This is the peer reviewed version of the following article: Heinemeyer, A. and Bene, C. Di and Lloyd, A.R. and Tortorella, D. and Baxter, R. and Huntley, B. and Gelsomino, A. and Ineson, P. (2011) 'Soil respiration : implications of the plant-soil continuum and respiration chamber collar-insertion depth on measurement and modelling of soil CO2 e ux rates in three ecosystems.', European journal of soil science., 62 (1). pp. 82-94, which has been published in nal form at http://dx.doi.org/10.1111/j.1365-2389.2010.01331.x. This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. fluxes. We hypothesized that total soil respiration is frequently under-estimated because soil 30 collar insertions sever surface roots, which coupled to the preferential practice of taking 31 daytime measurements, lead to the autotrophic (root-derived) component frequently being 32 missed. We measured root distribution and soil CO 2 efflux in three contrasting ecosystems: a 33Lodgepole pine (Pinus contorta) plantation, an upland heather-dominated peatland and a 34 lowland sheep-grazed grassland, where we combined shallow surface collars with collars at 35 different soil insertion depths for occasional and continuous hourly flux measurements. Collar 36 insertion by only a few centimetres reduced total soil CO 2 efflux in all three ecosystems by an 37 average of 15% but at times up to 30 to 50%, and was directly proportional to the quantity of 38 cut fine roots. Most reduction occurred in the shallow-rooted peatland system and least in the 39 deep-rooted grassland. In the forest and grassland, soil temperatures explained most of the 40 deep collar (i.e. largely heterotrophic) variation and did not relate to the root-derived (i.e.

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We deployed an automated multiplexed soil‐respiration (SR) system to monitor partitioned soil CO2 component fluxes (from roots, mycorrhizal hyphae and heterotrophs) in a UK grassland using a combination of shallow surface (total SR flux), deep (excluding roots and mycorrhizal fungi) and 20‐µm pore mesh window soil collars (excluding roots only). Soil CO2 efflux was monitored during a 3‐month period during summer. Repeated cutting of mycorrhizal connections in some of the mycorrhizal treatments enabled assessment of subsequent recovery of mycorrhizal fluxes and a comparison with deep collar fluxes. After soil collar insertion, fluxes in the deep collars were significantly reduced, by approximately 40%. Whereas fluxes in the uncut, mycorrhizal collar treatments remained close to those from the surface collar, cut mycorrhizal treatments showed an immediate reduction after cutting to values close to those from the deep collar with a subsequent recovery of around 4 weeks. Overall, the autotrophic root and mycorrhizal flux was relatively stable throughout. Whereas root fluxes contributed about 10–30% of the total flux during the initial larger flux period, this declined and there was an increased mycorrhizal contribution during the latter part of the measurement period. Moreover, SR flux components differed in their response to key climatic factors, with root fluxes responding equally to temperature and light. Importantly, whereas the heterotrophic flux component responded strongly to temperature and soil moisture, the mycorrhizal component responded much less to those factors, but more to light. We also investigated treatment impacts over time on soil biochemical variables such as microbial biomass C, extractable C, microbial quotient and metabolic quotient, and bacterial community structure, and discussed these in relation to measured SR fluxes and the partitioning technique.

A synthetic, water-soluble iron-porphyrin [meso-tetra(2,6-dichloro-3-sulfonatophenyl) porphyrinate of Fe(III) chloride] has recently been proposed as a biomimetic catalyst in the process of oxidative polymerization of terrestrial humic acids, to increase their conformational stability and thus contribute to a reduction of soil CO 2 release into the atmosphere. This study was aimed at investigating changes in selected soil chemical properties, CO 2 efflux, and maize root morphotopology after the addition of iron-porphyrin as a microcosm-style experiment, located in a greenhouse. The addition of mature compost was also included as an experimental factor in order to reveal synergistic effects in regard to freshly added organic materials. Iron-porphyrin determined a negligible effect on soil organic budget in both unplanted and planted microcosms. Conversely, the biomimetic catalyst was found to have significant and contrasting effects on soil respiration, apparently reflecting different iron porphyrin-plant-compost interactions. Consequently, iron-porphyrin significantly reduced CO 2 efflux from the bare (unplanted) soil, which was, conversely, stimulated in maize-planted microcosms. Additionally, combined iron-porphyrin and compost addition synergistically acted in increasing soil respiration in planted microcosms. Moreover, root biomass was increased with the addition of iron-porphyrin, and a further effect on maize root morphology was noted when used in combination with compost; notably the length of coarse and fine roots increased. We hypothesized that the efficacy of iron-porphyrin in reducing CO 2 efflux from soil may be mediated by morphological changes in the plant-root system.