Soil matrix tracer contamination and canopy recycling did not impair13CO2plant–soil pulse labelling experiments

Barthel, Matthias; Sturm, Patrick; Knohl, Alexander

doi:10.1080/10256016.2011.587610

Cited by 10 publications

(7 citation statements)

References 17 publications

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“…The measurement sequence of soil and canopy chambers as well as sensor recording was fully automated and controlled by a custom‐written L ab V iew program (National Instruments Corp., Austin, TX, USA). A detailed description of the set‐up can be found in Barthel et al. (2011).…”

Section: Methodsmentioning

confidence: 99%

The diel imprint of leaf metabolism on the δ¹³C signal of soil respiration under control and drought conditions

et al. 2011

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Summary• Recent 13 CO 2 canopy pulse chase labeling studies revealed that photosynthesis influences the carbon isotopic composition of soil respired CO 2 (d 13 C SR ) even on a diel timescale. However, the driving mechanisms underlying these short-term responses remain unclear, in particular under drought conditions.• The gas exchange of CO 2 isotopes of canopy and soil was monitored in drought ⁄ nondrought-stressed beech (Fagus sylvatica) saplings after 13 CO 2 canopy pulse labeling. A combined canopy ⁄ soil chamber system with gas-tight separated soil and canopy compartments was coupled to a laser spectrometer measuring mixing ratios and isotopic composition of CO 2 in air at high temporal resolution. The measured d 13 C SR signal was then explained and substantiated by a mechanistic carbon allocation model.• Leaf metabolism had a strong imprint on diel cycles in control plants, as a result of an alternating substrate supply switching between sugar and transient starch. By contrast, diel cycles in drought-stressed plants were determined by the relative contributions of autotrophic and heterotrophic respiration throughout the day. Drought reduced the speed of the link between photosynthesis and soil respiration by a factor of c. 2.5, depending on the photosynthetic rate.• Drought slows the coupling between photosynthesis and soil respiration and alters the underlying mechanism causing diel variations of d 13 C SR .

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Section: Methodsmentioning

confidence: 99%

The diel imprint of leaf metabolism on the δ¹³C signal of soil respiration under control and drought conditions

et al. 2011

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“…The temporal resolution and precision depends on the integration-time and instrument (e.g. 0.25 ‰ at 1 s and about 0.08 ‰ at 30 min integration time for δ 13 C and δ 18 O in CO 2 with a TDLS; Barthel et al, 2011b). High temporal resolution measurements of δ 13 C res determined in non-equilibrated closed chambers (e.g.…”

Section: New Methodological Developments In High Time-resolved Measurmentioning

confidence: 99%

Diel variations in the carbon isotope composition of respired CO2 and associated carbon sources: a review of dynamics and mechanisms

Werner

Geßler

2011

Biogeosciences

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Abstract. Recent advances have improved our methodological approaches and theoretical understanding of postphotosynthetic carbon isotope fractionation processes. Nevertheless we still lack a clear picture of the origin of shortterm variability in δ 13 C of respired CO 2 (δ 13 C res ) and organic carbon fractions on a diel basis. Closing this knowledge gap is essential for the application of stable isotope approaches for partitioning ecosystem respiration, tracing carbon flow through plants and ecosystems and disentangling key physiological processes in carbon metabolism of plants. In this review we examine the short-term dynamics in δ 13 C res and putative substrate pools at the plant, soil and ecosystem scales and discuss mechanisms, which might drive diel δ 13 C res dynamics at each scale. Maximum reported variation in diel δ 13 C res is 4.0, 5.4 and 14.8 ‰ in trunks, roots and leaves of different species and 12.5 and 8.1 ‰ at the soil and ecosystem scale in different biomes. Temporal variation in post-photosynthetic isotope fractionation related to changes in carbon allocation to different metabolic pathways is the most plausible mechanistic explanation for observed diel dynamics in δ 13 C res . In addition, mixing of component fluxes with different temporal dynamics and isotopic compositions add to the δ 13 C res variation on the soil and ecosystem level. Understanding short-term variations in δ 13 C res is particularly important for ecosystem studies, since δ 13 C res contains information on the fate of respiratory substrates, and may, therefore, provide a non-intrusive way to identify changes in carbon allocation patterns.

