© 1998 Heron Publishing—Victoria, Canada
Changes in the relationship between tree size and aboveground respiration in field-grown hinoki cypress (Chamaecyparis obtusa) trees over three years
Taketo Yokota (1, 2) and Akio Hagihara (1, 3)
1. Laboratory of Forest Ecophysiology, School of Agricultural Sciences, Nagoya University, Nagoya 464-01, Japan / 2. Global Environment Division, National Institute for Environmental Studies, Tsukuba, Ibaraki 305, Japan (tyokota@nies.go.jp) / 3. Laboratory of Ecology and Systematics, College of Science, University of the Ryukyus, Nishihara, Okinawa 903-01, Japan / Received February 18, 1997
Summary
Respiration measurements of aerial parts of 18-year-old hinoki cypress (Chamaecyparis obtusa (Sieb. et Zucc.) Endl.) trees were made under field conditions over three years to study changing relationships with tree
age between respiration and phytomass, phytomass increment, and leaf mass. The relationship between annual respiration (ra) and phytomass (wT) was approximated by a proportional function (ra = awT), where the proportional constant (a) decreased year by year. The effect of time on the relationship between annual respiration and phytomass of each sample tree
was fitted by a power function. Respiration of the tree suppressed by the canopy decreased year by year, but respiration of
the other trees increased slightly with age. The relationship between annual respiration and leaf mass was also approximated
by a generalized power function. Excluding the suppressed tree, the relationship between annual respiration (ra) and the annual increment of aboveground phytomass (ΔwT) was described by a proportional function (ra = 2.27ΔwT), where the proportional constant, 2.27, was independent of sample tree and year, indicating that about 2.3 times of the
annual aboveground phytomass increment equivalent was respired annually. For any tree, the time constant relationships between
annual respiration and leaf mass and phytomass increment for different-sized trees were similar to the corresponding time
continuum relationships. In contrast, the time continuum relationship between annual respiration and phytomass differed from
the time constant relationship, indicating that respiration of less active woody tissue contributed significantly to aboveground
respiration. Based on the relationship between tree size and annual respiration, annual aboveground stand respiration was
estimated to be 25.0, 26.9, and 25.8 Mgdm ha–1 year–1 for the three consecutive years, respectively, and the corresponding aboveground stand biomass was 60.0, 69.0, and 76.8 Mgdm ha–1.
Keywords:
phytomass, phytomass increment, size dependence, stand respiration, suppressed tree, time constant relationships, time continuum
relationships.
