Consequences of pinyon and juniper woodland reduction for wildlife in North America

Abstract

Pinyon and juniper (Pinus spp., Juniperus spp.) woodlands are expanding into shrublands and grasslands throughout much of western North America. Woodland reduction is frequently used to mitigate the effects of conifer encroachment on game species (e.g. mule deer Odocoileus hemionus) and shrub and grassland-obligate species (e.g. sage grouse Centrocercus spp.). Although these practices are widespread, previous studies on the effects of woodland reduction on animal communities have not yet been synthesized, making it difficult to set priorities for future research and practice. To address this gap, we first summarize the history of pinyon and juniper reduction in western North America and characterize known wildlife habitat associations in pinyon and juniper ecosystems. We then review and synthesize evidence from the scientific literature on wildlife responses to pinyon and juniper woodland reduction. We tallied the outcomes of these studies to determine the relative proportions of positive, negative, and nonsignificant responses by different taxonomic groups and functional groups. The majority (69%) of animal species responses to woodland reduction treatments were non-significant. However, particular groups of species (taxonomic and/or functional) were more likely to respond positively or negatively, depending on the woodland reduction treatment method. Unexpectedly, investigators often found non-significant or negative responses by ungulates to woodland reduction, and non-significant responses by sagebrush obligate species. However, few studies measured effects on sagebrush obligate species, which limits inference for this group. Indeed, our review demonstrates that the effects of woodland reduction are well-understood for only a subset of taxonomic groups (e.g. birds and small mammals); whereas other groups (e.g. reptiles and terrestrial invertebrates) are consistently under-studied. Further, a shortage of large-scale and long-term research limits our ability to fully understand spatial and temporal wildlife responses to woodland reduction. We encourage practitioners to design and implement pinyon and juniper reduction projects to experimentally assess the effects of these practices on both target and nontarget species. Adopting consistent monitoring protocols across projects would also facilitate greater understanding of how factors such as treatment type, size, location and duration result in positive or negative impacts to diverse wildlife of conservation concern.

Aridity drives spatiotemporal patterns of masting across the latitudinal range of a dryland conifer

“…Concurrent declines in seed production (Redmond et al 2012), seedling establishment (Floyd et al 2015, Redmond et al 2015, growth (Redmond et al 2017) and survival (Breshears et al 2005) portend a shift in the distribution and persistence of this conifer across the most arid portions of its range. Given piñon pine's role as a keystone species in many ecosystems for providing wildlife habitat (Bombaci and Pejchar 2016), food resources (Ignatov et al 2017), water retention (Morillas et al 2017) and carbon storage (Huang et al 2010), it is vital to understand the potential consequences of this demographic squeeze.…”

Multiscale models of habitat use by mule deer in winter

“…For example, forest canopy cover is an important habitat component for mule deer during winter (Leckenby and Adams , D'Eon and Serrouya , Anderson et al , Webb et al , Smith et al ). In contrast, increased western juniper ( Juniperus occidentalis ) encroachment may reduce availability of forage (Rowland et al , Witt and Patterson , Bombaci and Pejchar ) on winter range and be detrimental to mule deer.…”

“…For example, in Oregon, BLM administers 33% of mule deer winter range including >50% of our study area. Land management activities, including livestock grazing (Robinette et al , Willms et al ), timber harvest (Bergman et al , Bombaci and Pejchar ), energy development (Johnson et al , Sawyer et al ), and recreational activities (Wisdom et al , Stankowich ) could affect mule deer distributions and population dynamics. Additionally, industrial and residential development on or near public lands is increasing, resulting in reduced winter range area and increased disturbance to deer (Sawyer et al , Kline et al , Duncan and Burcsu ).…”

Reptiles Under the Conservation Umbrella of the Greater Sage‐Grouse

“…In other words, the correlative patterns (Table 3) for reptiles are fairly representative of greater sage‐grouse habitat preferences, including preferring intact stands of sagebrush with relatively low amounts of introduced grasses (e.g., crested wheatgrass, cheatgrass) or conifers (Arkle et al 2014, Farzan et al 2015). Conifer felling and removal (i.e., of pinyon pine and juniper trees encroaching into sagebrush) is one of the most common habitat management actions used to reduce perching and nesting structures for avian predators of sage‐grouse and reduce wildfire risk (Farzan et al 2015, Bombaci and Pejchar 2016, Holmes et al 2017). James and M'Closkey (2003) reported a positive response from 2 lizard species within our group I list (common sagebrush lizard and common side‐blotched lizard) when the trees were cut and left on site because these species preferred dead over live trees regardless of whether they were standing or prone.…”