International Tundra Experiment: Vegetative responses of Dryas octopetala to increased summer temperature and precipitation.

The International Tundra Experiment (ITEX) is a consortium of research sites seeking to understand the response of tundra plant populations to changes in growing season temperatures through a simple temperature manipulation and transplant experiment. The research goal is to examine the phenologic and reproductive responses of a set of species to experimentally-induced warming at a network of sites. The ITEX design is hierarchical, with sites participating at whatever level they are able. At the minimum, participation in ITEX requires climate monitoring (using the LTER MSR standards), a temperature manipulation using one of three possible designs, and monitoring phenologic and reproductive variables for at least one designated ITEX species or two other species. The temperature manipulation is achieved through use of conical or hexagonal open-top chambers of solar fiberglass, which have been shown to increase the air temperature at the surface approximately 3 degrees C. Dry tundra east of the Saddle on Niwot Ridge is being subjected to increased summer temperatures using ITEX chambers and a portion of the experimental plots are receiving supplemental summer rainfall at 50% above the long-term June + July + August precipitation total. Chambers increase summer air temperatures on average by 2.5 degrees Celsius, while soil temperatures are increased by 1.8 degrees Celsius. Organismic responses including the vegetative and reproductive responses of Dryas are being assessed and ecosystem carbon flux, soil solutions, and soil nitrogen content are being measured. This site is part of a Dryas transect of ITEX study locations including Toolik Lake, AK; Svalbard, Norway; Latnaja, Sweden; and Ellesmere Island, Canada