Micah D. Pace

Date of Award

2003

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Forest Resources

Advisor

Robert S. Seymour

Second Committee Member

Robert K. Shepard

Third Committee Member

Alan S. White

Abstract

There is little debate within the forest science community that leaf area (LA, the surface area of live foliage) or leaf area index (LAI, the total surface area of live foliage per unit of ground area) are important variables, central to enhancing the understanding of forest growth and many forest ecosystem processes. The ability to accurately measure LA1 has become a research priority and has resulted in various methods of estimation for a variety of species and regions. In this study LA estimation models for Pinus strobus L. were developed, tested, and compared across a wide range of densities for both thinned and unthinned stands in the Penobscot River Valley of central Maine. Test plots were located within a 52-year-old plantation. Direct LA1 estimations from litterfall were used to compare the indirect estimations of below-canopy light interception and various allometric models. Four treelevel models were developed through non-linear regression and compared at both treelevel and stand-level. Two models utilized sapwood area at breast height (SAbh) as a predictor variable and two non-sapwood models were based on basal area and a modified live-crown ratio (BA*mLCR). When compared to litterfall, LA1 measurements from light interception data yielded underestimates and overestimates in thinned and unthinned sites, respectively. However, the treatment-specific bias was masked when pooling the data and a relatively strong relationship with litterfall existed ( R ~ = 0.68). Among the allometric models, the SAbh models performed best showing no bias across stand densities. Estimations from BA*mLCR were in agreement with both litterfall and sapwood models within unthinned sites, but were biased, providing overestimations for thinned plots. The apparent bias in LA1 estimation from BA*mLCR was caused by the model's high sensitivity to the limited range of large trees sampled for equation development. Basal area at breast height was particularly influential. However, when sapwood-derived coefficients were used, an adjusted BA*mLCR equation performed well across the range of stand densities and provided accurate LA1 estimations when referenced to litterfall and sapwood-based estimations.

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