38 J. E. Hobbie 



(41%); moist C. aquatilis / Oncophoms wahlenbergii meadow in moist, flat 

 sites (21%); wet Dupontia fisherij / Eriophorum angustifolium meadow in 

 wet, flat sites and polygon troughs (7%); and wet C aquatilis/ E. 

 russeolum meadow in low polygon centers and at pond margins (15%). 

 The soil conditions controlling this distribution appear to be moisture, 

 redox potential, and soluble phosphorus levels. 



Only a small amount of green tissue is present at the base of the plant 

 stems when the snow melts. Leaves are rapidly formed, however, partly by 

 the translocation of carbohydrates stored below ground, and very rapid 

 growth (0.2 g g ' day^^) begins around 15 June. This lasts for about 10 

 days and then declines to 0.03 g g ' ^ day ^; this rate continues until about 

 1 August when the peak aboveground biomass of 60 to 100 g m~^ is 

 reached. Since the dead remains of several years' previous growth may be 

 still standing, the total plant material is between 150 and 300 g m "^ This 

 production is drastically reduced when there are high numbers of 

 overwintering lemmings. Not only do they cut down the stems and leaves 

 during the summer, but also under the snow they feed almost exclusively 

 on the green stem-bases. 



Photosynthesis continues during August but the photosynthate is 

 mostly incorporated into belowground reserves. In addition, organic 

 materials, minerals, and nutrients are transferred below ground. Roots 

 appear to live 2 to 10 years; their production is around 65 g m~^ year' 

 (Shaver and Billings 1975). Live biomass below ground is frequently 10 

 times that above ground. 



Vegetative reproduction is more reliable than sexual in the short 

 growing season and unfavorable climate, so flowering and seed set are 

 greatly reduced. In four monocotyledons only 2.5 to 10% of the shoots 

 were flowering shoots. 



Bryophytes are abundant at Barrrow but are mostly hidden by the 

 vascular plant canopy. Yet, moss and liverwort primary production ranges 

 up to 160 g m~^ yr~' in wet meadows. These plants contain lower 

 concentrations of macronutrients than do vascular plants but have higher 

 amounts of micronutrients and calcium. This may explain the change in 

 lemming diet to increasing amounts of bryophytes during the winter. 



Lichen abundance is inversely correlated with soil moisture; they are 

 absent in areas where there is any standing water for a week or so in the 

 spring. On better drained meadow sites, the lichen biomass can exceed 50 g 

 m ^ In spite of their low biomass, they are important nitrogen fixers. 

 Unlike the situation in many tundra areas, at Barrow the vertebrates 

 consume few lichens. Lemming stomachs, for example, seldom contain 

 more than 2% lichens. 



The plants in this arctic environment show a number of specialized 

 adaptations. In the spring, at 0°C, they are able to mobilize carbohydrates 

 and inorganic nutrients from belowground reservoirs; this allows very 

 rapid growth early in the growing season. Compensation levels are very 

 low in these plants so that net photosynthesis can proceed for 24 hours a 



