ACG22-P01

Japan Geoscience Union Meeting 2016

Sap flow measurement for Japanese cedar throughout the year with three techniques andrelated problem*Shin'ichi Iida1, Shin'ichi Takeuchi2, Takanori Shimizu1, Koji Tamai1
1.Department of Soil and Water Conservation, Forestry and Forest Products Research Institute,
2.Minami Kyushu University
Forests cover about 66% of land area of Japan, and Japanese cedar (Cryptomeria japonica) occupies
18% of total forested area. In Kyushu Island, south-western part of Japan, the water balance ofJapanese cedar stand has been made clear quantitatively by using eddy-covariance method and sap
flow technique (Kumagai et al., 2014; Shimizu et al., 2015). Meanwhile, except these studies, very
few measurements of sap flow have been carried out throughout the year, although Japanese cedar isthe most representative planted species in the larger part of Japan. Recently, newly developed
techniques, that is heat ratio method (HRM, Burgess et al., 2001) and heat field deformation method(HFD, Nadezhdina et al., 2012), have been available in Japan. Considering the background mentioned
above, we preliminarily compared these new methods with traditional thermal dissipation method(TDM, Granier, 1985) for a mature Japanese cedar planted at the central part of Japan. (Iida etal., 2015a). In this study, we show the results of measurement with HRM, HFD and TDM throughout theyear. And we point out the common problem of three techniques: calculated sap flow becomes smallerwhen a single sensor is used for relatively long period (i.e., more than 10 months).
We conducted measurements in a mature stand of Japanese cedar, whose age is 63, within Tsukuba
Experimental Watershed located in southern part of Mt. Tsukuba, Japan. We picked up a tree ofJapanese cedar whose height is 24.9 m and diameter at breast height is 40.4 cm, and installed
sensors of TDP, HRM and HFD. We used handmade sensors for TDM (e.g., Iida et al., 2015b) andsensors for HRM and HFD manufactured by ICT international Pty Ltd (type SFM1 and HFD8,
respectively). The length of TDM sensor was 20 mm, and the sap flux density was computed as meanvalue along the sensor length by the calibration equation proposed by Granier (1985). The width ofsapwood was 44 mm, and additional TDM sensor was inserted into the sapwood at the depth from 20 to
40 mm. On the other hand, the length of HRM sensor was 35 mm, and the sap flow movement was
detected at the depths of 12.5 and 27.5 mm. For HFD, the sensor length was 96 mm, and the depths ofsap flow detected were 20, 30, 40, 50, 60, 70, 80 and 90 mm.
The values of sap flux density by HFD showed high correlation with vapor pressure deficit (VPD).
Generally, conifer canopy has large aerodynamic conductance due to the needle leaf, and therefore
has high coupling with the ambient air. Thus, the high correlation with VPD is reasonable. Similar
trends were confirmed for TDP and HRM. However, the relationships changed with time, and sap flux
densities had become gradually smaller since the sensor installation. The clear deterioration was
found at 10-months after the installation, in common to TDP, HRM and HFD. This may be induced bywounding or air embolism, which cause disruption in water flow around the sensors (e.g., Moore etal., 2010). Therefore, to obtain the whole-year dataset of sap flow, attentions must be paid forany deteriorations by checking the relationships between sap flow and VPD.
Cited paper
Burgess, 2001. Tree Physiol., 21:589–598.
Granier, 1985. Ann. Sci. For., 42: 193–200. [English translation, in Evaporation, Benchmark Papers
in Hydrology 2. Gash JHC, Shuttleworth, WJ (eds). IAHS Press: Oxfordshire; 61–63].
Iida et al., 2015a. Japan Geoscience Union Meeting 2015, ACG30-P05.
Iida et al., 2015b. Ecohydrology, DOI: 10.1002/eco.1650.
Kumagai et al., 2014. J. Hydrol., 508: 66-76.

©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Moore et al., 2010. Trees, 24:165-174.
Nadezhdina et al., 2012. Trees, 26:1439–1448.
Shimizu et al., 2015. J. Hydrol., 522: 250-264.
Keywords: Japanese cedar, vapor pressure deficit, deterioration of detecting sap flow

©2016. Japan Geoscience Union. All Right Reserved.

