The effects of mechanical thinning treatments on juniper and ponderosa pine understory vegetation and key mule deer forage species in Northeastern New Mexico, USA
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Over the past 150 years, conifer species have been expanding into southwestern grasslands, displacing resident plant communities. The expansion of juniper (Juniperus spp.) and ponderosa pine (Pinus ponderosa) has led to reductions of grass and forb communities, has altered wildlife habitat, and has created potential problems for wildlife managers and ranchers, who often desire to remove or reduce juniper or ponderosa stands in an effort to improve wildlife or livestock habitat. The goal of this study was to determine the effects of juniper and ponderosa pine removal by selective logging and hydraulic mulching, on mule deer habitat in northeastern New Mexico. The primary objectives of this study were to: (1) examine differences in plant community richness, species occurrence, and cover between areas with and without removal of juniper and ponderosa; and (2) determine if removal of juniper and ponderosa improves biomass production, abundance and cover of key forage species available to mule deer (Odocoileus hemionus). Plant composition, biomass production, and plant density were assessed during June and July, at the height of the growing season, in 2011 and 2012. Analysis via Proc General Linear Models and Tukey Honestly Significant Difference were used to evaluate the treated and untreated plant communities and their differences in habitat characteristics preferred by mule deer. The results of this study will help provide information about how conifer removal and resulting changes in vegetation composition and production influence habitat characteristics preferred by mule deer. There was a slight increase species richness, total biomass production and key forage abundance in areas where trees were mechanically thinned. Treatments were unsuccessful at increasing herbaceous cover during times of drought. This information will be beneficial for ranchers and wildlife managers who seek to maintain suitable ungulate body conditions and healthy plant communities, by determining whether logging and hydro-axing are feasible and beneficial for managing habitat for mule deer.