Wildfire and Soil Microflora

Following the Rockhouse Fire, the Mimms Ranch was the site of a study on the effects wildfire on soil microflora. Soil microflora are essential for rangeland health but often overlooked in discussions.  Microflora within soil-surface communities create conditions favorable for rainfall infiltration, and consequently decreased runoff, as well as for retention of seeds and organic matter.

Research was conducted to describe the microflora to the genus level for three distinct ecological zones:  1) burned, 2) grazed, and 3) control areas.  Heavily grazed sites were included since they have been disturbed to a degree analogous to that associated with the intensity of the Rockhouse Wildfire.  Vegetation transects were conducted within each ecological zone following the fire and severe drought of 2011 and before summer precipitation of 2012. DNA extraction was used to assess microbial communities of the soil during the post-fire growth season.  Results indicated 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 were strongly correlated.  This research will serve as a baseline for future studies to allow land managers to better understand what affects soil microbial communities in semi-arid environments and how this in turn affects the overall health of the rangeland.

One of the study sites.  Early summer (above) & later summer (below), both about one-year post wildfire.

 

study sites

Nine study sites included burned areas within the red polyline, unburned within the blue, and trampled within the yellow.  (City of Marfa visible at bottom, right.)