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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 threats and conservation priorities in these systems. Human population growth, encroachment by woody vegetation, the spread of invasive non-native organisms, and climatic changes all will provide future challenges. Developing and implementing techniques to abate these threats will require effective collaboration, creative research, and innovative management of natural areas. One priority will be the restoration of highly degraded habitats to increase acreage of native ecosystems, create buffers, and enhance connectivity. Other priorities will focus on detecting and eradicating newly-arrived invasives, enhancing species diversity and habitat heterogeneity, and increasing ecological resilience. Long-term commitments and investments are critical. Developing realistic restoration goals will be particularly challenging, especially when assembling new communities from the ground up, and in a world with a rapidly changing climate. To assist with goal development, we propose a system for conceptualizing restoration goals so that their relative merits can be more easily compared when deciding amongst them. We suggest evaluating goals along two continua, one related to management intensity (ecological goals) and the other to ecological impacts (cultural goals). We conclude by suggesting some specific restoration and management principles that may help to further guide conservation action, and that point toward critical information needs for future research.
Land survey data recorded by the General Land Office between 1851 and 1910 were used to map historical vegetation in the Willamette Valley, Oregon. Of the 202 townships included in our study area, 148 (73%) were surveyed between 1851 and 1855. Widespread but dispersed and small-scale Euro-American settlement preceded the surveys by 5 years or more, but census records indicate that farming and logging at the time of survey had affected less than 4 and 0.5 percent of the valley, respectively. Native habitats presumably were grazed to an unknown extent by free-ranging livestock, but not otherwise disturbed by drainage or plowing. Ten vegetation classes were mapped, comprised of 66 subclasses. Prairie covered the largest area, followed in diminishing order by upland forest, savanna, woodland, riparian and wetland forest, water, shrubland, emergent wetlands, unvegetated, and herbaceous upland. Distribution of vegetation classes reflected gradients in precipitation, hydrology, soil moisture, topography, and fire frequency. In general, prairie occupied a central position in the valley surrounded by more or less concentric bands of savanna, woodland, and closed forest. Prairie and savanna dominated the southern and central valley, while forest and woodland were more abundant in the northern portion of the valley. To some extent, woodland may have been savanna under an earlier Native American fire regime. All subclasses except coniferous forest have declined in area since 1850.
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 155 ha study site on southeast Waldron Island, Washington. Sixty-two scars were identified on 15 crossdated Pseudotsuga samples that documented fire events between 1530 and 1908. A master tree-ring chronology was created for the period 1685 to 2004. Composite fire intervals and individual-tree fire intervals were used to characterize the fire history. Seasons of past fires were determined by analyzing fire scar position within annual ring structure. For the historical period 1700–1879, the composite mean fire return interval (FRI) was 7.4 yrs, and the mean individual-tree FRI was 18.4 yrs. The historic period mean individual-tree FRI was 18.4 yrs. In contrast, only three fires were recorded during the settlement/modern period (1880–2004), resulting in a mean individual-tree FRI of 103.8 yrs. Seasonality of past fires indicates that most fires occurred during late summer and fall. No evidence of spring or early summer burning was detected. Our study of the fire history for a site on Waldron Island shows a marked reduction in fire frequency between the historical and settlement/modern period, which we interpret as reflecting declines in Native American population size and activity and the eventual cessation of deliberate ignitions by Native Americans.
The Pacific Northwest, a region known for mesic coniferous forests, is also home to scattered prairies, which have been maintained by a combination of xeric site conditions and anthropogenic fires. These prairies, which existed for thousands of years, have been reduced to 2–4% of their historical extent over the past two centuries due to urban development, agriculture, and forest encroachment. We used soil properties, including organic matter concentration, black carbon concentration, proportion of large black carbon particles and moist color, to determine the historical location of prairie-forest ecotones at Mima Mounds and American Camp prairies. Based on these parameters, we conclude that Mima prairie historically extended 50 m north and 300 m east of the current ecotone. In contrast, at American Camp all sampled areas that are currently forested appear to have been grassland at some time in the past. Soils can provide an effective means of determining historical prairie boundaries.
