Questions

Questions in this section frequently come up in workshops, field tours, symposia, and general discussions related to pinyon-juniper woodlands.  They are closely linked to woodland ecology, resilience, resistance to invasives, and restoration.  Most are addressed in more depth in referenced citations and Miller et al. 2019.

What is the difference between old-growth, persistent, and presettlement woodlands?

In the literature, the terms presettlement, persistent, and old-growth are often used for woodlands existing on the landscape prior to Eurasian settlement. Although often used interchangeably, each has a different meaning and may or may not be one and the same. Presettlement woodlands established prior to Eurasian settlement and introduction of livestock around the 1860s…

Why is fire 5 times more likely to burn in the Great Basin than the Colorado Plateau?

Fire is five times more likely to burn in the northern Great Basin than in the southern Great Basin and Colorado Plateau (Littell et al. 2009). While the abundance and distribution of invasive annual grasses are likely influencing present-day regional fire occurrences in the northwestern Great Basin, Columbia Basin, and Snake River Basin, they do…

Are there sites where shrubs and perennial grasses and forbs can persist beneath closed pinyon and/or juniper canopies?

Yes and no.  Shrubs rarely persist beneath a closed tree canopy, especially sagebrush.  However, deep rooted perennial grasses have been observed to persist on sites with deep soils and where restrictive layers (e.g. clay accumulation layer called an argillic), reducing water capture and storage are absent or weakly developed.  Photos of two different pinyon-juniper sites,…

How will cheatgrass respond to projected changes in future climate?

Increasing temperatures and reduced summer precipitation are projected to favor expansion of cheatgrass (Bromus tectorum) at higher elevations.  The greater the change in summer conditions, the greater the expected shift in cheatgrass (Bradley et al. 2016).  Although cheatgrass will probably decline at lower elevations, red brome (B. rubens) already present throughout the Great Basin will…

Does elevated atmospheric CO2 favor cheatgrass?

Several studies found that increased atmospheric CO2 concentrations resulted in increased cheatgrass (Bromus tectorum), when soil water and nutrients were not limiting establishment and growth (Hungate et al. 1996; Larigauderie et al. 1988; Nowak et al. 2004).

Will cheatgrass dominate a site in the first growing season following fire where native perennial grasses are depleted?

Response of cheatgrass (Bromus tectorum) the first growing season on a depleted site following fire depends on seed source.  Abundance of post-fire cheatgrass seed is directly related to: the amount of seed in the seed-pool prior to the fire the amount seed combusted by fire, which is largely related to the abundance and types of…

Does tree removal influence soil water storage and stream flows?

Soil water storage: During the spring, Utah junipers (Juniperus osteosperma) and western junipers (J. occidentalis) rapidly used soil water in the upper soil zone (<0.9 m [3 ft] deep) where soil nutrient concentrations are highest and most important for the majority of herbaceous species. In areas where trees have been removed, the growing season of…

How long does it take pinyon and juniper seed to develop and how long does it persist in the soil?

In pinyon pines (Pinus monophylla and P. edulis), portions of three growing seasons are required to produce mature seeds. Pinyon seeds are short-lived with little inherent dormancy.  In Utah (Juniperus osteosperma) and western junipers (J. occidentals), it takes two growing seasons following pollination to produce mature fruits. In contrast to pinyon, juniper often have long-lived seeds…

Why do large fire years often follow one or more wet years in the semiarid Great Basin?

Many semi-arid communities are fuel limited, thus the accumulation of fine fuels during wet years increases fuel continuity at the landscape level and has been closely linked to large and widespread fires in semiarid ecosystems (Abatzoglou and Kolden 2013; Allen et al. 1995; Baisan and Swetnam 1997; Brown et al. 2008; Grissino-Mayer and Swetnam 2000;…

How do you determine if a site is fully occupied (stocked) by pinyon and or juniper?

The amount of lateral leader growth on understory sapling-size trees is a good indicator of understory competition between overstory trees.  Compare leader length in closed stands to trees growing in the open or at the edge of a stand or adjacent to a road.