A comparative analysis of image processing softwares to indirect estimation of leaf area index in forest ecosystems

Abstract

The leaf area of vegetation can be expressed in terms of leaf area index (LAI). This index depends on species
composition, developmental stage, prevailing site conditions, seasonality and management practices. LAI is
an important ecological parameter because vegetation-atmosphere processes of the canopy are controlled by
the foliage. It can be estimated with hemispherical photographs using some commercial and free softwares.
The choice of the software and the settings of parameters are two fundamental aspects to obtain suitable
data. The paper focuses on the comparative analysis of the LAI data obtained with three image processing
softwares (Spot Light Intercept Model, Gap Light Analyzer and WinScanopy) in a case study in Italy. The
data were analyzed in a qualitative and quantitative way. The Wilcoxon signed rank test showed statistically
significant differences among the three softwares. WinScanopy provides lower LAI values than the other two
softwares. The same non-parametric test distinguishing per forest type and forest age showed statistically
significant differences among softwares in three forest types (silver fir, Norway spruce and beech forests) and
in the young stands. Instead, no statistically significant differences were found in the mature stands.