Ground-based measurements of leaf area index: a review of methods, instruments and current controversies

Bréda, Nathalie

doi:10.1093/jxb/erg263

Cited by 1,204 publications

(906 citation statements)

References 104 publications

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“…Essas limitações no cálculo do balanço de energia que efetivamente chega ao interior do dossel em relação à quantidade de energia que chegou ao seu topo foi também abordado por Bréda (2003) e MacFarlane et al (2007).…”

Section: Resultsunclassified

“…Jonckheere et al (2004) classificam a maneira como foi determinado o IAF neste trabalho como método da "árvore modelo" e, segundo Bréda (2003), é menos destrutivo, já que, a partir da amostragem de poucos indivíduos representativos do povoamento, pode-se extrapolar a área foliar, por meio de suas relações com variáveis dendrométricas das árvores. Na tentativa de definir equações alométricas que predissessem a área foliar das demais árvores, foram testadas diferentes combinações das medidas adquiridas dessa variável com a H, o Rc e o DAP.…”

Section: Coleta De Dados Em Campounclassified

“…O Índice de Área Foliar (IAF) é uma variável biofísica que apresenta estreita relação com a produtividade de uma comunidade vegetal, pois representa a capacidade da planta em explorar o espaço ambiental disponível (GOWER et al, 1999;LANG;MCMURTRIE, 1992;VETTORAZZI, 2003), sendo inclusive aproveitado como parâmetro de entrada em modelos relacionados à evapotranspiração, à simulação dos ciclos de carbono e de água e à produtividade florestal (RODRIGUEZ et al, 2009;. De acordo com Bréda (2003), o IAF pode ser considerado um elemento-chave na compreensão da dinâmica da vegetação em ecossistemas terrestres.…”

Section: Introductionunclassified

“…Como esse método não distingue os tecidos fotossinteticamente ativos de outros componentes do dossel, como galhos, ramos e troncos, adota-se a expressão Índice de Área de Vegetação (IAV) para referirse à estimativa obtida por essas metodologias (BRÉDA, 2003;JONCKHEERE et al, 2004).…”

Section: Introductionunclassified

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Estimativas de índice de área foliar de plantios de Eucalyptus spp. segundo três alternativas metodológicas

Cantinho¹,

Ponzoni

Santos

2014

CERNE

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Foram realizadas estimativas de Índice de Área Foliar (IAF) e de Índice de Área de Vegetação (IAV) em 36 parcelas posicionadas em plantios de Eucalyptus sp. localizados nos municípios de Aracruz e São Mateus (ES), de propriedade da empresa FIBRIA S/A, mediante a aplicação de três diferentes técnicas: método destrutivo, processamento de fotografias hemisféricas tomadas no interior dos dosséis e utilização do equipamento LAI-2000 (LICOR). As coletas de dados em campo foram realizadas em duas épocas do ano, procurando explorar diferenças fenológicas atuantes principalmente sobre os valores de IAF e de IAV. As estimativas de IAF efetuadas a partir do método destrutivo, em termos absolutos, foram sempre superiores àquelas do IAV efetuadas a partir dos métodos indiretos. No período chuvoso, as relações entre as estimativas de IAF e de IAV, para ambos os métodos indiretos, foram mais fortes e consistentes do que aquelas verificadas no período mais seco do ano. As relações entre as estimativas de IAV efetuadas pelos dois métodos indiretos (fotografias e LAI-2000) foram consistentes e com grau de aderência mais elevado do que aquelas verificadas entre o IAF e IAV.

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Section: Resultsunclassified

Section: Coleta De Dados Em Campounclassified

Section: Introductionunclassified

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Estimativas de índice de área foliar de plantios de Eucalyptus spp. segundo três alternativas metodológicas

Cantinho¹,

Ponzoni

Santos

2014

CERNE

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“…This method is based on simplified models of light transmission into the canopy. A variety of approaches for estimating PAI using direct and indirect methods were presented by Bréda [49], Jonckheere et al [50] and Weiss et al [51]. Vegetation gap fraction (G) is defined as the fraction of sky seen from below the canopy [49][50][51][52].…”

