Document: GOR-3-68-9

Causes of spatial pattern in post-fire pine recruitment.

BLAIR, S.D.* and G.A.FOX

University of South Florida, Tampa, FL 33620-5150 ¹

Abstract:
Fire-frequency and competition both affect the dispersion of pine seedlings. We have studied patterns in the spatial dispersion and age/stage structure of Pinus palustris and P. elliottii growing in replicated experimental plots that, over a 20-yr period, have been burned every 1, 2, 5, or 7 yrs, or never burned. Average juvenile pine densities are much reduced as burn frequency increases. Two factors contribute to the reduction in juvenile pine densities: less frequent (hotter) fires (a) cause larger open patches and therefore longer dispersal distances, and (b) permit greater growth of shrubby Quercus competitors. We have used spatial patterns of juvenile pine dispersion in each burn plot to study the importance of both dispersal distance and oak competition. By statistically holding local oak density constant, we can estimate the effect of distance from seed source on pine recruitment. Similarly, by statistically holding distance from seed source constant, we can estimate the effect of local oak density on pine recruitment. Our analyses show that the relative importance of these factors in governing pine recruitment depends on spatial scale: In fires of great extent, dispersal limitation is important, but in fires of smaller extent, oak competition is the dominant factor.

Keywords: Fire, pine, oak, spatial, recruitment, dispersal, competition

This abstract is being presented at: 3:45 PM in session:
Oral Session #35: Fire Ecology.