「森林総合研究所研究報告」（Bulletin of FFPRI）Vol.19-No.1（No.453）89-104 March 2020

論89

文（Original article）
137

Cs concentrations in the pollen of sugi (Cryptomeria japonica var.
japonica) over 5 years following the 2011 Fukushima Daiichi
Nuclear Power Station accident in Fukushima Prefecture
1)

2)

3)

4)

Yoshiyuki KIYONO *, Akio AKAMA , Tatsuro KANAZASHI , Koji SHICHI ,5)
6)
5)
Teiji KONDO , Hiroshi HOSHI , Noritsugu KURAMOTO ,7)
8)
Yoshitake FUJISAWA and Shigeo KURAMOTO
Abstract
We aimed to estimate the amount of radiocesium re-dispersed by sugi (Cryptomeria japonica var. japonica) pollen
release accurately based on measurements of sugi male flowers before pollen release. We measured the biomass andcesium-137 (137Cs) concentrations in male flowers and sugi pollen in November (shortly after pollen maturity), and in
the following February (shortly before pollen release), in forests impacted by the 2011 Fukushima Daiichi Nuclear
Power Station accident. Pollen accounted for ca. ⅓ of male flower biomass and the 137Cs concentrations were notsignificantly different between male flowers and pollen in November in the Koriyama sugi forest. The regression
relationship between male flower and pollen 137Cs concentrations was used to calculate pollen 137Cs concentrations forevery November–December period in the years 2011–2015 at 21 localities in Fukushima Prefecture. The sugi pollen
137
Cs concentration declined year on year. The concentration in the spring of 2016 was ca. 8% of the concentration inspring 2012. The calculated 137Cs Tag (aggregated transfer factor) for the transmission of 137Cs from the environment topollen was 0.0203 m2 dry kg–1 in February 2012 and 0.00168 m2 dry kg–1 in February 2016, based on data available in
the MEXT 137Cs deposition quantity distribution map.
Key words: Deposition, distribution map, male flower, phenology, radiocesium, Tag (aggregated transfer factor), yearlyvariation in pollen production

1. Introduction

in mid to late October (Forestry Agency 2007) and becomesRadiocesium is contained in flowers (Barišić et al. 1992,

nutritionally independent in male flowers by November.

Molzahn and Assmann-Werthmüller 1993). After the 2011

Subsequently, male flowers enter dormancy and mature after thisTEPCO Fukushima Daiichi Nuclear Power Station (FDNPS)

dormancy is broken by winter cold. Pollen is usually released

accident, airborne pollen (Bunzl et al. 1993) was identified

from mid to late February in Fukushima Prefecture (Ministry

as a dispersal vector of radiocesium (Ministry of Agricultureof the Environment 2018). Pollen production fluctuates greatly

Forestry and Fisheries [MAFF] 2011, Tokuma Shoten 2011, TV

from year to year (Yokoyama and Kanazashi 1999, Kajimoto

Asahi 2011). Igarashi et al. (2019) also reported fungal sporeand Fukushima 2015); the ability to predict pollen production is

involvement in the re-suspension of cesium-137 ( Cs) during

an important element of measures used to combat sugi-pollinosis

summer. Many sugi (Cryptomeria japonica var. japonica) trees(hay fever). Male flowers are usually observed in monitored

grow in Fukushima Prefecture, which is of concern because

forests from November to December (Teiten-sugi-rin, National

their pollen can be inhaled by humans within the vicinity of theForestry Extension Association in Japan 2017, Ministry of thetrees. The internal radiation dosage that results from breathing

Environment 2016), when they are readily observable in tree

inhalation has been calculated for people living in Tokyo (MAFFcrowns. The quantity of male flowers that will release pollen

2011, Tsuruoka et al. 2015). Male sugi flowers are formed onin the following spring was estimated during the monitoring

current-year leaves in the June–August period. Pollen matures

procedure. However, the relationship between the observed

137

Received 13 August 2019, Accepted 18 December 20191) Department of Plant Ecology, Forestry and Forest Products Research Institute (FFPRI)
2) Center for Forest Restoration and Radioecology, FFPRI
3) Former FFPRI
4) Shikoku Research Center, FFPRI
5) Forest Tree Breeding Center, FFPRI
6) Former Forest Tree Breeding Center, FFPRI
7) Kagoshima University8) Department of Forest Vegetation, FFPRI* Department of Plant Ecology, FFPRI, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687 JAPAN; e-mail: kiono@ffpri.affrc.go.jp

90

KIYONO, Y. et al.

male flower mass and the 137Cs content of these flowers when the

2012–2015 provided by the Forestry Agency research projectpollen is released in the following spring remains unclear. MAFF

grant ‘Understanding actual condition of radioactive substance(2011) assumed that pollen mass accounts for ca. half of thein forest’). We also estimated the 137Cs Tag (aggregated transfer

Cs concentrations

factor) for the transmission of 137Cs from the environment to sugi

observed male flower biomass, and that the137

of male flowers and pollen were identical. However, there arepollen.

no data to verify these assumptions. Quantification of pollen/
male flower biomass and 137Cs concentration ratios will enableaccurate calculation of the re-dispersal of 137Cs mass by pollen
based on measurements of male flowers prior to pollen release.
We conducted measurements of sugi male flowers in a forest
located in Koriyama, Fukushima Prefecture on six occasions(November 2011, February and November 2012, February
2013, November 2015, February 2016) (Fig. 1, Δ). This forest
was exposed to radiation released in the FDNPS accident.
Subsequently, we examined the relationships among biomass
and 137Cs concentrations in male flowers and mature pollen
in November. We estimated the 137Cs concentration of sugi
pollen dispersed in the spring in the 2012–2016 period basedon these relationships and the measured 137Cs concentrations inmale flowers collected in the sugi forests (Fig. 1, ●) at diverse
locations in Fukushima Prefecture, in the November–December
period in each year between 2011 and 2015 (2011 data provided
by the Forestry and Forest Products Research Institute (FFPRI)
research project grant ‘Methodology development for estimating

Fig. 1. Locations of sugi (Cryptomeria japonica var. japonica)
forests that were surveyed.
△, location (Koriyama) at which the cesium-137 (137Cs)
concentrations and biomasses of sugi male flower parts
were measured. ●, locations at which yearly changes insugi male flower 137Cs concentrations were measured.

radiocesium concentration in sugi pollen, #201128’; data for
Table 1. Measured biomasses and 137Cs concentrations in sugi (Cryptomeria japonica var. japonica) male flower parts.

2011.11−1

2012.2

2012.112013.2

2016.112017.2ab

Pollen/male flower biomass ratio (g g )

-

-

-

-

0.32 ± 0.05

Male flower biomass (g 100 male flowers−1)−1
Pollen biomass (g 100 male flowers )1−1
Male flower husk biomass (g 100 male flowers )

-

-

-

-

1.756
0.561
1.196

1.180 ± 0.181
0.561 ± 0.074
0.620 ± 0.149

565
1430

1792 ± 487
686 ± 292a
3256 ± 1256a-

51-

59 ± 52cc
53 ± 55c
64 ± 48A
40 ± 27b

137

Cs concentration(Bq dry kg−1)

Male flower
Pollen1

Male flower husk
Current-year leafaA

231 ± 85b-

A

275 ± 86aAb

284 ± 210379 ± 310b
A
349 ± 227a

0.48 ± 0.06

A

137

Ratio of Cs concentration in February
137
pollen/ Cs concentration in previous
November male flowers

Cryptomeria japonica var. japonica clone

1.21

Combined

1.19

1.04

Soma 1,
Soma 5,
Soma 9,Soma 1,
Soma 1,
Soma 1,
Soma 9,Futaba 4,
Iwaki 1,
Soma 9,Iwaki 1,
Futaba 4,
Iwaki 1,
Iwaki 7,
Futaba 4,
Iwaki 7,
Iwaki 2,
Minamiaizu Minamiaizu Iwaki 7, andIwaki 1,
Yama 1, andYama 1. Iwaki 7, and7, and7, andMinamiaizu
Ken-misho Ken-misho Combined
Yama 1
5
137
for CsDifferent lower case superscript letters identify significant pairwise differences between means in rows (t-test; P < 0.05). Different
upper case letters identify significant pairwise differences between means in columns (paired t-test; P < 0.05).
1, including anther.

