Sagebrush Height Research Articles

The effect of vegetation structure on predation of artificial Greater Sage-Grouse nests

In Canada, Greater Sage-Grouse (Centrocercus urophasianus) are considered an endangered species by the Committee On the Status of Endangered Wildlife In Canada (COSEWIC), due to declining population numbers and distribution. Encroachment of agriculture and subsequent destruction of suitable sagebrush (Artemisia spp.) habitat is thought to be responsible for historical population declines. However, subtle changes in habitat quality may also result in reduced escape and nesting cover, which may lead to increased levels of predation. We examined the influence of vegetation cover and height on the fate of artificial Greater Sage-Grouse nests. Because most natural sage-grouse nests are associated with sagebrush, we predicted that sagebrush height and cover would be crucial to the success of nests. Lateral cover is important in protecting nests from detection by predators, and thus we predicted that nests surrounded by shorter grass would suffer greater predation rates than nests with taller grass. To experimentally test this hypothesis, we trimmed grass surrounding some artificial nests. Richardson’s ground squirrels (Spermophilus richardsonii) were the primary predators of artificial nests, with some predation by corvids and badgers (Taxidea taxus). Successful nests tended to be surrounded by shorter sagebrush, taller grasses, and taller, denser forbs than predated nests. Trimming grass around nests did not affect nest fate. However, ground squirrels typically attacked nests with less forb cover and fewer sagebrush, and avian predators tended to destroy nests at inactive leks with greater lateral cover. Thus, lateral cover provided by forbs and sagebrush appeared to be important for protecting nests from mammalian predators. These results suggest implementing management strategies that improve sagebrush habitat by providing tall, dense forbs and sagebrush, which could increase Greater Sage-Grouse nest success and recruitment.

Spectral and biophysical relationships of montane sagebrush communities in multi-temporal SPOT XS data

Correlation and multiple regression analysis was used to examine the relationships between spectral and biotic factors within the sagebrush communities of Grand Teton National Park, Wyoming. Field-sampled data on biophysical factors were regressed against June 1996 and September 1996 SPOT multi-spectral reflectance data for fifty-one plots. Highest r 2 values were generated for regression models using June reflectance data alone for predicting biophysical factors. Predictability of bitterbrush cover was improved using September reflectance data alone. Models predicting biophysical characteristics of sagebrush communities generally were not improved by using a combined June-September data set. Regression models for big sagebrush height, low sagebrush cover, and rock/soil cover were improved slightly using the combined two-date data set. Selection of remotely sensed data for biophysical studies of vegetation communities should be driven by the ecological and phenological characteristics of the vegetation community to be studied.