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Grass invasion in urban lowland fynbos fragments on the Cape Flats : does nutrient addition play a role?
Invasion by exotic grasses is a major threat to natural ecosystems in many parts of the world. On the Cape Flats in Cape Town, grasses were observed to be invading lowland fynbos fragments which are a high priority for conservation. The observation in other parts of the world that nutrient additions...
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| Format: | Thesis |
| Language: | English |
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Department of Biological Sciences
2017
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| Summary: | Invasion by exotic grasses is a major threat to natural ecosystems in many parts of the world. On the Cape Flats in Cape Town, grasses were observed to be invading lowland fynbos fragments which are a high priority for conservation. The observation in other parts of the world that nutrient additions from deposition of airborne pollutants were responsible for increased dominance of grass in natural ecosystems led us to test whether this was the case on the Cape flats. Phytometers were used to gauge the favourability for growth of soils from urban sites compared to those from rural control sites. An attempt was also made to demonstrate the negative effects of grass invasion on seedling establishment and diversity of native species by removal of grass cover and addition of smoke water. Phytometer results were inconclusive, but soil from city sites generally had higher total N than control sites for comparable amounts of organic matter, suggesting that N addition may be occurring. Total seedling emergence was significantly increased by removal of grass cover (p<0.001) and smoke water addition (p<0.05). The implications of our results for conservation of urban fynbos fragments are discussed and further, more detailed investigation of this topic is recommended. |
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