Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 5 1 2008 10.5194/bg-5-123-2008 http://www.biogeosciences.net/5/123/2008/ http://www.biogeosciences.net/5/123/2008/bg-5-123-2008.html http://www.biogeosciences.net/5/123/2008/bg-5-123-2008.pdf 123 128 2008-02-01 Relative stability of soil carbon revealed by shifts in δ¹⁵N and C:N ratio F. Conen franz.conen@unibas.ch M. Zimmermann J. Leifeld B. Seth C. Alewell Institute of Environmental Geosciences, University of Basel, Bernoullistr. 30, 4056 Basel, Switzerland School of Geosciences, University of Edinburgh, Drummond Street, EH8 9XP Edinburgh, UK Research Station ART, Reckenholzstr. 191, 8046 Zürich, Switzerland Life on earth drives a continuous exchange of carbon between soils and the atmosphere. Some forms of soil carbon, or organic matter, are more stable and have a longer residence time in soil than others. Relative differences in stability have often been derived from shifts in δ¹³C (which is bound to a vegetation change from C3 to C4 type) or through ¹⁴C-dating (which is bound to small sample numbers because of high measurement costs). Here, we propose a new concept based on the increase in δ¹⁵N and the decrease in C:N ratio with increasing stability. We tested the concept on grasslands at different elevations in the Swiss Alps. Depending on elevation and soil depth, it predicted mineral-associated organic carbon to be 3 to 73 times more stable than particulate organic carbon. Analysis of ¹⁴C-ages generally endorsed these predictions. Amundson, R., Austin, A. T., Schuur, E. A. G., Yoo, K., Matzek, V., Kendall, C., Uebersax, A., Brenner, D., and Baisden, W.T.: Global patterns of the isotopic composition of soil and plant nitrogen, Global Biogeochem. Cy., 17, 1031, doi:10.1029/2002GB001903, 2003. Baisden, W. T., R., Amundson, A., Cook, C., and Brenner, D. L.: Turnover and storage of C and N in five density fractions from California annual grassland surface soils, Global Biogeochem. Cy., 16, 1117, doi:10.1029/2001GB001822, 2002a. Baisden, W. T., Amundson, R., Brenner, D. L., Cook, A. C., Kendall, C., and Harden, J. W.: A multiisotope C and N modeling analysis of soil organic matter turnover and transport as a function of soil depth in a California annual grassland soil chronosequence, Global Biogeochem. Cy., 16, 1135, doi:10.1029/2001GB001823, 2002b. Balesdent, J., Mariotti, A., and Guillet B.: Natural C-13 abundance as a tracer for studies of soil organic-matter dynamics, Soil Biol. Biochem., 19, 25–30, 1987. Batjes, N. H.: Total carbon and nitrogen in the soils of the world, European J. Soil Sci., 47, 151–163, 1996. Davidson, E. A. and Janssens, I. A.: Temperature sensitivity of soil carbon decomposition and feedbacks to climate change, Nature, 440, 165–173, 2006. Dijkstra, P., Menyailo, O. V., Doucett, R. R., Hart, S. C., Schwartz, E., and Hungate, B. A.: C and N availability affects the N-15 natural abundance of the soil microbial biomass across a cattle manure gradient, Eur. J. Soil Sci., 57, 468–475, 2006. Egli, M., Mirabella, A., Sartori, G., Zanelli, R., and Bischof, S.: Effect of north and south exposure on weathering rates and clay mineral formation in Alpine soils, Catena, 67, 155–174, 2006. Falloon, P., Jones, C.D., Cerri, C.E., Al-Adamat, R., Kamoni, P., Bhattacharyya, T., Easter, M., Paustian, K., Killian, K., Coleman, K., and Milne, E.: Climate change and its impact on soil and vegetation carbon storage in Kenya, Jordan, India and Brazil, Agriculture, Ecosystems & Environment, 122, 114–124, 2007. Gleixner, G., Poirier, N., Bol, R., and Balesdent, J.: Molecular dynamics of organic matter in a cultivated