Influence of fire and drought on soil surface microbial communities in the Marfa grasslands, Presidio County, Texas

by Ohnishi, Masahiro, M.S., SUL ROSS STATE UNIVERSITY, 2013, 114 pages; 1525046


The Rock House Fire that occurred April 9, 2011 burned 90% of the Mimms Ranch west of Marfa, Texas. Lack of natural resources for animals and plants due to this wildfire and the exceptional drought conditions of 2011 caused environmental changes in West Texas. Microflora in soil-surface communities, essential to overall rangeland health, were impacted by the fire and drought. Recovery of the grassland ecosystem from these disturbances is strongly linked to soil health. Three distinct ecological zones were analyzed: 1) burned, 2) grazed, and 3) control areas. All sites were located within the Hippo-Fomile soil series. DNA extraction of soil was used as a measure of soil biomass. Quantitative-Polymerase Chain Reaction (qPCR) was utilized to compare total microbial consortia in the post-fire growth season. Quantification included several primer sets targeting different functional metabolic genes. Next-Generation Sequencing (NGS) was performed as the most efficient method to observe microbial diversities. Data suggests a global reduction of total microbial numbers across all different metabolic strategies in the burned areas. Results indicate that fire had an impact in terms of the relative frequency, canopy cover, and basal cover of vegetation and microbial numbers in burned sites. Both vegetation and microbial numbers recovered after significant rainfall in 2012. Mean soil pH in burned areas was significantly higher (7.6) than in grazed (6.9) and control areas (6.4) due to the fire. Overall, relationships between soil surface microbial communities, physical and chemical soil properties, and vegetation communities are strongly correlated.

AdviserBonnie J. Warnock
Source TypeThesis
SubjectsConservation biology; Microbiology; Environmental management
Publication Number1525046

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