Monday, July 08, 2013
Roots: More action down below explains deep soil carbon
Roots are more important than surface biota in creating soil carbon, according to Schmidt et. al's peer-reviewed paper Persistence of soil organic matter as an ecosystem property (eScholarship, 26-9-2012). "Root-derived carbon is retained in soils much more efficiently than are
above-ground inputs of leaves and needles40–42." Isotopic analyses and
comparisons of root and shoot biomarkers confirm the dominance of
root-derived molecular structures in soil43 and of root-derived carbon
in soil microorganisms44. Preferential retention of root-derived carbon
has been observed in temperate forests45,46, for example, where belowground
inputs, including fungal mycelia, make up a bigger fraction of
new carbon in SOM than do leaf litter inputs44,47. In addition to many
above-ground inputs being mineralized in the litter layer, root and
mycorrhizal inputs have more opportunity for physico-chemical interactions
with soil particles40. At the same time, fresh root inputs may
‘prime’ microbial activity, leading to faster decomposition of older
organic matter48,49 as well as changing community composition50.
Carbon allocation by plants thus plays an important part in soil carbon
dynamics, but it is not known how future changes in plant allocation
will affect soil carbon stocks51."
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inferred from maize cultivated soils. Soil Biol. Biochem. 28, 1261–1263 (1996).
43. Mendez-Millan, M., Dignac, M. F., Rumpel, C., Rasse, D. P. & Derenne, S. Molecular
dynamics of shoot vs. root biomarkers in an agricultural soil estimated by natural
abundance 13C labelling. Soil Biol. Biochem. 42, 169–177 (2010).
44. Kramer, C. et al. Recent (4 year old) leaf litter is not a major source of microbial
carbon in a temperate forest mineral soil. Soil Biol. Biochem. 42, 1028–1037
45. Bird, J. A., Kleber, M.&Torn, M. S. 13Cand15Nstabilizationdynamics in soil organic
matter fractions during needle and fine root decomposition. Org. Geochem. 39,
46. Bird, J. A. & Torn, M. S. Fine roots vs. needles: A comparison of 13C and 15N
dynamics in a ponderosa pine forest soil. Biogeochemistry 79, 361–382 (2006).
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input into soil organic matter. Plant Soil 281, 15–24 (2006).
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carbon supply. Nature 450, 277–280 (2007).
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deposition. Nature Geosci. 3, 315–322 (2010).
52. Chabbi, A., Kogel-Knabner, I. & Rumpel, C. Stabilised carbon in subsoil horizons is
located in spatially distinct parts of the soil profile. Soil Biol. Biochem. 41, 256–261
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understood component of terrestrial C cycle. Plant Soil 338, 143–158 (2011).
A comprehensive overview of key challenges to quantitative understanding of
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56. Kalbitz, K., Schwesig, D., Rethemeyer, J. & Matzner, E. Stabilization of dissolved
organic matter by sorption to the mineral soil. Soil Biol. Biochem. 37, 1319–1331
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soil archives of the Russian steppe. Glob. Change Biol. 8, 941–953 (2002).
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Posted by Michael Kiely at 10:36 PM