Browsing by Subject "Appalachian Mountains"
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Item Fire Regimes and Successional Dynamics of Pine and Oak Forests in the Central Appalachian Mountains(2012-07-16) Aldrich, Serena RoseThe role of fire in determining the structure and composition of many forested ecosystems is well documented (e.g. North American boreal forests; pi?on-juniper woodlands of the western US). Fire is also believed to be important in temperate forests of eastern North America, but the processes acting here are less clear, particularly in xerophytic forests dominated by yellow pine (Pinus, subgenus Diploxylon Koehne) and oak (Quercus L.). In this study, I use dendroecological techniques to investigate fire history and vegetation dynamics of mixed pine-oak forests in the central Appalachian Mountains of Virginia. The study addresses three objectives: (1) develop a lengthy fire chronology to document fire history beginning in the late presettlement era and extending throughout the period of European settlement, industrialization and modern fire exclusion; (2) explore fire-climate relationships; and (3) investigate vegetation dynamics in relation to fire occurrence. The study was conducted on three study sites within the George Washington National Forest. I used fire-scarred cross-sections from yellow pine trees to document fire history. Fire-climate relationships were investigated for each study site individually and all sites combined using superposed epoch analysis (SEA). Fire-history information was coupled with dendroecological data on age structure to explore stand development in relation to fire occurrence. Results of fire history analysis reveal a long history of frequent fire with little temporal variation despite changes in land use history. Mean fire intervals (MFI) ranged from 3.7?17.4 years. The most important change in the fire regime was the initiation of fire suppression in the early twentieth century. Results of SEA show that periodic droughts may be important drivers of fire activity. Drought the year of fire was important at two of the three study sites and when all sites were combined. Results of age structure indicate that vegetation development was clearly influenced by fire. Frequent burning maintained populations of yellow pine throughout the period of study until fire suppression allowed fire-sensitive hardwood trees and shrubs to establish. It is clear from this study that continued fire suppression will likely result in fire-tolerant pines and oaks being replaced by more mesophytic trees and shrubs.Item The Influence of Fire and Other Disturbance on Ericaceous Shrubs in Xeric Pine-Oak Forests of the Appalachian Mountains(2012-07-16) Pipkin, AshleyFire suppression in the southern and central Appalachian Mountains has resulted in an alteration to vegetation structure and composition. For this research the dominant species, abundance, density and age structure of the ericaceous shrub layer is characterized on four sites across the southern and central Appalachian Mountains. Fire histories for each of the sites varied, and were determined in previous research using dendroecological techniques. Over 800 ericaceous shrubs were collected, species included Pieris floribunda (Pursh) Bentham & Hooker f., Rhododendron maximum L. and Kalmia latifolia L.. Basal area of ericaceous shrubs was significantly different between sites. Age structures show that when fire suppression started Ericaceae began to establish. A few Ericaceae cross-sections displayed scars, that are likely associated with fire events, suggesting they probably survived mild fire events. Ericaceous shrub age structures were also compared to SPB outbreaks and PDSI. There were no significant correlations, but field observations suggest that SPB may be providing conditions suitable for Ericaceae establishment. Topographic patterns reveal that Kalmia latifolia is most abundant at mid-slope positions and decreases at higher and lower slope positions. There were significant differences in the density between slope positions averaged across all sites. Sites with the most recent and frequent fires did not have any of the three ericaceous shrubs collected at the slope bottom or ridge-top. At the most fire-suppressed site Ericaceae are present at every slope position. Age structures reveal that the oldest Ericaceae are found at the mid-slope positions while the age of thickets appears to decrease away from the mid-slope position. This pattern suggests that Ericaceae are moving into slope positions where they were previously less abundant. Sites with the most recent frequent fire regime seem to have prevented Ericaceae from heavily inhabiting high and low topographic positions while also reducing the overall basal area and density of Ericaceae.