Collection and production of native seeds for ecological restoration

The global push to achieve ecosystem restoration targets has resulted in an increased demand for native seeds that current production systems are not able to fulfill. In many countries, seeds used in ecological restoration are often sourced from natural populations. Though providing seed that is reflective of the genetic diversity of a species, wild harvesting often cannot meet the demands for large‐scale restoration and may also result in depletion of native seed resources through over harvesting. To improve seed production and decrease seed costs, seed production systems have been established in several countries to generate native seeds based on agricultural or horticultural production methods or by managing natural populations. However, there is a need to expand these production systems which have a primary focus on herbaceous species to also include slower maturing shrub and tree seed. Here we propose that to reduce the threat of overharvest on the viability of natural populations, seed collection from natural populations should be replaced or supplemented by seed production systems. This overview of seed production systems demonstrates how to maximize production and minimize unintended selection bias so that native seed batches maintain genetic diversity and adaptability to underpin the success of ecological restoration programs.     

Ensuring seed quality in ecological restoration: native seed cleaning and testing

Seeds are a critical and limited resource for restoring biodiversity and ecological function to degraded and fragmented ecosystems. Cleaning and quality testing are two key steps in the native seed supply chain. Optimizing the practices used in these steps can ensure seed quality. Post‐collection handling of seeds can have a profound impact on their viability, longevity in storage, and establishment potential. The first section of this article describes seed cleaning, outlines key considerations, and details traditional and novel approaches. Despite the growth of the native seed industry and the need for seed quality standards, existing equipment and standards largely target agricultural, horticultural, and commercial forestry species. Native plant species typically have complex seed traits, making it difficult to directly transfer existing cleaning and quality standards to these species. Furthermore, in ecological restoration projects, where diversity is valued over uniformity crop standards can be unsuitable. We provide an overview and recommendations for seed quality testing (sampling, purity, viability, germinability, vigor), identity reporting, and seed transfer as well as highlight the need to implement internationally recognized standards for certification for native seeds. Novel and improved cleaning and testing methods are needed for native species from a range of ecosystems to meet the challenges and goals of the United Nations Decade on Ecosystem Restoration. The guidelines outlined in this article along with others in the Special Issue of Restoration Ecology “Standards for Native Seeds in Ecological Restoration” can serve as a foundation for this critical work.     

How policies constrain native seed supply for restoration in Brazil

Large‐scale ecological restoration programs across the world involve a voluminous demand for native seeds of diverse native plant species. In this article, we explore how institutional systems have operated and impacted native seed supply in Brazil. Native seed supply for restoration is essentially a community‐based activity which faces broad barriers to operating within regulations because of requirements for excessive and costly technical documentation, scarcity of seed laboratories, and lack of instructions for native seed quality testing. Although decentralized seed networks have stimulated arrangements for local organizations to promote seed supply, policies constrain the development of local capacities and the ongoing sustainability of these organizations. These conditions have resulted in a vast network of informal collectors and producers who are largely “invisible” and unknown to the regulatory authorities. Policies have decentralized responsibilities from the state without devolving decision‐making power to the multiple stakeholders engaged in policy elaboration. The policies maintain the centralized regulation of native seed supply. After examining Brazilian seed networks' experiences and conducting discussions with stakeholders and experts, we suggest adapting the current regulations to more local level contexts, encompassing the following strategies: (1) ensuring native seed origin and identity; (2) relaxation of the laboratory accreditation process for native seed quality assurance; (3) fostering seed markets for restoration; (4) research to provide technological innovation; (5) supporting local, diverse, and small seed‐based businesses.     

On principles and standards in ecological restoration

The Society for Ecological Restoration (SER) has long debated how to define best practices. We argue that a principles‐first approach offers more flexibility for restoration practitioners than a standards‐based approach, is consistent with the developmental stage of restoration, and functions more effectively at a global level. However, the solution is not as simple as arguing that one approach to professional practice is sufficient. Principles and standards can and do operate effectively together, but only if they are coordinated in a transparent and systematic way. Effective professional guidance results when standards anchored by principles function in a way that is contextual and evolving. Without that clear relation to principles, the tendency to promote performance standards may lead to a narrowing of restoration practice and reduction in the potential to resolve very difficult and diverse ecological and environmental challenges. We offer recommendations on how the evolving project of restoration policy by SER and other agencies and organizations can remain open and flexible.     

