Future drought is projected to occur under warmer temperature conditions as climate change progresses, referred to here as globalchange-type drought, yet quantitative assessments of the triggers and potential extent of drought-induced vegetation die-off remain pivotal uncertainties in assessing climate-change impacts. Of particular concern is regional-scale mortality of overstory trees, which rapidly alters ecosystem type, associated ecosystem properties, and land surface conditions for decades. Here, we quantify regional-scale vegetation die-off across southwestern North American woodlands in 2002-2003 in response to drought and associated bark beetle infestations. At an intensively studied site within the region, we quantified that after 15 months of depleted soil water content, >90% of the dominant, overstory tree species (Pinus edulis, a piñ on) died. The die-off was reflected in changes in a remotely sensed index of vegetation greenness (Normalized Difference Vegetation Index), not only at the intensively studied site but also across the region, extending over 12,000 km 2 or more; aerial and field surveys confirmed the general extent of the die-off. Notably, the recent drought was warmer than the previous subcontinental drought of the 1950s. The limited, available observations suggest that die-off from the recent drought was more extensive than that from the previous drought, extending into wetter sites within the tree species' distribution. Our results quantify a trigger leading to rapid, drought-induced die-off of overstory woody plants at subcontinental scale and highlight the potential for such die-off to be more severe and extensive for future global-change-type drought under warmer conditions. tree mortality ͉ vegetation dynamics ͉ climate change impacts ͉ woodlands ͉ Pinus edulis
There are few empirical tests of the relationship between local resource production and community social systems. This paper reports the results of research on two communities in northern Idaho: one timber‐dependent, the other mining‐dependent. Data were collected for 13 indicators of resource production and 15 indicators of social change for periods up to 65 years. Regression analysis was used to test if community social change is associated with the production level of local resource systems. The final models support the hypothesis in both communities. The form, lag condition, and strength of the relationship is complex and may vary with the dependent indicator. The original causal image—the rural community with a social order that directly responds to changes in local resource production—is blurred. Suggestions are made for future research.
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