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Mean elevation values of "all yellow-cedar" stands (white) and "leading yellowcedar" stands (grey) (normalized by area). (Statistically significant difference between samples, p-value = <0.001)
Source publication
Yellow-cedar (Chamaecyparis nootkatensis D. Don (Spach)) is currently undergoing a dramatic decline in western North America. Recent research suggests that site factors combined with a shift in climate have predisposed yellow-cedar trees to decline. We conducted the first landscape-level analysis of the decline in coastal British Columbia to assess...
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Citations
... Already confirmed climate change effects in this region include elevated temperatures (Karl et al., 2009), declining mountain snowpack (Mote et al., 2005), shifts in species distributions (Wang et al., 2012), and reduced fog levels ( Johnstone and Dawson, 2010). Diminished snowpack combined with late winter freezes has triggered dieback of Alaska yellow-cedar (Cupressus nootkatensis) in southeast Alaska (Hennon et al., 2012) and northern British Columbia (Wooten and Klinkenberg, 2011). ...
Climate change poses significant threats to Pacific coastal rainforests of North America. Land managers currently lack a coordinated climate change adaptation approach with which to prepare the region's globally outstanding biodiversity for accelerating change. We provided analyses intended to inform coordinated adaptation for eight focal rainforest tree species of commercial importance and broad rainforest communities. By using two different approaches to determine vulnerability, including climate envelope modeling (Maxent) and the MC1 dynamic vegetation model, we were able to assess where Pacific coastal rainforests might be more stable over time. We examined vegetation stability based on climate projections and used protected areas and intact late-seral forest data to determine priority areas and current level of protections. Based on model outputs, focal rainforest conifers and general rainforest communities are more likely to persist and to expand their ranges along northern range margins while southern margins exhibited lower persistence and potential loss of suitable climate. Robust reserve design for temperate rainforests should include current and future late-seral forests as potential climate refugia to accommodate projected shifts in species of commercial and ecological importance.
... At the broad scale, yellow-cedar decline has elevational limits that vary by latitude (Lamb and Winton 2011) in a manner consistent with climate controls. Decline at southern latitudes in British Columbia occurs considerably higher in elevation (i.e., 200-700 m; Hennon et al. 2005, Westfall and Ebata 2009, Wooton and Klinkenberg 2011. Along northern latitudes, decline is found at lower elevations, until finally, at the northern extent, 57.6 degrees north (°N) in Alaska, tree death is expressed in a narrow, low-elevation band from sea level to only 150 m. ...
The extensive mortality of yellow-cedar along more than 1000 kilometers of the northern Pacific coast of North America serves as a leading example of climate effects on a forest tree species. In this article, we document our approaches to resolving the causes of tree death, which we explain as a cascade of interacting topographic, forest-structure, and microclimate factors that act on a unique vulnerability of yellow-cedar to fine-root freezing. The complex causes of tree mortality are reduced to two risk factors—snow depth and soil drainage—which are then used to model present and future cedar habitat suitability. We propose a dynamic, comprehensive conservation strategy for this valuable species on the basis of zones created by shifting climate, cedar's ecological niche, and observed risk factors. Research on yellow-cedar decline is offered as a template for understanding and adapting to climate change for other climate–forest issues.
In Southeast Alaska, many stands of yellow-cedar (Callitropsis nootkatensis D. Don; Oerst. ex D.P. Little; hereafter: ‘YC’) contain numerous standing, dead snags. Snag-age estimates based on morphology have been used to support the interpretation that a warming climate after ca. 1880 triggered unprecedented YC dieback. Here we present new estimates of YC snag longevity by cross-dating 61 snags with morphologies that suggest they stood dead for extended periods. All but four of these snags have lost their outermost rings to decay, so we estimate when they died using a new method based on wood-ablation rates measured in six living trees that display partial cambial dieback. Results indicate that ~59% of YC snags that lost their branches to decay (Class 5 snags) have remained standing for > 200 years, and some for as long as 450 years (snag longevity mean ± SD: 233 ± 92 years). These findings, along with supporting evidence from historical photos, dendrochronology, and snag-morphology surveys in the published literature suggest that episodes of YC dieback also occurred before 1880 and before significant anthropogenic warming began. The roles played by climate change in these earlier dieback events remain to be further explored.
Yellow-cedar (Callitropsis nootkatensis (D.Don) D.P. Little), a conifer in the Cupressaceae with indeterminate growth, is undergoing severe decline and mortality in southeast Alaska and the coast of northern and central British Columbia. This decline is attributed to cold damage to roots associated with climate warming and reduced snowpack. The cold tolerance of indeterminate conifer species is little studied, and less is known about root cold tolerance, as most studies focus on shoots. We compared the seasonal cycle of cold hardiness in roots and shoots of yellow-cedar seedlings from high and low elevation populations over one year. Freezing tolerance of shoots followed a typical seasonal cycle with low levels of cold tolerance observed from April to October and moderate levels of cold tolerance observed in mid-winter. Differences in shoot cold tolerance among populations were consistent with the latitude and elevation of origin. In contrast, at the same freezing temperatures, roots of all seedlings had consistent, high levels of cold damage throughout the year.
The effects of climate change on insect outbreaks, wildfire, invasive species, and pathogens in forest ecosystems will greatly exceed the effects of warmer temperature on gradual changes in forest processes. Increased frequency and extent of these disturbances will lead to rapid changes in vegetation age and structure, plant species composition, productivity, carbon storage, and water yield. Insect outbreaks are the most pervasive forest disturbance in the United States, and rapid spread of bark beetles in the western United States has been attributed to a recent increase in temperature. Wildfire area burned has increased in recent decades, although frequency and severity have not changed, and is expected to greatly increase by 2050 (at least twice as much area burned annually in the West). More frequent occurrence of fire and insects will create landscapes in which regeneration of vegetation will occur in a warmer environment, possibly with new species assemblages, younger age classes, and altered forest structure. Increased fire and insects may in turn cause more erosion and landslides. Invasive plant species are already a component of all forest ecosystems, and a warmer climate will likely facilitate the spread of current and new invasives, particularly annuals that compete effectively in an environment with higher temperature and frequent disturbance. The interaction of multiple disturbances and stressors, or stress complexes, has the potential to alter the structure and function of forest ecosystems, especially when considered in the context of human land-use change. Occurring across large landscapes over time, these stress complexes will have mostly negative effects on ecosystem services, requiring costly responses to mitigate them and active management of forest ecosystems to enhance resilience.
