Tree Density and Forest Productivity in a Heterogeneous Alpine Environment: Insights from Airborne Laser Scanning and Imaging Spectroscopy

We outline an approach combining airborne laser scanning (ALS) and imaging spectroscopy (IS) to quantify and assess patterns of tree density (TD) and forest productivity (FP) in a protected heterogeneous alpine forest in the Swiss National Park (SNP). We use ALS data and a local maxima (LM) approach...

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Bibliographic Details
Published in:Forests 2017-06, Vol.8 (6), p.212
Main Authors: Fatehi, Parviz, Damm, Alexander, Leiterer, Reik, Pir Bavaghar, Mahtab, Schaepman, Michael, Kneubühler, Mathias
Format: Article
Language:English
Subjects:
Airborne lasers
Alpine environments
Carbon
Data processing
Density
Dependence
Ecologists
Ecosystems
Elevation
Estimates
Forest productivity
Forests
Heterogeneity
Mapping
National parks
Photosynthesis
Productivity
Remote sensing
Resource availability
Satellites
Scanning
Sensitivity
Species composition
Spectroscopy
Timber
Topography
Trees
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Summary:We outline an approach combining airborne laser scanning (ALS) and imaging spectroscopy (IS) to quantify and assess patterns of tree density (TD) and forest productivity (FP) in a protected heterogeneous alpine forest in the Swiss National Park (SNP). We use ALS data and a local maxima (LM) approach to predict TD, as well as IS data (Airborne Prism Experiment—APEX) and an empirical model to estimate FP. We investigate the dependency of TD and FP on site related factors, in particular on surface exposition and elevation. Based on reference data (i.e., 1598 trees measured in 35 field plots), we observed an underestimation of ALS-based TD estimates of 40%. Our results suggest a limited sensitivity of the ALS approach to small trees as well as a dependency of TD estimates on canopy heterogeneity, structure, and species composition. We found a weak to moderate relationship between surface elevation and TD (R2 = 0.18–0.69) and a less pronounced trend with FP (R2 = 0.0–0.56), suggesting that both variables depend on gradients of resource availability. Further to the limitations faced in the sensitivity of the applied approaches, we conclude that the combined application of ALS and IS data was convenient for estimating tree density and mapping FP in north-facing forested areas, however, the accuracy was lower in south-facing forested areas covered with multi-stemmed trees.
ISSN:1999-4907
1999-4907
DOI:10.3390/f8060212