The Joensuu dasotrons:: A new facility for studying shoot, root, and soil processes

A new, controlled, environment facility for growing trees was built at Joensuu, Finland, between 1996 and 1998. It consists of four large rooms called dasotrons, with four large root pots in each. Each room is a separate unit, with independent control of air and soil temperature, air humidity and light. The environmental variables can be controlled to simulate conditions ranging from tropical to boreal. The controller set-points can be programmed locally or through a central control system running on a PC. The floor area and height of the rooms allows us to grow small trees (up to 3.7 m height) for several growing seasons. In each dasotron, there are four cylindrical pots with a removable upper section. There are access holes in the walls of the pots for the installation of sensors and minirhizotron tubes. Each pot has a drain, with valves, at the bottom to enable the removal of excess water or the collection of percolate samples. The operation of the facility was tested during one simulated annual growing cycle. During this test period, the dasotrons worked reliably and no systematic differences were found in the environmental conditions or in the growth of Norway spruce seedlings between the dasotrons. This new facility will enable diverse physiological and ecophysiological studies to be carried out on the responses of trees to their below- and above-ground environment.