Impact of farming systems on riparian vegetation of lake manyara catchment at chemchem and endabash rivers in karatu district, tanzania

Highland catchments of Lake Manyara basin are undergoing degradation through human activities from the adjacent communities. This study was conducted to assess the impact of farming systems on vegetations in the highland catchments of Lake Manyara basin namely Chemchem and Endabash rivers. The specific objectives were to identify the farming systems used and their sustainability with regard to wetland conservation, assess and compare the plant species composition and diversity between degraded and non degraded riparian zones. Riparian forests were stratified into degraded and non degraded strata. One hundred twenty eight concentric circular sample plots (64 plots in each strata) were established laid along transects. The difference between the two strata in each catchment was assessed using Sorensen’s similarity index and Shannon Wiener diversity index. All vascular plants were identified and DBH was measured for trees/shrubs in each plot. Monocroping and mixed farming systems are the major farming systems used, though both of them do not support conservation of pre existing riparian plants. Vegetation analysis revealed that plants dominating degraded riparian zones were different from those of non degraded riparian zones in both composition and diversity. The Shannon-Wiener diversity indices for trees ≥ 5cm dbh in the degraded and non degraded zone of Chemchem catchment were 2.9 and 2.6 respectively implying medium species diversity with higher diversity in the degraded zone. In the Endabash catchment the Shannon-Wiener diversity indices were 2.6 and 2.8 in the non degraded and degraded riparian zones respectively which imply moderate levels of diversity. All these may indicate medium disturbance which have not affected the areas very adversely. Sorensen’s similarityiii indices of 40.51 % and 45.8 % observed between degraded and non degraded zones in Chemchem and Endabash catchments respectively show that there are differences between degraded and non degraded though not very significant.