1981 Volume 19 Issue 1 Pages 17-23
An assimilation chamber whose inside temperature could be controlled was made to measure the photo-synthesis, respiration and transpiration of forest trees in situ. The switching power supply system was used in thermomodule circuit, which reduces the weight of the apparatus and make it easier to handle even in a primeval forest on steep mountain.
Deviation from the desired temperature during a 10-hour run was ±0.2°C under a constant thermal load (100 cal/min) . The settling time for the step input of temperature (28°C→23°C) was within 3 minutes and that of the load (100 cal/min→0 cal/min) was within half a minute.
The chamber was used to measure the photo-synthesis of intact sun leaves in a natural beech stand. The inside temperature closely followed the ambient air temperature with only a deviation of ±0.3°C during the day with fluctuating irradiations of sunlight.
