When Snow Melts Early: The Unusual Alpine Plant Life Histories During the Summer of 2012
Abstract
Many of the plant communities where earlier plant growth has been observed during the late 20th and early 21st Centuries are in seasonally snow covered landscapes. In these communities, snow cover, temperatures, day length, soil moisture, and other environmental cues determine the timing and duration of the window within which plants green and fade annually. In short-statured plant communities where snow accumulates, such as in the alpine tundra, rapid plant growth only begins after the snow melts, but may not occur immediately following snowmelt, especially when snow melts early. Multiple climate cues protect plants from emerging too early in environments where early growth could lead to tissue loss or death. Similarly, perennial plants senesce (shift to dormancy) to prevent greater tissue loss or death when seasonal environments become unfavorable for growth and tissue maintenance. Our objective was to determine how early snowmelt and climate warming influence alpine plant life histories, and due to the unusual, early loss of snow cover in 2012, we had the opportunity to characterize alpine plant life histories in an extreme climate year. We monitored when species first expanded their leaves and when whole leaf color change first occurred. These life history events mark the onset of the growing season and the onset of senescence for individual species and the plant community, which determine the window for plant growth. Subtle topographic features at our site and an experimental acceleration of snowmelt (via radiation absorbing shadecloth) led to variation in the timing of snowmelt (April 8 to May 10) across the 10 plots (8 m x 12 m) within our experiment. Within each plot, we monitored 1m x 1m control and experimentally warmed areas (via open top chambers). We found that earlier snowmelt lengthened the window for plant growth in the alpine tundra, because many species expanded their leaves within a few days to a week following snowmelt. However, warming shortened the window for plant growth due to earlier leaf loss. The summer of 2012 was unusual, because snowmelt was exceptionally early, temperatures were high, and almost no precipitation fell (< 1 cm) in May and June. Thus, species began senescing in early to mid June, when in a typical year snowmelt and leaf expansion would be occurring. For some species, the window for plant growth was over before it would typically have begun and prior to when monsoon rains typically begin in early July. This unusual timing for alpine plant life histories may be more common when winter and summer climates change.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.B21I..08S
- Keywords:
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- 0438 BIOGEOSCIENCES / Diel;
- seasonal;
- and annual cycles;
- 0439 BIOGEOSCIENCES / Ecosystems;
- structure and dynamics;
- 0476 BIOGEOSCIENCES / Plant ecology;
- 1630 GLOBAL CHANGE / Impacts of global change