Performance of Planted Native Hardwood Trees

Technical Article No. 10.3
Performance of
Planted Native
Hardwood Trees
INTRODUCTION
SURVEYING PLANTED STANDS
Growth and management information of selected native
hardwood tree species is contained within the Tãne’s
Tree Trust Indigenous Plantation Database based on
stand assessments during a recent survey by Tãne’s Tree
Trust (TTT) as well as during an earlier survey in the
1980s by the former Forest Research Institute (Pardy et
al. 1992).
Details on tree and stand assessments are given in
Technical Article No. 10.1. Briefly, DBH (diameter at
breast height – 1.4 m above ground level) of all planted
trees within plots in native hardwood tree plantations of
known age were recorded and heights measured for a
minimum sample of 12 trees per plot. Site factors and
stand histories were collated and growth datasets from
plantation surveys analysed.
10.3 Performance of Planted Native Hardwood Trees
number of native hardwood
tree species including the beeches
(Nothofagus spp.) have been planted
over many decades throughout New
Zealand. This article provides a
summary of the height and diameter
growth of a selection of planted
native hardwood tree species
including the development of
preliminary growth models. Details
on the survey and the Tãne’s Tree
Trust database are given in Technical
Article No. 10.1 in this handbook.
Technical Handbook Section 10: Native Tree Plantations
A
GROWTH MODELS
SPECIES AND NUMBERS
PLANTED
Stand selection and analysis
Compared to the native conifers (refer to Technical
Article No. 10.2 in this Handbook), far fewer hardwood
trees have been planted and virtually none have been
planted as a long-term timber resource. Of the over
10,000 trees in the Tãne’s Tree Trust Indigenous Plantation
Database, less than 1800 are of selected native hardwood
trees including the beeches have been measured to date
in about 100 plots. Other
than for the beeches, most
hardwood trees were
within small multi-species
groves such as in urban
parks or small plantings
in established gardens.
Where possible, data used for developing the growth
models was restricted to stands that had been planted at
regular spacing and which had minimal edge effects. Trees
planted in the open or on edges of stands will have
significantly faster diameter growth due to less competition
compared to trees growing within plantations, so were
excluded from the data used to develop growth models.
Growth modelling was therefore based on a restricted
number of plots and trees that represented stands.
Sigmoidal growth curves of the Bertalanfy-Chapman
form were fitted using nonlinear regression. Models were
obtained for mean height and quadratic mean DBH.
Separate slope or asymptote parameters were
fitted for each species. For the height model, an
intercept of 0.5 m representing height at planting
was used. For the DBH model, a zero intercept
at age 4 was used, this being the average age at
which breast height is achieved by most native
hardwoods.
Height/age curves
Plot mean heights along with fitted height/age
regression curves for the eight hardwood tree
species are given in Figure 1 for the individual
species. This varied from 60-110 years of age
for the different species depending on data
available in the Indigenous Plantation Database.
Up to twenty planted hardwood tree species have been
measured but there are only eight species with sufficient
numbers across a range of ages to warrant analysis of
diameter and height growth. The most commonly planted
beeches were red beech (Nothofagus fusca) and black beech
(Nothofagus solandri) with a smaller number of silver beech
(Nothofagus menziesii). Most of the beeches were established
in stands in the south of the North Island and in the
South Island.
At 60 years after establishment where growth has been
assessed across all eight species, red beech and black
beech were the tallest with mean heights exceeding 20 m
(Figure 1). This was followed by silver beech, rewarewa
and puriri at less than 20 m mean height, taraire at 15 m
and karaka and kohekohe at 10 m.
For those species where plots have been established in
older stands, red beech exceeds 30 m mean height 110
years after planting, followed by black beech at under 30
m and silver beech leveling off at 20 m height growth.
Five other hardwood species across 3 or more sites, were
karaka (Corynocarpus laevigatus), puriri (Vitex lucens), kohekohe
(Dysoxylum spectabile), rewarewa (Knightia excelsa) and taraire
(Beilschmedia tarairi). Most of these species were planted
on North Island sites and often established as amenity
groves in urban parks.
There was a limited range of ages represented by the
eight species with only three species – red beech, black
beech and puriri – where stands over 100 years since
planting were measured. All other species had limited
number of stands across a range of ages.
2
Diameter/age curves
Diameter/age curves exceeding 100 years are
shown for the hardwood trees in Figure 2. At
60 years after planting, mean DBH ranges from
30 cm for the slowest growing species rewarewa
and silver beech to 50 cm for taraire and red
beech. The bulk of hardwood tree species have
a mean diameter around 40 cm 60 years after
planting.
Figure 1: Height/age regression curves for the native hardwood tree species
assessed from data in the TTT Indigenous Plantation Database that included
the recent nationwide survey of native plantations.
For those species with older stands, red beech
is approaching 60 cm mean diameter growth in
100 years after establishment with black beech
at 50 cm and puriri 45 cm for stands planted
for over a century.
