Biogeosciences Discuss., 10, 5671-5700, 2013
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This discussion paper has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG.
Mean age of carbon in fine roots from temperate forests and grasslands with different management
E. Solly1, I. Schöning1, S. Boch2, J. Müller3, S. A. Socher2, S. E. Trumbore1, and M. Schrumpf1
1Max-Planck Institute for Biogeochemistry, Jena, Germany
2Institute of Plant Sciences and Botanical Garden, University of Bern, Bern, Switzerland
3Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany

Abstract. Fine roots are the most dynamic portion of a plant's root system and a major source of soil organic matter. By altering plant species diversity and composition, soil conditions and nutrient availability, and consequently belowground allocation and dynamics of root carbon (C) inputs, land-use and management changes may influence organic C storage in terrestrial ecosystems. In three German regions we measured fine root radiocarbon (14C) content to estimate the mean time since C in root tissues was fixed from the atmosphere in 54 grassland and forest plots with different management and soil conditions. Although root biomass was on average greater in grasslands 5.1 ± 0.8 g (mean ± SE, n = 27) than in forests 3.1 ± 0.5 g (n = 27), the mean age of C in fine roots in forests averaged 11.3 ± 1.8 yr and was significantly older and more variable compared to grasslands 1.7 ± 0.4 yr. We further found that management affects the mean age of fine root C in temperate grasslands mediated by changes in plant species diversity and composition. Fine root mean C age is positively correlated to plant diversity (r = 0.65) and to the number of perennial species (r = 0.77). In temperate grasslands the mean age of fine root C is also influenced by the study region mainly driven by differences in soil characteristics and climate which reflect in plant composition variations, with averages of 0.7 ± 0.1 yr (n = 9) on mostly organic sandy soils in northern Germany and of 1.8 ± 0.3 yr (n = 9) and 2.6 ± 0.3 (n = 9) in more silty and clayey soils respectively in central and southern Germany. Our results indicate an internal redistribution of C in perennial species and suggest linkages between fine root C age and management in grasslands. These findings improve our ability to predict and model belowground C fluxes across broader spatial scales.

Citation: Solly, E., Schöning, I., Boch, S., Müller, J., Socher, S. A., Trumbore, S. E., and Schrumpf, M.: Mean age of carbon in fine roots from temperate forests and grasslands with different management, Biogeosciences Discuss., 10, 5671-5700, doi:10.5194/bgd-10-5671-2013, 2013.
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