The Canopy Structure of Tundra Plant Communities at Barrow, Alaska, and Niwot Ridge, Colorado

Abstract

The seasonal development of foliage area index (foliage area per unit ground surface, F) was compared by inclined point quadrat analysis for an arctic and two alpine tundra communities. An extensive series of other arctic and alpine communities were also compared at the peak of the vegetative season which occurred between July 25 and August 9 in 1971 in both the arctic and alpine areas. At this time, F values for living foliage of the arctic communities were all less than 1.0 while F ranged between 1 and 2.2 in the alpine sites. A simulation of radiation extinction in an arctic and an alpine community indicated that lower solar radiation intensities in the long arctic day were absorbed in the sparsely stocked canopy to about the same degree on a daily basis as the higher radiation intensities in the denser community of the alpine tundra. The significance of senescent foliage tissue displayed at the top of the alpine communities is also discussed.