Seasonal soil and leaf CO2 exchange rates in a Mediterranean holm oak forest and their responses to drought conditions |
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| Affiliation: | 1. Department of Science and Agroforestry Technology and Genetics, Higher Technical School of Agricultural and Forestry Engineering, University of Castilla-La Mancha, Campus Universitario s/n, CP 02071 Albacete, Spain;2. Environmental Department, Renewable Energy Research Institute, University of Castilla-La Mancha, Campus Universitario s/n, CP 02071 Albacete, Spain;3. Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 1627, 70211 Kuopio, Finland;4. Department of Applied Physics, School of Industrial Engineering, University of Castilla-La Mancha, Campus Universitario s/n, CP 02071 Albacete, Spain;1. Tiantong National Field Observation Station for Forest Ecosystem, School of Ecological and Environmental Sciences, East China Normal University, Shanghai 200062, China;2. School of Life Sciences, Anhui Agricultural University, Hefei, Anhui Province, 230036, China;3. Center for Global Change and Ecological Forecasting, East China Normal University, Shanghai 200062, China;4. Coastal Ecosystems Research Station of Yangtze River Estuary, Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, The Institute of Biodiversity Science, Fudan University, 220 Handan Road, Shanghai 200433, China;5. The Shanghai Key Lab for Urban Ecological Processes and Eco-Restoration (SHUES), East China Normal University, Shanghai 2000241, China;1. Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, 99354, USA;2. CREAF, Global Ecology Unit CRAF-CSIC-UAB, Cerdanyola del Vallès, 08913 Catalonia, Spain;3. CSIC, Global Ecology Unit CREAF-CSIC-UAB, Cerdanyola del Vallès, 08913 Catalonia, Spain;4. Department of Earth System Science, University of California, Irvine, CA, 92697, USA;5. Global Change Research Institute, Czech Academy of Sciences, Bĕlidla 4a, CZ-603 00 Brno, Czech Republic;1. Department of Plant Production and Agricultural Technology, School of Advanced Agricultural Engineering, Castilla La Mancha University, Campus Universitario s/n, CP 02071 Albacete, Spain;2. Department of Agroforestry Technology and Science and Genetics, School of Advanced Agricultural Engineering, Castilla La Mancha University, Campus Universitario s/n, CP 02071 Albacete, Spain;1. Department of Forest and Ecosystem Science, The University of Melbourne, 4 Water Street, Creswick 3363, VIC, Australia;2. Department of Forest and Ecosystem Science, The University of Melbourne, 500 Yarra Boulevard, Richmond 3121, VIC, Australia;3. Department of Resource Management and Geography, The University of Melbourne, 500 Yarra Boulevard, Richmond 3121, VIC, Australia;1. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China;2. Department of Ecology, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China;3. University of Chinese Academy of Sciences, Beijing, 100049, China;4. College of Chinese Language and Culture, Jinan University, Guangzhou, 510610, China;5. Research Center for Global Change and Ecological Forecasting, School of Ecological and Environmental Sciences, East China Normal University, Shanghai 200062, China |
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| Abstract: | We measured the soil and leaf CO2 exchange in Quercus ilex and Phillyrea latifolia seasonally throughout the year in a representative site of the Mediterranean region, a natural holm oak forest growing in the Prades Mountains in southeastern Catalonia. In the wet seasons (spring and autumn), we experimentally decreased soil moisture by 30%, by excluding rainfall and water runoff in 12 plots, 1×10 m, and left 12 further plots as controls. Our aim was to predict the response of these gas exchanges to the drought forecasted for the next decades for this region by GCM and ecophysiological models.Annual average soil CO2 exchange rate was 2.27±0.27 μmol CO2 m−2 s−1. Annual average leaf CO2 exchange rates were 8±1 and 5±1 μmol m−2 s−1 in Q. ilex and P. latifolia, respectively. Soil respiration rates in control treatments followed a seasonal pattern similar to photosynthetic activity. They reached maximum values in spring and autumn (2.5–3.8 μmol m−2 s−1 soil CO2 emission rates and 7–15 μmol m−2 s−1 net photosynthetic rates) and minimum values (almost 0 for both variables) in summer, showing that soil moisture was the most important factor driving the soil microbial activity and the photosynthetic activity of plants. In autumn, drought treatment strongly decreased net photosynthesis rates and stomatal conductance of Q. ilex by 44% and 53%, respectively. Soil respiration was also reduced by 43% under drought treatment in the wet seasons. In summer there were larger soil CO2 emissions in drought plots than in control plots, probably driven by autotrophic (roots) metabolism. The results indicate that leaf and soil CO2 exchange may be strongly reduced (by ca. 44%) by the predicted decreases of soil water availability in the next decades. Long-term studies are needed to confirm these predictions or to find out possible acclimation of those processes. |
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