Date of Award

Summer 8-5-2020

Degree Type


Degree Name

Master of Science - Environmental Sciences


Environmental Science

First Advisor

Dr. Yuhui Weng

Second Advisor

Dr. Rebecca Rollins

Third Advisor

Dr. Kenneth Farrish

Fourth Advisor

Dr. Sheryll Jerez


Understanding the effects of environmental factors on stand growth is important in optimizing forest management plans. This study investigated the effects of soil and climate factors on the height growth (site index) of loblolly pine (Pinus Taeda L.) using data collected from permanent plots established in intensively-managed plantations across East Texas and Western Louisiana. The Chapman-Richards model was selected as the base model to describe the height-age relationships and important soil and climate variables were incorporated into the models as model parameter coefficient adjustors. Our results showed that the most important factors for predicting site index were nitrogen content of B horizon for soil and precipitation in spring and fall. Three models were developed, with one incorporating nitrogen of B horizon, one incorporating spring and fall precipitation, and the last one incorporating both the soil and climate variables. An increase in nitrogen content in B horizon and an increase in spring precipitation increased the tree height, but an increase in fall precipitation slowed tree height growth. The log-likelihood ratio tests showed that all three models had significantly smaller AIC than the base model. Compared to the base model, the three models also had larger model coefficient of determination (R2), smaller root mean squared error, and bias. All three models can be used to estimate site index of intensively-managed loblolly pine plantations in the region, but data used in this study were not large, and, therefore, caution should be taken in their application.

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.



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