Goldilocks forbs: survival is highest outside—but not too far outside—of Wyoming big sagebrush canopies

Abstract

In arid and semiarid systems, positive effects of nurse shrubs generally occur immediately underneath and around shrub canopies, creating microsites that can be targeted to promote plant establishment in restoration settings. Alternatively, the best microsites may occur in the interspace zone immediately surrounding nurse shrubs if positive abiotic effects extend beyond nurse shrub canopy boundaries and if competition with nurse shrubs is reduced in that zone. In the Intermountain West, U.S.A., we investigated survival of transplanted herbaceous seedlings at different distances from Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) canopies. We planted two native perennial forb species, Munro's globemallow (Sphaeralcea munroana) and common yarrow (Achillea millefolium), and two native perennial grass species, bluebunch wheatgrass (Pseudoroegneria spicata) and bottlebrush squirreltail (Elymus elymoides), at four distances from sagebrush canopies at six sites across the Intermountain West, repeated across 2 years. Under above‐normal precipitation, proximity to sagebrush influenced first‐year survival of the forb, but not grass, species. Globemallow and yarrow survival were highest mid‐way between the canopy dripline and maximum interspace distance between neighboring sagebrush plants. Ground cover characteristics and globemallow survival covaried with respect to distance from shrub, suggesting ground cover characteristics as indicators of suitable planting microsites. Under drier conditions, survival of all species was low and unaffected by distance from canopies. Our results demonstrate the value of fine‐tuning the canopy‐interspace paradigm to more carefully consider how plant performance may differ across zones within the interspace region between plants, especially when the goal is to maximize plant establishment in nondrought years.

Under drought conditions, fungicide seed coating does not increase emergence of two native grass species in sagebrush stands of the Intermountain West, U.S.A.

“…When precipitation was low, we found that planting near canopies had the potential to increase emergence, dependent on site conditions. Meanwhile, other studies suggest that there is no disadvantage to planting near canopies when precipitation is at normal or higher, as being planted near the canopy does not influence the establishment of direct‐seeded (Swanson et al 2021) or transplanted seedlings (Koutzoukis et al 2023). The same risk‐neutral approach does not hold for fungicide coatings; when precipitation is high, fungicide coatings can greatly increase emergence (Hoose et al 2022), but our results indicate that when precipitation is low, encrusting seeds to deliver fungicide may inhibit emergence.…”

Addressing barriers to proactive restoration of at‐risk sagebrush communities: a causal layered analysis

“…before fire) has not been practiced as a proactive means of increasing their resistance and resilience. Experimental research to test the feasibility of this proactive approach has been under way since 2018 at six locations in the Great Basin region focusing on public lands (Koutzoukis et al 2020), which constitute majority of rangelands in the West.…”