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Widespread tree mortality associated with drought has been observed on all forested continents and global change is expected to exacerbate vegetation vulnerability. Forest mortality has implications for future biosphere–atmosphere interactions of carbon, water and energy balance, and is poorly represented in dynamic vegetation models. Reducing uncertainty requires improved mortality projections founded on robust physiological processes. However, the proposed mechanisms of drought-induced mortality, including hydraulic failure and carbon starvation, are unresolved. A growing number of empirical studies have investigated these mechanisms, but data have not been consistently analysed across species and biomes using a standardized physiological framework. Here, we show that xylem hydraulic failure was ubiquitous across multiple tree taxa at drought-induced mortality. All species assessed had 60% or higher loss of xylem hydraulic conductivity, consistent with proposed theoretical and modelled survival thresholds. We found diverse responses in non-structural carbohydrate reserves at mortality, indicating that evidence supporting carbon starvation was not universal. Reduced non-structural carbohydrates were more common for gymnosperms than angiosperms, associated with xylem hydraulic vulnerability, and may have a role in reducing hydraulic function. Our finding that hydraulic failure at drought-induced mortality was persistent across species indicates that substantial improvement in vegetation modelling can be achieved using thresholds in hydraulic function. The mechanisms underlying drought-induced tree mortality are not fully resolved. Here, the authors show that, across multiple tree species, loss of xylem conductivity above 60% is associated with mortality, while carbon starvation is not universal.

Future drought is projected to occur under warmer temperature conditions as climate change progresses, referred to here as global-change-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 piǫn) 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 km2 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.

Applied historical ecology is the use of historical knowledge in the management of ecosystems. Historical perspectives increase our understanding of the dynamic nature of landscapes and provide a frame of reference for assessing modern patterns and processes. Historical records, however, are often too brief or fragmentary to be useful, or they are not obtainable for the process or structure of interest. Even where long historical time series can be assembled, selection of appropriate reference conditions may be complicated by the past influence of humans and the many potential reference conditions encompassed by nonequilibrium dynamics. These complications, however, do not lessen the value of history; rather they underscore the need for multiple, comparative histories from many locations for evaluating both cultural and natural causes of variability, as well as for characterizing the overall dynamical properties of ecosystems. Historical knowledge may not simplify the task of setting management goals and making decisions, but 20th century trends, such as increasingly severe wildfires, suggest that disregarding history can be perilous. We describe examples from our research in the southwestern United States to illustrate some of the values and limitations of applied historical ecology. Paleoecological data from packrat middens and other natural archives have been useful for defining baseline conditions of vegetation communities, determining histories and rates of species range expansions and contractions, and discriminating between natural and cultural causes of environmental change. We describe a montane grassland restoration project in northern New Mexico that was justified and guided by an historical sequence of aerial photographs showing progressive tree invasion during the 20th century. Likewise, fire scar chronologies have been widely used to justify and guide fuel reduction and natural fire reintroduction in forests. A southwestern network of fire histories illustrates the power of aggregating historical time series across spatial scales. Regional fire patterns evident in these aggregations point to the key role of interannual lags in responses of fuels and fire regimes to the El Nino-Southern Oscillation (wet/dry cycles), with important implications for long-range fire hazard forecasting. These examples of applied historical ecology emphasize that detection and explanation of historical trends and variability are essential to informed management.

In coming decades, global climate changes are expected to produce large shifts in vegetation distributions at unprecedented rates. These shifts are expected to be most rapid and extreme at ecotones, the boundaries between ecosystems, particularly those in semiarid landscapes. However, current models do not adequately provide for such rapid effects--particularly those caused by mortality--largely because of the lack of data from field studies. Here we report the most rapid landscape-scale shift of a woody ecotone ever documented: in northern New Mexico in the 1950s, the ecotone between semiarid ponderosa pine forest and pinon-juniper woodland shifted extensively (2 km or more) and rapidly (5 years) through mortality of ponderosa pines in response to a severe drought. This shift has persisted for 40 years. Forest patches within the shift zone became much more fragmented, and soil erosion greatly accelerated. The rapidity and the complex dynamics of the persistent shift point to the need to represent more accurately these dynamics, especially the mortality factor, in assessments of the effects of climate change

