Print PageDrought in the Southwest, which occurred between 1998 and 2004, caused widespread tree mortality. Here we used two methods to examine drought impacts to aspen (Populus tremuloides), corkbark fir (Abies bifolia), Douglas fir (Pseudotsuga menziesii), Engelmann spruce (Picea engelmannii) and white fir (Abies concolor) in spruce-fir ecosystems near Los Alamos, New Mexico. Sixteen plots, between 1998 and 2005, were sampled for both live and dead trees, by species and size class. All plots sampled before 2002 were classified as pre-drought, while all plots sampled during 2002 or later were classified as post-drought. In addition, of the four plots sampled in 2005, all dead trees were annotated as being killed recently by the drought or having been killed previous to the drought.
Results/Conclusions
The results suggested that drought contributed to the mortality of all species, except aspen. Aspen mortality appeared to be largely a function of post-fire, successional processes. Only limited data were available for corkbark fir. However, 100 percent of corkbark fir mortality, sampled in 2005, resulted from drought. The remaining species, Douglas fir, Engelmann spruce and white fir showed similar demographies through time and across size classes. Therefore, these species were grouped together and the diameter classes encompassing 0-30 cm were grouped for further analysis. Post-2001 mortality in this group was significantly greater (probability of the one-tail, t-test statistic = 0.0276) than pre-2002 mortality. These results were consistent with the census data in the 2005 sample plots, which indicated that 5.50 percent of the white fir mortality, 39.09 percent of the Engelmann spruce mortality, and 32.50 percent of the Douglas fir mortality resulted from drought.
Although not as dramatic, these results are consistent with drought mortality levels documented in piñon-juniper woodlands and ponderosa pine forests, found at lower elevations in the Jemez Mountains.
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