Methodological overview to hemispherical photography, demonstratedon an example of the software GLA
Keywords:
hemispherical photography, Gap Light Analyser, SideLook, thresholding, exposure timeAbstract
This contribution provides a literature overview concerning minimising the two main error sources at shooting and evaluating hemispherical photographs with the aid of the software Gap Light Analyser 2.0. It deals with matcrialisation of the process in which these phenomena arise. The point is at determining the exposure time and thresholding (determining the optimum brightness value for the pixel as the threshold for distinguishing between the foliage and the sky patches on a hemispherical photograph).
References
BARTIOD S., EPRON D. 2005. Variations of construction cost associated to leaf area renewal in saplings of two co-occurring temperate tree species (Acer platanoides L. and Fraxinus excelsior L.) along a light gradient. Ann. For. Sci., 62: 545-551.
BEAUDET M., MESSIER C. 2002. Variation in canopy openness and light transmission following selection cutting in northern hardwood stands: an assessment based on hemispherical photographs. Agric. Forest Meteorol., 110: 217-228.
BROWN, N. D. 1993. The implications of climate and gap inicroclimnte for seedling growth in a Bornean lowland rain forest. J. trop. Ecol., 9: 153-168.
BROWN, N. D., JENNINGS, S., WHEELER, P., NABENIELSON, J. 2000. An improved method for the rapid assessment of forest understorey light environments. J. appl. Ecol., 37: 1044-1053.
CRANE C. E., SHEARER B. L. 2007. Hemispherical digital photographs offer advantages over conventional methods for quantifying pathogen-mediated changes caused by infestation of Phytophthora cinnamomi. Austral. Pl. Pathol., 36: 466-474.
DAUZAT, J., CLOUVEL, P., LUQUET, D., MARTIN P. 2008. Using Virtual Plants to Analyse the Light-foraging Efficiency of a Low-density Cotton Crop. Ann. Bot., 101:1153-1166.
ENGLUND, S. R., O'BRIEN, J. J., Clark, D. B. 2000. Evaluation of digital and film hemispherical photography for predicting understorey light in a Bornean tropical rain forest. Agr. Forest Meteorol., 97: 129-139.
FRAZER, G. W., CANHAM, C. D., LERTZMAN, K. P. 1999. Gap light analyzer (GI.A). Version 2.0. Imaging software to extract canopy structure and gap light transmission indices from true-color fi-sheye poto-graphs: users'manual and program documentation. Burnaby, BC, Canada: Simon Fraser University. 36 p.
GLONČAK, P. 2007. Príspevok k metódam hodnotenia dynamiky vegetácie na príklade horských smrečín Nízkych Tatier [Contribution to the methods of vegetation dynamics assessment: an example from Picea abies mountain forest in the Nizke Tatry mts.]. In KRÍŽOVÁ, E., UJHÁZY, K. (eds). Dynamika, stabilita a diverzita lesných ekosystémov. 7.volen: Technická univerzita, p. 15-23.
GLONCAK, P. 2008. Dep. of Phytology, Faculty of Forestry, Technical University in Zvolen, T. G. Masaryka 24, Zvolen. 11. 6. 2008. Personal communocation.
HALH, S.E., BROWN, N. 2005. Use of the canopy-scope for assessing canopy openness in plantation forests. Forestry, 78:365-371.
HARDY, J. P., MHLLOH, R., KOENIG, G., MARKS, D., WINSTRAL, A., POMEROY, J. W., LINKD, T. 2004. Solar radiation transmission through conifer canopies. Agr. Forest Meteorol., 126: 257-270.
JANIŠOVÁ, M., HRIVNÁK, R., GÖMORY, D., UJHÁZY, K., VALACHOVIČ, M., GÖMÖRYOVÁ, E., HEGEDUŠOVÁ, K., ŠKODOVÁ, I. 2007. Changes in understorey vegetation after Norway spruce colonization of an abandoned grassland. Ann. Bot. Fenn., 44: 256-266.
JELASKA, S. D. 2004. Analysis of canopy closure in the Dinaric silver fir-beech forests (Omphalodo-Fagetum) in Croatia using hemispherical photography. Hacq., 3: 43-49.
