Tracing Carbon Fluxes: Resolving Complexity Using Isotopes

Schnyder, H.; Ostler, Ulrike; Lehmeier, C.; Wild, Melanie; Morvan‐Bertrand, Annette; Schäufele, Rudi; Lattanzi, Fernando A.

doi:10.1007/978-3-642-30645-7_7

Cited by 7 publications

(7 citation statements)

References 86 publications

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“…Since respiration rates decreased less compared with the decline in the allocation of fresh assimilates, respiratory substrate supply might have been balanced by an increased contribution of storage pools (Lehmeier et al ., 2010; Hopkins et al ., 2013; Lynch et al ., 2013). This assumption is confirmed by the ratio between the MRT of root respiratory substrate (as reflected by tracer dynamics in root respired CO 2 ; Schnyder et al ., 2012) and the MRT of root sucrose (which is assumed to act as a major precursor of respiratory substrate in roots; Ghashghaie et al ., 2003). In control plots, the MRT of the root respiratory substrate was higher than the MRT of root sucrose alone by a factor of 1.6 (Table 1).…”

Section: Discussionmentioning

confidence: 99%

Summer drought alters carbon allocation to roots and root respiration in mountain grassland

et al. 2014

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Drought affects the carbon (C) source and sink activities of plant organs, with potential consequences for belowground C allocation, a key process of the terrestrial C cycle. The responses of belowground C allocation dynamics to drought are so far poorly understood.We combined experimental rain exclusion with 13C pulse labelling in a mountain meadow to analyse the effects of summer drought on the dynamics of belowground allocation of recently assimilated C and how it is partitioned among different carbohydrate pools and root respiration.Severe soil moisture deficit decreased the ecosystem C uptake and the amounts and velocity of C allocated from shoots to roots. However, the proportion of recently assimilated C translocated belowground remained unaffected by drought. Reduced root respiration, reflecting reduced C demand under drought, was increasingly sustained by C reserves, whilst recent assimilates were preferentially allocated to root storage and an enlarged pool of osmotically active compounds.Our results indicate that under drought conditions the usage of recent photosynthates is shifted from metabolic activity to osmotic adjustment and storage compounds.

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Section: Discussionmentioning

confidence: 99%

Summer drought alters carbon allocation to roots and root respiration in mountain grassland

et al. 2014

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“…The time course of tracer appearance in respired CO 2 was analysed by a two‐pool compartmental model (Schnyder et al . ) and provided estimates of the sizes and half‐life of pools composing the substrate supply system of respiration, and the contribution of individual pools to respiration. The model considered a transport and metabolic pool (Q1) – which was fed by current photosynthesis and supplied substrate to the centres of respiration – and a storage pool (Q2), which exchanged substrate with Q1.…”

Section: Methodsmentioning

confidence: 99%

Atmospheric CO₂ mole fraction affects stand‐scale carbon use efficiency of sunflower by stimulating respiration in light

Gong

Schäufele

Lehmeier

et al. 2017

Plant Cell & Environment

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Plant carbon-use-efficiency (CUE), a key parameter in carbon cycle and plant growth models, quantifies the fraction of fixed carbon that is converted into net primary production rather than respired. CUE has not been directly measured, partly because of the difficulty of measuring respiration in light. Here, we explore if CUE is affected by atmospheric CO . Sunflower stands were grown at low (200 μmol mol ) or high CO (1000 μmol mol ) in controlled environment mesocosms. CUE of stands was measured by dynamic stand-scale C labelling and partitioning of photosynthesis and respiration. At the same plant age, growth at high CO (compared with low CO ) led to 91% higher rates of apparent photosynthesis, 97% higher respiration in the dark, yet 143% higher respiration in light. Thus, CUE was significantly lower at high (0.65) than at low CO (0.71). Compartmental analysis of isotopic tracer kinetics demonstrated a greater commitment of carbon reserves in stand-scale respiratory metabolism at high CO . Two main processes contributed to the reduction of CUE at high CO : a reduced inhibition of leaf respiration by light and a diminished leaf mass ratio. This work highlights the relevance of measuring respiration in light and assessment of the CUE response to environment conditions.

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“…A decision on which layout of pools likely is valid cannot be made on statistical criteria due to the statistically similar performance of different layouts. It must be based on the physiological properties of the system [38] . We will show that independent outputs are the most likely interpretation in our case.…”

Section: Methodsmentioning

confidence: 99%

Forward Modeling of Fluctuating Dietary 13C Signals to Validate 13C Turnover Models of Milk and Milk Components from a Diet-Switch Experiment

et al. 2013

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Isotopic variation of food stuffs propagates through trophic systems. But, this variation is dampened in each trophic step, due to buffering effects of metabolic and storage pools. Thus, understanding of isotopic variation in trophic systems requires knowledge of isotopic turnover. In animals, turnover is usually quantified in diet-switch experiments in controlled conditions. Such experiments usually involve changes in diet chemical composition, which may affect turnover. Furthermore, it is uncertain if diet-switch based turnover models are applicable under conditions with randomly fluctuating dietary input signals. Here, we investigate if turnover information derived from diet-switch experiments with dairy cows can predict the isotopic composition of metabolic products (milk, milk components and feces) under natural fluctuations of dietary isotope and chemical composition. First, a diet-switch from a C3-grass/maize diet to a pure C3-grass diet was used to quantify carbon turnover in whole milk, lactose, casein, milk fat and feces. Data were analyzed with a compartmental mixed effects model, which allowed for multiple pools and intra-population variability, and included a delay between feed ingestion and first tracer appearance in outputs. The delay for milk components and whole milk was ∼12 h, and that of feces ∼20 h. The half-life (t½) for carbon in the feces was 9 h, while lactose, casein and milk fat had a t½ of 10, 18 and 19 h. The 13C kinetics of whole milk revealed two pools, a fast pool with a t½ of 10 h (likely representing lactose), and a slower pool with a t½ of 21 h (likely including casein and milk fat). The diet-switch based turnover information provided a precise prediction (RMSE ∼0.2 ‰) of the natural 13C fluctuations in outputs during a 30 days-long period when cows ingested a pure C3 grass with naturally fluctuating isotope composition.

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Tracing Carbon Fluxes: Resolving Complexity Using Isotopes

Cited by 7 publications

References 86 publications

Summer drought alters carbon allocation to roots and root respiration in mountain grassland

Summer drought alters carbon allocation to roots and root respiration in mountain grassland

Atmospheric CO₂ mole fraction affects stand‐scale carbon use efficiency of sunflower by stimulating respiration in light

Forward Modeling of Fluctuating Dietary 13C Signals to Validate 13C Turnover Models of Milk and Milk Components from a Diet-Switch Experiment

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Tracing Carbon Fluxes: Resolving Complexity Using Isotopes

Cited by 7 publications

References 86 publications

Summer drought alters carbon allocation to roots and root respiration in mountain grassland

Summer drought alters carbon allocation to roots and root respiration in mountain grassland

Atmospheric CO2 mole fraction affects stand‐scale carbon use efficiency of sunflower by stimulating respiration in light

Forward Modeling of Fluctuating Dietary 13C Signals to Validate 13C Turnover Models of Milk and Milk Components from a Diet-Switch Experiment

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Atmospheric CO₂ mole fraction affects stand‐scale carbon use efficiency of sunflower by stimulating respiration in light