Comparison of direct and indirect methods for assessing leaf area index across a tropical rain forest landscape

Olivas, Paulo C.; Oberbauer, Steven F.; Clark, David B.; Clark, Deborah A.; Ryan, Michael G.; O’Brien, Joseph J.; Ordoñez, Harlyn

doi:10.1016/j.agrformet.2013.04.010

Cited by 71 publications

(61 citation statements)

References 29 publications

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“…The negatively biased LAI values arising from optical methods have usually been reported by many previous studies (e.g., Gower and Norman 1991;van Gardingen et al 1999;Macfarlane et al 2007;Olivas et al 2013). Most of these studies, however, reported only observed differences in LAI between direct and indirect methods over a certain period (e.g., the annual maximum LAI period), and few studies have evaluated the accuracy of optical methods for estimating seasonal LAI variation, validated against direct methods, for a forest stand.…”

Section: Introductionmentioning

confidence: 87%

On improving the accuracy of digital hemispherical photography measurements of seasonal leaf area index variation in deciduous broadleaf forests

et al. 2015

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Optical methods have been widely used to estimate seasonal changes of the leaf area index (LAI) in forest stands because they are convenient and effective; however, their accuracy in deciduous broadleaf forests has rarely been evaluated. We estimate the seasonal changes in the LAI by combining periodic observations of leaf area variation with litter collection (LAI dir ) in deciduous broadleaf forests and use these estimates to evaluate the accuracy of optical LAI measurements made using digital hemispherical photography (DHP). We also propose a method to correct DHP-derived LAI (LAI DHP ) values for seasonal changes in major factors that influence the determination of LAI, including the woody to total area ratio (␣), the element clumping index (⍀ E , using three different methods), and the photographic exposure setting (E). Before these corrections were made, LAI DHP underestimates LAI dir by 14%-55% from 21 May to 1 October but overestimates it by 78% on 12 May and by 226% on 11 October. Although pronounced differences are observed between LAI dir and LAI DHP , they are significantly correlated (R 2 = 0.85, RMSE = 0.32, P < 0.001). After considering seasonal changes in ␣, ⍀ E , and E, the accuracy of LAI DHP improves markedly, with a mean difference between the corrected LAI DHP and LAI dir of <17% in all periods. The results suggest that the proposed scheme for correcting LAI DHP is useful and effective for estimating seasonal LAI variation in deciduous broadleaf forests.

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Section: Introductionmentioning

confidence: 87%

On improving the accuracy of digital hemispherical photography measurements of seasonal leaf area index variation in deciduous broadleaf forests

et al. 2015

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“…Additionally, recent studies reported that an incorrect exposure setting in DHP LAI estimation may be a significant source of error (Chen et al 1991, Cescatti 2007, Chianucci & Cutini 2012, Beckschäfer et al 2013, Song et al 2013 by decreasing the contrast between the sky and foliage, further affecting the calculation of the LAI by DHP. Comparisons of the LAI estimated from DHP and the LAI-2000 techniques with those obtained from direct measurements have often been reported (Dufrêne & Bréda 1995, Chen et al 1997, Thimonier et al 2010, Mason et al 2012, Olivas et al 2013. However, the accuracy of the Le from DHP or LAI-2000 after correction for woody materials and clumping effects has rarely been evaluated based on nondestructive direct methods in different mixed deciduous-evergreen (i.e., deciduous broadleaf and evergreen needleleaf) and deciduous needleleaf forest stands.…”

Section: Introductionmentioning

confidence: 99%

Evaluation and correction of optically derived leaf area index in different temperate forests

Liu¹,

Jin²,

Zhou³

2016

iForest

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In recent years optical techniques for rapid LAI measurements have been developed, but few studies have been performed to evaluate the accuracy of optical estimation of LAI in mixed deciduous-evergreen forest stands. In this paper, we assessed the accuracy of digital hemispherical photography (DHP) and the LAI-2000 for the estimation of effective LAI (Le) by comparison with litter collection LAI (LAIlit) in four mixed deciduous broadleaf and evergreen needleleaf forests and one deciduous needleleaf forest. We also evaluated the relative contribution of major error sources to the determination of LAI by optical methods, including the woody-to-total area ratio (α), the element clumping index (ΩE) and the needle-to-shoot area ratio (γE). Additionally, incorrect automatic photographic exposure has been considered for DHP.

