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North Dakota University (1980)

Autecology of Atriplex Canescens (Pursh) Nutt. In Southwestern United States

Ruess, Roger W

Titre : Autecology of Atriplex Canescens (Pursh) Nutt. In Southwestern United States

Auteur : Ruess, Roger W.

Université de soutenance : North Dakota University

Grade : Doctor of Philosophy (PhD) 1980

Résumé partiel
Atriplex oanescens, a facultatively evergreen dioecious shrub inhabiting cold and warm winter deserts of western United States, was studied at four sites in the Great Basin. The species was commonly a co-dominant in communities throughout its distribution, and was frequently found with other members of the Chenopodiaceae and members of Compositae. It was found to resprout vigorously and experiments indicated that seeds from all sites germinated easily in wetted, well 3 aerated soil. The mean plant size ranged from 0.62±0.48 to 7.05±2.19 m . 3 -1 Density and cover ranged from 400 to 1.022 X 10 plants ha , and from 5.7 to 38.4% of the ground space, respectively.

Atviplex oanescens had a significant influence on the chemical and physical properties of the soil. Vegetated soils had significantly higher moisture content, organic matter, electrical conductivity, alkaline earth carbonates, nitrogen, potassium, sodium, calcium, magnesium and manganese than unvegetated soils. Both organic matter and nitrogen of unvegetated soils from the four study sites were typical of semi- arid environments, generally below 0.7 and 0.03%, respectively. Fertile islands beneath the shrub canopies provided microclimates favorable to the growth of ephemeral grass species.

Major cations in plant parts were in the order K > Ca > Mg > Na. Concentrations of these cations in plant parts decreased thus : leaves, fruits, twigs, middle and old growth. The mean of major cations in leaf tissue was 317.96±42.78 me 100 g_1 dry weight. Major anions in leaf tissue followed the order Cl > C20^ > N > P. The mean sum of major anions in leaf tissue was 116.15±15.54 me 100 g-* dry weight. High K/Na ratios were found in plant tissue, in contrast to low K/Na ratios in unvegetated soils. Leaf chloride content of Atriplex oanesoens was negatively correlated with total oxalate but positively correlated with the sum of major cations in the leaf.

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