78
SEASONA.L DEVELOPMENT OF A YOUNG PLANTATION Of
EUCAlYPTUS NITENS
D. J. FREDERICK
School of Forest Resources, North Carolina State University,
Box 8002, Raleigh, North Carolina 27695, United States
H. A. I. MADGWICK
Forest Research Institute, New Zealand Forest Service,
Private Bag, Rotorua, New Zealand
M. F. JURGENSEN
Department of Forestry, Michigan Technological University,
Houghton, Michigan 49931, United States
and G. R. OLIVER
Forest Research Institute, New Zealand Forest Service,
Private Bag, Rotorua, New Zealand
(Received for publication 27 November 1985; revision 10 March 1986)
ABSTRACT
A 5-year-old plantation of Eucalyptus. nitens Maid. grew over 4 m in height
and added basal area of 4.6 m2/ha in 12 months. Production of dry matter in
the above-ground portion of the stand averaged 36 tonnes/ha/annum over a
2-year period with over 70% in bole material. The season of sampling was
unimportant in determining the biomass of stand components since foliage
production was closely linked with leaf litterfall. Branch and stem mass
increased with time as woody litterfall was small compared with production.
Nutrient concentrations in living tissue tended to decrease with increased tree
size and often varied among seasons. Although season of sampling affected
estimates of stand nutrient content, no simple pattern of change was observed.
Calorific values of foliage and live branches were highest in summer or autumn
but seasonal differences in stem components were not statistically significant.
Keywords: biomass; litterfall; nutrients; energy; Eucalyptus nitens.
INTROOUCTION
Numerous studies of forest biomass and nutrient content have been published in
recent years. Few of these consider effects of season of sampling. Canopy weight of
pines changes systematically throughout the year (Madgwick 1983) but few data are
available for hardwoods (Langkamp et al. 1982; Satoo & Madgwick 1982). A knowledge of seasonal changes is important both for theoretical studies of dry matter
production and for applied studies of the implications of whole-tree harvesting for
such uses as energy.
We wished to determine whether season of sampling influenced biomass, energy,
or nutrient contents of Eucalyptus in the central North Island of New Zealand.
New Zealand Journal of Fo•restry Science 16(1): 78-86 (1986)
Frederick et al. -
Seasonal development of Eucalyptus nitem
79
MATERIALS AND METHODS
Sample Stand
A 5-year-old E. nitens plantation located in Cpt 905 of Kaingaroa. State Forest was
chosen for study. The site is flat and is at an altitude of 550 m. The soil is derived from
Taupo ash overlain with Kaingaroa silty sand (Frederick et· al. 1984). Previous cover
was a Pinus nigra Arn. plantation which had been clearfelled. Site preparation included
ripping, double disdng, and V-blading into beds 75 to 90 cm high at 3-m intervals.
Eucalyptus nitem was planted in 1975 at a 3 X 2-m spacing using 1/0 bare-rooted
stock grown at the Forest Research Institute nursery from seed collected from
Nimmitabel, New South Wales. Seedlings were planted on top of the beds.
Field Sampling
During October 1980, when the plantation was 5 years old, a permanent sample
plot 20 X 20 m (0.04 ha) was randomly located for sampling stand structure and
stocking. In October 1980 and at three successive 3-month intervals ail trees in the
permanent plot were measured for diameter at breast height (dbh). A final measure·
ment was made in October 1982 shortly before the stand was clearfei!ed to establish
a coppice study. At each measurement date a stratified random sample of nine trees
was selected based on dbh. The first four such selections were taken from the stand
around the permanent plot and the fifth from within the permanent plot. Methods for
handling sample trees followed those detailed earlier (Frederick et al. 1984, 1985).
In addition the height of the lowest leaf-bearing branch on the stem was recorded.
For each tree the dry weight of leaves, twigs, live branches, dead branches, stem wood,
and stem bark were determined. No reproductive structures were found on any sample
tree. All foliage was of the adult form. Stem diameters were measured, but no sample
trees taken, 1 year after the start of observations.
Stand weights were independently estimated at each sampling date using the
basal area ratio method (Madgwick 1981). Accurate error estimates for calculated
stand -.:omponent weights cannot be obtained with "small" numbers of sample trees
using the basal area ratio method. However, replicated sampling of known populations
suggests that such errors are likely to be about 12% of the calculated stand weights
(Madgwick 1981). This level of error was also indicated using estimates of stand
weight based on logarithmic regressions of weight on size.
