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Biological and environmental controls of the isotopic time lag between assimilation and respiration

English title Biological and environmental controls of the isotopic time lag between assimilation and respiration
Applicant Buchmann Nina
Number 105273
Funding scheme Project funding (Div. I-III)
Research institution Departement Umweltsystemwissenschaften ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Ecology
Start/End 01.01.2005 - 29.02.2008
Approved amount 231'114.00
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All Disciplines (2)

Discipline
Ecology
Botany

Keywords (5)

ecosystem physiology; biospheric-atmospheric exchange; functional biodiversity; stable isotopes; plant ecophysiology

Lay Summary (English)

Lead
Lay summary
Current changes in global climate and land use/land cover require aprofound understanding of the CO2 exchange of terrestrial ecosystems withthe atmosphere. Assessing the isotopic signature of ecosystem CO2 exchange(isofluxes) with experimental approaches in the field provided a firstglimpse on the control factors of ecosystem physiology, although themechanistic understanding about the direct or indirect effects ofbiological and environmental factors on ecosystem isofluxes is stilllimited. The best, but at the same time the only example of direct controlso far has been atmospheric vapor pressure deficit affecting the isotopicsignature of ecosystem respiration (13CR) with a time lag of 4 to10 days. This pronounced isotopic link between canopy assimilation andmainly belowground ecosystem respiration is strongly supported byindependent measurements as well. However, all results at the ecosystem,but also at the plant level indicate that our physiological understandingof isotopic time lags between assimilation and respiration is ratherpoorly, limited to only a handful plant species, and insufficient in timeresolution. Thus, we lack basic information about the isotopic signaturesalong the atmosphere-assimilate-organic matter-respiration chain, and thephysiological links and controls of the isotopic time lags betweenassimilation and respiration.

In the proposed project, biological and environmental controls of theisotopic time lags in (eco)system physiology will be assessed with thefollowing objectives
•to determine isotopic signatures of organic materials and respired CO2and their natural variability along the atmosphere-assimilate-organicmatter-respiration chain,
•to identify the length of the time lag between the environmental factorsaffecting leaf or canopy photosynthesis and the change in isotopicsignatures of respired CO2 of plants and soils, and
•to assess environmental and biotic factors influencing the time lag ofthe isotopic link between assimilation and respiration.

The study will be carried out using climate chambers. Several stand-aloneexperiments will be performed with different plant species (trees, herbsand grasses) to test for ecological generalization or life form specifictraits. Environmental conditions (climate control, nutrient and wateravailability), but also biological factors (plant age, plant phenologicalstage, source/sink relationships via leaf area reduction) will bemanipulated to induce and monitor isotopic time lags between assimilationand respiration. Stand-alone experiments will be carried out at varyingtime scales (from one day to several months). Different levels ofcomplexity will be studied (pots with only soil, pots with only plants butno soil, pots with soil and plants) to separate the response of variousecosystem components.

The expected outcome, i.e., profound mechanistic understanding of theunderlying principles of ecosystem CO2 exchange, will help to constrainecosystem models and solve current discrepancies on mean residence timesand therefore sequestration potentials of carbon in terrestrialecosystems.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Effects of ontogeny on δ13C of plant- and soil-respired CO2 and on respiratory carbon fractionation in C3 herbaceous species
Salmon Y Buchmann N Barnard RL (2016), Effects of ontogeny on δ13C of plant- and soil-respired CO2 and on respiratory carbon fractionation in C3 herbaceous species, in PLoS ONE, 11, 1-20.
Physiological controls of the isotopic time lag between leaf assimilation and soil CO2 efflux
Salmon Y Barnard R Buchmann N (2014), Physiological controls of the isotopic time lag between leaf assimilation and soil CO2 efflux, in Functional Plant Biology, 41, 850-859.
Carbon allocation and carbon isotope fluxes in the plant–soil–atmosphere continuum: a review
Brüggemann N Gessler A Kayler Z Keel SG Badeck F Barthel M Boeckx P Buchmann N Brugnoli E (2011), Carbon allocation and carbon isotope fluxes in the plant–soil–atmosphere continuum: a review, in Biogeosciences , 8, 3457-3489.
Ontogeny and leaf gas exchange mediate the carbon isotopic signature of herbaceous plants
Salmon Y Barnard R Buchmann N (2011), Ontogeny and leaf gas exchange mediate the carbon isotopic signature of herbaceous plants, in Plant, Cell and Environment, 34, 465-479.
Preparation of starch and soluble sugars of plant material for analysis of carbon isotope composition: a comparison of methods
Richter A Wanek W Werner RA Ghashghaie J Jäggi M Gessler A Brugnoli E Hettmann E Göttlicher (2009), Preparation of starch and soluble sugars of plant material for analysis of carbon isotope composition: a comparison of methods, in Rapid Communications in Mass Spectrometry, 23, 2476-2488.
Temporal dynamics of the carbon isotope composition in a Pinus sylvestris stand – from newly assimilated organic carbon to respired CO2
Kodama N Barnard RL Salmon Y Weston C Ferrio JP Holst J Werner RA Saurer M Rennenberg H Bu (2008), Temporal dynamics of the carbon isotope composition in a Pinus sylvestris stand – from newly assimilated organic carbon to respired CO2, in Oecologia , 156, 737-750.
Evaporative enrichment and time-lags between δ18O of leaf water and organic pools in a pine stand
Barnard RL Salmon Y Kodama N Sörgel K Rost J Rennenberg H Gessler A Buchmann N (2007), Evaporative enrichment and time-lags between δ18O of leaf water and organic pools in a pine stand, in Plant, Cell and Environment, 30, 539-550.

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