Peter W. Dunwiddie

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• Ph.D.
• Affiliate Professor at University of Washington

Local adaptation may facilitate range expansion during invasions, but the mechanisms promoting destructive invasions remain unclear. Cheatgrass ( Bromus tectorum ), native to Eurasia and Africa, has invaded globally, with particularly severe impacts in western North America. We sequenced 307 genotypes and conducted controlled experiments. We found...

Tribute to Estella B. Leopold

Grasslands are ubiquitous globally, and their conservation and restoration are critical to combat both the biodiversity and climate crises. There is increasing interest in implementing effective multifunctional grassland restoration to restore biodiversity concomitant with above- and belowground carbon sequestration, delivery of carbon credits and/...

Editorial on the importance of publication by managers of natural areas

Small dams on 3 of 4 natural lakes in the area near Pinedale, Wyoming created quantifiablr shoreline erosion due to water level fluctuations. Vegetative debris in the wash zone is locally derived. This is a brief paper on our findings.

The genetic diversity of germplasm used in reintroduction and restoration efforts can influence how resulting populations establish, reproduce, and evolve over time, particularly in disturbed and changing conditions. Regional admixture provenancing, mixing seeds derived from multiple populations within the same region as the target site, has been s...

Grasslands, woodlands, and associated communities comprise a biologically diverse ecoregion in western Oregon, Washington, and British Columbia. These habitats contrast conspicuously with the coniferous forests that largely surround them and were historically strongly shaped by a pronounced summer-dry Mediterranean climate together with frequent fi...

Pacific Northwest USA oak woodlands and savannas are fire-resilient communities dependent on frequent, low-severity fire to maintain their structure and understory species diversity, and to prevent encroachment by fire-sensitive competitors. The re-introduction of fire into degraded ecosystems is viewed as essential to their restoration, yet can be...

Understanding how plant community dynamics are impacted by altered disturbance regimes is a pressing challenge for restoration ecology. Most assessments of community dynamics involve computationally‐intensive statistical techniques, whilst management often defers to derived, qualitative “state‐and‐transition” models. Here, we demonstrate an interme...

This report presents the results of floristic surveys of small islands carried out in 2017-2018 in the San Juan Islands National Monument in Washington

1. Outcomes for butterfly conservation can hinge on interactions with host plants during early larval instars. Ontogenetic changes in larvae may cause predictors of survival to shift quickly over time. 2. Survival from instar to instar was measured for an endangered oligophagous butterfly, Euphydryas editha ssp. taylori (Taylor's checkerspot), whic...

Adaptive management (AM) was proposed as a rigourous and structured approach to natural resource management that increases learning and reduces uncertainty. It has been adopted as a guiding principle by agencies world‐wide, yet its usefulness for guiding management continues to be debated. We propose a new strategy, which we term staged‐scale resto...

Prescribed burning is a primary tool for habitat restoration and management in fire-adapted grasslands. Concerns about detrimental effects of burning on butterfly populations, however, can inhibit implementation of treatments. Burning in cool and humid conditions is likely to result in lowered soil temperatures and to produce patches of low burn se...

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 out...

Natural areas are often managed for the protection of native species and ecosystems. The presence of non-native species is generally perceived to run counter to these objectives; thus, they are often controlled or tolerated but rarely deliberately favored. We suggest greater emphasis be placed on the role species play in ecological settings regardl...

Rare species recovery presents several challenges for conservation managers, particularly when listed species interact with one another. We present a case study involving two such species: golden paintbrush (Castilleja levisecta) and Taylor's checkerspot butterfly (Euphydryas editha taylori), both of which occur in lowland prairies in the Puget Sou...

The revegetation of islands following retreat of Pleistocene glaciers is of great biogeographical interest. The San Juan Islands, Washington, feature regionally distinctive xerophytic plant communities, yet their vegetation history, as it relates to past climate and sea level, is poorly known. We describe a 13,700-year-old pollen record from Killeb...

Our study was undertaken to better understand how to increase the success rates of recovery plantings of a rare hemiparasite, golden paintbrush (Castilleja levisecta-Orobanchaceae). This species is endemic to western Washington and Oregon, USA, and southwestern British Columbia, Canada. Over 5000 golden paintbrush plants were outplanted as plugs in...

