Soil Temperature and Nutrient Cycling in the Tussock Growth Form of Eriophorum Vaginatum

Chapin, F; Van Cleve, Keith; Chapin, Melissa

"(1) Eriophorum vaginatum produces 20-cm-tall tussocks at an interior Alaskan tundra site. These tussocks become snow-free sooner and experience a 5-10% longer growing season than between-tussock areas. (2) Within-tussock soils thaw faster, reach maximum summer temperature sooner, are 6-8⚬ C warmer, and are thermally more stable than soils at comparable depths between tussocks. (3) Tussock plants have twice as deep an organic horizon to exploit as plants rooted between tussocks. In spite of low bulk density, portions of this organic soil have higher concentrations of soluble and exchangeable potassium, total nitrogen and total phosphorus than does the underlying mineral soil. Within the organic horizons, concentrations of exchangeable potassium, magnesium and manganese are highest at the tussock surface and decrease with depth. (4) Soil organic carbon and, presumably, organically-bound soil nutrients such as nitrogen, phosphorus and calcium cycle 3-10-times more rapidly within the tussock than beneath it. (5) At the end of the growing season 75% of E. vaginatum roots are found in the elevated portion of the tussock. Root density (9 cm root per cm3 of soil) is sufficiently high that E. vaginatum roots may exploit virtually the entire tussock-soil volume each year. (6) Eriophorum vaginatum leaf biomass per unit area measured in the centre of tussocks is five-fold greater than the total vascular leaf biomass averaged over the whole site. (7) We suggest that the tussock growth form, with its favourable thermal and nutritional micro-environment, may be largely responsible for the high productivity and widespread distribution of E. vaginatum."

Soil Temperature and Nutrient Cycling in the Tussock Growth Form of Eriophorum Vaginatum

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