Alternative interpretation and scale-based context for 'No evidence of recent (1995-2013) decrease of yellow-cedar in Alaska' (Barrett and Pattison 2017)

摘要

In their analysis of resampled and remeasured plot data from the USDA Forest Service Forest Inventory and Analysis (FIA) program, Barrett and Pattison (2017, Can. J. For. Res. 47(1): 97-105, doi: 10.1139/ cjfr-2016-0335) suggest that there is neither evidence of a recent regional decrease in yellow-cedar (Callitropsis nootkatensis (D. Don) Oerst. ex D. P. Little) live tree basal area nor a decrease in the species' extent in southeastern Alaska. Here, we identify substantial, broad-scale agreement between their estimated extent of concentrated yellow-cedar mortality and that resulting from a complementary, existing body of research into yellow-cedar decline spanning 35 years. However, we also discuss concerns that the FIA remeasurement data used did not match the spatial distribution of the decline (e.g., excluding areas of known active decline in wilderness areas) and that the temporal coverage of FIA data (1990s to 2000s) was inappropriately compared with a cumulative decline map that spans several decades, meshing recent mortality with mortality that occurred up to a century ago. We provide an alternative explanation of Barrett and Pattison's results in the context of ongoing yellow-cedar distribution and decline research in southeastern Alaska and support our interpretation by focusing on the temporal and spatial aspects of decline.