Propagating framework tree species to restore seasonally dry tropical forest: implications of seasonal seed dispersal and dormancy

ABSTRACT: An effective approach to forest restoration in degraded tropical forestland is the so-called ‘framework species method’, which involves planting 20–30 indigenous forest tree species, to re-establish a basic forest structure that catalyses biodiversity recovery. 

For the seasonally dry tropical forests of Doi Suthep-Pui National Park in northern Thailand, a provisional list of 36 potential framework species was compiled, from 19 different families, representing a broad spectrum of the tree flora. This paper examines the seed germination characteristics of these species when grown as a nursery ‘crop’, for planting to restore degraded sites, focussing on germination phenology and dormancy. It considers how such characteristics affect the first stage of nursery production from seed collection to pricking out seedlings in the nursery.

Twenty-nine species had germination percentages of 60% or higher, which is acceptable for nursery production. The median length of dormancy (MLD) ranged from 7 days for Erythrina subumbrans to 219 days for Lithocarpus garrettianus. Germination was defined as rapid if MLD was <3 weeks, and slow if it was >12 weeks. Twelve species germinated rapidly and eight germinated slowly, the remainder being intermediate. Seedling emergence ranged over a period of 7 days in the case of Erythrina stricta and E. subumbrans to 322 days in the case of L. garrettianus.