沙漠研究 24-1, 25-28 (2014)
Ἃ₍◊✲ 24-1, 25 - 28 (2014)
Journal of Arid Land Studies
Journal of Arid Land Studies－ DT11 Refereed Paper －㸫DT11 Refereed Paper㸫

Tree Growth Analysis in Saline Affected Farmland in Western Australia- Tree Species and Planting Method Selection for Agro-Forestry Kenyu KONDO1), Hideki SUGANUMA1), Shin-ichi AIKAWA2), Hajime UTSUGI2),
Hiroyuki HAMANO3) and Toshinori KOJIMA*1), 4)
Abstract: Salinity problems caused by shallow underground water level (secondary salinity) widely occurs in the wheat belt area ofWestern Australia. As a countermeasure to this type of salinity problem, agro-forestry was proposed and carried out. By planting
salinity tolerant trees in saline areas, underground water is used by planted trees, and then underground water level will gradually
decline. In consequence, the secondary saline areas are expected to be prevented from their expansion by applying agro-forestry
methods. This approach will not only mitigate the salinity problem through agro-forestry, but will simultaneously fix carbon as tree
biomass by planted trees reducing carbon dioxide in the atmosphere. Then, this approach is considered as an effective
countermeasure to climate change due to carbon dioxide increment. To fulfill both aims, planted trees should have high salinity
tolerance, i.e. they should grow fast with high survival ratio in saline areas. We calculated pseudo site biomass [t ha-1] by tree
biomass and survival ratio of planted trees, and tested which tree species together with planting methods are appropriate for this type ofagro-forestry.
Key Words: Agro-forestry, Groundwater, Salinization

1. Introduction
In Western Australia, salinity problems have been
widespread because of extensive deforestation for agriculturalland development, which has caused a gradual increase ofunderground water level over the years (Short and McConnell,2000). As a result, high saline underground water level rose
gradually. When underground water levels rose near soil
surface, salinity problems occurred by salt accumulation (Coxand McFarlane, 1995). Such saline land was discarded andPlantation Site

2. Materials and Methods

K-siteK-site: (KH, KM, KL)
Water-logged site䠄altitude 300 m䠅

E-siteJ-site

Salt 0m
lakeE-site䠖Drying site
䠄altitude 330 m䠅

J-site䠖 (JH, JL)
500m

deforestation for land development was further accelerated.
To stop this negative spiral, agro-forestry, which is coexistenceof agriculture and forestry, should be carried out (Endo et al.,1988). By doing so, transpiration will be increased, andevaporation from soil surface will be decreased.
Subsequently, underground water levels will decline andsecondary salinity problems will be mitigated (Bell, 1995;
Lefory and Stirzaker, 1999). In this study, we evaluated thesurvival ratio and tree growth of three tree species together
with 8 planting methods in 6 experimental plots, and searched
for efficient combination of species, method and place.

Saline site
䠄altitude 310 m䠅

300-350 mm/y.
Semi-arid area
1Fig. 1. Wickepin (Annual precipitation; 300-350mm: E11740’,
3246’S).
* Corresponding Author: kojima@st.seikei.ac.jp, kojimaseikei@gmail.com

2.1. Research area
Our research site is located in Wickepin (11740’E; 3246’S), about 250 km south-east from Perth, the provincial capitalof Western Australia. This area is categorized as semi-aridarea. Inside this farmland, three types of afforestation
experimental sites named E-site, J-site and K-site wereestablished (Fig. 1).
E-site (11740’48.1”E, 3243’58.0”S, altitude 330 m) is
located on a hill and has deep groundwater level, so this site
was set as a control site. This area can be still used foragriculture. J-site (11740’23.4”E, 3243’14.1”S, altitude 310
㸦Received, September 14th, 2013; Accepted, December 27th, 2013㸧

3-3-1, Kichijoji-Kitamachi, Musashino, Tokyo, 180-8633, Japan
1) Department of Materials and Life Science, Seikei University

3) Japan Science and Technology Agency

2) Forestry and Forest Product Research Institute4) Centre for Ecosystem Management, School of Natural Sciences, Edith Cowan University, Australia

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Fig. 3. Summary of pseudo site biomass (6th year).
Fig. 2. Planting methods in Wickepin.