- ACG22-P01 -ACG22-P02

Japan Geoscience Union Meeting 2016

Model-based analysis of tree-ring growth phenology in Picea glehnii forests on Hokkaido
Island, Japan*Dai Koide1, Akihiko Ito1
1.National Institute for Environmental Studies
Recent global change is predicted to broaden uncertainty of ecosystems especially in terrestrial
area. To reduce such uncertainties, tree-ring data is recently paid attention. Tree-rings have highpotential to examine terrestrial carbon fluxes since tree-rings intrinsically correlate with forest
carbon gains and stocks. A long observation time-span (decades to centuries) of tree-rings also
increases its potential, extending observation period beyond fundamental flux-tower carbon
observation (two or three decades). However, annual tree-rings are not simply in proportion to theannual sum of forest production. Annual tree-rings are made in a short time-span (e.g. two to threemonths) and such growing season's production is important for tree-rings though such growing season
is still not clearly determined in ecosystem models for many tree species. This insufficienttree-ring growth phenology scheme has prohibited ecosystem modelers to use tree-ring data forvalidation though it has high potential to reveal spatiotemporal carbon stocks. Therefore, thisresearch aims at revealing tree-ring growth phenology in conifer-hardwood mixed forests on Hokkaido
Island, Japan.
Seven tree-ring site data of Sakhalin spruce (Picea glehnii) on Hokkaido Island were obtained fromthe International Tree-Ring Data Bank. At each site, mean chronology was calculated in BAI (basal
area increment). Long-term climate data were obtained from the ERA20C reanalysis data (1900–2010)
with downscaling and bias correction using random forest modeling and Automated Meteorological Data
Acquisition System (AMeDAS) data on Hokkaido Island. Eight climatic parameters were used toconstruct the Vegetation Integrated SImulator for Trace gasses (VISIT) model. Flux data in Teshio
flux tower site was used to modify the VISIT model. Net primary production (NPP) in each tree-ringsite was predicted using the modified VISIT model and the downscaled ERA20C data. Predicted daily
NPP were summed up for various periods (from a month to seven months at two weeks intervals) and invarious temporal timings (at two weeks intervals). To analyze the most effective NPP period for BAI
explanation, correlations between BAIs and the sum of each NPP period were calculated with random
factor of sites and years and the best generalized linear mixed model was selected using the
Akaike's information criterion (AIC).
Model selection revealed that a model using the sum of NPP from day of year 43 to 183 was the bestmodel. This period contains tree-ring growing season (June) for Picea glehnii and other top models
whose AIC differences from the best model were less than two also contained this season, suggesting
importance of production in the tree-ring growing season. However, onset of the effective NPP
period varied from January to May among these top models.
This research revealed that NPP in the tree-ring growing season is an important factor fortree-ring width variations. Although this analysis aimed at clarifying mean growth phenology among
seven sites, differences in growth phenology among sites is expected to be a potential source ofwide variance in the timing of onset. Although tree-ring growth phenology is difficult to observe,
this research suggests that the growth phenology can be estimated from statistical analysis between
tree-ring and NPP, which connects to a next step toward tree-ring-based validation of ecosystemmodels to reduce terrestrial ecosystem uncertainties.
Keywords: Process-based ecosystem model, VISIT, Phenology, Conifer-hardwood mixed forest,
Allocation©2016. Japan Geoscience Union. All Right Reserved.

- ACG22-P02 -ACG22-P02©2016. Japan Geoscience Union. All Right Reserved.

