For Pinus densiflora, Pinus thunbergii, Abies firma, Chamaecyparis obtusa and Celtis sinensis, growth response of seedling roots to soil hardness was accessed using experimentally compacted soil in PVC tube with a variety of mechanical impedance. When no compacted soil was applied, root system of all species developed mostly downward to bottom except Pinus and Chamaecyparis, whose branch roots grew both laterally and downward. When the compacted soil segment was set beneath the seedlings, main root and branch root of Pinus and Abies could penetrate the compacted soil segment with higher impedance than Chamaecyparis and Celtis could. As the former species are known as “deep rooted species” while the latter two species are known as “shallow rooted species”, the root penetrability through the hard compacted soil was discussed in the context of general root system formation of each species.
The possibility and the approach for evaluating tree water stress by thermography were discussed. In a growth chamber, the leaf temperature and the transpiration rate of leaves of a two-year-old Zelkova trees (Zelkova serrata), which were coated with a quick-drying glue to control the transpiration rate, were examined. In the same thermal environment, there was a negative correlation between the leaf temperature and the transpiration rate. The result corresponded to the energy balance equation. Meanwhile, approaches of evaluating tree water stress by thermography were discussed based on the non-irrigated two-year-old Zelkova trees. There was a strong correlation between the transpiration rate and the difference between Td (the temperature of leaves covered with Vaseline on the abaxial side to control the transpiration rate) and Tl (the normal leaf temperature) rather than the difference between Tl and Ta (air temperature). The difference between Td and Tl is effective for evaluation of tree water stress.
In order to get quantitative information on the physiological status of field trees, we tried for 3 years simultaneous and continuous measurement of trans-root electric potential (TRP) by means of the electro-radicograph system which is developed by ourselves and sap-flow by means of the Granier type sap-flow-meters, in the field trees in a mountain area. We had accumulated ample experience on the electro-radicograph, but on the sap-flow system, we had no experience except model experiments in our laboratory. Under the very hard conditions in the mountain area, we met a number of unexpected troubles, to find finally the main obstacle was the bad insulation in the electric circuits caused by the invasion of rain water. Besides, a fundamental technical error in constructing the circuit was discovered in the most of the sap-flow meters imported. Here reported the process how to conquer the difficulties and the final solutions of the problems were.