Warming and snow experiment plant species composition data for Saddle snowfence, 1993 - 2000.

• Main Author: Walker, Marilyn
• Format: Dataset
• Language: English
• Published: Environmental Data Initiative 2019
• Subjects: Tundra
• Online Access: https://dx.doi.org/10.6073/pasta/61a8584e0c234e53dc7c373d6687e442; https://portal.edirepository.org/nis/mapbrowse?packageid=knb-lter-nwt.159.2

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. ITEX studies at Niwot Ridge, a logical outgrowth of the long-term phenology studies there, uses a factorial design based around the long-term snowfence experiment. Twenty cones are placed behind the snowfence, distributed at 10, 25, 45, and 75 m from the fence; each cone is paired with an adjacent plot. Beginning with the 1995 season, 24 additional plots were implemented outside of the snowfence influence. Twelve cones are distributed beyond both the north and south edges of the snowfence area, at 10, 25, 45, and 75 m behind the line of the snowfence; each cone is paired with an adjacent plot. This results in the following treatments: increased winter snow, increased summer temperature, increased snow and increased temperature, and control. Key phenologic, growth, and reproductive traits are being followed on marked individuals of Acomastylis (Geum) rossii and Bistorta (Polygonum) bistortoides, and complete species composition is being monitored. The point-quadrat technique used was identical to that described by Auerbach (1992): The point-quadrat method was used for estimating canopy stratification and plant cover. Aluminum point-quadrat frames were 1-m^2 in size, with double-layer filament spaced 10 cm apart to make a 10 x 10 cm grid for a total of 100 sample points per plot. Before sampling, the point-quadrat frame was leveled and plots were permanently marked in the following manner. Aluminum tags were nailed into the ground so that a frame could be repositioned in the same location from year to year; i.e., tags with a hole in the middle were used to define the locations for the point frame legs and four tags with a "X" stamped on them (positioned somewhere inside each of the frame corners) were used to define alignment of the frame by positioning the string crossings over these "X"s. Distances from the frame to a top canopy plant hit and to a surface layer plant hit were measured to the nearest 0.5 cm and recorded. Plant genus and species were also recorded at both hits at each point.