JELASKA, S. D., ANTONIĆ, O., BOŽIĆ, M., KRIŽAN, J., KUŠAN, V. 2006. Responses of forest herbs to available understory light measured with hemispherical photographs in silver fir-beech forest in Croatia. Ecol. Modell., 194: 209-218.
JENNINGS, S. B., BROWN, N. D., SHEIL, D. 1999.Assessing forest canopies and understorey illumination: canopy closure, canopy cover and other measures. Forestry, 72: 59-73.
JONCKHEERE, I., FLECK, S., NACKAERTS, K., MUYS, B., COPPIN, P., WEISS, M., BARET, F. 2004. Review of methods for in situ leaf area index determination. Part I. theories, sensors and hemispherical photography. Agric. Forest Meteorol., 121: 19-35.
JONCKHEERE, I., NACKAERTS, K., MUYS, B., COPPIN, P. 2005. Assessment of automatic gap fraction estimation of forests from digital hemispherical photography. Agric. Forest Meteorol., 132: 96-114.
MONTE M. A., REIS M. G. F., REIS G. G., LEITE H. G., STOCKS J. J. 2007. Métodos indiretos de estimação da cobertura de dossel em povoamentos de clone de cucalipto [Indirect methods to estimate canopy coverage of clonal eucalypt plantations]. Pesq. agropec. bras., 42: 769-775.
MONTERO, M.J., MORENO, G., BERTOMEU, M. 2008. Light distribution in scattered-trees open woodlands in Western Spain. J. Agrofor. Syst., 73: 233 244.
MORSDORF, F., KOTZ, B., MEIER, E., ITTEN, K. I., ALL-GOWER, B. 2006. Estimation of LAI and fractional cover from small footprint airborne laser scanning data based on gap fraction. Remote Sens. of Environ., 104:50-61.
NOBIS, M. 2005. SideLook 1.1 - Imaging software for the analysis of vegetation structure with true-colour photographs. 6 p. http://www.appleco.ch
NOBIS, M., HUNZIKER, U. 2005. Automatic thresholding for hemispherical canopy-photographs based on edge detection. Agr. Forest Meteorol., 128: 243 250.
RAMOS, F. N., SANTOS, F. A. M. 2006. Microclimate of Atlantic Forest Fragments: Regional and Local Scale Heterogeneity. Braz. Arch. Biol. Techn., 49: 935-944.
ROXBURGH, J. R., KELLY, D. 1995. Uses and limitations of hemispherical photography for estimating forestlight environments. N. 7. J. Ecol., 19: 213-217.
SCHNITZLER, A., CLOSSET, D. 2003. Forest dynamics in unexploited birch (Betula pendula) stands in the Vosges (France): structure, architecture and light patterns. For. Ecol. Mgmt, 183: 205 220.
SHINE, R., BARROTT, E. G., ELPHICK, M. J. 2002. Some like it hot: effects of forest clearing on nest lemperatures of montane reptiles. Ecology, 83: 2808-2815.
SIMONI, G., GIGNOUX, J., LE ROUx, X. 2003. Tree layer spatial structure can affect savanna. Production and water budget: results of a 3-D model. Ecology, 84: 1879-1894.
WHITMORE, T. C., BROWN, N. D., SWAINE, M. D., KENNEDY, D. K., GOODWIN-BAILEY, C. I., GONG, W. K. 1993. Use of hemisphere photographs in forest ecology: measurement of gap size and radiation totals in a Bornean tropical rain forest. J. trop. Ecol., 9: 131-151.
7.HANG, Y., CHEN, J. M., MIL.I.ER, J. R. 2005. Determining digital hemispherical photograph exposure for leaf area index estimation. Agr: Forest Meteorol., 133: 166 181.
Downloads
Published
Issue
Section
License
Copyright (c) 2008 Benjamín Jarčuška (Author)
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
This journal provides immediate open access to its content under the Creative Commons BY-NC-ND 4.0 license. Authors who publish with this journal retain all copyrights except for commercial rights (transfer of commercial rights) and agree to the terms of the above-mentioned CC BY-NC-ND 4.0 license.
