Conservation prospects for threatened Vietnamese tree species results from a demographic study
Pham Duc Chien, Pieter A.Zidema, Nguyen Hoang Nghia
Given that changes in population size are slow, information on future prospects of long-lived tree species is necessarily obtained from demographic models. We studied six threatened tree species in four Vietnamese protected areas: the broad-leaved Annamocarya sinensis, Manglietia fordiana and Parashorea chinensis, and the coniferous Calocedrus macrolepis, Dacrydium elatum and Pinus kwangtungensis. With data from a 2-year field study on recruitment, growth and survival, we constructed matrix models for each species. All species showed continuous regeneration, as indicated by annual seedling recruitment and inverse J-shaped population structures. To evaluate the future prospects of our study species, we calculated three parameters: (1) asymptotic growth rates (k) from matrix models indicated significant population declines of 2–3%/year for two species; (2) population trajectories for 50–100 years showed slight population declines (0–3%/year) for five species; and (3) the reproductive period required for an adult tree to replace itself was excessive for three of the six species, suggesting that these species presently have insufficient recruitment.
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