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Soil macrofauna, biodiversity, principal component analysis, soil quality, soil management. Palabras clave: The dominant pattern is the conversion of the native vegetation rainforest or Cerrado, the Brazilian savanna to agriculture by logging and burning.

As a consequence, the landscape that results from this colonization process is a mosaic of lands in agricultural use and secondary forests of various ages Vieira et al.

In this context, secondary forests fallows play a key role for soil Dunn and plant biodiversity conservation Vieira et al. Considering the fundamental role of soil macrofauna and its diversity in soil functions Lavelle et al. Experimental design Six land uses were evaluated for their impact on soil macrofauna: Cropping systems and forests plots had 2 ha each in size x m and were located at the UFRA Experimental farm while the pasture plots had 1.

All plots for macrofauna sampling were installed in January Kato, personal communication. A fragment about 5 ha of the 15 yr secondary forest was conserved as a control and used to install the 20 yr secondary forest plot of 2 ha in Macrofauna was sampled in March rainy season and September dry season , only the rainy season results are presented here.

Four principal components were retained for earthworms and ants while only two were retained for other matrices. Nested multivariate analyses of variance MANOVA were performed to test the effects of land use on the invertebrate communities with transects as nested factor Legendre For each axis, the variables with contributions superior to half of the highest contribution were retained. It was then assumed that invertebrate abundances were positively and linearly correlated with soil health.

The transformed abundances were multiplied by their contribution on each axis and these products were summed. PSB and F20 had intermediate abundances Fig. Ant abundance varied from in PSB to ind. No significant differences were detected between land uses Fig. The abundance of other invertebrates varied from in SB to ind. Earthworm richness was significantly different between PCM 2. Shannon diversity had the same pattern but F40 was the most diverse 0. Ant richness was greatly and significantly higher in F40 6.

Shannon diversity followed a similar pattern, but F20 and SB had intermediate diversity 0. The richness of other invertebrates was significantly higher in CM Diversity was also the highest in CM 0. Principal Component Analyses Eight earthworm genera were identified and they explained On axis 1, Glossodrilus adult and immature associated with F40 and SB, and was opposed to Pontoscolex immature that was associated with F On axis 2, Pontoscolex immature and Glossodrilus associated with forests and SB, were opposed to other genera including Pontoscolex adult that were associated with pastures and CM Fig.

The axis 3 opposed Pontoscolex adult and immature and other unidentified genera associated with CM, to Dichogaster adult and immature associated with PCM. They explained In addition to earthworms and ants, 19 invertebrate groups were identified 13 retained in PCA. The axis 1 represented S and H' gradient and opposed F20 and pastures to F Species richness and diversity index was significantly higher in F40 0. The integrated macrofauna index identified CM as the significantly better land use 0.

Ants were the dominant group both in terms of abundance and biomass, probably as a result of the collection date dry season and sample location litter.

Due to the lack of taxonomical information for the region, studies usually use parataxonomy Mathieu et al. In the present study, two major groups earthworms and ants were studied until genus level with the help of one specialized taxonomist per group, while the other groups encountered were identified only superficially order was the maximum taxonomic level. The relative precision of the community description led to the separation of the invertebrates in three matrices plus a matrix for richness and diversity, in order to maximize the potential of each major group to discriminate land uses for their impacts on soil macrofauna communities.

The first axis is the more difficult to interpret as it opposed the Glossodrilus genera populations, that dominate F40 and SB, to a huge immature Pontoscolex Pontoscolex i population in F Indeed, this forest showed evidences of recent illegal logging that modified locally the forest cover illegal wood extraction is very common in the region; Margulis and older modifications in the soil as remnants of graveled road, evidenced by local soil compaction and texture modification data not shown.

The evidence of soil importation on the site may help explain the dominant nature of the Pontoscolex population, as this genus is considered invasive and associated with human activities Barros et al. The second axis clearly separated the open pastures and CM vs.

Open environments were associated to more genera richness while forests and fallow were dominated by Glossodrilus and immature Pontoscolex Fig. The third axis opposed the pastures to all other land uses because of the presence of Dichogaster, an exotic genus from Africa Blakemore , which is present almost exclusively in the pastures only a few individuals in CM and was sampled preferentially in association with the B. In Amazonian pastures, B. The PCA on ants was dominated by a few genera while most had low contribution to the axes short arrows Fig.

