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Measuring Stem Growth Rates for Determining Age and Cohort Analysis of a Tropical Evergreen Tree
|Title:||Measuring Stem Growth Rates for Determining Age and Cohort Analysis of a Tropical Evergreen Tree|
|Issue Date:||Oct 1999|
|Publisher:||University of Hawai'i Press|
|Citation:||Gerrish G, Mueller-Dombois D. 1999. Measuring stem growth rates for determining age and cohort analysis of a tropical evergreen tree. Pac Sci 53(4): 418-429.|
|Abstract:||Metrosideros polymorpha (Myrtaceae) is the dominant canopy
tree in many Hawaiian lowland and montane rain forests. It is a shade-intolerant
species that persists throughout forest succession. Stands usually regenerate
following synchronized dieback of the canopy cohort. Like most tropical evergreen
trees, Metrosideros does not form growth rings, making determination of
tree age and stand turnover rates difficult. This study measured the annual stem
diameter growth rate for 3 yr in cohorts of six different stem size classes on
young volcanic substrates at 1100 m above sea level on the island of Hawai'i.
These side-by-side cohorts were assumed to represent a chronosequence of
stand development in early primary succession. Growth rates were used to predict
mean cohort tree age based on mean tree diameter, adjusting for variation
in growth rate during the life cycle of the trees. Mean annual growth rate was
about 2 mm yc1 for all the cohorts except the largest, which was significantly
lower. This cohort was undergoing stand dieback, with regeneration of a new
cohort and is assumed to represent the terminal stage of the cohort life cycle.
The predicted age of this cohort was about 200 years; this appears to be a reasonable
estimate of the turnover rate for cohorts in this environment. Individual
growth rates within cohorts were highly variable. Other parameters, such as
crown area and nearest neighbor distances, could not account for the variation.
Analysis indicates that the growth rate of each individual tree probably fluctuates
about the mean growth rate throughout its life. Year-to-year variation in
mean cohort growth rates was significant only for the two largest cohorts. For
these large trees, mean growth rate was negatively associated with rainfall. It is
suggested that these trees may be light limited, because solar radiation itself is
known to be negatively correlated with annual rainfall in the study area.
|Appears in Collections:||Pacific Science Volume 53, Number 4, 1999|