LEFT: Tucked up on the mountainside, this 11-tiered pagoda represents monasteries in the mountains of Japan. RIGHT: Maple leaves cover the roof of the machiai house in the tea garden. AURORA SANTIAGO is a nature and garden photographer whose work is strongly featured on the Seattle Japanese Garden website and blog. She won the People’s Choice Award during the 2017 “Autumn Reflections” juried photo exhibit at the Japanese Garden. She is also a retired RN. PROJECTED ENVIRONMENTAL CHANGES IN THE PNW • Rise of between 2.7°F and 10.4°F in • However, warmer winters may fail to mean air temperature this century, with satisfy “chilling requirement” of some greatest warming occurring in summer. species (e.g. Douglas-fir)—leading to • Reduction in summer precipitation of delayed budburst and shoot growth. up to 14% by end of century. • Also, early budburst may expose plants • Increase in mean winter precipitation to potential frost damage. of up to 8% by end of century. • Early flowering may promote seed • Summer soil-water availability likely to production but also lower reproductive decline in much of region. capacity by altering synchrony between plants and their pollinators/dispersers. • This will lead to increased drought stress and reduced photosynthesis. • Elevated carbon dioxide in the air may enhance productivity and water-use • Less precipitation will fall as snow, efficiency in plants, offsetting somewhat leading to reduced snowpack accumu- the negative effects of warming. lation and duration, and subsequent impacts on dependent ecosystems. • Warming climate will likely increase disturbances from wildfires, new pests • Warming winter temperature may and diseases, and invasive species. lengthen growing season, promoting growth (given sufficient water). • This may cause forests to convert from carbon sinks to carbon sources. 14 v Washington Park Arboretum Bulletin OUR CHANGING CLIMATE, PART 3 Implications for Native Plant Communities and Conservation in the Pacific Northwest Alpine meadow on Mount Rainier. B Y N I A LL D UNNE (Photo by Samuel Kerr/Wikimedia Commons) Part 1 of this article (“Bulletin,” Fall 2015) discussed simple practices that gardeners can adopt in order to shrink their carbon footprint and help reduce the severity of climate change in our region. Part 2 (“Bulletin,” Fall 2016) offered tips on how to adapt the garden to the coming conditions, which include hotter, drier summers; warmer, wetter winters; and new pest and disease problems (see “Projected Environmental Changes in the PNW,” page 14). Part 3 explores the predicted effects of climate change on native plant communities in our region and the steps that land managers are taking to prepare. ASSESSING VULNERABILITY few years ago, I went on a day trip to chinquapin and Rocky Mountain juniper) may the Olympic Peninsula on behalf of become more competitive in areas presently the UW Botanic Gardens’ Rare Care dominated by less drought-tolerant tree species.” Program.A The assignment was to find and The report assesses the vulnerability of survey a small population of golden chinquapin regionally native tree species to climate change (Chrysolepis chrysophylla), a native tree in the based on a number of factors, including their beech family with leathery, evergreen leaves and current distribution, adaptive genetic varia- spiny, chestnut-like fruits. The tree is rela- tion, reproductive capacity, and threats from tively common in the coastal forests of Oregon insects and disease. In the Western Washington and California, but only occurs in several small, region, iconic forest species such as Douglas- scattered populations in Washington—the fir, western red cedar, bigleaf maple and western northernmost point of its current range. hemlock all scored relatively low—meaning that It took some scrambling across a steep, they are at least risk from climate change effects. forested ridge, but eventually my field partner The highest vulnerability scores went to Pacific and I found the trees—about eight of them. silver fir, subalpine fir, Engelmann spruce, noble They were somewhat isolated from each other fir and grand fir, which all happen to be cold- in a sea of western hemlock and Douglas-fir— adapted, high-elevation tree species. (The report and they didn’t look particularly healthy. (The recommended that these species become a special species is relatively intolerant of shade.) It was focus for conservation and monitoring efforts.) hard to imagine how this tiny population could This tracks with general predictions about the persist over time. However, it’s possible we may influence of climate change on forests—namely be hearing more from the species in the future. that forest communities are expected to lose According to a 2012 USDA Forest Service