Quaking Aspen Ecology on Forest Service Lands North of Yellowstone National Park

Quaking aspen (Populus tremuloides) occupy a small area in the northern Rocky Mountains, but are highly valued as wildlife habitat. Aspen stands in and around Yellowstone National Park commonly consist of few, large, mature overstory stems and numerous root suckers that do not grow above the browsing reach (≈ 2 m) of most wild ungulates. Our primary objective was to determine if the recruitment or density of aspen stems \u3e 2 m tall had changed from 1991 to 2006 on a portion of the Gallatin National Forest. The same aspen stands were surveyed in 1991 and 2006 in the 560 km² study area (n = 316). Secondary objectives were to determine if aspen density was influenced by elk (Cervus elaphus) browsing, conifer establishment, and cattle (Bos spp.) grazing. Mean recruitment stem density did not change from 1991 to 2006 (P = 0.95). Density of stems \u3e 2 m declined 12 percent from 1991 to 2006 (P = 0.04), which indicates that recruitment stems are not being produced at a sufficient rate to replace aging overstories. Areas with the greatest elk densities had the lowest recruitment stem densities and contributed the most to the decline. Although elk browsing seemed to play the largest role, conifer establishment and cattle grazing have also negatively impacted overstory recruitment in aspen stands. Even though elk numbers on the Northern Yellowstone Winter Range have declined since wolf reintroduction, aspen recruitment has not increased at the landscape level on the Gallatin National Forest

Restoring Aspen Riparian Stands With Beaver on the Northern Yellowstone Winter Range

Aspen (Populus tremuloides) on the Gardiner Ranger District, Gallatin National Forest, have declined over the last half-century. In an attempt to reverse this trend, beaver (Castor canadensis) were reintroduced in Eagle Creek in 1991. In 2005, we assessed the long-term effects of beaver on aspen stands and the associated riparian area in the Eagle Creek drainage. Aspen recovery was estimated by comparing vegetative changes among control sites with \u3c10 percent beaver use\u3e(n = 5), active beaver sites (n = 6), sites abandoned for 1 to 3 years (n = 7), sites abandoned for 4 to 6 years (n = 4), and sites abandoned for 7 to 11 years (n = 5). Aspen stem densities in active sites and sites abandoned by beaver for 1 to 3 years were similar (2.6/m2) and greater (P = 0.01) than the remaining sites. Sprout and sapling densities were greater (P = 0.01) on active and sites abandoned for 1 to 3 years compared to the other sites. Aspen suckers were not able to grow taller than 2m on sites without beaver activity for 4 to 1 years, which prevented aspen recovery. Beaver activity stimulated the growth of aspen sprouts and saplings, but ungulate herbivory prevented successful aspen recovery in Eagle Creek

Converting Crested Wheatgrass Stands to Enhance Big Sagebrush: A Literature Review

Greater sage-grouse (Centrocercus urophasianus) is a high priority species for federal and state land management agencies. Sage-grouse are sagebrush (Artemisia spp.) obligates requiring sagebrush for their survival throughout the year. Sagebrush has been removed and replaced with crested wheatgrass (Agropyron cristatum & A. desertorum) throughout the West. The objectives of this paper were to review the literature (99 papers), as well as consult experts, to determine which methods are most likely to eliminate crested wheatgrass and establish sagebrush. No technique eliminates crested wheatgrass in a single application. Grazing and fire have no long-term impacts on crested wheatgrass. Mechanical treatments, such as plowing, disking, and cultivating reduce and eradicate crested wheatgrass, but a flush of invasive annual grasses following mechanical disturbance can make establishment of seeded species difficult. It appears that the best way to reduce crested wheatgrass cover and establish sagebrush is to spray crested wheatgrass with glyphosate in early spring for two consecutive years at a rate of 1.1 kg/ha of active ingredient. Then, sagebrush should be seeded in the late fall using a compact row seeder or Brillion cultipacker at a rate of 0.22 kg/ha pure live seed

Relationship of Wyoming Big Sagebrush Cover to Herbaceous Vegetation

We measured 328 sites in northern, central, and southern Montana and northern Wyoming during 2003 to test the relationship of herbaceous cover to Wyoming big sagebrush (Artemisia tridentata wyomingensis) cover. Long term annual precipitation at all sites was approximately 31 cm. Sagebrush and total herbaceous cover varied from 5 to 45 percent and 3.5 to 55 percent, respectively. Simple linear regression was the best fit model for predicting herbaceous cover from sagebrush cover using the highest Ra2 values as the model selection criteria. In northern Montana, herbaceous vegetation was predicted by sagebrush cover with the following model: Y = 37.4 – 0.61X (Ra2 = 0.16, P \u3c 0.001, n = 87). In central Montana, the model was Y = 14.0 – 0.00X (Ra2 = 0.00, P = 1.0, n = 155). In southern Montana, the model was Y = 35.9 – 0.39X (Ra2 = 0.14, P \u3c 0.001, n = 86). When all sites were combined, the best fit model was Y = 23.7 – 0.15X (Ra2 = 0.01, P \u3c 0.061, n = 328). This analysis determined that only 1 percent of the variation in herbaceous vegetation cover was associated with Wyoming big sagebrush cover. Management suggestions to reduce Wyoming big sagebrush in order to increase herbaceous production for greater sage-grouse (Centrocercus urophasianus) or livestock do not appear to be biologically sound. Keywords: Artemisia tridentata wyomingensis, line intercept, grass cover, Centrocercus urophasianus, forb cover, greater sage-grouse, sage-grouse habitat

Snowshoe Hare use of Silviculturally Altered Conifer Forests in The Greater Yellowstone Ecosystem

