Production and stable isotopic composition of CO&lt;sub&gt;2&lt;/sub&gt;
                        in a soil near Bern, Switzerland

Hesterberg, Rolf; Siegenthaler, U.

doi:10.3402/tellusb.v43i2.15264

Cited by 116 publications

(68 citation statements)

References 12 publications

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“…Time lags have been shown to increase for deeper soils (i.e. 6 months at -80 cm, Hesterberg and Siegenthaler 1991), while the extent of signal dampening (reduction of the annual amplitude) is dependent on total annual precipitation and soil properties (Hsieh et al 1998). We observe *60% of the d 18 O range of precipitation in soil water at -15 cm, which varies annually by an average ?3.8%.…”

Section: Discussionmentioning

confidence: 93%

Temperature versus species-specific influences on the stable oxygen isotope ratio of tree rings

Reynolds‐Henne

Saurer

Siegwolf

2009

Trees

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Stable isotopic ratios integrate ecosystem variability while reflecting change in both environmental and biological processes. At sites, where climate does not strongly limit tree growth, co-occurring trees may display large discrepancies in stable oxygen isotopic ratios (d 18 O) due to the interplay between biological processes (competition for light and nutrients, individual tree physiology, etc.) and climate. For a better quantification of the isotope variability within and among trees, the climatic and/or individual tree effects on seasonal d 18 O variations in precipitation, soil water, leaf water and leaf organic material (whole leaf, cellulose and starch) and annual d 18 O variations in tree-ring cellulose for Fagus sylvatica (Fs), Quercus robur (Qr), Carpinus betulus (Cb) and Pinus sylvestris (Ps) were studied in a mature temperate forest in Switzerland, using a mixed linear regression model technique. Furthermore, the influence of environmental factors on d 18 O was assessed by means of three common isotope fractionation models. Our statistical analysis showed that except for Ps, a greater portion of d 18 O variance in leaf compounds can be explained by individual tree effects, compared to temperature. Concerning tree-ring cellulose, only Fs and Ps show a significant temperature signal (maximum 12% of the variance explained), while the individual tree effect significantly explains d 18 O for all species for a period of 38 years. Large species differences resulted in a limited ability of the isotope fractionation models to predict measured values. Overall, we conclude that in a diverse mixed forest stand, individual tree responses reduce the potential extraction of a temperature signal from d 18 O.

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Section: Discussionmentioning

confidence: 93%

Temperature versus species-specific influences on the stable oxygen isotope ratio of tree rings

Reynolds‐Henne

Saurer

Siegwolf

2009

Trees

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“…In the untreated area, topsoil desiccation during dry periods (July-September) strongly reduced the soil CO 2 release and led to less negative δ 13 C values. Less negative δ 13 C of soil air under dry conditions can result from three effects: (1) a reduced discrimination of 13 C in leaves during photosynthesis (reduced stomatal conductance, see Farquhar et al 1989;Panek 1996); (2) an increase of the ratio of autotrophic (less 13 C depleted CO 2 , see above) to heterotrophic (micro-organism) respiration, because most microbial activity occurs in the top soil layer, which dries out first; and (3) an increased contribution of respired CO 2 from deeper and wetter soil layers, which are known to carry a less negative δ 13 C signal (Hesterberg and Siegenthaler 1991;Amundson et al 1998). Since high air (and leaf) temperature, high VPD and low soil moisture are mostly concurrent, the degree to which the isotopic ratio in soil CO 2 is impacted, by either plant or microbial activity remains uncertain (see Davidson et al 1998).…”

Section: Carbon Investment and Turnovermentioning

confidence: 98%

“…During this physical process the lighter 12 CO 2 molecules diffuse faster and therefore more 13 CO 2 molecules remain in the soil gas samples. This type of discrimination, described by Hesterberg and Siegenthaler (1991), and Amundson et al (1998) systematically biased our measured δ 13 C values. Therefore 4.4‰ was subtracted from all measured δ 13 C values.…”

Section: Soil Airmentioning

confidence: 99%

Carbon fluxes to the soil in a mature temperate forest assessed by 13C isotope tracing

et al. 2004

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Photosynthetic carbon uptake and respiratory C release from soil are major components of the global carbon balance. The use of 13C depleted CO2)(delta13C = -30 per thousand) in a free air CO2 enrichment experiment in a mature deciduous forest permitted us to trace the carbon transfer from tree crowns to the rhizosphere of 100-120 years old trees. During the first season of CO2 enrichment the CO2 released from soil originated substantially from concurrent assimilation. The small contribution of recent carbon in fine roots suggests a much slower fine root turnover than is often assumed. 13C abundance in soil air correlated best with temperature data taken from 4 to 10 days before air sampling time and is thus rapidly available for root and rhizosphere respiration. The spatial variability of delta13C in soil air showed relationships to above ground tree types such as conifers versus broad-leaved trees. Considering the complexity and strong overlap of roots from different individuals in a forest, this finding opens an exciting new possibility of associating respiration with different species. What might be seen as signal noise does in fact contain valuable information on the spatial heterogeneity of tree-soil interaction.

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“…The 18 O of CO 2 from both root respiration and soil decomposition is strongly influenced by the oxygen isotopic composition of the water with which it is in contact (Hesterberg and Siegenthaler 1991;Amundson et al 1998;Tans 1998;Stern et al 1999). CO 2 isotopically equilibrates with water according to:…”

Section: Isotopic Identity Of Different Ecosystem Gas Exchange Componmentioning

confidence: 98%

The use of stable isotopes to study ecosystem gas exchange

Yakir¹,

2000

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Stable isotopes are a powerful research tool in environmental sciences and their use in ecosystem research is increasing. In this review we introduce and discuss the relevant details underlying the use of carbon and oxygen isotopic compositions in ecosystem gas exchange research. The current use and potential developments of stable isotope measurements together with concentration and flux measurements of CO and water vapor are emphasized. For these applications it is critical to know the isotopic identity of specific ecosystem components such as the isotopic composition of CO, organic matter, liquid water, and water vapor, as well as the associated isotopic fractionations, in the soil-plant- atmosphere system. Combining stable isotopes and concentration measurements is very effective through the use of "Keeling plots." This approach allows the identification of the isotopic composition and the contribution of ecosystem, or ecosystem components, to the exchange fluxes with the atmosphere. It also allows the estimation of net ecosystem discrimination and soil disequilibrium effects. Recent modifications of the Keeling plot approach permit examination of CO recycling in ecosystems. Combining stable isotopes with dynamic flux measurements requires precision in isotopic sampling and analysis, which is currently at the limit of detection. Combined with the micrometeorological gradient approach (applicable mostly in grasslands and crop fields), stable isotope measurements allow separation of net CO exchange into photosynthetic and soil respiration components, and the evapotranspiration flux into soil evaporation and leaf transpiration. Similar applications in conjunction with eddy correlation techniques (applicable to forests, in addition to grasslands and crop fields) are more demanding, but can potentially be applied in combination with the Keeling plot relationship. The advance and potential in using stable isotope measurements should make their use a standard component in the limited arsenal of ecosystem-scale research tools.

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Production and stable isotopic composition of CO<sub>2</sub> in a soil near Bern, Switzerland

Cited by 116 publications

References 12 publications

Temperature versus species-specific influences on the stable oxygen isotope ratio of tree rings

Temperature versus species-specific influences on the stable oxygen isotope ratio of tree rings

Carbon fluxes to the soil in a mature temperate forest assessed by 13C isotope tracing

The use of stable isotopes to study ecosystem gas exchange

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