Vegetation Change
Vegetation is changing both through time and with treatments. We measure every species present along permanent transects to track shifts in native:invasive dynamics, species diversity, successional stage, and habitat for terrestrial wildlife. Some of the major findings from the first 10 years of vegetation monitoring are that in the shrubland network, cheatgrass is increasing regardless of treatment, and that sagebrush recovery is very slow after treatment. We saw more positive results in the woodland network: herbaceous vegetation is recovering well after treatments but includes both native and non-native species. Moist/cool sites and mechanical treatments tended to have more positive recovery trajectories than warm/dry and prescribed burn treatments.
Latest Resources on Vegetation
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Our review revealed tradeoffs in woody fuel treatments between reducing canopy fuels vs. increasing understory herbaceous vegetation (fuels) and fire behavior. In pinyon-juniper expansion areas, all treatments decreased crown fire risk. Prescribed fire and cut and broadcast burn treatments reduced woody fuels long-term but had higher risk of invasion. Mechanical treatments left understory vegetation intact and increased native perennial plants. However, cut and leave treatments increased downed woody fuel and high-intensity wildfire risk, while cut and pile burn and mastication caused localized disturbances and annual grass invasion. Ecological outcomes depended on ecological resilience; sites with warm and dry conditions or depleted perennial native herbaceous species experienced lower recovery and resistance to invasive annual grasses. In invasive annual grass dominated areas, high-intensity targeted grazing reduced fine fuels but required retreatment or seeding; in intact ecosystems with relatively low shrub cover, dormant season targeted grazing reduced fine fuel and thus fire spread. Preemergent herbicides reduced annual grasses with differing effects in warm and dry vs. cool and moist environments.
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Coating seeds with amendments to increase germination, emergence, and establishment is a promising strategy for dryland restoration. Seed coatings containing fungicides offer a potential solution in regions where fungal pathogens cause seed mortality during the winter stratification period between late fall seeding and spring germination. The effectiveness of the fungicide treatment, however, may be dictated by weather and within-site microenvironment. We tested how fungicide coating influenced seedling emergence of native grasses within sagebrush stands by planting untreated seeds and seeds coated (encrusted) with and without active fungicide ingredients in furrows that extended from the canopy edge of sagebrush plants (Artemisia tridentata ssp. wyomingensis) into the interspace. This was replicated at four sites across the Intermountain West in two successive years. We planted two native grasses, bluebunch wheatgrass (Pseudoroegneria spicata) and bottlebrush squirreltail (Elymus elymoides). Emergence was extremely low in both years, with a complete seeding failure (i.e. zero emergence) at two sites in the first year and three sites in the second year. At the one site where emergence was sufficient for statistical analysis, a) the coating on the fungicide and blank treatments inhibited emergence under anomalously dry conditions, and b) across seed treatments, proximity to a sagebrush canopy slightly increased seedling emergence. The variable emergence patterns across sites and years (e.g. the highest emergence was for the site-year combination with the lowest precipitation) highlight the sensitivity of seeding outcomes to, and dependence of fungicide seed coatings on, site conditions, and the necessity of repeating experiments across different weather years.
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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 canopies. We planted two native perennial forb species, Munro’s globemallow and common yarrow, and two native perennial grass species, bluebunch wheatgrass and bottlebrush squirreltail, 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.