HR: 17:00h
AN: B24A-05    [Abstracts]
TI: Nitrogen deposition and photosynthetic performance relations at high-N-loading forests in Switzerland and at a highly variable-N-loading Rocky Mtn. subalpine forest: Fluorometry and the estimation of photosynthetic-efficiency-based critical N loads
AU: * Sievering, H
EM: herman.sievering@cudenver.edu
AF: Long-Term Ecol. Res. Prog., INSTAAR, Univ. of Colorado, UCB 450, Boulder, CO 80303, United States
AU: * Sievering, H
EM: herman.sievering@cudenver.edu
AF: Dept.s of Geography & Environmental Science and of Physics, Univ. of Colorado, Denver & Boulder, CO 80217, United States
AU: * Sievering, H
EM: herman.sievering@cudenver.edu
AF: Plant Sciences, Swiss Inst. of Technology (ETH), Universitatstrasse, Zurich, Alp 8037, Switzerland
AU: Eugster, W
EM: w.eugster@eth.ch
AF: Plant Sciences, Swiss Inst. of Technology (ETH), Universitatstrasse, Zurich, Alp 8037, Switzerland
AU: Balster, H
EM: hugo.balster@colorado.edu
AF: Long-Term Ecol. Res. Prog., INSTAAR, Univ. of Colorado, UCB 450, Boulder, CO 80303, United States
AU: Tomaszewski, T
EM: tim.tomaszewski@colorado.edu
AF: Long-Term Ecol. Res. Prog., INSTAAR, Univ. of Colorado, UCB 450, Boulder, CO 80303, United States
AU: Schleppi, P
EM: patrick.schleppi@wsl.ch
AF: Swiss Federal Inst. of Forest, Snow and Landscape Res. (WSL), Birmensdorferstrasse, Birmensdorf, Alp 8069, Switzerland
AU: Waldner, P
EM: peter.waldner@wsl.ch
AF: Swiss Federal Inst. of Forest, Snow and Landscape Res. (WSL), Birmensdorferstrasse, Birmensdorf, Alp 8069, Switzerland
AU: Thimonier, A
EM: anne.thimonier@wsl.ch
AF: Swiss Federal Inst. of Forest, Snow and Landscape Res. (WSL), Birmensdorferstrasse, Birmensdorf, Alp 8069, Switzerland
AU: Buchmann, N
EM: nina.buchmann@eth.ch
AF: Plant Sciences, Swiss Inst. of Technology (ETH), Universitatstrasse, Zurich, Alp 8037, Switzerland
AB: Chlorophyll fluorescence (fluorometry) for quantitative plant photosynthetic performance determination is widely accepted in the biological sciences but less so for ecosystem analysis studies. Portable fluorometry has provided plant photosynthetic performance and plant stress status data in a small number of eco-physiological field studies that have investigated several specific atmospheric pollutants' impacts at forested ecosystems. We used fluorometry in N-amendment studies at forest canopies (where amended N is best applied to consider atmospheric N deposition impacts at forested ecosystems). Fluorometry measurements in the context of canopy N-amendment studies have been undertaken at the Niwot (LTER) Colorado subalpine forest (Sievering etal.: Part I, Tellus B 59(3), 483-492; Tomaszewski and Sievering: Part II, Tellus B 59 (3), 493-505) and, more recently, in Europe at several Swiss ILTER forest ecosystems. Our fluorometry measurements have shown (among other results to be presented): ▪ N amendments increased photosynthetic efficiency at the Niwot LTER subalpine forest. Modeling analysis indicates amended N enhanced needle Rubisco content and increased photosynthetic efficiency at this N-limited and 7 kgN ha-1 yr-1 (wet+dry) N loading Spruce-Fir subalpine forest ecosystem; ▪ Beech, Oak and Spruce trees responded differently to N amendments of about twice (wet+fog) growing- season N deposition at Swiss forest ecosystems receiving 20-35 kgN ha-1 annual N loadings.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0469 Nitrogen cycling
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting