The power equation
r =
azb is often used to represent the sunny crown profile of conifers, where
r is the crown radius (m) at distance
z (m) from the tree apex, and
a and
b are parameters. When parameter
b is invariant between trees, parameter
a is the only independent variable that determines the sunny crown profile. Assuming that parameter
b is invariant between trees, this study derived a sunny crown profile equation for Hinoki cypress (
Chamaecyparis obtuse ENDL.) based on the power equation from the relationship between parameter
a and the annual height increment HI (m/year):
a =
c HI
d where
c and
d are parameters. First, we derived the relationship
a =
c HI
d. Next, we evaluated the efficacy of the equation
r =
c HI
dzb at representing the sunny crown profile of Hinoki cypress. Data were obtained from 112 trees in six pure stands of even-aged Hinoki cypress. The fit of the equation
a =
c HI
d to the data was good. The equation
r =
c HI
dzb made more precise predictions than the equation
r =
azb assumed that each of parameters
a and
b is common to all trees. The values of parameters
b,
c, and
d estimated from the sample trees were 0.686, 0.401, and -0.299, respectively. The integration of the sunny crown profile equation
r =
c HI
dzb with a tree growth model, including the total height growth and the sunny crown length estimations, enables prediction of the sunny crown profile and its change with growth for Hinoki cypress.
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