Conference paper
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-7, 2014
ISPRS Technical Commission VII Symposium, 29 September – 2 October 2014, Istanbul, Turkey
A CONSIDERATION FOR THE LIGHT ENVIRONMENTAL MODELING UNDER
TROPICAL RAINFOREST CANOPIES
M. Yoshimura a, , M. Yamashita c
a
b
PASCO Corporation, PASCO Research Institute, 2-8-10 Higashiyama, Meguro-ku, Tokyo, Japan -gr4m-ysmr@asahi-net.or.jp
Tokyo University of Agriculture and Technology, Faculty of Agriculture and Women's Future Developing Organization, 3-5-8
Saiwai-cho, Fuchu, Tokyo, Japan -meguyama@cc.tuat.ac.jp
Commission VII, WG VII/1
KEY WORDS: Light environment, representativeness, PAR, fluctuating, sky condition, characterization
ABSTRACT:
Photosynthetic Active Radiation (PAR) is the most important light source for plant photosynthesis. It is known that most of PAR
from solar radiation is well absorbed by the surface. The canopy is the surface in forest region, consists an aboveground portion of
plant community and formed by plant crowns. On the other hand, incident solar radiation is fluctuating at all times because of
fluctuating sky conditions. Therefore, qualitative light environmental measurements in forest are recommended to execute under
stable cloudy condition. In fact, it is quite a few opportunities to do under this sky condition. It means that the diffuse light condition
without the direct light is only suitable for this measurement.
In this study, we challenged the characterization the forest light environment as its representativeness under no consideration of sky
conditions through analysis huge quantities of instantaneous data which obtained under the different sky conditions. All examined
data were obtained under the different sky conditions at the tropical rainforest canopy as one of the typical fluctuating sky conditions
regions. An incident PAR is transmitted and scattered by different forest layers at different heights. Various PAR data were
measured with quantum units as Photosynthetic Photon Flux Density (PPFD) at different forest heights by the quantum sensors. By
comparing PPFDs at different heights with an incident PPFD, relative PPFDs were calculated, which indicate the degree of PPFD
decrease from the canopy top to lower levels. As the results of these considerations, daily averaging is confirmed to be cancelled sky
fluctuating influences.
1. INTRODUCTION
2. SITE
Remote sensing is only one powerful tool to expand the plant
physiological model-based approach spatial-dimensionally.
However it is still remained many technical and theoretical
issues to be solved. Photosynthetic Active Radiation (PAR),
which is solar radiation in the wavelength range from 400 to
700 nm, is the most important for plant photosynthesis at
different forest height (Kenzo et al., 2006). It is known that
most of PAR is well absorbed by the surface and only a little is
reflected. In biology, this surface is the canopy. The canopy is
an aboveground portion of plant community and formed by
plant crowns. On the other hand, incident solar radiation is
fluctuating at all times because of fluctuating sky conditions
(Yamashita and Yoshimura, 2009). Therefore, the light
environmental measurements in forest have been recommended
to execute under stable cloudy condition. In fact, it is quite a
few opportunities to do under cloudy condition only, especially
in tropical rainforest climate zone. It makes difficult to
understand the representativeness of the light environment in
tropical rainforest (Yoshimura and Yamashita, 2012).
In this study, we focus on the influence of fluctuating sky
conditions to the diurnal and daily changes in the forest light
environment, and we measure the incident PAR on the top of
canopy and the transmissive PAR with quantum units as
Photosynthetic Photon Flux Density (PPFD) at different forest
height under tropical rainforest canopy on diverse sky
conditions. The relationships between relative PPFD and forest
height are examined with averaging in a short time period and
one-day. Then we consider the time representativeness of the
forest light environment under different weather conditions.
Our research site is the tropical rainforest in Lambir hills
national park and the western part of Sarawak state, Borneo
Island, Malaysia (fig.1). This region is known as the typical
tropical weather region without seasonal change. The tropical
rainforest also is known as the lug of the earth or the treasury of
biodiversity.
The canopy access crane had constructed in March 2000. This
crane is about 80m tall height with 75m arm length
(Nakashizuka et al., 2003). Using the gondola of this crane, it
can make us possible to access to any point three-dimensionally.
