Characterizing tree morality after extreme drought and insect outbreaks in the southern Sierra NevadaThis article is part of a larger document. View the larger document here.
The interplay of past management practices, higher temperatures, extended drought, and insect
outbreaks has resulted in unprecedented levels of tree mortality across the southern Sierra Nevada Mountains of
California. To characterize patterns in tree mortality, we collected repeated forest measurements on 255 variableradius
plots during 2015 and 2016. From initial measurements in spring 2015, sugar pine (Pinus lambertiana) and
ponderosa pine (P. ponderosa) mortality increased from 30 percent to 80 percent by summer 2016. Incense cedar
(Calocedrus decurrens) mortality remained relatively stable in 2015 but increased to 40 percent in summer 2016.
There were positive relationships for live crown ratios and survivorship for both sugar pine and white fir (Abies
concolor). In addition, there was a positive effect of diameter on survivorship for ponderosa pine in spring 2015;
however, this relationship was reversed in summer 2016. Our results indicate that the effects of this mortality
event were variable among species with initial survivorship positively related to tree size.