Optimising seed processing techniques to improve germination and sowability of native grasses for ecological restoration

• Grasslands across the globe are undergoing expansive degradation due to human impacts and climate change. If restoration of degraded native grassland is to be achieved at the scale now required, cost‐effective means for seed‐based establishment of grass species is crucial. However, grass seeds present numerous challenges associated with handling and germination performance that must be overcome to improve the efficiency of seeding. Previous research has demonstrated that complete removal of the palea and lemma (husk) maximises germination performance, hence we investigated the effects of complete husk removal on seed handling and germination of four temperate Australian grass species.
• Three techniques were tested to remove the husk – manual cleaning, flaming or acid digestion (the latter two followed by a manual cleaning step); these techniques were refined and adapted to the selected species, and germination responses were compared.
• The complete removal of the husk improved seed handling and sowability for all species. Germination was improved in Microlaena stipoides by 19% and in Rytidosperma geniculatum by 11%. Of the husk removal methods tested, flaming was detrimental to seed germination and fatal for one species (R. geniculatum). Compared to manual cleaning, sulphuric acid improved the overall efficacy of the cleaning procedure and increased germination speed (T50) in Austrostipa scabra, Chloris truncata and M. stipoides, and improved final germination in R. geniculatum by 13%.
• The seed processing methods developed and tested in the present study can be applied to grass species that present similar handling and germination performance impediments. These and other technological developments (seed coating and precision sowing) will facilitate more efficient grassland restoration at large scale.

     

Seed use in the field: delivering seeds for restoration success

Seed delivery to site is a critical step in seed‐based restoration programs. Months or years of seed collection, conditioning, storage, and cultivation can be wasted if seeding operations are not carefully planned, well executed, and draw upon best available knowledge and experience. Although diverse restoration scenarios present different challenges and require different approaches, there are common elements that apply to most ecosystems and regions. A seeding plan sets the timeline and details all operations from site treatments through seed delivery and subsequent monitoring. The plan draws on site evaluation data (e.g. topography, hydrology, climate, soil types, weed pressure, reference site characteristics), the ecology and biology of the seed mix components (e.g. germination requirements, seed morphology) and seed quality information (e.g. seed purity, viability, and dormancy). Plan elements include: (1) Site treatments and seedbed preparation to remove undesirable vegetation, including sources in the soil seed bank; change hydrology and soil properties (e.g. stability, water holding capacity, nutrient status); and create favorable conditions for seed germination and establishment. (2) Seeding requirements to prepare seeds for sowing and determine appropriate seeding dates and rates. (3) Seed delivery techniques and equipment for precision seed delivery, including placement of seeds in germination‐promotive microsites at the optimal season for germination and establishment. (4) A monitoring program and adaptive management to document initial emergence, seedling establishment, and plant community development and conduct additional sowing or adaptive management interventions, if warranted. (5) Communication of results to inform future seeding decisions and share knowledge for seed‐based ecological restoration.     

Seeding the future – the issues of supply and demand in restoration in Australia

It has been almost 15 years since concerns about the limited capacity of remnant native vegetation to supply the volumes of seed required to meet increasing restoration demands were first raised. Since that time little progress has been made towards addressing this constraint with the ongoing decline of native vegetation communities, especially since 2000, further challenging seed supply. We provide examples of the size of this demand for seed, as well as major issues associated with seed sourcing. We also discuss how invoking the concept of market forces to drive seed supply and demand is inappropriate and highlight the need for an industry body to oversee seed collection and utilisation standards. We further propose key actions that are required to secure the seed supply chain within the next 20 years to meet existing and future restoration targets. We argue that concerted, coordinated action at Commonwealth, State and regional levels are required to underpin effective future restoration outcomes.     