森林総合研究所研究報告 第 19 巻 1 号, 2020

137

Cs concentrations in the pollen of Cryptomeria

2. Materials and methods
2.1 Biomass and

Cs concentrations in sugi male ﬂowers

137

91

measured by the Japan Frozen Foods Inspection Corporation(JFFIC); measurements of the remaining samples were obtained

and pollen in November and the following February

by the FFPRI. Measured values were standardized to zero

Male flowers and current-year leaves were collected inmoisture content based on our measurements of moisture content

November 2011 from several flowering plus-tree clones of sugiin the samples. We selected three medium-sized male flowers as(Table 1) that had been planted in the progeny test demonstration

samples from each clone in November 2016 and February 2017,

forest [established in 1969, Kawakami (2000)] of the Fukushima

and dissected out the pollen and male flower husk with needles

Prefectural Forestry Research Centre (Koriyama City, Fig. 1,

under a stereoscopic microscope (SMZ 800-1; Nikon). Anthers△). Here, we define sugi leaves as young stems and branches

were included with the male flower husks. In November, a large

covered with live needle-like leaves (Kiyono and Akama 2016).

amount of resin was observed in the resin paths of the husks, andUnder this definition, some sugi leaves grow into stems or

the removed pollen grains were often smeared with this resin.

branches following the development of xylem. Male flowers

In February, the amount of resin was reduced and pollen/male

were collected in February 2012 from six clones: Soma 5, Soma

flower husk separation was relatively easy. The masses of the9, Futaba 4, Iwaki 2, Yama 1, and Minamiaizu 5 (Table 1). Sun-

pollen and male flower husks were measured using an electronic

exposed lower branches of trees on the forest edge ca. 0.6 m

balance (XS 205 DU; Mettler Toledo; max weight, 81/220 g, d =long bearing leaves and male flowers were collected (as on all

0.01 mg/0.1 mg) and then standardized to zero moisture content.

subsequent occasions) and transferred to water-filled plastic

The numbers of male flowers were not counted in November

crates for separate collection of pollen and other male flower

2011, February 2012, November 2012, or February 2013. The

organs (referred to hereafter as “male flower husk”) (Fig. 2). Malemeasured values for pollen, male flower husks, and male flower

flowers and current leaves were collected in November 2012 frombiomasses per male flower obtained in November 2016 werefour clones, Soma 1, Iwaki 1, Iwaki 7, and Minamiaizu 7, andused as proxy data for November 2011 and November 2012.

from a non-clone sugi tree grown from a seedling (Ken-misho,

Likewise, measurements made in February 2017 were used as

referred to hereafter as a “clone temporarily”). In February 2013,

proxy data for February 2012 and February 2013. Since thepollen, male flower husks, and current-year leaves were collected

pollen biomasses and 137Cs concentrations were not different

from the same five clones via the procedure used in February

between November and the following February, the 137Cs

2012. In November 2016 and February 2017, male flowers wereconcentrations of male flower husks in November 2011 andcollected from six clones: Soma 1, Soma 9, Futaba 4, Iwaki 1,

November 2012 were calculated from the 137Cs concentrations

Iwaki 7 and Yama 1 (Table 1). In February 2017, the branches ofeach clone were cut and stood in water for collection of pollen,
male flower husks, and current-year leaves. We counted thenumber of male flower husks on each clone on this occasion.
We sampled six sugi clones in February 2012, five during thesecond procedure (November 2012/February 2013), and six
during the third procedure (November 2016/February 2017).
None of the clones bloomed well on all three occasions, likely areflection of the annual fluctuation in sugi male flower formationand genetic variability. However three clones bloomed to thesame extent on the first and third occasions, and on the second
and third occasions. The provenances of the 10 clones were as
follows: 7 from Hamadori, 1 from Nakadori, and 2 from Aizu,
i.e., primarily from Hamadori, but spread throughout Fukushima
Prefecture. The clones selected were considered representativeof the sugi trees impacted by the FDNPS accident.
Collected and dried male flowers, pollen, male flower husks,
and current-year leaves of each clone were packed separately in
U-8 containers. The 137Cs concentrations were measured using
a high-purity germanium (HPGe) coaxial detector system at the
FFPRI. In 2011 and 2016, the male flowers from multiple clones
were combined into single samples. The 137Cs concentrations inthe samples prepared in November 2011 and February 2012 wereBulletin of FFPRI, Vol.19, No.1, 2020

Fig. 2. Procedure for collecting Cryptomeria japonica var.
japonica pollen from branches held standing inwater-filled crates.
Branches were separately wrapped in bags of glassine
paper (used to reduce static electricity) (18 × 38 cm,
Rizo, Inc.; http://www.rizo.co.jp/crossingbag.html). The
bag openings were closed with cotton and copper wire,
after which the branches were transferred to water-filledcrates in a laboratory held at ca. 23°C during working
hours (8:30–17:15) on weekdays. The water level inthe crates was maintained over time. Most pollen was
released into the bags within 3 weeks.

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KIYONO, Y. et al.

3. Resultsof male flowers (measured in each November) and pollen(measured in each following February), and the pollen/male

3.1 Biomass and

Cs concentrations in sugi male ﬂowers

137

flower biomass ratio measured in November 2016. The maleand pollen in each November and each following

flower 137Cs concentration in February 2013 was estimated fromFebruary

Cs concentrations at that

Biomass per male flower decreased between each November

time and (ii) the pollen/male flower biomass ratio measured inand each following February (Fig. 3a). Since we assumed the

February 2017. Using these calculated values, the pollen, malepollen status to be unchanged, the male flower husk biomass

flower husk, and male flower 137Cs contents (product of biomass

therefore decreased. The ratio of pollen biomass to male flower

Cs concentration) were estimated for November 2011,

biomass increased as male flowers matured: 0.32 ± 0.05 in(i) the pollen and male flower husk

and

137

137

February and November 2012, and February 2013.

November and 0.48 ± 0.06 in February (Table 1) (P < 0.0001,
n = 6). The male flower 137Cs concentration was higher in

2.2 Estimating theCs concentration in sugi pollen

137

each February than in each previous November (Fig. 3b) due

released in spring during the period 2012‒2016

to the increase in 137Cs concentration in the male flower husk.

FFPRI and MAFF collected male sugi flowers in the

The increase in the period November 2011–February 2012

November–December period of every year between 2011 (132was especially large. The quantities of 137Cs per male flower

localities in sugi forests) and 2015 (21 localities) in Fukushima

and per male flower husk increased in the period November

137

Cs concentrations in the tissues

2011–February 2012 (Fig. 3c), but were lower in the periods(Akama et al. 2013, Akama et al. 2017). Leaves have also been

November 2012–February 2013 and November 2016–February

Prefecture, and measured thecollected since 2012. In our work, we selected 21 localities

2017. We found no significant difference in the current-year leaf

(Fig. 1, ●) in which the survey continued for 5 years, to identify

137

inter-annual changes in Cs concentrations. Sugi trees from

(Fig. 3d, Table 1).

137

Cs concentration between November 2012 and February 2013
Both the concentrations and quantities of 137Cs decreased

which samples were collected were not necessarily those(Fig. 3b,c; Table 1) year on year. The decline was rapid immediately

sampled in the previous years.
The 21 localities in our study had 14 granite and otherplutonic rock types, 3 sedimentary rocks, 2 metamorphic rocks,

after the accident. Similar trends in 137Cs concentration occurredin the current-year leaves (Fig. 3d, Table 1).

1 igneous rock type, and 1 Jurassic accretionary complex

The 137Cs concentrations were not significantly different(Geological Survey of Japan 2014). The pollen/male flower

between (a) November 2012 male flowers and current-year137

Cs concentration ratio obtained in the Fukushima Prefectural

leaves and (b) February 2013 pollen (paired t-tests, P = 0.152–

Forestry Research Centre forest was used in the calculations to

0.898, n = 5, Fig. 3b,d).

estimate the pollen 137Cs concentrations over 5 years. A few male

The pollen/male flower 137Cs concentration ratios were high inflowers dropped during the period from male flower maturity to

November and low in the following February (Fig. 4), reflecting

pollen release, but we did not consider the implications of thisthe increase in 137Cs concentration in male flower husks fromphenomenon.

November through the following February. The difference in
137

2.3 Transmission of

Cs to sugi pollen

Cs concentration ratio between November and the following

February was smaller in later years. The pollen/November male137

Cs deposition data after July 2, 2011 in the 21 localities

flower 137Cs concentration ratio was ca. 1.2 in the first andCs deposition

second years after the FDNPS accident and close to 1.0 in thein the region (Ministry of Education, Culture, Sports, Science

fifth year (Table 1). Using the duration of time after the accident

and Technology, MEXT 2018). The mean value between theas a parameter, we constructed a regression model to calculate

upper and lower limits of a given deposition class constituted

the pollen/November male flower 137Cs concentration ratio:

The

137

(Fig. 1) were obtained from a distribution map of137

the deposition value and was used in the analyses. The sugi
pollen 137Cs concentration (see 2.2)/137Cs deposition ratio was

Pollen/November male flower 137Cs concentration ratio =determined for each year in the period 2012–2016 to provide

1.27 exp (–0.0000895T); (R2 = 0.9292, P = 0.171, n = 3)

Cs aggregated transfer factors (Tags) for

137

137

(1)

Cs transmission

from the environment to sugi pollen.

where T is the number of days since March 11, 2011.

