Kayri Havens
Chicago Botanic Garden
Andrea Kramer
Chicago Botanic Garden
Jessamine Finch
Northwestern University
Rebecca Barak
David H. Smith Conservation Fellows
Katie Kucera
Northwestern University
Prairie restoration: How to make the best decisions about what seed provenances to collect and where to use them
Kayri Havens1, Andrea Kramer1, Rebecca Barak1,2, Jessamine Finch1,2, and Abbey White1,2
1Chicago Botanic Garden, Division of Plant Science and Conservation, Glencoe, IL 60022, U.S.A.
2Northwestern University, Department of Biological Sciences, Evanston, IL 60201, U.S.A.
The U.S. tallgrass prairie is one of the world's most endangered ecosystems. It is also an ecosystem where ecological restoration has been practiced for nearly a century. Proper sourcing of seed for this restoration has never been straightforward, and it is becoming even more challenging and complex as the climate changes. For decades, restoration practitioners have subscribed to the 'local is best' tenet, even if the definition of 'local' was often widely divergent between projects. However, given rapid climate change, we can no longer assume that locally-sourced seeds are always the best option. Using examples from our work in the tallgrass prairie and the grasslands of the Colorado Plateau, we discuss what we are learning from provenance trials and how this may influence seed sourcing decisions. We review provisional seed zone maps and seed decision tools, including a new tool under development to assess options of plant provenance based on the goals and context of a given project. Lastly we will discuss our findings in the context of other grassland restoration around the world.
Drivers and constraints of seed mix design for prairie restoration
Rebecca Barak1,2,3,4, Zhao Ma2, Kayri Havens3, and Lars Brudvig4
1David H. Smith Conservation Fellows
2Forestry and Natural Resources, Purdue University, West Lafayette, Indiana, U.S.A.
3Plant Science and Conservation, Chicago Botanic Garden, Glencoe, Illinois, U.S.A.
4Plant Biology Department, Michigan State University, East Lansing, Michigan, U.S.A.
The process of ecological restoration begins long before seeds are sown, in the decision-making process of land managers and other stakeholders in the restoration process. Land managers face multiple, potentially confounding, objectives and constraints as they make decisions for restoration. While restoration ecologists tend to focus on biological considerations when studying restorations and designing experiments, managers must also consider social, economic and other drivers for restoration in general, and for seed mix design in particular. We will report results from a social science analysis of restoration land managers working in the tallgrass prairie ecosystem. We conducted semi-structured interviews with 18 prairie restoration land managers in Illinois, Indiana and Michigan, seeking to understand the decision processes they use to design seed mixes. We asked questions that focused on 1) restoration objectives and the role of seed mix design, 2) drivers and constraints of the seed mix design process, 3) tools and resources for making seed mix design decisions (including the role of restoration research), and 4) determinants of restoration outcomes. Themes brought forth in manager responses will help restoration researchers and practitioners better understand the intricacies of the seed mix design process, and encourage collaboration between restoration researchers and practitioners. This work relates to several goals of the National Native Seed Strategy.
Effects of seed source vary among species, early life stages, and field sites for two milkweeds (Asclepias sp.)
Jessamine Finch1,2, Alexandra Seglias1,2, Andrea Kramer2, and Kayri Havens2
1Northwestern University, Department of Biological Sciences, Evanston, IL 60201, U.S.A.
2Chicago Botanic Garden, Division of Plant Science and Conservation, Glencoe, IL 60022, U.S.A.
A key consideration in ecological restoration is the sourcing of plant material. Ideal sourcing maximizes the likelihood that material is ecologically appropriate, while minimizing any negative genetic effects (e.g. swamping, outbreeding). In seed-based restoration, the first test of ecological suitability is germination and seedling emergence. A mismatch between seed traits and the conditions at the restoration site can serve as a major bottleneck to recruitment, ultimately reducing restoration quality and/or increasing costs. Despite their importance to restoration outcomes, empirically based seed transfer guidelines are not available for most species. Instead, practitioners rely on provisional seed transfer zones, derived from ecological and climatic data, which are intended as a generalized framework to guide seed sourcing for any species. In recognition of this limitation, the National Seed Strategy (for Rehabilitation and Restoration) has called for immediate research to determine empirical seed transfer zones for key restoration species. Given their central role in monarch habitat restoration, proper seed sourcing for milkweeds (Asclepias sp.) has become a top priority. To assess the utility of provisional seed transfer zones, and inform the establishment of empirical zones, we investigated the effect of population and collection zone on field recruitment for two milkweeds (Asclepias incarnata, A. syriaca). Populations (n=18) were sourced from three collection zones and sown at two field sites in the Midwest U.S. We used germination bags and grid-seeded plots to assess variation in germination, emergence, establishment, and juvenile performance. Magnitude and direction of source effects varied among species, life stages, and field sites. For A. incarnata, germination rates and aboveground biomass were greater for southern populations, while seedling emergence was greater for northern populations (P < 0.001). Interestingly, germination, emergence, and biomass of A. syriaca displayed no significant difference among seed sources. Emergence timing, seed source, and field site significantly affected survival for both species (P < 0.001). Overall, survival increased with latitude of population origin at the northern site, but slightly decreased with latitude at the southern site. Variation in early life stages among collection zones was considerably more pronounced for A. incarnata than A. syriaca, suggesting that restoration establishment of A. incarnata is more sensitive to seed sourcing. However, seed sourced from within a single collection zone did perform similarly, indicating that current zones appropriately delineate some degree of intraspecific variation. Implications of these results will be discussed in the context of the ongoing monarch habitat restoration effort and seed sourcing guidelines.
