Woody Vegetation Status across Rural and Urban Land Use Types on the Riparian Zone of Sakubva River in Mutare District, Eastern Zimbabwe

Abstract

The study assessed the woody vegetation attributes across the rural and urban land use types on the Sakubva riparian zone in Mutare District, eastern Zimbabwe. The study contributes to the formation of baseline information on Sakubva riparian zone with possible use of woody plants as indicator species for biomonitoring the ecological health of this riverine ecosystem. The study area of Sakubva River stretch was delineated into two study strata: (i) the upstream Mutare urban land use type, and (ii) the downstream Dora rural land use type. To describe the woody vegetation composition, abundance and structure of Sakubva riparian zone, the following variables were recorded: tree and shrub height, basal stem circumference, number of stems per plant, tree/shrub density, number of coppiced woody plants, woody species diversity, human induced damage on woody plants, fire damage on woody plants and plant status. Descriptive statistics were used to summarize data collected on woody vegetation attributes and significance differences across the two land use strata were analyzed using the Mann-Whitney U tests (one-tailed). Woody species diversity was determined using the Shannon-Weiner diversity index. A hierarchical cluster analysis (HCA) using the Wards method with a matrix of 30 sample plots and only the recorded woody species data was used to explore dominance of woody species across the study strata. The study recorded a woody species richness of 21 across the study area, which was dominated by the plant family Fabaceae, sub-family Caesalpinoideae of the prototype Miombo woodland. All the measured woody plant variables recorded no significant difference (P > 0.05) between the two defined study strata, except for the sapling density (P < 0.05). The study hypothesized that Mutare urban environment has fewer human disturbances and a more intact riparian woodland as compared to rural land use in Dora community. However, it was concluded that woody vegetation composition and structure was generally less influenced by variations in land use type within the Sakubva riparian zone of eastern Zimbabwe. It was evident from this study that woody plants occurring in Mutare urban and rural Dora land use categories within the Sakubva riparian zone were to some extent damaged by humans as shown by evidence of past fires, wood harvesting and land clearance for gardening. We recommend continuous monitoring of riparian woodlands on varying land use categories across Mutare District, eastern Zimbabwe.