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Understory responses to mechanical removal of pinyon-juniper overstory




Stephens, Garrett J., author
Paschke, Mark, advisor
Johnston, Danielle, advisor
Meiman, Paul, committee member
Wilson, Ken, committee member

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Declining Colorado mule deer (Odocoileus hemionus) populations have necessitated improved habitat management techniques. In particular, oil and gas development in the Piceance Basin of western Colorado has impacted critical winter range, creating a need for treatments that will increase forage, and especially palatable shrub species. Pinyon-juniper (Pinus spp - Juniperus spp) tree removal is one technique, however it is unclear which method of tree removal will most effectively promote forage species. This experiment quantified understory responses to pinyon-juniper canopy removal and seed additions using three different methods: anchor chain, rollerchopper, and hydro-ax. Twenty-one 0.8-ha plots were mechanically treated during the fall of 2011 (7 replicates of each treatment). Half of each plot was seeded prior to mechanical treatment with a mix of native grasses, shrubs, and forbs. After two growing seasons, productivity of forbs, grasses, and shrubs combined was roughly three times greater in hydro-ax, rollerchop, and chain plots relative to control plots (where tree removal did not occur). Comparisons of vegetation productivity among treated plots showed that the response of early seral species, some of which were included in the seed mix, was dependent upon the interaction of seeding and mechanical treatments. Specifically, the productivity of annual species was greater in seeded versus unseeded plots for chain and hydro-ax but not for rollerchop. Rollerchop plots, however, had greater productivity of non-native species than chain or hydro-ax (such as Salsola tragus, Descurainia sophia, and Bromus tectorum). Also, the abundance of shrubs, which are an important source of winter forage, was greater in seeded than unseeded subplots. Results after two growing seasons suggest that all three mechanical treatments increase forage productivity and of the three techniques, rollerchop may promote non-native establishment (primarily forbs). At this early stage in plant community development, differences in the effect of mechanical treatments on shrub forage are not yet apparent, but may emerge with future monitoring.


2014 Spring.
Includes bibliographical references.

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mechanical treatments
mule deer


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