Abstract:
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.
