Did climatic warming trigger the onset and development of yellow‐cedar decline in southeast Alaska*

Hennon, Paul E.; Shaw, Charles G.

doi:10.1111/j.1439-0329.1994.tb00833.x

Cited by 36 publications

(51 citation statements)

References 15 publications

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“…ex D.P. Little), a species distributed from the northern Klamath Mountains of California to Prince William Sound in Alaska, has been dying in southeast Alaska since the late 1800s with intensifying rates observed in the 1970s and 1980s (Hennon and Shaw 1994). Recent research reveals a complex ''tree injury pathway'' where climate change plays a key role in a web of interactions leading to widespread yellow-cedar mortality, referred to as yellow-cedar decline (Hennon et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Long‐term vegetation changes in a temperate forest impacted by climate change

et al. 2014

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Abstract. Pervasive forest mortality is expected to increase in future decades as a result of increasing temperatures. Climate-induced forest dieback can have consequences on ecosystem services, potentially mediated by changes in forest structure and understory community composition that emerge in response to tree death. Although many dieback events around the world have been documented in recent years, yellowcedar (Callitropsis nootkatensis) decline provides an opportunity to study vegetation changes occurring over the past century. Current research identifies climate-related reductions in snow cover as a key driver of this species dieback. To examine the process of forest development post-dieback, we conducted vegetation surveys at 50 plots along the outer coast of southeast Alaska across a chronosequence of mortality. Our main study objectives were to examine changes in seedling and sapling abundance, and community structure of conifer species in the overstory; effects of yellow-cedar mortality on plant diversity and community composition of functional groups in the understory; and volume of key forage species for Sitka black-tailed deer (Odocoileus hemionus sitkensis) managed throughout the region. The probability of yellow-cedar sapling occurrence was reduced across the chronosequence. Yellow-cedar seedling and sapling abundance also decreased. We observed a turnover from yellow-cedar to western hemlock (Tsuga heterophylla) dominated forests. Functional plant diversity increased and the community composition of the understory changed across the chronosequence. Bryophytes became less abundant and grasses more abundant in the early stages of stand development, and shrubs increased in relative abundance in latter stages. Our results demonstrate that yellow-cedar is significantly less likely to regenerate in forests affected by widespread mortality, and a species dieback can dynamically rearrange the plant community over time. These findings emphasize the importance of considering long-term temporal dynamics when assessing the impacts of climate change on biodiversity and ecosystem services, and adapting forest management to a changing climate.

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Section: Introductionmentioning

confidence: 99%

Long‐term vegetation changes in a temperate forest impacted by climate change

et al. 2014

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“…Around 1880, yellow cedar growing near open bogs, or on semibog sites with poor drainage, began to die, initiating a forest decline that continues to this day (Hennon et al, 1990a). Circumstantial evidence suggests that this decline was triggered by climatic warming (Hennon and Shaw, 1994), with minimal involvement of biotic agents (Hennon, 1990;Hennon et al, 1990b,c,d). Interactions of site characteristics with maritime-continental climate patterns are associated with tree mortality (Hennon and Shaw, 1997) that has left standing dead trees (snags) on more than 200,000 ha widely spread across the landscape.…”

Section: Introductionmentioning

confidence: 99%

Changes in Heartwood Chemistry of Dead Yellow-Cedar Trees that Remain Standing for 80 Years or More in Southeast Alaska