Decay corrections for all 137Cs concentrations were made on 1

Since there were so few data points (n = 3), the slope of

February 2017. We used an online tool (http://www.civilworks.

the regression line was not significant, but the coefficient ofjp/freetool/freetool.htm#normal) to test the normality of the data

determination (R2) was large.

distribution.
森林総合研究所研究報告 第 19 巻 1 号, 2020

Biomass (dry g male flower−1)0.1aMale flower
Male flower husk

0.01

Pollen0.001
2011/3/11 2012/3/11 2013/3/11 2014/3/11 2015/3/12 2016/3/11 2017/3/12

10000

0.01

Male flower
Male flower husk
Pollen0.001

0.0001
2011/3/11 2012/3/11 2013/3/11 2014/3/11 2015/3/12 2016/3/11 2017/3/12

Male flower husk
Male flower
Pollen100

10
2011/3/11 2012/3/11 2013/3/11 2014/3/11 2015/3/12 2016/3/11 2017/3/12

Date

137Cs concentration (Bq dry kg−1)

137Cs content (Bq male flower−1)

c

b

1000

Date

0.1

93

Cs concentrations in the pollen of Cryptomeria

137Cs concentration (Bq dry kg−1)

137

10000

Date

d

1000

100

10
2011/3/11 2012/3/11 2013/3/11 2014/3/11 2015/3/12 2016/3/11 2017/3/12

Date
Fig. 3. Temporal changes in (a) biomass, (b) 137Cs concentration, and (c) the contents of 137Cs in pollen, male flower husks, andmale flowers; (d) current-year leaf 137Cs concentration in Cryptomeria japonica var. japonica.
● ○ Pollen, ▲ △ Male flower husk, ◆ ◇ Male flower, ■ Current-year leaf. Closed symbols represent measured values and open
symbols are estimates.

137Cs concentration ratio

1.4

When we divided the 21 localities into (a) 11 with highPollen/November male flower

1.2

y = 1.27 e-0.0000895x
R2 = 0.9292

1.0male flower 137Cs concentrations (2,600–130,000 Bq dry kg–1)
in the period November–December 2011 and (b) 10 with low
137

Cs concentrations (97–2,500 Bq dry kg–1), we found that

0.8

the logarithmic-mean 137Cs concentrations of male flowers and0.6

current-year leaves decreased over time (Fig. 5a,b). The trends
Pollen/following February male flower

0.4
0.2
0.0

were similar between the two categories of localities: the mean
concentration decreased exponentially with time. We therefore
calculated the logarithmic means and standard deviations (SD)

0

500

1000

1500

Number of days since March 11, 2011

2000

Fig. 4. Temporal changes in Cryptomeria japonica var.
japonica pollen/male flower 137Cs concentration
ratios.
◆ Pollen/November male flower 137Cs concentration
ratio, ◇ pollen/following February male flower 137Csconcentration ratio.

of the male flower 137Cs concentrations across the pooled set of
localities (Fig. 6).
We predicted the logarithmic means (± SD) of current-year
leaf 137Cs concentrations, the male flower 137Cs concentrations,and the estimated pollen 137Cs concentrations by inserting themale flower 137Cs concentrations into equation (1). The 137Csconcentrations of current-year leaves, male flowers, and pollen
declined over time in the November–December periods from

3.2 Estimating theCs concentration in sugi pollen

137

released in spring during the period 2012‒2016
The sugi male flower and current-year leaf

Cs concentration

137

data for Fukushima Prefecture were not normally distributed inany of the years; the distributions may have been lognormal(D’Agostino-Pearson test, K 2 < 5.991, P > 0.050; Anderson andDarling test, A2 < 0.752).
Bulletin of FFPRI, Vol.19, No.1, 20202011 through 2015 (Fig. 6). The 137Cs concentrations in the threeplant components varied significantly, except in 2013: male
flower < pollen (P = 0.008–0.021, n = 21), current-year leaf <pollen (P = 0.006–0.038, n = 21).

94

1000000.1

a137Cs Tag (m2 dry kg−1)

Male flower 137Cs conc. (Bq dry kg−1)

KIYONO, Y. et al.

10000
1000
100

0.001

10
1
2011/3/11 2012/3/11 2013/3/11 2014/3/11 2015/3/12 2016/3/11 2017/3/12

Current-year leaf 137Cs conc. (Bq dry kg−1)

Date1000000.01

0.0001
2011/3/11 2012/3/11 2013/3/11 2014/3/11 2015/3/12 2016/3/11 2017/3/12

Date

Fig. 7. 137Cs point-in-time aggregated transfer factor (Tag)for 137Cs transmission from the environment to
Cryptomeria japonica var. japonica pollen.
The plot provides logarithmic means ± SD for the pollen
137
Cs concentration/deposition (MEXT 2018) ratios
across 21 C. japonica var. japonica forests in Fukushima
Prefecture.

b

10000
1000
100

5). The relationship between the Tag and the quantity of 137Cs

10
1
2011/3/11 2012/3/11 2013/3/11 2014/3/11 2015/3/12 2016/3/11 2017/3/12

deposited was not significant in any year (P = 0.091–0.567, n =21). The Tag was not significantly different between plutonic (n= 14) and sedimentary rocks (n = 3) (P = 0.217–0.995), and no

Date

Fig. 5. Inter-annual changes in 137Cs concentrations in (a)male flowers and (b) current-year leaves of Cryptomeria
japonica var. japonica.
The plot provides logarithmic means ± standard deviation(SD) of 137Cs concentrations in flowers and leaves in 11
localities with high male flower 137Cs concentrations (◆ ■),and in 10 localities with low 137Cs concentrations (◇ □).

trends were detected for igneous rocks (n = 1). The mean (± SD)
Tag value was 0.0203 ± 0.0121 m2 dry kg–1 in February 2012 and0.00168 ± 0.00926 m2 dry kg–1 in February 2016.
4. Discussion
4.1 137Cs in sugi male ﬂowers during the period between

137Cs concentration (Bq dry kg−1)

pollen maturity and pollen release
100000Old leaves and branches of sugi usually die in the fall (Tange

Pollenet al. 1989, Kaneko et al. 1997). Before leaf death, compounds

Nov.–Dec.
current-year leaf

10000

in the withering leaves are transported to the surviving organs.
Since the biomass per male flower was reduced in the periods

1000

100

from November through the following February (Fig. 3a, Table1), it is likely that material resorption occurred in male flowers1)

Nov.–Dec.
male
floweras well as in leaves. The amount of resin in male flowers fell

10
2011/3/11 2012/3/11 2013/3/11 2014/3/11 2015/3/12 2016/3/11 2017/3/12

Date

between November and the following February.
In Osmunda japonica (Kiyono et al. 2018a), Petasites japonicus(Kiyono et al. 2018b), and Eleutherococcus sciadophylloides

Fig. 6. Inter-annual changes in the 137Cs concentrations in
Cryptomeria japonica var. japonica male flowers,
current-year leaves, and pollen.
The plot provides logarithmic means ± SD of 137Csconcentrations in male flowers (◆) and current-year
leaves (■) collected in the November–December period,and in pollen (●) collected in the following February in
21 sugi forest localities in Fukushima Prefecture.

(Akama and Kiyono 2015, Kiyono et al. 2019), the 137Cs tends
to remain in dead leaves. This has not been reported for sugi.
Potassium and Cs is thought to behave similarly in sugi leaves(Yoshihara et al. 2016); we found that K concentrations in male
flowers, female flowers, and leaves were higher than in trunks,
branches, and roots (Appendices 1 and 2). Between November
and the following February, the male flower K concentration
appeared to increase in comparison with other elements, such as

3.3

Cs aggregated transfer factors (Tags) for

137

Cs

137

transmission from the environment to sugi pollen

N (Appendix 3). We therefore propose that 137Cs likely remainedin the dying tissues of sugi (see Fig. 2 in Yoshihara et al. 2016).

