Leaf area index measurements
نویسندگان
چکیده
Leaf area index (LAI) is a key structural characteristic of forest ecosystems because of the role of green leaves in controlling many biological and physical processes in plant canopies. Accurate LA1 estimates are required in studies of ecophysiology, atmosphere-ecosystem interactions, and global change. The objective of this paper is to evaluate LA1 values obtained by several research teams using different methods for a broad spectrum of boreal forest types in support of the international Boreal EcosystemAtmosphere Study (BOREAS). These methods include destructive sampling and optical instruments: the tracing radiation and architecture of canopies (TRAC), the LAI-2000 plant canopy analyzer, hemispherical photography, and the Sunfleck Ceptometer. The latter three calculate LA1 from measured radiation transmittance (gap fraction) using inversion models that assume a random spatial distribution of leaves. It is shown that these instruments underestimate LA1 of boreal forest stands where the foliage is clumped. The TRAC quantifies the clumping effect by measuring the canopy gap size distribution. For deciduous stands the clumping index measured from TRAC includes the clumping effect at all scales, but for conifer stands it only resolves the clumping effect at scales larger than the shoot (the basic collection of needles). To determine foliage clumping within conifer shoots, a video camera and rotational light table system was used. The major difficulties in determining the surface area of small conifer needles have been largely overcome by the use of an accurate volume displacement method. Hemispherical photography has the advantage that it also provides a permanent image record of the canopies. Typically, LA1 falls in the range from 1 to 4 for jack pine and aspen forests and from 1 to 6 for black spruce. Our comparative studies provide the most comprehensive set of LA1 estimates available for boreal forests and demonstrate that optical techniques, combined with limited direct foliage sampling, can be used to obtain quick and accurate LA1 measurements.
منابع مشابه
Sugar beet response to N fertilization as assessed by late season chlorophyll and leaf area index measurements in a semi-arid environment
In a 3-year experiment (2002-2004), five N rates (0, 60, 120, 180, 240 kg N ha-1) were applied to sugar beets arranged in a Randomized Complete Block design with six replications. Experimentation took place under the semi-arid, irrigated conditions of central Greece. The aim of this work was to study the late season response of sugar beet crop to N fertilization as assessed by non-destructive m...
متن کاملLeaf area relationships to plant vegetative characteristics in cotton (Gossypium hirsutum L.) grown in a temperate sub-humid environment
Measurement or estimation of leaf area is essential for understanding crop responses to experimental treatments. The objective of this study was to develop regression models for estimating leaf area of field-grown cotton (Gossypium hirsutum L.) from measurements of leaf dry weight (LDW), vegetative components (stems and leaves) dry weight (VDW) and plant height (PH). Three cotton cultivars (Del...
متن کاملCrown structure and leaf area index development in thinned and unthinned Eucalyptus nitens plantations.
The crown structure of Eucalyptus nitens (Deane & Maiden) Maiden 6 years after thinning, and the development of stand leaf area index both immediately and 6 years after thinning, were investigated. Thinning did not alter branch angle, branching density or the relationship between branch size and branch leaf area. However, larger branches were found in the lower crown of thinned trees and the in...
متن کاملLeaf Area, Leaf Area Index and Light Extinction Coefficient for Taro Culture
Taro, Colocasia esculenta (L.) Schott, is the most important species from the Araceae family. The leaf area (LA) is important for the interception of solar radiation and for the biomass production. The light extinction coefficient (k) is related to the leaf inclination angle, leaf arrangement, regarding the Leaf Area Index (LAI), providing an indication of the plants efficiency on intercepting ...
متن کاملDigital Cover Photography for Estimating Leaf Area Index (LAI) in Apple Trees Using a Variable Light Extinction Coefficient
Leaf area index (LAI) is one of the key biophysical variables required for crop modeling. Direct LAI measurements are time consuming and difficult to obtain for experimental and commercial fruit orchards. Devices used to estimate LAI have shown considerable errors when compared to ground-truth or destructive measurements, requiring tedious site-specific calibrations. The objective of this study...
متن کامل