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 increment cores and 197 stem cross-sections collected from trees in 21 plots. Individuals of both species were more than 200 years old, indicating that the stand had a mixed composition for centuries. The historical tree density was ca. one-tenth that present prior to restoration (oak release) activities. This open oak/Douglas-fir savanna was maintained for centuries by fires set by Native Americans. It began to infill with oak, and later Douglas-fir, in the 1800s, particularly following Euro-American settlement in the 1860s. Douglas-fir encroachment continued throughout the 1900s, with a very large cohort becoming established in the early 1970s. This recent wave of recruitment has occurred in many sites in the region, and may reflect interactions among climatic and environmental conditions, together with changes in land use, including the cessation of livestock grazing and logging. Oak release actions were undertaken to re-open the forest structure, and involved the removal of 55% of the trees, primarily small-diameter Douglas-fir. Comparisons with historical information suggest that the post-release stand is still much denser and biased towards Douglas-fir than the stand was historically.
Although Oregon white oak (Quercus garryana) woodlands are a characteristic landscape component in southwestern Oregon, little is known about their current or historical stand structures. Meanwhile, fuel reduction thinning treatments that change stand structures in non-coniferous communities are ongoing and widespread on public lands in this region; some of these treatments also have restoration objectives. Managers need baseline information on which to base prescriptions that have a restoration focus. We inventoried 40 Oregon white oak dominated woodlands across two study areas in southwestern Oregon, and describe here their stand characteristics and age structures. We assessed whether these varied systematically with site conditions or recorded fire history. Stands included various proportions of single- and multiple-stemmed trees and a range of tree densities and diameter- and age-class distributions. Variables that may indicate site moisture status were weakly associated with multivariate gradients in stand structure. Peak establishment of living Oregon white oaks generally occurred during 1850–1890, sometimes occurred in the early 1900s, and recruitment rates were low post-fire suppression (∼1956). Recruitment of sapling-sized oak trees (< 10 cm diameter at breast height, ≥ 1.3 m tall) was generally low and their ages ranged from 5 to 164 yr; they were not necessarily recent recruits. The observed wide range of variability in stand characteristics likely reflects the diversity of mechanisms that has shaped them, and suggests that a uniform thinning approach is unlikely to foster this natural range of variability.
Many land managers are interested in maintaining or restoring plant communities that contain Oregon white oak (OWO, Quercus garryana), yet there is relatively little information available about the species' growth rates and survival to guide management decisions. We used two studies to characterize growth (over multi-year periods and within individual years) and to evaluate the main factors that affect growth and survival. The objective of the first study was to revise the OWO components of the Forest Vegetation Simulator (FVS), a widely-used growth model. We first compiled a large database on growth and survival to develop equations to revise FVS. Diameter growth and survival over multi-year periods were strongly affected by stand density, the competitive position of the tree, tree size, and site productivity. The height growth potential of OWO was predicted from site productivity, stand density and tree size. In the second study, intra-annual patterns of OWO growth were evaluated by precisely measuring stem diameters with band dendrometers. OWO experienced two periods of stem expansion, with the first period likely representing growth (the production of new wood and bark) and the second representing stem rehydration in the fall and winter. As in the first study, growth was strongly affected by the level of competition around each tree. Our results show the sensitivity of Oregon white oak to competition and highlight the need to restore low stand densities in many cases to improve growth and the likelihood of survival.
