Data/hora: 09/06/2024 23:53:34

Biblioteca(s): | Embrapa Florestas.
Data corrente: | 15/09/2008
Data da última atualização: | 15/09/2008
Autoria: | MARGERIE, P.; BARETTA, D.; AKPA-VINCESLAS, M.; DECAËNS, T.
Título: | Nutrients production in casts of Lumbricidae and vegetation biomass on a chalky slope of the Seine valley : a multivariate analysis.
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:

The chalky slopes of the Seine valley (Upper Normandy, France) are supporting semi-natural
grasslands subjects to a process of secondary succession, which leads to a mosaic of stages
from short grasslands to maple woods. Soils are rendzinas, supporting high densities and
biomasses of macrofauna, mainly earthworms (80 to 120 g m-²). A median stage of the succession
is the Brachypodium tall grassland, which is stable when compared to other stages for at least
some decades. Earthworm populations in this vegetal formation have previously been proved
to exhibit spatial patterns with patches of ca. tenth of meters. In the homogeneous tall grassland,
these patterns are not correlated with those of the floristic composition. We hypothesise in this
work that, given that earthworms are known to provide an important source of nutrients in their
casts (microsites of efficient mineralisation), the biomass of the tall grassland vegetation is
correlated with earthworm cast-derived nutrients amount in the soil.
A three-steps procedure was used: (i) we assessed the kinetics of nutrients (N-NO3-, N-NH4+,
P-P2O5) in casts produced in the laboratory by five earthworm species (32-days incubation),
and we used these results to (ii) estimate the amount of nutrients produced by real earthworm
populations in field conditions and (iii) to explore the relationships between above- and
belowground vegetation biomasses and cast-derived nutrients.
Results obtained from step (i) are consistent with those of the literature with NH4+ and P2O5
following a roughly bell shaped curve, reaching its acme between 2 and 12 days after cast
production. Phosphorus increased up to 7-fold the mean amount in soil, and NH4+ up to 2.3-
fold. We found significant differences among earthworm species, with the anecic Aporrectodea
giardi being the best nutrient provider in the laboratory. NO3- did not show any apparent dynamic
in casts, with less than 10% variation compared to soil.
The extrapolation to the field was made using a small scale study of earthworm populations and
vegetation biomasses which took place on the chalky slope of Saint Adrien (64 points of 0.125
m² located on a 4 m² tall grassland surface in a square jointive design). Neither earthworm
associations nor vegetation composition exhibited significant spatial pattern. A principal
components analysis performed on vegetation above- and belowground biomasses and casts
nutrient production estimated from earthworm biomass led to an axis 1 (26.3 % of total variance)
interpreted as a size effect with all variables displaying positive values and an axis 2 (21.6 % of
total variance) exhibiting a segregation between (a) aboveground biomass except the ligneous
plants and (b) belowground and ligneous biomasses and nutrient production.
Perspectives include the extrapolation of these small-scale results to the scale at which earthworm
spatial patterns are documented, in order to quantify the potential role of earthworm populations
in the kinetic of secondary succession

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