Section: Pai and Fvc Retrievalmentioning

confidence: 99%

Use of Radarsat-2 and Landsat TM Images for Spatial Parameterization of Manning’s Roughness Coefficient in Hydraulic Modeling

et al. 2015

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Vegetation resistance influences water flow in floodplains. Characterization of vegetation for hydraulic modeling includes the description of the spatial variability of vegetation type, height and density. In this research, we explored the use of dual polarized Radarsat-2 wide swath mode backscatter coefficients (σ°) and Landsat 5 TM to derive spatial hydraulic roughness. The spatial roughness parameterization included four steps: (i) land use classification from Landsat 5 TM; (ii) establishing a relationship between σ° statistics and vegetation parameters; (iii) relative surface roughness (Ks) determination from Synthetic Aperture Radar (SAR) backscatter temporal variability; (iv) derivation of the spatial distribution of the spatial hydraulic roughness both from Manning's roughness coefficient look up table (LUT) and relative surface roughness. Hydraulic simulations were performed using the FLO-2D hydrodynamic model to evaluate model performance under three different hydraulic modeling simulations results with different Manning's coefficient parameterizations, which includes SWL1, SWL2 and SWL3. SWL1 is simulated water OPEN ACCESSRemote Sens. 2015, 7 837 levels with optimum floodplain roughness (np) with channel roughness nc = 0.03 m −1/3 /s; SWL2 is simulated water levels with calibrated values for both floodplain roughness np = 0.65 m −1/3 /s and channel roughness nc = 0.021 m −1/3 /s; and SWL3 is simulated water levels with calibrated channel roughness nc and spatial Manning's coefficients as derived with aid of relative surface roughness. The model performance was evaluated using Nash-Sutcliffe model efficiency coefficient (E) and coefficient of determination (R 2 ), based on water levels measured at a gauging station in the wetland. The overall performance of scenario SWL1 was characterized with E = 0.75 and R 2 = 0.95, which was improved in SWL2 to E = 0.95 and R 2 = 0.99. When spatially distributed Manning values derived from SAR relative surface values were parameterized in the model, the model also performed well and yielding E = 0.97 and R 2 = 0.98. Improved model performance using spatial roughness shows that spatial roughness parameterization can support flood modeling and provide better flood wave simulation over the inundated riparian areas equally as calibrated models.

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Vegetation, land surface brightness, and temperature dynamics after aspen forest die‐off

Huang

Anderegg

2014

JGR Biogeosciences

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Forest dynamics following drought-induced tree mortality can affect regional climate through biophysical surface properties. These dynamics have not been well quantified, particularly at the regional scale, and are a large uncertainty in ecosystem-climate feedback. We investigated regional biophysical characteristics through time (1995-2011) in drought-impacted (2001-2003), trembling aspen (Populus tremuloides Michx.) forests by utilizing Landsat time series green and brown vegetation cover, surface brightness (total shortwave albedo), and daytime land surface temperature. We quantified the temporal dynamics and postdrought recovery of these characteristics for aspen forests experiencing severe drought-induced mortality in the San Juan National Forest in southwestern Colorado, USA. We partitioned forests into three categories from healthy to severe mortality (Healthy, Intermediate, and Die-off ) by referring to field observations of aspen canopy mortality and live aboveground biomass losses. The vegetation cover of die-off areas in 2011 (26.9% of the aspen forest) was significantly different compared to predrought conditions (decrease of 7.4% of the green vegetation cover and increase of 12.1% of the brown vegetation cover compared to 1999). The surface brightness of the study region 9 years after drought however was comparable to predrought estimates (12.7-13.7%). Postdrought brightness was potentially influenced by understory shrubs, since they became the top layer green canopies in disturbed sites from a satellite's point of view. Satellite evidence also showed that the differences of land surface temperature among the three groups increased substantially (≥45%) after drought, possibly due to the reduction of plant evapotranspiration in the Intermediate and Die-off sites. Our results suggest that the mortality-affected systems have not recovered in terms of the surface biophysical properties. We also find that the temporal dynamics of vegetation cover holds great potential for assessing propensity of subsequent mortality during drought itself, which could provide effective monitoring and potentially a much needed "early warning" of drought-induced tree mortality.

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Ground-based measurements of leaf area index: a review of methods, instruments and current controversies

Cited by 1,204 publications

References 104 publications

Estimativas de índice de área foliar de plantios de Eucalyptus spp. segundo três alternativas metodológicas

Estimativas de índice de área foliar de plantios de Eucalyptus spp. segundo três alternativas metodológicas

Use of Radarsat-2 and Landsat TM Images for Spatial Parameterization of Manning’s Roughness Coefficient in Hydraulic Modeling

Vegetation, land surface brightness, and temperature dynamics after aspen forest die‐off

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