The roles of fire and environmental factors in plant community dynamics of high-elevation yellow pine woodlands in northeastern West Virginia

Background/Question/Methods

Management using fire is becoming more common in the central Appalachians, but little is known about historic fire regimes and community dynamics of fire-adapted plant species in high elevation habitats. I quantified evidence of historic wildfire in high elevation pine woodlands in the Ridge and Valley and Allegheny Front regions of WV and tested two hypotheses about the role of fire: 1) that fire determines the pattern of regeneration and successional dynamics of yellow pine (Pinus rigida & P. pungens) woodlands on ridges and associated slopes, and 2) that edaphic factors, not fire, regulate pine communities in stressful habitats such as clifftops and bogs. Stressful habitats may be relatively free of competing tree species and provide safe sites for yellow pine recruitment. Between 2009 and 2011, I collected data on plant abundance, size structure, pine recruitment, and evidence of fire at 46, 20 x 20 m study sites in northeastern WV from 650-1200 m elevation. Cross-dated increment cores were used to place sections from fire-scarred trees and coarse woody debris on the timeline, so that the years and seasons of historic forest fires could be identified.

Results/Conclusions

Ten plant community types were described using cluster analysis and NMS ordination of plant abundance data. An index of fire evidence (FEI; 0-4 kinds of fire evidence present per site) varied significantly across community types and species composition as represented by NMS ordination coordinates. A complex picture of the role of fire emerged that did not confine it to any particular community type or landform, but cliffs and slopes had significantly higher FEI values than bogs. Pine seedling regeneration was most strongly determined by landform, with 94% of all pine seedlings (< 1 m tall) growing in either cliff or bog habitats. Dendrochronological evidence showed that fires occurred from the mid-late 1800’s through the 1960s, but fires burned at different sites in different years. A patchy disturbance history and edaphic factors that vary by landform likely worked together to determine community composition in high elevation pine woodlands, and these factors are incorporated into a conceptual model of high elevation pine successional dynamics. The range of variability in historic fire frequency and seasonality, and whether or not fire is needed to perpetuate pine populations on different landforms, both have important implications for future management of high elevation pine communities.