This paper explores the use of a new pedagogy, the rock art stability index (RASI), to engender deeper understanding of weathering science concepts by students. Owing to its dynamic nature, RASI represents a quintessential actor network for weathering science, because it links task in the landscape with an active material practice and an alternative materialistic world-view recently called for in positivistic science, to create place. Using concept maps as an assessment tool, 571 college undergraduate students and 13 junior high school integrated science students (ages 12—13) were evaluated for increased learning potential between pre- and post-field experiences. Further, this article demonstrates that when students use RASI to learn the fundamental complex science of weathering they make in-depth connections between weathering form and process not achieved through traditional, positivistic weathering pedagogy. We argue that RASI draws upon inherent actor networks which allow students to link weathering form and process to an animate conceptualization of landscape. Conceptualizing landscape as sentient actor networks removes weathering science disciplinary connections and their inherent pedagogic practices. Our focus in this paper is not to challenge weathering ontology and epistemology, but rather to argue that there is a need for a pedagogical paradigm shift in weathering science.

Forest managers throughout the West are anxiously seeking solutions to the problem of \"large crown fires\"--destructive blazes atypical of many forest types in the region. These wildfires have created a crisis mentality in management that has focused on rigid prescriptions for fuels reduction, rather than the restoration of diverse, resilient, and self-regulating forest ecosystems. Sisk et al discuss landscape perspective--the path that begins the journey toward solutions to the problem of destructive crown fires--which captures complex relationships linking resources to the larger forest ecosystem.

The June 2005 Cave Creek Complex Fire is one of the largest historic wildfires to affect Arizona's Sonoran Desert. Post-fire gullying was measured using 1:1900-scale aerial photographs. Detailed comparisons of pre-fire and post-fire imagery, selected using a stratified randomly sampling approach, reveal far more gullies formed in contact with dirt roads than adjacent wildlands, approximately four times more frequently. Post-fire gullies that did not form in contact with roads covered approximately 0.18 percent of the analyzed imagery after the 2005 Arizona monsoon and approximately 0.24 percent after the 2006 Arizona monsoon. Extrapolating this percentage to the total area burned, we estimate gullying to have impacted 456 acres after the 2005 Arizona monsoon and 592 acres after the 2006 Arizona monsoon. A corresponding field-based investigation reveals both deepening and widening of gullying over time.

G Gardner and HL Gorton (1985 Plant Physiol 77: 540) demonstrated that gabaculine (5-amino-1,3-cyclohexadienylcarboxylic acid) inhibits the initial synthesis and resynthesis of spectrophotometrically detectable phytochrome in pea, maize, and oat. We show that the level of immunodetectable phytochrome in pea is unaffected by the presence of gabaculine at a concentration that reduces spectrophotometrically detectable phytochrome up to 10-fold. This result indicates that gabaculine inhibits chromophore synthesis without affecting phytochrome apoprotein synthesis and that chromophore-less phytochrome is stable in the cell.

The EAT (Eating Attitudes Test) was administered to 299 college students (225 females, 74 males) who were taking an introductory nutrition course during the first week of classes and again during the 15th week of classes. Results were tabulated for both the eat-40 and the EAT 26 versions of the test. The EAT had not been reported as previously being administered in a pre-test vs. post-test fashion in a non-clinical setting prior to the current study. A score >29 on the EAT-40 and >19 on the EAT-26 is considered symptomatic for an eating disorder. The study showed that females scored significantly higher than the males on the EAT-40 (p<.006), and on the EAT-26 (p<.0001). However, there were no significant differences by gender in pre-test versus post-test EAT-40 or EAT-26 scores. For the three subscales of the EAT-26, only the Dieting subscale showed significant differences (p<.0001) between males and females, with females scoring higher. Repeated Measures ANOVA showed only significant differences between gender and time on the EAT-26. Pearson's correlation of symptomatic EAT scores with BMI was not significant. It was concluded that a high prevalence of eating disorders existed on the college campus, and that the nutrition education had little, if any, impact on the EAT scores of the students from pre-test to post-test. It was also concluded that the EAT may not be the best measure for determining the effectiveness of nutrition education on the eating attitudes and behaviors of a non-clinical sample of college students. It was proposed that there is a need for an assessment tool designed to look not only at food attitudes and behaviors, but also food intakes and food frequencies, in order to better assess subjects from non-clinical samples.

Logistics engineering, the reinvention of government to make procurement simpler and faster and the concept of lifetime supportability are discussed. The best way to improve logistics is to set up a turnkey contract that obligates the contractor to continuous improvement.