Plant-animal interactions and forest community dynamics on the 30-ha Mo Singto forest dynamics plot in continental Thailand

Background/Question/Methods: The 30-ha Mo Singto forest dynamics plot was established in central Thailand (14° N latitude) on which all trees and shrubs ≥ 1 cm in diameter were censused, identified and mapped in 2004–2005. There are 262 species of trees and shrubs ≥ 1 cm in diameter, and also about 120 species of lianas. This plot lies in wet seasonal broad-leaved evergreen forest in Khao Yai National Park, inhabited by a largely intact fauna which includes white-handed gibbons, pig-tailed monkeys, Asian elephant, 3 species of deer, 2 species of bears, wild pigs, 5 species of civets, 4 species of diurnal squirrels, 4 species of hornbills, etc.—all potential plant seed dispersers or predators. Study of forest dynamics within this rich community is leading to important insights concerning tree species recruitment, forest regeneration, and interaction specificity. Using the plot tree database and GIS, we have been able to study in detail the foraging pathways and diet of gibbons, to try to answers questions concerning the diversity of plant species in their diet, the seasonal and interannual variability of their diet, and the specificity of their seed-dispersal relationships.

Results/Conclusions: Studies focussed on individual tree species have yielded important insights into the specificity and variability of animal disperser–plant relationships. The tree flora contains a wide spectrum of regeneration types including species that can regenerate in early successional forest and those which cannot, and species which are regenerating in old-growth forest and those which are not. A few old-growth regenerating species appear to be obligate gibbon- or hornbill-dispersed species; however, many species on the plot are dispersed by a wide variety of birds and mammals, both arboreal and terrestrial. Gibbon diets include a suite of preferred, succulent, large-seeded fruit species, but also a broad variety of fruits and leaves that are eaten when preferred species are not available. The total fruit diet of gibbons includes at least 105 species, about half of all animal-dispersed trees and lianas commonly available in the forest. The great flexibility of plant dispersal mechanisms, and of animal diets, appears to be related to the high seasonal variation in fruit availability and, especially, the high interannual variability of flowering and fruiting, which in turn can be related to the unpredictable variability in the length and severity of the dry season in this monsoonal continental climate.