Japan Geoscience Union Meeting 2016

- ACG22-P02 -ACG22-P03

Japan Geoscience Union Meeting 2016

Role of understory vegetation on net ecosystem exchange of water and CO2 at larch forest
in eastern Siberia*Ayumi Kotani1, Takeshi Ohta1
1.Graduate School of Bioagricultural Sciences, Nagoya University
This study investigated evapotranspiration (ET) and CO2 exchange over larch-dominated forests inthe middle part of the Lena basin, eastern Siberia. Forest ecosystem in this region ischaracterized by low precipitation, a short growing season, and extensive permafrost. Seasonal
thawing permafrost supplies soil water, which is prevented to infiltrating by an impermeable frozen
layer, and supports forest development. Recently, expanding summer thawing depth and unusually wet
soil layer maintained for a few years at larch forest observation sites caused decline of larchtrees (Iijima et al, 2014) and would have affected the water and carbon flux of ecosystem scale(Ohta et al., 2014). To investigate vulnerability of the larch dominant forest faced to too wet
condition, we analyzed water and CO2 fluxes observed with eddy covariance methods inside and overthe forest from 2004 to 2013.
The study site is the Spasskaya Pad station (62° 15´N, 129° 14´E) on alluvial terrace near Yakutsk.
The mean annual air temperature and mean annual precipitation (1986–2004) at this site were −9 ºC
and 256 mm, respectively. In tower site, soil water of active layer is high after unusually highprecipitation (compared with the previous 20-year average) in two successive summers, and soil
layer close to the ground surface was almost saturated around 2007-2009. The dominant species of
the upper canopy is larch (Larix cajanderi), while development of birch (Betula platyphyila) andwillow (Salix bebbiana) is remarkable during this decade. The understory was covered with dense
cowberry (Vaccinium vitis-idaea). Through the wet period, 19 of 212 larch trees on 2500 m2 area
became dieback, and grasses and shrubs with a high water tolerance have invaded this site.
A decadal observation of hydro-meteorological variables shows inter-annual variability including
extreme environmental conditions such as unusually wet active layer, which was maintained for a few
years. Some mature larch trees locating poor drainage area suffered wet damage, while young birch
and willow trees developed and herbs with water tolerance expanded. Compared to the fluxes of thewhole ecosystem, those based on the understory layer changed through the study period due toincrease biomass and change of inside canopy environments; plentiful light and soil water, andenhanced turbulent mixing. Evapotranspiration from the understory layer increased and contribution
to the whole forest flux reached 60%. Although this layer always acts as CO2 source in seasonal
average through the study period, source strength weaken and changed to temporal sink in the earlysummer (June). On contrast, contribution of the larch layer, in spite of remaining uncertainty inquantity, decreased in both of evapotranspiration and CO2 uptake. Interactions between larches andunderstory vegetation would support this forest ecosystem. Decline of larch contribution is made up
by understory growing, resulting in relatively stable whole forest exchange rate at least until
this wet event.
Acknowledgment:
Observation data used in this study was provided by Y. Iijima (Japan Agency for Marine-Earth
Science and Technology) and T. C. Maximov (Institute for Biological Problems of Cryolithzone).
Reference:
Iijima et al., 2014. Sap flow changes in relation to permafrost degradation under increasing
precipitation in an eastern Siberian larch forest. Ecohydrology 7, 177–187.
Ohta et al., 2014. Effects of waterlogging on water and carbon dioxide fluxes and environmental
variables in a Siberian larch forest, 1998-2011. Agric. For. Meteorol. 188, 64-75.

©2016. Japan Geoscience Union. All Right Reserved.

- ACG22-P03 -ACG22-P03

Japan Geoscience Union Meeting 2016

Keywords: boreal forest, water and carbon cycle, eddy covariance methods©2016. Japan Geoscience Union. All Right Reserved.

- ACG22-P03 -ACG22-P04

Japan Geoscience Union Meeting 2016

Factors affecting global distribution of soil carbon in observational datasets and Earthsystem models*Shoji Hashimoto1
1.Forestry and Forest Products Research Institute
Soil is the largest carbon stock in the terrestrial ecosystem. Therefore, understanding soil carbon
dynamics is essential to predict future climate change. In the last two decades, several global
soil datasets have been developed, and some are under further improvement. These datasets containthe global distributions of soil physiochemical properties, which allow us to calculate the global
distribution of the soil organic carbon (SOC) stock, and some datasets provide the SOC stock bydefault. These datasets are based on globally observed data points, although there are biases inspatial distribution and densities of some data points. Earth system models (ESMs) have beencreated to understand the current climate and project future climate conditions. These models
incorporate the terrestrial carbon cycle including SOC. However, it was reported that ESM results
agree moderately at the biome level but that the correlation between the distribution of the SOC
stock simulated by the ESMs and that of observational datasets is poor when the two were comparedat a fine scale (e.g., 1° scale). In this study, we identified key factors governing global SOC
distribution in observational datasets and those simulated by ESMs. We applied a data mining scheme
and boosted regression trees to identify influential factors and how these factors are related to
the SOC stock (Elith et al., 2008). We revealed similarities and differences between theobservational and ESM datasets after comparing their outputs. The results of this study will be
useful to understand the nature of observational SOC datasets and ESM outputs to improve theterrestrial carbon dynamics model in ESMs.
Keywords: Soil carbon, Dataset, Earth system model©2016. Japan Geoscience Union. All Right Reserved.

