the diameter at breast height (dbh) measurements made on trees with a dbh greater or
equal to 9 cm. Between 5 and 10 dominant or codominant trees were then randomly
selected in a 1,964-m
2 plot with the same centre as the inventory plot. Each tree was
then felled and disks taken at stump height (0.15 cm), 0.60, 1.00, breast height
(1.3 m), 3.00 m and every 2 m thereafter until the top of the tree. The disks were
sanded, and ring widths measured along four radii for the lower disks lower than
3.00 m and on two opposing radii on the other disks. For a complete description of
sampling design, see Schneider et al. (2013) or Franceschini and Schneider (2014).
Only the rings produced after 1970 were kept for the analysis, leading to a total of
1,082,125 ring widths. Data characteristics are available in Table 1.
3 Quantifying Stem Form
Through the years, several methods have been used to study the effect of different
variables on the shape of a tree stem. Of these, three methods that have been used in
recent years will be presented: the vertical profile of radial growth, stem taper
equations and allometric exponents.
3.1 Ring Width Models
The diameter of a stem at a given point is the sum of the yearly radial increments at
that height. Generally, the yearly increment is largest at crown base and close to the
stump (e.g. see Larson 1963 for early observations in the first half of the twentieth
century; Deleuze and Houllier 2002; Cortini et al. 2013). Differences in radial
growth rates within a tree can lead to important biases when constructing longterm ring chronologies, if sampling of dead trees is not carried out at the same height
as those of the living trees (Autin et al. 2015).
Table 1 Mean tree, stand and
environmental characteristics
for the sampled plots with
balsam fir (standard deviations
in parentheses)
Variable
Mean
Diameter at breast height (cm)
22.1 (4.7)
Total tree height (m)
16.7 (2.9)
Tree age (years)
72.9 (22.4)
Altitude (m)
421 (181)
Stand density (n/ha)
1,303 (520)
Stand basal area (m
2
/ha)
33.0 (9.8)
Mean summer temperature (
C)
15.2 (1.1)
Mean winter temperature (
C)
À14.1 (2.3)
Total summer precipitation (mm)
1,061 (109)
Mean wind speed (m/s)
3.6 (1.8)
Mean wind standard deviation (m/s)
2.0 (0.9)
298
R. Schneider
equal to 9 cm. Between 5 and 10 dominant or codominant trees were then randomly
selected in a 1,964-m
2 plot with the same centre as the inventory plot. Each tree was
then felled and disks taken at stump height (0.15 cm), 0.60, 1.00, breast height
(1.3 m), 3.00 m and every 2 m thereafter until the top of the tree. The disks were
sanded, and ring widths measured along four radii for the lower disks lower than
3.00 m and on two opposing radii on the other disks. For a complete description of
sampling design, see Schneider et al. (2013) or Franceschini and Schneider (2014).
Only the rings produced after 1970 were kept for the analysis, leading to a total of
1,082,125 ring widths. Data characteristics are available in Table 1.
3 Quantifying Stem Form
Through the years, several methods have been used to study the effect of different
variables on the shape of a tree stem. Of these, three methods that have been used in
recent years will be presented: the vertical profile of radial growth, stem taper
equations and allometric exponents.
3.1 Ring Width Models
The diameter of a stem at a given point is the sum of the yearly radial increments at
that height. Generally, the yearly increment is largest at crown base and close to the
stump (e.g. see Larson 1963 for early observations in the first half of the twentieth
century; Deleuze and Houllier 2002; Cortini et al. 2013). Differences in radial
growth rates within a tree can lead to important biases when constructing longterm ring chronologies, if sampling of dead trees is not carried out at the same height
as those of the living trees (Autin et al. 2015).
Table 1 Mean tree, stand and
environmental characteristics
for the sampled plots with
balsam fir (standard deviations
in parentheses)
Variable
Mean
Diameter at breast height (cm)
22.1 (4.7)
Total tree height (m)
16.7 (2.9)
Tree age (years)
72.9 (22.4)
Altitude (m)
421 (181)
Stand density (n/ha)
1,303 (520)
Stand basal area (m
2
/ha)
33.0 (9.8)
Mean summer temperature (
C)
15.2 (1.1)
Mean winter temperature (
C)
À14.1 (2.3)
Total summer precipitation (mm)
1,061 (109)
Mean wind speed (m/s)
3.6 (1.8)
Mean wind standard deviation (m/s)
2.0 (0.9)
298
R. Schneider