Data used in analyses. (XLSX)

Aim Darwin posed a conundrum about species invasions, postulating the importance of functional distinctiveness from the receiving native community to avoid competition, and, at the same time, the importance of shared similarity to pass environmental filters and successfully establish. Using phylogenetic distances and functional traits, we assessed...

Re-establishment of golden paintbrush (Castilleja levisecta) is a major restoration objective at many sites in the Pacific Northwest. However, reintroducing species is a time and resource intensive task, and it is imperative restoration is carried out as efficiently as possible. Reintroduction of golden paintbrush in South Puget Sound prairies over...

We compiled existing data and information to characterize the condition and trends in high priority natural resources in San Juan Island National Historical Park. This report, and the spatial datasets provided with it, is intended to inform and support park managers and scientists in developing recommendations for improving or maintaining natural r...

We compiled existing data and information to characterize the condition and trends in high priority natural resources in Ebey’s Landing National Historical Reserve (EBLA, or "the Reserve"). This report, and the spatial datasets provided with it, is intended to inform and support Reserve managers and scientists in developing recommendations for impr...

The objective of this project was to determine seed production and viability of plants sharing morphological traits of Castilleja levisecta (CALE) and C. hispida (CAHI). Fruiting stems were gathered from 25 putative CALE x CAHI hybrids and from one plant of each species, for a total of 27 maternal plants. Seed production and germination were assess...

The prairie and oak ecosystems of the South Puget Sound are some of the most fragmented and endangered ecosystems in North America. With a suite of endangered, threatened, and rare species across taxonomic lineages with multiple and sometimes conflicting needs, management and restoration can border on impossible. While fire presents its challenges,...

The occurrence of multiple rare species in the same habitat presents both opportunities and challenges. Both golden paintbrush (“GP”) (Castilleja levisecta – federally Threatened: 1997) and Taylor’s checkerspot (“TC”) (Euphydryas editha taylori – federally Endangered: 2013) historically occurred in lowland prairies in the Pacific Northwest, and cur...

Although it is well documented that the vast majority of native prairies in western Washington have disappeared, it is less clear to what extent the remaining fragments have been modified by the loss of native taxa. In this study, we focus on one group of plants—native annuals—that are notably lacking in prairies today. Based on current and histori...

The fundamental properties of organisms—what they are, how and where they live, and the biotic and abiotic interactions that link them to communities and ecosystems—are the domain of natural history. We provide examples illustrating the vital importance of natural history knowledge to many disciplines, from human health and food security to conserv...

Finding ecologically and economically effective ways to establish matrix species is often critical for restoration success. Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis) historically dominated large areas of western North America, but has been extirpated from many areas by large wildfires; its re-establishment in these areas ofte...

Background/Question/Methods Current grassland and heathland habitats of New England are relicts of the agricultural practices of early European settlers. While anthropogenic in origin, these habitats play a crucial role in maintaining biodiversity. Disturbance-based management techniques, such as burning and mowing, are used to prevent tree encroa...

Re-establishment of golden paintbrush (Castilleja levisecta) is a major restoration objective at many sites in the Pacific Northwest. In this study we assessed performance of outplanted plugs over five years at six sites in South Puget Sound. Specifically, we identified factors associated with increased survival, flowering, and new plant recruitmen...

Golden paintbrush (Castilleja levisecta), a hemiparasitic member of the Orobanchaceae, was historically found in lowland prairies in the Pacific Northwest. Reduced to only about a dozen sites in western Washington and British Columbia (extinct in Oregon), golden paintbrush was listed as a threatened species by the U.S. Fish and Wildlife Service in...

Although it is well documented that the vast majority of native prairies in western Washington have disappeared, it is less clear to what extent the remaining fragments have been modified by the loss of native taxa. In this study, we begin to provide insight by focusing on one group of 40 plants – native annuals – that are notably lacking in prairi...

QuestionMost results of restoration efforts are species-specific and/or site-specific and therefore are not general enough to be easily applied to other species and other sites. Our research addresses the issue of species-specific results by investigating the feasibility of using plant traits instead of taxonomic identity to characterize species re...

Background/Question/Methods Experiments under carefully controlled conditions have been criticized as having limited applicability because they do not adequately reflect the heterogeneity of natural environments. This heterogeneity, arising from multiple sources, can affect the magnitude and direction of ecological interactions. We evaluated the...

