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Stand density, drought, and herbivory constrain ponderosa pine regeneration pulse

January 6, 2020

Trees in dry forests often regenerate in episodic pulses when wet periods coincide with ample seed production. Factors leading to success or failure of regeneration pulses are poorly understood. We investigated the impacts of stand thinning on survival and growth of the 2013 cohort of ponderosa pine (Pinus ponderosa Douglas ex P. Lawson & C. Lawson) seedlings in northern Arizona, United States. We measured seedling survival and growth over the first five growing seasons after germination in six stand basal areas (BAs; 0, 7, 14, 23, 34, and 66 (unthinned) m2·ha−1) produced by long-term experimental thinnings. Five-year survival averaged 2.5% and varied among BAs. Mean survival duration was longer in intermediate BAs (11 to 16 months) than in clearings and high BAs (5 months). The BAs of 7, 14, and 23 m2·ha−1 had >2600 5-year-old seedlings·ha−1. In contrast, regeneration was lower in the clearing (666 seedlings·ha−1) and failed completely in the 34 m2·ha−1 and unthinned treatments. Seedling survival was highest during wet years and lowest during drought years. Many surviving seedlings had no net height growth between years 4 and 5 because of stem browsing. Results indicate that natural regeneration of ponderosa pine is influenced by stand BA, drought, herbivory, and interactions between extreme climatic events.

Publication Year 2020
Title Stand density, drought, and herbivory constrain ponderosa pine regeneration pulse
DOI 10.1139/cjfr-2019-0248
Authors Thomas E. Kolb, Kelsey Flathers, John Bradford, Caitlin M. Andrews, Lance A. Asherin, W. Keith Moser
Publication Type Article
Publication Subtype Journal Article
Series Title Canadian Journal of Forest Research
Index ID 70208722
Record Source USGS Publications Warehouse
USGS Organization Southwest Biological Science Center