canopy structure measurement by gap fraction - search results

On the angular dependency of canopy gap fractions in pine ...

In this short communication paper, measurements of canopy structure, gap fractions and effective LAI in 986 plots of Scots pine, Norway spruce and Silver birch stands are used to assess how sim-ilar the vertical canopy gap fraction profiles (as described by the shape function ()) are for common boreal tree species. 2. Materials

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A method for estimating canopy openness, effective leaf ...

The Canadian Forestry Service, Pacific Forestry Centre, utilized hemispherical photography and paired LAI-2000 Plant Canopy Analyzers to measure gap fraction distribution, canopy openness, effective leaf area index, and seasonally-integrated understory light levels in several age sequences of Coastal Western Hemlock and Douglas-fir forests on ...

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Accuracy and Precision of Two Indirect Methods for ...

canopy. The gap fraction is then computed by taking the ratio of these two measurements. Both measurements must be taken with the light sensor lev-eled and facing the same compass direction. There is extensive theory detailing the relationship between gap fractions, leaf area index, and other canopy structure statistics (Welles and Norman 1991).

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Daily leaf area index from photosynthetically active ...

Abstract Leaf area index (LAI) is a critical biophysical indicator that describes foliage abundance in ecosystems. An accurate and continuous estimation of LAI is therefore desirable to quantify ecosystem status and function (e.g. carbon and water exchange between the land surface and the atmosphere). However, deriving accurate LAI measurements at regular temporal intervals remains challenging ...

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Laser scanning based three dimensional measurement of ...

Three-dimensional vegetation canopy structure is the critical original data source for the evaluation of radiation transfer modeling, remote sensing products validation and many other remote sensing applications. Although a number of three-dimensional measurement techniques have been already used in industrial measurement, few of them can be directly applied to vegetation canopy structure ...

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WinSCANOPY: Canopy Structure and Solar Radiation Analysis

Gap size distribution (GSD), i.e. the number of gaps in function of their size, can be used in combination with gap fractions to quantify the degree of clumpiness at the tree level and to use this information to increase the accuracy of LAI measurements. For a canopy of a given gap fraction with randomly distributed foliage elements, it is ...

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(PDF) Measuring vegetation canopy structure - Leaf Area ...

Vegetation canopy structure characterisation from local to landscape scale Manual to measure and model leaf area index and its spatial variability on local and landscape scale Dr Marion Pfeifer1 & Dr Alemu Gonsamo2 1 Ecology and Evolution, Faculty of Natural Sciences, Imperial College of Science, Technology and Medicine, UK, [email protected] 1 Geography Department, University …

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Canopy Structure, and Leaf area, are fundamental features ...

Canopy Structure, and Leaf area, are fundamental features of the landscape. We ... With hemisphericalphotographs one can measure gap fraction and infer leaf area index. The method was pioneered in the 70s, including my mentor, Boyd Hutchinson. The method is rapid, cheap and indirect, but there is art to detecting

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Evaluation of structure description requirements for ...

between gap fraction and canopy structure suffer from the Iimited accuracy of the measurements. A laboratory experiment was therefore conducted on artificial canopies, which enabled an accurate ...

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Estimating forest canopy bulk density using six indirect ...

ing leaf area index (LAI) and canopy gap fraction. Results from CBD estimates are compared across the six indirect techniques, and regression equations are developed so that these methods can be used in the field. Recommendations on their use are discussed. Background Current methods Canopy bulk density (CBD) is difficult to measure be-

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TWO-DIMENSIONAL FOREST CANOPY ARCHITECTURE FROM ...

to measure forest canopy directional gap fraction, defined as one minus the probability of a beam of light intercepting a canopy element in a given direction. Lovell et al. (2003) used a laser scanner to determine directional gap fraction in stands of different species and found close correlation with data from hemispherical photography.

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Methodology comparison for canopy structure parameters ...

2.2. Gap fraction inversion Gap fraction inversions have often been used to estimate the foliage density of canopies based on different models. Simple models, such as Beer-Lambert's law (Eq. (1)), are commonly used while more complex models that consider explicitly crowns placement (e.g. Fournier et al., 1996; Nilson,1999) are

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CiteSeerX — Journal of Experimental Botany

CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): Canopy structure measurement by gap fraction analysis

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Evaluation of hemispherical photos extracted from ...

2014) . From the binarized images, canopy structure measures such as canopy openness, leaf area index, gap fraction, etc. can be estimated (Frazer, Trofymow and Lertzman, 1997; Gonsamo, D'odorico and Pellikka, 2013; Chianucci, 2020) . By plotting a sun path onto the binarized image the canopy structure can be used to infer understory light ...

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A clumped-foliage canopy radiative transfer model for a ...

(4) ground lidar measurements of the canopy gap fraction in woodland in Australia. The model comparisons with these measurements demonstrate that the ACTS model achieves better or similar performance compared to the full GORT and the layered Beer's law schemes with regard to

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Digital Cover Photography for Estimating Leaf Area Index ...

Keywords: light intercepted by the canopy; gap fraction; clumping index; remote sensing 1. Introduction Accurate modeling of energy balance, gas exchange processes and light dist ribution occurring within the canopy of fruit orchards requires the characterization and assessment of canopy vigor and structure.

