8
Knowledge Gaps and Research Needs to Support the Native Seed Supply
For the seed supply to work efficiently, there is a need for a strong foundation of knowledge to underpin decision making. Because native seed is a high-value product and decisions about its use have consequences, not the least of which is the success or failure of restoration projects, the effective management of the nation’s seed supply must be supported by knowledge drawn from many sources.
Over the course of the assessment the committee learned of multiple types of information needs. There are some issues that call for innovative and even transformative research with potentially broad applicability across the nation, for example, seed sourcing with particular attention to climate change, the integration of traditional ecological knowledge into restoration practices, and the economics of native seed production and markets.
Other issues call for the accelerated development and wider dissemination of improved technical knowledge relevant to specific regions and/or species, including how to improve the genetic diversity, viability, quality testing, long-term storage, and deployment of seeds and other native plant materials for restoration. While not a research topic per se, the utility of seed certification is highlighted (Box 8-2) as an avenue whereby the genetic research suggested in this chapter can be supported with a consistent set of definitions of germplasm status and development and cultivation protocols.
SEED SOURCING AND SEED ZONE DELINEATION
There is a considerable body of research showing that plant populations can become locally adapted to climate, soils, competitive regimes, pests and pathogens, and many other factors (Hufford and Mazer, 2003; Linhart and Grant, 1996). This has led to local seed sourcing preferences for restoration, although the definition of “local” can be quite divergent between projects. For several species, seed transfer zones have been empirically derived from common garden studies. A summary of these, with maps, data, and citations, can be found on the US Forest Service’s Threat and Resource Mapping site.1 Seed transfer zones are geographic areas within which seeds can be planted with minimal risk of maladaptation (Kramer and Havens, 2009). Local adaptation can vary significantly between species so seed transfer zones are ideally determined on a species-by-species basis (Johnson et al., 2010; Leimu and Fischer, 2008).
For taxa where seed transfer zones have not been studied, provisional seed zones have been developed (Bower et al., 2014; Doherty et al., 2017) (see Figure 8-1a) including those that augment climate-only zones with molecular genetics (Massatti et al., 2020) and arbitrary geographic distance (Saari and Glisson, 2012) to source seeds.
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1 See https://www.fs.usda.gov/wwetac/threat-map/TRMSeedZoneMapper.php (accessed February 1, 2023).
SOURCE: US Forest Service (Bower et al., 2014; Omernik, 1987).
However, many studies suggest that using an ecologically similar source site leads to better outcomes (Hereford, 2009; Johnson et al., 2010, 2015). See Figure 8-1b for a map of Omernik Level III ecoregions used to source seeds for all species.
Despite the existence of considerable case-by-case research on local adaptation, there is still a great need to improve the overall scientific basis for seed zone definitions, with the goal of creating widely accepted standards for seed zone delineation which could significantly improve the functioning of the native seed market.
SEED SOURCING AND CLIMATE CHANGE
Rapid climate change now poses a fundamental challenge to traditional approaches to seed sourcing in restoration. Many restoration projects are now obtaining seed from more distant sources (provenances), employing strategies such as broadening the definition of local (relaxed local provenancing), creating mixtures from different source areas (composite provenancing, admixture provenancing), and obtaining seeds from regions where the climate resembles the predicted future climate of the restoration location (predictive provenancing) (Breed et al., 2013, 2018; Broadhurst et al., 2008; and Havens et al., 2015).
Mixed-provenance strategies have also been proposed to increase genetic diversity and therefore the potential for climate adaptation (Bucharova et al., 2019; Prober et al., 2015; but see Kramer et al., 2018). The Climate Smart Restoration Tool2 maps current and future seed transfer limits for seed lots based on empirical or provisional data.
The science of climate-adapted restoration is new and rapidly evolving, and conclusive empirical tests of proposed strategies are scarce. This creates tremendous needs and opportunities for basic and applied research, which could include conducting an actual restoration project in a rigorous experimental fashion using the principles of adaptive management. We note that seed of known provenance (such as source-identified seed) is a critical requirement for such research (Havens et al., 2015; Vitt et al., 2022).
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2 See https://climaterestorationtool.org/csrt/ (accessed December 1, 2022).
SOURCE: Environmental Protection Agency (Omernik, 1987).
