Colonization of abandoned pastures by eastern red cedar (Juniperusvirginiana L.)

Abstract

Rates and patterns of colonization of the predominantly avian dispersed eastern red cedar (Juniperusvirginiana L.) were investigated in three abandoned pastures in southwest Virginia. The three populations, with median ages of 2, 5, and 14 years, showed sigmoid cumulative net increases in numbers of individuals over time. Exponential increase occurred during the first 6–9 years after initial establishment. Densities peaked in about 8–10 years. Only the youngest population showed a significant spatial gradient in the distribution of red cedar individuals, decreasing exponentially with distance from the nearest cone-bearing trees along the edge of the pasture. A decreasing activity gradient of avian dispersers with distance from the seed source may have influenced a differential seed input in the pasture, resulting in the observed spatial trend in tree density. No relationship existed between age and location of individuals within stands. The apparent spatial uniformity of overall density of individuals with increasing age (as noted in the 5- and 14- year-old populations) is probably due to several factors, including the increasing availability of avian perching sites and the addition of seed sources with increasing age of invading red cedar populations.