Forest dynamics in the Virginia piedmont

Tree growth, as recorded in the width of annual increments, is a function of multiple factors including species biology, climate variation, and forest disturbance. This dissertation investigates the degree to which these factors control the growth of trees and the subsequent dynamics of forests in the Virginia piedmont. The main thesis of this research holds that these three factors structure not only the temporal patterns of tree growth but also the larger-scale spatial patterns, as recorded in the spatial distribution, structure, and composition of forest stands. To evaluate this thesis, forest stands are surveyed at Montpelier, Sweet Briar College, and Cumberland State Forest. Of these forests, the National Natural Landmark Forest at Montpelier provides an ideal setting for the characterization of both the influence of climate and disturbance on tree growth and serves as the central site for this research. Analysis of climate reconstructions from white oak tree-ring data demonstrates that summerwood responds to early summer precipitation while springwood responds to prior fall precipitation. Comparison of these reconstructions with meteorological diaries recorded by the Madison family suggests an unexpected shift in the seasonality of these correlations to earlier in the calendar year, possibly arising from a concurrent shift in the seasonality of precipitation at Montpelier. Analysis of disturbance history at Montpelier shows episodes of synchronized canopy releases of white oak trees and periods of establishment by early successional species that coincide with known changes in land use or ownership; however, the forests at Montpelier also contain trees pre-dating Madison family settlement. The overall spatial pattern of trees across all three forests shows a transition from a clumped understory to a uniformly distributed overstory. An individual-based model, sensitive to both soil IV moisture and light availability, replicates both the change in species composition across these sites and the spatial distribution of trees within these sites, supporting the thesis that climate and disturbance, through soil moisture and light availability, also structure the spatial patterns of these forests. In turn, this model may now serve as a tool for simulating the temporal response of tree rings and evaluating hypothetical manipulations of these factors.

Note: Abstract extracted from PDF file via OCR.

Digitization of this thesis was made possible by a generous grant from the Jefferson Trust, 2015.

Thesis originally deposited on 2016-02-18 in version 1.28 of Libra. This thesis was migrated to Libra2 on 2017-03-23 16:33:47.