A New Technique for the Experimental Manipulation of Temperature in Plant Communities

1. A new technique for the experimental manipulation of temperature, in open conditions, without the aid of cloches or screens, has been designed, built and tested. 2. The apparatus permits controlled elevation or depression of temperature relative to ambient to be achieved while tracking normal diel temperature variation. The vertical profile is also influenced. 3. Temperature is controlled by means of a simple electronic circuit which governs the operation of a solenoid valve permitting fluid to circulate in a fine pipework heating/cooling element placed at the soil surface. Both controlled elevation and controlled depression of temperature can be achieved using the same design of apparatus. 4. The new system has been used to manipulate the length of the growing season in a long-term experiment investigating the role of climate and management as controls on species diversity in meadows. Specimen results from this experiment are presented. 5. It is suggested that the temperature manipulation technique offers a new approach to the study of climatic influences on plant community dynamics under field conditions.