Masters Theses

Date of Award

8-2021

Degree Type

Thesis

Degree Name

Master of Science

Major

Forestry

Major Professor

David S. Buckley

Committee Members

Monica Papes, Lisa I. Muller

Abstract

Structural complexity has an important influence on wildlife habitat and several other ecosystem services. Establishment of white oak (Quercus alba) intercropped with loblolly pine (Pinus taeda), shortleaf pine (Pinus echinata), or eastern white pine (Pinus strobus), in 2014 provided the opportunity to investigate effects of planting species mixtures in different spatial arrangements on structural complexity. Terrestrial LiDAR was used to evaluate the structure of each intercropped treatment and monoculture control. The measures of complexity included: 1) rumple 2) top rugosity 3) standard deviation of individual tree crown area, 4) standard deviation of maximum tree heights, 5) standard deviation of total number returns associated with trees, 6) standard deviation of LiDAR returns associated with trees across 0.5m vertical layers, and 7) standard deviation of 0.5 x 0.5 x 0.5m voxel by the number of returns at 0.5m vertical intervals. In addition, mean maximum tree height, individual tree crown area, mean of 95th percentile of returns, and the mean number of returns by tree height were analyzed. The following three hypotheses were tested: 1) oak and pine mixtures would have greater structural complexity than monocultures, 2) white oak and loblolly pine would have greater structural complexity than other mixtures, and 3) complexity would be greater in treatments with a 0.31m spacing than in those with a 1.74m spacing. Significantly greater complexity in the mixtures than in oak monocultures partially supported the hypothesis that oak and pine mixtures would have greater structural complexity. The lack of significant differences between the complexity of mixtures and pine monocultures, however, suggests that the pines were more important in contributing to complexity than white oak. According to most measures of variability, mixtures with loblolly pine and loblolly pine monocultures had the greatest structural complexity; supporting the hypothesis that white oak and loblolly pine would have greater structural complexity. The hypothesis that complexity would be greater in treatments with a 0.31m spacing was not supported. The importance of loblolly pine in this study suggests that fast-growing species can influence structural complexity as much or more than the number of species planted.

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