Conservation of Plant Diversity in Agroforestry Systems in a Biodiversity Hotspot Region of Northeast India

Abstract

In Assam, a north-eastern state of India, most of the traditional agroforestry systems are still practised. The plant species composition of three agroforestry systems namely homegardens tea gardens and agrisilvicultural systems, were assessed using quadrat method. A total of 516 plant species belonging to 241 genera under 91 families were recorded, which consisted of 134 trees, 143 shrubs (67 shrub species and 76 species of saplings) and 239 herbs (93 herb species, 33 climber species and 113 species of seedlings). Homegardens had the highest species richness (475 plant species) belonging to 234 genera under 90 families. This was followed by agrisilvicultural systems (101 spp., 43 genera, 29 families), and the least was in tea gardens (79 spp., 41 genera, 25 families). The highest average number of plant species per system was recorded in homegarden (108.96 ± 5.96, range 23–207 spp.). A negative correlation was found between the agroforestry system plot size and plant species richness. Sorenson’s similarity index showed a very low degree of similarity in the plant species recorded among the three selected systems. Out of 516 plant species recorded across the different agroforestry systems, 1.0% species (n = 3) were vulnerable (Aquilaria malaccensis, Saraca asoca and Santalum album), 8.9% species (n = 46) were least concerned, 1.6% species (n = 8) were data deficient and 88.6% species (n = 457) were not assessed. Only homegarden recorded all the three plant species under the vulnerable category of IUCN Red List. It can be concluded that the agroforestry systems, specially the homegardens harbour rich plant diversity and act as miniature versions of natural forests by conserving rare, threatened and data-deficient plant species. The results suggest that the agroforestry systems with some management interventions need to be promoted as conservation models in areas with high pressure on tropical forests.