We used size-structured Lefkovitch projection matrix anal
ysis to predict future trends in the survival of
Aquilaria crassna (Th
ymelaeaceae), a tropical evergreen forest tree that has been highl
y sought after for its valuable aromatic wood (agarwood) for millennia. Data on growth, damage to trees b
y poachers, fruit production, seed dispersal and seedling recruitment were collected from a 30-ha plot in Khao Yai National Park, central Thailand that had seen moderate poaching. The population as
ymptotic growth rate,
yle="text-decoration:none; color:black" href="/science?_ob=MathURL&_method=retrieve&_udi=B6V5X-4SN92K5-2&_mathId=mml8&_user=1067359&_cdi=5798&_rdoc=22&_acct=C000050221&_version=1&_userid=10&md5=3ba8af9354aed55fbc79ed6d00196cd8" title="Click to view the MathML source" alt="Click to view the MathML source">λa, and transient growth rate,
yle="text-decoration:none; color:black" href="/science?_ob=MathURL&_method=retrieve&_udi=B6V5X-4SN92K5-2&_mathId=mml9&_user=1067359&_cdi=5798&_rdoc=22&_acct=C000050221&_version=1&_userid=10&md5=316f8fd58edcc9377823ef362004fd90" title="Click to view the MathML source" alt="Click to view the MathML source">λtr, found from using the matrix to project the observed population 48
years, were 1.002 and 1.005, respectivel
y, with 95%confidence intervals of [0.985, 1.016] and [0.985, 1.023]. The stable size distribution obtained from the matrix was reasonabl
y similar to the observed size distribution, suggesting that at the time of the stud
y the population was not far from equilibrium. Sensitivit
y anal
ysis and simulations of poaching on adult trees indicate that both
λ’s are ver
y sensitive to the removal of adult trees and the growth of preadult trees. In particular, the increase in tree mortalit
y and decrease in preadult growth rate caused b
y agarwood collection seen in some areas could cause extirpation of the population. While in such cases the population appears to be poised on the brink of decline, several factors that we could not evaluate could alter its fate. First, adult deaths could stimulate recruitment of
young under the parent trees; second, there is marked
year-to-
year variation in fruiting success and possibl
y recruitment; third, there is considerable spatial variation in tree densit
y and recruitment, suggesting that attempts to evaluate future success need to encompass larger spatial and time scales.