【地表形态变化预测】Richard Streeter and Andrew J. Dugmore. Anticipating land surface change. PNAS 2013 vol. 110 no. 15 5779-5784
Abstract
The interplay of human actions and natural processes over varied spatial and temporal scales can result in abrupt transitions between contrasting land surface states. Understanding these transitions is a key goal of sustainability science because they can represent abrupt losses of natural capital. This paper recognizes flickering between alternate land surface states in advance of threshold change and critical slowing down in advance of both threshold changes and noncritical transformation. The early warning signals we observe are rises in autocorrelation variance and skewness within millimeter-resolution thickness measurements of tephra layers deposited in A.D. 2010 and A.D. 2011. These signals reflect changing patterns of surface vegetation which are known to provide early warning signals of critical transformations. They were observed toward migrating soil erosion fronts cryoturbation limits and expanding deflation zones thus providing potential early warning signals of land surface change. The record of the spatial patterning of vegetation contained in contemporary tephra layers shows how proximity to land surface change could be assessed in the widespread regions affected by shallow layers of volcanic fallout (those that can be subsumed within the existing vegetation cover). This insight shows how we could use tephra layers in the stratigraphic record to identify “near misses” close encounters with thresholds that did not lead to tipping points and thus provide additional tools for archaeology sustainability science and contemporary land management.
【地貌过程限制因气候变暖引起的森林形态】Marc Macias-Fauria and Edward A. Johnson. Warming-induced upslope advance of subalpine forest is severely limited by geomorphic processes. PNAS
Forests are expected to expand into alpine areas because of climate w