Browsing by Author "Moe, S. R."

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Invasion of the cosmopolitan species Echinochloa colona into herbaceous vegetation of a tropical wetland system
(The Ecological Society of Japan 2014, 2004) Andrew, S. M.; Totland, Q.; Moe, S. R.
The negative effects of alien plant species on ecosystem structure and functions are increasingly recognised, and efforts to control these species are vital to restore degraded ecosystems and preserve biodiver- sity. However, we lack a full understanding of factors that determine alien species invasions along spatial gradients in herbaceous vegetation of tropical systems. We therefore examined the effects of community prop- erties, environmental variables and human-related dis- turbance factors on the invasion of the alien grass Echinochloa colona (L.) Link at small- and large scales in the Kilombero Valley wetland, Tanzania. Generalized additive mixed models showed that E. colona abundance on a small scale was negatively related to above-ground biomass and evenness of resident species, whereas E. colona abundance was positively related to grazing intensity. On a large scale, biomass (negatively related to E. colona abundance) and distance to river (positive) were important in explaining E. colona abundance. These findings support the assertion that different fac- tors may contribute to the invasion of alien plant species at different spatial scales, as also reported in many temperate systems. Overall, our results show that suc- cessful invasion of alien species is a function of plant community properties, human-related disturbance and favourable environmental conditions. Effective man- agement strategies should consider mitigations that can increase the biomass and evenness of native species and a reduction of grazing pressure to restore the wetland and conserve biodiversity.
Spatial variation in plant species richness and diversity along human disturbance and environmental gradients in a tropical wetland
(Springer Science+Business Media Dordrecht 2014, 2014-11) Andrew, S. M.; Totland, Q.; Moe, S. R.
Human disturbance, natural environmen- tal conditions and seed dispersal are often inferred as important drivers of plant community richness and diversity in wetland ecosystems. However, plant functional groups within a plant community have different environmental requirements and may respond differently to human disturbance. Therefore, the understanding of the relative importance of these variables in determining community and functional groups richness and diversity is important for improved management and wise use of wetland resources. We collected data on vegetation and envi- ronmental conditions, human disturbance and seed dispersal from 60 plots of 20 9 50 m, to identify variables that potentially affect total species richness and Shannon-Wiener diversity of the grassland plant community at the Kilombero Valley wetland, Tanza- nia. We further tested whether important predictor variables for species richness and Shannon-Wiener diversity differ among graminoid, forb and shrub functional groups. Overall, our results suggest that environmental conditions, human disturbance and seed dispersal determine spatial variation in species rich- ness and Shannon-Wiener diversity of the grassland vegetation. The total richness and Shannon-Wiener diversity and the richness of shrubs decreased with distance from the Kilombero River, whereas the total Shannon-Wiener diversity and the Shannon-Wiener diversity of graminoids decreased with the increase in grazing intensity. Shrub species richness was related to the spatial position of plots and decreased with total organic carbon of soil. Current increase in human disturbances through cattle husbandry and changes in natural environmental conditions (e.g. through water diversion and drainage) should be discouraged in order to restore and sustain biodiversity of the Kilombero wetland.
Species composition and functional structure of herbaceous vegetation in a tropical wetland system
(Springer Science+Business Media B.V., 2012) Andrew, S. M.; Moe, S. R.; Totland, Q.; Munishi, P. K. T.
Understanding driving factors of spatial heterogeneity in plant species com- position and functional structure is a key step towards wetland ecosystems restoration and biodiversity conservation. We surveyed 60 randomly selected plots of 20 9 50 m each and collected 12 explanatory variables to understand potential impacts of natural environ- mental conditions, human disturbance and spatial position of plots variables on plant functional groups (PFGs) and species composition within grasslands of the Kilombero Valley Floodplain wetland, Tanzania. Ordination analyses were used to identify important vegetation gradients and establish significant natural environmental conditions, human disturbance and spatial position of plots correlates. Partial redundancy analysis (RDA) and partial canonical correspondence analysis (CCA) were used to determine the individual and shared effects of these three sets of explanatory variables on the PFGs and species composition, respectively. In total, 115 plant species, including 22 weed and 3 invasive species, and five PFGs were registered. Annual graminoid was the most abundant, whereas perennial forb the least abundant PFG with 50 and 1 % relative covers, respectively. Overall, spatial position, altitude, total organic carbon, cow dung, distance to the river and distance to kraal (cattle enclosure near human settlement commonly made of wood materials for animal protection) were important descriptors of both PFGs and overall species composition. Separate CCA of only weed and invasive plant species showed that some species, particularly the invasive Polygala paniculata were strongly associated with cow dung, indicating that present increase in cattle numbers may result in future problems associated with this species. Intensification of human activities and alteration of natural environmental conditions associated with these factors should be discouraged to maintain plant species composition and functional structure for wetland restoration and sustainable biodiversity conservation.