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.
","abstract_html":"<p>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 (<em>Pinus Taeda L.</em>) 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 (R<sup>2</sup>), 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. </p>","abstract_has_math":false,"creators":["Edo-Iyasere, Osakpamwan"],"institution":null,"degree_name":"Master of Science - Environmental Sciences","degree_level":"Thesis","degree_discipline":"Environmental Science","degree_department":null,"school":null,"contributors":["Dr. Yuhui Weng","Dr. Rebecca Rollins","Dr. Kenneth Farrish"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2020,"date_issued":"2020-08-05T07:00:00Z","date_published":"2020-08-05T07:00:00Z","updated_at":"2026-07-24T04:30:30Z","subjects":["height-age relationship","site index","growth and yield modeling","soil and climate","loblolly pine plantations","Biostatistics","Environmental Sciences","Forest Sciences"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholarworks.sfasu.edu/etds/345","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Dr. Yuhui Weng","Dr. Rebecca Rollins","Dr. Kenneth Farrish"]},{"key":"dc:creator","label":"Author","values":["Edo-Iyasere, Osakpamwan"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2020-09-02T07:00:00Z"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Environmental Science"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science - Environmental Sciences"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["height-age relationship","site index","growth and yield modeling","soil and climate","loblolly pine plantations","Biostatistics","Environmental Sciences","Forest Sciences"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarworks.sfasu.edu/etds/345"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["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.
"]},{"key":"dc:title","label":"Title","values":["THE INFLUENCE OF ENVIRONMENTAL VARIABLES ON THE HEIGHT GROWTH OF LOBLOLLY PINE (Pinus taeda) IN THE WESTERN GULF"]}]}],"canonical_facts":{"dc:contributor":["Dr. Yuhui Weng","Dr. Rebecca Rollins","Dr. Kenneth Farrish"],"dc:creator":["Edo-Iyasere, Osakpamwan"],"dc:date.available":["2020-09-02T07:00:00Z"],"dc:description.abstract":["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.
"],"dc:identifier":["https://scholarworks.sfasu.edu/etds/345"],"dc:subject":["height-age relationship","site index","growth and yield modeling","soil and climate","loblolly pine plantations","Biostatistics","Environmental Sciences","Forest Sciences"],"dc:title":["THE INFLUENCE OF ENVIRONMENTAL VARIABLES ON THE HEIGHT GROWTH OF LOBLOLLY PINE (Pinus taeda) IN THE WESTERN GULF"],"thesis:degree_discipline":["Environmental Science"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["Master of Science - Environmental Sciences"]},"updated_at":"2026-07-24T04:30:30Z"}