Though regeneration of Garry oak (Quercus garryana) seedlings within Garry oak ecosystems is important to maintain this threatened habitat, seedling regeneration is often poor. Two independent studies were initiated in the early 2000s to examine questions surrounding Garry oak recruitment: one at the Crow's Nest Ecological Research Area (CNERA) on Salt Spring Island, BC, and another at the Pacific Rim Institute for Environmental Stewardship (PRI) on Whidbey Island, WA. In both areas, Garry oak seedlings were caged and monitored for growth and relative health. Over 8 years at CNERA, growth of caged plants outpaced growth of controls, which was indicative of high browsing pressure and relatively high palatability of Garry oak seedlings to black-tailed deer and feral sheep. The PRI oaks grew more slowly and at four PRI sites survival was 30–50% over 5–6 years as compared to 90% survival at CNERA over 8 years. The mortality at PRI was likely due to a combination of dry summer conditions and large numbers of voles, which took advantage of the cages for protection from predators; furthermore, lack of mycorrhizal hosts could have inhibited seedling establishment. Weed block inside exclosure cages provided ideal nesting conditions for voles. This study demonstrated that the caging of Garry oak seedlings, although labor-intensive and requiring frequent maintenance, provides valuable protection from large ungulate browsers and can be maintained as a relatively long-term measure, but vigilance is required to protect young seedlings from other threats such as voles or competing vegetation.
Oregon white oak (Quercus garryana) woodlands are the focus of intensive conservation efforts. However, little is known about regeneration in protected oak stands, particularly in small stands surrounded by residential and commercial development. This study investigates the relationship between habitat and landscape structure and patterns of oak seedling and sapling abundance. Specifically, I ask whether patterns of oak seedling and sapling abundance reflect the habitat preferences of animals that disperse acorns and whether seedling and sapling abundance differ in urban versus non-urban landscapes. I conducted vegetation surveys within 30 oak woodlands with natural understory distributed across a gradient of urban development. I used general linear mixed models to determine relationships between oak seedling and sapling abundance and habitat and landscape features. Seedling and sapling patterns showed different relationships to habitat and landscape structure, suggesting that different factors mediate the transition between each stage. I found that seedlings are most abundant under oak and non-oak forest canopy and least abundant under no forest canopy, possibly reflecting dispersal patterns. I found no relationship between seedling abundance and urban development, but young saplings show a negative relationship with urban development. These results suggest that seed dispersers influence seedling spatial patterns, but that this influence is reduced in later life history stages. Although urban development is not related to seedling production, young sapling abundance was significantly lower in urban landscapes. Improved understanding of how habitat and landscape structure influence forest regeneration processes is needed in order to create effective forest restoration and management plans.
The loss and degradation of prairie-oak habitats has resulted in significant changes in bird species breeding distributions and populations. Among the 49 species highly associated with prairie-oak habitats, 21 have experienced extirpations, range contractions, and/or regional population declines. Three species have been regionally extirpated as breeding species since the 1940s, including Lewis's woodpecker, which historically occurred throughout the region. Eleven species have experienced local or ecoregional extirpations and/or range contractions. The predominant pattern of range contraction starts at the northern edge of a species range and moves southward. Nine species have relatively small regional populations, six with limited distribution in the Klamath Mountains ecoregion, and three with small and patchily distributed breeding populations throughout the region. There are nine species with significantly declining regional population trends with a high degree of confidence based on Breeding Bird Survey data, and five with similar declines using Christmas Bird Count data. Several other species may be declining based on a lower degree of confidence in the data or anecdotal observations. These include both endemic subspecies, streaked horned lark and Oregon vesper sparrow, which have regional population estimates of <2,000 and <3,000 birds, respectively. Six species have expanded their range in prairie-oak habitats in the last 50 years. The predominant pattern of range expansion starts at the northern edge of a species range and moves northward. Recommended actions to support prairie-oak bird conservation include range-wide and local inventories and monitoring to determine status, and evaluations and implementation of reintroductions or federal listings as appropriate.
Avian reintroductions are an important conservation tool, but landbird reintroductions are substantially underrepresented compared to other avian taxa, which hinders progress in improving the value and efficacy of landbird reintroductions. We document an ongoing reintroduction of Western bluebirds (Sialis mexicana) to their historic range in the prairie-oak ecosystem on San Juan Island, Washington. Further, we assess the success of preliminary reintroductions and discuss the feasibility of further landbird reintroductions in this threatened ecosystem in the Pacific Northwest. We released 80 adults and 26 juveniles from 2007 to 2010 using a variety of soft-release techniques, and we collected demographic data on the reintroduced population. The program achieved preliminary criteria of success: individuals were safely translocated to the release site, and released individuals established breeding territories; both translocated individuals and their offspring reproduced successfully; and the reintroduced population grew each year. Results reinforced the use of large aviaries and two to three week holding periods for reintroductions of the genus Sialia, and also showed, for the first time, that the reintroduction of a migratory landbird can be effective. Besides contributing to bird conservation, the reintroduction generated tangible accomplishments towards conservation of prairie-oak habitats through education and habitat protection. Reintroductions of Western bluebirds to former parts of their range and of slender-billed white-breasted nuthatch to south Puget Sound should be considered practical options for future avian conservation efforts in the prairie-oak ecosystem.