- ACG22-P04 -ACG22-P05

Japan Geoscience Union Meeting 2016

Estimation of understory carbon budget and environmental factors influencing on theprocesses in a larch forest on the northern foot of Mount Fuji
*Munemasa Teramoto1, Naishen Liang1, Jiye Zeng1, Reiko Ide1, Nobuko Saigusa1
1.National Institute for Environmental Studies
Forest ecosystem is very important component of terrestrial ecosystems, and elucidating the carbon
cycle mechanism in forest ecosystem is vital for understanding global carbon cycle and predicting
future carbon budget along with global climate change. There are many studies reported carbon
budget of specific forest ecosystem using eddy-covariance method, however, this technique cannot
provide detailed information about each process of forest carbon cycle. Especially, information
about understory carbon budget include understory vegetation is limited.
To understand the impact of forest understory carbon budget and environmental factors influencing
on processes of understory carbon cycle, we set multi-channel automated chamber measurement system
in larch forest on northern foot of Mt. Fuji in 2006. The control unit of chamber system mainly
consisted of a data logger (CR1000, Campbell Scientific), an infrared gas analyzer (LI820, LI-COR)
and an air compressor. We set soil chambers (90 cm ×90 cm ×50 cm) for soil CO2 flux measurement.
Surroundings of the half of those soil chambers were root cut with chainsaw until 25 cm depth forthe measurement of heterotrophic respiration (Rh), and the remaining control chambers were used forsoil respiration (Rs) measurement. We also set plant chambers (90 cm ×90 cm ×100 cm) which included
understory vegetation to measure understory net CO2 exchange (NUE), understory respiration (Ru) andunderstory gross primary production (GPP_u).
We got continuous data for 8 years from 2006 to 2013 with chamber measurement method. Comparison
with eddy-covariance data showed that annual Ru accounted for 68.6% of annual ecosystem
respiration, and annual GPP_u accounted for 16.3% of annual gross primary production of the larch
forest. Primary factor for GPP_u was light intensity of forest understory, and positive correlation
between annually estimated GPP_u and annual average of understory PPFD (R2 = 0.64) was confirmed.
Remarkable exponential correlations between soil temperature and Rs, Rh and Ru were observed, andtotal Q10 values for Rs, Rh and Ru were 2.49, 2.57 and 2.25, respectively. On the other hand,
influence of soil moisture on those soil CO2 fluxes were minor except summer season when soil
moisture was notably decreased due to few rainfall.
Keywords: Understory carbon budget, CO2, Chamber, Soil respiration, Larch forest©2016. Japan Geoscience Union. All Right Reserved.

- ACG22-P05 -ACG22-P06

Japan Geoscience Union Meeting 2016

Initial results of observations of soil CO2 and CH4 fluxes in three ecosystem types oftropical peatland in Sarawak, Malaysia*Ryuichi Hirata1, Yosuke Okimoto2, Takashi Hirano2, Frankie Kiew2,3, Lulie Melling3
1.National Institute for Environmental Studies, 2.Research Faculty of Agriculture, Hokkaido
University, 3.Tropical Peat Research Laboratory Unit
Tropical peatlands in Southeast Asia store large carbon by accumulating peat and they arevulnerable to climate change and human disturbances.
Soil carbon dioxide (CO2) and methane (CH4) fluxes observations were started on September 2015 at
three ecosystem types of tropical peatland in Sarawak, Malaysia. The sites were one tropical swamp
forest with high ground water level and one with low ground water level, and an oil palm plantationon peat. In each site, we installed an automated multi-chamber system. We will present the initial
results of the observations.
Keywords: Automated multi-chamber system, peat swamp forest, oil palm

©2016. Japan Geoscience Union. All Right Reserved.