10ﾟ
N
Lambir Hills National
Park
MALAY
PENINSULA
BORNEO
(KALIMANTAN)
0゜
SUMATRA
100゜E
110゜E
120゜E
Fig.1 Study site and the canopy access crane
This contribution has been peer-reviewed.
doi:10.5194/isprsarchives-XL-7-217-2014
217
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-7, 2014
ISPRS Technical Commission VII Symposium, 29 September – 2 October 2014, Istanbul, Turkey
3. LIGHT DISTRIBUTION IN FOREST
Incident solar radiation proceeds from the top of the canopy to
the forest floor, and consists of three components. The first is
direct radiation, which penetrates the top of the canopy into the
forest. The second is diffuse radiation, which is reflected from
leaf or ground surfaces. The third is transmissive radiation,
which penetrates leaves.
Attenuation of solar radiation is the sum of the three
components. Radiation which penetrates the forest is modelled
using the Lambert–Beer law, which is expressed in eq.1.
According to the Lambert–Beer law, light intensity decays
exponentially with Leaf Area Index (LAI). Solar radiation at
any height in the forest, I, is defined by eq.1 from the incident
solar radiation at the top of the canopy, I0, and the
corresponding LAI at that height. This equation applies to any
plant species. Photosynthetic Photon Flux Density (PPFD,
quantum units: mol/m2/s) is used normally to represent
radiation in this kind of analysis. The PPFD is also expressed by
PAR. Most incident PAR penetrates leaves and is absorbed
effectively by photosynthesizing pigments such as chlorophyll.
I / I0 = exp (− k (LAI))
(1)
where I0 is the incident PAR at the top of canopy, I is
transmissive PAR and k is the coefficient of light absorption,
and where:
relative PAR = I / I0
(2)
Light attenuation at any forest height is expressed by the
relative PPFD, which is shown in eq.2. This is the ratio between
incident and transmissive PPFD, and is calculated from PPFD at
a particular height compared with incident PPFD at the top of
the canopy (Lowman and Nadkarni 1995). The absorption
coefficient k expresses light absorption below the forest surface.
MkVL by Alec) was used. The quantum sensor was set up on
the top of the observation crane, unobscured by obstacles.
To monitor sky conditions and account for cloud effects on the
forest
light
environment
during
qualitative
forest
characterization, whole-sky images were captured with a
fisheye lens camera installed at the top of canopy.
4.2 Transmissive PPFD
Incident PPFD is transmitted and scattered by different forest
layers at different heights. Various PAR data were measured
with quantum units at different forest heights by the same
quantum sensors. By comparing PPFDs at different heights with
the standard PPFD, relative PPFDs are calculated which
indicated the degree of PPFD decrease from the canopy top to
lower levels.
Fig.3 shows the target canopy view and the quantum sensors’
horizontal and vertical distributions. The upper left figure shows
the incident PPFD measurement instruments’ view at the top of
the crane. The central upper figure shows the distribution of
four horizontal measurement points on our objective canopy. At
each point 1 to 4, 6 quantum sensors were placed at different
heights below the canopy; the upper right image is one of the
sensors’ views. The lower image depicts six vertical sensors’
distributions at four horizontal measurement points.
The S-25 sensor measured the standard PPFD at the top of the
canopy for calculation of relative PPFD.
Objective canopy of measurement
I ncident PPFD
Top of crane
Transmissive PPFD
Sensor at forest floor
S-25(Top of crane)
S-24(43.3m)
Canopy
S-20(36.6m)
4. MEASUREMENTS
S-23(36.9m)
S-22(34.5m)
The concept of our measurements for the light environment
under tropical rainforest canopy is shown in fig.2. The incident
and the transmissive PPFDs measurements are explained as
follows.
S-15(23.4m)
S-12(22.2m)
S-8(15.3m)
30m
S-18(27.5m)
S-14(22.2m)
S-10(20.2m)
S-11(16.2m)
S-7(11.1m)
S-4(8.2m)
S-3(1.1m)
I ncident PPFD
S-21(34.5m)
S-19(31.1m)
S-16(29.1m)
S-6(5.9m)
S-2(1.4m)
S-17(26.9m)
S-13(20.0m)
20m
S-9(12.7m)
10m
S-5(5.5m)
S-1(1.4m)
Forest floor
: Quantum Sensor
Fig.3 Distribution of target canopy and quantum sensors.
