Collaborative Research: SG: Does variation in development explain variation in phenological responses to temperature?

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The boreal forest (a habitat that covers 29% of the US and Canada) is undergoing earlier springs, warmer summers, and extended falls. While many plants respond to warmer springs by flowering earlier, a significant number of species do not respond, and some even show delayed flowering. Such patterns are inconsistent with predictions based on well-understood physiological responses to temperature. For plants that grow in boreal forest, however, the process that ends in the bursting of flower buds actually begins a year or more before flowers open, a developmental process known as "preformation". This research will test the hypothesis that the effects of rising temperatures on the extended period of preformation explain delayed flowering. The effects of rising temperatures on preformation may limit the extent to which plants can adapt to environmental variability. The discovery of a strong role for development could dramatically improve our ability to predict the timing of flowering in high-latitude communities and may also provide insights into how temperate trees and shrubs, the majority of which preform flowers, will respond to increasing temperatures. This project will also involve citizen scientists, who will obtain phenology, temperature and snow depth data from across Alaska.This project will evaluate three potential effects of warm temperatures on the development of flower primordia: increasing temperatures could 1) induce early bud set and dormancy; 2) induce more rapid development and / or a delay in bud set so that some buds mature in the fall of the year in which they were initiated; and 3) delay flower initiation. Eight species of understory boreal shrubs will be studied; their small stature makes them amenable to experimental temperature manipulation, and because they are woody they likely share features of preformation with the dominant trees and shrubs of diverse plant communities. Open-topped chambers will be used to raise temperatures for one or two growing seasons, and development will be followed over the course of three years. Temperature will be related to potential developmental determinants of flower opening: timing of initiation, rate of development, and cessation of growth. By manipulating and analyzing the effects of time of snow melt, date of growth initiation and temperature across the entire multi-year trajectory of flower development for representative species, the researchers will identify the mechanisms that underlie "non-typical" phenological responses.