Speaker: Dr. Vijayalaxmi Kinhal (Institute of Bio-architecture and Ecology, Auroville)
Organiser: Department of Ecology, French Institute of Pondicherry.
Abstract
Patterns of reforestation in tropical dry evergreen forest on the coromandel coast under different land-use and management practices were studied. Directed succession seen in a chronosequence of 2, 6, 12 & 30 years old afforestation sites with soil and water conservation supplemented by enrichment planting was compared to spontaneous succession chronosequence of grazing lands aged 2, 4, 10 & 50 years.
Continuous disturbance (grazing pressure) slows the rate of succession. After 30 years directed sites are more similar (16%) and species rich (123) than spontaneous sites 5% & 109 species respectively. The significant vegetative inter-species and overall community interactions are all positive in both pathways.
Resilience for vegetation ≥ 1 cm dbh reveals density is seven times, basal area is five times, cover is 29 times and height is 1.5 times more in oldest sites of directed than spontaneous succession, but number of primary forest species regenerating is similar in both cases. Directed succession is expensive, while spontaneous succession showing only 30% recovery nonetheless has 64% of its species providing usufruct benefits.
Nucleated succession by a nurse-plant is the mode of spontaneous succession. Phoenix pusilla, an endemic was indicated as the nurse plant by traditional ecological knowledge (TEK) from a south Indian tribe Irula.
Phoenix pusilla was significantly spatially associated with 11 primary and two secondary species. An experiment over eight months revealed amelioration of abiotic conditions by an decrease in soil temperature (by 50%) and radiation (by nine times), increase in organic matter content and water holding capacity under nurse plants as compared to open interspaces, facilitated ten times more seedling germination and emergence, with seedling height twice taller under Phoenix pusilla, than in interspaces.
All secondary tree species enumerated in this study have an Asian distribution & can aid restoration in dry forests of India and Asia.