5. RESULTS
Canopy surface
about 40m
Transmissive PPFD
5.1 Time representative Consideration
4 vertical points
Below canopy
Forest floor
Fig.2 Concept of the forest light environmental measurements
4.1 Incident PPFD
The incident PPFD is observed for the standard for relative
PPFD calculation. To determine the standard of relative PPFD
calculation, a quantum sensor with ultra-small memory (MDS-
We observed the light environment under the tropical rainforest
canopies for 10 days from 29th August to 7th September in 2005.
The weather conditions were mixed by sunny and cloudy.
Here, we considered the time representativeness of light
environment under the canopies in our site. Fig.4 shows the
relative PPFD at 24 measurement points with one-day average
and 10-days average. Comparing with one-day and 10-days
averages, there is no big difference. Three exponential
approximations in fig.4 are derived from the relative PPFD of
1st Sep under cloudy condition, 5th Sep under sunny condition,
and 10-days under all weather conditions. There is also no
difference between sunny and cloudy days. In this way, it is
able to show the time representativeness of light environment in
the forest by averaging the one-day relative PPFD regardless of
the cloudy and sunny. Also, to derive the approximations as
This contribution has been peer-reviewed.
doi:10.5194/isprsarchives-XL-7-217-2014
218
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-7, 2014
ISPRS Technical Commission VII Symposium, 29 September – 2 October 2014, Istanbul, Turkey
exponential from the relations with relative PPFD with forest
height, that is, there is a linear relationship between forest
height and LAI in our study forest site.
of light environment in the forest by averaging the one-day
relative PPFD regardless of the cloudy and sunny. Furthermore,
we could recognize that the 30-minute average of relative PPFD
measured under cloudy condition has the adequate time
representativeness as minimum time requirement.
As the future works, we will develop the light environmental
modeling under the rainforest canopies by considering the
relationship between the forest height and LAI.
5.2 Time representativeness on weather Conditions
The incident and transmissive PARs under sunny condition are
easy changeable in short time period by clouds movement.
Therefore, we examined the minimum time requirement for the
time representativeness of the light environment under different
weather conditions.
Fig.5 and 6 show the 30-minute average of relative PPFD with
forest height at each measurement point observed on 29th Aug.
under sunny condition and 1st Sep. under cloudy condition
respectively. These exponentials are derived as approximations
from 30-minute averages at 24 measurement points. The
variation of relative PPFD at each measurement point and each
30-minute interval is very large especially more than 20 m of
the sensors’ height on sunny day (fig.5). On the other hand, we
cannot see the big differences between these measurement
points and between 30-minute intervals on cloudy day (fig.6).
From these results, we can recognize that the 30-minute average
of relative PPFD measured under cloudy condition has the
adequate time representativeness of the light environment in
forest.
REFERENCES
Kenzo, T., Ichie, T., Watanabe,Y.,Yoneda,R.,Ninomiya, I. and
Koike, T., 2006, Change in photosynthesis and leaf
characteristics with tree height in five dipterocarpaceae species
in a tropical rain forest. Tree Physiology, 26, pp. 865–873.
Lowman, D.M. and Nadkarni, M.N. (Eds.), 1995, Forest
Canopies (San Diego, CA: Academic Press).
Nakashizuka, T., Sakai, S. and CHONG, L., 2003, Lambir Hills
National Park canopy crane, Malaysia. In Studying Forest
Canopies from Above: the International Canopy Crane Network,
Y. Basset, V. Horlyck and S.J. Wright (Eds.), pp. 120–125
(Panama: Smithsonian Tropical Research Institute and UNEP).
6. CONCLUSION
To characterize the forest light environment as its
representativeness under no consideration of weather conditions,
we analysed huge quantities of instantaneous data which
obtained at the different measurement heights and under
weather conditions in the tropical rainforest.
Through the considerations related with the time
representativeness and weather conditions in the forest light
environment, we could understand the time representativeness
Yamashita, M. and Yoshimura, M., 2009, The Diurnal Global
and Diffuse PAR Change Analysis by Sky Conditions and its
Characteristics. Journal of Environmental Information Science,
Vol. 37, No.5, pp.7-14.
Yoshimura, M. and Yamashita, M., 2012, Measurement of
tropical rainforest three-dimensional light environment and its
diurnal change, International Journal of Remote Sensing, 33:3,
848-859.introduction
100%
8/29
y = 0.0135e0.087x
R² = 0.877
90%
8/30
8/31
80%
Relative PPFD
9/1
y = 0.0142e0.083x
R² = 0.868
70%
9/2
9/3
60%
9/4
y = 0.0147e0.083x
R² = 0.893
50%
9/5
40%
9/6
30%
9/7
10 days ave.
