Moist calcareous tundra has many ecosystem properties analogous to those of
the hypothesized "Mammoth Steppe" or steppe tundra of glacial Beringia, an
d today it is an important range land for arctic wildlife. Moist calcium-ri
ch 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 organ
ic layer thickness, and 30% deeper active layers. The vegetation is less sh
rubby than that of tussock tundra, has twice the vascular-plant species ric
hness, greater habitat diversity at multiple scales, and contains plants wi
th fewer antiherbivory chemicals and more nutrients (particularly calcium).
It has some properties that are unlike the hypothesized steppe tundras, in
cluding abundant sedges and a mossy understory. Moist calcium-rich tundra i
s common north of the acidic shrubby southern tundras and south of the spar
sely vegetated polar deserts. Successionally, this tundra type occurs betwe
en 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 trans
itions from cold arid Beringian ecosystems to present-day moist acidic tund
ra. (C) 2000 Elsevier Science Ltd. All rights reserved.