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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #144730

Title: VEGETATION DYNAMICS OF A NEW ENGLAND FOREST IN RELATION TO ENVIRONMENTAL AND HISTORICAL FACTORS

Author
item Goslee, Sarah
item NIERING, WILLIAM
item URBAN, DEAN
item CHRISTENSEN, NORMAN

Submitted to: The Journal of the Torrey Botanical Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2004
Publication Date: 7/20/2005
Citation: Goslee, S.C., Niering, W.A., Urban, D.L., Christensen, N.L. 2005. Vegetation dynamics of a New England forest in relation to environmental and historical factors. The Journal of the Torrey Botanical Society. 132(3):471-482.

Interpretive Summary: Plant community composition information collected along permanent transects monitored for 45 years was used to describe the changes in vegetation in a New England oak-hemlock forest. Plant composition was related to soil and topography, but the effects of land use history were much stronger than any environmental effects. An understanding of the interacting effects of environment and history can aid in the development of reliable, site-specific plans for conserving or even creating valuable or interesting ecosystems.

Technical Abstract: Forty-five years of vegetation data from a currently forested site in southeastern Connecticut were analyzed to describe plant community dynamics and to examine the relative importance of environmental and historical factors over time. Hemlock (Tsuga canadensis L.) increased in importance in the forest canopy until the introduction of the hemlock woolly adelgid. The many herb and shrub species initially found in post-agricultural areas of this site declined or disappeared as the forest canopy closed. Shade-intolerant understory species are now increasing in abundance as the death of large hemlocks opens gaps in the canopy. Mantel path analysis was used to quantify the complex network of relationships among environment, land use history and the composition of the tree, shrub, herb and sapling strata. Environment as a whole (including slope, aspect, drainage, soil texture, surface rockiness and soil depth) was poorly correlated with vegetation; only the relationship between the shrub stratum and environment was significant. Slope and drainage were the most important environmental factors measured. Land use history was strongly related to all four strata, but the strength of this relationship decreased over time. The sapling stratum was highly variable through time; other strata showed more self-similarity between samples. Common models of forest succession suggest that both the correlations between vegetation composition and environmental factors and the relationships among strata should increase over time. Neither of these predictions was true for this site. The role of land use history may affect the vegetation so strongly as to conceal the effects of environmental variation. Few studies have investigated the role of alternate pathways or common causes on the complex relationships between these variables; Mantel path analysis provides a framework for doing so that may lead to new insights into the theory of vegetation dynamics.