The Water Relations of Certain Heath Plants with Reference to their Ecological Amplitude: III. Experimental Studies: General Conclusions

Abstract

The effects of waterlogging and soil drought on the water relations of three ericaceous heath plants, Calluna vulgaris, Erica tetralix and E. cinerea were examined experimentally. In the field these plants are characteristic of intermediate, wet and dry soil moisture regimes respectively. Erica cinerea is the most sensitive to waterlogging showing a reduction in transpiration and relative turgidity which leads to the death of the plant; Calluna shows less inhibition while Erica tetralix is virtually unaffected by a period of waterlogging. In dry soils Erica tetralix shows a reduction in transpiration but a lethal reduction in relative turgidity whereas Erica cinerca shows little reduction to either transpiration or relative turgidity. Calluna shows a large reduction in both transpiration and relative turgidity but appears to be able to tolerate this. The findings of others papers in this series are brought together and summarized. Calluna vulgaris shows the best germination and establishment over a wide range of soil types and moisture regimes. Erica tetralix is able to compete with Calluna on the wetter parts of the latter''s range on account of its indifference to waterlogging and Erica cinerea can compete on the drier areas as it is less inhibited by soil drought.