Cs Tag decreased exponentially over time

The 137Cs concentration of the male flower husks was higher

after the accident (Fig. 7). The coefficient of variation (CV)in February than in the previous November (Fig. 3b, Table 1).

of Tag was unrelated to time since the accident (P = 0.737, n =The increase in concentration was especially large in the period

The coefficient137

森林総合研究所研究報告 第 19 巻 1 号, 2020

137

Cs concentrations in the pollen of Cryptomeria

95

from November 2011 through the following February. The

flowers had matured, and as the resorption of materials from

Cs in male flower husks increased over this period

male flower husks to leaves progressed, the difference in 137Cs(Fig. 3c, Table 1). Since less than a year had passed following

concentration between pollen and male flower husks widened. We

Cs absorption likely occurred throughapplied equation (1) (using values for male flowers in November

both the roots and above-ground plant surfaces (Mahara et al.

in Fig. 6) to the male flower data for the November–December

2014, Sekiyama et al. 2016, Wang et al. 2016). Consequently,

period. The pollen concentration predicted by equation (1) may

amount of137

the accident, new137

Cs in whole individuals, and in leaves thatbe an overestimation. The coldness of winter is related to thewere nutritionally close to the male flower husks, may havebreaking of dormancy, and warming after the dormancy break is

the quantity of137

Cs adhering to the ante-3.11 leaves

related to the subsequent maturation of male flowers (Kanazashi

that existed before the accident (Kiyono and Akama 2016)

et al. 2016). Since some male flowers might end dormancy in thewas almost entirely lost in the 3 years following the accident

November–December period, the rate of subsequent maturation

due to rain wash-off and leaf death (Kiyono and Akama 2016,

depends to some extent on weather conditions. Hence, theincreased during that time.

137

Cs adhering to thepollen concentrations in Figs. 6 and 7 incorporate uncertainties

leaf surfaces in the November 2011–February 2012 period would

resulting from differences in meteorological conditions in thehave been transferred to the plant body, and probably accounts

sugi habitat and the year in which male flowers bloomed.

Yoshihara et al. 2016). A proportion of the137

for increases in the 137Cs concentration in the male flower husks
after November. The increases in 137Cs concentration in male

4.4 Time since the accident and the radiocesium

flower husks between November and the following February

concentration in sugi pollen

declined over time, becoming negligible in the period fromThe concentration of 137Cs in the current-year leaves (Appendix

2016 to 2017, likely because the transfer of new 137Cs from the4) and male flowers declined over the years after the accident

environment to sugi was reduced. Thus, the concentration in(Akama et al. 2017). We found that the decline in concentrationeach component of the trees appeared to have stabilized.

in mature pollen was similar to that in male flowers (Fig. 6). The
supply of 137Cs can vary by habitat soil (Saunton et al. 2003,

Note 1) A similar phenomenon was observed in the fruit ofSalt et al. 2004, Yamaguchi 2014) and geology, as found for

Akebia trifoliata (Kiyono and Akama, unpublished data). The

Eleutherococcus sciadophylloides (Kiyono et al. 2019): shootmoisture content proportion in the fruit was 0.24, and the biomass137

was 19.6 dry g fruit , immediately before the fruit opened. The(Kawamata) and igneous rocks (Kaneyama) than in thosemoisture content proportion of opened fruit was 0.12 and thewith sedimentary rocks (Hirono). However, we did not detectbiomass was 9.7 dry g fruit .

similar habitat effects on sugi pollen in our study. The pollen–1–1

Cs concentrations become higher in habitats with plutonic

Cs concentration in February 2016 was 8% of that in February

137

4.2 Evaluation of previous assumptions on the quantitative

2012 (Fig. 6). Differences in the initial 137Cs concentration had

relationship between sugi male ﬂowers and pollen

little effect on the rate of decrease over time (Fig. 5). It was

In a press release issued in late 2011, the MAFF (2011)

predicted that over 90% of 137Cs in ante-3.11 leaves would beassumed that pollen biomass accounted for 50% of male flower

removed within 3 years of the FDNPS accident (Kiyono andbiomass. According to our findings, this was an overestimate

Akama 2016). Transfer from 137Cs deposits in bark would havefor male flowers in the November–December period, whencontinued, even after transfer from the leaves over the short term

pollen accounted for about one third of flower biomass (Table

had decreased. However, within 3 years of the FDNPS accident,Cs

the amount of 137Cs in bark was less than in leaves (Kajimoto

concentration in sugi pollen was the same as the concentration

et al. 2015) and the amounts of 137Cs transferred from barkin male flowers during these months was reasonable (Table 1).

would therefore be relatively small. By about March 2014, root

Thus, the amount of 137Cs contained in airborne pollen was 60–

absorption would have been the main supply source of 137Cs

70% of the value proposed by the MAFF (2011).

to the plant body of sugi. The 137Cs distribution in sugi wood1). However, the assumption of the MAFF that the137

approached an equilibrium state within 3 years of the accident
4.3 Relationship between

Cs concentrations in sugi

137

male ﬂowers and pollen in November
We found no significant difference in(Ogawa et al. 2016), but such equilibrium state was not observedin the same period in some other sugi forests (Imamura et al.

Cs concentration

137

2017, Ohashi et al. 2017).

between male flowers and pollen in November (Fig. 3b, Table

The decrease in 137Cs concentration in male flowers and pollen

1). Since pollen becomes nutritionally independent in the malematched the decrease (Mahara et al. 2014, Imamura et al. 2017)

flower by November, the 137Cs concentrations in male flower

in sugi leaf 137Cs concentrations. However, pollen production

husks and pollen were considered to be similar. After the malevaries greatly from year to year; summer weather conditions in

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96

KIYONO, Y. et al.

the two preceding years greatly influence the amount of pollen

pollen 137Cs concentrations in eastern Japan can be estimatedproduced (Takahashi et al. 1996, Takahashi and Kawashimafrom 137Cs deposition data in the Extension Site of Distribution

1999, Kiyono 2010). The amount of pollen captured in

Map of Radiation Dose, etc.,/GSI Maps (MEXT 2018) and the

Fukushima City between 2012 and 2016 was highest in 2013

Tag for the relevant year (Fig. 7). Multiplication of these data and(Hanako, Ministry of the Environment 2016), but we found nopollen biomass (about ⅓ of the male flower biomass) provides

clear trends in the 137Cs concentrations in sugi male flowers andan estimate of the 137Cs content of sugi pollen in a single year

pollen in 2013 (Figs. 3–7). The influence of fluctuations in pollen

over a wide area before pollen release. For example, sugi pollen

production on pollen 137Cs concentration was not determined inreleased in spring 2016 from a sugi forest where the 137Cs

detail in our study (see Appendix 3).

deposition was 800 kBq m–2 on July 2, 2011 was calculated toCscontain ca. 1,180 Bq dry kg–1 of 137Cs based on the known 137Csconcentration between November and the following February

deposition (704 kBq m–2 after attenuation correction) and a Tag of

We found no significant difference in the current-year leaf
(Fig. 3d, Table 1). During this period, the current-year leaf

137

137

Cs

0.00168 m2 dry kg–1 as of 2016.

concentration appeared more stable than the concentration inmale flowers. The current-year leaf 137Cs concentration in sugi

5. Conclusions

forest was higher than that of pollen in November 2011, but the

There are few data on 137Cs in flower organs. Based on theconcentrations were not significantly different after November

measurements made on male flowers before pollen release, we

2012 (Fig. 3b,d; Table 1). However, data obtained in our broadwere able to more precisely estimate the amount of 137Cs released

area survey over 21 localities in Fukushima prefecture showedby sugi pollen than previous investigations. It might be possible

Cs concentrations were low in the current year leaves

to estimate pollen 137Cs concentration from the current-year leaf

that

137

Cs concentration, but this will require rigorous verification inin most cases since November 2012 (Figs. 5 and 6). Since

137

concentrations in current year leaves and pollen showed similar

future studies. The transfer of 137Cs from the environment to sugi

trends over the years, the current year leaf 137Cs concentration inpollen had not stabilized 5 years after the accident, and further

Cs concentration

monitoring will be required to determine the 137Cs Tag value in thein pollen released in the following February. Kanasashi et al.

equilibrium state. The 137Cs concentration of sugi pollen should(2015) found that within the period from November 2012 tobe lower in the future, but pollen production fluctuates year on

February 2013, in regions partially overlapping those included

year, and the 137Cs mass released by pollen fluctuates accordingly.

in our study and extending over a wide area of eastern JapanThe relationship between sugi pollen production and pollen 137Cs(mostly in Fukushima Prefecture), the 137Cs concentration

content is unknown and awaits future investigations.

November may be useful for estimating the137

in leaves was lower than concentrations in male flowers andpollen. However, the 137Cs concentration at the tips of the leaves

Acknowledgmentsthat produced male flowers was higher than the concentrations

Special thanks are due to the staff of the former Research,in male flowers and pollen. 137Cs concentrations differ among

Extension, and Environment Policy Division and Forest

leaf parts (Burger and Lichtscheidl 2017). Studies of leaf parts

Research, Extension and Protection Division of the Privatethat could be used as an appropriate indicator of pollen 137Cs

Forest Department of Japan’s Forestry Agency and theconcentration should be undertaken in future investigations.