m) is located near the salt lake and has shallow ground waterlevel and is affected by salinity problem.
K-site(11740’1.2”E, 3243’14.2”S, altitude 300 m) is located near awadi and has very shallow ground water. This site isfrequently affected by water-logging. J-site and K-site cannot
be used for agriculture.
In addition, depending on altitude differences within J-site
and K-site, sub-sites named JH-site and JL-site in J-site andKH-site, KM-site and KL-site in K-site were set, since lower
altitude areas are most affected by larger environmental stress(salinity and water-logged).
2.2. Planting methods
We conducted test plantation methods in E-site, J-site andK-site in Sept. 2006 as shown on Figure 2. Seedlings ofthree tree species (Eucalyptus camaldulensis, E. sargentii andE. salubris) were planted with 8 types of planting method
inside each site. Adopted 8 types of planting methods wereas follows; control, ripping, hole with original soil, hole withkanuma soil, hole with potting mix soil, pipe with original soil,pipe with kanuma soil and pipe with potting mix soil.
Control method means just planting trees directly to the land
and was considered as the reference planting method.
Ripping and hole methods were adopted to improve soil
conditions (Barrett-Lennard, 2003).
Pipe method wasadopted to improve soil condition and also to prevent roots
area of tree seedlings from intruding saline water. The tree
density of E-site, J-site and K-site were 2858 trees ha-1, 2766
trees ha-1 and 3124 trees ha-1, respectively.
2.3. Analysis procedure
Inside each afforestation site, height and survived
individual numbers of all tree species were measured every
year from 2006. The measurement data of 18 patterns (3 tree
species × 6 sites, E, JH, JL, KH, KM and KL-site) were usedfor following analyses. We analyzed the data of surviving

samples in 2012. First, survival ratio and averaged tree
biomass [kg tree-1] of survived trees for each planting method
were calculated in 18 patterns, and used for latter described
statistical analyses. We also calculated pseudo site biomass
using the equation (1).
Bpse = Bave × Sr × D × 1/1000(1)-1; where Bpse is pseudo site biomass [t ha ]; Bave is averagebiomass [kg tree-1]; Sr is survival ratio [-]; D is tree density[tree ha-1]; 1/1000 is conversion factor from kg to metric ton.
After the pseudo site biomass calculation, we evaluated whichtree species combined with planting method were appropriate
for agro-forestry in this area.
2.4. Statistical analyses
In this research, all planting methods were also ranked bymultiple comparisons method (Bonferroni method) according
to their survival ratio, where the significant level (Į) was set as
0.05. The software used for statistical analysis was Excel
statistics Ver. 6.0 (Esumi Co. Ltd.). Tree samples less than
three surviving individuals were excluded from statisticalanalysis and expressed as “x” in the result. From thisstatistical analysis, averaged tree biomass and survival ratio wereranked based on alphabetical order (a<b<c), i.e. b is better than a.

3. Results and Discussion
3.1. Summary of pseudo site biomass
Figure 3 summarizes all the best methods in each site foreach tree species. X axis indicates each site, and Y axis
indicates tree species and Z axis indicates the calculated
pseudo site biomass. In bar chart, faint color shows thepseudo site biomass by the control method and deep colorshows pseudo site biomass by the best method in eachcondition. This figure was created to see the difference ingrowth between the best method and control, clearly. In thisfigure, E. camaldulensis had good growth performance innormal land condition such as E-site, but had bad growth27

Fig. 4. Average biomass and survival ratio of each plantation
method of E-site, E. sargentii.

Fig. 6. Average biomass and survival ratio of each plantation
method of JH-site, E. sargentii.

Fig. 5. Pseudo site biomass of E-site, E. sargentii.

