Response of 2 semiarid grasslands to cool-season prescribed fire

Abstract

Woody perennials have invaded semiarid grasslands throughout the Southwestern United States. This invasion was coupled with decreased grass cover and increased runoff and soil erosion. Fire, which was a natural force that shaped and maintained the grasslands, is a management tool that may aid in restoring and maintaining grass cover. However, fire also poses the risk of increasing erosion and further soil degradation because protection afforded by vegetation is reduced immediately after the fire. Using a randomized block study design, this study measured vegetation cover, soil potentially mineralizable N, and erosion associated with the first application of prescribed fire on 2 semiarid grasslands. The potential for adverse effects from these fires was great because the fires occurred at the beginning of a drought period. However, the effects of the burn were minor relative to the effects of the drought, which caused the greatest change. Grass cover on the burn plots was nearly equal to grass cover on the controls 1 year after the fire. After 2 growing seasons, grass cover was equal on the control and burn plots. Potentially mineralizable soil N and sediment transport were similar on the control and burned plots during the 2 years following the fire. Thus, prescribed fire for reducing the cover of woody perennials may not increase the risk of site degradation over that caused by drought and weather fluctuations.

Modeling climate change effects on runoff and soil erosion in southeastern Arizona rangelands and implications for mitigation with conservation practices

“…Many studies have found that less-costly prescribed fire, in combination with managed grazing and herbicide applications, can effectively reduce mesquite canopy cover and control invasive species for maintenance of local grasslands (Wright and Bailey 1982;Teague et al 2010). In shrubinvaded grasslands of the southwestern United States, prescribed burning treatments have in some cases effectively eliminated mesquite and enhanced grass recovery by resulting in high shrub mortality and reducing competition for shallow soil moisture, eventually reducing erosion loss (Cable 1967;Martin 1983;DeBano et al 1998;White and Loftin 2000;Parmenter 2008;Ravi and D'Odorico 2008). However, it is important to point out that present notions of best management practices might be inadequate for future planning because they draw heavily from our past knowledge.…”

Applying Improved Estimates of MODIS Productivity to Characterize Grassland Vegetation Dynamics

“…Soil and vegetation sampling occurred within the middle 60-m by 60-m area within each plot to protect against edge effects. Within each plot, 3 permanently marked 60-m lines were used for vegetation cover and density measurements (White and Loftin 2000). Soils were collected by cover type (shrub, grass, or bare soil) along the 60-m lines.…”

“…Change in soil microtopography within each runoff collector was monitored using 2 soil erosion bridge locations established within the area of the runoff-sediment collectors prior to the burn (1 bridge location parallel to the top and 1 centered along the side of each collector; see White and Loftin [2000] for bridge description and image). The bridge used in this study has a center reference, which was created by placement of a nail with a receiving dimple beneath the middle hole of the bridge.…”

“…Managers need to understand the duration and magnitude of potential erosional loss to best use their available management tools. White and Loftin (2000) reported on the effects of the first application of prescribed fires on sediment transport, changes in soil surface elevations, vegetation cover, and potential soil fertility at two grassland sites in New Mexico. Although the fires reduced vegetation cover, fire was not the major factor controlling erosional loss.…”

“…Each of the 2 grasslands reported by White and Loftin (2000) have experienced 1 additional fire; another cool-season prescribed fire at one site and a warm-season wildfire at the other. The original objective of this research was to document the effects of multiple cool-season fires in 2 semiarid grasslands on vegetation cover type (grass, shrub, or bare ground), potentially mineralizable N (as a measure of site fertility), and soil erosion or building processes.…”