Fukushima Prefectural Forestry Research Centre, particularly
Mr. Norio Takanobu and Mr. Hirohisa Ito (currently at the

4.5 137Cs aggregated transfer factors (Tags) for

Cs

137

Soso Agriculture and Forestry Office), for help during ourtransmission from the environment to sugi pollen

fieldwork to collect samples. We thank Dr. Akinori Nagao

The 137Cs Tag declined year on year from February 2012 through(Japan Science and Technology Agency, JST) for his advice on

February 2016, and had not reached an equilibrium state by thethe ecophysiology of floral initiation in sugi. We also thank thefifth year after the FDNPS accident (Fig. 7). After the Chernobyl

Center for Forest Restoration and Radioecology at the FFPRI

Cs dispersed

for help in processing and analyzing samples with an HPGeamong trees and soils of the polluted forests to stabilize (IAEA

coaxial detector system located at the FFPRI. This research was2009). The coefficients calculated for the unbalanced stage were

supported by research grants from the FFPRI (# 201128) and theaccompanied by large errors (Yoshida 2012). Therefore, theForestry Agency, and in part by the Priority Research Assistancevalues in Fig. 7 are temporal and applicable only to the relevant

Cooperator program of the JST.

accident, it took 5–10 years for the movement of

137

year. However, there were no significant inter-annual trends in
Cs Tag within a deposition range of 5–4,500 kBq m–2 (as of July

137

2, 2011). Since the data on 137Cs deposition covered almost all
sugi forests in eastern Japan, including Fukushima Prefecture,
森林総合研究所研究報告 第 19 巻 1 号, 2020

137

Cs concentrations in the pollen of Cryptomeria

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Appendix 1. C, N, P, K, Ca, Mg, Na, and Mn concentrations

leaves, branches, stems, and roots. The concentrations of C, N,

in organs of Cryptomeria japonica var. japonica andP, K, Ca, Mg and Mn were measured (Table A1-2, Vegetation

Chamaecyparis obtusa.

Control Laboratory, FFPRI). A CN elemental analyzer was used

In July 2001, trees in the young forests of Cryptomeria

to measure C and N; P was measured by inductively coupledjaponica var. japonica (sugi) and Chamaecyparis obtusa (hinoki)

plasma emission spectroscopy (ICP); flame photometry was used

(Table A1-1) in the nursery of the Chiyoda Experimental Station

to measure K and Mn; atomic absorption spectrometry was usedof FFPRI in Kasumigaura City, Ibaraki Prefecture were divided

to measure Ca and Mg (Ringyo Kagaku Gijutsu Shinkosho).

into three size classes per species. A sample tree was dug out
from each compartment containing two species and trees ofthree size classes. Simultaneously, GA3 (gibberellic acid) was
sprayed on the leaves to promote flowering in some of the live
standing trees; similar numbers of trees were used as controls. In
the period February–March 2002, three sprayed trees and threecontrol trees in three size classes of both species were sampled.
The sampled trees were divided into organs: male flowers, female
flowers (since male and female hinoki flowers were difficult todistinguish, they were combined into a single flower category),

Table A. 1-1. General description of surveyed trees.
Sampling
date
2001.7
2002.2
2002.2
2001.7
2002.3
2002.3

DBH Tree height Tree biomass-1
cmm
dry kg tree
Sugi
2.7 ± 0.8 2.9 ± 0.7
2.8 ± 1.3
Sugi 2001.7 GA3 2.9 ± 0.8 3.2 ± 0.6
4.1 ± 1.4Sugi
3.1 ± 0.9 3.1 ± 0.6
4.3 ± 2.0
Hinoki2.0 ± 0.3 2.7 ± 0.2
3.3 ± 0.6
Hinoki 2001.7 GA3 2.8 ± 0.5 2.9 ± 0.9
3.5 ± 1.1
Hinoki2.6 ± 0.3 2.8 ± 1.5
3.5 ± 0.7

SpeciesTreatment

Values are mean ± SD. Sugi, Cryptomeria japonica var. japonica.
Hinoki, Chamaecyparis obtusa. DBH, diameter at breast height.

Table A1-2. C, N, P, K, Ca, Mg, Na, and Mn concentrations in organs of Cryptomeria japonica var. japonica and Chamaecyparis
obtusa.
Sampling
Speciesdate
2002.2
Sugi
2002.2
Sugi
2002.2
Sugi
2002.2
Sugi
2001.7
Sugi
2002.2
Sugi
2002.2
Sugi
2001.7
Sugi
2002.2
Sugi
2002.2
Sugi
2001.7
Sugi
2002.2
Sugi
2002.2
Sugi
2001.7
Sugi
2002.2
Sugi
2002.2
Sugi

GA3
SampleOrgan
trees
treatment
2001.7
Male flower
3
Male flower
1
2001.7 Female flower
3
Female flower
3
Leaf
3
2001.7
Leaf
3
Leaf
3
Branch3
2001.7
Branch3
Branch3
Stem
3
2001.7
Stem
3
Stem
3
Root
3
2001.7
Root
3
Root
3

C
%
51.8 ± 1.0
52.6
49.3 ± 1.1
49.7 ± 0.3
52.3 ± 0.6
51.1 ± 0.4
51.3 ± 0.2
49.8 ± 0.5
49.5 ± 0.3
49.9 ± 0.3
50 ± 150 ± 0.2
50 ± 0.3
49.2 ± 0.1
49.6 ± 0.3
50.5 ± 1.1

N%0.74 ± 0.04
0.74
1.15 ± 0.13
1.04 ± 0.59
0.97 ± 0.04
0.78 ± 0.07
0.80 ± 0.01
0.47 ± 0.05
0.44 ± 0.03
0.47 ± 0.02
0.34 ± 0.1
0.34 ± 0.02
0.34 ± 0.02
0.35 ± 0.04
0.33 ± 0.03
0.68 ± 0.36

P%
0.20 ± 0.01
0.17
0.27 ± 0.01
0.18 ± 0.13
0.19 ± 0.08
0.22 ± 0.03
0.22 ± 0.03
0.069 ± 0.020
0.050 ± 0.005
0.059 ± 0.006
0.023 ± 0.001
0.022 ± 0.01
0.028 ± 0.01
0.032 ± 0.003
0.024 ± 0.008
0.119 ± 0.097

K%
0.84 ± 0.04
0.91
0.95 ± 0.08
0.57 ± 0.38
0.64 ± 0.19
0.69 ± 0.13
0.65 ± 0.08
0.29 ± 0.07
0.22 ± 0.02
0.28 ± 0.03
0.16 ± 0.03
0.12 ± 0.02
0.11 ± 0.01
0.23 ± 0.02
0.13 ± 0.05
0.41 ± 0.31

Ca%
0.50 ± 0.06
0.37
1.23 ± 0.34
0.91 ± 0.30
1.13 ± 0.12
1.06 ± 0.20
1.20 ± 0.19
0.90 ± 0.29
0.73 ± 0.10
0.78 ± 0.05
0.35 ± 0.06
0.38 ± 0.03
0.43 ± 0.04
0.49 ± 0.10
0.45 ± 0.05
0.77 ± 0.35

Mg%
0.20 ± 0.05
0.17
0.30 ± 0.05
0.20 ± 0.12
0.18 ± 0.02
0.20 ± 0.02
0.19 ± 0.03
0.103 ± 0.050
0.086 ± 0.013
0.084 ± 0.013
0.038 ± 0.004
0.041 ± 0.007
0.039 ± 0.002
0.057 ± 0.008
0.048 ± 0.005
0.110 ± 0.010

Na%
0.0050 ± 0.0010
0.085
0.0026 ± 0.0006
0.0079 ± 0.0027
0.0054 ± 0.0011
0.0012 ± 0.0007
0.0045 ± 0.0005
0.0004 ± 0.0006
0.0047 ± 0.0027
0.0023 ± 0.0040
ND
ND
ND
0.0067 ± 0.0027
0.0058 ± 0.0020
0.0040 ± 0.0037

Mn%
0.0036 ± 0.0007
0.00250.0057 ± 0.0004
0.0034 ± 0.0012
0.0024 ± 0.0003
0.0019 ± 0.0004
0.0020 ± 0.0001
0.0008 ± 0.0001
0.0007 ± 0.00003
0.0009 ± 0.00005
0.00056 ± 0.00015
0.00051 ± 0.00005
0.00053 ± 0.00007
0.0040 ± 0.0008
0.0022 ± 0.0004
0.0041 ± 0.0034

2002.3
2002.3
2001.7
2002.3
2002.3
2001.7
2002.3
2002.3
2001.7
2002.3
2002.3
2001.7
2002.3
2002.3