SPECIES DIVERSITY AND COMPOSITION
Just as seed selection will be informed by studies on the role of genetic diversity and provenance within a species and population, there are many research questions to be addressed about the appropriate selection of species and species mixes for restoration projects. Of course, the basic goal in many cases is to reestablish as many as possible of the plant species that were present at a site prior to disturbance. However, there are other instances in which this goal is not achievable because of highly altered site conditions, lack of pre-disturbance information, or scarcity of the necessary plant material. Also, there are cases in which the selection of species mixes is directed at outcomes such as supporting pollinators or wildlife, regenerating depleted soil microbiota, or maintaining stable plant cover under challenging physical conditions. For selecting species mixes, an extensive literature based primarily on controlled small-scale experiments suggests the general principle that higher levels of plant diversity at the species, functional, and/or phylogenetic levels will lead to higher average biomass, temporal stability of biomass, or other desirable aspects of ecosystem function (Cardinale et al., 2006, 2007, 2012; Gamfelt et al., 2013; Gross et al., 2014; Hector and Bagchi, 2007; Hooper et al., 2012; Kinzig et al., 2002; Loreau and Hector, 2001). The application of this ecological principle to actual restoration practice, especially at the scales of heterogeneous landscapes, is highly deserving of further research. Many other questions concerning species composition in relation to restoration success are also in need of further attention. For example, either functional traits (e.g., Leger et al., 2021), or patterns of species co-occurrence in undisturbed sites (e.g., Agneray et al., 2022), may be valuable tools for designing species mixes that are capable of achieving such goals as withstanding harsh environments, co-occurring stably, and resisting invasion.
Research on general principles of restoration success is the provenance of the federal research agencies, including the National Science Foundation, US Department of Agriculture National Institute of Food and Agriculture (NIFA), and the US Geological Survey (USGS). For example, applied research being pursued by the USGS in the context of the Colorado Plateau Plant Program seeks answers to fundamental questions with practical applications (see Box 8-1).
TRADITIONAL ECOLOGICAL KNOWLEDGE
Indigenous cultures traditionally place tremendous importance on the links between human and nonhuman domains, which is reflected in the diverse practices with which they historically managed their plant and animal resources (e.g., Hornborg, 2006; Viveiros de Castro, 2004). Former federal policies reducing tribal land and forced cultural assimilation threatened traditional knowledge for much of the 19th and 20th centuries (see Chapter 5). Recovering and maintaining traditional knowledge was of high importance in the Tribal Nursery Needs Assessment (Luna et al., 2003).
For land management and native plant restoration, there is a growing realization that combining traditional ecological knowledge with western science can benefit both tribal needs and western science approaches to native plant research (Anderson and Barbour, 2003; Berkes, 2008; Berkes et al., 2000; Dockry et al., 2022; Eisenberg et al., 2019; Pierotti and Wildcat, 2000), a theme also highlighted in recent popular books (e.g., Kimmerer, 2013). The Fort Belknap Native Seed and Restoration Program and the Grand Ronde Tribal Native Plant Materials Program described in Chapter 5 show how native knowledge and western science can successfully engage.
A critical area for research is to better understand the collecting, growing, harvesting, and storage of native plants on tribal lands, in the context of managing and promoting ecological restoration and ecosystem management and the cultural uses of native plants. This need was also noted in the Tribal Nursery Needs Assessment and the Nursery Manual for Native Plants (Dumroese et al., 2009), yet it remains largely unmet. Critical to this process is engaging tribes in all aspects of planning, carrying out, and applying results from scientific projects to promote ecosystem management and native plant restoration (Dockry et al., 2022; Farley et al., 2015).
ECONOMICS OF NATIVE SEED PRODUCTION AND MARKETS
This report offers a general sense of availability and uses of native seed and plant materials, but data gaps prevented it from offering a clear, quantitative picture at the national level. Not only is the magnitude of total native seed use currently not clear, by extension so too is our overall quantitative understanding of how native seeds are used and the costs to produce them. Economic research is needed to understand (1) the nature of demand and supply in the current native seed market; (2) the evolution of native seed uses over time; (3) costs of production for major types of native seed; and (4) sources of production and price risk, as well as the effectiveness of alternative contract designs at mitigating those risks.
