沙漠研究 22-1, 131 -134 (2012 )"ICAL 1 / DT X"

Journal of Arid Land Studies－Refereed Paper－An Analysis of Root Biomass in a Sapling Cultivation Experimentfor Afforestation on Salt Affected Land
Katsuhiko KUROSAWA*1), Shin-ichi AIKAWA2), Yusuke ODA1), Toshinori KOJIMA1), Satoko KAWARASAKI2),
Masahiro SAITO2), Hideki SUGANUMA1), Richard HARPER3) and Hiroyuki TANOUCHI4)
Abstract: The purpose of this study is to analyze the data of root biomasses measured in a sapling cultivation experiment reportedby Oda et al. (2009). In the experiment, Eucalyptus rudis × E. camaldulensis, E. camaldulensis and E. sargentii were cultivated in aglasshouse at Tsukuba, Japan, and those were watered with 0, 100 and 200 mmol-NaCl/L solution. The dry weight of the roots
tended to decrease with increase of NaCl concentration. The significant relationship were observed between the tree height and thedry weight of the roots (r = 0.818-0.851, p < 0.001). These suggest that the root biomass of the tree species may be able to be
estimated by the allometry equations. The biomass ratios of the root to the shoot did not increase with NaCl concentration despitethat the reduction of shoot growth is generally much greater than the reduction of root growth under saline condition. The biomass
ratio of the root to shoot of Eucalyptus saplings might not increase with NaCl concentration because same tendency was reported byMarcar (1993).
Key Words: Carbon sequestration, Root biomass, Salt affected land, Sapling cultivation experiment, Semi-arid land

1. Introduction
In recent years, risk of salinity and waterlogging has been
indicated in the wheat belt of Western Australia. The area had
been the forest area dominated by Eucalyptus species, however,those were deforested and used as farmland on a large scale(Aikawa et al., 2008). The groundwater balance wasdisrupted by the deforestation because the transpiration rates of
the crops typified by wheat were lower than those of the
Eucalyptus species and the depths of water uptake by the crops
were much shallower than those by Eucalyptus trees. The
groundwater level rose and salt was accumulated at the surface
soil as a result from the disrupted ground water balance(Kurosawa et al., 2010), and it is predicted that by 2050, up to17 million hectares (about 2.21% of Australian land) may be athigh risk (Jolly et al., 2002). The afforestation is expected tobe the most useful method to decrease the groundwater level
and to restore the groundwater balance (Kurosawa et al.,2009).
Afforestation trial has been carried out since 2004 at thesites in the wheat belt of Western Australia in our GHG-SSCP(Development of Greenhouse-gas Sink/Source Control
Technologies through Conservation and Efficient Managementof Terrestrial Ecosystems) project aiming at carbon fixation
and restoring groundwater balance by systematic afforestation(Yamada et al., 1999). The study experiments for thesystematic afforestation have been done in the afforestationsites on natural fields but also the laboratories and theglasshouses.
Oda et al. (2009) showed the results of cultivation
experiments of Eucalyptus saplings in the glasshouse under theirrigation conditions with fresh or saline water (100 or 200
mmol-NaCl/L), and they determined the best Eucalyptus
species for the afforestation to the salt-affected land. They
analyzed the planted Eucalyptus heights and total-dry weights(aboveground and underground parts) of the saplings, however,the dry weight of the roots, expecting to be affected by thewater salinity, has not been analyzed in detail. In general,
under saline condition, the reduction of shoot growth is muchgreater than the reduction of root growth (Cheeseman, 1988).
The afforestation sites of our study project are built around themarge area of the salt affected land, and it is important theeffects of the salinity stress to the underground biomass (thefixed carbon in the roots). The purpose of this study is toelucidate the change and the tendencies of the undergroundbiomass of the cultivated saplings and to consider the estimate
method of the root biomass with the size data of the above partof the planted trees by analysis the data of root biomasses
measured in the sapling cultivation experiment reported byOda et al. (2009).

* Corresponding Author: kurosawa@ejs.seikei.ac.jp
Seikei University, 3-3-1 Kichijoji-kitamachi, Musashino, Tokyo 180-8633, Japan
1) Faculty of Science and Technology, Seikei University, Japan

3) Research Institute for Sustainable Ecosystems, Murdoch University, Western Australi

2) Forestry and Forest Products Research Institute, Japan

4) Shikoku Research Center, Forestry and Forest Products Research Institute, Japan2. Materials and Methods

