Greater sage-grouse (Centrocercus urophasianus) habitat response to mowing and prescribed burning Wyoming big sagebrush and influence of disturbance factors on lek persistence in the Bighorn Basin, Wyoming

My thesis work focused on evaluating the relative influence of prescribed burning (1990--1999 and 2000--2006) and mowing (2000--2006) treatments on the quality of greater sage-grouse (Centrocercus urophasianus ) nesting and early brood-rearing habitats and landscape characteristics that influenced sage-grouse lek persistence from 1980 to 2009 in the Bighorn Basin of north-central Wyoming. Objectives of treatments have focused on land health, watershed improvement, and to enhance habitat conditions for livestock, greater sage-grouse (Centrocercus urophasianus), and other wildlife. I focused on how prescribed burning and mowing may affect sage-grouse nesting and early brood-rearing habitats by evaluating habitat quality through insect, soil, and vegetation parameters at 30 treated sites compared to 30 nearby, untreated reference sites. My sites were classified by treatment type, soil type, season, and decade of treatment (sites burned in the 1990s and sites burned or mowed during 2000--2006). Prescribed burning greatly (--85.1 to --100%) reduced levels of sagebrush canopy cover at least 19 years postburn, while mowing maintained minimum levels of sagebrush canopy cover recommended for sage-grouse nesting and early brood-rearing habitats. In some cases, prescribed burning showed positive results for sage-grouse nesting and early brood-rearing habitats compared to mowing such as 6.3- to 16.9-times greater ant weights (mg/trap; on aridic burns during 1990s and ustic burns during 2000--2006 respectively), 2.3- to 85.1-times greater beetle weights (mg/trap) on ustic soils, 3.6- to 4.3-times higher perennial grass canopy cover on aridic soils, 2.6-times higher plant species richness on aridic soils during 2000--2006 burns, and 2.0- to 5.0-times higher soil nitrogen on burns during 2000--2006, but all of these characteristics were not found to be enhanced compared to reference sites. Mowing provided 3.6- to 13.2-times higher sagebrush canopy cover on ustic soils, 2.2- to 3.0-times higher sagebrush heights on aridic and ustic soils, and 1.2- to 1.5-times higher insect diversity on ustic and aridic soils than prescribed burning. When comparing mowed sites to reference sites, there was1.2- to 2.5-times higher litter and 3.5- to 9.1-times higher ant weights (mg/trap) at mowed sites. However, mowing did not promote an increase in other sage-grouse early brood-rearing needs such as the abundance of food forbs, abundance or weights of beetles and grasshoppers, or perennial grass canopy cover or height. Forb nutritional content and production were not enhanced (i.e., similar to reference sites) by either treatment. Perennial grass height and canopy cover (5 of 6 cases) were not enhanced through burning or mowing. The main benefit from prescribed burning was an increase in grasshopper abundance (no./trap) compared to reference sites (grasshopper abundance was 2.4- to 3.4-times greater at prescribed burned sites than reference sites). In general, results indicate few positive aspects of treating Wyoming big sagebrush to enhance habitat conditions for nesting and early brood-rearing sage-grouse as much as 19 years after prescribed burning and 9 years after mowing in the Bighorn Basin. Mowing, however, appears to be a better alternative than prescribed burning Wyoming big sagebrush, largely because it leaves intact sagebrush, but comparisons between reference sites typically did not suggest habitat conditions were enhanced through mowing. Consequently, managers contemplating these 2 treatment techniques to enhance sage-grouse habitats should consider other treatment strategies including non-treatment.;When evaluating factors that may have influenced the probability of sage-grouse lek persistence in the Bighorn Basin I found support for the synergistic influence of multiple disturbance factors influencing sage-grouse lek persistence. I predicted that increasing roads, energy development, and wildfire will result in loss of more sage-grouse leks in the Bighorn Basin. The Bighorn Basin has lower developed reserves of oil and gas than many other regions of Wyoming; however, my study supports findings from studies in those areas that demonstrate energy development negatively affects lek persistence. I recommend that conservation efforts should focus on minimizing well development and implementing wildfire suppression tactics within 1.6-km of active sage-grouse leks.