20%
Exponential (9/1)
指数 (9/1)
10%
Exponential (9/5)
指数 (9/5)
Exponential (10days)
指数 (10 days ave.)
0%
0
10
20
30
40
50
Hight (m)
Fig.4 Relations of the relative PPFD and forest height at each measurement points with one-day average and 10-days average.
This contribution has been peer-reviewed.
doi:10.5194/isprsarchives-XL-7-217-2014
219
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-7, 2014
ISPRS Technical Commission VII Symposium, 29 September – 2 October 2014, Istanbul, Turkey
100%
7.5‐ 8.0hAve
8.0‐ 8.5hAve
90%
8.5‐ 9.0hAve
9.0‐ 9.5hAve
80%
9.5‐10.0hAve
70%
10.0‐10.5hAve
10.5‐11.0hAve
Relative‐PPFD
60%
11.0‐11.5hAve
50%
11.5‐12.0hAve
12.0‐12.5hAve
40%
12.5‐13.0hAve
13.0‐13.5hAve
30%
13.5‐14.0hAve
20%
14.0‐14.5hAve
14.5‐15.0hAve
10%
15.0‐15.5hAve
0%
15.5‐16.0hAve
0
10
20
30
40
50
16.0‐16.5hAve
Height (m)
Fig.5 30-minute average of relative PPFD with forest height at each measurement point observed on 29th Aug. under sunny
conditions.
100%
7.5‐ 8.0hAve
8.0‐ 8.5hAve
90%
8.5‐ 9.0hAve
9.0‐ 9.5hAve
80%
9.5‐10.0hAve
70%
10.0‐10.5hAve
10.5‐11.0hAve
Relative‐PPFD
60%
11.0‐11.5hAve
50%
11.5‐12.0hAve
12.0‐12.5hAve
40%
12.5‐13.0hAve
13.0‐13.5hAve
30%
13.5‐14.0hAve
20%
14.0‐14.5hAve
14.5‐15.0hAve
10%
15.0‐15.5hAve
0%
15.5‐16.0hAve
0
10
20
30
40
Height (m)
50
16.0‐16.5hAve
Fig.6 30-minute average of relative PPFD with forest height at each measurement point observed on 1st Sep. under cloudy condition.
This contribution has been peer-reviewed.
doi:10.5194/isprsarchives-XL-7-217-2014
220
ISPRS Technical Commission VII Symposium, 29 September – 2 October 2014, Istanbul, Turkey
A CONSIDERATION FOR THE LIGHT ENVIRONMENTAL MODELING UNDER
TROPICAL RAINFOREST CANOPIES
M. Yoshimura a, , M. Yamashita c
a
b
PASCO Corporation, PASCO Research Institute, 2-8-10 Higashiyama, Meguro-ku, Tokyo, Japan -gr4m-ysmr@asahi-net.or.jp
Tokyo University of Agriculture and Technology, Faculty of Agriculture and Women's Future Developing Organization, 3-5-8
Saiwai-cho, Fuchu, Tokyo, Japan -meguyama@cc.tuat.ac.jp
Commission VII, WG VII/1
KEY WORDS: Light environment, representativeness, PAR, fluctuating, sky condition, characterization
ABSTRACT:
Photosynthetic Active Radiation (PAR) is the most important light source for plant photosynthesis. It is known that most of PAR
from solar radiation is well absorbed by the surface. The canopy is the surface in forest region, consists an aboveground portion of
plant community and formed by plant crowns. On the other hand, incident solar radiation is fluctuating at all times because of
fluctuating sky conditions. Therefore, qualitative light environmental measurements in forest are recommended to execute under
stable cloudy condition. In fact, it is quite a few opportunities to do under this sky condition. It means that the diffuse light condition
without the direct light is only suitable for this measurement.
In this study, we challenged the characterization the forest light environment as its representativeness under no consideration of sky
conditions through analysis huge quantities of instantaneous data which obtained under the different sky conditions. All examined
data were obtained under the different sky conditions at the tropical rainforest canopy as one of the typical fluctuating sky conditions
regions. An incident PAR is transmitted and scattered by different forest layers at different heights. Various PAR data were
measured with quantum units as Photosynthetic Photon Flux Density (PPFD) at different forest heights by the quantum sensors. By
comparing PPFDs at different heights with an incident PPFD, relative PPFDs were calculated, which indicate the degree of PPFD
decrease from the canopy top to lower levels. As the results of these considerations, daily averaging is confirmed to be cancelled sky
fluctuating influences.
