Diversity and carbon sequestration potential of preferred on-farm tree species in Najja Sub-county, Buikwe District.

Abstract

On-farm tree planting, often practiced under agroforestry systems, has been a significant component of sustainable land use in Sub-Saharan Africa (SSA), including Uganda. The planting and retention of trees is recognized globally for its dual role in supporting farmer livelihoods and providing essential ecosystem services, particularly carbon sequestration for climate change mitigation. Since farmers' preferences for particular tree species are influenced by a complex interplay of socio-economic, cultural, ecological, and agronomic factors this study sought to ascertain the preferences, diversity and carbon sequestration potential of on-farm tree species in Najja sub county, Buikwe district. The specific objectives of the study were: (1)I To assess the farmers’ preferences, uses and management practices of the different on-farm trees in Najja Sub- county-Buikwe District. (2) To evaluate the abundance and diversity of on-farm trees in the area and (3) To determine the amount of carbon sequestered by the preferred-on farm tree species in the area. A mixed methods research design combining both quantitative and qualitative research methods was used to gain a more complete picture than a standalone quantitative or qualitative study, The research involved household surveys to assess farmer preferences and management practices, alongside rigorous field measurements of individual tree parameters such as Diameter at Breast Height (DBH), crown width and height for biomass estimation across 45 sampled plots. In-depth interviews with farmers was also used through one-on-one conversations between the researcher and the respondent aimed at obtaining respondent’s experiences, opinion and feeling about a given topic. The collected data were checked, cleaned, coded and entered into Statistical Package for Social Scientists (SPSS) version 23.0 and Microsoft excel for analysis. To obtain farmers’ preferences, uses and management practices of the different on-farm trees in the area, frequencies were run for all responses to get the number of respondents for each use ,commonly preferred species and management practices for different on farm trees. Findings revealed a strong and consistent farmer preference for species that offer direct benefits, primarily fruits and timber. All respondents reported that they plant or retain trees in their various farms. Whereas 87% of the respondents preferred Autocarpus heterophyllus, 77% of them preferred Mangifera indica and 62% of them planted Markhamia lutea and a few respondents planted Theobroma cacao. While a moderate on-farm tree diversity was observed, evidenced by a Shannon-Wiener Diversity Index of 2.3015, a significant knowledge gap emerged, with nearly 80% of farmers reporting being unaware of the broader carbon sequestration benefits provided by these trees. Total carbon sequestration potential computed to be approximately 0.3 tons of CO₂ per hectare across the sampled farms were not evenly distributed but was significantly driven by larger, mature trees, like Ficus sycomorus and Maesopsis eminii. These trees were identified as key contributors to carbon storage due to their growth characteristics and density. Extension services that focus on promoting sustainable management practices for high-carbon stock species should be initiated to incentivize farmers ono protecting the existing biodiversity and maximizing the ecological and economic benefits derived from agroforestry systems. A critical step must be taken to initiate targeted public awareness and educational campaigns to inform the majority of the respondents who are currently unaware of the carbon sequestration benefits of their trees.