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“…The LAI also plays an important role in stimulating carbon and hydrological cycles (Beckschäfer et al, 2014;Olivas et al, 2013). In photosynthesis process, LAI is the driving factor to produce biomass or net primary production (Eisfelder, Klein, Niklaus & Kuenzer, 2014).…”

Section: Introductionmentioning

confidence: 99%

“…LAI in broadleaf forest is defined as one sided green leaf area per unit ground area (Olivas et al, 2013;Pu, Yu, Gong & Biging, 2005) and it is the key physical factor in the energy exchange between terrestrial ecosystem and atmosphere (Cristiano, Klein, Niklaus & Kuenzer, 2014;Gonsamo & Pellikka, 2008). The LAI also plays an important role in stimulating carbon and hydrological cycles (Beckschäfer et al, 2014;Olivas et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Leaf Area Index Derived from Hemispherical Photograph and its Correlation with Aboveground Forest Biomass

Basuki

2015

Ina.J.For.Res

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LEAF AREA INDEX DERIVED FROM HEMISPHERICAL PHOTOGRAPH AND ITS CORRELATION WITH ABOVE-GROUND FOREST BIOMASS. Leaf area index (LAI) is one of the key physical factors in the energy exchange between terrestrial ecosystem and atmosphere. It determines the photosynthesis process to produce biomass and plays an important role in performing forest stand reflectance. Therefore building relationship between LAI and biomass from field measurements can be used to develop allometric equations for biomass estimation. This paper studies the relationship between diameter at breast height (DBH) and leaves biomass, DBH and crown biomass (sum up of leaves, twigs and branches) as well as between LAI and leaves biomass; LAI and crown biomass; LAI and Total Above-ground Biomass (TAGB) in East Kalimantan Province. Destructive sampling was conducted to develop allometric equations. The DBH measurements from 52 sample plots were used as training data for model development (35 plots) and for validation (17 plots). A hemispherical photograph was used to record LAI. The result shows that strong corelation (r) exists between natural logarithmic (ln) DBH and crown biomass ranging from 0.88 to 0.98. The correlation (r) between LAI and biomass of leaves; leaves + twigs + branches; TAGB were 0.742, 0.768 and 0.772, respectively. Improvement of (r) between LAI and biomass can be conducted by proper time of LAI measurement, when the sky is uniformly overcast.Keywords: LAI, biomass, hemispherical photograph, allometric equation, East Kalimantan INDEKS LUAS DAUN (LAI YANG DIAKSES DARI FOTO HEMISPHERICAL DAN KORELASINYA DENGAN PERMUKAAN BIOMASSA HUTAN. Indeks luas daun (LAI) merupakan salah satu faktor fisik utama dalam pertukaran energi antara ekosistem daratan dan atmosfer. LAI menentukan proses fotosintesis yang memproduksi biomassa dan berperan penting dalam reflektan parameter tegakan hutan, oleh karena itu hubungan antara LAI dan biomassa dari pengukuran lapangan perlu dibangun untuk membentuk persamaan allometrik yang selanjutnya digunakan untuk mengestimasi biomassa di tempat lain. Tulisan ini mempelajari hubungan antara diameter setinggi dada (DBH) dengan biomassa tajuk (daun; daun + ranting + cabang) dan juga antara LAI dengan biomassa tajuk; serta LAI dengan biomassa total (TAGB

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Comparison of direct and indirect methods for assessing leaf area index across a tropical rain forest landscape

Cited by 71 publications

References 29 publications

On improving the accuracy of digital hemispherical photography measurements of seasonal leaf area index variation in deciduous broadleaf forests

On improving the accuracy of digital hemispherical photography measurements of seasonal leaf area index variation in deciduous broadleaf forests

Evaluation and correction of optically derived leaf area index in different temperate forests

Leaf Area Index Derived from Hemispherical Photograph and its Correlation with Aboveground Forest Biomass

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