The Composition of Wet-Heath Vegetation in Relation to Aeration of the Ground-Water and Soil: I. Field Studies of Ground-Water and Soil Aeration in Several Communities

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Abstract
The relation between botanical composition and aeration conditions in the ground-water, and in the soil above the water table, were studied on a number of transects in wet-heath vegetation together with an investigation of the composition of the gas in the intercellular spaces of Molinia coerulea roots. Highly significant regressions of the cover of Molinia coerulea, Myrica gale, Calluna vulgaris and Erica tetralix, on the concentrations of carbon dioxide and hydrogen sulphide in the ground-water were found, negative in the case of the first two species and positive in the second two. The oxygen concentration in the ground-water was very low. Even in oxygen deficient ground-water with carbon dioxide concentrations equivalent to 40% in air Molinia roots never contained less than 15% oxygen nor more than 6% carbon dioxide, which suggested that the intercellular space system provided a path for gas exchange between the roots and the atmosphere above the soil. Nevertheless there appeared to be a relation between the gas concentrations in the roots and in the soil external to them.