Plant communities of Kilombero wetlands in Tanzania: structure, invasion and cattle grazing
| dc.contributor.author | Macrice ,Andrew Samora | |
| dc.date.accessioned | 2024-06-04T09:49:44Z | |
| dc.date.available | 2024-06-04T09:49:44Z | |
| dc.date.issued | 2014 | |
| dc.description | PhD Thesis | |
| dc.description.abstract | Wetlands arc dynamic ecosystems appreciated worldwide for supporting biodiversity. sustaining livelihoods and climate change mitigation and adaptation. However, the increased degradation of wetlands and changes in their plant species composition and diversity due to anthropogenic disturbances, alterations of natural environmental conditions and plant invasions is an increasing global concern. Thus, to restore the species composition and diversity and protect existing plant communities in wetlands, timely understanding of important factors that regulate and maintain plant community structure as well as how communities become vulnerable to alien plant invasions is essential. Therefore, using herbaceous vegetation, studies were conducted to investigate key drivers of spatial heterogeneity in plant species composition, richness and diversity, to examine invasibility of plant communities and to assess how large domestic herbivores (cattle) select foraging sites within Kilombero Valley Floodplain wetland. Tanzania. The results show that patterns of spatial variation in plant species composition. richness and diversity were associated with natural environmental conditions, human disturbance and spatial position variables. In particular, variation in species composition of all plant species and functional groups (graminoids. forbs and shrubs) were best explained by natural environmental conditions (total organic carbon, elevation and distance from Kilombero River) and human disturbance (cow dung density and distance to cattle holding pen area (kraal)). Total species richness and the richness of functional groups decreased with the increase in distance from the river, suggesting that, annual flooding is important in the study site. Grazing reduced total species diversity and the diversity of graminoids possibly through changing local nutrient balance. Most shrub species were found on relatively high ixelevations, and shrub richness related negatively to total organic carbon suggesting that shnibs are less tolerant to inundation and high levels of soil fertility. Plant community properties such as species evenness and bioinass have rarely been used in biological invasion studies. Interestingly, these properties promoted community resistance against invasion of alien plant species Echinochloa colona through reducing its abundance. Moreover, it appears that grazing intensity creates gaps which are occupied by fast growing opportunistic species such as £. culona which may then alter the structure of native plant communities. Thus, disturbed areas with rich environmental resources (e.g. light. water, nutrients) and low plant biomass and evenness of native species are hot spots for plant invasions. Cattle selected foraging sites using a nesting feeding choice model. On a larger scale. cattle selected patches with low diversity, at high elevations, and at longer distances from agricultural fields. Moreover, cattle selected patches with a higher abundance of palatable plant species with high biomass at large scale. It appears that once the large scale patch is selected, cattle tend to graze on small patches with high plant species richness and moderate biomass to achieve nutritional balance and maximize energy gains. In conclusion, maintenance of plant species richness and biomass together with optimal stocking rates could improve cattle production and rangeland quality. Since natural environmental conditions and human disturbance variables shapes plant community structure. intensification of human activities (e.g. overgrazing by livestock) and alterations of natural environmental conditions (e.g. through water diversion and drainage) should be discouraged. Finally, improved management strategies including increasing biomass and evenness of native species together with reduction in grazing pressure may reduce community vulnerability to alien plant invasions and improve biodiversity conservation. | |
| dc.identifier.uri | https://www.suaire.sua.ac.tz/handle/123456789/6220 | |
| dc.language.iso | en | |
| dc.publisher | Sokoine University of Agriculture | |
| dc.subject | Plant communities | |
| dc.subject | Kilombero wetlands | |
| dc.subject | Cattle grazing | |
| dc.subject | Structure | |
| dc.subject | Invasion | |
| dc.title | Plant communities of Kilombero wetlands in Tanzania: structure, invasion and cattle grazing | |
| dc.type | Thesis |