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Observations on the Ecology of Astragalus tennesseensis
Carol C. Baskin, Jerry M. Baskin and Elsie Quarterman
The American Midland Naturalist
Vol. 88, No. 1 (Jul., 1972), pp. 167-182
Published by: The University of Notre Dame
Stable URL: http://www.jstor.org/stable/2424496
Page Count: 16
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Astragalus tennesseensis Gray, a decumbent, perennial legume, is endemic to the cedar glades of northern Alabama and central Tennessee. The present center of distribution is in central Tennessee and only one population is known in northern Alabama. Its geographical range once extended to north-central Illinois and west-central Indiana but within the past few decades it apparently has disappeared from these areas. Within the cedar glades of central Tennessee, the species grows mostly in the transition zone between the open glades and glade thickets or woods. Environmental conditions in this zone with respect to light, temperature, and soil and atmospheric moisture are intermediate between those of open glade and glade woods. The ecological life cycle of this species is as follows: seeds germinate in early spring, and the seedlings grow slowly, taking several years to reach reproductive maturity. Very few of the seedlings survive to adults. Flowering occurs from mid-April to mid-May, and cross-pollination is necessary for seed set. Fruits and seeds are mature by early June, fruits fall from plants by mid-July and seeds are shed throughout the next year. Plants remain vegetative (nondormant) throughout the summer, shed their leaves in early autumn, after which vegetative buds at the caudex produce an overwintering rosette of leaves. Flower buds are initiated the following April, and meiosis and pollen grain formation occur as the buds begin to swell. Observations made over the past 6 years in the middle Tennessee cedar glades suggest that the species is declining due to habitat disturbance and destruction by man. As destruction of its cedar glade habitat continues, the species, no doubt, will continue to decline and may even become extinct.
The American Midland Naturalist © 1972 The University of Notre Dame