Mapping the vulnerability of giant sequoias after extreme drought in California using remote sensing.

Between 2012 and 2016, California suffered one of the most severe droughts on record. During this period Sequoiadendron giganteum (giant sequoias) in the Sequoia and Kings Canyon National Parks (SEKI), California, USA experienced canopy water content (CWC) loss, unprecedented foliage senescence, and, in a few cases, death. We present an assessment of the vulnerability of giant sequoia populations to droughts that is currently lacking and needed for management. We used a temporal trend of remotely sensed CWC obtained between 2015 and 2017, and recently georeferenced giant sequoia crowns to quantify the vulnerability of 7,408 individuals in 10 groves in the northern portion of SEKI. CWC is sensitive to changes in liquid water in tree canopies; therefore, it is a useful metric for quantifying the response of sequoia trees to drought. Temporal trends indicated that 9% of giant sequoias had a significant decline or consistently low CWC, suggesting these trees were likely operating at low photosynthetic capacity and potentially at high risk to drought stress. We also found that 20% of the giant sequoias had an increase or consistently high level of CWC, indicating these trees were at low risk to drought stress. These vulnerability categories were used in a random forest model with a combination of topographic, fire-related, and climate variables to generate high-resolution vulnerability risk maps. These maps show that higher risk is associated with lower elevation and higher climate water deficit. We also found that sequoias at higher elevations but located near meadows had higher vulnerability risk. These results and the vulnerability maps can identify vulnerable sequoias that may be difficult to save or locations of refugia to be protected, and thus may aid forest managers in preparation for future droughts.

Patients with aortic stenosis: who should undergo noncardiac surgery in a rural hospital?

PURPOSE: Sometimes, patients in rural settings with aortic stenosis not severe enough to require valve replacement desire to undergo elective noncardiac procedures at their small local hospital. This has important implications for all stakeholders, including perianesthesia nurses. The purpose of this evidence-based article was to determine when it is appropriate for patients with aortic stenosis to undergo noncardiac surgery in this setting. METHODS: A systematic search strategy was applied. FINDINGS: The search revealed 12 evidence sources meeting the inclusion criteria: one clinical practice guideline, one cohort study, two nonrandomized control trials, four case-control studies, and four narrative reviews. CONCLUSIONS: The evidence suggests that patients with aortic stenosis undergoing moderate and higher risk noncardiac surgical procedures require expertise and resources often unavailable in small rural hospitals. These patients should be appropriately evaluated before the procedure. It may be appropriate for these patients to undergo low risk noncardiac surgery in small rural hospitals if stable, and there is a low likelihood of fluid shifts and unstable hemodynamics.