Sustainability of restoration potential through woody tree diversity and provisioning ecosystem services of tree-based tropical home gardens in degraded catchment-landscapes

Tree-based tropical home garden agroforestry systems in South Asia and other regions of the world deliver almost all ecosystem services provided by natural forests at different scales. These systems play a vital role in restoring degraded catchment landscapes. However, the sustainability of the restoration potential depends on the woody tree diversity and their provisioning ecosystem services (PESs). This study estimated the woody tree diversity of home gardens in selected Divisional Secretariate Divisions in two districts of the Upper Mahaweli Catchment (UMC) in Sri Lanka, and assessed the PESs provided by woody tree species in home gardens. The woody tree diversity was estimated using the Shannon Index, Simpson Index, and Evenness Index. PESs were assessed using primary data obtained via a tree resource assessment survey with a household survey, and analyzed using descriptive statistics. A total of 110 woody tree species belonging to 38 families were identified. The Shannon Index (1.51-2.95), Simpson Index (0.58-0.68), and Evenness Index (-0.38-2.95 indicated high tree diversity, comparable to tropical forests in the South Asian region. Regarding PESs, the highest percentage of tree species provided timber (36.23%), followed by food (23%), multipurpose (15 %), medicinal products (8%), fuelwood (10%), spices (3%), fodder (3%), and green manure (2%). Additionally, approximately 3% of woody tree species offered minor uses such as gum, oil, resins, fencing, and decoration. These results indicate that woody tree species in home gardens are capable of providing a wide variety of PESs. The study confirms that home gardens in UMC possess significant restoration capacity in terms of tree species diversity and the ability to generate PESs. Consequently, they serve as a viable strategy for maintaining the long-term ecological sustainability of catchment landscapes. This study provides a model for utilizing tree-based home garden agroforestry systems as an alternative strategy for the ecological restoration of degraded landscapes worldwide.