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Canopy structure measurement by gap fraction analysis ...

Canopy structure measurement by gap fraction analysis using commercial instrumentation Jon M. Welles, Jon M. Welles 3. 1. LI-COR. Inc, 4421 Superior St., Lincoln, NE 68504, USA. 3 To whom correspondence should be addressed: + 1 402 467 2819. E-mail: [email protected] ...

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Terrestrial laser scanners to measure forest canopy gap ...

The canopy directional gap fraction computed from the three laser scans showed a similar pattern with a very low gap fraction at zenith angles between 0° to 20°, maximum gap fractions of approximately 13% at zenith angles between 25° to 30° and lower gap fractions at higher zenith angles.

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Digital Cover Photography for Estimating Leaf Area Index ...

2.4. Canopy Light Interception Measurements. Incident radiation (I o) and the radiation transmitted below canopy (I) were measured using a commercial Ceptometer (AccuPAR LP-80, Decagon Devices Inc., Pullman, WA, USA), by taking one measurement above the canopy and five measurements distributed below the canopy parallel to tree rows.The measurements were regularly …

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Structural diversity as a predictor of ecosystem function ...

The two metrics of height and openness, mean canopy height and gap fraction, significantly predicted 5 of 6 ecosystem functions (figure 2). Mean canopy height consistently positively predicted two proxies of ecosystem productivity, while gap fraction negatively predicted these two functions (basal area and LAI; figures 2(A) and (B)).

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Canopy structure measurement by gap fraction analysis ...

Canopy structure measurement by gap fraction analysis using commercial instrumentation, Journal of Experimental Botany, 1996, pp. 1335-1342, 47/9, DOI: 10.1093/jxb/47.9.1335 Home · About ...

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CI-110 Plant Canopy Imager | Tools for Applied Plant ...

Gap Fraction indicates how much of the sky is visible from beneath the plant canopy. The greater the area of sky that is visible, the larger the gap fraction. When using the CI-110, a value between 0 and 1 is assigned to estimate the Gap Fraction in a canopy—0 means that no sky is visible below the plant canopy whereas 1 means that the entire ...

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ORNL DAAC SAFARI 2000 LEAF AREA INDEX AND CANOPY STRUCTURE ...

The parameters derived from the TRAC instrument include estimates of plant or leaf area index (PAI, LAI), overstory gap fraction, and clumping index. At each site the TRAC instrument was carried along three parallel transects, each 750 m long and spaced 250 m apart. Measurements were made every 25 m along the transects.

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Influence of image pixel resolution on canopy ...

Nilson T.,Kuusk A. 2004 - Improved algorithm for estimating canopy indices from gap fraction data in forest canopies.Agricultural and Forest Meteorology 124: 157-169. Paletto A., Tosi V. 2009 - Forest canopy cover and canopy closure: comparison of assessment techniques. European Journal of Forest Research 128(3): 265-272.

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CANOPY DAMAGE AND RECOVERY AFTER SELECTIVE …

canopy gap fraction with spectral mixture analyses of Landsat 7 satellite imagery to assess landscape and regional dynamics of canopy damage following selec-tive logging in the eastern Amazon. Our field studies encompassed measurements of ground damage and canopy gap fractions along multitemporal sequences of post-harvest regrowth of 0.5–3.5 yr.

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Near-surface remote sensing of canopy architecture and ...

canopy structure with methods developed for homogeneous, closed canopies are prone to failure. I employed a multi-model and multi-instrument approach to quantify leaf area index in an oak savanna ecosystem of California. I found that the effective area index should be calculated by taking the logarithm of average gap fraction.

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Quantifying vertical and horizontal stand structure using ...

canopy segments and gap fraction between each vertical slice within and between individual forest measurement plots. We found a significant relationship between the ... Canopy structure can also be linked to stand productivity both above and below ground (Kirsch 2013). ...

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LBA-ECO ND-04 Secondary Forest Recovery, Structure, and ...

Canopy cover was calculated using the canopy gap diffuse data, the fraction of pixels in each sky region that are open (white) on the fisheye photograph, weighted by hemispherical area. Forest structure and biomass measurements:

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(PDF) Bias in lidar-based canopy gap fraction estimates ...

Testing the Application of Terrestrial Laser Scanning to Measure Forest Canopy Gap Fraction. By Richard Armitage. Developing a dual-wavelength full-waveform terrestrial laser scanner to characterize forest canopy structure. By Mathias Disney. Terrestrial laser scanning for forest monitoring.

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Canopy gap fraction estimation from digital hemispherical ...

This makes it possible for a human interpreter (or for a programmed algorithm) to create an above-canopy sky reference from below-canopy images. Thus, gap fraction measurements can be made using a single digital hemispherical camera that is capable of storing sensor raw data if the gaps in the canopy are large enough to be reliably identified ...

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Forest Canopy Structural Complexity and Light Absorption ...

1 Introduction. The relationship between forest canopy structure and light absorption is a long-standing and ever advancing subject foundational to many research areas in the physical sciences, including the modeling and measurement of biogeochemical cycles, energy balance, and other Earth system processes (Shugart et al., 2010; Watt, 1947).For example, a quantitative and mechanistic ...

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