- ACG22-P06 -ACG22-P07

Japan Geoscience Union Meeting 2016

Change of CO2 flux during an early secondary succession after severe forest disturbance*Takashi Hirano1
1.Research Faculty of Agriculture, Hokkaido University
Forest ecosystems are expected as a major sink of atmospheric carbon dioxide (CO2), whereas theirability to absorb CO2 is severely perturbed by disturbances, such as deforestation, fires,
windthrow etc. Many studies which adopted the chrono-sequence approach reported that such severe
disturbances often changed forest to be a CO2 source. However, there are few studies that directly
measure CO2 flux for a long term (more than 10 years) above a disturbed forest site during an earlystage of secondary succession after severe disturbance.A flux site of a larch plantation in
Tomakomai, Hokkaido, Japan was struck by a typhoon in September 2004. Because of wind storm, about
90% of trees fell down. The fallen trees were removed by heavy machinery from the site, throughwhich the soil surface and understory species were also disturbed. After the operations of timbertransport, secondary succession progressed naturally in the ex-forest site. We recommenced flux
measurement in August 2005. CO2 flux has been measured by the eddy covariance technique with an
open-path CO2 / H2O analyzer (LI7500, Licor) during a snow-free period from mid-April to
mid-November. Cumulative net ecosystem CO2 exchange (NEE) during the snow-free period was positive
every year until 2015, whereas it showed a negative relationship, which indicates that the CO2
source strength of the ecosystem decreased. This negative relationship was caused by the increaseof gross primary production (GPP) or ecosystem photosynthesis, which corresponded to vegetation
recovery through secondary succession.
Keywords: Windthrow, Eddy covariance, Vegertation recovery©2016. Japan Geoscience Union. All Right Reserved.

- ACG22-P07 -ACG22-P08

Japan Geoscience Union Meeting 2016

Influence of natural and human disturbances on long-term CO2 exchange over larch forests*Yoshiyuki Takahashi1, Nobuko Saigusa1, Ryuichi Hirata1, Naishen Liang1, Reiko Ide1, Kentaro Takagi2, Takashi Hirano3
1.Center for Global Environmental Research, National Institute for Environmental Studies, 2.The
Field Science Center for Northern Biosphere, Hokkaido University, 3.Graduate School of Agriculture,
Hokkaido University
Larch forest is an important research object for evaluating ecosystem response against future
global warming because it is a representative vegetation type for high latitudinal northeast
Eurasia where greater temperature rise due to climate change is anticipated. In Japan, Larch is acommon tree type of plantation that has been planted widespread over northeastern Japan especiallyafter World War II. However, many larch forests have been left unmanaged because of the sluggish
lumber demand. Quantifying the influence of the forest management on carbon budget in larch forests
has significance on the securement of forests as a source of CO2 absorption.
Thus, National Institute for Environmental Studies (NIES) has implemented long-term monitoring
program of CO2 exchange over three domestic larch forests in association with Hokkaido University.
We established the Fuji Hokuroku Flux Observation Site in the foothills of Mt. Fuji as analternative base for monitoring, and began observations in January 2006. The site is dominated bylarch trees of more than 50 year-old. 30% thinning was conducted at the site in spring of year
2014. Tomakomai Flux Research site was established in 1999 to carry out integrated monitoring on
the carbon budget in a mature larch forest. However, the site was devastated by the typhoon in
2004. Flux observation at the site is ongoing after the typhoon disturbance.
We began observations of the effects of canopy opening on a larch forest ecosystem structure in2001 at a mixed forest in Teshio experimental forest of Hokkaido University. The forest was
clear-cut and planted with larch trees in 2003. We monitor and evaluate the changes in carbon
budget and forest ecosystem structure. Those three observation sites were affected from different
kinds of natural and human disturbance. We will introduce the comparison results of carbon fluxes
and related parameters for the sites.
Keywords: CO2, flux, disturbance, larch, monitoring©2016. Japan Geoscience Union. All Right Reserved.

