Solar equivalent leaf area: an efficient biometrical parameter of individual leaves, trees and stands

Abstract

The solar equivalent leaf area (A(s)), a simply and easily determined biometrical parameter of leaves, trees and stands, was derived theoretically. The parameter is defined as projected leaf area weighted for the time integral of irradiance at a given location in the canopy relative to that of fully irradiated leaves at the top of the canopy. The efficiency of A(s) as a basis for estimating stand-area transpiration of a mature oak (Quercus robur L.) forest from measurements of transpiration by individual trees was compared with that of other stand and tree characteristics. Stand transpiration estimates based on A(s) were more precise and less prone to systematic error than estimates based on basal area, timber volume, projected tree crown area, projected leaf area, or leaf dry mass. Solar equivalent leaf area reflects both the amount and the physiological properties of leaves and can be used as a measure of tree size and functional capacity. It can be calculated from ordinary forest inventory data on trees and stands, adjusted according to simple phyllometric data. It appears to have wide application in ecological and forestry studies for relating the physiological characteristics of individual leaves to those of entire trees or stands.

Sapflow measurements in forest stands: methods and uncertainties

“…Structural scaling factors usually used are tree basal area, volume or tree circumference [11,18], the tree sapwood area [37] or leaf area [43]. Cermák [10] could demonstrate that sapflow rates related to solar equivalent leaf area were less prone to systematic errors than flow rates related to stem or crown size parameters. In dry habitats, leaf area may be a worse scalar owing to pronounced changes in transpiration per leaf area during drought [44].…”

Open field-applicable instrumental methods for structural and functional assessment of whole trees and stands

“…This is also reflected by leaf morphology, e.g., leaf thickness (mm) or leaf dry weight per area (g m -2 ). When directly measured irradiance or, more precisely, net irradiance data (I in J m -2 d ] can be applied as an approximate, but field applicable measure of relative irradiance (Cermák 1989(Cermák , 1998. This also fits for coniferous species when modified accordingly as dry mass per unit length of shoot ([g m -1 ] - Sprugel et al 1998).…”

“…) are almost linearly dependent on Irel (in %max) and therefore these morphological parameters can be applied for its estimates (Cermák 1989, 1998, Tselniker & Malkina 1992, Sprugel et al 1998. The values are usually quite variable because they are sensitive to small differences in irradiation across the given canopy layer height; where leaves are sampled.…”

“…When irradiance data at different heights above ground are not available (which is the usual case in open forests), this question can be solved with acceptable error by deriving approximate values from leaf biometric parameters, which depend on internal shading of neighboring tree branches and neighboring trees. For example, the measured leaf dry weight per area (ρd, in g m -2) and the dry weight of the unit length of shoots (g m -1) are almost linearly dependent on Irel (in %max) and therefore these morphological parameters can be applied for its estimates (Cermák 1989, 1998, Tselniker & Malkina 1992, Sprugel et al 1998. The values are usually quite variable because they are sensitive to small differences in irradiation across the given canopy layer height; where leaves are sampled.…”

The effect of light acclimation of single leaves on whole tree growth and competition - an application of the tree growth model ALMIS

“…4,5,22,31]. For example, such differences were observed in Fagus sylvatica, Quercus robur and Acer saccharum [8,13,38]. For trees of a given leaf area, shade acclimation has been shown to enhance carbon gain of the whole plant [2,7,35].…”