@article{fdi:010053417,
  title = {{O}rganic matter stabilization in soil aggregates : understanding the biogeochemical mechanisms that determine the fate of carbon inputs in soils},
  author = {{V}erchot, {L}. {V}. and {D}utaur, {L}. and {S}hepherd, {K}. {D}. and {A}lbrecht, {A}lain},
  editor = {},
  language = {{ENG}},
  abstract = {{W}e studied the biochemical and biophysical processes of carbon sequestration in an intensive agroforestry system on two soils ({F}eralsol - {L}uero; {A}renosol - {T}eso) in {W}. {K}enya to elucidate the mechanisms associated with long-term carbon storage. {S}pecifically, we looked at a top-down model (macro-aggregates form around organic matter particles and micro-aggregates form within the macro-aggregates) and a bottom-up model (micro-aggregates form independently and are incorporated into macro-aggregates) of soil aggregate formation. {S}oil samples were collected from experiments on improved tree fallows using different species and two tillage treatments; water-stable aggregates were extracted and sorted into three size classes: macro-aggregates (>212 mu m), meso-aggregates (53-212 mu m) and micro-aggregates (20-53 mu m). {O}rganic matter characterization of each fraction was based on {C}-13 isotope abundance, {F}ourier transform infrared ({FTIR}) spectroscopy and the abundance of polysaccharides. {I}mproved fallows increased soil {C} by 0.28 and 0.26 kg m(-2) in the top 20 cm of the soil profile in {L}uero and {T}eso, respectively. {T}illage altered the distribution of aggregates among size classes. {C}hanges in the delta {C}-13 signature in each fraction indicated that more of the new carbon was found in the macro-aggregates (35-70%) and mesa-aggregates (18-49%) in {L}uero and less (9-17%) was found in the micro-aggregates. {I}n {T}eso, about 40-80% of the new aggregate {C} was found in the mesa-aggregates. 14-45% was found in the micro-aggregates and only 4-26% was found in the macro-aggregates. {T}he mesoaggregates and macro-aggregates to a lesser extent, in both sites, were enriched in carboxylic-{C} and aromatic-{C}, indicating the importance of {OM} decomposition and plant-derived {C} in the stabilization of larger aggregates, supporting the top-down model of aggregate formation. {M}icrobially derived polysaccharides play a leading role in the formation of stable micro-aggregates and carboxylic-{C} promotes stabilization through surface occlusion. {T}his bottom-up process is essential to promote long-term carbon sequestration in soils. {A}dditionally, the micro-aggregates at both sites were enriched in polysaccharides and had elevated ratios of galactose + mannose:arabinose + xylose than the other aggregate fractions, indicating the importance of microbial processes in the formation of stable micro-aggregates and supporting the bottom-up model.},
  keywords = {{C}arbon sequestration ; {C}arbohydrates ; {C}-13 ; {FTIR} ; {A}ggregates ; {I}mproved ; fallow},
  booktitle = {},
  journal = {{G}eoderma},
  volume = {161},
  numero = {3-4},
  pages = {182--193},
  ISSN = {0016-7061},
  year = {2011},
  DOI = {10.1016/j.geoderma.2010.12.017},
  URL = {https://www.documentation.ird.fr/hor/fdi:010053417},
}