A comprehensive market study is needed simply to characterize the magnitude and details of the US native seed and plant material market. As noted in the introduction to this report, one-third of US territory is in government hands, with the rest held privately (Figure 1-1). For certain federal agencies, land areas under direct management are well known (Table 3-1), and some federal, state, and tribal agencies can report the use of native seed on their lands. Although tracking native seed use on private agricultural land is trickier because of the many buyers, the area planted with native seed under USDA programs like the large Conservation Reserve Program (see Iovanna and Pratt presentation reported in Chapter 6) is fairly clear (although seed species and quantities are not). On non-agricultural private land, there is no central data source to estimate native seed use. So, the first step is to measure the total land area planted with native species and the annual demand for native seed and plant materials.
As this report has shown, the uses of native seeds and plant materials vary widely. Some users aim to restore native plant ecology, while others seek to serve specific functions, such as soil conservation, pollination, or aesthetics. In effect the larger market for native seeds is composed of many submarkets of seed users with specific preferences. Users in some of those submarkets are more willing to substitute one species for another, meaning that they are more price sensitive. Research in the Colorado Plateau (Camhi et al., 2019) has found that where users are more open to substitutions (e.g., to meet a particular ecosystem function, like supporting rangeland grazing), they are more likely to choose seed that meets that goal at a lower price. By contrast, where seed demand must meet rigid specifications (e.g., to restore plant ecology with locally adapted genotypes), buyers are less willing to change species because of prices (so demand is more “price inelastic” in economist parlance). A quantitative, national assessment of native seed user requirements is needed to characterize those submarkets and how best to meet the component demands. Such a study should be done on a regional basis, not only because of the difference in land ownership regionally (e.g., more public land in the West), but also because certain uses are more urgent than others (e.g., establishing native rangeland species ahead of invasives versus planting roadsides with pollinator-friendly species).
Understanding future demand for native seeds calls for understanding past patterns. As wildfires have covered more acreage in the United States, the demand for seed to reestablish vegetative cover has grown. In recent years, it has become higher priority to meet that demand with native species—rather than exotics. On agricultural land too, the emphasis on native species has certainly expanded under the USDA Conservation Reserve Program. Thoughtful projection of future native seed needs will require an understanding of past patterns, both quantitatively and by species. This understanding must be paired with an awareness of how climate change is altering the demands for native seed.
Complementing demand-side studies there is a need to understand better the cost and time needed to produce native seed and plant material. Such information underpins the economic supply that makes native seed available. Here again, there is a need to study market segments, as costs of production will be strongly affected by such factors as the need for locally adapted genetics, availability of wild seed collection sites, plant life cycle (perennial versus annual), seed yields, and scale of production. Such production cost research would provide the basis for survey research on producer willingness to supply native seed under varying conditions.
Risk management is a high priority for producers of native seed and plant materials, as reported in the supplier survey here. Much risk research is needed at the regional level for key native species. Research to improve understanding of production and price risks would inform better designs for production and marketing contracts. To date, there have been important innovations, such as the BLM Indefinite Delivery Indefinite Quantity contracts and the USFS Blanket Purchase Agreements, but there exists a plethora of alternative contract designs that could be adapted to meet the needs of the market for native seeds. Separate from characterizing native seed production and market risks is the need for research to test the alternative contract designs at connecting market demand with producer supply.
BASIC SEED PRODUCTION INFORMATION FOR MORE SPECIES
Species-specific applied research is needed to improve the protocols for planting, growing, and harvesting many species. For many native grasses, production protocols are available and large quantities of seed can easily be produced using standard farming equipment. Native forbs are more problematic as they belong to a variety of plant families, with variable fruit and seed morphology and timing of ripening. Seed production may not begin until the second year or beyond, pollinator requirements may be unknown or may include native pollinators not present at the farm site, and insect and disease issues may emerge when the species is grown in a seed field monoculture (Cane, 2008; Shaw and Jensen, 2014). Very basic planting requirements (seeding date, rate, depth, etc.) must be determined, and specialized planting or harvesting equipment may be needed, when bringing new species into production. Stock seed supplies are often limited, necessitating an initial increase before field production can begin. The results of on-farm trial and error are usually unavailable to other growers of the same species. Conducting and disseminating applied research has considerable potential to expand the diversity and volume of native seeds for restoration.