2001.7
2001.7
2001.7
2001.7
2001.7-51 ± 249.9 ± 0.01
52.2 ± 0.6
51.0 ± 0.5
51.2 ± 1.0
50.6 ± 0.3
50.1 ± 0.1
50.4 ± 0.2
49.8 ± 0.3
49.6 ± 0.1
49.9 ± 0.2
50.2 ± 0.3
49.9 ± 0.1
49.5 ± 0.2

2.1 ± 0.7
1.6 ± 0.04
1.21 ± 0.27
1.01 ± 0.09
0.86 ± 0.06
0.42 ± 0.02
0.47 ± 0.02
0.44 ± 0.02
0.33 ± 0.02
0.39 ± 0.01
0.35 ± 0.03
0.40 ± 0.05
0.35 ± 0.01
0.36 ± 0.01

0.36 ± 0.14
0.31 ± 0.06
0.16 ± 0.02
0.23 ± 0.11
0.20 ± 0.08
0.051 ± 0.012
0.048 ± 0.009
0.041 ± 0.007
0.024 ± 0.007
0.046 ± 0.006
0.034 ± 0.005
0.050 ± 0.015
0.036 ± 0.011
0.041 ± 0.010

0.84 ± 0.29
0.64 ± 0.12
0.59 ± 0.08
0.53 ± 0.06
0.51 ± 0.08
0.24 ± 0.01
0.18 ± 0.02
0.16 ± 0.01
0.15 ± 0.01
0.13 ± 0.02
0.12 ± 0.02
0.21 ± 0.03
0.10 ± 0.02
0.12 ± 0.03

0.57 ± 0.09
0.89 ± 0.03
1.1 ± 0.3
1.1 ± 0.2
1.2 ± 0.3
0.72 ± 0.16
0.76 ± 0.09
0.81 ± 0.05
0.33 ± 0.04
0.42 ± 0.04
0.45 ± 0.08
0.39 ± 0.10
0.31 ± 0.04
0.37 ± 0.04

0.17 ± 0.02
0.20 ± 0.05
0.17 ± 0.02
0.15 ± 0.01
0.14 ± 0.02
0.045 ± 0.006
0.038 ± 0.001
0.039 ± 0.001
0.020 ± 0.003
0.025 ± 0.001
0.022 ± 0.001
0.070 ± 0.023
0.036 ± 0.005
0.046 ± 0.002

0.0057 ± 0.0011
0.0097 ± 0.0114
0.0052 ± 0.0019
0.0037 ± 0.0030
0.0028 ± 0.0010
ND
0.0067 ± 0.0017
0.0080 ± 0.0067
ND
0.0007 ± 0.0012
ND
0.0053 ± 0.0021
0.0038 ± 0.0021
0.0025 ± 0.0002

0.0051 ± 0.0019
0.0097 ± 0.0029
0.0114 ± 0.0011
0.0073 ± 0.0002
0.0098 ± 0.0013
0.0020 ± 0.0003
0.0015 ± 0.0002
0.0021 ± 0.0006
0.00012 ± 0.00005
0.0012 ± 0.0002
0.0015 ± 0.0001
0.0071 ± 0.0045
0.0025 ± 0.0002
0.0036 ± 0.0008

HinokiHinokiHinokiHinokiHinokiHinokiHinokiHinokiHinokiHinokiHinokiHinokiHinokiHinokiFlowerFlower
Leaf
Leaf
Leaf
BranchBranchBranch
Stem
Stem
Stem
Root
Root
Root

2
2
3
3
3
3
3
3
3
3
3
3
3
3

Values are mean ± SD. Sugi, Cryptomeria japonica var. japonica. Hinoki, Chamaecyparis obtusa. GA3 treatment, sprayed withgibberellic acid.
Appendix 2. C, N, P, K, Ca, Mg, and Mn concentrations

in February 2005 were harvested and separated into organs:in organs of Cryptomeria japonica var. japonica (Bokasugi

male flowers, female flowers, leaves, branches, stems, and roots.

clone).

The concentrations of C, N, P, K, Ca, Mg and Mn elements

GA3 was sprayed on the leaves (in July 2002, 2003, and 2004)

were measured for each organ (Table A2-2, Vegetation Controlof some of the live standing trees in a Cryptomeria japonica var.

Laboratory, FFPRI). A CN elemental analyzer was used tojaponica (Bokasugi clone) forest (Kiyono et al. 2006) establishedmeasure C and N; P was measured by ICP; flame photometryin April 2002 in the nursery of FFPRI in Tsukuba City, Ibaraki

was used to measure K and Mn; atomic absorption spectrometry

Prefecture. The spray was applied to promote flowering (Table

was used to measure Ca and Mg (Ringyo Kagaku Gijutsu

A2-1). Twelve individuals in February 2004 and ten individuals

Shinkosho). A negligible number of flowers formed after the
森林総合研究所研究報告 第 19 巻 1 号, 2020

137

101

Cs concentrations in the pollen of Cryptomeria

Table A2-1. Schedule of GA3 (gibberellic acid) spraying andsubsequent sampling of Cryptomeria japonica
var. japonica (Bokasugi clone) trees.

GA3 treatment in July 2004. The mean monthly temperature andmonthly rainfall during the test period differed little from normal
values, although precipitation in October 2004 was especiallyheavy.

Abbrev.

2002.7

2003.7

2004.2

GA3
GA3

2
4
2
4

2004.72005.2Treatment Treatment Sample trees Treatment Sample trees

GA3

-2-/4
--3/4
-23/4
--- /4-2--/5--3-/5---4/5-2-4/5--34/5---- /5

GA3
GA3

GA3

GA3

GA3
GA3
GA3

GA3

Table A2-2. C, N, P, K, Ca, Mg, and Mn concentrations in organs of Cryptomeria japonica var. japonica(Bokasugi clone).
Sampling
date

