The effects of cloud cover on photosynthesis in a subalpine forest ecosystem focusing on Niwot Ridge, Colorado

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Sunday, 17 January 2010
Exhibit Hall B2 (GWCC)
Raymond Jay Detweiler, UCAR, Boulder, CO

Climate change is an increasing concern worldwide. In the Northern Hemisphere, sub-alpine ecosystems serve as a major carbon sink. Recent research has shown that these ecosystems are particularly vulnerable to changes in climate. Even small changes in water availability and temperature despite longer growing season length have been shown to cause significant reductions in the ecosystem's ability to sequester carbon. In this study, sensors measuring photosynthetically active radiation, air temperature, relative humidity, sap flow, soil moisture, and soil temperature were deployed to a high-altitude sub-alpine forest ecosystem on Niwot Ridge near Nederland, Colorado to collect data at a high spatial and temporal density. Using the data obtained from these sensors, preliminary observations were made concerning the effects of cloud cover on CO2 sequestration. Data from three representative days in July were analyzed to observe differences among sunny, cloudy, and partly cloudy days. The carbon uptake appeared to be greatest on the sunny day, less on the partly cloudy day, and even less on the completely overcast day. This is contrary to existing research, which suggests that cloudy and partly cloudy days should increase sequestration because light is distributed more evenly and temperatures keep exchange passages within the leaf open. These results may be due to a number of factors, such as the atypical rains that occurred this season and decreased temperatures overall. Reviewing additional data collected this summer and in past years should further improve our understanding of the effects of climate change in sub-alpine forests.