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 fall burning. All treatment combinations were crossed with native seed addition. As expected, we found there was no ‘silver bullet’; while some treatment combinations led to large improvements in weed control and native diversity and abundance, the optimum combination and degree of success varied across sites. Where non-native grasses are the most pressing problem, we recommend the use of grass-specific herbicides as highly effective with minimal non-target effects on native forbs and some native grasses. Fire is a useful tool for preparing a site for seeding and can be followed closely with a broad spectrum herbicide to control rapidly resprouting weeds. Careful timing of post-fire herbicide application avoids impacting later-sprouting natives. At all sites, we recommend seed addition to enhance native diversity and abundance, as our data show even relatively high quality sites are strongly seed-limited. Repeat mowing is ineffective at reducing herbaceous weed abundance. Additionally, mowing did not increase bare soil, resulting in poor seedling establishment. If fire is not an option, we recommend testing additional treatments to increase bare soil and seeding success. At all sites, we conclude that enhancing natives and controlling invasives are likely to be most successful through repeated applications of treatment combinations.
Competition for soil resources is a driving force in plant community ecology. Therefore, amendments that alter soil resources should affect vegetation dynamics and are potential tools for controlling exotic species. We tested the effects of two types of carbon addition, sugar and activated carbon (AC), on an exotic-dominated grassland plant community. Sugar stimulates the microbial community and temporarily reduces plant available nitrogen (N), while AC adsorbs plant available N. Six experimental plots and three carbon treatments were used: sugar (1000 g m-2; 42% C), AC (420 g m-2; 100% C), and control. Treatments were applied in a split-plot design in spring 2008. Aboveground biomass, plant cover, species richness, and plant basal area were tracked for two growing seasons. Although total biomass was not affected by C addition, the distribution of biomass among life forms was affected: carbon addition reduced forb biomass but had no effect on grasses or legumes. Total cover was lower in sugar-treated plots, and sugar also altered the proportional composition of that cover by reducing the abundance of forbs, especially in the first year. Five species were particularly sensitive to sugar addition: Myosotis discolor, Sonchus asper, Taraxacum officinale, Valerianella locusta, and Vulpia bromoides. Sugar also reduced plant basal area in the first year. These results suggest that sugar and, to a lesser extent, AC could be useful management tools. Sugar could be applied to areas where herbicide use is undesirable, reducing the abundance of exotic forbs and providing a window of opportunity for native species establishment.
Nitrogen enrichment has often been demonstrated to enhance the success of introduced plant species at the expense of native species. In the south Puget lowland prairies of Washington State, invasion by Scotch broom (Cytisus scoparius), a nitrogenfixing legume, is associated with elevated soil nitrogen levels. After broom removal, the higher soil nitrogen levels may have facilitated the secondary invasion of the prairies by numerous non-native species, particularly rhizomatous pasture grasses that can interfere with native plant seedling establishment. Numerous studies have shown the potential for carbon addition to immobilize soil nitrogen and reduce the success of introduced species relative to native species. We compared the available soil nitrate, the cover of native and introduced species between sugar-addition (1000 g C m-2) and control plots on two Puget lowland prairies. Sugar treatment initially immobilized nitrate and reduced cover of introduced species compared to that on control plots, but these effects dissipated within two years. Moreover, after four years, cover of introduced species, especially that of Agrostis capillaris and Hypochaeris radicata, had rebounded to become higher in sugar-addition than in control plots. In contrast, native species showed no negative responses to sugar treatment, suggesting that where sugar or other carbon treatment is economically feasible, combining carbon with the establishment of a high density of native species might limit the potential for introduced species to rebound.
