Effects of image quality, size and camera type on forest light environment estimates using digital hemispherical photography

Inoue, Akio; Yamamoto, Katsumi; Mizoue, Nobuya; Kawahara, Yuichiro

doi:10.1016/j.agrformet.2004.06.002

Cited by 47 publications

(42 citation statements)

References 24 publications

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“…Verificaram-se, porém, maiores valores de correlação quando as fotografias foram classificadas utilizando várias metodologias com o aplicativo Sidelook 1.1 (Tabela 1), o que pode ser devido à melhor definição de cor das fotografias obtidas nessa idade. Inoue et al (2004) observaram diferenças significativas entre as dimensões da imagem para a câmera Coolpix 900, sendo a fotografia de maior dimensão (1.280x960 pixels) considerada mais adequada, quando comparada com a dimensão de 640x480 pixels, em razão de maior precisão na captação das imagens dos elementos da copa, como folhas e galhos. No entanto, em relação à câmera Coolpix 990, esses autores não observaram diferenças significativas entre as combinações de dimensões e qualidade da fotografia (básica, normal e alta) e recomendaram o uso das dimensões 640x480 pixels para essa câmera, por requerer menor espaço na memória para armazenamento das fotografias.…”

Section: Resultsunclassified

“…Sua estimativa pode ser alcançada por métodos diretos e métodos indiretos (Cherry et al, 1998;Macfarlane et al, 2000;Jonckheere et al, 2004;Weiss et al, 2004).…”

Section: Introductionunclassified

“…Fotografias hemisféricas ou digitais comuns constituem uma alternativa para o cálculo do IAF, do balanço de radiação e da arquitetura do dossel (Macfarlane et al, 2000;Jonckheere et al, 2004;Chaves, 2005;Leblanc et al, 2005;Zhang et al, 2005;Przeszlowska et al, 2006 (Wagner, 1998(Wagner, , 2001). Contudo, a escolha manual do limiar é subjetiva e arbitrária, e representa uma fonte de erro (Frazer et al, 2001;Jonckheere et al, 2004).…”

Section: Introductionunclassified

“…Contudo, a escolha manual do limiar é subjetiva e arbitrária, e representa uma fonte de erro (Frazer et al, 2001;Jonckheere et al, 2004). Nobis & Hunziker (2005) sugeriram um algoritmo para determinação automática do limiar, baseado na detecção do valor da borda, dado pelo mais alto contraste entre os pixels que representam o céu e o dossel, e concluíram que este algoritmo é apropriado para substituir o método manual, por requerer menor tempo na análise, o que permite que seja aplicado em quantidade maior de fotografias, com maior precisão.…”

Section: Introductionunclassified

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Métodos indiretos de estimação da cobertura de dossel em povoamentos de clone de eucalipto

Monte

Reis

et al. 2007

Pesq. agropec. bras.

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Resumo -O objetivo deste trabalho foi avaliar o potencial de uso de fotografias digitais na estimação do índice de cobertura de dossel (ICD), em substituição ao índice de área foliar (IAF Indirect methods to estimate canopy coverage of clonal eucalypt plantationsAbstract -The objective of this work was to evaluate methods to process digital photographs in order to estimate the canopy coverage index (CCI), to replace the use of leaf area index (LAI). Digital photographs with 640x480 and 1,280x960 pixels were processed with the Erdas Imagine, Gap Light Analyzer and Sidelook softwares. Leaf area index, using the LAI-2000, and digital photographs were obtained from pruned and thinned Eucalyptus grandis clone plantations at 81 and 93 months of age. Significant correlations were observed between LAI and CCI. Greater sized photographs (1,280x980 pixels) allowed better differentiation between sky and canopy pixels. Canopy Coverage Index obtained from digital photographs processed with the Sidelook was better correlated with LAI than that obtained by Erdas Imagine and Gap Light Analyzer. It is possible to use digital photography for eucalypt forest CCI estimation.

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Section: Resultsunclassified

“…Sua estimativa pode ser alcançada por métodos diretos e métodos indiretos (Cherry et al, 1998;Macfarlane et al, 2000;Jonckheere et al, 2004;Weiss et al, 2004).…”

Section: Introductionunclassified

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Métodos indiretos de estimação da cobertura de dossel em povoamentos de clone de eucalipto

Monte

Reis

et al. 2007

Pesq. agropec. bras.

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“…All images were taken at 1.5 m above ground level on completely overcast days, to enhance image contrast and to avoid chromatic aberrations related to the equipment used (Frazer et al, 2001). Images were black and white and had 1:4 JPEG (Fine) compression and full size resolution (1600 x 1200), according to Frazer et al (2001) and Inoue et al (2004). Auto-focus and ex-was larger in the " bambuzal" than in the gaps or understorey where the lower values of openness were always below 10% ( Figure 2).…”

Section: Light Regimementioning

confidence: 99%

Structure of the herb stratum under different light regimes in the Submontane Atlantic Rain Forest

Lima

Gandolfi

2009

Braz. J. Biol.