MAINTAINING GENETIC INTEGRITY DURING CULTIVATION
Maintaining the genetic integrity of seed through the increase process is also an important concern. Native seed farming to increase amounts of seed sourced from wild populations aims to maintain genetic diversity but may cause unintended genetic changes, particularly when plants are grown under conditions quite different from the wild source population. Cultivated populations can become maladapted to conditions in the wild (Ensslin et al., 2015; Espeland et al., 2017; Havens et al., 2004; Husband and Campbell, 2004). In production, plants may receive irrigation, be protected from herbivores, and be grown in rich or fertilized soils and under novel climatic conditions that could make them less fit when reintroduced (Conrady et al., 2022; Espeland et al., 2017). For example, cultivated Carlina vulgaris and Jasione montana exhibited loss of tolerance for drought and competition (Ensslin et al., 2015), and farmed Clarkia pulchella (of non-certified seed) showed strong increases in mortality especially in simulated drought conditions (Pizza et al., 2021), although some other studies found less evidence for cultivation-induced losses of genetic integrity of native seed (Conrady et al., 2022).
Seed certification requirements (see Box 8-2) are designed to reduce genetic changes by limiting the number of generations that can be produced from stock seed. Since generations grown, species mating system, the production environment, and on-farm methodology all may differ and affect seed genetic integrity, more species-specific research is needed on genetic changes and how they can be managed during agronomic production.
SEED BIOLOGY AND SEED ANALYSIS
Accurate information about seed quality is essential for setting seed prices and calculating seeding rates. Seed tests that do not represent accurate seed quality affect costs and project success for users and income for producers. There are two difficulties in achieving quality information. First, there are federal, state, and private entities involved with analyzing and labeling native seed sold in the marketplace. Both regulations and laboratory quality across entities can be uneven. Second, the tests needed to assess quality are difficult to conduct accurately.
State seed laboratories in most states are members of the Association of Official Seed Analysts (AOSA)3 and follow AOSA seed analysis rules. State seed acts and regulations provide for truth in labeling and enforcement for seed lots of species covered by AOSA rules sold within the state. These requirements may differ across states. The Federal Seed Act (FSA) (USDA 1940 with revisions)4 takes precedence for seeds sold in interstate commerce but includes few native species. In addition to state seed laboratories there are commercial and private seed laboratories and a federal regulatory seed laboratory. There are several seed testing and accreditation programs to which seed laboratories and individual seed analysts may apply for accreditation.5 This section discusses these issues and newer technology that may help with solutions.
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3 See https://analyzeseeds.com/about-us (accessed February 10, 2023).
4 See https://www.ams.usda.gov/sites/default/files/media/Federal%20Seed%20Act.pdf (accessed February 10, 2023).
5 See https://www.betterseed.org/resources/seed-testing-accreditation-schemes/ (accessed February 10, 2023).
Labeling seed for sale requires results of germination, purity, and noxious weed seed tests and that the date of each test be listed on the seed tag. Percent germination includes the germinated, hard, and dormant seed in the tested sample. Purity testing requires examination of 2,500 seeds to determine the percent pure seed, other crop seed, weed seed, and inert material. A sample of 25,000 seeds is required for noxious weed testing and the species and number of seeds of each noxious species found must be listed. Seed lots cannot be transported through or offered for sale in a state if the seed lot contains a species that is either prohibited (Prohibited Weed Seed), or present in excess of the number per pound (Restricted Weed Seed) as designated in the state seed law. Seed lots cannot be sold if they contain any seeds of species designated as a restricted noxious in the state where sold. Testing must be conducted within the period specified by the FSA (if applicable) for interstate shipment and by the state where the seed is sold.
There are more than 900 native species with official AOSA germination rules (about 5% of the US native flora). For some other species there are unofficial protocols that have come into use but have not received formal review and acceptance. These are provided in an AOSA database: Test Methods for Species without Rules.6 For the many native species lacking any guidance, analysts often use procedures found in the literature or rules or protocols developed for members of the same genus or for species from similar habitats. The result is that for these species, different procedures may be used by different laboratories, often resulting in disparate results.