Background/Question/Methods The establishment of parasitic plants may be limited both by their requirements and by their host plants. These issues are magnified when the parasitic species is rare. Castilleja levisecta (golden paintbrush) is a federally threatened hemiparasite associated with one of the most endangered ecosystems in the United Sta...

In many ecosystems, restoration is increasingly focused on developing communities de novo, such as creating prairies in abandoned agricultural fields. These efforts often face formidable challenges in controlling invasive weeds, selecting appropriate native species to match local site conditions, developing effective methods to establish species as...

Repeated perturbations, both biotic and abiotic, can lead to fundamental changes in the nature of ecosystems, including changes in state. Sagebrush steppe communities provide important habitat for wildlife and grazing for livestock. Fire is an integral part of these systems, but there is concern that increased ignition frequencies and invasive spec...

Species interactions affect plant diversity through the net effects of competition and facilitation, with the latter more prevalent in physically stressful environments when plant cover ameliorates abiotic stress. One explanation for species loss in invader-dominated systems is a shift in the competition-facilitation balance, with competition inten...

The distribution of exotic species bearing fruits may depend in part on their palatability to birds because species attracting a more diverse array of dispersers should broadcast seed to a wider range of habitats, including those otherwise assumed to represent refuges from exotic species invasion, such as small islands. To test these ideas, we comp...

Successful conservation management requires an understanding of how species respond to intervention. Native and exotic species may respond differently to management interventions due to differences arising directly from their origin (i.e., provenance) or indirectly due to biased representations of different life history types (e.g., annual vs. pere...

Understanding a system's historical conditions is a key first step in mapping out restoration goals and strategies. We examined the age structure and stem density of a stand dominated by Garry oak (Quercus garryana) and Douglas-fir (Pseudotsuga menziesii), and related this structure to its environmental history. Our reconstruction was based on 139...

In Pacific Northwest prairies and oak woodlands, cessation of anthropogenic burning in the mid-1800s resulted in large-scale degradation and loss of habitat due to tree and shrub encroachment. Widespread invasive species, deep thatch accumulations, and extensive moss cover now limit the ability of native plants to germinate and thrive. These change...

We conducted a 5-year study at 10 sites from British Columbia to the Willamette Valley aimed at improving methods for restoring degraded prairies and oak savannas. Our manager-recommended treatment combinations were applied over 4 years and included the following components: spring and fall mowing, grass-specific and broad-spectrum herbicide, and f...

The last 100 years have seen a marked decline in Oregon white oak woodlands in the Puget Sound region. Efforts to restore the woodlands cannot hope to be successful unless the role fire has played in maintaining them in the past is understood. A fire scar chronology was constructed from a Pseudotsuga menziesii-Quercus garryana community within a 15...

The 24 papers in this issue of Northwest Science summarize research and management presented at a 2010 meeting convened by the Cascadia Prairie-Oak Partnership, a collaboration focusing on the prairie/oak ecosystems of the Willamette Valley-Puget Trough-Georgia Basin ecoregion. We present an overview that builds on these papers to consider future t...

Invasive plants, especially non-native perennial grasses, are a critical threat to remnant prairies and oak savannas in the Pacific Northwest. Managers must control non-native plants without adversely impacting native species in fragmented prairie remnants. We describe results of a collaborative experiment replicated at 10 sites along a 500 km lati...

Thousands of hectares of high quality sagebrush shrub-steppe burned in south-central Washington in 2000 and 2007, particularly on the Arid Lands Ecology Reserve (ALE) on the Hanford Reach National Monument. Extensive rehabilitation efforts took place on ALE to control invasive species and establish native species following each of these fires. Perm...

Background/Question/Methods The composition of plant communities depends on interactions between propagule availability (seed limitation) and propagule establishment (microsite limitation), both of which can be mediated by biotic and abiotic conditions (nutrient availability, climate, competition from resident species). Successful restoration of...

Numerous papers describe the biology of invasive plants and control techniques for addressing site-specific infestations. However, few studies describe the practical steps and components needed to control invasives at a larger, more ecologically-meaningful scale. The Skagit Knotweed Working Group was formed in 2000 to control Japanese knotweed (Pol...

Predicted changes in climate present unusual challenges to conservation planners, land managers, and restoration efforts directed toward preserving biodiversity. Successful organisms will respond to these changes by persisting in suitable microsites, adapting to novel conditions, or dispersing to new sites. We describe three general categories of s...