1. INTRODUCTION
2. SITE
Remote sensing is only one powerful tool to expand the plant
physiological model-based approach spatial-dimensionally.
However it is still remained many technical and theoretical
issues to be solved. Photosynthetic Active Radiation (PAR),
which is solar radiation in the wavelength range from 400 to
700 nm, is the most important for plant photosynthesis at
different forest height (Kenzo et al., 2006). It is known that
most of PAR is well absorbed by the surface and only a little is
reflected. In biology, this surface is the canopy. The canopy is
an aboveground portion of plant community and formed by
plant crowns. On the other hand, incident solar radiation is
fluctuating at all times because of fluctuating sky conditions
(Yamashita and Yoshimura, 2009). Therefore, the light
environmental measurements in forest have been recommended
to execute under stable cloudy condition. In fact, it is quite a
few opportunities to do under cloudy condition only, especially
in tropical rainforest climate zone. It makes difficult to
understand the representativeness of the light environment in
tropical rainforest (Yoshimura and Yamashita, 2012).
In this study, we focus on the influence of fluctuating sky
conditions to the diurnal and daily changes in the forest light
environment, and we measure the incident PAR on the top of
canopy and the transmissive PAR with quantum units as
Photosynthetic Photon Flux Density (PPFD) at different forest
height under tropical rainforest canopy on diverse sky
conditions. The relationships between relative PPFD and forest
height are examined with averaging in a short time period and
one-day. Then we consider the time representativeness of the
forest light environment under different weather conditions.
Our research site is the tropical rainforest in Lambir hills
national park and the western part of Sarawak state, Borneo
Island, Malaysia (fig.1). This region is known as the typical
tropical weather region without seasonal change. The tropical
rainforest also is known as the lug of the earth or the treasury of
biodiversity.
The canopy access crane had constructed in March 2000. This
crane is about 80m tall height with 75m arm length
(Nakashizuka et al., 2003). Using the gondola of this crane, it
can make us possible to access to any point three-dimensionally.
10ﾟ
N
Lambir Hills National
Park
MALAY
PENINSULA
BORNEO
(KALIMANTAN)
0゜
SUMATRA
100゜E
110゜E
120゜E
Fig.1 Study site and the canopy access crane
This contribution has been peer-reviewed.
doi:10.5194/isprsarchives-XL-7-217-2014
217
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-7, 2014
ISPRS Technical Commission VII Symposium, 29 September – 2 October 2014, Istanbul, Turkey
3. LIGHT DISTRIBUTION IN FOREST
Incident solar radiation proceeds from the top of the canopy to
the forest floor, and consists of three components. The first is
direct radiation, which penetrates the top of the canopy into the
forest. The second is diffuse radiation, which is reflected from
leaf or ground surfaces. The third is transmissive radiation,
which penetrates leaves.
Attenuation of solar radiation is the sum of the three
components. Radiation which penetrates the forest is modelled
using the Lambert–Beer law, which is expressed in eq.1.
According to the Lambert–Beer law, light intensity decays
exponentially with Leaf Area Index (LAI). Solar radiation at
any height in the forest, I, is defined by eq.1 from the incident
solar radiation at the top of the canopy, I0, and the
corresponding LAI at that height. This equation applies to any
plant species. Photosynthetic Photon Flux Density (PPFD,
quantum units: mol/m2/s) is used normally to represent
radiation in this kind of analysis. The PPFD is also expressed by
PAR. Most incident PAR penetrates leaves and is absorbed
effectively by photosynthesizing pigments such as chlorophyll.
I / I0 = exp (− k (LAI))
(1)
where I0 is the incident PAR at the top of canopy, I is
transmissive PAR and k is the coefficient of light absorption,
and where:
relative PAR = I / I0
(2)
Light attenuation at any forest height is expressed by the
relative PPFD, which is shown in eq.2. This is the ratio between
incident and transmissive PPFD, and is calculated from PPFD at
a particular height compared with incident PPFD at the top of
the canopy (Lowman and Nadkarni 1995). The absorption
coefficient k expresses light absorption below the forest surface.
