2002 ARCSS All-Hands Workshop

Growth of Sphagnum Under Extended Growing Season at Toolik Lake, Alaska

Sarah J. Colby¹, Steven F. Oberbauer², Lorraine E. Ahlquist^3
1Department of Biological Sciences, Florida International University, Miami, FL, 33199, USA, scolby53@hotmail.com
²Department of Biological Sciences, Florida International University , Miami, FL, 33199, USA
³Department of Biological Sciences, Florida International University, Miami, FL, 33199, USA

Climate models predict that climate warming will be greatest at high latitudes. Along with temperature, the length of the growing season is anticipated to increase with climate change in the Arctic. While considerable effort has been dedicated to studying the effects of altered season length on vascular plants, little attention has been paid to the responses of mosses, including the tundra dominant Sphagnum. Because Sphagnum has previously been shown to be photoinhibited in arctic tundra, we hypothesized that Sphagnum would decrease growth in response to early season snowmelt. Alternatively, Sphagnum may increase growth due to additional seasonal light and/or season duration. During two arctic summers, 2000–2001, we examined the vertical growth response of Sphagnum species in situ using the cranked-wire method under an artificially extended growing season. Summer season was extended by careful snow removal early in the season. In 2000, the growth rate of Sphagnum under the extended season was considerably lower than that of controls in the beginning of the season, but after six weeks growth rates were similar. In 2001, growth of Sphagnum under the extended season remained below that of the controls throughout the entire season. These results indicate that earlier snowmelt has a negative effect on the growth rate of Sphagnum, possibly due to photoinhibition. However, the response of Sphagnum may be the result of earlier snowmelt affecting factors other than light such as early season temperature, water table, depth of the active layer, and Sphagnum water content. During the summer of 2002, we plan to investigate how light and these other important factors affect Sphagnum growth and physiology in response to an extended growing season.

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