In December 1980, ten 1-m2 litter traps were located randomly within the permanent
plot. Litterfall was collected at 4- to 6-week intervals for the next 13 months. Litterfall
was separated into leaves, woody material, and miscellaneous litter prior to oven-drying
at 70°C
Laboratory Analyses
Chemical analyses were made on the first four tree samplings and litterfall. Stem
wood samples were chipped and all tree samples were ground to pass 2-mm and
1-mm-mesh sieves for wood and foliage components respectively. Samples of rree
material and litterfall were sent to Analytical Services Limited for chemical analysis.
Nitrogen was determined using Kjeldahl digestion with selenium catalyst followed by
colorimetry. After wet digestion with nitric and perchloric acid, potassium and calcium
80
New Zealand Journal o.f Forestry Science 16(1)
were determined by flame emission; magnesium, manganese, zinc, a:nd copper by
atomic absorption; phosphorus by colorimetry, and sulphur turbidimetrically. Calorific
values were determined using a bomb calorimeter (Leith 1965).
The relationships between nutrient concentrations, tree dbh, and season o.f
sampling were examined using covariance analysis. Sampling times were represented
by dummy variables.
RESULTS
At the beginning of observations the E. nitens stand had attained a top height o.f
12.5 m and contained 72 tonnes ~ry
matter/ha in above-ground parts of trees
(Table 1). Substantial growth occurred in height, basal area, volume, and stem weight
in each season of the year .from October 1980 to July 1981. Top height increased
almost 4 m, basal area 3.7 m 2 /ha, and stem weight by 25 tonnes/ha. A further 0.9 m 2
basal area/ha was added between July and October 1981. Neither leaf material nor
live branch weight showed any clear seasonal trend, with changes between sampling
dates being masked by sampling variation. Foliage mean weight was 6.9 tonnes/ha
and live branch weight 12.6 tonnes/ha. Over the same period the weight of dead
branches on the trees doubled .from 5 to 10 tonnes/ha.
TABLE 1-Stand characteristics and dry matter content of a stand of Eucalyptus nitens
sampled at five dates
Oct
1980
Jan
1981
Apr
1981
July
1981
Oct
19'82.
Stocking (stems/ha)
Basal area (m2Jha)
1675
1675
1675
1675
1675
2.3.4
2.6.7
2.7.1
32.5
Mean diameter (cm)
Average height (m)
13.0
2.5.4
13.5
13.9
14.0
15.2.
11.1
12.5
13.7
14.0
15.6
Top height (m)
12..5
14.4
15.9
16.3>
18.4
Height to lowest live branch (m)
2.7
3.4
5.0
5.0
7.2
Volume under bark (m3Jha)
Dry weight (tonnes /ha)
102
12.6
140
155
2.09
6.3
11.3
7.0
15.9
6.4
10.4
8.0
12.9
5.3
6.3
7.8
10.6
9.4
14.4
0.0
64.8
90.9
Trees
Leaves
Live branches
Dead branches
7.2
Fruits
Stem wood
0.0
0.0
42..6
50.8
0.0
53.7
Stem bark
6.2
7.1
7.8
9.2
10.8
71.6
87.0
86.1
105.5
132.6
Tree above-ground
0.0
Frederick et al. -
Seasonal development of Eucalyptus nitens
81
Litterfall collections commenced in January 1981 and showed a marked seasonal
trend with leaves making up almost 90% of the total litterfall over 13 months of
observation (Fig. 1). Maximum leaf fall occurred in summer but in late winter leaf
fall was negligible. Annual leaf litterfall amounted to 77% of mean foliage weight
on the stand, suggesting an average leaf life of between 1 and 2 years. Rate of branch
[]FOLIAGE
):'
D WOODY
<(
0
MATERIAL
"E
.!!}
"
(')
f-
I
C)
w
s:
0
s
M
0
DATE (MONTH)
FIG. !-Seasonal pattern of litterfall in a 5-year-old E. nitens
plantation.
fall was similar for all months except for November when over one-quarter of total
branch fall occurred. Total litterfall over the first 12 months of observation was 5.3
and 0.7 tonnes/ha of leaves and woody material, respectively (Table 2). The base of
the live crown rose 2.3 m from October 1980 to July 1981. Most branches dying
within this period remained on the trees. Branch litterfall represented only about 10%
of increment of dead branches on the trees.
TABLE 2-Annual dry matter and nutrient content of litterfall in a Eucalyptus nitens
plantation, January 1981-January 1982, and the weight and nutrient content of
the forest floor <n.d.
not determined)
Component
Litterfall
Leaves
Woody
Forest floor
Dry
matter
(t/hal
N
P
K
S
Ca
--------(kg/ha)
Mg
Mn
Cu
Zn
0.06
n.d.
11.5
4.1
32.3
5.0
4.5
3.4
2.7
0.2
0.9
0.4
4.0
0.8
0.3
0.03
0.01
121
8
13
n.d.
