| Summary: | Includes bibliographical references. 2015 Summer. Altered seasonality is one of the many consequences of climate change that is affecting plant communities worldwide. Warmer temperatures, altered precipitation patterns, and changes in duration of snow cover are a few of the seasonal changes taking place. These abiotic cues are key drivers of the annual life cycles of plants, and effects of their changes vary across ecosystems, plant communities, and individual species. Regardless, changes in vegetative phenology, through earlier and/or later leaf greening and senescence, determine the timing and extent of the growing season. The consequent impacts on ecosystem function include feedbacks to local climate, changes in trophic interactions, altered nutrient cycling and plant community dynamics, and changes in plant production and carbon balance. Because Arctic ecosystems are undergoing more rapid climate change relative to lower latitudes, plant community responses there may be indicative of changes to come in other systems. In the Arctic, seasonal changes are characterized by warmer temperatures and altered duration of snow cover. While landscape-scale observations of Arctic regions suggest a general trend towards earlier onset of greening, later plant senescence, and increased aboveground production, experiments are needed to determine the species and mechanisms that are driving these trends. Over three years, we experimentally altered the timing of snowmelt and increased temperature in moist acidic tundra. We investigated plant phenological and functional response to these changes. First, we asked how early snowmelt and warming affect the timing of leaf appearance and expansion, and whether spring phenological shifts would affect aboveground production of individual species. Earlier leaf expansion and growth are expected with warmer temperatures; however, in seasonally snow-covered ecosystems, timing of snowmelt may be an additional cue of plant species green-up. We found that altered seasonality led to ...
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