The Influence of Fluvial Geomorphic Processes on Spatial Patterns of Forest Primary Succession

I investigated spatial patterns of tree species in primary successional forests along depositional point bars at river bends of the Bogue Chitto River, Louisiana, USA and on nine additional rivers in the southeastern US. I hypothesized that geomorphic processes associated with river planform cause patterns of tree species to vary predictably along point bars as well as with increasing age of land during forest primary succession. By mapping trees and seedlings I determined that common canopy species in the first stage of succession were located predictably along either an upstream or downstream segment of each point bar in association with elevation, a correlate to hydroperiod. I conducted a three-year field experiment to test the relative effects of physical flood damage, inundation, and soil moisture on locations of seedling emergence and survival, with measured environmental variables as covariates. Availability of soil moisture was the most important limitation to seedling survival. Cohorts of seedlings were followed for four years to test the relationship between seedling survival and patterns of tree species. Mortality during the first year limited individuals to their species-specific long-term locations along point bars. Patterns of recruitment along point bars were consistent among years and among river bends in the reach. I developed a multi-species demographic model to test the predictability of demographic processes during succession. Patterns of establishment along the point bar, as well as community changes with time, have been fairly consistent during the past 60 years of succession, although relative abundance of species within stages may fluctuate through time. Surveys of ten rivers in the southeastern US coastal plain revealed that seven have the predicted pattern of tree species. Analysis of aerial photographs and hydrographs suggested that intermediate stream energy level, single channel meandering planform, high precipitation, and naturally fluctuating hydrolographs predict the predicted pattern of species. My research applied a multi-scale and interdisciplinary approach to identify causes of a previously unstudied complex but predictable pattern of primary succession characterizing rivers in a large physiographic region.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Plant Biology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Robertson, Kevin Matthew

Contributors dc:contributor

• Augspurger, Carol K.

• Agriculture, Forestry and Wildlife

Language dc:language

eng

Identifier

(MiAaPQ)AAI3017197

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/87022