A few tree ring studies indicate recent growth declines at northern latitudes. The precise causes are not well understood. Here we identify a temperature threshold for decline in a tree ring record from a well‐established temperature‐sensitive site at elevational tree line in northwestern Canada. The positive ring width/temperature relationship has weakened such that a pre‐1965 linear model systematically overpredicts tree ring widths from 1965 to 1999. A nonlinear model shows an inverted U‐shaped relationship between this chronology and summer temperatures, with an optimal July–August average temperature of 11.3°C based on a nearby station. This optimal value has been consistently exceeded since the 1960s, and the concurrent decline demonstrates that even at tree line, trees can be negatively affected when temperatures warm beyond a physiological threshold. If warming continues without significant gains in effective precipitation, the large‐scale greening of recent decades could be replaced by large‐scale browning. Such browning could slow or reverse carbon uptake by northern forests.

The functioning of Arctic ecosystems is not only critically affected by climate change, but it also has the potential for major positive feedback on climate. There is, however, relatively little information on the role, patterns, and vulnerabilities of CO 2 fluxes during the nonsummer seasons in Arctic ecosystems. Presented here is a year-round study of CO 2 fluxes in an Alaskan Arctic tussock tundra ecosystem, and key environmental controls on these fluxes. Important controls on fluxes vary by season. This paper also presents a new empirical quantification of seasons in the Arctic based on net radiation. The fluxes were computed using standard FluxNet methodology and corrected using standard Webb-Pearman-Leuning density terms adjusted for influences of open-path instrument surface heating. The results showed that the nonsummer season comprises a significant source of carbon to the atmosphere. The summer period was a net sink of 24.3 g C m À2 , while the nonsummer seasons released 37.9 g C m À2 . This release is 1.6 times the summer uptake, resulting in a net annual source of +13.6 g C m À2 to the atmosphere. These findings support early observations of a change in this particular region of the Arctic from a long-term annual sink of CO 2 to an annual source from the terrestrial ecosystem and soils to the atmosphere. The results presented here demonstrate that nearly continuous observations may be required in order to accurately calculate the annual net ecosystem CO 2 exchange of Arctic ecosystems and to build predictive understanding that can be used to estimate, with confidence, Arctic fluxes under future conditions.

[1] We investigate the physiological effects of the elongation of the growing season and the increase in summer greenness on northern hemisphere forests by examining the relationship between NDVI and tree rings. These variables are correlated during June and July only. These results suggest that NDVI proxies the physiological status of trees and that the summer status of the canopy has a larger effect on tree vigor than the duration of the canopy.

This paper explores the theoretical roots of the wounded healer archetype and the shadow side of the wounded healer. Our emphasis is on reflectivity as a means of expanding self-understanding and clinical consultation as a way of enhancing reflectivity. A case vignette presented in this article is taken from the clinical practice of one of the authors (KP), who, literally and figuratively, lives the role of wounded healer.

This article applies theoretical perspectives of client stalking behavior to vignettes of clinical nurse specialists (CNSs) who have experienced stalking incidents. A description of stalking behavior, estimations of the frequency of stalking behavior, characteristics of stalkers, and the impact of stalking on victims are addressed. Health care professionals, including CNSs, may inadvertently become victims of stalking behavior. Firm and clear boundary setting is important in all CNS-client relationships. CNSs who believe that they are becoming the objects of attention for particular individuals are advised to convey a clear message that they have no interest in the development of such a relationship. In this article CNS responses to actual client stalking behavior, including confrontation by the CNS, police involvement, restraining orders, and use of the CNS's attorney, are explored. The use of clinical consultation and the need for agencies to develop safety plans for all employees are also addressed.