Date of Award
Doctor of Philosophy
Dr. W. Thomas Straw
Dr. Alan Kehew
Dr. Alexander Enyedi
Increment core samples were collected and examined to test the hypothesis that the history of punctuated or intermediate-term changes in wetland soil-moisture conditions can be reconstructed from the annual growth-ring record of trees. The hypothesis is based on plant physiological principles that indicate a relationship between water surplus stress and impaired physiological activity that could lead to reduced growth.
Sampling sites were selected for their ostensible historic hydrologic variability and the availability of documentation of hydrologic disturbances. A conceptual model was developed by which trees were sampled along a hydrotopographic gradient for comparison of radial stem growth in uplands versus wetlands. In order to construct a protocol that could be practical for wetland scientists, cores were prepared for analysis using a simplified modification of existing techniques and growth rings were measured with common laboratory equipment Processed tree ring data were compared to independent documentation of hydrologic influence at the sample sites, where appropriate, including historical aerial photographs, gauged streamfiow and precipitation data. A variety of traditional dendrochronological data processing and analytical techniques and creative approaches were applied to the raw data to address the hypothesis.
The hydrologic signal was not strong in the observed wood samples and the hypothesis was therefore rejected. Pre-established analytical techniques were not Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. particularly useful for isolating the hydrologic variable from the data set Some improved resolution was made possible through techniques developed in this study, e.g., deviation from the growth mean and ring-width index subchronologies. Weakness in the water surplus stress-growth signal may be attributed in part to the ability of some tree taxa to physiologically compensate for periodic inundation or soil saturation. Attempts to enhance the ring definition of diffuse-porous tree species were unsuccessful; therefore, the incorporation of ubiquitous midwestem region forested wetland species, such as Acer saccharimm, were excluded from the dendrohydrologic analyses. Lessons learned from the successes and failures of this study suggest that, with some refinement, the technique that was developed has the potential to recognize hydrologic changes through tree growth observations in selected settings.
Hascall, Allan P. III, "Reconstruction of Wetland Hydrology Dynamics Using Tree Rings" (1997). Dissertations. 1632.