Fig. 7. Pseudo site biomass of JH-site, E. sargentii.

performance in harsh environmental condition such as J-site
and K-site. And E. salubris had bad growth performance inall sites, thus this tree species was considered not suitable foragro-forestry. And E. sargentii was considered obviously thebest tree species in all the environmental condition because it had
good growth performance compared with other tree species.

respectively. In both figures, data of each method calculated
from less than three surviving individuals are marked by cross.
In E-site, hole method with potting mix soil was consideredas the most suitable method, especially in biomass growth,though statistical difference of average tree biomass was notobserved between this method and control method. Andripping method was considered to second suitable method,especially for improving survival ratio.
The same analyses results of JH-site are shown in Figures
6 and 7. Pseudo site biomass was much smaller than that ofE-site. However, pipe method with potting mix soil
improved survival ratio significantly compared to the control
method. And hole method with kanuma and original soil
were considered to improve growth of E. sargentii, though thiswas not statistically proven.
The same analyses results of KH-site are shown in Figures
8 and 9. Ripping method was considered as the most suitable
planting method in terms of survival ratio improvement, but
not so much biomass difference was observed among planting
methods excluding pipe with original and kanuma soil.
Though E. sargentii was reported to have high salinity
tolerance and high water-logging tolerance (Marcar andCrawford, 2004), this tree species showed poor growth insaline area. But in water-logging area, E. sargentii showed
good tree growth. The pseudo site biomass of KH-site was
75% of that of E-site. Thus, E. sargentii was considered as

3.2. Result of tree growth and site biomass
Since E. sargentii was revealed as the most appropriate tree
species for agro-forestry in this research area, detailed
investigated results were shown as follows. Figure 4 shows
the result of the averaged biomass and the survival ratio of E.
sargentii in E-site. X axis indicates averaged tree biomass[kg] and Y axis indicates survival ratio [%]. Dotted lines
indicate the significant rank boundaries of survival ratio
according to the statistical analysis (multiple comparisons
method, Population rate, Bonferroni). Smaller plots indicate
first to fifth year’s data and the bigger plots indicates 6th year’s
one. Plots locate in the upper right side indicate better
planting method. From this figure, we could not clearlyknow which method was greater than control method, thus
pseudo biomass calculation results were used for evaluation.
Figure 5 shows the result of pseudo site biomass of eachplanting method of E. sargentii in E-site. X axis indicatesplanting method and Y axis indicates pseudo site biomass.
Columns indicate first to sixth year’s data from left to right,

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Fig. 8. Average biomass and survival ratio of each plantation
method of KH-site, E. sargentii.

Fig. 9. Pseudo site biomass of KH-site, E. sargentii.

appropriate for planting normal land and water-logging land.
The result of the averaged biomass and the survival ratio ofE. salubris and E. camaldulensis were much lower than that ofE. sargenti. E. camaldulensis has high drought tolerance andgrows rapidly and widely observed in Australian continent(Marcar and Crawford, 2004), but had bad growth
performance in high water-logged area such as KM and KL
sites. E. salubris is native species of Wickepin, however, it
had bad growth performance in this research.
Only a few tree species survived in high saline area andwater-logged area such as JL-site and KL-site. So these sites
could not be used for agro-forestry. But slightly water-logged
area such as KH-site was considered to be used foragro-forestry with E. sargentii trees. From our study, E-site
was considered as the best site of tree growth because it had
good growth performance compared with other sites. But as
indicated by Flugge and Abadi (2006), applying agro-forestry
to agricultural land introduces large proportion of opportunity
loss, and then not so much area can be used for afforestation.

4. Conclusion
From this study in Wickepin, the most suitable tree species
for agro-forestry was considered as E. sargentii. This tree

species showed high survival ratio and fast tree growth inarable area (E-site) and water-logging areas (KH-site, KM-siteand KL-site). Efficient planting methods for E. sargentii
were considered as ripping and hole with potting mix, but evencontrol method showed relatively high survival ratio and fasttree growth of E. sargentii. Other combinations of planting
methods and tree species showed low survival ratio and slow
tree growth, thus they were not appropriate for agro-forestry.
In addition, no method showed good performance in saline
area (JH-site and JL-site), thus such areas should not be used
for agro-forestry.
In future studies, cost of each planting method andopportunity cost of agro-forestry should be compared, and thenappropriate agro-forestry methods should be investigated.
Because using arable area for agro-forestry increases
opportunity cost to the land owners and/or farmers, using otherthan control method increases initial cost of agro-forestry.
Thus, the data of survival ratio and growth rate are insufficient
for actual decision making of agro-forestry.
Acknowledgements
This work was supported by grants from the Mitsui & Co.,
Ltd. Environment Fund and from the Global Environment
Research Fund of The Ministry of the Environment(GHG-SSCP Project).

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