Variation in seed germination requirements and response to gibberellic acid among populations of Penstemon pachyphyllus: implications for the production of genetically diverse mixed-source seed lots
Katie Kucera1, Kevin Gunnell2, Scott Jensen3, Melissa Landeen2, and Andrea Kramer4
1Northwestern University, Department of Biological Sciences, Evanston, IL 60201, U.S.A.
2Utah Division of Wildlife Resources, Great Basin Research Center, Ephraim, UT 84627, U.S.A.
3U.S.D.A. Forest Service Provo, UT 84606, U.S.A.
4Chicago Botanic Garden, Division of Plant Science and Conservation, Glencoe, IL 60022, U.S.A.
Multi-source seed lots (MSSLs) combine multiple populations of a species to increase the genetic diversity of a seed lot beyond what is possible with a single-source approach, and are increasingly being produced for use in ecological restoration. However, the process of producing seed in nursery settings can potentially lead to unintentional shifts in genetic diversity, and little research has been conducted to identify best practices to ensure genetic diversity remains representative of all populations used. For example, if not all populations germinate at the same time or under the same conditions, some populations may be favored in the final seed lot over others. These impacts may be amplified if the species is produced in nursery conditions over more than one generation. We utilize wild-collected and nursery-produced seeds from six populations of Penstemon pachyphyllus, a priority restoration species in the Great Basin region of the western United States where MSSLs are currently being produced for restoration use, to assess this question. Research has shown that the species has intraspecific variation in seed dormancy-breaking requirements, and to establish nursery beds of this species, gibberellic acid is often used to overcome dormancy and ensure the greatest possible germination response across populations. However, it is not known if all populations respond similarly to gibberellic acid and if this may impact which populations are represented in MSSLs. We conducted seed germination trials that included multiple treatments of cold stratification length as well as gibberellic acid. Results confirmed that the germination response of P. pachyphyllus varies among population, and is an interactive function of source population, seed generation, and stratification treatment. Importantly, the relative success of the GA3 treatment compared to the cold stratification treatments varies based on source population and seed generation. These results will be important for monitoring and maintaining unique trait variations and genetic diversity among P. pachyphyllus populations as they are combined and seeded in large-scale restorations.
Assessing capacity of the U.S. native plant production industry to support the restoration of species diversity
Abigail White1,2,, Jeremie Fant1,2, Kayri Havens1,2, Mark Skinner3, and Andrea Kramer1,2*
1Chicago Botanic Garden, Division of Plant Science and Conservation, Glencoe, IL 60022, U.S.A.
2Northwestern University, Department of Biological Sciences, Evanston, IL 60201, U.S.A.
3USDA Forest Service, Pacific Northwest Region Regional Office, Portland, OR 97204, U.S.A.
*presenting author
Seed-based restoration efforts often require large quantities of diverse and appropriately-adapted native plant seeds. Shortages of seeds for the range of species targeted for restoration may prevent the restoration from meeting species diversity and structure goals. In the United States, the native plant industry is helping meet these demands, but very little is known about its capacity to support the needs of species-diverse restoration efforts. We conducted the first comprehensive and quantitative assessment of the native plant industry in the U.S. in order to better understand the capacity of this industry to support the restoration of species diversity. Our assessment includes more than 800 vendors nationwide, as well as the native plant species they make available for restoration. By synthesizing lists of available species sold by native plant vendors across the U.S., we were able to identify gaps in species availability and inform the research, development, and production of native plant materials. Out of ~25,000 native vascular plant taxa native in U.S., we found that 26% are commercially sold, and that the growth form, conservation status, distribution, and taxonomy of the species significantly predicted whether or not it was available. In contrast, less than 0.1% of the nation's ~3,000 native nonvascular taxa were identified as being sold commercially. Additionally, we investigated how the demand for germplasm for high-quality restoration efforts in the Midwestern tallgrass prairie region is being met by vendors. Restoration efforts in this region have been the target of high-quality restoration efforts for decades. We found that 74% of more than 1,000 target species are commercially available in this well-developed native plant market, and genetically-diverse locally-sourced seeds are often available. Building on the successes of regional markets like the tallgrass prairie region, and to fill gaps that we identified, we recommend that future efforts foster stronger regional collaboration, expand on efforts to ensure consistent and clear demand for more diverse species, and support greater investment in applied research of understudied species currently missing from production efforts.