TREE DIVERSITY AND THEIR CARBON STOCK IN SELECTED URBAN GREEN INFRASTRUCTURES, LILONGWE CITY, MALAWI

Abstract

Urban vegetation stands as a pivotal ecosystem for the provision and support of ecosystem services in towns and cities leading to the attainment of SDG 11: “Make cities and human settlements inclusive, safe, resilient and sustainable.” In pursuit of this goal, this study aimed at determining the present urban tree species richness, diversity and carbon stock potential in Lilongwe City, Malawi. Six distinct urban forest types were identified: Cemeteries, Institutional lands, Parks and Recreation, Residential, Riverine, and Roadside/Avenues. Stratified random sampling was done in order to come up with the required number of samples. For parks/recreation and cemeteries sample plots of 20m x 20m and 10m x 10m were laid respectively. For roads and riverine, sample plots were laid side by side of 20m x 20m at an interval of 500m. For institutions and residential areas, a total count of trees was done and the area for each was measured. In each sample plot/area, a full tree inventory was conducted. A total of 4,031 individual trees was recorded comprising of 166 tree species across all six forest types, with five species common to all forest types. Residential forests recorded the highest tree species richness with 87 and Riverine was the least with 15. Only 38 tree species were found in parks/recreation, 37 in residential, 15 in institutional lands, 4 in road/avenue, and 1 in cemeteries. Furthermore, the Rẻnyi diversity profile for residential forests was above the profiles of the other forest types signifying it being more diverse than others; albeit with an uneven distribution of individual tree species, primarily attributed to the dominance of Mangifera indica. Similarly, the shape of profiles for other forest types were less horizontal. An even distribution of individual species in an ecosystem signifies a healthier ecosystem critical in sustaining ecosystem services. Carbon stock estimation revealed a mean of 51.67±5.27 t/ha with 7.21% uncertainty, and significant differences (P<0.001) among forest types. Pairwise analysis demonstrated non-significant differences (P>0.05) in carbon stock estimation between institutional and cemetery forests, recreation and residential forests, as well as riverine and avenue forests. Therefore, the present results suggest that all six forest types are disturbed and need appropriate management. Hence the study outcomes offer a foundation for informed decision-making by town planners. There is also need for a comprehensive study to estimate carbon emissions, particularly in Lilongwe's industrial areas, to address the holistic sustainability of the city's urban environment