72 



W. R. MOLLER-STOLL AND G. LERCH 



control sets a natural temperature gradient of about i°C persisted between 

 top and bottom of the soil column. 



Results are very conspicuous, as shown in Fig. 3. 



Temperature gradients, drawn in this and the following diagrams 

 represent the average values of soil temperature reached about 30 minutes 



days 



Fig. 3. Ecological effect of vapour movement and condensation due to a temperature 

 gradient in a moist soil with a rooted plant (see Fig. i). Hatched area: temperature 

 gradient within the test soil. Base = basal soil column, top = apical soil column, 

 W.P. = wilting point. Initial soil moisture, per cent, in brackets. Vapour tension of 

 air: 45%. 



after the test had been started, and being maintained up to the end of each 

 day. Night temperatures have not been regarded, because they do not affect 

 the course of the experiments. Radiation like that in the field did not occur 

 under the experimental conditions in the greenhouse. 



The relations found in the control containers agreed with the results 

 previously published by other authors (see Veihmeyer, 1956), in particular 



