Ione Clay Barrens
Map SatelliteClimatic and edaphic conditions combine in this area to produce one of the most remarkable and distinctive ecological islands in the State. Several plant species are restricted to this area and others occur as disjuncts.
The dominant plant is the lone manzanita, Arctostaphylos myrtifolia, which is restricted to this area and to several small nearby localities with similar soil conditions. This low-lying manzanita is a distinctive olive green which contrasts with the gray of the whiteleaf manzanita, Arctostaphylos viscida, and the taller Parry manzanita, Arctostaphylos manzanita which form part of the chaparral cover surrounding and impinging upon parts of the island.
The rare wild buckwheat, Eriogonum apricum, is found only on the island and grows in a few inhospitable spots where other plants do not grow. This plant differs from the 75-odd other species of Eriogonum to the extent that its nearest relatives have not been determined.
A shrubby rockrose, Helianthemum scoparium, is confined to the island and its immediate vicinity. Other plants of restricted distribution occurring on the island include Ceanothus tomentosus, Horkelia parryi, Mimulus viscidus, and Plagiobothrys scriptus.
Among the disjuncts found here is Juncus confusus, a Rocky Mountain species occasionally found in the Sierra above 1,200 meters (3,950 ft). Other disjuncts include Agrostis elliottiana, Lotus stipularis var. stipularis and Scribneria bolanderi.
The boundaries of the island coincide with the limits of the outcrop of the lone formation in this region. This formation is composed of kaolinitic clay materials, quartz sand and ironstone. It is a marine sedimentary formation laid down in the Upper Eocene and it represents the last marine invasion of the valley. Mining cuts exhibit a colorful display of soil horizons, red soil resting on a base of white kaolinitic clay. The hilltops are capped by sheets of laterite or hard, indurated ironstone several feet thick. The hardpan clay is very poor in minerals needed for plant growth and is highly acidic (pH 2.9-3.95).
The soil horizon sequences here are identical to those in tropical India, Africa and Hawaii. These lone laterite profiles are probably survivors of the tropical climate that prevailed in the area during part of the Tertiary period. Few, if any other sites on the continent preserve an ancient soil regime in such magnitude and splendor.
Integrity: Clay, for use as a fire clay, has been quarried in the area for a number of years and since 1955 the white sand which is relatively free of iron has been extracted for glass manufacture. If quarrying operations are increased or new quarries opened, the main plant stands may be destroyed.
Use: Private
Ref: Gankin, R. and Major, J., 1964. Arctostaphylos myrtifolia, its Biology and Relationship to the Problem of Endemism. Ecology Vol. 45 #4, p. 792-808.
February 1975
Inventory of California Natural Areas
Revision © 2009 Steven Louis Hartman