#629 Environmental Management (2009) 44:84–92 DOI 10.1007/s00267-008-9258-4 Influence of Mowing Artemisia tridentata ssp. wyomingensis on Winter Habitat for Wildlife Kirk W. Davies Æ Jonathan D. Bates Æ Dustin D. Johnson Æ Aleta M. Nafus Received: 8 August 2008 / Accepted: 14 December 2008 / Published online: 22 January 2009 Ó Springer Science+Business Media, LLC 2009 Abstract Mowing is commonly implemented to Artemi- characteristics. Because of the large reduction in A. sia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. tridentata spp. wyomingensis for potentially 20 years fol- Welsh (Wyoming big sagebrush) plant communities to lowing mowing, mowing should not be applied in improve wildlife habitat, increase forage production for Artemisia facultative and obligate wildlife winter habitat. livestock, and create fuel breaks for fire suppression. Considering the decline in A. tridentata spp. wyomingensis- However, information detailing the influence of mowing on dominated landscapes, we caution against mowing these winter habitat for wildlife is lacking. This information is communities. crucial because many wildlife species depended on A. tridentata spp. wyomingensis plant communities for winter Keywords Wyoming big sagebrush Á Recovery Á habitat and consume significant quantities of Artemisia Sagebrush Á Mechanical treatment Á Cover Á during this time. Furthermore, information is generally Nutritional quality Á Crude protein limited describing the recovery of A. tridentata spp. wy- omingensis to mowing and the impacts of mowing on stand structure. Stand characteristics and Artemisia leaf tissue Introduction crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber (NDF) concentrations were measured in Artemisia tridentata Nutt. (big sagebrush) plant commu- midwinter on 0-, 2-, 4-, and 6-year-old fall-applied nities occupy vast portions of the western United States mechanical (mowed at 20 cm height) treatments and (Ku¨chler 1970; Miller and others 1994; West and Young compared to adjacent untreated (control) areas. Mowing 2000). These communities provide important habitat for compared to the control decreased Artemisia cover, den- wildlife and forage for domestic livestock. Prior to Euro- sity, canopy volume, canopy elliptical area, and height pean settlement, wildfires periodically shifted dominance (P \ 0.05), but all characteristics were recovering from A. tridentata to herbaceous vegetation and created a (P \ 0.05). Mowing A. tridentata spp. wyomingensis plant mosaic of habitats across the landscapes (Miller and He- communities slightly increases the nutritional quality of yerdahl 2008; Miller and Rose 1999; Wright and Bailey Artemisia leaves (P \ 0.05), but it simultaneously results 1982). With the decrease in fire return intervals in some A. in up to 20 years of decrease in Artemisia structural tridentata plant communities, increased levels of A. tridentata cover and density can reduce or eliminate the herbaceous component (West 1983). West (2000) esti- & K. W. Davies ( ) Á J. D. Bates Á A. M. Nafus mated that *25% of the A. tridentata steppe ecosystem is USDA—Agricultural Research Service, Eastern Oregon Agricultural Research Center, Burns, OR, USA comprised of decadent, even-aged stands of A. tridentata. e-mail: [email protected] Long-term maintenance in an A. tridentata state has also been demonstrated to reduce resistance to exotic plant D. D. Johnson invasions (Davies and others 2008). As a consequence, Department of Rangeland Ecology and Management, Harney County Extension Office, Oregon State University, there is a desire to increase the diversity of A. tridentata Burns, OR, USA structural characteristics and understory productivity across 123 Environmental Management (2009) 44:84–92 85 landscapes to provide a mosaic of various habitats (Beck Wambolt and Payne (1986) mowed A. tridentata at 5.1– and others, in press; Connelly and others 2000; Crawford 7.6 cm above ground level, which is very different than and others 2004). contemporary mowing projects designed to improve wild- Mechanical thinning of A. tridentata is a common life habitat. Contemporary mowing projects for wildlife are method for reducing its cover and density to increase implemented to thin A. tridentata stands and create diver- herbaceous production and habitat diversity (Dahlgren and sity in habitats, not eliminate (control) A. tridentata. In the others 2006; Hedrick and others 1966). Thinning A. northern Great Basin, mowing of A. tridentata is often at tridentata stands might be beneficial to some Artemisia 20 cm above ground level to increase the survival of young obligate wildlife species (Beck and Mitchell 2000; Craw- A. tridentata and decrease the potential for blade contact ford and others 2004). Stevens and Monson (2004) with surface rocks. Mueggler and Blaisdell (1958) reported recommended that the shrub overstory need not be elimi- that 3 years after chain roto-beating, A. tridentata pro- nated, but be reduced to lessen competition with understory duction was only 14% of the untreated area. Although not species. Advantages of mechanical thinning treatments conclusive, herbaceous species data from their study sug- over burning include the ability to retain shrub and her- gest that they were treating A. tridentata ssp. vaseyana baceous components while controlling the size and shape (Rydb.) Beetle (mountain big sagebrush) not A. tridentata of the treatment (Urness 1979). Mechanical treatments ssp. wyomingensis. Most previous literature focused on A. have been suggested to be more appropriate than burning in tridentata control, rather than thinning A. tridentata ssp. A. tridentata ssp. wyomingensis (Beetle & A. Young) S.L. wyomingensis. Welsh (Wyoming big sagebrush) communities to enhance Information is also lacking describing the influence of vegetation characteristics because A. tridentata probably mechanical treatment on the nutritional quality of A. has a more speedy recovery with mechanical treatments tridentata ssp. wyomingensis leaves. The nutritional quality (Beck and others, in press; Watts and Wambolt 1996). of A. tridentata is important for many wildlife species that However, the impact of mechanical thinning A. triden- consume Artemisia. Centrocercus urophasianus (sage- tata ssp. wyomingensis on winter habitat for wildlife has grouse) diets consist almost exclusively of Artemisia leaves not been evaluated. A. tridentata ssp. wyomingensis plant in the winter (Patterson 1952; Wallestad and others 1975), communities provide important winter habitat to many the total diet of Antilocapra americana (pronghorn ante- wildlife species because these plant communities are often lope) in Oregon contained about 61% Artemisia (Mason at lower elevations and experience warmer temperatures 1952), and A. tridentata can comprise more than 50% of and less snow accumulation than more productive adjacent Odocoileus hemionus (mule deer) diets in January and summer habitats (Burke and others 1989; Connelly and February (Austin and Urness 1983). Mechanical treatment others 2000; Homer and others 1993; Shiflet 1994). The might influence leaf nutritional quality by decreasing the length of recovery of A. tridentata ssp. wyomingensis is age of A. tridentata in the stand. Mature A. tridentata plants critical because it provides important hiding and thermal frequently suffer mortality from mechanical treatments, cover (Connelly and others 2000). A. tridentata ssp. wy- whereas younger, smaller individuals often survive omingensis is also an important dietary component for (Wambolt and Payne 1986). Wambolt (2004) reported many wildlife species during the winter (Austin and Urness higher crude protein content in juvenile compared to mature 1983; Patterson 1952; Wallestad and others 1975). A. tridentata ssp. wyomingensis plants, but crude protein Information describing recovery and structural charac- content of other A. tridentata subspecies did not differ by teristics of mechanically thinned A. tridentata ssp. age. Younger plants are generally more nutritious than older wyomingensis is lacking. Historic mechanical treatments of individuals (Marschner 1998). To better understand the A. tridentata were implemented to control A. tridentata, implications of mechanical treatment of A. tridentata on not to thin stands; for example, the objectives of Wambolt winter habitat, the impacts of mowing on the nutritional and Payne (1986) and Mueggler and Blaisdell (1958) were quality of A. tridentata leaves needs to be investigated. to remove A. tridentata as close to ground level as possible. The purpose of this study was to evaluate the recovery Wambolt and Payne (1986) reported that mechanical con- and affects of mowing A. tridentata ssp. wyomingensis on trol treatment of A. tridentata ssp. wyomingensis resulted in stand characteristics during the winter. The objectives of 13–15 years of lower A. tridentata cover relative to this study were to (1) quantify the influence of mowing on untreated areas. However, the A. tridentata cover in the A. tridentata ssp. wyomingensis stand characteristics, (2) untreated areas decreased drastically during the study and, determine the recovery of A. tridentata ssp. wyomingensis thus, A. tridentata cover in the treated areas might take following mowing, and (3) ascertain if mowing influences even longer to recover. Wambolt and Payne (1986) also did nutritional quality of A. tridentata ssp. wyomingensis leaf not report treatment effects on A. tridentata density, height, tissue [crude protein (CP), acid detergent