3. Results and Discussion
Figure 1 shows mean dry weight of the roots and theresults of the comparison test of the roots weight classified thedata group by the NaCl concentrations of the irrigated water.
Mean the dry weight of the roots decreased with theconcentrations of the NaCl concentrations. Mean dry weightof the sapling roots grown with fresh water were 14.96 (E.
rudis × E. camaldulensis), 12.26 (E. camaldulensis) and 5.22(E. sargentii) g, respectively. Mean dry weights of the rootsof E. rudis × E. camaledulensis and E. camaldulensis weresignificantly higher (p < 0.01) than that of E. sargentii under
the cultivation condition with fresh water and 100
mmol-NaCl/L solution. Under the cultivation condition with
200 mmol-NaCl/L solution, mean dry weight of the roots waslower than those under the any other conditions, and there wasmean dry weight of the roots [g]aE. rudis x E. camaldulensis
a20.00E. camaldulensis
E. sargentii

15.00
a10.00abb5.00

aaa0.00
0 mmol-NaCl/L

100 mmol-NaCl/L

200 mmol-NaCl/LFig. 1. Mean dry weights of the roots of the cultivated saplings. The
different letters show the significant differences analyzed by
Tukey-Kramer test in the interspecies conditions.
100(a) E. rudis x E. camaldulensis

10y = 0.00002649 x1.832
r = 0.851
p < 0.001

10.1

dry weight of the roots [g]The cultivation experiments were carried out in a
glasshouse of Forestry and Forest Production ResearchInstitute at Tsukuba City from May 2007 to January orFebruary 2008. The tree species and the cultivation periods
were Eucalyptus rudis × E. camaldulensis, E. camaldulensis
and E. sargentii, respectively (Oda et al., 2009). The trees
were germinated and cultivated in plastic pipes (1m height and10cm diameter) filled with Kanuma soil (the general gardening
soil in Japan), and nets were put on the bottom of the allcultivation pipes for gravitational drainage of the surplus water.
After the germination, all plants were grown under wet
condition by irrigation with fresh water for about one month.
After that, those were watered for 2 weeks interval with 2.0 Lof fresh water (0 mmol-NaCl/L) or saline water (100 or 200mmol-NaCl/L). The 100 and 200 mmol-NaCl/L wereequivalent to 12.64 dS/m (moderate salt tolerant) and 25.28
dS/m (highly salt tolerant), respectively (Marcar and Crawford,2004). The supplied water volume was sufficient to saturate
the soil layer. After the cultivation period, all the saplings
were measured the tree height, and then those were harvested
for the measurement of those dry weights. The harvested
saplings were separated as aboveground and underground parts.
The separated parts were dried out 60˚C condition inlaboratory ovens for a few days. After the procedure, the dryweights of the sapling parts were measured in the laboratory.
The dry weight data of the parts were sorted by the items of theparts, species and cultivation conditions for statistical analyzes.
Turkey-Kramer test (Yanai, 2004) was adopted to the analyzes
for elucidation of significant difference between each datagroups. Sminov test (Ichihara, 1990) was adopted for thedetection of outlier in a data group.

25.00

100(b) E. camaldulensis

10y = 0.0002924 x1.521
r = 0.818
p < 0.001

10.1100(c) E. sargentii

1010.1100

y = 0.0006967 x1.353
r = 0.848
p < 0.001
1000
tree height [mm]10000

Fig. 2. Allometry relationships between the dry weight of the roots ofthe cultivated saplings and the tree heights.

not significant difference among mean dry weights of the rootsof the each species. These suggest that the roots of all thecultivated Eucalyptus under the salinity tolerant conditions
were inhibited their own growth by the salinity stress, and thedry weight data of the roots were not so different as the result.
Figure 2 shows the relations between the final tree heights
and the dry weight of the roots after the harvesting of thesaplings. The dry weight of the roots increased with the treeheight. The equations in the figures were the results of theregression analysis determined by the least square method, andthe significant correlations were detected between the treeheights and the dry weight of the roots in all the cases (r =0.818-0.851, p < 0.001). These mean that the dry weight of
the underground part of the cultivated saplings could be unified
by the allometry relationships during the cultivation period
despite the difference of NaCl concentration of the irrigatedwater and the biomass of the roots can be estimated by theallometry relations and the data of the tree height.

0 mmol-NaCl/L

100 mmol-NaCl/L

200 mmol-NaCl/L

0.80

y = 0.00001291 x + 0.3508(a) E. rudis
x E. camaldulensis r = 0.060
0.60
p > 0.05
0.40

Biomass ratio of the root to shoot [-]

0.20
0.00
8.00

(b) E. camaldulensis

6.00
y = -0.001526 x + 1.975
r = 0.175
p > 0.05

4.00
2.00
0.00
0.80

y = -0.00002437 x + 0.3257
r = 0.050
p > 0.05(c) E. sargentii

0.60
0.40
0.20
0.00

0500

1000
tree height [mm]

1500

2000

Fig. 3. The relationship between biomass ratio of the root to shoot andthe tree height of the saplings. The data surrounded bydotted line were the significant outliers detected by Sminov test.
0 mmol-NaCl/L

