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Physiological and Ecotypic Adaptations of Plants to Salt Desert Conditions in Utah

P. J. Goodman
Journal of Ecology
Vol. 61, No. 2 (Jul., 1973), pp. 473-494
DOI: 10.2307/2259040
Stable URL: http://www.jstor.org/stable/2259040
Page Count: 22
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Physiological and Ecotypic Adaptations of Plants to Salt Desert Conditions in Utah
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Abstract

Plant distribution in the salt desert is important owing to the varying forage value of the species involved. Two dominants, Atriplex confertifolia and Eurotia lanata, occur in perplexing mosaics of slightly differing communities within a single zone of the halosere which surrounds the Great Salt Lake. By contrast, a subdominant, Atriplex nuttallii, is exceptionally widespread, occurring over an eighty-fold range of salinity, in several zones of the halosere. It was suggested that ecotypic variation might partly explain the observed differences in plant distribution. To investigate this, growth of the three species was measured first in the field, then in uniform laboratory culture, and finally in graded salt solutions. In the field, A. nuttallii increased in yield as salinity decreased. The number of accompanying species decreased along the same gradient. When nitrogen fertilizer was added, ephemerals including the poisonous species Halogeton glomeratus increased, but Atriplex nuttallii was unaffected. Very high net assimilation rates were recorded in A. nuttallii and in the accompanying annuals, but these were subject to large, only partly explained, errors. Pure stands of A. confertifolia and Eurotia lanata yielded more of each species than did mixed communities including grasses. The total yield of the mixed communities about equalled that of the pure stands. Interactions were found between species and community. In particular, yield of Atriplex was small in the mixed communities in May, and was decreased by nitrogen addition, suggesting that some kind of competitive stress existed. In uniform cultures, ecotypes of A. nuttallii from saline sites yielded more than those from less saline sites. When plants of A. confertifolia and Eurotia lanata from different communities were transferred to uniform cultures, their yields were very similar. In graded solutions, the species differed in their salt and boron tolerance. Growth of Eurotia lanata was decreased by increased salt and boron, whereas that of Atriplex nuttallii was increased. Salt response of A. nuttallii ecotypes was correlated with the salinity of their natural habitats. While the ecotypes in A. nuttallii largely explained its distribution, the problem of mosaic distribution of Atriplex-Eurotia remained incompletely solved.

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