Restoring highly degraded sites in Oregon's Willamette Valley to diverse native prairie plant communities is an important component of regional conservation strategies. However, creating or reassembling desired native plant communities is a tremendous challenge for restoration practitioners, and useful practical approaches are needed. Here, we describe an implementation strategy we developed for restoring intensively managed agricultural sites to native wet prairie that integrates relevant scientific research and lessons learned from previous restoration experience, with a particular focus on sequencing disturbance, colonization, and competitive actions to achieve desired outcomes. Then, we report vegetation monitoring results from four projects where we used this implementation strategy to assess if progress is being made to achieve our two a priori project objectives: (1) establishing a plant community with 50 or more native plant species, and (2) establishing a plant community with > 70% absolute cover of native plant species. By the second growing season after seeding, all four projects had more than 40 native species and native cover exceeded 90%. For the two projects for which we have data during the fifth growing season, native species richness exceeded 50 and absolute native cover exceeded 100%. Furthermore, percent cover of native annuals decreased and percent cover of native perennials increased by the fifth growing season, consistent with predictions from succession. These results indicate that our implementation strategy can assist the efforts of landowners and managers to restore high diversity prairie communities from highly disturbed agricultural sites.
We evaluate prairie plant community variation in a matrix of restoration treatments in the south Puget Lowland, WA. Native and exotic plant community diversity and composition were measured across areas that differed in burning history and grass-specific herbicide application, having received one to several treatments since 2002. All plots were also variable in historical proximity to a key invasive exotic species (Cytisus scoparius - Scotch broom), a nitrogen-fixing shrub. Three trends were readily apparent from our data: 1) total plant species richness was higher following a prescribed fire. This trend was associated with increases in both native and exotic plants; 2) areas treated with a grass-specific herbicide generally had lower exotic and higher native cover; and 3) using a combination of GIS modeling and community analysis, we found that historical proximity to C. scoparius across all treatment areas was associated with suppressed native species richness. In fact, the magnitude of the effect of historical proximity to C. scoparius was as large as the differences among fire treatment areas. These data suggest that restoration treatments such as fire and herbicide application affect species richness and diversity in prairies, but the changes were neither rapid nor large. Further, exotic species legacies may interact with treatment effects to variably alter restoration outcomes.
Wet prairies dominated by the perennial bunchgrass Deschampsia cespitosa occurred extensively in the Willamette Valley at the time of Euro-American settlement. Historical evidence and recent habitat changes suggest that late summer fires set by Native Americans suppressed woody vegetation and promoted vegetative growth, seed production and seedling recruitment of herbaceous species. Using prescribed fire for prairie management is challenging; dry season mowing is often the preferred alternative in wet prairies. We initiated a seven year experiment to compare the effects of late summer/fall mowing and burning on native and non-native vascular plants in a remnant Willamette Valley wet prairie. We analyzed change in percent frequency from pre-treatment to the first two post-treatment years (and over all years) with ANOVA for a randomized complete block design. Twenty-five of 61 species or life stages showed treatment effects from burning or mowing. Ordination and MRBP tests indicated small treatment effects on overall species composition. With burning, the response of 15 species was desirable relative to management objectives (the increase of a native herbaceous or decrease of non-native or woody species) and eight showed undesirable effects. With mowing, eight and seven species exhibited desirable and undesirable treatment outcomes, respectively. While both fire and mowing appear to provide short term benefits to native wet prairie plants, more species benefitted from burning than mowing. While prescribed fire may be a preferred management tool where and when it can be implemented, the optimal management treatment will depend upon the suite of introduced species at a given site.
