Measurement methods and variability assessment of the Norway spruce total leaf area: implications for remote sensing |
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Authors: | Lucie Homolová Petr Lukeš Zbyněk Malenovský Zuzana Lhotáková Věroslav Kaplan Jan Hanuš |
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Affiliation: | 1. Laboratory of Geo-Information Science and Remote Sensing, Wageningen University, Droevendaalsesteeg 3, 6708 PB, Wageningen, The Netherlands 2. Remote Sensing Laboratories, Department of Geography, University of Zürich, Winterthurerstrasse 190, 8057, Zurich, Switzerland 3. Global Change Research Centre, Academy of Sciences of the Czech Republic, Bělidla 986/4a, 60300, Brno, Czech Republic 4. School of Geography and Environmental Studies, University of Tasmania, Private Bag 76, Hobart, 7001, Australia 5. Department of Experimental Plant Biology, Faculty of Science, Charles University in Prague, Vini?ná 5, Prague, Czech Republic
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Abstract: | Estimation of total leaf area (LAT) is important to express biochemical properties in plant ecology and remote sensing studies. A measurement of LAT is easy in broadleaf species, but it remains challenging in coniferous canopies. We proposed a new geometrical model to estimate Norway spruce LAT and compared its accuracy with other five published methods. Further, we assessed variability of the total to projected leaf area conversion factor (CF) within a crown and examined its implications for remotely sensed estimates of leaf chlorophyll content (C ab). We measured morphological and biochemical properties of three most recent needle age classes in three vertical canopy layers of a 30 and 100-year-old spruce stands. Newly introduced geometrical model and the parallelepiped model predicted spruce LAT with an error <5 % of the average needle LAT, whereas two models based on an elliptic approximation of a needle shape underestimated LAT by up to 60 %. The total to projected leaf area conversion factor varied from 2.5 for shaded to 3.9 for sun exposed needles and remained invariant with needle age class and forest stand age. Erroneous estimation of an average crown CF by 0.2 introduced an error of 2–3 μg cm?2 into the crown averaged C ab content. In our study, this error represents 10–15 % of observed crown averaged C ab range (33–53 μg cm?2). Our results demonstrate the importance of accurate LAT estimates for validation of remotely sensed estimates of C ab content in Norway spruce canopies. |
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