Seed storage: maintaining seed viability and vigor for restoration use

Effective seed storage after sourcing (harvesting or purchasing) is critical to restoration practitioners and native seed producers, as it is key to maintaining seed viability. Inadequate seed storage can lead to a waste of both natural and economic resources when seeds of poor quality are sown. When working with native species with unknown storage behavior, general assumptions can be made based on studies on related species, and standard practices may be applied with caution; however, an investigation should be conducted to understand if specific storage requirements are needed and for how long seeds can be stored before they lose significant viability. In this paper of the Special Issue Standards for Native Seeds in Ecological Restoration, we provide an overview of the key concepts in seed storage and the steps to take for effective storage of native seeds for restoration use.     

National standards: Reasserting the ecological restoration framework in uncertain times

National ecological restoration standards – produced in 2016 through the collaboration of 13 of Australia's leading ecological restoration organisations – are increasingly influencing practitioners. This paper elucidates two of the Key Principles that underpin standards to encourage highest and best efforts across all sectors and help resolve uncertainty about the role of restoration in a changing world.     

Lack of adequate seed supply is a major bottleneck for effective ecosystem restoration in Chile: friendly amendment to Bannister et al. (2018)

We argue that the need for a quality seed supply chain is a major bottleneck for the restoration of Chile's native ecosystems, thus supplementing the list of bottlenecks proposed by Bannister et al. in 2018. Specifically, there is a need for defining seed transfer zones, developing standards and capacities for properly collecting and storing seeds, reducing information gaps on seed physiology and longevity, and implementing an efficient seed supply chain with certification of seed origin and quality. Without such capacities, countries are unlikely to meet their restoration commitments. Although we focus on bottlenecks in Chile, the issues we raise are relevant to other countries and thus the global agenda for ecological restoration.     

Rapid evolution in native plants cultivated for ecological restoration: not a general pattern

• The growing number of restoration projects worldwide increases the demand for seed material of native species. To meet this demand, seeds are often produced through large‐scale cultivation on specialised farms, using wild‐collected seeds as the original sources. However, during cultivation, plants experience novel environmental conditions compared to those in natural populations, and there is a danger that the plants in cultivation are subject to unintended selection and lose their adaptation to natural habitats. Although the propagation methods are usually designed to maintain as much natural genetic diversity as possible, the effectiveness of these measures have never been tested.
• We obtained seed of five common grassland species from one of the largest native seed producers in Germany. For each species, the seeds were from multiple generations of seed production. We used AFLP markers and a common garden experiment to test for genetic and phenotypic changes during cultivation of these plants.
• The molecular markers detected significant evolutionary changes in three out of the five species and we found significant phenotypic changes in two species. The only species that showed substantial genetic and phenotypic changes was the short‐lived and predominantly selfing Medicago lupulina, while in the other, mostly perennial and outcrossing species, the observed changes were mostly minor.
• Agricultural propagation of native seed material for restoration can cause evolutionary changes, at least in some species. We recommend caution, particularly in selfing and short‐lived species, where evolution may be more rapid and effects may thus be more severe.

     

Factoring restoration practitioner perceptions into future design of mechanical direct seeders for native seeds

The methods used to distribute seeds influence the success of a restoration project. We surveyed 183 restoration practitioners from across the globe with the aim of identifying common limitations to the effective use of mechanical direct seeding in large‐scale restoration practice to highlight avenues for design improvement to mechanized seeding equipment. Results from this survey show that direct seeding methods are commonly used for ecological restoration and agree with other studies that suggest the method can achieve results much quicker and cheaper than the alternative of distributing nursery‐grown tube stock. However, this study indicates that current mechanical direct seeding methods lack adequate control of seed sowing depth and spatial distribution and highlight that the inability to sow seeds of varying morphology over complex topography are common limitations to direct seeding. To improve restoration success, engineering improvements to mechanical direct seeders used in large‐scale restoration should focus in particular on addressing issues of precision of delivery for diverse seed types and landscapes.     