181
11
n.d.
n.d.
5.3
46.7
0.7
11.7
0.01
82
New Zealand Journal of Forestry Science 16(1)
Total nutrient content of the stand was closely related to dry weight (Table 3).
Thus the content of most nutrients in the stand increased from the first to the fourth
sampling. This trend was clearest for dead branches,. which doubled in total dry weight
over the period, and for elements such as calcium which were relatively more important
in the woody material. Weights of nutrients in foliage were greatest for the fourth
sampling when estimated dry weight was also highest.
TABLE. 3-Total nutrient content of a stand of Eucalyptus nitens (kg/ha)
N
p
K
s
ea
Mg
Mn
October
Leaves
Twigs
Branches
Live
Dead
Cu
Zn
- (g/ha)-
<kg/ha)
7.1
4.5
6.4
28
2.6
35
2.1
3.0
16
30
7.1
2.6
13
94
216
563
99
34
7.3
4.2
39
39
9.1
4.0
37
43
14
9
1.7
18
2.8
7
2.4
2.3
23
0.5
61
5.2
22
2.4
11.9
82
8.5
8.7
36.7
23.9
102
85
65
80
Stem
Bark
Wood
Total
January
Leaves
Twigs
Branches
Live
Dead
Stem
Bark
Wood
Total
35
27.9
103
241
3.5
15.3
36.6
6.8
52
8.7
46
1.8
25
6.5
1.1
100
19
9.5
2.4
26
1.8
11
39
53
6.1
2.9
79
75
8.9
6.2
4.9
3.5
49
16
160
111
2.5
47
105
35
72
365
125
273
233
309
9.5
44.8
7.1
2.5
25.7
23
122
3.0
20.4
43.0
8.3
13.7
30.4
714
43
12
9'.7
1.2
31
14
1.6
5.2
0.8
24
5
100
26
38
3.7
3.3
43
97
5.6
7.4
3.1
5.2
23
37
116
160
2.6
15.2
35.7
124
35
345
10.0
9.8
42.6
8.7
3.4
26.3
15
83
81
185
274
760
10.4
2.6
49
31
9.7
6.8
35
3.2
1.6
14
118
56
4.0
4.9
45
117
4.7
3.0
5.7
36
57
90
144
3.7
18.6
44.1
154
10.7
44
440
11.8
11.1
4.3
32.4
17
110
270
212
64
244
97
13
30
11
4.7
0.9
24
57
233
107
7.2
10
1.3
28
20
3.4
1.1
25
271
39
47
188
April
Leaves
Twigs
Branches
Live
Dead
Stem
Bark
Wood
Total
14
28
2.8
46
70
120
263
13.9
29.5
273
120
20
8.8
2.4
21
25
20
3.1
32
0.8
12
33
2.9
17.5
35.5
47
139
8.1
July
Leaves
Twigs
Branches
Live
Dead
Stem
Bark
Wood
Total
78
296
48
299
8.7
48.7
81
702
Frederick et al. -
Seasonal development of Eucalyptus nitens
83
Concentrations of nitrogen, phosphorus, potassium, sulphur, magnesium, and
copper within each living component all tended to decrease with increased dbh at
each sampling (Table 4). The effect of sampling date on the slope of the relationship
between nutrient concentrations was not statistically significant. Nutrient concentrations
varied among sampling occasions but trends with time were not consistent.
TABLE 4-The effects of dbh and time of sampling on nutrient concentrations in tissues
of Eucalyptus nitens. For dbh, - means a significant negative correlation
with nutrient concentration. For time, the symbol indicates direction of effect.
One symbol means significant at the 5'% level, double symbols at the 1% level
assuming all tests independent. E'ffects of sampling da.te are relative to October
1980 (ns = not significant)
Nutrient
Variable
N
d.b.h.
January
April
July
p
K
s
ea
ns
ns
ns
ns
ns
+
++
ns
+
++
+
ns
ns
ns
+
ns
ns
+
ns
ns
ns
+
++
ns
ns
Mg
Cu
ns
ns
ns
+
++
ns
ns
ns
+
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
Zn
ns
ns
ns
ns
ns
Live branches
d.b.h.
January
+
April
+
++
+
July
ns
ns
ns
ns
++
ns
ns
ns
'15
+
ns
ns
ns
+
ns
ns
ns
ns
ns
ns
ns
+
ns
ns
ns
ns
ns
ns
++
ns
ns
+
ns
ns
+
ns
Dead branches
d.b.h.
January
April
July
ns
Stem bark
d.b.h.
January
April
July
ns
ns
ns
ns
+
H
+
ns
ns
ns
ns
ns
Stem wood
d.b.h.