Seed quality data are essential for setting seed prices and calculating seeding rates. Because both initial germination and total viability (includes dormant seed) of native seed lots are often highly variable, seed price and seeding rates are generally calculated on a basis of pure live seed (PLS) per pound. PLS pounds in a seed lot = [% purity/100] × [% viability/100] × pounds of bulk seed. Seed tests that do not accurately represent actual seed quality affect costs and project success for users and income for producers. In addition, seeding rates calculated on such inaccurate tests will not represent the actual PLS seeded per area, leading to misinterpretations of seeding outcomes and monitoring data.
Discrepancies in test results can arise from several factors:
- The number of Registered Seed Technologists at seed laboratories may be insufficient to meet the needs of the native seed industry.
- Many species lack official testing rules or protocols; thus different laboratories may use different test procedures and obtain differing results.
- Analysts often have little or no experience with many native species that are only rarely submitted for testing.
- Germination tests for dormant seeds requiring cold or warm stratification may take weeks or months. A viability test using tetrazolium chloride (TZ) is often requested as a substitute for a germination test as it can be completed relatively rapidly. The TZ tests do not reflect germination ability, but rather whether the seed is alive or respiring, or not (total viability). The tests must be conducted by experienced analysts and can represent additional costs.
- Equipment availability and quality (e.g., germinators, balances, microscopes, seed herbaria) varies among laboratories.
Solutions to these problems will require seed biology research, leading to the development of additional AOSA rules. Increased laboratory accreditation and training of analysts in native seed testing could also contribute to more uniform results among laboratories. Improved funding to enable acquisition of high-quality equipment would reduce differences among analysts in their ability to identify seeds and evaluate test results. Blind referee tests can identify discrepancies in test results among laboratories and point to training needs. New technologies being developed for crop seed testing and variety development may lead to more consistent results and require far less time than current methods that require examination of individual seeds. X-ray imaging in combination with ad hoc image analysis software can be used to automatically calculate fill and seed weight. By calibrating the interpretation of x-ray images to germination results, it would be possible to determine viability without the need for destructive and time-consuming tests, such as germination and TZ. Moreover, computer vision and AI technology applied to seed images can aid in seed identification and recognition of defects. These techniques require extensive image galleries for individual species, and the greater morphological variability in wild populations compared to highly selected crop varieties create challenges.
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6 See https://analyzeseeds.com/test-methods-for-species-without-rules/ (accessed February 10, 2023).
DISCUSSION
Restoration ecology has existed as a scientific discipline since the first half of the 20th century, and has made many important strides, yet is also noted for suffering a substantial disconnect between science and practice (Burbidge et al., 2011; Cabin et al., 2010; Dickens and Sudling, 2013). In this chapter we have identified what we believe are the most important knowledge gaps that impede the ability of the native seed supply to develop more fully and function effectively.
Some of the knowledge gaps lie in the realm of investigator-driven, conceptually innovative research, which is traditionally supported by competitive funding from research agencies including the National Science Foundation and USDA-NIFA. To maximally influence the nation’s seed supply chain, such basic research will need to be carried out at large scales, and using environments and species, that reflect the real-world challenges and constraints of restoration practice.
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7 How AOSCA Tracks Wildland Sourced Seed, see https://www.aosca.org/programs and services (accessed December 30, 2022).
Other critical knowledge gaps lie in technical areas that are typically addressed by applied research organizations including USGS, USDA Agricultural Research Service, and others. While much applied research has already been carried out on many of the subjects the committee has discussed, there remains a need to identify solutions that are broader and more generally applicable—a nationwide system of seed zones being a notable example.
Conclusion 8-1: Many information gaps affect the ability of the native seed supply to function efficiently and effectively. Addressing them would inform decision making, reduce uncertainty, and improve restoration outcomes.
Conclusion 8-2: Important gaps in basic research include developing and testing strategies for seed sourcing that take rapid climate change into account; integration of traditional ecological knowledge into ecological restoration; and the role of species diversity, traits that contribute to survival, and the economics of the native seed industry.
Conclusion 8-3: Critical needs for the development and dissemination of improved technical knowledge include identifying basic growing requirements for more species, maintaining genetic integrity during cultivation, improved approaches to seed analysis, and greater use of seed certification.
Conclusion 8-4: Tribal leadership and collaboration are essential features of research on traditional ecological knowledge and tribal uses of native plant materials.
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