To help in the interpretation of the ant community structure among land uses, genera were classified according to their ecological habits Fernandez Although this classification was devised for the Cerrado no such classification is available for Amazonian rainforest ants it was consistent with the present results.

On axis 2 Acropyga and Paratrechina separated the pastures from the crops. Acropyga is classified as a soil specialist and was the dominant genus in pasture, suggesting a good adaptation to the compacted soils with little or no litter. On the contrary, Paratrechina, classified as soil and vegetation opportunist, abounded in the crops that had thick 1.

The fact that the first three genera are classified as vegetation opportunists Camponotus can also be classified as a "patrolling generalist", Fernandez reflect the switch in vegetation cover from open or fallow systems to real forest cover while the higher abundance of predator specialist Hypoponera or the "big epigeic predators" Pachycondyla and Ectatomma indicate a higher ecosystem "maturity" Odum , Neutel et al. On the fourth axis Pheidole characterized F20 while Brachymyrmex and the predator genera were associated with F40, thus confirming the higher maturity of the old secondary forest Fig.

The PCA of the other invertebrate groups had only two relevant axes with most of the variability explained by the first axis Mathieu et al. In Africa Cameroon , termite communities were similar in secondary and primary forest in several studies Eggleton et al. Indeed, the mulch provided soil protection and food supply establishing an environment similar or better to the fallow vegetation Mathieu et al.

The PCA on species richness and Shannon diversity index was the most explicative Table 1 and confirmed that the old secondary forests have a well developed macrofauna structure that is more similar to that of mature ecosystems, with the highest richness and diversity of ants, the highest diversity of earthworms and also high richness and diversity of others invertebrates Fig.

However, the plots studied experienced only one fire and were converted from primary forest very recently less than 10 yr previous Mathieu et al. As a matter of fact, earthworm proliferation after forest conversion to pasture has often been reported in Amazonia, but is often associated to large populations of the invasive species P. The ant index was the only one that did not detect significant differences between land uses, probably because the index retained only five ant genera in the variable selection data not shown , thus suggesting a limitation in the use of the index when rare species dominate the community.

Indeed, PCA is not devoted to select a subset of the most discriminant variables from a large data set. However, special attention must be paid to the nature of relationship between the indicator variables and soil health. This could be misleading in some occasions for macrofauna, for example with proliferation of soil compacting worms as P.

As a conclusion, the MISH proved to be useful in separating the land uses but still needs to be fully tested and eventually refined, to provide reliable indication of soil health. Ant richness and diversity greatly benefited from the secondary forests of both ages, while earthworms had more diverse populations in the pastures and similar diversity in pastures and old secondary forest.

Indeed, the land use mosaic created by smallholder agriculture has proved to support high biodiversity in this study as in former ones Baar et al. We also would like to gratefully thank O. Tropical soil biology and fertility: CAB International, Wallingford. A comparison of soil quality indexing methods for vegetable production systems in northern California. Agriculture Ecosystems and Environment.

Ribeiro, A. Nobre, R. Evaluation of soil fertility in smallholder agroforestry systems and pastures in western Amazonia. Cordeiro, M. Biodiversity and Conservation. Pashanasi, R. Biology and Fertility of Soils. VermEcology, Kippax. James, A. Pasini, D. Nunes, N. Benito, P. Exotic, peregrine and invasive earthworms in Brazil: Caribbean Journal of Science. Vlek, T. Recovery of faunal communities during tropical forest regeneration.

Conservation Biology. Soil biodiversity and its implications for ecosystem functioning in a heterogeneous and variable environment. Appied Soil Ecology Bignell, S. Hauser, L. Dibog, L. Termite diversity across an anthropogenic disturbance gradient in the humid forest zone of West Africa. Bignell, W. Sands, N.

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Lo notable de las tierras negras del Amazonas es que con un adecuado y casi elemental nivel de manejo no pierden la fertilidad, ni con el tiempo ni con las cosechas sucesivas Petersen et al. Mitigation and Adaptation Strategies for Global Change 11, En Amazonian Dark Earths: Kluwer Academic Publishers, Dordrecht, Netherlands. Origin, Properties, Management. Radiocarbon 43, Shneour E Oxidation of graphite carbon in certain soils. Science , McGraw-Hill, New York.

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