Long-term Respiration in Relation to Growth and Maintenance Processes of the Aboveground Parts of a Hinoki Forest Tree

Over a three-year period, CO(2) exchange rates were measured continuously on the aboveground parts of a 13-year-old hinoki (Chamaecyparis obtusa (Sieb. et Zucc.) Endl.) tree in the field, using an open gas-exchange system tracking ambient temperature. The relationship between daily aerial respiratory consumption and daily gross production, which was analyzed monthly, closely resembled McCree's equation. The value of the coefficient of growth respiration ranged between 0.0 in winter and 0.16 in summer and increased with increasing monthly mean temperature. A clockwise loop was observed for monthly change in the relationship between the coefficient of growth respiration and temperature. Maintenance respiration could be formulated as a power function of aboveground dry weight. The exponent of the equation ranged from 0.3 to 1.1. A value of 1.1 in May and June, when trees were growing most actively, indicated that maintenance respiration was directly proportional to aboveground weight. In March, April, July, and August, maintenance respiration was not proportional to aboveground weight, but it was closely proportional to surface area. The exponent value exhibited seasonal change with a clockwise loop in response to monthly average temperature. During the dormant season, respiration was used only for maintenance purposes, whereas during the growing season both growth and maintenance respiration occurred. Annual growth and maintenance respiration increased with increasing tree age. The average annual contribution to total respiratory consumption was 21% for growth respiration and 79% for maintenance respiration.