Warming experiments elucidate the drivers of observed directional changes in tundra vegetation.

Few studies have clearly linked long-term monitoring with in situ experiments to clarify potential drivers of observed change at a given site. This is especially necessary when findings from a site are applied to a much broader geographic area. Here, we document vegetation change at Barrow and Atqasuk, Alaska, occurring naturally and due to experimental warming over nearly two decades. An examination of plant cover, canopy height, and community indices showed more significant differences between years than due to experimental warming. However, changes with warming were more consistent than changes between years and were cumulative in many cases. Most cases of directional change observed in the control plots over time corresponded with a directional change in response to experimental warming. These included increases in canopy height and decreases in lichen cover. Experimental warming resulted in additional increases in evergreen shrub cover and decreases in diversity and bryophyte cover. This study suggests that the directional changes occurring at the sites are primarily due to warming and indicates that further changes are likely in the next two decades if the regional warming trend continues. These findings provide an example of the utility of coupling in situ experiments with long-term monitoring to accurately document vegetation change in response to global change and to identify the underlying mechanisms driving observed changes.

Clinical role of F-18 fluorodeoxyglucose positron emission tomography imaging in patients with lung cancer and suspected malignant pleural effusion.

STUDY OBJECTIVES: The goals of this study were to determine the sensitivity, specificity, and predictive accuracy of F-18 fluorodeoxyglucose positron emission tomography (PET-FDG) imaging in detecting metastatic disease involvement of pleura and/or presence of malignant pleural effusion in patients with proven lung cancer. We wanted to compare efficacy of PET-FDG imaging to CT scanning in differentiating benign pleural effusion from malignant effusion and/or pleural involvement in patients with lung cancer. METHODS: We studied 35 patients with biopsy-proven lung cancer and abnormal findings on CT scanning for presence of pleural effusion (n = 34) and/or pleural thickening or nodular involvement (n = 4). The results of positron emission tomography and CT scanning were compared to pleural cytology (n = 31), histologic findings of pleural biopsy (n = 3), and/or clinical follow-up (n = 3) for at least 1 year for presence or absence of malignant pleural effusion. RESULTS: PET-FDG imaging correctly detected the presence of malignant pleural effusion and malignant pleural involvement in 16 of 18 patients and excluded malignant effusion or pleural metastatic involvement in 16 of 17 patients (sensitivity, specificity, and accuracy of 88.8%, 94.1%, and 91.4% respectively). CONCLUSION: PET-FDG imaging is a highly accurate and reliable noninvasive test to differentiate malignant from benign pleural effusion and/or pleural involvement in patients with lung cancer and findings of suspected malignant pleural effusion on CT scanning.