- ACG22-P08 -ACG22-P09

Japan Geoscience Union Meeting 2016

Forest resources change observation using spaceborne LiDAR in Siberian*Masato Hayashi1, Kazuhito Ichii2,1, habura borjigin1, Nobuko Saigusa1, Yoshito Sawada1, Yoshiki
Yamagata1
1.National Institute for Environmental Studies, 2.Japan Agency for Marine-Earth Science andTechnology
High-latitude area in the northern hemisphere, including Siberia, is the region most affected byclimate change. A monitoring technology for vegetation change is very important for such region.
Satellite remote sensing can provide the most practical mean for the large-scale and continuous
observation, and spaceborne LiDAR is particularly expected. This sensor transmits a laser pulse tomeasure vertical structure near the Earth’s surface. ICESat/GLAS was the only spaceborne LiDAR sofar, which was operated by NASA from 2003 to 2009. However, there are some future plans ofspaceborne LiDAR, such as ICESat-2, GEDI, and MOLI, and they are expected to be used for forest
monitoring. This study aims to clarify the potential of spaceborne LiDAR to quantitatively observe
forest resources change in Siberia. We collected GLAS data acquired in 40°N-90°N and 60°E-170°W.
Then, we excluded some GLAS data as follows: 1) the data in cloud covered area or non-forested
area, 2) the data with large noise (SNR of GLAS waveform < 10), and 3) the data in steep slopedarea (surface slope > 5°). As a result, we obtained about 3,000,000 points GLAS data suitable forthe analysis. Next, we estimated canopy height and aboveground biomass from each of GLAS waveform
data. We adopted RH100 (height from signal start to ground peak) for canopy height and an existingmodel (Neigh et al., 2013) for aboveground biomass. As a result, the average values were 7.4m of
canopy height, and 23.0 Mg ha-1 of aboveground biomass in the whole study area. Next, we calculated
the average of canopy height and aboveground biomass for every 5° longitude and latitude mesh, tounderstand the spatial distribution of forest resources. The spatial distributions of canopy height
and aboveground biomass showed similar pattern, which was high in the south and low in the north ingeneral. And, we separated the estimates data into the two period according to the GLAS observation(2003-2005 and 2005-2007), to understand the yearly change. As a result, canopy height showed aslightly decreasing trend, and aboveground biomass showed alomost no change, however, an increasing
trend was seen in the western region (see figure). For the future, we will investigate the cause ofthis trend. This study showed that spaceborne LiDAR is suitable for monitoring the forest resourceschange accurately.
Keywords: Forest biomass, Spaceborne LiDAR, ICESat/GLAS, Siberia©2016. Japan Geoscience Union. All Right Reserved.

- ACG22-P09 -ACG22-P09©2016. Japan Geoscience Union. All Right Reserved.

Japan Geoscience Union Meeting 2016

- ACG22-P09 -ACG22-P10

Japan Geoscience Union Meeting 2016

Phenological changes for 10 years and the influence on ecosystem productivity in a larch
forest at the foot of Mt. Fuji
*Reiko Ide1, Hiroyuki Oguma1, Yasuo Hirose1, Yoshiyuki Takahashi1, Nobuko Saigusa1
1.National Institute for Environmental Studies
Phenological changes such as earlier budding or flowering and later leaf coloring and leaf fall
have been reported around the world along with recent global warming. Phenology is an important
index for climate change, and is also one of valuable factors to regulate the carbon cycle interrestrial ecosystems. As the phenological responses to environment vary across species,
assessment of long-term phenological trend for each species is required. In this study, weinvestigated the phenology of a Japanese larch forest by near-surface remote sensing, and analyzed
the relationship between the phenology and climate change and also the influence of phenology on
the forest ecosystem productivity derived from CO2 flux observation.
Our study was conducted in a larch plantation at Fuji-hokuroku flux observation site (Fujiyoshidacity, Yamanashi). About 87 % of the canopy is dominated by 60-year-old Japanese larch (Larix