Information about snowshoe hare habitat use in key Canada lynx recovery areas, such as the Greater Yellowstone Ecosystem, is critical for the conservation of lynx. Although research conclusions differ in regard to the types and ages of forests preferred by snowshoe hares, restrictions on silvicultural practice have been implemented by forest managers to protect snowshoe hares in this area. However, some research suggests that regenerating lodgepole pine stands associated with silvicultural treatments benefit snowshoe hares. We evaluated three indices of snowshoe hare use within a timber management area in southwest Montana, inside the Greater Yellowstone Ecosystem (1999–2012) to assess the relative use of forest types. We analyzed: 1) 11 years of data collected from 280 pellet plots using linear mixed models and AICc model selection, 2) 13 years of track counts from 2,202 km of roadway travel using Chi-squared goodness-of-fit tests of proportional segment lengths and the associated cover types, and 3) 76 nights over one winter of live-trapping using a hare/night index. Overall, we observed the greatest use within the youngest two classes of regenerating lodgepole pine stands that were associated with clear cutting and pre-commercial thinning. These results suggest snowshoe hares prefer silviculturally influenced 30–60 years old lodgepole pine forests

Fine Scale Nest Site Selection of Greater Sage-Grouse In The Centennial Valley, Montana

The purpose of this study was to determine fine scale nest site selection of greater sage-grouse (Centrocercus urophasianus) in the Centennial Valley, MT. A total of ninety nests were found during 2014-2015 using radio-collared sage-grouse. Vegetation surveys were conducted at nests and random sites that measured the nest shrub and the cover available within 3m of the nest. Length of the branch over the nest (Lgth.LB), average axis width of the nest shrub (AvgAxis), lateral cover of the nest shrub (LCShrub), aerial cover of the nest shrub (ACShrub), and height of the lower branch over the nest (Ht.LB) were the habitat variables that received the most support. All habitat variables that were included in the top model were nest shrub morphological characteristics and cover provided by the nest shrub. Therefore, there is strong support that sage-grouse in the Centennial Valley are selecting nest sites based on the morphology of the nest shrub and the cover provided by that nest shrub. None of the habitat variables associated with herbaceous cover received much support for inclusion in our models. On average, residual cover (i.e. grass from previous year) provided concealment for only 4% of the nest bowl. The relative probability of a shrub being selected for a nest site is maximized when Lgth.LB >75cm long, AvgAxis >130cm wide, LCShrub >80%, and ACShrub > 70%. Managers should focus on conserving mountain big sagebrush (Artemisia tridentata ssp. vaseyana) and three-tip sagebrush (Artemisia tripartita) habitats because they were more likely to meet those shrub characteristics

Aspen Recovery Since Wolf Reintroduction on the Northern Yellowstone Winter Range

Quaking aspen (Populus tremuloides Michx.) recruitment and overstory stem densities were sampled in 315 clones in 1991 and 2006 on 560 km2 of the Northern Yellowstone Winter Range (NYWR). A primary objective was to observe if aspen status had improved from 1991 to 2006: evidence of a wolf (Canis lupus) caused trophic cascade. Recruitment stems (height \u3e 2 m and diameter at breast height \u3c 5 cm) represent recent growth of aspen sprouts above elk (Cervus elaphus) browsing height, whereas overstory stems (all stems \u3e 2 m) represent the cohort of stems, which will insure the sustainability of the clone. Overstory stem densities declined by 12% (P = 0.04) on the landscape scale when compared with paired t-tests. Overstory stems declined in 58% of individual clones and in 63% of the 24 drainages of the study area. The second objective was to determine which factors influenced changes in aspen density. Winter ungulate browsing (P = 0.0001), conifer establishment (P = 0.0001), and cattle (Bos spp.) grazing (P = 0.016) contributed to the decline in overstory stem densities when analyzed using a mixed effects model of log transformed medians. Eighty percent of the clones were classified as having medium to high browsing levels in 1991, whereas 65% of the clones received a similar rating in 2006, possibly due to the reduced NYWR elk population. Aspen recruitment has increased in some 2–10 km2 areas, but not consistently. Our study found that a trophic cascade of wolves, elk, and aspen, resulting in a landscape-level recovery of aspen, is not occurring at this time

Aspen Restoration Using Beaver on the Northern Yellowstone Winter Range under Reduced Ungulate Herbivory

Ungulate browsing and lack of overstory disturbance have historically prevented aspen regeneration on the Northern Yellowstone Winter Range (NYWR). Aspen clones regenerate if sprouts are produced that grow into recruitment stems (\u3e2 m tall) and replace the mature overstory. Beaver reintroduced in 1991 to Eagle Creek on the NYWR facilitated aspen restoration by removing overstory trees and increasing sprouting. However, intense ungulate browsing, primarily from the Northern Yellowstone elk herd, was preventing aspen recruitment in Eagle Creek as of 2005. Since 2005, wolf predation has contributed to a 56% decrease in this elk herd. We investigated the effects of beaver reintroduction, ungulate herbivory, and predator-mediated declines in elk numbers on aspen regeneration in Eagle Creek from 1997 to 2012. Aerial photos of Eagle Creek in 2005 and 2011 showed that the aspen overstory has not been replaced 21 years after beaver reintroduction (p \u3e 0.05). Sprouting and recruitment were investigated using 4-m radius circular plots (n = 31) established throughout Eagle Creek in 1997 and monitored annually until 2012. Beaver activity stimulated sprouting in 71% of these plots. In 2012, 77% of the plots had ≥1 recruitment stem and 75% of the paired plots associated with exclosures (n = 16) had aspen stems with an average height ≥2 m. Recent increases in aspen recruitment in Eagle Creek indicate that aspen communities are regenerating. This has likely resulted from decreased ungulate browsing pressure on aspen saplings from 2005 to 2012. These findings are consistent with the predictions of a density-mediated trophic cascade following wolf reintroduction