Journal ArticleDOI
Plant canopy gap-size analysis theory for improving optical measurements of leaf-area index.
Jing M. Chen,Josef Cihlar +1 more
TLDR
A new gap-size-analysis theory is presented to quantify the effect of canopy architecture on optical measurements of LAI based on the gap-fraction principle and can be used for any heterogeneous canopies.Abstract:
Optical instruments currently available for measuring the leaf-area index (LAI) of a plant canopy all utilize only the canopy gap-fraction information. These instruments include the Li-Cor LAI-2000 Plant Canopy Analyzer, Decagon, and Demon. The advantages of utilizing both the canopy gap-fraction and gap-size information are shown. For the purpose of measuring the canopy gap size, a prototype sunfleck–LAI instrument named Tracing Radiation and Architecture of Canopies (TRAC), has been developed and tested in two pure conifer plantations, red pine (Pinus resinosa Ait.) and jack pine (Pinus banksiana Lamb). A new gap-size-analysis theory is presented to quantify the effect of canopy architecture on optical measurements of LAI based on the gap-fraction principle. The theory is an improvement on that of Lang and Xiang [Agric. For. Meteorol. 37, 229 (1986)]. In principle, this theory can be used for any heterogeneous canopies.read more
Citations
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Journal ArticleDOI
Review of methods for in situ leaf area index (LAI) determination: Part II. Estimation of LAI, errors and sampling
TL;DR: In this paper, the theoretical background of modeling the gap fraction and the leaf inclination distribution is presented and different techniques used to derive leaf area index (LAI) and leaf inclination angle from gap fraction measurements are reviewed.
Journal ArticleDOI
Leaf area index of boreal forests: theory, techniques, and measurements
TL;DR: In this article, the authors evaluate the results obtained by several research teams using different methods for a broad spectrum of boreal forest types in support of the international Boreal Ecosystem-Atmosphere Study (BOREAS).
Journal ArticleDOI
Retrieving Leaf Area Index of Boreal Conifer Forests Using Landsat TM Images
Jing M. Chen,Josef Cihlar +1 more
TL;DR: In this paper, the authors used the TRAC (Tracing Radiation and Architecture of Canopies) to quantify the effect of canopy architecture on optical measurements of leaf area index, and found that effective LAI is less variable and easier to measure than LAI, and is also an intrinsic attribute of plant canopies.
Journal ArticleDOI
Evaluation of Vegetation Indices and a Modified Simple Ratio for Boreal Applications
TL;DR: In this article, un ratio simple modifie (MSR) is proposed for extraire les parametres biophysiques des forets boreales a l'aide de donnees de teledetection.
Journal ArticleDOI
Sources of variability in canopy reflectance and the convergent properties of plants
TL;DR: Current understanding of plant spectral properties with respect to sources of uncertainty at leaf to canopy scales is reviewed and a pattern that emerges suggests a synergy among the scattering effects of leaf-, stem- and canopy-level traits that becomes most apparent in the near-infrared (NIR) region.
References
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Journal ArticleDOI
Defining leaf area index for non‐flat leaves
Jing M. Chen,T. A. Black +1 more
TL;DR: In this article, the projection coefficients of several objects including spheres, cylinders, hemicircular cylinders, and triangular and square bars are investigated through mathematical derivation and numerical calculation for a range of ellipsoidal angular distributions.
Journal ArticleDOI
A theoretical analysis of the frequency of gaps in plant stands
TL;DR: Theoretical problems of the penetration of direct solar radiation and diffuse skylight in relation to the geometrical structure of the plant stand are considered in this paper, where a new formula for the gap frequency and corresponding models of stand geometry based on the theory of Markov processes are also proposed.
Journal ArticleDOI
Remote sensing of temperate coniferous forest leaf area index The influence of canopy closure, understory vegetation and background reflectance
TL;DR: In this article, the effects of canopy closure, understory vegetation, and background reflectance on the relationship between Landsat TM data and the leaf area index (LAI) of temperate coniferous forests in the western U.S.