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 changes in habitat structure and function have contributed to the decline of several plant and animal species. Over the past decade, prescribed fire has been increasingly applied throughout the Willamette Valley-Puget Trough-Georgia Basin Ecoregion and used in conjunction with other techniques (herbicide, seeding native species) to restore native habitat with variable results. This variability likely is a result of differential fire intensity, dictated by fuels, weather and application technique, all of which can be controlled for by altering fire season, fire frequency, pre-fire treatments and fire extent. In order to burn at the spatial and temporal scales necessary for effective habitat restoration, however, prescribed burn programs must overcome several socio-political, programmatic and economic challenges. This requires a collaborative approach to prescribed fire training, implementation and research. Future research on fire season, fire frequency, species-specific responses to fire and effects of fire surrogates on ecosystem structure and functioning will help to refine prescribed fire management for maximum effectiveness in prairie and oak woodland restoration.
Invasion by non-native plant species is one of the greatest threats to prairie, savanna, and oak woodland habitats of the Willamette Valley-Puget Trough-Georgia Basin (WPG) ecoregion. Invasive plants can modify the diversity, structure, and function of natural habitats. Effects from non-native invasions have contributed to the decline of many native species found on Pacific Northwest prairie and oak habitats. Even with aggressive management, these unique habitats are severely impacted by nonnative plant invasions. Without management, native species diversity will continue to decline rapidly. Here we provide a list of invasive plants that have extensive detrimental impacts on prairies, savannas, and oak woodlands throughout the ecoregion as a resource for land managers. We provide technical descriptions for the most highly invasive shrubs, grasses, and forbs, current best management practices, and an outlook for the future. When available, we document results from experimental trials. Much of the information presented is based on field observations from experienced land managers. Invasive plants will continue to be a management priority in the WPG for the foreseeable future. Working cooperatively from an ecoregional perspective to track occurrence, develop and implement effective management, and monitor progress is the best platform for successful restoration of the prairies, savannas, and oak woodlands in the WPG ecoregion.
South Puget Sound prairies are fragmented and degraded, which has a profound effect on plant populations, especially those that are already species of concern, such as Puget balsamroot (Balsamorhiza deltoidea Nutt). Small Puget balsamroot populations may be caused by inadequate pollination via insufficient pollinator services or by low quality pollen. Comparing potential germinants of hand- and naturally-pollinated inflorescences, which takes into account seed set and germination rates, illustrates the extent of pollination limitation on three South Puget Sound prairies on Joint Base Lewis-McChord (7S, Upper Weir, and Johnson). Our results demonstrated that Puget balsamroot is self-incompatible. On all three prairies, hand-pollinated inflorescences produced more potential germinants than naturally-pollinated inflorescences (P < 0.001), indicating that Puget balsamroot is pollen limited. In addition, 7S had a significantly greater number of floral and soil resources than either Johnson or Upper Weir (P < 0.05). However, there were not proportionally more bees found on 7S as compared to Johnson or Upper Weir. Therefore, Puget balsamroot on 7S may be pollen limited because pollinator populations are too small. Determining pollinator population sizes on the south Puget Sound lowland prairies could prove to be useful in determining the relative effects of pollinator limitation and low pollen quality. We suggest that fragmented ecosystems are more susceptible to pollinator limitations than congruent systems because ranges of pollinators no longer adequately overlap to facilitate travel between the ecosystem fragments.
Prairie-oak butterfly species in the Willamette Valley-Puget Trough-Georgia Basin (WPG) ecosystem have declined dramatically due to widespread habitat degradation and loss of prairie-oak ecosystems in the region. Conservation of prairie-oak butterflies offers unique opportunities and special challenges. Here we provide an overview of butterfly conservation in WPG prairies. We begin with a review of the status of at-risk butterfly species in the region, an introduction to five species that are the focus of current conservation efforts: Fender's blue (Icaricia icarioides fenderi), Taylor's checkerspot (Euphydryas editha taylori), mardon skipper (Polites mardon), island marble (Euchloe ausonides insulanus), and Oregon silverspot (Speyeria zerene hippolyta), and a brief review of 10 additional at-risk butterfly species in the ecoregion. We follow with a discussion of three key threats (habitat loss and fragmentation, invasive species, and lack of appropriate disturbance) and four dominant management approaches (fire, herbicides, mowing, and habitat restoration). We discuss current challenges and emerging issues for these species, and focus on invasive species management, understanding basic biology, conserving multiple species, and adapting to climate change. We highlight several success stories from around the region. We conclude that butterfly biologists and land managers in the WPG are in a unique position to conserve the region's threatened prairie butterflies. Facilitating greater communication across the region through organizations such the Cascadia Prairie-Oak Partnership will assist in recovery of the WPG's threatened, endangered and at-risk butterfly species.
