Data/hora: 04/06/2024 10:58:57

Biblioteca(s): | Embrapa Florestas.
Data corrente: | 06/10/2008
Data da última atualização: | 06/10/2008
Autoria: | HYODO, F.; TAYASU, I.; KONATÉ, S.; TONDOH, J. E.; LAVELLE, P.; WADA, E.
Título: | Gradual enrichment of 15N with humification of diets in a belowground food web: relationship between 15N and diet age determined using 14C.
Ano de publicação: | 2008
Fonte/Imprenta: | In: INTERNATIONAL COLLOQUIUM ON SOIL ZOOLOGY, 15; INTERNATIONAL COLLOQUIUM ON APTERYGOTA, 12., 2008, Curitiba. Biodiversity, conservation and sustainabele management of soil animal: abstracts. Colombo: Embrapa Florestas. Editors: George Gardner Brown; Klaus Dieter Sautter; Renato Marques; Amarildo Pasini. 1 CD-ROM.
Idioma: | Inglês

Conteúdo:

Stable nitrogen (N) isotope has been widely used to disentangle food web and to infer trophic
positions of organisms based on an assumption that the stepwise enrichment occurs along
trophic levels. The enrichment of 15N in soil organisms with diet humificaition has also been
reported , but the underlying mechanism has not been fully examined. To examine the effect of
diet humification on 15N, we estimated the stable N isotope ratios and diet ages of earthworms
and termites. These 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 savannah in the Ivory Coast. We defined diet age as the time elapsed
since carbon (C) in the diet of earthworms and termites was fixed from atmospheric CO2 by
photosynthesis; it was estimated by comparing the radiocarbon (14C) content of these organisms
to atmospheric 14CO2 records. Stable N isotope ratios increased along the humification
gradient of diets, and values for earthworms and termites varied from 1.8 to 9.9? and from ?
1.5 to 15.9?, respectively. Epigeic (litter-feeding) earthworms had younger diet ages (2?4 y),
whereas endogeic (soil-feeding) earthworms generally exhibited older diet ages (5?9 y). Grassfeeding
termites had young diet ages (2 y), and wood/soil-feeding termites had the oldest diet
ages (~50 y). Soil-feeding termites were similar in diet age (7?12 y) to wood feeders (8?11 y),
with the exception of one species (18?21 y) that consumes large-diameter wood. A significant
positive relationship was found between diet ages and stable N isotope ratios of the two groups
in the savannah. This relationship held in the gallery forest when termites feeding on woody
tissues were not considered. These 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. Given that
aboveground food webs are often sustained directly by material and energy flow from belowground
food webs, in addition to trophic interactions, gradual enrichment of 15N with the humification of
belowground diets should be considered when interpreting stable N isotope ratios of terrestrial
food webs.

Categoria do assunto: | --
Registro original: | Embrapa Florestas (CNPF)
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