GA3 treatment

Organ

Sample
trees

C
%

N
%

P
%

K
%

Ca
%

Mg
%

Mn
%

2004.2

2002.7Root

2

50 ± 10.64 ± 0.12

0.069 ± 0.007

0.25 ± 0.01

0.46 ± 0.04

0.051 ± 0.008

0.0025 ± 0.0020

2004.2

2003.7Root

450 ± 10.61 ± 0.04

0.067 ± 0.013

0.27 ± 0.10

0.52 ± 0.08

0.055 ± 0.006

0.0022 ± 0.0011

2004.2

2002.7, 2003.7

Root

2

49 ± 10.68 ± 0.12

0.068 ± 0.003

0.27 ± 0.02

0.53 ± 0.07

0.058 ± 0.005

0.0027 ± 0.0008

2004.2-450 ± 10.64 ± 0.13

0.067 ± 0.013

0.28 ± 0.05

0.46 ± 0.04

0.057 ± 0.010

0.0027 ± 0.0013

2004.2

2003.7455 ± 0.4

1.3 ± 0.2

0.19 ± 0.02

0.92 ± 0.28

0.42 ± 0.20

0.10 ± 0.02

0.0015 ± 0.0001

2004.2

2002.7, 2003.7

254 ± 0.2

1.3 ± 0.2

0.17 ± 0.02

0.97 ± 0.12

0.40 ± 0.03

0.11 ± 0.01

0.0018 ± 0.0001

2004.2

2003.7451 ± 0.5

1.7 ± 0.2

0.21 ± 0.02

0.89 ± 0.24

0.77 ± 0.11

0.14 ± 0.01

0.0026 ± 0.0005

2004.2

2002.7, 2003.7

0.0021 ± 0.0007

2004.2

2002.7

Root
Male
flowerMale
flowerFemaleflowerFemaleflowerLeaf

2004.2

2003.7

2004.2
2004.2
2004.2

2

51 ± 0.2

1.8 ± 0.1

0.18 ± 0.01

0.83 ± 0.39

0.52 ± 0.27

0.12 ± 0.03

251 ± 0.05

1.58 ± 0.07

0.131 ± 0.022

0.78 ± 0.16

1.22 ± 0.04

0.090 ± 0.010

0.0021 ± 0.0004

Leaf

4

51 ± 0.3

1.48 ± 0.10

0.132 ± 0.013

0.89 ± 0.23

1.07 ± 0.05

0.068 ± 0.011

0.0018 ± 0.0001

2002.7, 2003.7
-

Leaf

2

51 ± 0.1

1.50 ± 0.03

0.132 ± 0.027

0.80 ± 0.13

1.15 ± 0.22

0.088 ± 0.017

0.0016 ± 0.0004

Leaf

4

52 ± 0.2

1.46 ± 0.12

0.115 ± 0.003

0.75 ± 0.14

1.14 ± 0.16

0.091 ± 0.014

0.0020 ± 0.0003

2002.7

Branch2

50 ± 0.3

0.98 ± 0.01

0.078 ± 0.010

0.47 ± 0.12

0.88 ± 0.07

0.060 ± 0.012

0.0010 ± 0.0001

2004.2

2003.7

Branch450 ± 0.3

0.89 ± 0.15

0.073 ± 0.004

0.45 ± 0.09

0.80 ± 0.10

0.051 ± 0.010

0.0009 ± 0.0001

2004.2

Branch2

50 ± 0.5

0.86 ± 0.15

0.073 ± 0.002

0.45 ± 0.09

0.84 ± 0.03

0.057 ± 0.003

0.0010 ± 0.0001

2004.2

2002.7, 2003.7-

Branch451 ± 0.2

0.86 ± 0.08

0.070 ± 0.014

0.42 ± 0.09

0.78 ± 0.12

0.066 ± 0.014

0.0010 ± 0.0002

2004.2

2002.7Stem

2

50 ± 10.51 ± 0.12

0.053 ± 0.017

0.25 ± 0.05

0.47 ± 0.07

0.036 ± 0.004

0.00055 ± 0.00023

2004.2

2003.7Stem

4

50 ± 10.51 ± 0.06

0.048 ± 0.007

0.22 ± 0.04

0.46 ± 0.08

0.034 ± 0.005

0.00065 ± 0.00022

2004.2Stem

2

50 ± 10.43 ± 0.01

0.45 ± 0.07

0.029 ± 0.007

0.00055 ± 0.00016

Stem

4

50 ± 10.47 ± 0.06

0.033 ± 0.003
0.041 ± 0.007

0.15 ± 0.06

2004.2

2002.7, 2003.7-

0.19 ± 0.03

0.41 ± 0.04

0.036 ± 0.004

0.00059 ± 0.00015

2005.2

2002.7

Leaf

1

50

1.29

0.091

0.66

1.30

0.088

0.00182005.2

2003.7Leaf

250 ± 0.3

1.14 ± 0.31

0.122 ± 0.023

0.76 ± 0.07

1.11 ± 0.08

0.122 ± 0.026

0.0019 ± 0.0001

2005.2

2004.7Leaf

250 ± 0.2

1.29 ± 0.04

0.107 ± 0.005

0.80 ± 0.03

1.39 ± 0.11

0.077 ± 0.005

0.0020 ± 0.0002

2005.2

2002.7, 2004.7

Leaf

1

50

1.34

0.099

0.74

1.24

0.073

0.00152005.2

2003.7, 2004.7

Leaf

2

50 ± 0.1

1.41 ± 0.10

0.116 ± 0.008

0.85 ± 0.02

1.23 ± 0.23

0.112 ± 0.056

0.0022 ± 0.0010
0.0017 ± 0.0001

2005.2-Leaf

250 ± 0.3

1.35 ± 0.05

0.101 ± 0.008

0.84 ± 0.06

1.08 ± 0.09

0.112 ± 0.030

2005.2

2002.7

Branch

1

49

0.54

0.044

0.29

0.77

0.041

0.00067

2005.2

2003.7

Branch249 ± 0.2

0.43 ± 0.17

0.040 ± 0.003

0.31 ± 0.02

0.73 ± 0.002

0.050 ± 0.020

0.00068 ± 0.00016
0.00057 ± 0.00001

2005.2

2004.7

Branch2

45 ± 50.44 ± 0.06

0.039 ± 0.0002

0.29 ± 0.05

0.78 ± 0.06

0.037 ± 0.001

2005.2

2002.7, 2004.7

Branch

1

49

0.49

0.038

0.28

0.76

0.039

0.00055

2005.2

2003.7, 2004.7

Branch249 ± 0.3

0.53 ± 0.01

0.040 ± 0.002

0.30 ± 0.03

0.73 ± 0.01

0.053 ± 0.016

0.00070 ± 0.00010

2005.2-

Branch249 ± 0.1

0.50 ± 0.04

0.036 ± 0.001

0.27 ± 0.04

0.69 ± 0.10

0.047 ± 0.011

0.00063 ± 0.00006

2005.2

2002.7

Stem

1

50

0.35

0.032

0.20

0.35

0.024

0.00060

2005.2

2003.7Stem

2

50 ± 0.3

0.29 ± 0.09

0.026 ± 0.006

0.18 ± 0.02

0.32 ± 0.03

0.028 ± 0.008

0.00053 ± 0.00011

2005.2

2004.7Stem

2

50 ± 0.2

0.29 ± 0.002

0.028 ± 0.003

0.16 ± 0.01

0.36 ± 0.08

0.024 ± 0.004

0.00059 ± 0.00003

2005.2

2002.7, 2004.7

Stem

1

50

0.39

0.036

0.21

0.36

0.026

0.00073

2005.2

2003.7, 2004.7

Stem

2

50 ± 10.34 ± 0.06

0.030 ± 0.007

0.19 ± 0.07

0.38 ± 0.05

0.032 ± 0.010

0.00062 ± 0.000001

2005.2-Stem

2

50 ± 0.4

0.35 ± 0.01

0.029 ± 0.003

0.18 ± 0.01

0.38 ± 0.01

0.028 ± 0.002

0.00060 ± 0.00017

2005.2

2002.7

Root

1

49

0.41

0.044

0.28

0.40

0.039

0.00226

2005.2

2003.7Root

2

50 ± 0.3

0.33 ± 0.12

0.031 ± 0.008

0.19 ± 0.03

0.38 ± 0.04

0.039 ± 0.005

0.00143 ± 0.00053

2005.2

2004.7Root

2

49 ± 0.2

0.33 ± 0.14

0.035 ± 0.015

0.25 ± 0.09

0.45 ± 0.003

0.038 ± 0.003

0.00189 ± 0.00005

2005.2

2002.7, 2004.7

Root

1

49

0.47

0.043

0.24

0.48

0.041

0.00173

2005.2

2003.7, 2004.7

Root

2

49 ± 10.35 ± 0.02

0.032 ± 0.005

0.20 ± 0.02

0.35 ± 0.003

0.033 ± 0.001

0.00144 ± 0.00027

2005.2-Root

249 ± 0.2

0.32 ± 0.005

0.028 ± 0.003

0.18 ± 0.02

0.33 ± 0.09

0.031 ± 0.001

0.00166 ± 0.00014

Values are mean ± SD. GA3 treatment, sprayed with gibberellic acid.
Bulletin of FFPRI, Vol.19, No.1, 2020

1
2
2
1
2
2

102

KIYONO, Y. et al.

Appendix 3. Temporal changes in C, N, P, K, Ca, Mg, and Mn

those for the other elements; the February K concentration

contents in Cryptomeria japonica var. japonica male flowers.

exceeded the November K concentration in all four individuals

We sampled Cryptomeria japonica var. japonica (Kurakake 3

tested (Table A3-1). The concentration ratios for N and K wereclone) in a forest established in April 2002 at the FFPRI nursery

significantly different (paired t-test, P = 0.043, n = 4), but there

in Tsukuba City, Ibaraki Prefecture. Four trees of similar size

were no other significant pairwise differences, likely because

were selected and male flowers were collected on February 14,

sample sizes were small. Compared to the other elements, the2008, November 21, 2008, and February 11, 2009. We measured

K content was maintained at relatively high levels throughout

concentrations of C, N, P, K, Ca, Mg, and Mn in the flowers.

the pollen dispersal season (February). The February K contents

A CN elemental analyzer was used to measure C and N; P waswere not significantly different between 2008 and 2009 (paired

measured by ICP; flame photometry was used to measure K andt-test, P = 0.160, n = 4). The Kurakake 3 clone produced a

Mn; atomic absorption spectrometry was used to measure Ca

relatively large biomass of male flowers in every year. The

and Mg (Ringyo Kagaku Gijutsu Shinkosho). The concentration

quantity of male flowers was higher in 2008 than in 2009 (Fig.

ratios for February 2009/November 2008 were 0.99 ± 0.24

A3-1), corresponding to the increase/decrease pattern in airborne[mean ± SD] (n = 4) for N, 0.96 ± 0.24 (n = 4) for P, 1.06 ± 0.23

cedar pollen concentration (MAFF 2011) in the Kanto region.

(n = 4) for Ca, 0.94 ± 0.11 (n = 4) for Mg, and 0.79 ± 0.27 (n =The data are insufficient to explain how the annual fluctuation in4) for Mn. Concentrations were similar between November 2008

pollen affects the nutritional status of pollen.

and February 2009. The ratio for K (1.25 ± 0.21 n = 4) exceeded

Fig. A3-1. Monitored branch with leaves forming male flowers.
Left 2007.12.31, right 2008.11.21.

