Volumes 100–101, January–February 2014, Pages 78–88
Prescribed fire effects on resource selection by cattle in mesic sagebrush steppe. Part 1: Spring grazing ☆
Highlights
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- Beef cows were GPS tracked 2 yrs prefire and 5 yrs postfire on sagebrush steppe.
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- A resource selection function accurately predicted prefire and postfire cattle use.
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- Slope and sagebrush cover were the primary drivers of prefire cattle use.
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- Prefire cattle were neutral towards areas later receiving light/moderate fire severity.
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- Cattle selected for lightly/moderately-burned areas for at least 5 years postfire.
Abstract
Prescribed
fire is commonly applied world-wide as a tool for enhancing habitats
and altering resource-selection patterns of grazing animals. A
scientific basis for this practice has been established in some
ecosystems but its efficacy has not been rigorously evaluated on mesic
sagebrush steppe. Beginning in 2003, resource-selection patterns of beef
cows were investigated using global positioning system (GPS) collars
for 2 years before and for 5 years after a fall prescribed burn was
applied to mesic sagebrush steppe in the Owyhee Mountains of
southwestern Idaho, USA. Resource-selection functions (RSF) developed
from these data indicated cattle selected for lightly to moderately
burned areas for all 5 postfire years. Cattle had been neutral towards
these areas prior to the fire when their distribution was primarily
affected by slope, sagebrush dominance, and distance to upland water.
Resource-selection responses to the fire lasted 2–3 years longer than
would be expected for fire-induced, forage-quality improvement effects.
Although this is a case study and caution should be taken in
extrapolating these results, if applied under conditions similar to this
study, livestock producers and natural resource managers can likely use
fall prescribed fire in the mesic sagebrush steppe to affect cattle
resource-use patterns for 5 years postfire.
Keywords
- Burning;
- GPS tracking;
- Habitat use;
- Livestock distribution;
- Modeling;
- Rangeland improvement
1. Introduction
Prescribed
fire is commonly applied to rangelands throughout the world as a tool
for enhancing habitats and managing resource-selection patterns of
grazing animals (Butz, 2009, Pyne, 1995 and Wikeem and Strang, 1983).
A scientific basis for this management practice has been established in
montane grasslands, tall grass prairie, mixed prairie, shortgrass
prairie, shrub steppe, and savanna (Augustine et al., 2010, Bates et al., 2009, Hobbs and Spowart, 1984, Klop et al., 2007, Peek et al., 1979 and Vermeire et al., 2004).
The sagebrush-steppe ecosystem occupies about 44.4 million ha in
western North America. Higher elevation, mesic communities, dominated by
mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyanna Beetle) and/or antelope bitterbrush (Purshia tridentata
[Pursh] DC), form a substantial proportion of the sagebrush steppe and
serve as principal livestock grazing areas. Despite their prominence,
use of prescribed fire for managing resource selection by livestock has
never been rigorously evaluated on mesic sagebrush steppe rangelands.
Fire
has always played an important ecological role, promoting heterogeneity
on mesic sagebrush steppe rangelands. Prior to settlement, natural
ignitions temporally converted areas of sagebrush-grassland to perennial
grassland. Fire-killed sagebrush and bitterbrush eventually regrew,
principally from seed, and returned the landscape back to
sagebrush-grassland (Lesica et al., 2007). Fire also killed fire-sensitive, tree species like western juniper (Juniperus occidentalis Hook.) which tend to encroach into mesic sagebrush steppe ( Miller and Rose, 1999).
Modern introductions of highly-flammable, exotic invasive plants like cheatgrass (Bromus tectorum L.) and medusa head (Taeniatherum caput-medusae
[L.] Nevski) have increased fire frequencies in some areas and raised
concerns about the modern role of fire in the sagebrush steppe ( Whisenant, 1989, D’Antonio and Vitousek, 1992, Brooks et al., 2004 and Pierson et al., 2011). However, while fire in the lower-elevation, more arid portions of the sagebrush steppe (e.g., Wyoming big sagebrush [A. tridentata Nutt. ssp. wyomingensis
Beetle]-dominated communities) may cause severe degradation by
converting sagebrush-grasslands into annual grasslands dominated by
cheatgrass, type conversions of this nature are not inevitable ( Davies et al., 2008) and are much less likely in the mesic sagebrush steppe where cheatgrass is less competitive with native perennial grasses ( Chambers et al., 2007).
In fact, within mesic sagebrush steppe, the concern is often about a
modern lack of fire rather too much fire. Fire suppression or exclusion
can lead to overmature, dense, excessively woody stands of mountain big
sagebrush and antelope bitterbrush. Lack of fire can also promote
encroachment of western juniper eventually resulting in a type
conversion from sagebrush-grasslands to dense woodlands ( Miller and Rose, 1999). Trees and shrubs can out-compete herbaceous plants for light, moisture, and soil nutrients ( Wrobleski and Kauffman, 2003).
Consequently, progression towards dense, overmature shrub stands or
juniper woodlands can dramatically reduce the vigor, productivity, and
availability of forage plant species important to rangeland livestock
and wildlife (e.g., mule deer [Odocoileus hemionus Rafinesque]) ( Miller et al., 2000).
Prescribed fire is increasingly being applied by nature resource
managers, to overmature stands of sagebrush or sagebrush stands
suffering from tree encroachment, to carefully restart a fire cycle
previously stalled by fire suppression. The intended purposes of these
prescribed fires are often manifold but commonly fire is applied to
improve livestock distribution.
Many factors affect livestock behavior and consequent resource-selection patterns (Bailey et al., 1996 and Senft et al., 1987). Vegetation composition, cover, and forage characteristics affect use patterns of grazing animals (Bailey, 1995, Ganskopp and Bohnert, 2009, Ganskopp et al., 1992, Gillen et al., 1984 and Howery et al., 1996).
Water and mineral sources, topography, weather, and site microclimate
also affect choice of foraging and resting areas, distance traveled
between these focus areas, and time spent in them (Bailey, 1995, Bailey, 2005, Bailey et al., 2008, Cook, 1966, Howery et al., 1998, Loza et al., 1992, Mueggler, 1965 and Senft et al., 1985).
To be effective, livestock management treatments, including prescribed
fire, must account for or work in concert with the most dominant of
these environmental factors.
The
intent of this research project was to evaluate spatial and temporal
effects of prescribed fire on resource selection, activity budgets, and
movement path characteristics of beef cattle in mesic sagebrush steppe
rangelands. Two studies were carried out where, the first evaluated
these cattle behavioral responses during spring (early May) just prior
to peak forage production and, the second was conducted mid-summer
(July) as forage plants began to senesce. The present paper presents
findings from the first study. Two additional papers in this series
present the findings from the mid-summer study and the results from
cattle activity budget and movement path evaluations of both studies.
Specific objectives of the spring grazing study were to: 1) model the
resource-selection responses of cattle to prescribed fire and
environmental factors; and 2) evaluate the efficacy of upland prescribed
fire application for managing cattle distribution.
