THE OBJECTIVE EVALUATION METHOD OF THE TREE VIGOR WITH THE STEM TEMPERATURE

THE DEVELOPMENT OF A PLANT VIGOR MEASURING INSTRUMENT

Abstract

The sap temperature changes by heat exchanged between the tree and its external environment, for example, the air temp., the insolation, and the wind, when the sap is rising in the stem from the root. The good growth tree exchanges less heat from its external world than the bad one, because its amount of flow is more and its bigger crown mitigates the thermal environment of the stem and the root. The relatiive change of sap temp., which is the change of the sap temp. passing through a fixed length stem divided by the air temp. that is the forecast maximum change, is related to the tree vigor judged with the four-ranking method by the Science and Technology Agency.