Table A3-1. Temporal changes in Cryptomeria japonica var. japonica cv. Kurakake 3 male flower C, N, P, K, Ca, Mg, andMn contents. conc. ratio refers to the concentration ratios for 11 February 2009/21 November 2008.

1
2
3
4

C
%
53.8
53.8
52.6
53.4

N
%
0.85
0.86
0.88
0.86

P
%
0.098
0.104
0.133
0.155

K
%
0.293
0.342
0.348
0.481

Ca
%
0.204
0.166
0.193
0.148

Mg
%
0.076
0.071
0.068
0.065

Mn
%
0.00230.00100.00130.00102008.11.21
2008.11.21
2008.11.21
2008.11.21

1
2
3
4

54.6
54.9
55.1
54.4

0.78
0.93
0.89
0.82

0.145
0.199
0.169
0.153

0.251
0.318
0.233
0.259

0.163
0.105
0.078
0.128

0.056
0.055
0.057
0.060

0.00150.00100.00060.00152009.2.11
2009.2.11
2009.2.11
2009.2.11

1
2
3
4

54.9
54.3
55.2
54.0

0.78
0.88
0.78
0.92

0.178
0.135
0.144
0.162

0.294
0.332
0.290
0.396

0.159
0.145
0.082
0.107

0.057
0.058
0.051
0.049

0.00120.00070.00060.00072009.2.11/2008.11.
21 conc. ratio

Mean ± SD

1.00 ± 0.01

0.99 ± 0.10

0.96 ± 0.24

1.25 ± 0.21

1.06 ± 0.23

0.94 ± 0.11

0.79 ± 0.27

Sampling dateTree no.

2008.2.14
2008.2.14
2008.2.14
2008.2.14

森林総合研究所研究報告 第 19 巻 1 号, 2020

137

103

Cs concentrations in the pollen of Cryptomeria

Appendix 4. The quantity of 137Cs per Cryptomeria japonica

or decrease as the leaves aged (within the data range) (Fig.

var. japonica leaves in 21 forests within Fukushima PrefectureA4-1). Kiyono and Akama (2016) predicted that the leaf 137Cs

after the Fukushima Daiichi Nuclear Power Station accident.

concentration would decrease in the current-year leaves year-

In 2016, we divided sugi leaves collected at Iwaki (Fig. 1) byby-year, and also decrease with leaf aging based on the leaf

Cs concentrations in sugi male flowers

dynamics model. The pattern of annual change in the amountand leaves collected at Iwaki have been measured annuallyof 137Cs per current-year leaf in this study (Fig. A4-1) matchedsince 2011. We measured the numbers, lengths, and dry weights

the model predictions of Kiyono and Akama (2016). As theof leaves collected in November 2016. Assuming (i) that theleaves aged, the numbers thereof decreased (Fig. A4-2), andmeasured values can be applied to samples obtained in thethe dry weights of leaves in the same length category tended toperiod 2011–2015, and to the other 20 localities, and (ii) that theincrease (Fig. A4-3), likely due to leaf thickening as they grew

their birth year. The

137

Cs concentration in 2011 (Bq dry kg ) can be estimatedinto branches following the development of the xylem. Since thefrom the male flower 137Cs concentration in 2011 (Bq dry kg–1)

increase in dry weight in leaves (Fig. A4-3) offset the decreaseusing an unpublished regression by the Forestry and Forest

in 137Cs concentration per unit dry weight (Figs. 5 and 6), theProducts Research Institute (FFPRI) based on the data fromquantity of 137Cs per leaf did not clearly increase/decrease as thefive prefectures between Nagano and Fukushima: Leaf 137Cs

leaves aged (Fig. A4-1).

leaf

137

–1

concentration in 2011 = 0.3915 [Male flower 137Cs concentration
the quantity of 137Cs per current year leaf (Fig. A4-1, decay
correction: 1 Dec 2011) using the following equation:
Quantity of 137Cs per leaf = Leaf 137Cs concentration × Leaf
weightWhen we examined leaves that formed in the same year, we

0.1

0.15
0.1
0.05
0

0.01

0.001

0.2

2011/11–12

2012/11–12

2013/11–12

2014/11–12

DateFig. A4-1. The content of 137Cs per Cryptomeria japonica
var. japonica leaf (a) 8–9 months after the nuclear
accident and (b) 3 years (plus 8–9 months) after
the accident.
Data were collected in 21 C. japonica var. japonica
forests in Fukushima Prefecture (Akama et al. 2013;
Forestry Agency 2015, revised). ×, leaves that formed
in 2011; Δ, leaves that formed in 2012; ●, leaves thatformed in 2013; □, leaves that formed in 2014. Decay
correction date: December 1, 2011. Content of 137Cs
per leaf = leaf 137Cs concentration × leaf weight.
---, curve connecting the current-year leaves. The
leaf 137Cs concentration in 2011 (Bq dry kg–1) was
estimated from the male flower 137Cs concentration in2011 (Bq dry kg–1) using an unpublished regression
by the Forestry and Forest Products ResearchInstitute (FFPRI) based on the data from fiveprefectures between Nagano and Fukushima: Leaf
137
Cs concentration in 2011 = 0.3915 [Male flower
137
Cs concentration in 2011] 1.2022; (R² = 0.7812, P <0.001, n = 13).
Bulletin of FFPRI, Vol.19, No.1, 2020

2

4

6

8

10

12

Leaf length class (cm)

14

16

18

Fig. A4-2. Number of leaves of Cryptomeria japonica var.
japonica in each leaf length class.
Leaf-bearing branches of several trees were collected
and combined in Iwaki in November 2016. We added
2 cm to the length of each current-year leaf to take
into account leaf elongation occurring between
November and the following spring. □, current-year
leaf; ⊠ , 1-year-old leaf; ■, 2-year-old leaf.

Mean leaf weight (dry g leaf−1)

Content of 137Cs per leaf (Bq leaf−1)

found that the quantity of 137Cs per leaf did not clearly increase

Relative number of leaves

in 2011] 1.2022; (R² = 0.7812, P < 0.001, n = 13), we estimated

1.4
1.2
1
0.8
0.6
0.4
0.2
0

<2

2–4

4–6

6–8 8–10 10–12 12–14 14–16 16–18

Leaf length class (cm)Fig. A4-3. Mean weight of Cryptomeria japonica var. japonica
leaves in each leaf length class.
Leaf-bearing branches of several trees were collected
in November 2016 in Iwaki and combined. □, currentyear leaf; ⊠ , 1-year-old leaf; ■, 2-year-old leaf.

104

2011 年福島第一原子力発電所事故後 5 年間の、福島県のスギ（Cryptomeria japonica var. japonica）の花粉セシウム 137 濃度
1）

2）

3）

4）

5）

清野 嘉之 *、赤間 亮夫 、金指 達郎 、志知 幸治 、近藤 禎二 、
6）
5）
7）
8）
星 比呂志 、倉本 哲嗣 、藤澤 義武 、倉本 惠生
要旨
花粉飛散前のスギ（Cryptomeria japonica var. japonica）雄花の測定値をもとに、スギ花粉により再飛散される放射性セシウムの量を的確に推定するため、2011 年の東京電力福島第一原子力発電所事故の影響下にあるスギについて、花粉の完成直後（11 月）と飛散直前（翌年 2 月）の雄花と花粉の質量、セシウム 137（ 137Cs）濃度を調べた。郡山市のスギ林では 11 月の雄花質量の約 1/3 が花粉で、雄花と花粉の 137Cs 濃度に有意差はなかった。得られた雄花と花粉の関係を、福島県内の 21 か所で 2011–2015 年の毎年 11–12 月に得たスギ雄花の測定値にあてはめ、花粉 137Cs 濃度を推定した。スギ花粉
137
Cs 濃度は年々低下し、2012 年春と比べ 2016 年春の濃度は約 8% であった。文部科学省の 137Cs 沈
着量の分布マップを利用して求めた、環境からスギ花粉への 137Cs 面移行係数は 2012 年 2 月が 0.0203
m 2 dry kg -1、2016 年 2 月は 0.00168 m 2 dry kg -1 であった。
キーワード： 沈着、分布マップ、雄花、生物季節、放射性セシウム、面移行係数、花粉量年変化

原稿受付：令和元年 8 月 13 日 原稿受理：令和元年 12 月 18 日
1）森林総合研究所 植物生態研究領域
2）森林総合研究所 震災復興・放射性物質研究拠点
3）元森林総合研究所
4）森林総合研究所 四国支所
5）森林総合研究所 林木育種センター
6）元森林総合研究所 林木育種センター
7）鹿児島大学
8）森林総合研究所 森林植生研究領域* 森林総合研究所 植物生態研究領域 〒 305-8687 茨城県つくば市松の里 1
森林総合研究所研究報告 第 19 巻 1 号, 2020