Selecting framework tree species for restoring seasonally dry tropical forests in northern Thailand based on field performance

Background

Framework tree species are indigenous forest tree species, planted to complement and accelerate natural regeneration of forest ecosystems and encourage biodiversity recovery, on degraded sites. This study tests the extent to which 37 native forest tree species might act as framework tree species to accelerate recovery of evergreen, seasonal forest in a degraded upper watershed in Doi Suthep-Pui National Park in northern Thailand.

Research goals & methods

The trees were planted at a density of 3125 ha^-1 in 1998 and 1999. The plots were hand weeded and fertiliser applied around planted trees three times during the rainy season. Field performance of planted trees was assessed at the end of the second wet season after planting by monitoring height, crown width and weed cover. A fire, which spread through some of the plots in March 2001, enabled assessment of resilience to fire for some of the species. Nine species were ranked as ‘excellent’ framework species, including Ficus hispida var. hispida, Gmelina arborea, Hovenia dulcis, Melia toosendan, Michelia baillonii, Prunus cerasoides, Rhus rhetsoides and Spondias axillaris. Fifteen species qualified as ‘acceptable’ framework species: Acrocarpus fraxinifolius, Balakata baccata, Castanopsis acuminatissima, Ficus altissima, Ficus benjamina var. benjamina, Ficus glaberrima var. glaberrima, Ficus racemosa var. racemosa, Ficus subulata var. subulata, Glochidion kerrii, Heynea trijuga, Macaranga denticulata, Machilus bombycina, Nyssa javanica, Sapindus rarak and Sarcosperma arboreum.

Conclusions & takeaways

Nine species performed poorly in most respects and should probably be rejected as framework species: Aglaia lawii, Callicarpa arborea var. arborea, Cinnamomum caudatum, Diospyros glandulosa, Helicia nilagirica, Horsfieldia thorelii, Lithocarpus fenestratus, Phoebe cathia and Pterocarpus macrocarpus. Assessment of the growth, survival rates, and resilience of indigenous forest trees can assist in identifying framework trees for restoration.