soil, Org. Geochem., 33, 357–366, 2002. Harkness, D. D., Harrison, A. F., and Bacon, P. J.: The temporal distribution of `bomb' $^14$C in a forest soil, Radiocarbon, 28, 328–337, 1986. Högberg, P.: $^15$N natural abundance in soil-plant systems, New Phytol., 137, 179–203, 1997. Jones, C., McConnell, C., Coleman, K., Cox, P., Falloon, P., Jenkinson, D., and Powlson D.: Global climate change and soil carbon stocks; predictions from two contrasting models for the turnover of organic carbon in soil, Global Change Biol., 11, 154–166, 2005. Knorr, W., Prentice, I. C., House, J. I., and Holland, E. A.: Long-term sensitivity of soil carbon turnover to warming, Nature, 433, 298–301, 2005. Kramer, M. G., Sollins, P., Sletten, R. S., and Swart, P. K.: N isotope fractionation and measures of organic matter alteration during decomposition, Ecology, 84, 2021–2025, 2003. Krull, E. S., Baldock, J. A., and Skjemstad, J. O.: Importance of Mechanisms and Processes of the Stabilisation of Soil Organic Matter for Modelling Carbon Turnover, Funct. Plant Biol., 30, 207–222, 2003. Levin, I., Kromer, B., Schoch-Fischer, H., Bruns, M., Münnich, M., Berdau,D., Vogel, J. C., and Münnich, K. O.: $\delta ^14$CO₂ record from Vermunt, in: Trends, A Compendium of Data on Global Change, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., USA, 1994. Levin, I. and Kromer, B: $\delta ^14$CO₂ records from Schauinsland, in: Trends, A Compendium of Data on Global Change, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., USA, 1997. Liao, J. D., Boutton, T. W., and Jastrow, J. D.: Organic matter turnover in soil physical fractions following woody plant invasion of grassland: Evidence from natural $^13$C and $^15$N, Soil Biol. Biochem., 38, 3197–3210, 2006. Mariotti, A., Pierre, D., Vedy, J. C., Bruckert, S., and Guillemot, J.: The abundancee of natural nitrogen 15 in the organic matter of soils along an altitudinal gradiant, Catena, 7, 293–300, 1980. Nannipieri, P., Ascher, J., Ceccherini, M. T., Landi, L., Pietramellara, G., and Renella, G.: Microbial diversity and soil functions, Eur. J. Soil Sci., 54, 655–670, 2003. Robinson, D.: $\delta^15$N as an integrator of the nitrogen cycle, Trends Ecol. Evol., 16, 153–162, 2001. Snider, M. J., Reinhardt, L., Wolfenden, R., and Cleland, W. W.: N-15 kinetic isotope effects on uncatalyzed and enzymatic deamination of cytine mark, Biochemistry, 41, 415–421, 2002. Stuiver, M., Reimer, P. J., and Braziunas, T. F.: High-precision radiocarbon age calibration for terrestrial and marine samples, Radiocarbon, 40, 1127–1151, 1998. Trumbore, S. E.: Comparison of carbon dynamics in tropical and temperate soils using radiocarbon measurements, Global Biogeochem. Cy., 7, 275–290, 1993. Trumbore, S. E., Bonani, G., and Woelfli, W.: The rates of carbon cycling in several soils from AMS C14 measurements of fractioned soil organic matter, in: Soils and the Greenhouse Effect, edited by: Bouwman, A. F., John Wiley & Sons, 407–414, 1990. Vervaet, H., Boeckx, P., Unamuno, V., Van Cleemput, O., and Hofman, G.: Can $\delta ^15$N profiles in forest soils predict NO$_3^-$ loss and net N mineralization rates?, Biol. Fertil. Soils, 36, 143–150, 2002. v.Lützow, M., Kögel-Knabner, I., Ekschmitt, K., Matzner, E., Guggenberger, G., Marschner, B., and Flessa H.: Stabilization of organic matter in temperate soils: mechanisms and their relevance under different soil conditions – a review, Eur. J. Soil Sci., 57, 426–445, 2006. Zimmermann, M., Leifeld, J., Schmidt, M.W.I., Smith, P., and Fuhrer, J.: Measured soil organic matter fractions can be related to pools in the RothC model, Eur. J. Soil Sci., 58, 658–667, 2007.