Title: Stages and Spatial Scales of Recruitment Limitation in Southern Appalachain Forests
Author: Clark, James S.; Macklin, Eric; Wood, Leslie;
Source: Ecological Monographs, 68(2), 1998, pp. 213-235
Publication Series: Miscellaneous Publication
Description: Recruitment limitation of tree population dynamics is poorly understood, because fecundity and dispersal are difficult to characterize in closed stands. We present an approach that estimates seed production and dispersal under closed canopies and four limitations on recruitment: tree density and location, fecundity, seed dispersal, and establishment. Consistent estimates are obtained for 14 canopy species using 5 yr of census data from 100 seed traps and several thousand mapped trees and seedlings from five southern Appalachian forest stands that span gradients in elevation and moisture. Fecundity (seed production per square centimeter of basal area) ranged over four orders of magnitude, 100 cm2 basal area (Carya, Conrus, Nyssa Quems) to >lO3 cm2yr (Betula). Mean dispersal distance ranged from <5 m (Cornus, Nyssa) to >20 m (Acer, Betula, Liriodendron, Tsuga) and was positively correlated with fecundity. Species also differ in the degree of seed clumping at fine (1 m2) spatial scales. Dispersal patterns can be classed in two groups based on dispersal vector: wind-dispersed taxa with high fecundities, long-distance dispersal, and low clumping vs. animal-dispersal taxa with low fecundities, short-distance dispersal, and a high degree of clumping. "Colonization" limitations caused by sixes and locations of parent trees, fecundity, and dispersal were quanti6ed as the fraction of sites receiving seed relative to that expected under null models that assume dispersal is nonlocal (i.e., long-distance) and not clumped (i.e., Poisson). Difference among species in colonization levels ranged from those capable of saturating the forest floor with seed in most stands (Acer, Betula, Liriodendron) to ones that leave much of the forest floor without seed, despite presence of adults (Cayra Cornus, Nyssa Oxydendrum). Seedling establishment is one of the strongest filters on recruitment in our study area. Taken together, our results indicate (1) that fecundity and dispersal can be resolved, even under a closed canopy and (2) that recruitment of many species is limited by the density and location of source, dispersal patterns, or both.
Keywords: dispersal, estalishment, fecundity, forest dynamics, negative binomial, recruitment, seed rain, southern Appalachains
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Clark, James S.; Macklin, Eric; Wood, Leslie 1998. Stages and Spatial Scales of Recruitment Limitation in Southern Appalachain Forests. Ecological Monographs, 68(2), 1998, pp. 213-235
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