Increased nitrogen-use efficiency of a short-rotation poplar plantation in elevated CO2 concentration

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Tree Physiology, 27:1153–1163

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Increased nitrogen-use efficiency of a short-rotation poplar plantation in elevated CO₂ concentration

Carlo Calfapietra (1, 2), Paolo de Angelis (1), Birgit Gielen (3), Martin Lukac (4), Maria Cristina Moscatelli (5), Giuseppina Avino (1), Alessandra Lagomarsino (1), Andrea Polle (6), Reinhart Ceulemans (3), Giuseppe Scarascia Mugnozza (1, 7), Marcel R. Hoosbeek (8) and Maria Francesca Cotrufo (9)

1. University of Tuscia, Department of Forest Environment and Resources (DISAFRI), Via S. Camillo De Lellis, I-01100 Viterbo, Italy / 2. Corresponding author (carlocalf@unitus.it) / 3. University of Antwerpen, Campus Drie Eiken, Department of Biology, Research Group of Plant and Vegetation Ecology, Universiteitsplein 1, B-2610 Wilrijk, Belgium / 4. University of Wales, School of Agricultural and Forest Sciences, Bangor, Gwynedd LL57 2UW, United Kingdom / 5. University of Tuscia, Soil Biochemistry Laboratory, Department of Agrobiology and Agrochemistry, Via S. Camillo De Lellis, I-01100 Viterbo, Italy / 6. Institut für Forstbotanik, Georg-August Universität, Büsgenweg 2, 37077 Göttingen, Germany / 7. Institute of Agro-Environmental and Forest Biology – (IBAF-CNR), Via G. Marconi, 2 “Villa Paolina,” 05010 Porano (TR), Italy / 8. Wageningen University, Department of Environmental Sciences, Earth System Science Group, P.O. Box 37, 6700 AA Wageningen, The Netherlands / 9. Second University of Naples, Department of Environmental Sciences, Via Vivaldi 43, I-81100 Caserta, Italy / Received July 31, 2006; accepted October 23, 2006; published online May 1, 2007

Summary

We estimated nitrogen (N) use by trees of three poplar species exposed for 3 years to free air CO₂ enrichment (FACE) and determined whether the CO₂ treatment affected the future N availability of the plantation. Trees were harvested at the end of the first 3-year rotation and N concentration and content of woody tissues determined. Nitrogen uptake of fine roots and litter was measured throughout the first crop rotation. The results were related to previously published variations in soil N content during the same period. We estimated retranslocation from green leaves and processes determining N mobilization and immobilization, such as mineralization and nitrification, and N immobilization in litter and microbial biomass. In all species, elevated CO₂ concentration ([CO₂]) significantly increased nitrogen-use efficiency (NUE; net primary productivity per unit of annual N uptake), decreased N concentration in most plant tissues, but did not significantly change cumulative N uptake by trees over the rotation. Total soil N was depleted more in elevated [CO₂] than in ambient [CO₂], although not significantly for all soil layers. The effect of elevated [CO₂] was usually similar for all species, although differences among species were sometimes significant. During the first 3-year rotation, productivity of the plantation remained high in the elevated [CO₂] treatment. However, we observed a potential reduction in N availability in response to elevated [CO₂].

Keywords: nitrogen, FACE, Populus, SRF, NUE, N uptake.