. (2011) on savanna ecosystems, it was hypothesised that seasonal drought and moisture balance were more likely to limit forest distribution than broader rainfall patterns. The biomes of the CFR were mapped using Mucina & Rutherford’s (2006) vegetation map. Environmental data was extracted from Schulze (2007) and analysed using various statistical methods and the effective rainfall during the wet and dry seasons was examined in relation to vegetation patterns. As a complementary analysis, high resolution spatial data was extracted from the Worldclim database (www.worldclim.org) and run in the program Maximum Entropy. The presence of forest was shown to be constrained by soil moisture deficits in the driest half of the year. However there was considerable overlap of climactic and edaphic conditions across the different biomes. It was suggested that seasonal drought may play an indirect rather than direct role in shaping vegetation type. As the length of the dry season correlated with the length of the dry season, it was determined that seasonal drought may effect vegetation by promoting landscape-shaping fires. These findings have implications for predicting and understanding historical and future ecosystem shifts and their relationship with global and local climate change. |
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