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This study aimed to characterize the structure of the herb stratum in relation to light availability in the Submontane Atlantic Rain Forest at the Carlos Botelho State Park, SP, Brazil. Forty-one 10 x10 m plots were established under the closed canopy (18 plots), small and medium canopy gaps (11) and large canopy gaps dominated by Guadua tagoara (Ness) Kunth (12). Inside each plot, the line intercept method was applied to assess soil coverage as an estimate of density of herb stratum vegetation. Hemispherical photographs were taken at the centre of the plots to evaluate the annual light regime. Overall, Calathea communis Wanderley and S. Vieira had the greater mean coverage, followed by woody seedlings, ground ferns and other herbs (mainly, Araceae, Acanthaceae, Amaranthaceae and Cyperaceae). There were strong correlations among several groups of the herb stratum, such as the negative correlations between woody seedlings with the coverage of C. communis and with rocks. The analysis of the hemispherical photographs confirmed the difference among environments that led to significant differences in the soil coverage of the herb stratum vegetation but woody seedlings. For instance, C. communis showed great coverage in large gaps while ferns were more abundant in small and medium gaps and in the understorey. Other herbs, in turn, demonstrated bigger soil coverage in small and medium gaps. Although this study represents a rough assessment of the structure and composition of the herb stratum, the results found here illustrated the evident relation between herb species density and the environmental variation promoted by changes on canopy structure and topography.Keywords: Calathea communis, canopy gaps, ground herbs, light. Estrutura do estrato herbáceo sob diferentes regimes de luz na Floresta Pluvial Atlântica SubmontanaResumo O objetivo deste estudo foi caracterizar a estrutura do estrato herbáceo em relação à disponibilidade de luz na Floresta Pluvial Atlântica Submontana do Parque Estadual Carlos Botelho, SP, Brasil. Para tanto, foram instaladas 41 parcelas de 10 x 10 m em ambientes sob o dossel fechado (18 parcelas), em clareiras pequenas e médias (11), e em clareiras grandes com dominância de Guadua tagoara (Ness) Kunth (12). Em cada parcela a percentagem de cobertura de solo, avaliada através do método de interceptação em linha, foi usada como estimativa da densidade da vegetação do estrato herbáceo. Fotografias hemisféricas foram tomadas ao centro de cada uma das parcelas para avaliar o regime anual de luz nos ambientes. No geral, a maior média obtida foi para Calathea communis Wanderley e S. Vieira, seguida por plântulas de regenerantes lenhosos, pteridófitas terrestres e outras ervas (principalmente Araceae, Acanthaceae, Amaranthaceae e Cyperaceae). Houve ainda fortes correlações entre vários grupos do estrato herbáceo, como as correlações negativas entre plântulas de regenerantes com a cobertura de C. communis e de rochas. A análise das fotografias hemisféricas confirmou a existência de ambientes com...

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Factors affecting rainfall interception determined by a forest simulator and numerical model

Toba

Ohta

2008

Hydrological Processes

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Abstract:To elucidate the factors involved in interception loss, we conducted experiments in which we measured environmental variables such as rainfall intensity, forest structure, and weather conditions. An artificial forest consisting of 24 vinyl trees was used to examine the influences of forest structure and rainfall conditions on interception loss. The interception rate was higher at higher plant area index (PAI) values and wind speeds and lower with greater rainfall intensity.We confirmed the factors affecting interception loss by using an interception model based on the tank model. The artificial forest simulations provide new evidence that interception loss is influenced by the PAI, rainfall intensity, saturation deficit, and wind speed. The effect of the saturation deficit on the interception rate was unclear from the experimental results, but the single-tank model revealed that wind speed strongly influences the effects of the saturation deficit on interception loss. Thus, whereas interception loss was not significantly affected by the saturation deficit at low wind speeds, it increased significantly with the saturation deficit under windy conditions. The model simulation also showed the sensitivity of each factor with regard to the interception rate. The sensitivity of rainfall intensity decreased as the PAI increased, and the sensitivity of the saturation deficit increased as the wind speed increased.The experiments and model calculations clarified the main elements affecting interception loss and their sensitivities. Compared with previous studies on interception loss, this study revealed a positive relationship between the PAI and interception loss, a negative exponential relationship with rainfall intensity, and the effects of the saturation deficit on interception loss.

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Effects of image quality, size and camera type on forest light environment estimates using digital hemispherical photography

Cited by 47 publications

References 24 publications

Métodos indiretos de estimação da cobertura de dossel em povoamentos de clone de eucalipto

Métodos indiretos de estimação da cobertura de dossel em povoamentos de clone de eucalipto

Structure of the herb stratum under different light regimes in the Submontane Atlantic Rain Forest

Factors affecting rainfall interception determined by a forest simulator and numerical model

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