Comprehensive evaluation of Leaf Area Index estimated by several Comprehensive evaluation of Leaf Area Index estimated by several methodmethod

― ― LAI-2000, SunScan, Fish-eye, and littertrap ―LAI-2000, SunScan, Fish-eye, and littertrap ―

　 　 　 　 　 　　　　　　　　　　　　　　　　　　　　　　 Midori　Kurata1　 ， G.A.Sanchez-Azofeifa2 ， Wang　Quan1　,　Yoshitaka　Kakubari1　

1　Faculty　of　Agriculture,　Shizuoka　University　,　2　Earth　&　Atmospheric　Sciences　University　of　Alberta,Canada　

　 Leaf Area Index (LAI) is a key biophysical variable influencing land surface processes such as photosynthesis, transpiration, and energy balance and is a required input for various ecological models. It is necessary to rely first on ground-based LAI estimates if remotely sensed vegetation indices need cross-calibration. At present, there are several techniques for estimating LAI. The aim of this study is to establish a practical technique for LAI estimation suitable to mountaineous beech forest stands.

　　　　　　

Study　site　 　･ The northern slope of the Naeba Mountain (36°51’N, 138°41’N), located in southern Niigata Prefecture in Japan

　･ dominant species is beech (Fagus Crenata)

LAI-2000LAI-2000

SunScanSunScan

measure both incoming radiation and transmitted through the canopy

1) Estimated　LAI　by　direct　methods　. ･ litter collection: One of the most reliable methods the LAI estimation ●For the old-beech forest, the relationship was almost 1:1● The destructive sampling was made for sites with no litter traps, from which the estimated values then used as ground truth

In　 this　 study,　 LAI　 from　 litter　 collection　 or　 allometric　equation　was　treated　as　true　values,

LAI-2000 was suitable for LAI estimation in mountain beech forests. And broad view angle is required for measuring. In addition, it usually underestimates LAI and thus needs conection before it can be used.

Although it is very portable, Fish-eye measuring requires more technique.

SunScan is hard to use in the forest stands if the cable is connected to BFS. However, SunScn is resistant to weather changes and can keep measuring under versatile weather conditions.

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k

1500

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1300

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X3

700n

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600k

550k

900X

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900X

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1200

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900y X4

700n

old-wood young-wood mix-wood

litter collection

allometric equation

LAI2000 (90°)

sunscan

fisheye

E-mail : zoorin@agr.shizuoka.ac.jp

E-mail : zoorin@agr.shizuoka.ac.jp

3) Estimating　LAI　by　direct　methods

1)　1)　IntroductioIntroductionn

2)　Material　&　2)　Material　&　MethodMethod

Mt. Kaguramine(2029 m)

Long Term Ecological Monitoring Studies Sites since 1970

Mt.Naeba (2145.3 m)

1500m

550m

Mt. Kaguramine(2029 m)

Long Term Ecological Monitoring Studies Sites since 1970

Mt.Naeba (2145.3 m)

1500m

550m

#15

litter　collection　5-10 litter traps were set randomly at 8sites respectively

allometric　aquation　 　 In seven sites, destructive samplings were made for parameterising allometric at each altitude (IBP, 1970) measure the diffuse radiation below 490nm

In this study, with view caps of 22.5°and 90°

4) Estimating　LAI　by　indirect　methods

3)　Results　and　3)　Results　and　DiscussionDiscussion

Among these indirect methods, LAI-2000 has the strongest correlation with the direct estimated LAI.with 90°view-cup → Wide field-of-view is much desired for the heterogeneous radiation environment as below canopy. Although it was underestimated →It needs connection before it can be used.

SunScan estimated LAIe of old-beech has the linear relationship to direct LAI, although in young-beech LAIe was underestimated.

Fisheye estimated LAIe is saturated around LAIe =2. Classification of images involves using digital image process to distinguish canopy opening from foliage, which is achieved by determining a threshold intensity value.

4)　4)　ConclusionConclusion

log F = h log ( D2H ) + K ･･･ ( for old-beech and mix-wood )

F = 0.006 × ( Dπ ) 2+ 0.4656 ( Dπ ) ･･･ ( for young-beech )

F: total leaf area of each tree, D: diameter at breast height, H: tree height, h and K: fitted coefficients of the equation at different altitudes.

SunScan　:　Canopy Analysis System (Delta-T Devices Ltd, UK) measure the PAR above canopy (with BFS) and below canopy (with probe)

measuring radiation based on gap fraction and calculating LAI from the Beer-Lambert extinction law

Fish-eyeFish-eye

LAI-2000　:The Plant Canopy Analyser (LI-COR Inc. , USA)

Fish-eyeHemispherical photograghs taken by using digital cameras with fishey converter→calculated by a specific software Hemiview (Delta-T Devi ces Ltd, UK). ( gap fraction and canopy openness)

R2 = 0.95

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0 1 2 3 4 5 6 7 8LAI estimated by allometric equation

LAI e

stim

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litte

r col

lect

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old-beechmix-woodyoung-beech

( 1: 1 )

Fig. 1 Relationships between LAI estimated by allometric equation and by litter collection.The dotted line is 1:1

the leaf fall from the understories

the less destructive samplings

Fig. 2 The relationships between LAI based on direct methods and LAIe estimated by LAI-2000, SunScan and Fish-eye. Thick line shows the correlation of all samples, while thin line only for old-beech.

Fig. 3 LAI Estimated by litter collection, allometric equatiion, LAI-2000, SunScan and Fish-eye.

R2 = 0.22

R2 = 0.71

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0 1 2 3 4 5 6 7 8LAI estimated by LAI2000 (22.5°)

LA

I es

tim

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ct m

etho

d ( 1: 1)

R2 = 0.57

R2 = 0.92

0 1 2 3 4 5 6 7 8LAI estimated by LAI2000 (90°)

old-beechmix-woodyoung-beech

( 1: 1)

R2 = 0.09

0 1 2 3 4 5 6 7 8LAI estimated by Fish-eye

old-beech

mix-wood

young-beech

( 1:1)

R2 = 0.59

R2 = 0.52

0 1 2 3 4 5 6 7 8LAI estimated by SunScan

( 1:1)

typesite name 1500ｋ 1500y 1300y 900X3 700n2 600k 550ｋ 1200y 1100y 900y 900X4 700ｎ 900X1 900X5altitude (m) 1500 1500 1300 900 700 600 550 1200 1100 900 900 700 900 900age of stands (yr) 300 300 300 150 200 250 260 250 250 250 150 200 70 85DBH (cm) 17.6 13.8 11.5 28.9 36.9 30.2 37.1 20.0 11.8 16.6 15.8 16.0 23.1 17.3mean tree height (m) 22 20 20 22 30 27 34 20 19 31 21 31 21 21stand density (trees ha-1) 450 229 250 383 361 433 246 539 625 535 829 425 1033 1400basal area (m2/ha) 30.4 21.3 31.4 41.6 52.4 45.6 36.3 35.3 53.8 44.8 30.8 30.9 51.1 46.5percent of Fagus Crenata (%) 71 72 86 59 82 74 86 33.0 38.0 41.0 28.1 31.4 94 74

○ ○ ○ ○ ○ ○ ○ ○○ ; destructive sampling were made in 1970s

old-beech mix-wood young-beech