Research and Publications
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.
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.
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 the availability of adequate seed supplies of species and sources appropriate for restoration projects and programs necessitates extensive science‐based planning. The selection of target species requires a review of disturbance conditions and reference areas, development of a reference model, and consideration of specific objectives, timeframes, available resources, and budgets as well as the performance of prospective species in past restoration efforts. Identification of seed sources adapted to site conditions is critical to provide for short‐term establishment and long‐term sustainability. Seed zones and plant movement guidelines provide tools for sourcing plant materials with reduced risk of maladaptation. A seed zone framework also facilitates seed use planning and contributes to stability and predictability of the commercial market, thereby reducing costs and improving the availability of adapted seed supplies. Calculating the amount of seed required for each species is based on seed quality (viability, purity), seed weight, expected seedling establishment, and desired composition of the seeding. If adequate collections from wildland stands are not feasible, then seed increase in seed fields or use of nursery stock may be warranted. Adherence to seed collection and seed production protocols for conserving genetic diversity is critical to protect genetic resources and buffer new seedings and plantings against environmental stressors. Maintenance of genetic diversity becomes even more critical considering current or expected climate change impacts. Collaboration and partnerships can benefit seed selection and procurement programs through sharing of information, coordination in project planning, and increasing the availability of native seed.
Wildfires change plant community structure and impact wildlife habitat and population dynamics. Recent wildfire‐induced losses of big sagebrush (Artemisia tridentata) in North American shrublands are outpacing natural recovery and leading to substantial losses in habitat for sagebrush‐obligate species such as Greater Sage‐grouse. Managers are considering restoration strategies that include planting container‐grown sagebrush to improve establishment within areas using more conventional seeding methods. Although it is thought that planting sagebrush provides initial structural advantages over seeding, empirical comparisons of sagebrush growth are lacking between individuals established post‐fire using both methods. Using a Bayesian hierarchical approach, we evaluated sagebrush height and canopy area growth rates for plants established in 26 seeded and 20 planted locations within the Great Basin. We then related recovery rates to previously published nesting habitat requirements for sage‐grouse. Under average weather conditions, planted or seeded sagebrush will require 3 or 4 years, respectively, and a relatively high density (≥ 2 plants/m2) to achieve the minimum recommended canopy cover for sage‐grouse (15 %). Sagebrush grown in warmer and drier conditions met this cover goal months earlier. Although planted sagebrush reached heights to meet sage‐grouse nesting requirements (30 cm) one year earlier than seeded plants, seeded individuals were ~19 cm taller with 410 cm2 more canopy area than planted sagebrush after 8 years. However, big sagebrush establishment from seed is unreliable. Strategically planting small, high density patches of container‐grown sagebrush in historic sage‐grouse nesting habitat combined with lower density seedings in larger surrounding areas may accelerate sage‐grouse habitat restoration.
This handbook is a guide to developing realistic project plans and implementing appropriate management strategies by enhancing your understanding of basic shrub biology, ecological concepts,and management principles.
A resilience-based approach to management can facilitate regional planning by guiding the allocation of management resources to where they will have optimal socioecological benefits. This type of approach requires a sound understanding of the environmental factors, ecosystem attributes and processes, and landscape components that influence ecological resilience of the focal system. Chambers et al. review and integrate resilience concepts to help inform natural resources management decisions for ecosystems and landscapes. They describe the six key components of a resilience-based approach, beginning with managing for adaptive capacity and selecting an appropriate spatial extent and grain. Additional components include developing an understanding of the factors influencing the general and ecological resilience of ecosystems and landscapes, the landscape context and spatial resilience, pattern and process interactions and their variability, and relationships among ecological and spatial resilience and the capacity to support habitats and species. They suggest that a spatially explicit approach that couples geospatial information on general and spatial resilience to disturbance with information on resources, habitats, or species provides the foundation for resilience-based management. A case study from the sagebrush biome is provided that is widely used by the management agencies.
