沙漠研究 22-1, 223 -226 (2012 )"ICAL 1 / DT X"

Journal of Arid Land Studies－Refereed Paper－

Selection of Afforestation Methods for Eucalyptus sargentii
as a Countermeasure to Climate Change and Salinity Problem-A Case Study of Wheat Belt Area in Western AustraliaToshinori KOJIMA*1) 2), Yuji WAKAMORI1), Ken KOIZUMI1), Katsuhiko KUROSAWA1),
Masahiro SAITO3) and Hideki SUGANUMA1)
Abstract: There exist serious problems such as increase of underground water level and secondary salinity problem in wheat belt insouthern Western Australia. So we here propose agro-forestry, which is a remedy of water logging and salinity problems by planting
trees in a part of the farmland. Planted trees use surplus underground water by transpiration from the deep soil. At the same time,
planted trees capture CO2 from atmosphere, so we attempt to use this agro-forestry method as a global warming countermeasure.
To investigate agro-forestry effect on water logging and global warming, some afforestation sites were established in the semi-arid
region (Wickepin) in Western Australia. We tested three types of field modification technologies, two types of soil modification
technologies and three types of tree species. From statistical analysis on survival ratio and tree growth, we selected the suitablecombination of modification technology and tree species in various salinity and water logging intensity.
Key Words: Afforestation, Salinity, Semi-arid area, Statistical analysis, Water logging

1. Introduction
In Australia, farmland has been cultivated by cutting large
scale of Eucalyptus native forest from European immigration.
Transpiration water amount of the crop land is lower than thatof the native forest, and the crops can’t extend their roots deepin the soil compared to the trees, and then all the rainwater was
not used by crops. Thus surplus water was supplied into thedeeper underground water, and underground water level has
gradually risen with long time. In addition, the surplus water
dissolved salt naturally contained in the soil and plenty of salt
has been gathered into the underground water, which became
saline water. In consequence, shallow underground waterlevel brought water logging which also brought soil salinity
and salt accumulation on soil surface since saline capillarywater reached soil surface and evaporated. This problem has
been widely observed in the decades in Australia andagricultural production was gradually declined because of thisproblem. Part of crop land became desolate area.
So agro-forestry has been carried out as a countermeasureagainst these problems (Endo et al., 1998; Marcar andCrawford, 2004). Furthermore, afforestation also has role offixing CO2 and planted trees will be used for producing
biomass energy. Then our team established agro-forestry trial
area at a farmland of Wickepin in Western Australia andvarious trials were conducted to develop afforestation
technologies (Kojima and Egashira, 2011). In the presentstudy, we will report the experimental results for improving
soil environment of root zone to increase survival ratio of
seedlings and to accelerate their growth. .

2. Materials and Methods
2.1. Research area
Our agro-forestry trial area at Wickepin locates at 200 km
south-east from Perth, the provincial capital of Western
Australia. In the trial area, there are several test sites. But inthis study, we will report the results of three sites; E-site（S32°43’58”, E 117°40’48.1”, elevation 330 m), J-site (S32°43’14.1”, E 117°40’23.4” , elevation 310 m) and K-site (S32° 43’ 14.2”, E 117° 40'1.2” , elevation 300 m). E-site has
drought stress but can be still used for wheat cultivation.
J-site has strong secondary salinity problems becouse of its
location (next to a salt lake) and can not be used for wheat
cultivation. This J-site consists of sub-sites named J-high(JH) and J-low (JL) according to their difference in altitude.
K-site has strong water-logging stress with a little secondary
salinity problem because of its location near a water channel
and can not be used wheat cultivation. This site also consistsof three sub-sites named K-high (KH), K-middle (KM) andK-low (KL).