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“…In order to obtain the cumulative excess 13 C F until the end of the 1-month measurement period, gaps in excess 13 C F were linearly interpolated, excess 13 C F aggregated to hourly values and finally summed up. The first 8 h after labeling were excluded from the cumulative consideration as they were strongly influenced by physical back diffusion of the tracer signal out of the soil (Barthel et al, 2011b). Thus, the results for the biological 13 C flux might be slightly underestimated by the exclusion of the first 8 h after pulse labeling.…”

Section: Calculation Of 13 C Excess In Above-and Belowground Biomass mentioning

confidence: 99%

“…Control and treatment plots were labeled in parallel, in order to guarantee pulse labeling of one experimental block under identical environmental conditions. CO 2 concentrations as well as the isotopic composition of the air inside the labeling chambers were monitored by two infrared gas analyzers (Li840 and Li6262; Li-Cor Biosciences Inc., Lincoln, NE, USA) that had previously been tested for their 13 CO 2 sensitivities (Barthel et al, 2011b). As conditions inside only one labeling chamber could be monitored at a time, we regularly switched between the two labeling chambers (one labeling a control plot, the other labeling a treatment plot).…”

Section: Co 2 Pulse Labelingmentioning

confidence: 99%

The impact of extreme summer drought on the short-term carbon coupling of photosynthesis to soil CO2 efflux in a temperate grassland

et al. 2014

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Abstract. Along with predicted climate change, increased risks for summer drought are projected for Central Europe. However, large knowledge gaps exist in terms of how drought events influence the short-term ecosystem carbon cycle. Here, we present results from 13 CO 2 pulse labeling experiments at an intensively managed lowland grassland in Switzerland. We investigated the effect of extreme summer drought on the short-term coupling of freshly assimilated photosynthates in shoots to roots as well as to soil CO 2 efflux.Summer drought was simulated using rainout shelters during two field seasons (2010 and 2011). Soil CO 2 efflux and its isotopic composition were measured with custombuilt chambers coupled to a quantum cascade laser spectrometer (QCLAS-ISO, Aerodyne Research Inc., MA, USA). During the 90 min pulse labeling experiments, we added 99.9 atom % 13 CO 2 to the grass sward. In addition to the isotopic analysis of soil CO 2 efflux, this label was traced over 31 days into bulk shoots, roots and soil.Drought reduced the incorporation of recently fixed carbon into the shoots, but increased the relative allocation of fresh assimilates below ground compared to the control grasslands. Contrary to our hypothesis, we did not find a change of allocation speed in response to drought. Although drought clearly reduced soil CO 2 efflux rates, about 75 % of total tracer uptake in control plots was lost via soil CO 2 efflux during 19 days after pulse labeling, compared to only about 60 % under drought conditions. Thus, the short-term coupling of above-and below-ground processes was reduced in response to summer drought. The occurrence of a natural spring drought in 2011 lead to comparable albeit weaker drought responses increasing the confidence in the generalizability of our findings.

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Soil matrix tracer contamination and canopy recycling did not impair¹³CO₂plant–soil pulse labelling experiments

Cited by 10 publications

References 17 publications

The diel imprint of leaf metabolism on the δ¹³C signal of soil respiration under control and drought conditions

The diel imprint of leaf metabolism on the δ¹³C signal of soil respiration under control and drought conditions

Diel variations in the carbon isotope composition of respired CO<sub>2</sub> and associated carbon sources: a review of dynamics and mechanisms

The impact of extreme summer drought on the short-term carbon coupling of photosynthesis to soil CO<sub>2</sub> efflux in a temperate grassland

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Soil matrix tracer contamination and canopy recycling did not impair13CO2plant–soil pulse labelling experiments

Cited by 10 publications

References 17 publications

The diel imprint of leaf metabolism on the δ13C signal of soil respiration under control and drought conditions

The diel imprint of leaf metabolism on the δ13C signal of soil respiration under control and drought conditions

Diel variations in the carbon isotope composition of respired CO&lt;sub&gt;2&lt;/sub&gt; and associated carbon sources: a review of dynamics and mechanisms

The impact of extreme summer drought on the short-term carbon coupling of photosynthesis to soil CO&lt;sub&gt;2&lt;/sub&gt; efflux in a temperate grassland

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Soil matrix tracer contamination and canopy recycling did not impair¹³CO₂plant–soil pulse labelling experiments

The diel imprint of leaf metabolism on the δ¹³C signal of soil respiration under control and drought conditions

The diel imprint of leaf metabolism on the δ¹³C signal of soil respiration under control and drought conditions

Diel variations in the carbon isotope composition of respired CO<sub>2</sub> and associated carbon sources: a review of dynamics and mechanisms

The impact of extreme summer drought on the short-term carbon coupling of photosynthesis to soil CO<sub>2</sub> efflux in a temperate grassland