Responses of Diversity and Growth-Form Dominance to Fertility in Alaskan Tundra Fellfield Communities

The effects of NPK fertilization on species composition and diversity in tundra fellfield communities were measured after 1, 3, and 5 growing seasons. The outcome did not agree with the idea that fellfield is a microsuccessional mosaic or with predictions of the intermediate disturbance hypothesis. The outcome did agree with the hypothesis that growth-form dominance is causally related to soil fertility. Growth-form composition changed markedly, with graminoids replacing evergreen dwarf shrubs as dominants; deciduous dwarf shrubs and forbs changed little in relative abundance. Fertilization increased cover markedly, showing that fellfield vegetation (like many other tundra vegetation types) is nutrient limited.