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Fecundity schedules for forest trees.
LaDeau, Shannon 1, Clark, James1, HilleRisLambers, Janneke1, Ibanez, Ines1, 1
ABSTRACT- Forest tree fecundity schedules affect community dynamics and forest response to disturbance and global change. Unfortunately, there is little quantitative data on changing tree fecundity with age in natural forests. Consequently, the relationship between size and net reproductive rates is poorly understood. As a result, most studies assume that fecundity M is proportional to basal area B, i.e., M(B) = aB. Estimation requires years of data and a method for determining seed production in closed forest stands with overlapping seed shadows. We applied an inverse modeling approach to an extensive data set and estimated fecundity in a closed Southern Appalachian forest as a function of tree size. This was done under several different assumptions about how fecundity might change with age. We find that proportionate allocation to fecundity declines with tree size much faster than observed for open-grown trees in seed orchards. For the fitted model M(B) = aBb, we obtain slope estimates of 0 < b < 1. The form of this allocation change varies among species. Together with growth and survival data we use these results to estimate net reproductive rates for several species of temperate forest trees.
KEY WORDS: fecundity, seed shadow, allocation