MkVL by Alec) was used. The quantum sensor was set up on
the top of the observation crane, unobscured by obstacles.
To monitor sky conditions and account for cloud effects on the
forest
light
environment
during
qualitative
forest
characterization, whole-sky images were captured with a
fisheye lens camera installed at the top of canopy.
4.2 Transmissive PPFD
Incident PPFD is transmitted and scattered by different forest
layers at different heights. Various PAR data were measured
with quantum units at different forest heights by the same
quantum sensors. By comparing PPFDs at different heights with
the standard PPFD, relative PPFDs are calculated which
indicated the degree of PPFD decrease from the canopy top to
lower levels.
Fig.3 shows the target canopy view and the quantum sensors’
horizontal and vertical distributions. The upper left figure shows
the incident PPFD measurement instruments’ view at the top of
the crane. The central upper figure shows the distribution of
four horizontal measurement points on our objective canopy. At
each point 1 to 4, 6 quantum sensors were placed at different
heights below the canopy; the upper right image is one of the
sensors’ views. The lower image depicts six vertical sensors’
distributions at four horizontal measurement points.
The S-25 sensor measured the standard PPFD at the top of the
canopy for calculation of relative PPFD.
Objective canopy of measurement
I ncident PPFD
Top of crane
Transmissive PPFD
Sensor at forest floor
S-25(Top of crane)
S-24(43.3m)
Canopy
S-20(36.6m)
4. MEASUREMENTS
S-23(36.9m)
S-22(34.5m)
The concept of our measurements for the light environment
under tropical rainforest canopy is shown in fig.2. The incident
and the transmissive PPFDs measurements are explained as
follows.
S-15(23.4m)
S-12(22.2m)
S-8(15.3m)
30m
S-18(27.5m)
S-14(22.2m)
S-10(20.2m)
S-11(16.2m)
S-7(11.1m)
S-4(8.2m)
S-3(1.1m)
I ncident PPFD
S-21(34.5m)
S-19(31.1m)
S-16(29.1m)
S-6(5.9m)
S-2(1.4m)
S-17(26.9m)
S-13(20.0m)
20m
S-9(12.7m)
10m
S-5(5.5m)
S-1(1.4m)
Forest floor
: Quantum Sensor
Fig.3 Distribution of target canopy and quantum sensors.
5. RESULTS
Canopy surface
about 40m
Transmissive PPFD
5.1 Time representative Consideration
4 vertical points
Below canopy
Forest floor
Fig.2 Concept of the forest light environmental measurements
4.1 Incident PPFD
The incident PPFD is observed for the standard for relative
PPFD calculation. To determine the standard of relative PPFD
calculation, a quantum sensor with ultra-small memory (MDS-
We observed the light environment under the tropical rainforest
canopies for 10 days from 29th August to 7th September in 2005.
The weather conditions were mixed by sunny and cloudy.
Here, we considered the time representativeness of light
environment under the canopies in our site. Fig.4 shows the
relative PPFD at 24 measurement points with one-day average
and 10-days average. Comparing with one-day and 10-days
averages, there is no big difference. Three exponential
approximations in fig.4 are derived from the relative PPFD of
1st Sep under cloudy condition, 5th Sep under sunny condition,
and 10-days under all weather conditions. There is also no
difference between sunny and cloudy days. In this way, it is
able to show the time representativeness of light environment in
the forest by averaging the one-day relative PPFD regardless of
the cloudy and sunny. Also, to derive the approximations as
This contribution has been peer-reviewed.
doi:10.5194/isprsarchives-XL-7-217-2014
218
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-7, 2014
ISPRS Technical Commission VII Symposium, 29 September – 2 October 2014, Istanbul, Turkey
exponential from the relations with relative PPFD with forest
height, that is, there is a linear relationship between forest
height and LAI in our study forest site.
of light environment in the forest by averaging the one-day
relative PPFD regardless of the cloudy and sunny. Furthermore,
we could recognize that the 30-minute average of relative PPFD
measured under cloudy condition has the adequate time
representativeness as minimum time requirement.
As the future works, we will develop the light environmental
modeling under the rainforest canopies by considering the
relationship between the forest height and LAI.
5.2 Time representativeness on weather Conditions
The incident and transmissive PARs under sunny condition are
easy changeable in short time period by clouds movement.
Therefore, we examined the minimum time requirement for the
time representativeness of the light environment under different
weather conditions.
