Co-Authors:
Sprintsin, M., Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, SedeBoqer Campus 84990, Israel
Cohen, S., Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Maseyk, K., Department of Environmental Sciences and Energy Research, Weizmann Institute of Science, Rehovot 76100, Israel, UMR 7618 Bioemco, Université Pierre et Marie Curie, Paris, France
Rotenberg, E., Department of Environmental Sciences and Energy Research, Weizmann Institute of Science, Rehovot 76100, Israel
Grünzweig, J., Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agricultural, Food and Environmental Quality Sciences, Hebrew University of Jerusalem, Rehovot 76100, Israel
Karnieli, A., Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, SedeBoqer Campus 84990, Israel
Berliner, P., Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, SedeBoqer Campus 84990, Israel
Yakir, D., Department of Environmental Sciences and Energy Research, Weizmann Institute of Science, Rehovot 76100, Israel
Abstract:
Effective leaf area index (LAIe) in the semi-arid Pinus halepensis plantation, located between arid and semi-arid climatic zones at the edge of the Negev and Judean deserts, was measured bi-annually during four years (2001-2004) and more intensively (monthly) during the following two years (2004-2006) by a number of non-contact optical devices. The measurements showed a gradual increase in LAIe from ∼1 (±0.25) to ∼1.8 (±0.11) during these years. All instruments, when used properly, gave similar results that were also comparable with actual leaf area index measured by litter collection and destructive sampling and allometric estimates. Because of the constraint of clear sky conditions, which limited the use of the fisheye type sensors to times of twilight, the fisheye techniques were less useful. The tracing radiation and architecture of canopies system, which includes specific treatment of two levels of clumpiness of the sparse forest stand, was used successfully for the intensive monitoring. The mean clumpiness index, 0.61, is considered representative for the specific environment. Finally, the LAIe measurements at the start of each season were used to constrain phenology-based estimates of annual LAIe development, resulting in a continuous course of LAIe in the forest over the five-year period. Intra-seasonal LAIe variation in the order of 10% of total LAIe predicted by the model was also observed in the intensive TRAC measurements, giving confidence in the TRAC system and indicating its sensitivity and applicability in woodlands even with low LAIe values. The results can be important for forest management decision support as well as for use in evaluation of remote sensing techniques for forests at the lowest range of LAIe values. © 2011 Elsevier B.V.
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