Human communities from the Okavango Delta benefit from the services and goods provided by the wetland ecosystem through its riparian vegetation. These include food and timber products used for the construction of shel...Human communities from the Okavango Delta benefit from the services and goods provided by the wetland ecosystem through its riparian vegetation. These include food and timber products used for the construction of shelter and canoes. Despite the importance of riparian tree species in the Delta, their regeneration structure is currently unknown. For riparian trees to be managed sustainably, information on the current regeneration status of the trees under different land uses is needed. The Moremi game reserve (protected area) and Seronga (communal area) were selected for this study on the regeneration of riparian tree species of Croton megalobotrys Müll. Arg, Philenoptera violacea (Klotzsch) Schrire, Senegalia nigrescens (Acacia nigrescens) Oliv and Diospyros mespiliformis Hochst. ex A. Dc. The height of each individual tree was estimated in randomly selected 30 plots (15 from each site) of 20 × 50 m for assignment to five regeneration classes: 0-0.5, 0.5-1, 1-2, 2-4 and >4 m. Linear regression was used to infer regeneration status of each species. An independent-sample Student’s t test was used to determine any significance differences in seedling density/ha and sapling density/ha between different sites at p < 0.05. Diospyros mespiliformis populations had an unstable regeneration structure in both sites, while P. violacea regeneration was stable regardless of land-use type. Croton megalobotrys and S. nigrescens had an unstable regeneration pattern in Seronga, while in Moremi it was stable; thus, the regeneration structure of C. megalobotrys and S. nigrescens is affected by land-use. This result implies that intervention is needed to conserve the two species in Seronga where the current land-use appears to be incompatible with regeneration; D. mespiliformis also needs to be conserved in both Moremi and Seronga.展开更多
Introduction:Understanding the environmental factors that influence riparian vegetation community composition and distribution is important for understanding wetland ecosystem functioning.This understanding can furthe...Introduction:Understanding the environmental factors that influence riparian vegetation community composition and distribution is important for understanding wetland ecosystem functioning.This understanding can further serve to inform policy aimed at conserving wetlands such as the Okavango Delta.In the Okavango Delta,information on the influence of distance from surface water on vegetation community composition and structure is limited.The objective of this study was to determine the relationship between distance from surface water and riparian plant communities at different sites in the Okavango Delta.Methods:Vegetation sampling was conducted in four sites in 20 m×10 m belted plots placed perpendicular to the river bank at 0–10 m,10–20 m,20–30 m,30–40 m,and 40–50 m distance classes.At each site,10–15 plots were sampled at each distance class.Basal area,species richness,cover,and plant diversity were determined for each plot.Indicator species analysis was used to determine the characteristic species at each distance class.One-way analysis of variance and Tukey post hoc analyses were used to compare species diversity,richness,cover,and basal area between distance classes.Generalized linear mixed(GLM)model was used to test for the overall impact of site and distance on each plant parameter.Results:Mean species richness was significantly(p<0.05)higher at 0–10 m than at 20–30 m,30–40 m,and 40–50 m in Boro.There was no significant difference within other sites.Mean species diversity also varied significantly(p<0.05)in Boro where it was higher at 0–10 m and 10–20 m than at 30–40 m.Mean basal area differed significantly within Jao and Upper Panhandle.In Jao,it was higher(p<0.05)at 0–10 m than at other distance classes.Mean percentage canopy cover differed significantly within all sites.In addition to this,plant species composition also changed along distance from surface water within each site.From GLM analysis,both distance and site significantly(p<0.05)influenced diversity and basal area.Species richness and cover were significantly(p<0.05)influenced by site only.Conclusion:Distance from surface water and site are important determinants of riparian plant dynamics in the Okavango Delta.展开更多
基金supported by German Federal Ministry for Education and Research
文摘Human communities from the Okavango Delta benefit from the services and goods provided by the wetland ecosystem through its riparian vegetation. These include food and timber products used for the construction of shelter and canoes. Despite the importance of riparian tree species in the Delta, their regeneration structure is currently unknown. For riparian trees to be managed sustainably, information on the current regeneration status of the trees under different land uses is needed. The Moremi game reserve (protected area) and Seronga (communal area) were selected for this study on the regeneration of riparian tree species of Croton megalobotrys Müll. Arg, Philenoptera violacea (Klotzsch) Schrire, Senegalia nigrescens (Acacia nigrescens) Oliv and Diospyros mespiliformis Hochst. ex A. Dc. The height of each individual tree was estimated in randomly selected 30 plots (15 from each site) of 20 × 50 m for assignment to five regeneration classes: 0-0.5, 0.5-1, 1-2, 2-4 and >4 m. Linear regression was used to infer regeneration status of each species. An independent-sample Student’s t test was used to determine any significance differences in seedling density/ha and sapling density/ha between different sites at p < 0.05. Diospyros mespiliformis populations had an unstable regeneration structure in both sites, while P. violacea regeneration was stable regardless of land-use type. Croton megalobotrys and S. nigrescens had an unstable regeneration pattern in Seronga, while in Moremi it was stable; thus, the regeneration structure of C. megalobotrys and S. nigrescens is affected by land-use. This result implies that intervention is needed to conserve the two species in Seronga where the current land-use appears to be incompatible with regeneration; D. mespiliformis also needs to be conserved in both Moremi and Seronga.
基金This study which is part of GT’s PhD work was sponsored by the German Federal Ministry for Education and Research(BMBF).
文摘Introduction:Understanding the environmental factors that influence riparian vegetation community composition and distribution is important for understanding wetland ecosystem functioning.This understanding can further serve to inform policy aimed at conserving wetlands such as the Okavango Delta.In the Okavango Delta,information on the influence of distance from surface water on vegetation community composition and structure is limited.The objective of this study was to determine the relationship between distance from surface water and riparian plant communities at different sites in the Okavango Delta.Methods:Vegetation sampling was conducted in four sites in 20 m×10 m belted plots placed perpendicular to the river bank at 0–10 m,10–20 m,20–30 m,30–40 m,and 40–50 m distance classes.At each site,10–15 plots were sampled at each distance class.Basal area,species richness,cover,and plant diversity were determined for each plot.Indicator species analysis was used to determine the characteristic species at each distance class.One-way analysis of variance and Tukey post hoc analyses were used to compare species diversity,richness,cover,and basal area between distance classes.Generalized linear mixed(GLM)model was used to test for the overall impact of site and distance on each plant parameter.Results:Mean species richness was significantly(p<0.05)higher at 0–10 m than at 20–30 m,30–40 m,and 40–50 m in Boro.There was no significant difference within other sites.Mean species diversity also varied significantly(p<0.05)in Boro where it was higher at 0–10 m and 10–20 m than at 30–40 m.Mean basal area differed significantly within Jao and Upper Panhandle.In Jao,it was higher(p<0.05)at 0–10 m than at other distance classes.Mean percentage canopy cover differed significantly within all sites.In addition to this,plant species composition also changed along distance from surface water within each site.From GLM analysis,both distance and site significantly(p<0.05)influenced diversity and basal area.Species richness and cover were significantly(p<0.05)influenced by site only.Conclusion:Distance from surface water and site are important determinants of riparian plant dynamics in the Okavango Delta.