Fig.5 and 6 show the 30-minute average of relative PPFD with
forest height at each measurement point observed on 29th Aug.
under sunny condition and 1st Sep. under cloudy condition
respectively. These exponentials are derived as approximations
from 30-minute averages at 24 measurement points. The
variation of relative PPFD at each measurement point and each
30-minute interval is very large especially more than 20 m of
the sensors’ height on sunny day (fig.5). On the other hand, we
cannot see the big differences between these measurement
points and between 30-minute intervals on cloudy day (fig.6).
From these results, we can recognize that the 30-minute average
of relative PPFD measured under cloudy condition has the
adequate time representativeness of the light environment in
forest.
REFERENCES
Kenzo, T., Ichie, T., Watanabe,Y.,Yoneda,R.,Ninomiya, I. and
Koike, T., 2006, Change in photosynthesis and leaf
characteristics with tree height in five dipterocarpaceae species
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6. CONCLUSION
To characterize the forest light environment as its
representativeness under no consideration of weather conditions,
we analysed huge quantities of instantaneous data which
obtained at the different measurement heights and under
weather conditions in the tropical rainforest.
Through the considerations related with the time
representativeness and weather conditions in the forest light
environment, we could understand the time representativeness
Yamashita, M. and Yoshimura, M., 2009, The Diurnal Global
and Diffuse PAR Change Analysis by Sky Conditions and its
Characteristics. Journal of Environmental Information Science,
Vol. 37, No.5, pp.7-14.
Yoshimura, M. and Yamashita, M., 2012, Measurement of
tropical rainforest three-dimensional light environment and its
diurnal change, International Journal of Remote Sensing, 33:3,
848-859.introduction
100%
8/29
y = 0.0135e0.087x
R² = 0.877
90%
8/30
8/31
80%
Relative PPFD
9/1
y = 0.0142e0.083x
R² = 0.868
70%
9/2
9/3
60%
9/4
y = 0.0147e0.083x
R² = 0.893
50%
9/5
40%
9/6
30%
9/7
10 days ave.
20%
Exponential (9/1)
指数 (9/1)
10%
Exponential (9/5)
指数 (9/5)
Exponential (10days)
指数 (10 days ave.)
0%
0
10
20
30
40
50
Hight (m)
Fig.4 Relations of the relative PPFD and forest height at each measurement points with one-day average and 10-days average.
This contribution has been peer-reviewed.
doi:10.5194/isprsarchives-XL-7-217-2014
219
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-7, 2014
ISPRS Technical Commission VII Symposium, 29 September – 2 October 2014, Istanbul, Turkey
100%
7.5‐ 8.0hAve
8.0‐ 8.5hAve
90%
8.5‐ 9.0hAve
9.0‐ 9.5hAve
80%
9.5‐10.0hAve
70%
10.0‐10.5hAve
10.5‐11.0hAve
Relative‐PPFD
60%
11.0‐11.5hAve
50%
11.5‐12.0hAve
12.0‐12.5hAve
40%
12.5‐13.0hAve
13.0‐13.5hAve
30%
13.5‐14.0hAve
20%
14.0‐14.5hAve
14.5‐15.0hAve
10%
15.0‐15.5hAve
0%
15.5‐16.0hAve
0
10
20
30
40
50
16.0‐16.5hAve
Height (m)
Fig.5 30-minute average of relative PPFD with forest height at each measurement point observed on 29th Aug. under sunny
conditions.
100%
7.5‐ 8.0hAve
8.0‐ 8.5hAve
90%
8.5‐ 9.0hAve
9.0‐ 9.5hAve
80%
9.5‐10.0hAve
70%
10.0‐10.5hAve
10.5‐11.0hAve
Relative‐PPFD
60%
11.0‐11.5hAve
50%
11.5‐12.0hAve
12.0‐12.5hAve
40%
12.5‐13.0hAve
13.0‐13.5hAve
30%
13.5‐14.0hAve
20%
14.0‐14.5hAve
14.5‐15.0hAve
10%
15.0‐15.5hAve
0%
15.5‐16.0hAve
0
10
20
30
40
Height (m)
50
16.0‐16.5hAve
Fig.6 30-minute average of relative PPFD with forest height at each measurement point observed on 1st Sep. under cloudy condition.
This contribution has been peer-reviewed.
doi:10.5194/isprsarchives-XL-7-217-2014
220