Rangeland managers need tools to control invasive annual grasses, particularly following wildfire. We assessed responses of native and invasive/exotic grasses to the MB906 soil amendment containing live cultures of a purportedly weed-suppressive strain of the bacterium Pseudomonas fluorescens (“WSB”). MB906 was applied alone and in combination with the pre-emergent herbicide imazapic on >3000 ha across three sagebrush-steppe landscapes burned several months prior. Replicate plots of each treatment type were established and plant cover was measured in the following three years. Cover of invasive-annual grasses (“IAG”) was not responsive to MB906 when all IAG species were considered (“IAG-All”). However, MB906 led to a 54% reduction in the IAG’s that were previously reported to be controlled by WSB (“IAG-Target”) in the second year following application (IAG-Target = cheatgrass, Bromus tectorum and medusahead, Taeniatherum caput-medusae; IAG-All also includes Vulpia myuros and Bromus arvensis). MB906 reduced the effectiveness of co-applied imazapic: Imazapic alone reduced IAG-All by 83% and 68% in years 1 and 2, respectively, while imazapic+MB906 reduced IAG-All by 48% and 38% in years 1 and 2, respectively, across all landscapes, and a similar response pattern was observed for IAG-Target. Perennial grass cover was unaffected by the treatments except where it increased 4-fold in response to imazapic applied at a high rate (0.140 kg a.i. ha−1) in one of the landscapes. Tank mixing MB906 and herbicide may have lessened the biological activity of the herbicide by altering the pH or mineral content of the spray solution or by direct metabolism of the herbicide by the bacteria. These results do not provide strong support for MB906 as a tool for annual grass control, though they suggest further investigation may be warranted.
Adaptive variation among plant populations must be known for effective conservation and restoration of imperiled species and predicting their responses to a changing climate. Common‐garden experiments, in which plants sourced from geographically distant populations are grown together such that genetic differences may be expressed, have provided much insight on adaptive variation. Common‐garden experiments also form the foundation for climate‐based seed‐transfer guidelines. However, the spatial scale at which population differentiation occurs is rarely addressed, leaving a critical information gap for parameterizing seed‐transfer guidelines and assessing species’ climate vulnerability. We asked whether adaptation was evident among populations of a foundational perennial within a single “empirical” seed‐transfer zone (based on previous common‐garden findings evaluating very distant populations) but different “provisional” seed zones (groupings of areas of similar climate and are not parameterized from common‐garden data). Seedlings from three populations originating from similar conditions within an intermediate elevation were planted into gardens nearby at the same elevation, or 250–450 m higher or lower in elevation and 0.4–25 km away. Substantial variation was observed between gardens in survival (ranging 2%–99%), foliar crown volume (7.8–22.6 dm3), and reproductive effort (0%–65%), but not among the three transplanted populations. The between garden variation was inversely related to climatic differences between the gardens and seed‐source populations, specifically the site differences in maximum–minimum annual temperatures. Results suggest that substantial site‐specificity in adaptation can occur at finer scales than is accounted for in empirical seed‐transfer guidance when the guidance is derived from broadscale common‐garden studies. Being within the same empirical seed zone, geographic unit, and even within 10 km distance may not qualify as “local” in the context of seed transfer. Moving forward, designing common‐garden experiments so that they allow for testing the scale of adaptation will help in translating the resulting seed‐transfer guidance to restoration projects.
Western US sagebrush ecosystems are threatened due to multiple interacting factors: encroachment by conifer woodlands, exotic annual grass invasion, severe wildfire, climate change, and anthropogenic development. Restoration of these communities is primarily focused on reducing conifer species such as western juniper, with the goal of increasing native herbaceous perennials and sagebrush and decreasing exotic annual grass invasion. Assessing the long-term success of restoration treatments is critical for informing future management and treatment strategies since short-term patterns do not generally predict long-term trends. Using a designed experiment from a Wyoming big sagebrush community that was established in 2008, we examined the long-term vegetation response to juniper removal and seeding (cultivar and local) in disturbed and undisturbed areas (slash pile, skid trails, no disturbance). We also examined the landscape scale plant response to juniper removal using repeatedly measured randomly located transects across two restoration units. We found that seeded species persisted in the long term and also mitigated exotic grass increases.