et al. 2005

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Abstract-We measured the concentrations of extractable bioactive compounds in heartwood of live yellow-cedar (Chamaecyparis noothtensis) trees and five classes of standing snags (1-5, averaging 4, 14,26,5 1, and 81 yearssince-death, respectively) to determine how the concentrations changed in the slowly deteriorating snags. Three individuals from each of these six condition classes were sampled at four sites spanning a 260-km distance across southeast Alaska, and the influence of geographic location on heartwood chemistry was evaluated. Cores of heartwood were collected at breast height and cut into consecutive 5-cm segments starting at the pith. Each segment was extracted with ethyl acetate and analyzed by gas chromatography. Concentrations of carvacrol, nootkatene, nootkatol, nootkatone, nootkatin, and total extractives (a sum of 16 compounds) for the inner (0-5 cm from pith), middle (5-10 cm from pith), and surface (outer 1.1-6.0 cm of heartwood) segments from each core were compared within each tree condition class and within segments across condition classes. Heartwood of class 1 and 2 snags had the same chemical composition as live trees. The first concentration changes begin to appear in class 3 snags, which coincides with greater heartwood exposure to the external environment as decaying sapwood sloughs away, after losing the protective outer bark. Within core segments, the concen-* To whom correspondence should be addressed. E-mail: rke1seyGJfs.fed.u~ trations of all compounds, except nootkatene, decrease between snag classes 2 and 5, resulting in the Ileartwood of class 5 snags having the Iowest quantities of bioactive compounds, although not different t%om the amounts in class 4 snags. This decline in chemical defense is consistent with heartwood of class 5 snags being less decay-resistant than heartwood of live trees, as observed by others. The unique heartwood chemistry of yellow cedar and the slow way it is altered after death allow dead trees to remain standing for up to a century with a profound impact on the ecology of forests in southeast Alaska where these trees are in decline.

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“…• Concentrations of yellow-cedar mortality were first observed in the late 1800s to early 1900s (Sheldon 1912), with the greatest pulses of death in the 1970s and 1980s (Hennon and Shaw 1994). These mortality events correspond to the end of the Little Ice Age and warmer periods of the Pacific Decadal Oscillation, followed by a relative lull in decline in the 1990s and 2000s (Hennon et al 2016).…”

Section: Understanding Of Decline Dynamicsmentioning

confidence: 99%

Alternative interpretation and scale-based context for “No evidence of recent (1995–2013) decrease of yellow-cedar in Alaska” (Barrett and Pattison 2017)

et al. 2017

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Abstract:In their analysis of resampled and remeasured plot data from the USDA Forest Service Forest Inventory and Analysis (FIA) program, Barrett and Pattison (2017, Can. J. For. Res. 47(1): 97-105, doi:10.1139/cjfr-2016-0335) suggest that there is neither evidence of a recent regional decrease in yellow-cedar (Callitropsis nootkatensis (D. Don) Oerst. ex D.P. Little) live tree basal area nor a decrease in the species' extent in southeastern Alaska. Here, we identify substantial, broad-scale agreement between their estimated extent of concentrated yellow-cedar mortality and that resulting from a complementary, existing body of research into yellow-cedar decline spanning 35 years. However, we also discuss concerns that the FIA remeasurement data used did not match the spatial distribution of the decline (e.g., excluding areas of known active decline in wilderness areas) and that the temporal coverage of FIA data (1990s to 2000s) was inappropriately compared with a cumulative decline map that spans several decades, meshing recent mortality with mortality that occurred up to a century ago. We provide an alternative explanation of Barrett and Pattison's results in the context of ongoing yellow-cedar distribution and decline research in southeastern Alaska and support our interpretation by focusing on the temporal and spatial aspects of decline.Key words: yellow-cedar decline, climate change, forest inventory, biomass monitoring, survey metholodology. Mots-clés : faux-cyprès de Nootka, dépérissement, changement climatique, inventaire forestier, suivi de la biomasse, méthode d'inventaire.

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Did climatic warming trigger the onset and development of yellow‐cedar decline in southeast Alaska*

Cited by 36 publications

References 15 publications

Long‐term vegetation changes in a temperate forest impacted by climate change

Long‐term vegetation changes in a temperate forest impacted by climate change

Changes in Heartwood Chemistry of Dead Yellow-Cedar Trees that Remain Standing for 80 Years or More in Southeast Alaska

Alternative interpretation and scale-based context for “No evidence of recent (1995–2013) decrease of yellow-cedar in Alaska” (Barrett and Pattison 2017)

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