Author ORCID Identifier

https://orcid.org/0000-0002-6116-3925

Semester

Fall

Date of Graduation

2022

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Division of Forestry and Natural Resources

Committee Chair

Jamie Schuler

Committee Co-Chair

Bryce Adams

Committee Member

Bryce Adams

Committee Member

David McGill

Committee Member

Todd Ristau

Abstract

Forest management is a complex task that influences future site conditions for centuries. Therefore, forest managers utilize decision tools such as forest growth and yield models to aid in the decision-making process. These models allow managers to make reasonable assessments about future site conditions and to construct evidence-based management plans. SILVAH, which stands for SILViculture of Allegheny Hardwoods, is a decision tool for forest managers in Central Appalachia and was built by the U.S. Forest Service. It contains a growth and yield simulator that was developed in the late 20th century. This research sought to understand and examine the accuracy of SILVAH’s projections overtime and to develop and test newly parameterized equations as a comparison. The first half of this research concluded that SILVAH’s basal area projection accuracy was related to initial relative density of the stand as well as projection length. Basal area projection error ranged from 4% to 56% of the actual values. Furthermore, SILVAH tended to underpredict basal area than overpredict it. With regards to stand density (trees per acre), SILVAH’s accuracy was largely determined by projection length and, unlike basal area, SILVAH tended to overpredict density. The second half of this project sought to develop new five-year individual-tree growth and mortality models and to examine the factors that influence growth and mortality for nine different tree species groups utilizing 77,870 five-year observations on long-term research plots from the Kane Experimental Forest. Generalized linear mixed-effects models were used to model growth and mortality, accounting for repeat measurements and the hierarchical nature of the data. Final models were selected based on likely biological significance and fit statistics. Results showed that proxy measures for initial tree size and competition variables are highly important to both individual-tree growth and mortality. Validation tests of the new models revealed improvements over the models currently in SILVAH. In addition, predicted growth dynamics of multiple species was analyzed and indicated that birch species and oak species show distinct patterns under different levels of competition and initial tree size.

Embargo Reason

Publication Pending

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