Prescribed fire effects on erosion parameters in a perennial grassland

Published source details O'Dea M.E. & Guertin D.P. (2003) Prescribed fire effects on erosion parameters in a perennial grassland. Journal of Range Management, 56, 27-32.
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Summary

In USA, following many years of fire suppression, prescribed burning is being reintroduced to some grasslands as a means of habitat management and restoration. Concerns however have been raised that inappropriate burn times may increase erosion especially in semi-arid areas, in the interim period between vegetation denudation immediately post-burn to vegetation recovery. A 2-year experiment was undertaken to assess the effects of a late-spring burn and summer rainfall on seasonal runoff and erosion of semi-desert grassland at The Elgin study area (31°62 N, 110°52'W), southern Arizona.

The study area (1-3% slope) comprised perennial bunchgrasses (dominant grass genera were Eragrostis, Bouteloua, Lycurus and Muhlenbergia) with oak Quercus woodland in drainages. Livestock had been excluded for 30 years.

Six blocks each comprising four (3 x 10 m) subplots with sediment catchments (metal boxes set into the ground at the base of each plot) were installed on a hillslope. The four treatment variations applied were: a control, a prescribed burn, a rainfall simulation, and a rainfall simulation plus prescribed burn.

Burns were applied in late May 1998. At the end of June 1998, a simulated summer rainfall event was applied to assigned plots (63.5 mm/h for 40 min, average depth 43 mm) using a rotating-boom rainfall simulator.

Sampling points were established within each subplot to measure grass and herb (e.g. cover and grass basal area), soil and hydrologic (e.g. bulk density, erosion, runoff volumes and water intake rates) variables in response to treatments, after the summer growing seasons of 1998 and 1999.

Perennial grass cover was much reduced in the two burn treatments (1998: control 20%, burn 9%, rain 30%, rain + burn 11%; 1999: control 32%, burn 19%, rain 31%, rain + burn 15%). Annual dicots on the other hand increased (in 1998 being lowest in the controls (0.9%) and highest in rain + burn (3.2%); in 1999 lowest in rain only (3.8%) and highest in burn only (10.1%)). However, total average plant cover (and grass basal area, especially marked in burn + rain) was clearly reduced in the burn plots.

Increased bulk density, erosion and runoff, and lower water intake rates were all apparent in burned plots following the 1998 summer. In 1999, higher bulk density, runoff volumes and erosion were again observed within burned plots, as well as lower aggregate stability and water intake rates.

The results indicate that following late-spring burning, semi-desert grasslands are susceptible to greater summer runoff and erosion compared to unburned areas.

Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: https://www.uair.arizona.edu/holdings/journal/issue?r=http://jrm.library.arizona.edu/Volume56/Number1/