To conserve or restore culturally significant plants, one must consider the important role that indigenous land management techniques have played in maintaining habitats of those species. Beargrass (Xerophyllum tenax) is a basketry plant used by Native Americans and is reportedly declining in traditional gathering sites. Many low-elevation beargras...

Invasive plants, especially nonnative perennial grasses, pose one of the most critical threats to protected prairies and oak woodlands in the Pacific Northwest. Our current knowledge regarding the effectiveness of weed control methods, especially in sites that retain a significant component of native vegetation, is largely anecdotal or based on res...

Japanese knotweed, Sakhalin knotweed, and their hybrid, Bohemian knotweed, are invasive across much of the United States. Monocultures formed by these species threaten natural riparian areas, and effective methods of control are being sought. Injection of herbicide is a relatively new control technique with no known published results. Bohemian knot...

A series of interacting steps resulted in the use of the wrong species in a prairie restoration. Contributing factors included misidentifying species of fescue, combining seeds from nearby sites, favoring the collection of seeds from one species over another in the wild as well as in the nursery, and compounding the preferential selection of a spec...

Vascular plant species lists were compiled for all the major prairies that remain in south Puget Sound, Washington State, USA. Overall, 278 species were recorded in 15 prairies that ranged in area from 12-3,000 ha. Fifty-nine percent of these were native taxa, with forbs the most frequently represented life form (74%). Seventy percent of the specie...

Vernal pools are common on the Columbia Plateau of eastern Washington, where they occur on basalt bedrock within the channels scoured by the Pleistocene Missoula Floods. This is the first extensive floristic survey of these pools. Eighty-five percent of the 283 plant taxa are native, and the majority of these are annual. The Washington vernal pools...

A native grassland dominated by Roemer's fescue (Festuca idahoensis var. roemeri), great camas (Camassia leichtlinii), and a diversity of other forbs has been the focus of a variety of experiments on restoration techniques, as well as studies tracking ecological changes since 1981. Investigations in existing grasslands have primarily focused on res...

Factors contributing to an invasion of the Asian woody vine Celastrus orbiculatus in a mesic forested Massachusetts (USA) sanctuary were investigated. Planting germinated C. orbiculatus seeds in the field revealed that, although they tolerate a wide range of conditions, seedlings grow largest in moist circumneutral soil under high irradiance. A stu...

We present a long-term assessment of a bald eagle (Haliaeetus leucocephalus) population from a wintering site in the U.S. Pacific Northwest. Eagles were counted weekly between 1978 and 2000 on a 19-km reach of the Skagit River, and on a contiguous 24-km upriver reach between 1982 and 2000. Eagles typically occurred in greatest numbers from mid-Dece...

In 1983 four 0.25 hectare (ha) plots were established in Ram Pasture, Nantucket Island, MA, to evaluate methods of maintaining coastal sandplain grasslands. Cover and frequency of vascular plants were measured in the plots prior to treatments and annually thereafter. One plot was burned in April, one was burned in August, one was mowed in August, a...

In 1990, vegetation cover and frequency in thirty-one 0.2-m2 quadrats in an ungrazed coastal sandplain in Massacussetts (USA) were compared with cover and frequency in matched quadrats in an adjacent grassland that had been used as a sheep pasture until 1948. Species that had significantly higher values of cover or frequency in the former pasture i...

We surveyed forests in Massachusetts to identify any remaining old-growth stands. We located twenty-eight tracts in western Massachusetts that met our criteria, with one additional site east of the Connecticut River. Hemlock and northern hardwoods in excess of 150-200 years dominate most sites, which range in area from 3-28 ha. Most stands occur on...

A set of 372 vegetation relevés was collected from coastal sandplain communities on Nantucket, Cape Cod, and Martha's Vineyard. Sites on Nantucket had the highest average number of rare species and the lowest number of non-native species. We used TWINSPAN to identify major vegetation types from these data. The first division separated the samples i...

Historical management practices can have a major effect on the current trends in land use and vegetation cover. This National Park Service report dives into the historical record comparing written accounts of the landscape back to the 1600’s, photographs from the late 1800’s onward and evidence of recent (~100yrs.) fires from tree cores in the area...

summaryThe effects of spatial isolation on pollen representation were examined in a study of seven small kettle ponds on Block Island, a small, unforested island 19 km off the New England Coast (USA). Modern pollen assemblages from the ponds were compared with modern assemblages from similar ponds on the adjacent, partly forested mainland and in ex...