kaempferi) and the maximum LAI of the canopy was 3.2 m2 m-2 in 2012. CO2 flux and micro
meteorological factors have been measured by eddy covariance method for ten years since 2006. For
phenological observation, reflectance from the canopy has been continuously observed on theobservation tower by using two spectral radiometers (upward and downward) and digital cameras. The
vegetation index to detect seasonal changes of the canopy greenness was calculated as Green Ratio:
GR=G/(R+G+B). The start and end dates of the growing season were determined from the days when thetime series of GR indicated the maximum rate of increase and decrease. Then relationships of theyearly variations of phenology, temperature, net ecosystem exchange (NEE) and gross primary
production (GPP) were analyzed.
As results, the mean dates of start and end of growing season were Apr. 23 and Nov. 8, with large
amplitudes of 12 and 8 days respectively. Significant earlier or later phenological trend was notfound across these ten years from 2006 to 2015. The mean annual growing season length was 198.5±4.1
days. The start and end dates were significantly related to the mean temperature respectively
during Mar.-Apr. and during Sep.-Oct. The phenological responses to temperature were −4.5 day/ºC (R2= 0.88) in spring and 2.3 day/ºC (R2 = 0.74) in autumn. In addition, the influences of phenology
on GPP and NEE during spring (Apr. and May) and autumn (Oct. and Nov) were indicated. Meanwhile,
yearly variations in annual GPP and NEE were more influenced by the decrease of summer
productivities due to thinning and typhoon than phenological factors.
Keywords: Phenology, Growing season, Climate change, Carbon cycle, GPP©2016. Japan Geoscience Union. All Right Reserved.

- ACG22-P10 -ACG22-P11

Japan Geoscience Union Meeting 2016

Sun-induced chlorophyll fluorescence reveals strong representativeness of ecosystem-level
photosynthesis in rice paddy field in Mase Japan*Tomomichi Kato1, Katsuto Tsujimoto2, Kenlo Nasahara3, Tomoko Akitsu3, Keisuke Ono4, Akira Miyata4
1.Research Faculty of Agriculture, Hokkaido University, 2.Graduate School of Agriculture, Hokkaido
University, 3.Faculty of Life and Environmental Sciences, 4.National Institute forAgro-Environmental Sciences
Chlorophyll fluorescence emission from ecosystem induced by sunlight (Sun-Induced Fluorescence:SIF) is now a key factor to accurately estimate the ecosystem-level photosynthesis activity as
suggested by satellite studies, and has been recently detected by satellites [Frankenberg et al.,2011; Guanter et al., 2012; Joiner et al., 2013] and measured at field stations [Daumard et al.,2010; Porcar-Castell, 2011]. However, the few example of field-based assessment on the
representation ability reduces its value for the availability to better understand the dynamics in
CO2 uptake by land ecosystem.
To elucidate the potential of SIF to estimate ecosystem GPP in typical Asian crop type, thecanopy-top SIF was calculated from the spectrum data in Japanese rice paddy field in Mase incentral Japan (36°03′N, 140°01′E, 11 m a.s.l.), and compared with eddy-tower measured GPP on
half-hourly and daily bases during seven years from 2006 to 2012. The rice (Oriza sativa L.;
cultivar Koshihikari) was transplanted in May and harvested in September normally. The SIF wasestimated from the spectrums of downward Sun irradiance and upward canopy-reflected irradiancemeasured at the height of 3m above ground by HemiSpherical Spectro-Radiometer (HSSR), consisting of
the spectroradiometer (MS-700, Eko inc., Tokyo, Japan) with the full-width at half maximum (FWHM)
of 10 nm and wavelength interval of 3.3 nm. The SIF around 760nm (O2-A band: SIF760) was calculated
according to the Fraunhofer Line Depth principle [Maier et al., 2003] with several additionalarrangements.
The GPP increased almost linearly as both SIF760 and APAR (Absorbed Photosyntethically Active
Radiation) increased based on monthly-averaged diurnal courses during the growing season in 2006.
The slopes of their regression lines differed much among the months in APAR, but in SIF760. Thesenearly constant relationships among the months between GPP and SIF760 were kept for all theobservation years. Daily averaged GPP and SIF760 indicated similar seasonality for multiple years
although the conventional vegetation indices, NDVI and EVI, showed the smoothed temporal variations
but with longer maximum period than GPP showed. Thus, those strong relationships of SIF to GPP
confirmed that the SIF is a quite useful proxy of ecosystem-level photosynthesis in the rice paddy
field.
Keywords: spectroradiometry, remote sensing, carbon cycle©2016. Japan Geoscience Union. All Right Reserved.

- ACG22-P11 -