1. Growth Impact of Simulated Insect Spring
Defoliation on Young Eucalyptus bosistoana
Huimin Lin, Dr. Tara Murray & Prof. Euan Mason
School of Forestry, University of Canterbury, Christchurch, New Zealand
• Location: Trial was located in a 5-year old E.
bosistoana plantation in a dryland farm near Seddon,
Marlborough.
• Method: Artificial defoliation was used to simulate
chewing damage from 2 major Eucalyptus insect
defoliators.
• Treatments: control (n=64), moderate (n=39) and
severe (n=39) defoliation.
• Defoliation time: October 2015.
• Measurements: Stem diameter at 1m and tree height
were measured monthly after defoliation and 1
month before defoliation.
• In March 2016 (about 5 months after defoliation),
most trees were largely recovered (figure a & b), but
there are exceptions (figure c).
• Eucalyptus bosistoana can produce 1st class naturally
ground durable heartwood.
• It’s drought tolerant which can provide alternative
sustainable land use options for dryland areas.
Moderate
defoliation
Severe
defoliation
Control
a. b. c.
Acknowledgements: Assoc Prof Luis Apiolaza for data analysis; volunteers for
defoliation: Niger Sultana, Tingdong Guo‎, Fei Guo‎‎, Jennifer Schori‎, Yukako Nakamura,
Jiaping Hu, Meili Duan, Aiqing Wang, Han Bao and Zicheng Yi.
Contact: huimin.lin@pg.canterbury.ac.nz
Results
2.75
3.00
3.25
3.50
3.75
week(-4) week(0) week(04) week(08) week(12) week(16) week(20)
Stemdiameterat1m(cm)
Defoliation severity
C
M
S
0.00
0.05
0.10
0.15
week(0) week(04) week(08) week(12) week(16) week(20)
Growthrateofstemdiameterat1m(cm/month)
Defoliation severity
C
M
S
2.2
2.3
2.4
2.5
week(-4) week(0) week(04) week(08)week(12) week(16)week(20)
Treeheight(m)
Defoliation severity
C
M
S
0.000
0.025
0.050
0.075
0.100
week(0) week(04) week(08) week(12) week(16) week(20)
Growthrateoftreeheight(m/month)
Defoliation severity
C
M
S
Oct Nov Dec Jan Feb Mar
Oct Nov Dec Jan Feb Mar
Sep Oct Nov Dec Jan Feb Mar
Sep Oct Nov Dec Jan Feb Mar
Stemdiameterat1m(cm)Treeheight(m)
Growrateofstemdiameterat1m(cm/month)Growrateoftreeheight(m/month)
*Spring defoliation was conducted in October
Control Moderate
defoliation
Severe
defoliation
Interaction effect of defoliation level and time on tree height
2.6
Treeheight(m)
time time time
Stemdiameterat1m(cm)
Control Moderate
defoliation
Severe
defoliation
time time time
3.8
3.6
3.4
3.2
3.0
2.8
Interaction effect of defoliation level and time on stem diameter
• Stem diameter at 1m and tree height of 3 treatments were not significantly different at the start of the experiment.
• In March 2016 (about 5 months after defoliation), stem diameter of severe defoliated treatment trees were significantly lower than
the control treatment trees (P = 0.0194), while tree height of control treatment was significantly higher than severe defoliation
treatment, but not moderate defoliation treatment.
• Linear mixed effects models were build to study the relationship between the growth of stem diameter/tree height and defoliation
severity. The interaction between time and defoliation severity is significant, indicating that there is significant difference for growth
rate between control and defoliated treatments. However, the impact of defoliation on height growth was not as strong as stem
growth.
• Late summer defoliation impact and further measurements on these trees growth will be continued.
2.3
2.2
2.4
2.5
mean±SE mean±SE
mean±SE mean±SE