A comparison of different survey methods for assessing gap parameters in old-growth forests

Yamamoto, Shin‐Ichi; Nishimura, Norio; Torimaru, Takeshi; Manabe, T.; Itaya, Akemi; Bęcek, Kazimierz

doi:10.1016/j.foreco.2011.05.029

Cited by 17 publications

(12 citation statements)

References 49 publications

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“…; Green ; Kathke & Bruelheide ; Yamamoto et al. ) confirm what seems to be a general pattern in forest ecology: canopy gaps smaller than 150 m 2 are very abundant (>75%) whereas gaps larger than 400 m 2 are rare (<5%). The exceptionally high proportion of large gaps found by Sanford et al.…”

Section: Discussionmentioning

confidence: 66%

“…Despite the importance of gaps to forest ecology, patterns associated with their frequency, size and shape remain open after more than three decades of gap research. For example, there continues to be uncertainty with regard to which statistical distribution best describes gap sizes (Foster & Reiners 1986;Lertzman & Krebs 1991;Yamamoto et al 2011) or whether gap opening is a random or clumped process in space and time (Brokaw 1985;van der Meer & Bongers 1996a;Nuske et al 2009). Assessments of gap shape, which has a direct influence on gap microclimate and species colonization (Howe 1990;Brown 1993;van Dam 2001), are also scarce (Lertzman & Krebs 1991;Battles et al 1996;Eysenrode et al 1998).…”

Section: Introductionmentioning

confidence: 99%

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Improving methods in gap ecology: revisiting size and shape distributions using a model selection approach

Lima

Prado

Martini

et al. 2012

J Vegetation Science

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Questions We assess gap size and shape distributions, two important descriptors of the forest disturbance regime, by asking: which statistical model best describes gap size distribution; can simple geometric forms adequately describe gap shape; does gap size or shape vary with forest type, gap age or the method used for gap delimitation; and how similar are the studied forests and other tropical and temperate forests? Location Southeastern Atlantic Forest, Brazil. Methods Analysing over 150 gaps in two distinct forest types (seasonal and rain forests), a model selection framework was used to select appropriate probability distributions and functions to describe gap size and gap shape. The first was described using univariate probability distributions, whereas the latter was assessed based on the gap area–perimeter relationship. Comparisons of gap size and shape between sites, as well as size and age classes were then made based on the likelihood of models having different assumptions for the values of their parameters. Results The log‐normal distribution was the best descriptor of gap size distribution, independently of the forest type or gap delimitation method. Because gaps became more irregular as they increased in size, all geometric forms (triangle, rectangle and ellipse) were poor descriptors of gap shape. Only when small and large gaps (> 100 or 400 m2 depending on the delimitation method) were treated separately did the rectangle and isosceles triangle become accurate predictors of gap shape. Ellipsoidal shapes were poor descriptors. At both sites, gaps were at least 50% longer than they were wide, a finding with important implications for gap microclimate (e.g. light entrance regime) and, consequently, for gap regeneration. Conclusions In addition to more appropriate descriptions of gap size and shape, the model selection framework used here efficiently provided a means by which to compare the patterns of two different types of forest. With this framework we were able to recommend the log‐normal parameters μ and σ for future comparisons of gap size distribution, and to propose possible mechanisms related to random rates of gap expansion and closure. We also showed that gap shape varied highly and that no single geometric form was able to predict the shape of all gaps, the ellipse in particular should no longer be used as a standard gap shape.

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Section: Discussionmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Improving methods in gap ecology: revisiting size and shape distributions using a model selection approach

Lima

Prado

Martini

et al. 2012

J Vegetation Science

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“…Most studies in beech-dominated primeval forests reported higher gap fractions, varying between Kenderes et al 2009, Garbarino et al 2012, Rugani et al 2013. Differences in the gap fraction can be due to different gap definitions (e.g., Runkle 1992) and the methods of gap sampling (e.g., Yamamoto et al 2011). Some canopy gap definitions are based on a minimum size of the gaps or a threshold of height difference compared to the surrounding canopy.…”

