Aubinet, Marc

Heinesch, Bernard

Jockheere, Inge

Laffineur, Quentin

Simpraga, Maja

Soubie, Remy

Steppe, Kathy

Verbeeck, Hans

Vincke, Carioline

English

Ghent University Academic Bibliography

Seasonal variation of LAI in the footprint of a flux measurement tower   Šimpraga Maja1, Verbeeck Hans1, Soubie Rémy2, Heinesch Bernard3, Jonckheere Inge4, Laffineur Quentin3, Aubinet Marc3, Vincke Caroline2, Steppe Kathy1   1Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000 Gent, Belgium 2 Université catholique de Louvain, Earth and Life Institute, Environmental Sciences. Croix du Sud, 2/9, 1348 Louvain-la-Neuve, Belgium 3Unité de Physique des Biosystèmes, Gembloux Agro-Bio Tech, Université de Liège, Gembloux, Belgium 4 FAO, Environment, Climate Change and Bioenergy Division (NRCD), Viale delle Terme di Caracalla, Rome Italy   Tel: +32 9 264 61 13  E-mail: maja.simpraga@ugent.be Functie: wetenschappelijk medewerkster Project: IMPECVOC project (www.impecvoc.ugent.be) promotors: Prof. dr. ir. Kathy Steppe, Dr. Hans Verbeeck  Forests, throughout the year, undergo different phenological stages. These seasonal phenology patterns, in deciduous, coniferous and/or mixed forests, should be considered in modelling studies of carbon, water, energy and biogenic volatile organic compound fluxes. Estimates of leaf (needle) area are used to follow the phenological development of forest stands. Moreover, leaf area index is an important parameter for the integration and upscaling of different ecological processes. We performed a structural analysis of the forest canopy by using different non-destructive methods, namely hemispherical photography (HP), LAI-2200 and understory intercepted photosynthetically active radiation (PAR) measurements (Pontallier et al., 2003). The main objective of this study was to quantify temporal variability of LAI and to compare these three different methods.  LAI is defined as the leaf area (m²) per unit of ground area (m²) and it is known that it varies seasonally (Jonckheere et al., 2004). In literature different indices are used to study leaf area. Attention should be paid to which definition is used (Asner et al., 2003): plant area index (PAI) (Holst et al., 2004), leaf area index (LAI) (Mussche et al., 2004) or vegetation area index (VAI) (Fassnacht et al., 1994), being the most common indices. Measurements were done in the experimental forest of Vielsalm, located in the Belgian Ardennes (50°18’N, 6°00’E, altitude: 450m) described in detail in Aubinet et al. (2001). The footprint of the flux tower in this forest was divided into four transect subplots with five sampling points per transect. The distance between each point was 15 meters. In total 43 sampling points were divided and located using a GPS. The HP and LAI-2200 were carried out at nine dates on a monthly basis, while PAR measurements were logged automatically throughout the phenological year 2010. During the course of one year, we observed a pronounced seasonal bell-shaped LAI variation for all three techniques used. Clearly, seasonal vegetation area index can be classified into three phenological periods: leaf production, leaf maturity and leaf senescence (Fig. 1). Interestingly, LAI-2200 showed a more rapid increase in spring  compared to HP and intercepted PAR. LAI reached a maximum value in summer and a minimum value in winter for all techniques. Some explanations for the observed difference between the three techniques were brought forward and several fundamental questions were addressed. The seasonal evolution of the LAI will be discussed for the deciduous subplot, including strengths and weaknesses of each technique.                         Day of the year (DOY)0 50 100 150 200 250 300 350 400LAI (m2  m-2)01234567Leaf production Leaf maturity Leaf senescence Figure 1: Leaf area index (LAI) of beech plot according to LAI-2000 (▲),  hemispherical photography (●) and intercepted PAR (□) in Vielsalm forest (Wallonia, Belgium) during the phenological year of 2010. Acknowledgements  The authors wish to acknowledge support from the Belgian Federal Science Policy Office in the framework of the project “Science for a Sustainable Development: Terrestrial Ecology” (IMPECVOC project, contract #SD/TE/03B) and the “FWO-Vlaanderen” (contract # G.0031.07). Additionally, we are thankful to Prof. em. Raoul Lemeur, Philip Deman, Geert Favyts, Michele Yernaux and Henri Chopin. References Asner, G., Scurlock, J., Hicke, J., 2003. Global synthesis of leaf area index observations: implications for ecological and remote sensing studies. Global Ecology and Biogeography 12, 191-205.  Aubinet M., Chermanne B., Vandenhaute M., Longdoz B., Yernaux M., Laitat E., 2001. Long term carbon dioxide exchange above a mixed forest in the Belgian Ardennes. Agricultural and Forest Meteorology 108, 293–315. Holst, T., Hauser, S., Kirchgaßner, A., Matzarakis, A., Mayer, H., Schindler, D., 2004. Measuring and modelling plant area index in beech stands. International Journal of Biometeorology 48, 192–201. Jonckheere, I., Fleck, S., Nackaerts, K., Muys, B., Coppin, P., Weiss, M., Baret, F., 2004. Review of methods for in situ leaf area index determination. Part I. Theories, sensors and hemispherical photography. Agricultural and Forest Meteorology 121, 19-35.  Mussche, S., Samson, R., Nachtergale, L., De Schrijver, A., Lemeur, R., Lust, N.A., 2001. Comparison of optical and direct methods for monitoring the seasonal dynamics of leaf area index in deciduous forests. Silva Fennica 35, 373–384. Pontailler, J-Y., Hymus, J. G., Drake, B. G., 2003. Estimation of leaf area index using ground-based remote sending NDVI measurements: validation and comparison with two indirect techniques. Canadian Journal of Remote Sensing 29, 381-387. 

Seasonal variation of LAI in the footprint of a flux measurement tower

Simpraga, Maja0020037964928010018951939797098500450000-0002-6972-4598F743CB3C-F0ED-11E1-A9DE-61C894A0A6B4

Verbeeck, HansLA200019973752948010017128160000-0003-1490-0168FBB1ED20-F0ED-11E1-A9DE-61C894A0A6B4

Steppe, KathyLA218010014612220000-0001-6252-0704F605A5E2-F0ED-11E1-A9DE-61C894A0A6B4

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https://biblio.ugent.be/publication/1209489/file/1209491.pdf

Seasonal variation of LAI in the footprint of a flux measurement tower

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