Spatial heterogeneity in the relocation of added 13C within the structure of an upland grassland soil

• Published in: Soil biology & biochemistry Vol. 38; no. 2; pp. 229 - 234
• Main Authors: Grieve, Ian C., Davidson, Donald A., Ostle, Nicholas J., Bruneau, Patricia M.C., Fallick, Anthony E.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 2006; New York, NY Elsevier Science
• Subjects: Agronomy. Soil science and plant productions; Biochemistry and biology; biodiversity; Biological and medical sciences; Carbon cycling; carbon dioxide; carbon sequestration; chemical constituents of plants; Chemical, physicochemical, biochemical and biological properties; Fundamental and applied biological sciences. Psychology; grassland soils; isotope labeling; Physics, chemistry, biochemistry and biology of agricultural and forest soils; roots; Soil aggregates; Soil fauna; soil horizons; soil nutrient dynamics; soil organic matter; Soil science; Spatial variability; spatial variation; Stable carbon isotope; stable isotopes; upland soils; Zoology (interactions between soil fauna and agricultural or forest soils); Scotland; Soil fauna; Spatial variability; Stable carbon isotope; Carbon cycling; Soil aggregates; Upland area; Carbon Isotopes; Carbon cycle; Upland soils; Soil science; Aggregate; Isotopes; Grassland soil
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2005.04.035

A pulse of
13CO
2 was added to the above ground vegetation in an upland grassland to determine the effects of faunal diversity on the flux of carbon to the surface horizons of the soil. Faunal diversity was manipulated by liming and biocide treatments for three years prior to the pulse addition. The relocation of
13C within roots and rhizosphere soil was determined by analysis of samples of bulk soil and of specific features identified on soil thin sections on four dates after the addition of the
13CO
2 pulse. Analysis of bulk soils showed only a small enrichment in
13C and no significant effects of the treatments. Analysis by isotope ratio mass spectrometry of the products of in situ laser combustion of root material and aggregates formed from faunal excrement showed that the distribution of the newly photosynthesised
13C is very localised, with large spatial variability in soil and root
δ
13C at scales of less than 1
mm.
δ
13C values ranged from the natural abundance level of around −28‰ to −4.9‰ in roots and to −8.4‰ in aggregates. The small pulse and large spatial variability masked any effects of the liming and biocide treatments in these soils. However, the variability in the relocation of newly photosynthesised carbon may help to explain the large spatial variability found in bacterial numbers at the sub-mm scale within soils and emphasises the importance of the accessibility of substrates to decomposers in undisturbed structured soils.