Predicted height and diameter
growth
The predicted height and diameter of each of
the eight hardwood tree species for selected
ages up to 80 years since planting is given in
Table 2. These predictions are largely restricted
to within the limits of the data so predictions
do not extend to 80 years for the limited stands
assessed for rewarewa and taraire.
Figure 4: Mean DBH/age regression curves to age 110 years for the native
hardwood tree species based on growth data collated in the TTT Indigenous
Plantation Database.
Table 2: Predicted height and diameter for native hardwood tree species from the growth models developed for each species based
on the assessment of native plantations in the nationwide surveys.
Height (m)
Age
(years)
Red
beech
Black
beech
Silver
beech
Puriri
Karaka
10
20
40
80
5.9
10.9
18.9
28.4
5.4
9.9
17.0
25.6
4.3
7.8
13.4
20.2
5.6
9.7
15.0
19.5
Diameter (cm)
3.8
6.5
10.1
13.0
3.7
6.3
9.6
12.4
5.6
9.7
15.1
4.7
8.1
12.5
10
20
40
80
10.4
21.0
37.6
55.9
8.8
17.7
31.8
47.4
6.7
13.5
24.3
36.1
8.0
16.2
29.1
43.2
8.3
16.8
30.1
44.9
9.1
18.4
32.9
49.0
6.6
13.3
23.9
11.6
23.3
41.8
Of the selected hardwood trees assessed for height growth
in planted stands, the fastest growing hardwoods are the
beeches all of which are predicted to be between 20-30
m high 80 years after planting (Table 2). This is up to 35
cm annual height increment for red beech and 32 cm for
black beech. Faster earlier growth rates of up to 50 cm
height growth are predicted for several hardwood tree
Kohekohe Rewarewa
Taraire
species at the 10 and 20 years periods including red beech,
black beech, puriri and rewarewa.
The tallest northern hardwood is puriri predicted to be
nearly 20 m high 80 years after planting compared to
kohekohe and karaka at only 12-13 m high over the same
time period since planting.
3
The hardwood tree species with fastest predicted diameter
growth include red beech (56 cm), black beech (47 cm)
and kohekohe (49 cm) 80 years after planting (Table 2).
Mean periodic annual diameter increment for these faster
growing hardwood trees are 6-7 mm. Silver beech has
the slowest diameter growth at only 36 cm 80 years after
establishment.
The beeches are generally the fastest growing native
hardwood. Wardle (1984) indicates that red beech is the
fastest growing and silver beech is slower than the other
beeches. He has also found that the fastest growth period
for managed beech stands tend to be at the young pole
stages within the first few decades of establishment,
and particularly where stands had been thinned.
Rate of diameter growth is decreasing for many species
from the earlier periods compared to the 80 year period.
For instance, red beech is predicted to have a periodic
diameter increment at 10 and 20 years of over 10mm but
reducing to 9 mm at 40 years and 7 mm at 80 years after
planting. Similarly, kohekohe had a periodic mean annual
diameter increment of 9 mm at the 10 and 20 year period
but growth rate is predicted to decline to 8 mm increment
at 40 years and 6 mm at 80 years after planting.
Variability between individual stands across all hardwood
tree species is substantial due to the wide range of site
and climatic factors that occur between stand locations.
Many of the stands in the survey were not well managed
after planting so that growth performance particularly
within 5-10 years of planting is likely to have been seriously
compromised by weed competition.
As stands develop, there is inevitable increasing competition
between trees and therefore a decrease in diameter growth
rate as seen in the growth models developed for these
selected native hardwood trees. Virtually no stands of
native hardwood trees were thinned thus contributing to
the decreasing diameter growth rates over time.
Consequently, these average growth rates do not necessarily
reflect the true potentials of each species.
CONCLUSIONS
Mean annual diameter growth rates of 10 mm and 50
cm for height for the faster growing native hardwood
tree species within 20 years of planting is similar to those
recorded previously (e.g. Bergin and Gea 2007; Pardy et
al. 1992). However, growth rates have decreased over
time across most species. It is inevitable that tree height
growth rate will decrease with time as trees reach their
natural heights, but diameter growth can continue for
many decades but rate of growth will inevitably decrease
with increasing within stand competition.
References:
Wardle, J. 1984: The New Zealand beeches: ecology, utilisation
and management. New Zealand Forest Service, Caxton
Press, Christchurch. 447p.
Bergin, D.O.; Gea, L. 2007: Native trees – planting and
early management for wood production. New Zealand
Indigenous Tree Bulletin No. 3. New Zealand Forest
Research Institute. Revised edition. 44p.
Pardy, G. F.; Bergin, D. O.; Kimberley, M. O. 1992: Survey
of native tree plantations. Forest Research Institute Bulletin
No. 175. 24p.
Authors: David Bergin and Mark Kimberley, Scion
Contact: Tãne’s Tree Trust
Website: www.tanestrees.org.nz
The Ministry of Agriculture and Forestry does not
necessarily endorse or support the content of the
publication in any way.
ISSN 2230-3014 October 2011
4
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