Seeds from 30 species of grasses and forbs native to Pacific Northwest prairies were tested for physical and physiological dormancy. The physical dormancy was determined by mechanically and chemically scarifying seeds. Physiological dormancy was evaluated with cold stratification before germination. Experiments were analyzed individually with ANOVA analysis, and by seed lots through time using multiple regression. Three of the tested species had too little germination to determine what kind of dormancy was present. Physical dormancy was found in three legumes that required a treatment to break the hard seed coat. These species, Lotus unifoliolatus, Lupinas albicaulis, and Trifolium willdenovii also had increased germination following cold stratification. This can be taken as evidence of physiological dormancy. Physiological and physical dormancy together is considered combinational dormancy. Another eight species had increased germination after cold stratification. This included both species that did not germinate without cold stratification (Aquilegia formosa, Camassia leichtlinii, C. quamash, Heracleum maximum, Lomatium nudicaule, Perideridia oregona, and Sidalcea campestris), and species with germination proportions that increased following stratification (Eriophyllum lanatum, and the legumes). Four annual forbs (Clarkia purpurea, Collomia grandiflora, Gilia capitata, and Madia gracilis) had increased germination when seeds were cold stratified, but the response was more consistent with a low temperature requirement for germination than physiological dormancy. The remaining 12 species germinated with no pretreatments. Understanding the germination requirements of these species will aid in their propagation for restoration and the provisioning of ecosystem services and may help explain the ecology of these species on the landscape.
Understanding germination requirements of native species is an important component of restoration in south Puget Lowland prairies (Washington, USA). We conducted an experiment to determine the effects of pre-germination treatment and germination temperature conditions on the proportional germination of three species of Lupinas. For one species, Lupinus lepidus, germination was highest following heat shock treatments to the dormant seed, suggesting adaptation to the high temperatures associated with wildfire. For a more widespread species, Lupinus polyphyllus, high heat treatments had no effect, and germination was mildly higher in a temperature sequence simulating winter chilling followed by cool, diurnally alternating temperatures. For a final intermediate species, Lupinus albicaulis, responses to germination temperatures were dependent on high-heat treatments. These data suggest interspecific variation in germination cues where these Lupinus species are influenced differentially by environmental conditions in both breaking of physical dormancy and the promotion of germination. Our results have the potential to improve the establishment of these species from seed in restoration. Specifically, there may be implications for the timing of manual seed sowing and the efficacy of seed establishment following exposure to fire in south Puget Lowland prairies.
This paper represents a collaboration by conservation practitioners, ecologists, and climate change scientists to provide specific guidance on local and regional adaptation strategies to climate change for conservation planning and restoration activities. Our geographic focus is the Willamette Valley-Puget Trough-Georgia Basin (WPG) ecoregion, comprised of valley lowlands formerly dominated by now-threatened prairies and oak savannas. We review climate model strengths and limitations, and summarize climate change projections and potential impacts on WPG prairies and oak savannas. We identify a set of six climate-smart strategies that do not require abandoning past management approaches but rather reorienting them towards a dynamic and uncertain future. These strategies focus on linking local and regional landscape characteristics to the emerging needs of species, including potentially novel species assemblages, so that prairies and savannas are maintained in locations and conditions that remain well-suited to their persistence. At the regional scale, planning should use the full range of biological and environmental variability. At the local scale, habitat heterogeneity can be used to support species persistence by identifying key refugia. Climate change may marginalize sites currently used for agriculture and forestry, which may become good candidates for restoration. Native grasslands may increasingly provide ecosystem services that may support broader societal needs exacerbated by climate change. Judicious monitoring can help identify biological thresholds and restoration opportunities. To prepare for both future challenges and opportunities brought about by climate change, land managers must incorporate climate change projections and uncertainties into their long-term planning.