Ecological Archives E093-016-A5

Fernando Alfredo Lattanzi, German Darío Berone, Wolfgang Feneis, and Hans Schnyder. 2012. 13C-labeling shows the effect of hierarchy on the carbon gain of individuals and functional groups in dense field stands. Ecology 93:169–179.

Appendix E. A model to assess the role of tracer residence in shoot metabolic pools, tracer partitioning belowground, and tracer use in shoot respiration in determining the fraction of assimilated tracer lost from the shoot (flost) during steady state labeling.

Fig. E1. The model consisted of a pool that received assimilated carbon, that is, 13C-tracer, and from which carbon was used for shoot growth or lost via shoot respiration or allocation belowground. Thus, assimilation = allocation belowground + shoot respiration + shoot growth. Assimilation and pool size (Q) were assumed constant, and growth, partitioning and respiration were assumed linearly related to Q (first-order kinetics). Thus, assimilation = Q/τ · A + Q/τ · B + Q/τ · C, where τ is the mean residence time of carbon in Q, and A, B, and C are the proportion of carbon partitioned belowground, to shoot respiration, and to shoot growth, so that A + B + C = 1. B and C depend on carbon use efficiency for shoot growth (CUE): B = (1 – A) · CUE, C = (1 – A) · (1 – CUE). The model was implemented in ModelMaker (Cherwell Scientific, Oxford, UK) and flost estimated for any time t as the sum of tracer partitioned to shoot respiration and belowground from time 0 to time t, divided by the total amount of assimilated tracer. flost is independent of assimilation rate, thus the model was run with a nominal assimilation rate = 1.

Fig. E2. Results of simulation of flost for different combinations of (b) the mean residence time (τ) of carbon in a pool Q; (c) the proportion of carbon partitioned belowground, A,; and (c) the carbon use efficiency for shoot growth, CUE. Values of τ, CUE and A were taken from Amthor (2000), Belanger, Gastal and Warembourg (1992; 1994), Cannel and Thornley (2000), Gifford (2003), Lehmeier et al. (2008), Minchin, Thorpe and Farrar (1994), and Parsons and Robson (1982).

Literature Cited

Amthor J.S. 2000. The McCree-de Wit-Penning de Vries-Thornley respiration paradigms: 30 years later. Annals of Botany, 86:1–20.

Belanger G., F. Gastal, and F.R. Warembourg. 1992. The effects of nitrogen fertilization and the growing season on carbon partitioning in a sward of fall fescue (Festuca arundinacea Schreb). Annals of Botany, 70:239–244.

Belanger G., F. Gastal, and F.R. Warembourg. 1994. Carbon balance of tall fescue (Festuca arundinacea Schreb): Effects of nitrogen fertilization and the growing season. Annals of Botany, 74:653–659.

Cannell M.G.R and J.H.M. Thornley. 2000. Modelling components of plant respiration: some guiding principles. Annals of Botany, 85:45–54.

Gifford R.M. 2003. Plant respiration in productivity models: conceptualisation representation and issues for global terrestrial carbon-cycle research. Functional Plant Biology, 30:171–186.

Lehmeier C. A., F. A. Lattanzi, R. Schäufele, M. Wild, and H. Schnyder. 2008. Root and shoot respiration of perennial ryegrass are supplied by the same substrate pools: Assessment by dynamic 13C labeling and compartmental analysis of tracer kinetics. Plant Physiology, 148:1148–1158.

Minchin P.E.H., M.R. Thorpe, and J.F. Farrar. 1994. Short-term control of shoot:root partitioning. Journal of Experimental Botany, 45:615–622.

Parsons A.J. and M.J. 1982. Seasonal Changes in the Physiology of S24 Perennial Ryegrass (Lolium perenne L). 4. Comparison of the Carbon Balance of the Reproductive Crop in Spring and the Vegetative Crop in Autumn. Annals of Botany, 50:167–177.

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