Characteristics of bee fodder plants of mlele beekeeping zone, Katavi, Tanzania

MSc Dissertation

Pollination by insects, particularly bees, is essential for biodiversity conservation and plant reproductive success. Tanzania is characterized by a rich diversity of flowering plants estimated to be over 9000 species. A wide variety of flowering plant species serve as bee fodders and are essential to maintaining healthy bee populations. Mlele District in Katavi region of Tanzania is among the highest honey producing area in the region. Several studies on bee fodder plants characteristics, including their composition and nectar quality have been done in temperate and sub temperate regions with few in the tropics. These studies have reported the impact of environmental and human disturbances on bee fodder plants. Despite the potential of Katavi region for beekeeping, few studies have been done in the region, especially on the characteristics of bee fodder plants incorporating environmental, disturbance and the nectar quality. This knowledge gap results into ineffective conservation of food sources for bees, unsustainable beekeeping practices, low production and quality of bee products. The study overall objective was to determine the characteristics of bee fodder plants of Mlele Beekeeping zone. The study included two objectives, the first objective was to determine the composition of bee fodder plants along environmental and disturbance gradients and the second was to determine the periodicity of floral rewards by the bee fodder plant species. A systematic sampling design was employed to assess how environmental and disturbance gradients impact bee fodder plants composition. A total of 50 rectangular plots of size 50 by 30 m were laid in two transects with 25 plots in each transect. Plant flowers were observed for 10 minutes and were scored as bee fodder plants after at least three bees visited the flower within the observation period. The periodicity of floral rewards objective employed purposive sampling design on the basis of provision of measurable amounts of nectar and enough flowers to conduct the study with repeated measurements. Plants in which the honeybees extended their proboscis into the flowers were determined as nectar rewarding plants and where bees collected pollen were determined as pollen rewarding plants. Data collection on bee fodder plants composition was obtained through a summary of species data list and their abundance values. Climatic data was obtained from the current climate data set downloaded from world climate site with a 30 arc seconds resolution and four subsets of biophysical data were used. Disturbance data was recorded for presence or absence and the disturbance type.550 hours of observation were made for recording of flower visitors on ten bee fodder plant species from 0700 hours to 1800 hours. Nectar was extracted by micro capillary tubes and quality was measured in form of total sugar concentration by the use of a digital handheld refractometer. In the data analysis section, data skewness was addressed by standardization of the data. Detrended Correspondence Analysis (DCA) was applied to assess the ecological gradient's magnitude within the species composition matrix and to determine the appropriate constrained ordination method. The results gave the option for Canonical Correspondence Analysis (CCA) due to the data's heterogeneity. Log-transformations were applied to species abundance data to meet multivariate normality assumptions. Rare species occurring in fewer than five plots were excluded from the analysis. Stepwise automatic forward selection identified significant explanatory variables for CCA. The chosen variables were then constrained against tree species and community composition. Permutational Multivariate Analysis of Variance Using Distance Matrices (Adonis) was employed for variance partitioning. The community composition was identified by the use of Bray-Curtis’s dissimilarity and Silhouette validation. Generalized linear models were created to examine visitations and effect of nectar concentration and temperature on bee visitation rate. Overall, 71 bee fodder plants belonging to 25 families were recorded. The results revealed that 23% of the variation in the composition of dominant tree species within the study area could be attributed to the interplay of environmental and disturbance factors. Elevation emerged as the most influential predictor, accounting for approximately 11.6% of the total variation. Annual mean temperature contributed around 3.5% to the observed variation and annual precipitation about 3.6%. Four bee fodder plant communities were identified in the area with first cluster being dominated by Erythrophleum africanum, second with Brachystegia glaucescens, third with Diplorhynchus condylocarpon and fourth Bobgunnia madagascariensis. Nectar concentration was identified as a central driver of bee visitation patterns. The bee fodder plants including Antidesma membranaceum and Friesodielsia obovata, showcased nectar concentration percentages that significantly enhanced their attractiveness to bees. The results of this research study have the potential in providing valuable insights to beekeepers and conservationists for improving beekeeping practices in Mlele Beekeeping zone. It provides understanding into factors influencing bee visitation rates to different bee fodder plant species. It also highlights the significance of nectar sugar concentration and temperature in shaping bee foraging behavior. Environmental factors particularly elevation, annual mean temperature and annual precipitation are seen to be important in shaping the composition of bee fodder plants. The findings recommend prioritizing and promoting planting and conserving bee plant species with high visitation rates such as Antidesma membranaceum, Psorospermum febrifugum and Securidaca longepedunculata to support bee populations and enhance pollination services. Further research is needed into other bee fodder plants traits that attract bee to deepen our understanding of bee interactions. Understanding the relationship between environmental factors and bee plant communities in other locations and other factors such as soil type and land use should be considered. As ecosystems face ongoing challenges from climate change and human activities, such research becomes increasingly valuable in ensuring the health of bee populations and the preservation of biodiversity. Further research in other regions and at different scales is needed to expand our knowledge of these vital relationships and their implications for beekeeping and conservation efforts globally.

The Higher Education for Economic Transformation (HEET) Project