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Estimating light climate in forest with the convex densiometer: operator effect, geometry and relation to diffuse light

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Abstract

Although light is a key factor in forestry, it is surprisingly seldom measured in day-to-day management of European forests. The spherical convex densiometer is a simple instrument that allows to evaluate the canopy openness (CO) by counting the number of ‘canopy’ dots on a grid lying on a convex mirror reflecting the canopy. In this contribution, we compared the performances of this instrument in mixed oak–beech hardwood forests spanning the lower end of the light gradient [1–17 % above canopy photosynthetically active radiation (PAR)] to two reference techniques: PAR measurements and fish-eye photography, based on a detailed analysis of its functioning. Discrepancies between the densiometer and the fish-eye estimates of CO were due to a combination of differences in dot resolution, dot counting and portion of the hemisphere considered. By contrast, the various effects of operator on densiometer estimates, including the influence of conformation on the angle of view, were found to be relatively minor. Densiometer readings were closely related to the relative light intensity assessed by PAR sensors in overcast conditions, which suggests that the use of this inexpensive tool should be expanded.

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Acknowledgments

We thank all the technical staff of the Forest Sciences team, in particular Cédric Daine for invaluable field and laboratory assistance for the treatment of the fish-eye pictures. The authors show gratitude to the Université catholique de Louvain for the financial support of this study. We also wish to thank two anonymous reviewers who provided useful comments on an earlier version of this paper. Projet cofinancé par le Fonds européen de développement régional et par la Région wallonne dans le cadre du programme INTERREG IV-A Grande Région. «L’Union européenne investit dans votre avenir». Gefördert durch den Europäischen Fonds für regionale Entwicklung und die wallonische Region im Rahmen des Programms INTERREG IV-A Großregion. «Die Europäische Union investiert in Ihre Zukunft».

Conflict of interest

Authors declare that they have no conflict of interest.

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Authors and Affiliations

  1. Earth and Life Institute, Environmental Sciences, Université catholique de Louvain, Croix du Sud 2/9, L7.05.09, 1348, Louvain-la-Neuve, Belgium

    Olivier Baudry, Charlotte Charmetant & Quentin Ponette

  2. INRA, UMR1092, Laboratoire d’Etude des Ressources Forêt Bois (LERFoB), Centre INRA de Nancy, 54280, Champenoux, France

    Catherine Collet

  3. AgroParisTech, UMR1092, Laboratoire d’Etude des Ressources Forêt Bois (LERFoB), ENGREF, 14 rue Girardet, 54000, Nancy, France

    Catherine Collet

Authors
  1. Olivier Baudry
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  2. Charlotte Charmetant
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  3. Catherine Collet
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  4. Quentin Ponette
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Corresponding author

Correspondence to Olivier Baudry.

Additional information

Communicated by C. Ammer.

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Baudry, O., Charmetant, C., Collet, C. et al. Estimating light climate in forest with the convex densiometer: operator effect, geometry and relation to diffuse light. Eur J Forest Res 133, 101–110 (2014). https://doi.org/10.1007/s10342-013-0746-6

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  • DOI: https://doi.org/10.1007/s10342-013-0746-6

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