Calcium-rich tundra, wildlife, and the “Mammoth Steppe”

Abstract

Moist calcareous tundra has many ecosystem properties analogous to those of the hypothesized “Mammoth Steppe” or steppe tundra of glacial Beringia, and today it is an important range land for arctic wildlife. Moist calcium-rich tundras are associated with moderately drained fine-grained arctic soils with relatively high soil pH. Compared to tussock tundra, moist calcareous tundra has 10 times the extractable Ca in the active layer, half the organic layer thickness, and 30% deeper active layers. The vegetation is less shrubby than that of tussock tundra, has twice the vascular-plant species richness, greater habitat diversity at multiple scales, and contains plants with fewer antiherbivory chemicals and more nutrients (particularly calcium). It has some properties that are unlike the hypothesized steppe tundras, including abundant sedges and a mossy understory. Moist calcium-rich tundra is common north of the acidic shrubby southern tundras and south of the sparsely vegetated polar deserts. Successionally, this tundra type occurs between the present-day dry calcareous dune vegetation and tussock tundra. Thus, at least conceptually, moist calcareous tundra is intermediate between the steppe tundra and tussock tundra and provides insights regarding the transitions from cold arid Beringian ecosystems to present-day moist acidic tundra.