@article{fdi:010042604,
  title = {{G}radual enrichment of {N}-15 with humification of diets in a below-ground food web : relationship between {N}-15 and diet age determined using {C}-14},
  author = {{H}yodo, {F}. and {T}ayasu, {I}. and {K}onate, {S}. and {T}ondoh, {J}. {E}. and {L}avelle, {P}atrick and {W}ada, {E}.},
  editor = {},
  language = {{ENG}},
  abstract = {1. {S}table nitrogen ({N}) isotope has been widely used to disentangle food webs and to infer trophic positions of organisms based on an assumption that the stepwise enrichment occurs along trophic levels. {T}he enrichment of {N}-15 in soil organisms with diet humification has also been reported, but the underlying mechanism has not been fully examined. 2. {T}o examine the effect of diet humification on {N}-15, we estimated the stable {N} isotope ratios and diet ages of earthworms and termites. {T}hese organisms feed on organic matter with various degrees of humification, ranging from undecomposed plant materials to humified organic matter (soil organic matter), in a gallery forest and a savanna in the {I}vory {C}oast. {W}e defined diet age as the time elapsed since carbon ({C}) in the diet of earthworms and termites was fixed from atmospheric {CO}2 by photosynthesis; it was estimated by comparing the radiocarbon ({C}-14) content of these organisms to atmospheric ({CO}2)-{C}-14 records. 3. {S}table {N} isotope ratios increased along the humification gradient of diets, and values for earthworms and termites varied from 1.8 parts per thousand to 9.9 parts per thousand and from -1.5 parts per thousand to 15.9 parts per thousand, respectively. {E}pigeic (litter-feeding) earthworms had younger diet ages (2-4 years), whereas endogeic (soil-feeding) earthworms generally exhibited older diet ages (5-9 years). {G}rass-feeding termites had young diet ages (2 years), and wood/soil-feeding termites had the oldest diet ages (c. 50 years). {S}oil-feeding termites were similar in diet age (7-12 years) to wood feeders (8-11 years), with the exception of one species (18-21 years) that consumes large-diameter wood. 4. {A} significant positive relationship was found between diet ages and stable {N} isotope ratios of the two groups in the savanna. {T}his relationship held in the gallery forest when termites feeding on woody tissues were not considered. {T}hese results show that the stable {N} isotope ratios of organisms can increase with diet age, unless {C} in the diet has been stored as organic matter, such as woody tissue, that is able to age without being subject to humification processes. 5. {G}iven that above-ground food webs are often sustained directly by material and energy flow from below-ground food webs, in addition to trophic interactions, gradual enrichment of {N}-15 with the humification of below-ground diets should be considered when interpreting stable {N} isotope ratios of terrestrial food webs.},
  keywords = {earthworms ; radiocarbon ; stable nitrogen isotope ; termites},
  booktitle = {},
  journal = {{F}unctional {E}cology},
  volume = {22},
  numero = {3},
  pages = {516--522},
  ISSN = {0269-8463},
  year = {2008},
  DOI = {10.1111/j.1365-2435.2008.01386.x},
  URL = {https://www.documentation.ird.fr/hor/fdi:010042604},
}