report cold-adapted trees near their low-elevation and entitled “Climate Change and Forest Trees in the low-latitude range limits, while warm-adapted Pacific Northwest,” “tree species that are highly trees are expected to increase in abundance near drought-tolerant (e.g. Pacific madrone, golden their high-elevation and high-latitude limits. Fall 2018 v 15 SPECIAL CONCERN FOR ALPINES terrain on the snowy edge of the high alpine zone. The concern for cold-adapted trees is echoed “As temperatures warm and precipitation at high in a more recent Forest Service publication, elevations shifts from snow to rain, these climate “Climate Change Effects on Vegetation in the conditions will cease to exist. The endemics have Pacific Northwest” (2014), which reviews and essentially topped out; they are already occupy- synthesizes the current scientific literature and ing the highest and coldest available terrain, and ecosystem modelling projections on the topic. there is no colder climate space available for their The authors found that of the five major biomes distributions to shift into as climate warms.” in the Pacific Northwest (subalpine forests and For a plan of action, the researchers recom- alpine meadows; maritime, coniferous forests; mend that potential refuge sites (some of which dry coniferous forests; juniper savannas and are mapped in their paper) be protected from woodlands; interior shrub-steppe), subalpine non-climate related impacts, such as hiking by forest and alpine meadows are at most risk. All humans and foraging by non-native mountain the simulation models reviewed agreed that goats. (Good news on the latter score: Olympic suitable climate available for most key subalpine National Park officials began airlifting mountain species will be moderately reduced to nonexis- goats back to their native range in the North tent by the end of this century. Suitable habitat Cascades this summer.) may only be available at high elevations in the far So-called “interventionist” approaches, northern Cascade Mountains. such as assisted migration (moving the plants While many members of these high-elevation to more favorable habitat), may also be helpful. communities will likely be able to persist farther However, Wershow and DeChaine say that these north of our region (either because they grow there approaches are controversial due to their poten- already, or they may be able to migrate), some tial unintended effects on other native species endemic alpine species—that is native alpines and are unlikely to be used in the Park because it restricted to our region—may be in big trouble. is managed as wilderness. At the UW Botanic Gardens’ 2018 OBSERVATIONAL STUDIES Washington Botanical Symposium in March, Though the different ecosystem models seem to Eric DeChaine, professor of biology at Western be in relative agreement about the vulnerability Washington University, presented his lab’s of alpine and subalpine communities, there’s a research on five perennial herbs endemic lot of uncertainty about the other major biomes to the Olympic Mountains: piper’s harebell in our region. This stems from a lack of certitude (Campanula piperi), Flett’s violet (Viola flettii), about exactly what future growing conditions Olympic Mountain groundsel (Senecio will look like (particularly precipitation levels), neowebsteri), Olympic Mountain synthyris and also how plants will respond to the changes. (Synthyris pinnatifida var. lanuginosa), and Flett’s For instance, some model results predict little or no fleabane (Erigeron flettii). DeChaine and his change for maritime coniferous forests, while others graduate student Samuel Wershow have esti- predict reductions for this forest type—particularly mated that 85 to 99 percent of suitable habitat in the southern part of the Pacific Northwest. will be lost for each of the species by 2080—and Models use simplified versions of natural that small refugia (areas in which populations systems and are best utilized as signposts rather may persist as warming diminishes their habitats than definitive forecasts. Other data, such as elsewhere) may only remain on the highest peaks results from observational and experimental of the eastern Olympics. studies, should be factored in, too. One 2010 In a related paper published this spring in study of forest herb communities in the Siskiyou the “American Journal of Botany,” Wershow and Mountains of southern Oregon was consis- DeChaine write that all five species are habitat tent with warming predictions: It found that, specialists occupying a narrow range of environ- over a 60-year period (1949 to 2009), in which mental conditions—generally the cold, rocky mean temperatures increased 3.5 °F, there were 16 v Washington Park Arboretum Bulletin multiple changes in lower