* Corresponding Author: kojima@st.seikei.ac.jp
3-3-1, Kichijoji-kitamachi, Musashino, Tokyo, 180-8633, Japan
1) Department of Materials and Life Science, Faculty of Science and Technologies, Seikei University
2) Centre for Ecosystem Management, School of Natural Sciences, Edith Cowan University, Australia

3) Forestry and Forest Product Research Institute, Japan

2.2. Plantation methods of seedlings
We tested eight types of plantation methods in all sites.
First method was no modification. This was just planting
seedlings on original soil directly and it was assumed control
method. It was called “Control’’. Second method was thatsoil surface layer was scratched like ditch with about 60 cm
depth by heavy equipment and seedlings are planted along theditch.
This method also adopted mounding.
Bothtreatments may improve root growth and air permeability(Marcar and Crawford, 2004). This method was called“Ripping”. Third method was that vertical holes with 1 m
depth and 10 cm diameter were drilled up by boring machine,and original soil was put back, and then tree seedlings wereplanted in the hole. This method also adopted mounding andthis method may avoid water-logging. This method wascalled “Hole’s original”. Fourth and fifth methods weresimilarly Hole’s original but used two additional soils.
Additional soils were Kanuma-soil and potting mix.
Kanuma-soil was commonly used soil for gardening in Japanand improved water retention characteristics and waterpermeability. Potting mix was leaf mold used for gardening
in Australia. These methods were called Hole’s Kanuma andHole’s potting mix, respectively. Sixth method was that PVC(poly-vinyl chloride) pipe with 9 cm diameter and 1.2 m length
was inserted in the same hole of “Hole method” drilled byboring machine, and original soil was put back inside the pipe.
This method was called “Pipe’s original”. Seventh and eighth
methods were called “Pipe’s Kanuma” and “Pipe’s pottingmix” that were used the same pipes of “Pipe’s original” butused the same above mentioned additional soils instead oforiginal soil.
We planted three species of seedlings with above eight
methods respectively. Seedlings are Eucalyptus camaldulensis,
E. salubris and E. sargentii. In this study we focused E.
sargentii which grows around naturally in Western Australia
and has salt tolerance and has a characteristic of expandingroots sideways.
2.3. Tree height measurement and biomass estimation
First we have conducted measurements of tree height ofplanted seedlings twice a year since September 2006. And
we also recorded survival ratio. Some died samples at earlystage were replaced by new seedlings but were excluded fromour analysis.
Second we cut down some samples in September 2010 andmade an allometric equation. The allometric equation wasused for dry-biomass weight (Y) estimation from tree height (X).
And we conducted regression analysis by a power function as Y
= bXa. Using this estimated biomass data and planting density,
we also calculated biomass density in Mg ha-1 unit.

2.4. Statistical analysis of tree growth
We conducted statistical analysis called multiple
comparison (α = 0.05, Bonferroni) of average tree height andsurvival ratio to the data of September 2010. Statistical orderwith significant difference is given as a < b < c. Then we
made scatter plots giving survival ratios for Y-axis and averagetree height or average biomass for X-axis, reflecting the resultsof statistical analysis. From this result, we determined whichplantation method is suitable for in each site.

3. Results and Discussion
Figure 1 shows a scatter plot and statistical analysis resultsfor KH-site with average tree height on the X-axis and survival
ratio on the Y-axis. Continued four plots represent annual
data from the first to fourth year. The biggest plots indicate
the data of the fourth (last) year. In this figure, statisticalanalysis was applied to the data of fourth year. Longitudinaldotted lines represent significant difference in tree height andlateral dotted lines represent significant difference in survival
ratio. The digits next to the fourth year plots represent thesurvival numbers of planted trees.
In KH-site, Ripping and Pipe’s potting mix gave the bestresults for survival ratios, while all data of growth werestatistically indistinguishable except Pipe’s Kanuma and Pipe’soriginal. Thus from survival ratio significance, Ripping was
judged as the best planting method for KH-site
On the other hand, in Figure 2 with biomass on the X-axis
instead of tree height, Hole’s original shows statisticallysignificant high value of biomass. From survival ratio
evaluation, Ripping and Pipe’s potting mix were better thanControl, and from growth analysis evaluation, Hole’s original
was better than Control. Then we compared these results byusing biomass density in Mg ha-1. According to this analysis,
Ripping, Hole’s original and Control gave 9.0, 8.2 and 7.5 Mg
ha-1, respectively. So planting Eucalyptus sargentii in areas
which have water-logging problem like KH-site, Ripping wasrevealed the best planting method.
Similarly, results of KL-site are shown in Figures 3 and 4.
In KL-site, Ripping was the best planting method of all theevaluation indices which were survival ratio, average treeheight, biomass and biomass density.
The results for the E. sargentii planted in the other sites arealso summarized as follows using similar methodology.
In KM-site, there was no significant difference of survival
ratio and growth, statistically.
In E-site, comparatively high survival ratio was found.
Among the various methods, Ripping and Hole’s potting mix
were revealed the best planting method.
In JH-site, there was no significant difference in survival
ratio and growth.