Native seed trade of herbaceous species for restoration: a European policy perspective with global implications

With the need to meet ambitious restoration targets, an improved native seed sector for the production of herbaceous species with a practical and supportive policy framework is recognized. We evaluated the current “ready‐made” policy frameworks in Europe regarding the native seed supply of herbaceous species and found them to be, generally, unsatisfactory for both producers and users. Initially, such policies were designed for fodder seed and relate to distinctness, uniformity, and stability, traits that do not reflect the genetic heterogeneity of native species required for ecological restoration. Until recently, more suitable certification standards were designed to multiply fodder seed for preservation of the natural environment; however, due to the disparateness of the seed market in Europe, this policy is rarely practical and fails to encompass all herbaceous native species often resulting in unregulated seed sales. We recommend a new or adapted native seed policy constructed through a participatory or bottom‐up approach and supported through the formation of widely based trade associations. Such a policy could stimulate the native seed trade with concomitant impacts on the speed of improving ecosystem services.     

Long‐term effects of prairie restoration on plant community structure and native population dynamics

The key to restoring degraded grassland habitats is identifying feasible and effective techniques to reduce the negative impacts of exotic species and promote self‐sustaining native populations. It is often difficult to extend monitoring of restoration efforts to evaluate long‐term success, but doing so is essential to understanding how initial outcomes change over time. To assess how initial treatment effects persist, we revisited degraded patches of Pacific Northwest prairie habitat 6 years after experimental restoration efforts ceased. We evaluated plant community composition to determine the lasting effects of supplemental native seeding and disturbance treatments (burning, mowing, and herbicide to reduce exotic species). We tracked the persistence of seeded species and measured spread of their populations to evaluate suitability of species for restoration and the ability of the habitat to support native plant populations. We found that plots that received supplemental seeding continued to exhibit higher richness of native species than those left unseeded, and that both seeding and disturbance treatments could positively influence native species abundance over the long term. The initially observed effects of disturbance treatments on reducing exotic grass abundance had diminished, highlighting the importance of long‐term monitoring and ongoing control of exotic species. Nevertheless, these treatments significantly influenced the population trajectories of 4 out of 8 seeded native species. There was evidence of spatial advance of most seeded species. Results from extended monitoring confirm that dispersal limitation of native species and difficulties maintaining the reduction of exotic grasses continue to be major barriers to success in restoration of invaded grasslands.     

Message in a bottle: Inadvertent loss of seeds of native grassland species as a result of rudimentary long‐term storage

Many practitioners are likely to have collected seeds with the intention of using that seed for conservation and/or restoration plantings, but have not got around to using the seed, sometimes for many years. Currently, it is not clear what species have short‐lived or long‐lived seed when stored under rudimentary conditions such as in paper bags or in a refrigerator. We report the germinability of 12 temperate native grassland species, comprising 16 populations, whose seeds were collected with the purpose of raising seedlings to plant into the wild, but whose seeds were subsequently stored at ~2–4°C for 25+ years. We conclude that most of the grassland species that we assessed do not have viable seed after 25 years when stored in such conditions; only two species germinated despite evidence that seed germinates well for most species when first collected. Inadvertent loss of seeds of as a result of long‐term storage is most likely in readily germinable species (e.g. members of the Asteraceae). The ways in which seeds are stored by practitioners deserves consideration given the risk of seed mortality with long‐term storage under rudimentary conditions.     

Overcoming challenges on using native seeds for restoration of megadiverse resource‐poor environments: a reply to Madsen et al.

Madsen et al. (2016) reviewed several major limiting factors to establishment of seedlings in nonforest ecosystems (NFE), and proposed seed enhancement technologies to overcome these restoration barriers. However, biodiverse nutrient‐poor NFE present additional hurdles that preclude landscape‐scale seed‐based restoration and were not mentioned in their review. Here, we discuss issues related to native seed availability and provenance, and shortfalls in knowledge on seed quality testing and dormancy release that severely hamper restoration of degraded nutrient‐impoverished NFE. We present alternatives for overcoming these challenges and highlight the need for investments to find more practical and cost‐effective options for broad‐scale restoration.     