Section: Canopy Gap Patternmentioning

confidence: 99%

Gap pattern of the largest primeval beech forest of Europe revealed by remote sensing

et al. 2015

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Abstract. Little is known about the gap pattern of primeval beech forests, since large-scale studies with continuous coverage are lacking. Analyses of forest structural patterns have benefitted from advances in remote sensing, especially with the launch of satellites providing data of submetric ground resolution. These developments can strongly advance our knowledge of natural forest dynamics and disturbance regimes. The Uholka-Shyrokyi Luh forest in the Ukrainian Carpathians, the largest remnant of primeval European beech (Fagus sylvatica L.) covering 102.8 km 2 , is an outstanding object to analyze the frequency distribution of gap sizes and to infer processes of forest dynamics. A stereo pair of very high-resolution WorldView-2 satellite images was used to characterize the forest's gap pattern. Canopy gaps were first digitized stereoscopically based on the image pair. In a second step, spectral properties in the red and yellow frequency bands were used to distinguish the stereoscopically mapped gap areas from non-gap areas, which enabled gap mapping over the entire study area. To validate the spectral gap mapping 338 randomly distributed samples were assigned manually to gap and non-gap areas based on the orthoimages. We found excellent agreement except for an overestimation of gaps close to clouds due to diffuse image areas. The frequency distribution of gap size revealed the forest to be structured by a small-scale mosaic of gaps mainly ,200 m 2 (98% of the gaps). Only a few large, stand-replacing events were detected, most probably caused by a wind storm in March 2007 and a heavy wet snow fall in October 2009. The small canopy gaps reflect fine-scale processes shaping forest structure, i.e., the death of single trees or groups of a few trees and is in line with the findings of the terrestrial forest inventory. We conclude that remote sensing approaches based on very high-resolution satellite images are highly useful to characterize even small-scale forest disturbance regimes and to study long-term gap dynamics. Stereo satellite images provide two viewing angles of the study area, thus allowing for a highly accurate mapping of canopy gaps in forests with a complex topography.

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“…A partir de esas mediciones es posible estimar estructura y transmisión de luz al sotobosque (Rich, 1990;Hu et al, 2009), ambas de gran importancia para el inventario forestal (Chen et al, 2006;Cruz-leyva et al, 2010) y el manejo de la regeneración natural (Yamamoto, 2000;Yamamoto et al, 2011).…”

Section: Introductionunclassified

Introducción a la fotografía hemisférica en ciencias forestales

Mauro-Díaz

Lencinas

Valle

2014

MYB

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La fotografía hemisférica es profusamente utilizada en climatología y ciencias forestales en vinculación con tecnología geomática. Permite obtener un registro detallado de los claros del dosel y estimar, tanto la estructura del mismo, como la transmisión de luz al sotobosque, ambas variables de gran importancia para el inventario forestal y el manejo de la regeneración natural. Debido a que los equipos de fotografía hemisférica tienen usos muy diversos, incluso en fotografía artística, su costo es bajo en comparación con instrumentos específicos. Para utilizar esta técnica correctamente se requiere de conocimientos particulares de óptica, fotografía y procesamiento digital de imágenes. El objetivo del trabajo es explicar el principio de funcionamiento de la fotografía hemisférica en estimación de parámetros estructurales de bosques. Para ello se discute sobre óptica y fotografía, procesamiento digital de imágenes y estimación de parámetros estructurales. Conocer estos aspectos es relevante para adquirir un equipo, capturar fotografías en el terreno y utilizar softwares específicos para su procesamiento. Las fotografías son archivos raster, los cuales pueden entenderse como una matriz de n filas por m columnas, donde cada celda es un pixel. Para que un raster se visualice como una imagen es necesario establecer un espacio y una profundidad de color. Es importante tener en cuenta que en la captura de la fotografía se producen muchos errores, ya que dependiendo de la región geográfica es muy difícil satisfacer las condiciones ideales de iluminación.

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A comparison of different survey methods for assessing gap parameters in old-growth forests

Cited by 17 publications

References 49 publications

Improving methods in gap ecology: revisiting size and shape distributions using a model selection approach

Improving methods in gap ecology: revisiting size and shape distributions using a model selection approach

Gap pattern of the largest primeval beech forest of Europe revealed by remote sensing

Introducción a la fotografía hemisférica en ciencias forestales

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