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Abstract
Multi-cohort stands maintained by the U.S. Department of Agriculture, Forest Service on the Penobscot Experimental Forest (PEF) have played a central role in research into the mechanisms that regulate ontogenetic trends in forest conifers as they control effects due to population, climatic, and edaphic factors. These long-term silvicultural studies have permitted direct comparisons of trends in morphology and physiology across life-stages, and experimental reciprocal grafting research among juvenile, mid-aged and old-growth individuals has proved an important approach to discriminating between trends due to tree size and those related to life-stage. The results of this research have provided valuable insight into the physiological mechanisms that underlie age-related trends in growth and development. Two decades of study on the PEF have identified a surprising paradox of high photosynthetic rates and declining stemwood production that characterizes the transition from mid-aged to old-growth life-stages in spruce. Ultimately, this research has led to a novel explanation for that paradox in the ecologically stable strategy hypothesis, which integrates environment, intrinsic regulation of development, and life-stage specific challenges.
Parent Publication
Citation
Day, Michael E.; Greenwood, Michael S.; Spencer, Katherine; Adams, Stephanie L. 2014. Understanding patterns and regulatory pathways in conifer ontogeny: the role of the Penobscot Experimental Forest. In: Kenefic, Laura S.; Brissette, John C., comps. Penobscot Experimental Forest: 60 years of research and demonstration in Maine, 1950-2010. Gen. Tech. Rep. NRS-P-123. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 138-146.
