Date of Award

8-2021

Degree Type

Thesis

Degree Name

Master of Science - Environmental Sciences

Department

Environmental Science

First Advisor

Dr. Brian P. Oswald

Second Advisor

Dr. Kenneth Farrish

Third Advisor

Mr. Tyson Hart

Abstract

This study focused on whether prescribed burning affects soil physical and chemical properties, especially water infiltration, in Western Gulf Coast forests. Soil water infiltration rates were measured 1) pre-burn (before the fire), 2) post-burn (one month after the fire), and 3) at vegetation green-up (three months after the fire). Soil samples were also collected to determine the effects of prescribed burning on soil pH, bulk density, particle density, pore space, soil strength, O-horizon weight and depth (organic matter), water stable aggregates, and soil fertility. This project was conducted on two different burn intervals. The National Forests and Grasslands of Texas (NFGT) of the United States Forest Service burns, perform prescribed burns every two to three years, predominantly during the dormant season. The Winston 8 Land and Cattle Ltd. Tree Farm, south of Nacogdoches, Texas, is often burned biannually during the dormant season, but occasionally during the growing season. The study was aimed at developing an understanding of any correlation between the soil physical and chemical properties among the burn intervals and between different time frames and the effects prescribed burning has on them. Very little research has been done to determine the effects of prescribed fire on soil water infiltration rates, and none have been done in the forests of the Western Gulf Coast or in Texas. All soils in the study were sand and loamy sand surface soil texture classes, because surface soil textures were so similar, it was assumed texture would not greatly affect the results in this study. SAS was used to determine the effects of prescribed burning between three different time spans (pre-burn to post-burn, post-burn to green-up and pre-burn to green-up), and between two different burn intervals, National Forest and Grasslands of Texas mean three-year interval and Winston 8 Land and Cattle Ltd. Tree Farm annual interval (National Forest and Winston 8). There was a significant increase in soil water infiltration rates between pre-burn to post-burn and pre-burn to green-up time frames, and between the two different burn intervals. The soil strength initially decreased slightly, but increased over time. Soil stable aggregates increased significantly over time, leading to an increase in soil structure after burning. This study found there could be short-term responses on soil physical and chemical properties from repeated burning treatments. Soil physical properties which significantly changed due to this prescribed burn include soil bulk density, pore space, water stable soil aggregates, and soil strength. Soil properties which significantly changed due to this prescribed burn include nitrogen in the forms of ammonium and nitrate, the carbon to nitrogen ratio, and electrical conductivity. Based on these results, these burn intervals do not change the availability of nutrients within the soil.

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

Available for download on Thursday, July 28, 2022

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