100975Survival Ratio (%)

10257b◆ Control■ Ripping▲ Hole's Kanuma▲ Hole's original△ Hole's potting mix● Pipe's Kanuma● Pipe's original〇 Pipe's Potting mix

ab58650425aababaabb050

0100150

200250

Average Tree height (cm)Fig. 1. Tree height and survival ratio of planted trees on KH-site.
100

92575

b10Survival Ratio (%)

758650ab4a25aabababb00

2000

1000

3000

4000

5000

Biomass (g/Tree)
Fig. 2. Tree biomass and survival ratio of planted trees on KH-site.

10024Survival Ratio (%)

754b9ab2350a3 3250aabbaabb0050100150200250

Average Tree hight (cm)Fig. 3. Tree height and survival ratio of planted trees on KL-site.

6000

10024Survival ratio (%)

75b9ab42350

3 3a25a000aababbb

1000

2000

3000

4000

5000

6000

Biomass (g/Tree)
Fig. 4. Tree biomass and survival ratio of planted trees on KL-site.
Table 1. Estimated total biomass density for all methods of all sites.
Site nameEJH
JL
KH
KMKL

Biomass(Mg ha-1)
2.22
0.49
0.61
2.89
1.53
1.02

In JL-site, significant difference in growth was foundand Pipe’s potting mix was the best planting method while
all methods gave indistinguishable results of survival ratio.
From these results,when the farmland which can be used
for wheat cultivation, such as E-site, was used forafforestation sites, Ripping or Hole’s potting mix was
considered to give better results compared to Control.
When the land with salinity problems, such as J-site, wasused for afforestation sites, Pipe’s potting mix was
considered to give better results compared to Control.
When the land with water-logging, such as K-site, was usedfor afforestation sites, Ripping was considered to give better
results compared to Control.
Finally the estimated results of total biomass density ofall sites are shown on Table 1. According to Table 1, theyield of KH-site was found remarkably high. It wasconsidered that there was almost no stress for E. sargentii inKH-site because KH-site which located the higher elevation
had less water-logging effects than the other K-sites. In
addition, E. sargentii has the characteristic of expanding its
roots horizontally. Considering the difference in biomassamount among the various methods in various sites, byselecting the most suitable methods according to thecharacteristics of each site, higher yield was expected inwater-logging site for afforestation using E. sargentii.

4. Conclusion
When the farmland which can be used for wheat
cultivation, such as E-site, was used for afforestation sites,
Ripping or Hole’s potting mix was considered to give better
results compared to Control. When the land with salinity
problems, such as J-site, was used for afforestation sites,
Pipe’s potting mix was considered to give better resultscompared to Control.
And When the land withwater-logging, such as K-site, was used for afforestationsites, Ripping was considered to give better resultscompared to Control.
Considering the difference in biomass amount among
the various methods in various sites, by selecting the mostsuitable methods according to the characteristics of each site,higher yield was expected in water-logging site forafforestation using E. sargentii.
Acknowledgement
This work was conducted under the support of theMitsui & Co., Ltd. Environment Fund, Grant-in-Aid for
Scientific Research (22254002) of Japan Society for thePromotion of Science and the Global Environment Research
Fund of The Ministry of Environment of Japan (GHG-SSCPproject).

References
Endo I., Abe Y., Kojima T. (1998): Desert Engineering.
Morikita publishing Co. Ltd, Tokyo, p182-187
Kojima T., Egashira Y. (2011): Arid Land Afforestation
against Global Warming. Corona publishing Co. Ltd.,Tokyo, 222p.
Marcar N., Crawford D. (2004): Trees for Saline landscapes,
RIRDC Publication Number 03/108 p1-3