Seed Menus: An integrated decision‐support framework for native plant restoration in the Mojave Desert

The combination of ecosystem stressors, rapid climate change, and increasing landscape‐scale development has necessitated active restoration across large tracts of disturbed habitats in the arid southwestern United States. In this context, programmatic directives such as the National Seed Strategy for Rehabilitation and Restoration have increasingly emphasized improved restoration practices that promote resilient, diverse plant communities, and enhance native seed reserves. While decision‐support tools have been implemented to support genetic diversity by guiding seed transfer decisions based on patterns in local adaptation, less emphasis has been placed on identifying priority seed mixes composed of native species assemblages. Well‐designed seed mixes can provide foundational ecosystem services including resilience to disturbance, resistance to invasive species, plant canopy structure to facilitate natural seedling recruitment, and habitat to support wildlife and pollinator communities. Drawing from a newly developed dataset of species distribution models for priority native plant taxa in the Mojave Desert, we created a novel decision support tool by pairing spatial predictions of species habitat with a database of key species traits including life history, flowering characteristics, pollinator relationships, and propagation methods. This publicly available web application, Mojave Seed Menus, helps restoration practitioners generate customized seed mixes for native plant restoration in the Mojave Desert based on project locations. Our application forms part of an integrated Mojave Desert restoration program designed to help practitioners identify species to include in local seed mixes and nursery stock development while accounting for local adaptation by identifying appropriate seed source locations from key restoration species.     

Ten years of native seed certification in Germany – a summary

Many renaturation projects and compensation areas are based on the use of seeds from regional indigenous wild plants; in the following: native or regional seeds. Despite this, such seeds make up only a small proportion of the total number of seeds used for greening projects; in Germany, for example, it is only around 1% (=200 t per year). Although the market for regional seeds is small, it is highly competitive. High‐priced native seeds compete with flower mixes of unspecified origin and can only be differentiated from them by reliable quality seals. A quality assurance system based on seed legislation (EU Directive 2010/60, preservation mixtures) has been developed in a few European countries. However, quality assurance ends with the sale of the seeds. Thus, seed use remains unmonitored, and often unsuitable material, or material foreign to the region, is planted in restoration areas. Unfortunately, nature conservation has not made seed‐based restoration one of its key issues, neither at the European nor at the national level. Currently there are many different local and regional standards, methods and private certificates that are confusing for users and which provide little continuity and predictability for producers. We recommend the establishment of an EU directive or a broadly agreed recommendation to the EU member states, spearheaded by nature conservation, which would define the standards for producing and using native seeds (e.g. harmonised regions that cross national borders, quality regulations). At the same time, wild plant interest groups should combine existing structures in order to strengthen seed‐based restoration through international cooperation.     

Informing native plant sourcing for ecological restoration: cold‐hardiness dynamics,flowering phenology,and survival of Eriogonum umbellatum

Despite advances in restoration of degraded lands around the world, native plants are still underutilized. Selection of appropriate plant materials is a critical factor in determining plant establishment and persistence. To better inform decision‐making, we examined cold‐hardiness dynamics, flowering phenology, and survival among five geographically distinct sulfur‐flower buckwheat (Polygonaceae: Eriogonum umbellatum Torr.) populations in a common garden. LT₅₀ (a measure of freezing injury) was determined every 6 weeks across a complete year; one population was also evaluated at the source. Cold‐hardiness dynamics were similar across populations, with annual fluctuations in mean LT₅₀ exceeding 40°C. Rate of deacclimation (i.e. loss of cold tolerance) in spring varied across populations and was not related to the elevation from which a population came. Plants were less cold hardy in October 2014 compared to October 2013, likely reflecting a response to colder local conditions in 2013. Although the range of LT₅₀ was similar for a single comparison of common garden versus wild‐grown plants, wild‐grown plants acclimated and deacclimated earlier than common garden‐grown plants. Plants derived from a low‐elevation population showed delayed flowering phenology, while high‐elevation populations showed earlier flowering phenology, with one high‐elevation population having the lowest survival rate in the common garden. These results suggest that while considerable plasticity in seasonal cold‐hardiness dynamics occur, population variability in deacclimation and flowering phenology have implications for selection and movement of sulfur‐flower buckwheat for ecological restoration.