Date of Award

12-2021

Degree Type

Thesis

Degree Name

Master of Science - Forestry

Department

Forestry

First Advisor

Kathryn R. Kidd

Second Advisor

Jeremy P. Stovall

Third Advisor

Brian P. Oswald

Fourth Advisor

Steven B. Jack

Abstract

Riparian ecosystems are vital to the landscape, providing critical services including water filtration and purification, flood and erosion control, carbon sequestration, biodiversity support, and aesthetic value. Bottomland hardwood forests, however, are threatened by invasive species, land loss/conversion, inconsistent or absence of harvesting disturbances, and altered hydrological patterns, leading to reduced success of desired, native species. This research assessed regeneration dynamics and one-year survival in a seasonally-flooded bottomland hardwood forest at Boggy Slough Conservation Area in East Texas to identify abiotic and biotic factors important for successful establishment of native regeneration. Areas sampled included two that were previously treated with herbicide for Chinese tallow (Triadica sebifera L.) and one untreated, reference area.

Shade-tolerant species were, in general, more common in the regeneration layer than shade-intolerant species. Less-desirable native species, such as water-elm (Planera aquatica J.F.Gmel.) and American hornbeam (Carpinus caroliniana Walt.) as well as invasive tallow were present at higher densities than many desired species. Oak species had low sapling densities, indicating potential recruitment issues throughout much of the site. The results showed that seedling densities of some native species, as well as Chinese tallow, varied among treatment areas, and that new cohorts of tallow regeneration may have been facilitated in the post-treatment environment at the expense of certain native species. Overcup oak (Quercus lyrata Walt.) seedlings were most abundant in the reference area. Other native indicator species in both treated and reference areas were mid-tolerant to tolerant of shade. Abiotic and biotic factors, representing complex moisture, light, and ground cover gradients, were associated with regeneration abundances of native species differently across sapling (DBH 0.6 to 3.9 inches), large seedling (DBH < 0.6 inches, height ≥ 6 inches), and small seedling (DBH < 0.6 inches, height < 6 inches) size classes.

After one year, survival rates among native-hypogeal, native-epigeal, and invasive-Chinese tallow differed; Chinese tallow had a significantly lower survival rate than the native groups, likely as a result of weather events. Height and diameter increased the odds of survival for all regeneration groups. Additionally, vigor, down woody debris (DWD), microtopography, and canopy cover had varying influence among species groups. When significant, raised microsites increased odds of survival, while proximity to DWD and higher canopy cover decreased odds of survival. This research provided deeper insight into micro-site preferences of bottomland native tree species and which are projected to occupy the canopy in the future. To encourage regeneration of desired, native species, managers must be able to match species to site and create canopy openings sufficient to promote recruitment of native species without allowing competitive invasive species from claiming newly-available light and growing space.

Creative Commons License

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

Available for download on Friday, December 08, 2023

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