Stand-scale tree mortality factors differ by site and species following drought in southwestern mixed conifer forests

• Published in: Forest ecology and management Vol. 330; pp. 171 - 182
• Main Authors: Kane, Jeffrey M., Kolb, Thomas E., McMillin, Joel D.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.10.2014; Elsevier
• Subjects: Abies concolor; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Conifers; Drought; Droughts; Forest management. Stand types and stand dynamics. Silvicultural treatments. Tending of stands. Natural regeneration; Forestry; Forests; Fundamental and applied biological sciences. Psychology; Mortality; Pine; Pinus flexilis; Populus tremuloides; Pseudotsuga menziesii; Scolytidae; Stand types and stand dynamics. Silvicultural treatments. Tending of stands. Natural regeneration; Stands; Supports; Synecology; Terrestrial ecosystems; Tree death; Trees; USA, Arizona; Tree death; Populus tremuloides; Pinus flexilis; Abies concolor; Drought; Pseudotsuga menziesii; Site; Forest stand; Mortality; Forest ecology; Salicaceae; Southwest; Dicotyledones; Angiospermae; Gymnospermae; Softwood forest tree; Forestry; Death; Hardwood forest tree; Coniferales; Spermatophyta; Species; Mixed forest stand; Coniferous forest
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/j.foreco.2014.06.042

•We examined the stand level factors of tree mortality in southwestern mixed-conifer forests of northern Arizona.•We found varied but substantial mortality in most species between 1996 and 2006.•Tree mortality differed by sites and species and was significantly related to climate, biotic, and topographic factors. Impacts of drought on tree mortality in high-elevation mixed-conifer forests of southwestern U.S. are poorly understood. A recent extended and severe drought in the region provided an opportunity to investigate the patterns and factors associated with tree mortality in this forest type. Specifically, we quantified mortality that occurred between 1995 and 2008 of four tree species, white fir (Abies concolor), limber pine (Pinus flexilis), trembling aspen (Populus tremuloides), and Douglas-fir (Pseudotsuga menziesii), in mixed-conifer forests over three sites in northern Arizona within 84, 0.02ha plots. We found: (1) varied but substantial tree mortality (4–56% by basal area) in most species between 1996 and 2006 in association with recent severe and prolonged drought; (2) tree mortality differed among sites and species with aspen and white fir having the most mortality (>30% by basal area); (3) relationships between tree mortality and most climatic factors (e.g. temperature, precipitation, Palmer Drought Severity Index) were lagged 1–4yr; (4) bark beetle attack and intraspecific tree basal area were consistently and positively related to tree mortality for most species and sites, whereas topographic and other stand characteristics were less consistently related to mortality. Results show that aspen, Douglas-fir, and white fir were more vulnerable to recent drought-associated mortality than limber pine. Associations between tree mortality and intraspecific basal area support further evaluation of treatments that reduce intraspecific competition within stands to lower risks of tree mortality in southwestern mixed conifer forests.