By Bryce Richardson, Research Geneticist, USDA Forest Service, Rocky Mountain Research Station, Provo, Utah, USA (brichardson02@fs.fed.us)
The sagebrush biome in western North America (Fig. 1) is experiencing degradation principally from increased frequency of disturbances and the displacement of sagebrush, primarily big sagebrush (Artemisia tridentata), and other native shrubs, forbs, and grasses by invasive species. This process has resulted in the loss of flora and fauna (e.g., greater sage-grouse, Centrocercus urophasianus) that depend on these ecosystems. Restoration of sagebrush ecosystems, either by seeding or planting nursery stock of sagebrush and other native plants, is our best defense to reduce the expansion of invasives and improve degraded lands.
Figure 1. The sagebrush biome can be comprised of several species, but the most dominant is big sagebrush (Artemisia tridentata) occupying sites from 300 to 3,000 m. This broad ecological breadth is further divided into three predominant subspecies (tridentata, wyomingensis and vaseyana) that occupy different ecological niche. (Photo: Nancy Shaw)
A fundamental component of sagebrush restoration is developing the knowledge and tools to collect and store native plant seeds and deploy seed collections to the appropriate site. This can be challenging for big sagebrush for a number of reasons:
1) Taxonomic complexity: Big sagebrush consists of three predominant subspecies with overlapping distributions and in some cases introgression.
2) Genetic adaptation: Like many widespread plants, big sagebrush exhibits clinal variation in adaptive traits. This is especially the case for cold hardiness and prudent movement of seed is warranted.
3) Seed storage: If not properly stored in cold and dry conditions, sagebrush seed can be short-lived. Maintaining appropriate conditions in seed storage facilities is critical to having viable seed on hand for restoration projects.
4) Episodic weather: Arid ecosystems often vary considerably in precipitation patterns. There are likely years in which low precipitation is not conducive to seed germination or seedling establishment. This is true whether planting results from natural seed dispersal or from human strategies efforts to seed or plant big sagebrush and other natives.
5) Climate change: Many studies have suggested that big sagebrush is susceptible to a warming climate. Vulnerability to climate change appears be greatest at the warm-dry end of the sagebrush biome climate spectrum, which is primarily occupied by Wyoming big sagebrush. Climate change could be one of the underlying factors contributing to current losses in this subspecies.
Figure 2. Collectors harvest seeds in the fall from basin big sagebrush (Artemisia tridentata subsp. tridentata). Seed is cleaned, certified for purity, subspecies and location and then stored for restoration projects. (Photo: Stan Young)
The sagebrush seed work group (SSWG) was formed in 2017 with the following goals: 1) identify best practices and knowledge gaps relevant to the use of sagebrush seed in ecosystem restoration activities, 2) promote research to develop, test and refine those practices and to fill knowledge gaps and 3) engage with existing collaborations to encourage adoption and implementation of practices that will improve restoration outcomes. The SSWG is comprised of federal and state researchers and land managers, private seed vendors, and state seed certification agencies. The primary tasks for the group include: exploring methods to differentiate taxa both in the field and in the laboratory, developing seed transfer limits based on adaptive traits and making these limits climate-smart (i.e., capable of projecting these transfer limits using climate change models) and developing seed technology, such as seed coatings, to improve germination and establishment success.