Seasonal Dynamics of Above- and Belowground Production of Vascular Plants at Barrow, Alaska

Abstract

An analysis of the functional relationships of any ecosystem requires an understanding of the mechanisms and controls of primary production—the photosynthetic conversion of solar energy to energy contained in plant biomass. Prior to the support of the IBP, analyses of primary production in U.S. arctic tundra ecosystems were limited primarily to measurements of aboveground standing crop. Dennis and Johnson (1970) summarized the results of many of these analyses and concluded that at Barrow the range of aboveground primary production was 30 to 224 g m-2 when herbivores were excluded. Aboveground standing crop alone, however, may grossly underestimate the magnitude of total standing crop and production since belowground standing crops are large. Scott and Billings (1964) found that a maximum of over 80% of the total standing crop was located belowground in a mesic alpine tundra site. Alexandrova (1958) clearly has documented maximum belowground standing crops of over 800 g m-2 in U.S.S.R. arctic tundra sites. Dennis and Johnson (1970) reported belowground standing crops at Barrow of up to 1435 g m-2, and Khodachek (1969) measured belowground standing crops as high as 4700 g m-2 in the western Taimyr region. The large size of the belowground standing crops suggests that the annual increment of belowground material is an important component in total primary production. Our IBP-supported analysis of the course and magnitude of primary production at Barrow, Alaska, was undertaken to provide a more detailed description of seasonal events and to increase our knowledge of the control of this production by such factors as climatological conditions, soil and nutrient limitations, and the effect of consumers.