Adapting management to a changing world: Warm temperatures, dry soil, and interannual variability limit restoration success of a dominant woody shrub in temperate drylands

Abstract

Restoration and rehabilitation of native vegetation in dryland ecosystems, which encompass over 40% of terrestrial ecosystems, is a common challenge that continues to grow as wildfire and biological invasions transform dryland plant communities. The difficulty in part stems from low and variable precipitation, combined with limited understanding about how weather conditions influence restoration outcomes, and increasing recognition that one-time seeding approaches can fail if they do not occur during appropriate plant establishment conditions. The sagebrush biome, which once covered over 620,000 km of western North America, is a prime example of a pressing dryland restoration challenge for which restoration success has been variable. We analyzed field data on Artemisia tridentata (big sagebrush) restoration collected at 771 plots in 177 wildfire sites across its western range, and used process-based ecohydrological modeling to identify factors leading to its establishment. Our results indicate big sagebrush occurrence is most strongly associated with relatively cool temperatures and wet soils in the first spring after seeding. In particular, the amount of winter snowpack, but not total precipitation, helped explain the availability of spring soil moisture and restoration success. We also find considerable interannual variability in the probability of sagebrush establishment. Adaptive management strategies that target seeding during cool, wet years or mitigate effects of variability through repeated seeding may improve the likelihood of successful restoration in dryland ecosystems. Given consistent projections of increasing temperatures, declining snowpack, and increasing weather variability throughout midlatitude drylands, weather-centric adaptive management approaches to restoration will be increasingly important for dryland restoration success.

Soil characteristics are associated with gradients of big sagebrush canopy structure after disturbance

“…This is in contrast to previous studies that have attributed explanatory power of post-fire sagebrush characteristics to gradients in mean annual precipitation (e.g., Germino et al 2018 or snowpack accumulation (Shriver et al 2018). This is in contrast to previous studies that have attributed explanatory power of post-fire sagebrush characteristics to gradients in mean annual precipitation (e.g., Germino et al 2018 or snowpack accumulation (Shriver et al 2018).…”

“…First, the weather that occurs the year immediately following seeding treatments (especially precipitation and temperature) can impact the rate and magnitude of vegetation recovery (Brabec et al 2017, Hardegree et al 2017, Shriver et al 2018, and likely enhance model explanatory power. First, the weather that occurs the year immediately following seeding treatments (especially precipitation and temperature) can impact the rate and magnitude of vegetation recovery (Brabec et al 2017, Hardegree et al 2017, Shriver et al 2018, and likely enhance model explanatory power.…”

“…However, the increasing frequency and severity of disturbances such as wildfire can interfere with historical soilvegetation relationships, altering resource availability and transforming ecosystem composition (Chambers et al 2007). The success or failure of reestablishing key species through seeding treatments after disturbance has been linked broadly to, for example, physiography, vegetation community, and soil moisture availability (Knutson et al 2014, Shriver et al 2018), but few studies have focused on gradients in canopy structure growth, specifically in reestablished communities. Hence, understanding landscape factors driving these gradients, especially using field-identifiable soil factors such as texture or surface characteristics (i.e., the pedoderm), is essential to understanding how canopy structure can redevelop for wildlife habitat and to promote historical ecosystem functioning.…”

“…These studies have linked factors to greater sagebrush reestablishment and canopy structure growth including greater annual precipitation, more favorable topographic positions, coarser soil textures, greater soil depths, and specific soil surface conditions (e.g., Knutson et al 2014, Nelson et al 2014, Shriver et al 2018. These studies have linked factors to greater sagebrush reestablishment and canopy structure growth including greater annual precipitation, more favorable topographic positions, coarser soil textures, greater soil depths, and specific soil surface conditions (e.g., Knutson et al 2014, Nelson et al 2014, Shriver et al 2018.…”

Pre‐fire vegetation drives post‐fire outcomes in sagebrush ecosystems: evidence from field and remote sensing data

“…We defined the contemporary time period as 2011-2016 to facilitate comparisons of contemporary field data (collected during this time period) and contemporary component data. This finding may explain why declines in shrub and sagebrush cover as estimated from component data (Table 1) were larger in burned plots in California than those in Idaho, and is consistent with research showing that sagebrush recovery after a fire can be a slow process that may require several decades in some locations, or occur only under certain climate conditions (Billings 1994, Wamboldt et al 2001, Lesica et al 2007, Knutson et al 2014, Shriver et al 2018. Indeed, the Rush Fire in 2012, which was responsible for burning the majority of burned plots in California (87% and 95% for the Field vs.…”