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Assessment of soil nitrogen and phosphorous availability under elevated CO2 and N-fertilization in a short rotation poplar plantation
Lagomarsino, A. ; Moscatelli, M.C. ; Hoosbeek, M.R. ; Angelis, P. de; Grego, S. - \ 2008
Plant and Soil 308 (2008)1-2. - ISSN 0032-079X - p. 131 - 147.
microbial biomass-c - atmospheric co2 - enrichment face - arylsulfatase activity - organic-matter - carbon-dioxide - ponderosa pine - use efficiency - increases - forest
Photosynthetic stimulation by elevated [CO2] is largely regulated by nitrogen and phosphorus availability in the soil. During a 6 year Free Air CO2 Enrichment (FACE) experiment with poplar trees in two short rotations, inorganic forms of soil nitrogen, extractable phosphorus, microbial and total nitrogen were assessed. Moreover, in situ and potential nitrogen mineralization, as well as enzymatic activities, were determined as measures of nutrient cycling. The aim of this study was to evaluate the effects of elevated [CO2] and fertilization on: (1) N mineralization and immobilization processes; (2) soil nutrient availability; and (3) soil enzyme activity, as an indication of microbial and plant nutrient acquisition activity. Independent of any treatment, total soil N increased by 23% in the plantation after 6 years due to afforestation. Nitrification was the main process influencing inorganic N availability in soil, while ammonification being null or even negative. Ammonium was mostly affected by microbial immobilization and positively related to total N and microbial biomass N. Elevated [CO2] negatively influenced nitrification under unfertilised treatment by 44% and consequently nitrate availability by 30% on average. Microbial N immobilization was stimulated by [CO2] enrichment and probably enhanced the transformation of large amounts of N into organic forms less accessible to plants. The significant enhancement of enzyme activities under elevated [CO2] reflected an increase in nutrient acquisition activity in the soil, as well as an increase of fungal population. Nitrogen fertilization did not influence N availability and cycling, but acted as a negative feed-back on phosphorus availability under elevated CO2.
Increases in nitrogen uptake rather than nitrogen-use efficiency support higher rates of temperate forest productivity under elevated CO2
Finzi, A.C. ; Norby, R.J. ; Calfapietra, C. ; Gallet-Budynek, A. ; Gielen, B. ; Holmes, W.E. ; Hoosbeek, M.R. ; Iversen, C.M. ; Jackson, R.B. ; Kubiske, M.E. ; Ledford, J. ; Liberloo, M. ; Oren, R. ; Polle, A. ; Pritchard, S. ; Zak, D.R. ; Schlesinger, W.H. ; Ceulemans, R. - \ 2007
Proceedings of the National Academy of Sciences of the United States of America 104 (2007)35. - ISSN 0027-8424 - p. 14014 - 14019.
atmospheric carbon-dioxide - rotation poplar plantation - fine-root production - soil-n availability - enrichment face - populus-tremuloides - deciduous forest - organic nitrogen - community composition - ecosystem responses
Forest ecosystems are important sinks for rising concentrations of atmospheric CO2. In previous research, we showed that net primary production (NPP) increased by 23 ± 2% when four experimental forests were grown under atmospheric concentrations of CO2 predicted for the latter half of this century. Because nitrogen (N) availability commonly limits forest productivity, some combination of increased N uptake from the soil and more efficient use of the N already assimilated by trees is necessary to sustain the high rates of forest NPP under free-air CO2 enrichment (FACE). In this study, experimental evidence demonstrates that the uptake of N increased under elevated CO2 at the Rhinelander, Duke, and Oak Ridge National Laboratory FACE sites, yet fertilization studies at the Duke and Oak Ridge National Laboratory FACE sites showed that tree growth and forest NPP were strongly limited by N availability. By contrast, nitrogen-use efficiency increased under elevated CO2 at the POP-EUROFACE site, where fertilization studies showed that N was not limiting to tree growth. Some combination of increasing fine root production, increased rates of soil organic matter decomposition, and increased allocation of carbon (C) to mycorrhizal fungi is likely to account for greater N uptake under elevated CO2. Regardless of the specific mechanism, this analysis shows that the larger quantities of C entering the below-ground system under elevated CO2 result in greater N uptake, even in N-limited ecosystems. Biogeochemical models must be reformulated to allow C transfers below ground that result in additional N uptake under elevated CO2.
Woody biomass production during the second rotation of a bio-energy Populus plantation increases in a future high CO2 world
Liberloo, M. ; Calfapietra, C. ; Lukac, M. ; Godbold, D. ; Luos, Z.B. ; Polles, A. ; Hoosbeek, M.R. ; Kull, O. ; Marek, M. ; Rianes, Chr. ; Rubino, M. ; Taylors, G. ; Scarascia-Mugnozza, G. ; Ceulemans, R. - \ 2006
Global Change Biology 12 (2006)6. - ISSN 1354-1013 - p. 1094 - 1106.
elevated co2 - atmospheric co2 - poplar plantation - enrichment face - no3 availability - n-fertilization - hybrid poplar - water-stress - pinus-taeda - growth
The quickly rising atmospheric carbon dioxide (CO2)-levels, justify the need to explore all carbon (C) sequestration possibilities that might mitigate the current CO2 increase. Here, we report the likely impact of future increases in atmospheric CO2 on woody biomass production of three poplar species (Populus alba L. clone 2AS-11, Populus nigra L. clone Jean Pourtet and Populus×euramericana clone I-214). Trees were growing in a high-density coppice plantation during the second rotation (i.e., regrowth after coppice; 2002¿2004; POPFACE/EUROFACE). Six plots were studied, half of which were continuously fumigated with CO2 (FACE; free air carbon dioxide enrichment of 550 ppm). Half of each plot was fertilized to study the interaction between CO2 and nutrient fertilization. At the end of the second rotation, selective above- and belowground harvests were performed to estimate the productivity of this bio-energy plantation. Fertilization did not affect growth of the poplar trees, which was likely because of the high rates of fertilization during the previous agricultural land use. In contrast, elevated CO2 enhanced biomass production by up to 29%, and this stimulation did not differ between above- and belowground parts. The increased initial stump size resulting from elevated CO2 during the first rotation (1999¿2001) could not solely explain the observed final biomass increase. The larger leaf area index after canopy closure and the absence of any major photosynthetic acclimation after 6 years of fumigation caused the sustained CO2-induced biomass increase after coppice. These results suggest that, under future CO2 concentrations, managed poplar coppice systems may exhibit higher potential for C sequestration and, thus, help mitigate climate change when used as a source of C-neutral energy.