Date of Award

Fall 12-1-2008

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geography, Geology, and Anthropology

First Advisor

Susan M. Berta

Second Advisor

Gregory D. Bierly

Third Advisor

S. Brian Ceh

Abstract

Hurricanes are a relatively common occurrence along the gulf coast of Texas. This research analyzed the effect hurricanes have on the growth and structure of forests in southeastem_Texas. Increment cores were taken from numerous species within the Neches Bottom Unit of the Big Thicket National Preserve and the Wier Woods Nature Preserve to analyze how hurricanes affect the structure of these forests. In the Turkey Creek Unit of the Big Thicket National Preserve and in the Angelina National Forest, Pi nus palustris (Longleaf pine) and P. taeda (Loblolly pine) was sampled in order to analyze how hurricanes affect the growth and persistence of these trees at their ecological limit. Ninety-four trees were analyzed to determine the effect of hurricanes on structure. Establishment dates of numerous samples at both the Neches Bottom U11it and Wier Woods Nature Preserve coincided with hurricane events which occurred from 1854 to 1963. Various other samples had establishment dates which occurred either one year prior or within five years after an event. When species composition was analyzed, an increase in the number of shade-tolerant species paired with little opportunity for recruitment of shade-intolerant species suggests that hurricanes are accelerating successional trends in both sites. The combination of establishment dates and species composition suggests that hurricanes play a vital role in determining the overall structure and future of these forests. Additionally, a number of species in this research were successfully cross-dated for the first and used for dendroecological analysis. IV In the Angelina National Forest and the Turkey Creek Unit of the Big Thicket National Preserve, 154 samples were analyzed to determine how the climate of southeastern Texas affects the growth of P. palustris and P. taeda at their western most ecological extent. Additional analysis was performed to determine what effect late season precipitation from hurricane events has on the annual growth of these species. Climatic analysis found that drought and late-season moisture availability were the most significant variables determining annual growth in P. palustris. When compared to known drought events, significant decrease in annual growth was found in all P. palustris sites. However, P. taeda was less affected by drought, and in fact showed significant increases in growth the year following a know drought event. When compared to historical hurricane events, the effect on annual growth showed mixed results. P. palustris sampled in the Angelina National Forest (Angelina Wilderness Area) and the Turkey Creek site showed significant increases in growth, particularly in the latewood growth, on hurricane years. No increase was seen in the remaining P. palustris stand in the Angelina National Fores't or in the P. taeda stand in the Turkey Creek Unit. Differences in substrate and understory vegetation could affect the retention of soil moisture muting the benefits in these stands.

Download

Share

COinS