A NEW TECHNIQUE FOR THE EXPERIMENTAL MANIPULATION OF TEMPERATURE IN PLANT-COMMUNITIES

1. A new technique for the experimental manipulation of temperature, i n open conditions, without the aid of cloches or screens, has been des igned, 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 a lso influenced. 3. Temperature is controlled by means of a simple elec tronic circuit which governs the operation of a solenoid valve permitt ing fluid to circulate in a fine pipework heating/cooling element plac ed at the soil surface. Both controlled elevation and controlled depre ssion of temperature can be achieved using the same design of apparatu s. 4. The new system has been used to manipulate the length of the gro wing season in a long-term experiment investigating the role of climat e and management as controls on species diversity in meadows. Specimen results from this experiment are presented. 5. It is suggested that t he temperature manipulation technique offers a new approach to the stu dy of climatic influences on plant community dynamics under field cond itions.