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Grant E. Sorensen

Publications and source records attributed to Grant E. Sorensen.

3 recordsLinked to original sources
USGS2020

Mule deer habitat selection following vegetation thinning treatments in New Mexico

Mule deer ( Odocoileus hemionus ) survival and population growth in north-central New Mexico, USA, was previously reported to be limited by nutritional constraints due to poor forage conditions in degraded habitats. Management recommendations suggested thinning of pinyon–juniper to improve habitat quality for mule deer. To evaluate the influence of these vegetation treatments, we monitored habitat selection by 48 adult female mule deer from 2011 to 2013 in a population previously reported to be nutritionally limited. Monitoring occurred 1–4 years after completion of treatments that were intended to improve forage conditions, including mechanical reduction of pinyon pine ( Pinus edulis ) and juniper ( Juniperus spp.) density and senescent brush ( Quercus gambelii–Cercocarpus montanus ) cover. During the summer season, deer selected recently treated areas, but odds ratios decreased with treatment age. However, during winter, deer avoided more recently treated areas and selected thinned areas >4 years old. Deer selected mixed oak ( Quercus spp.) and pinyon–juniper savanna vegetation cover types with a moderately open canopy and ponderosa pine ( Pinus ponderosa ) forests while avoiding grasslands and montane shrublands across all seasons. Deer selected areas closer to water and developed areas, northeast aspects, on gentle slopes, and at lower elevations. Creating a savanna-like cover type may elicit a positive deer response as a result of their strong avoidance of dense, closed canopy pinyon–juniper woodlands. © 2020 The Wildlife Society.

New Mexico↗
USGS2015

Ungulate exclusion, conifer thinning and mule deer forage in northeastern New Mexico

The southwestern United States has experienced expansion of conifer species ( Juniperus spp. and Pinus ponderosa ) into areas of semi-arid grassland over the past century. The expansion of conifers can limit palatable forage and reduce grass and forb communities. Conifer species are sometimes thinned through hydraulic mulching or selective cutting. We assessed the effects of these treatments on mule deer ( Odocoileus hemionus ) habitat in northeastern New Mexico to determine if conifer thinning improved cover of preferred forage species for mule deer in areas with and without ungulates. We measured plant cover and occurrence of preferred forage species in the summers of 2011 and 2012. An ongoing regional drought probably reduced vegetation response, with preferred forage species and herbaceous cover responding to conifer thinning or ungulate exclusion immediately following treatment, but not the following year. In 2011, areas that received thinning treatments had a higher abundance of preferred forage when compared to sites with no treatment. Grass coverage exhibited an immediate response in 2011, with ungulate exclosures containing 8% more coverage than areas without exclosures. The results suggest that conifer thinning and ungulate exclusion may elicit a positive response, however in the presence of drought; the positive effects are only short-term.

New Mexico↗