100 mmol-NaCl/L

200 mmol-NaCl/L

0.80 (a) E. rudis

y = 0.00001291 x + 0.3508
x E. camaldulensis r = 0.060
p > 0.05

0.60
0.40
0.20
Biomass ratio of the root to shoot [-]Figure 3 shows the relationships between the biomass ratioof the root to shoot (the dry weight ratio of the undergroundand the aboveground parts) and the tree heights of the saplings,
and Figure 4 shows the biomass ratios of the root to shoot andthe tree heights after the Sminov test. The data surrounded by
the dotted line in Figure 3 were the significant outliers detectedby Sminov test. The equations in the Figures 3 and 4 showed
the results of the regression analysis determined by the leastsquare method. The slopes of the regression equations inFigure 4 were near 0, and the significant relationships were notdetected in the analyses. The biomass ratios of the root toshoot of each tree species were ranged from 0.18 to 0.50 (E.
rudis × E. camaldulensis), from 0.39 to 0.70 (E. camaldulensis)
and from 0.14 to 0.45 (E. sargentii), respectively. The
minimum and maximum values of the biomass ratios of theroot to shoot of E. camaledulensis tend to be higher than thoseof the other tree species. This means that the biomass ratiosof the root to shoot tend to be depended on the tree species.
Table 1 shows the average of the biomass ratios of the root toshoot, the standard deviations (S.D.) and the coefficients ofvariation (C.V.) on the tree species and NaCl concentrations.
Cheesman (1988) showed that the reduction of shoot growth ismuch greater than the reduction of root growth, however, in
this study, the biomass ratios of the root to shoot under fresh
water condition on each tree species were similar to thoseunder saline water conditions. The biomass ratios of the root
to shoot ratios did not increase with the NaCl concentrations.
Marcar (1993) showed the results of the experiments of 4
types of Eucalyptus saplings (including E. camaldulensis)
cultivation in a glasshouse, and the significant differences was
not detected between the biomass ratio of the root to shootunder control (fresh water cultivation) condition and thoseunder saline water condition. There were same experimental
points between this study and Marcar (1993), Ecucalyptus
saplings (under 1 year old) and cultivation experiment in aglasshouse. In a journal about arboriculture, Harris (1992)
showed that the biomass ratios of the root to shoot is 5 or 6 formost trees under normal natural condition, and the biomass
ratios of the root to shoot in this study tend to be higher thanthose in Harris (1992). These indicate that the biomass ratioof the root to shoot of young Eucalyptus saplings underlaboratory experimental condition may not tend to be changed
by salinity stress.

0.00
0.80 (b) E. camaldulensis
0.600.40
y = -0.001526 x + 1.975
r = 0.175
p > 0.05

0.20
0.00
0.80(c) E. sargentii

0.60

y = 0.00002923 x + 0.2832
r = 0.007
p > 0.05

0.40
0.20

4. Conclusion

0.00
0The data of the cultivation experiment of Eucalyptus
saplings, especially the dry weight data of the root and shoot,were analyzed in this study, and the following were mainfindings:

500

1000
tree height [mm]

1500

2000

Fig. 4. The relationship between biomass ratio of the root to shoot andthe tree heights of the saplings. (after Smirnov test for outliers)

Table 1. Mean biomass ratio of the root to shoot, the standard
deviations and the coefficients of variation on the tree
species and NaCl concentration.
E. rudis x
E. camaldulensis

E. camaldulensis

E. sargentii

average
S.D.
C.V.

0.35
0.08
0.23

0.53
0.08
0.14

0.31
0.05
0.16

100 mmol-NaCl/L average
S.D.
C.V.
200 mmol-NaCl/L average
S.D.
C.V.

0.34
0.09
0.25
0.33
0.07
0.23

0.52
0.11
0.21
0.57
0.09
0.16

0.33
0.13
0.39
0.30
0.10
0.31

0 mmol-NaCl/L(a) There were significant relationships between the dry weightof the cultivated roots and the tree height after theharvesting of the saplings.
(b) Biomass ratio of the root to shoot did not increase withNaCl concentration of the irrigated water despite that thereduction of shoot growth is generally much greater than
the reduction of root growth.
(c) The trends of the biomass ratio of the root to shoot weredepended on the tree species.
These show that the allometry relationships can be utilized
for the estimate of the underground biomass of the saplings.
The biomass ratio of the root to shoot could be utilized too,however, the tendency of the ratio depending on tree species
should be considered.

Acknowledgement
This work was conducted with support from MEXT
KAKENHI 22254002 (Grant-in-Aid for Scientific ResearchA), the Mitsui & Co., Ltd. Environmental Fund, the Global
Environment Research Fund of the Ministry of Environment(GHG-SSCP project) and the Japan Science and Technology
Agency (Core Research for Evolutional Science andTechnology). The helpful opinions of researchers andstudents in our laboratory are gratefully acknowledged.

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