January
April
July
ns
ns
ns
ns
ns
ns
ns
+
+
++
+
ns
ns
ns
ns
ns
ns
ns
84
New Zealand Journal of Forestry Science 16(1)
Calorific values of leaves and live branches were significantly different among
sample dates with minimum values in October (Table 5). Effect of sampling date
on calorific values in stem components was not statistically significant, though for stem
bark there was a consistent decline in value throughout the period of observation.
TABLE 5-Calorific values (kJ/g) of components of a Eucalyptus nitens stand
Component
s.e.
Sampling date
October
January
April
July
Leaves
22.2
23.0
22.7
22.5
0.09
Live branches
Dead branches
19.2
19.5
19.7
19.4
0.08
18.8
19.1
18.9
19.2
0.17
Stem bark
18.0
19.4
18.0
17.9
19.5
17.6
19.3
0.13
Stem wood
19.3
0.09
DISCUSSION
Eucalyptus nitens is noted for its fast early growth and in Australia has been found
out-produce E. regnans F. Muell. up to 15 years of age on a number of E. regnans
sites (Pederick 1979). Lack of an adequate growth and yield model for E. nitens
prevents an accurate assessment of relative productivity of our study plot but growth
in height and basal area was less than that found for a range of E. regnans stands
also growing in the central North Island of New Zealand (Frederick et a'l. 1985).
Differences in over-all performance could be due to seed source of the E. nitens which
has proved of poor to average performance in provenance trials (Pederick 1979;
Franklin 1980). At age 5 the Nimmitabel provenance in Pederick's study had a
dominant height close to that of our stand, while the best-producing provenances
were 15% taller and dominant trees had 60% more volume than the Nimmitabel
provenance. In contrast, seed collected from the area including our E. regnans sample
plots has performed better than average in provenance trials (Griffin et a,z. 1982;
Wilcox 1982). Differences in basal area growth could partly reflect the lower stocking
of the B. nitens stand. Mean annual increment at age 5 years was 14 tonnes/ha compared with 20 tonnes/ha in a close-spaced, 4-year-old stand which contained almost
four times as many stems per hectare (Madgwick et al. 1981). Foliage mass on the
present stand was lower than that on either E. regnans plantations or the close-spaced
E. nitens.
to
1
Litterfall patterns in the B. nitens stand were similar to those found in a wide
range of Bucalyp,tus species with a summer maximum and a winter minimum (Baker
1983; Frederick et al. 1985 ). Lack of a discernible seasonal trend in total foliage mass
on the stand suggests that leaf production and abscission follow similar seasonal trends.
This hypothesis would be extremely difficult to test on a stand basis since conventional
biomass sampling would require a large number of sample trees, while direct observation of leaf initiation and development on a sufficient scale to determine precise
relationships would appear infeasible given the size of the trees.
Frederick et al. -
Seasonal development of Eucalyptus nitens
85
Nutrient pools in woody tissue were strongly dependent on total dry weight so
that time trends were dominated by the accumulating woody biomass in the stand.
Detecting seasonal changes in nutrient pools in foliage and live branch components
does not appear amenable to conventional biomass sampling because of variability
among individual trees. Even when foliage nutrients are monitored a:t monthly intervals,
and maturation state of individual leaves is taken into account, foliage nutrients in
Eucalyptus spp. tend to vary considerably (Bell & Ward 1984) and may be related
to rainfall (Schonau 1983 ). In our stand maturation state of the leaves will have varied
throughout the canopy especially during the season of maximum leaf fall and production.
Variability from whole-tree sampling was more important than season of sampling
m the determination of biomass and nutrient content of canopy components of this
E. nitens stand. If our findings are confirmed in other environments the omission of
information on sampling date in studies of eucalypt stand weights would be of little
importance. Data on nutrient contents of other stands are required to determine
whether there is a consistent pattern of seasonal change in this genus.
Over the 2-year period in which dry-matter measurements were made, the aboveground portion of the stand increased by 61 tonnes/ha or 30 tonnes/ha/annum. In
addition, litter production was 6 tonnes/ha/annum giving a current annual increment
of 36 tonnes/ha/annum. This annual increment is comparable to that found in dosespaced Pinus radiata D. Don also growing in the central North Island of New Zealand
(Madgwick & Oliver 1985).
ACKNOWLEDGMENT'S
This research was made possib:e with the aid of Senior Research Fellowships for
D. J. Frederick and M.. F. Jurgensen. Completion of the manuscript was expedited through
a Forest Service Study Award to H. A. I. M.adgwick, and the hospitality of North Carolina
State University.
We thank all the organisations and individuals whose help made this research possible.
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Martin Jurgensen