Date of Award

1981

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

Abstract

Baldcypress (Taxodium distichum L. Rich.) is a desirable species for tree ring studies due to its longevity, resistance to decay, and the statistical characteristics of the ring record (Bowers, 1973). This investigation endeavors to determine: (1) the type and number of samples needed for such studies; (2) the values of x-ray densitometry analysis with the species; (3) the usefulness of the data for delineating differences in swamp sites which differ in length of flooding and if these differences could affect wood quality; and (4) the appropriateness of the data from disturbed swamp sites in south Louisiana to dendroclimatic studies. Differences exist in eight sample types. Furrow samples have a large number of missing and/or merging growth rings, are difficult to measure, and their statistical characteristics are no better than those of lobe samples. Compass direction is not significant but south samples contain twice as many resinous bands. Over 50% of the chronology variance is accounted for by differences among core chronologies. Thus, it is beneficial to take two or more samples per tree. A sample size of 120, four cores from thirty trees, is required to reduce the standard error of the sample mean to .05 or less. X-ray densitometry did not alleviate problems with crossdating and false rings which are common with baldcypress. Although statistical characteristics of the density parameters do not indicate their use in dendroclimatic studies, the density data are significantly correlated with both mean monthly precipitation and temperature. A shift in hydrology from permanently to seasonally flooded enhanced wood production in good years; and, maximum latewood became more homogeneous among trees. Wide rings are characterized by increases in density and more abrupt ring profiles. Maximum latewood and minimum earlywood vary together; the greatest difference in ring uniformity is due to changes in maximum latewood. The statistics generated indicate that dendroclimatic studies of baldcypress in south Louisiana should prove fruitful. Evidence demonstrates that the species will be useful in analyzing regional anomalies, such as the low winter temperatures of the 1960's and 1976-79, and that baldcypress data may be able to be pooled with data from other species.

Pages

175

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