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Acta Amazonica

Print version ISSN 0044-5967On-line version ISSN 1809-4392

Acta Amaz. vol.9 no.2 supl.1 Manaus  1979

https://doi.org/10.1590/1809-43921979092s005 

ARTIGOS

Pastagens da Amazônia Central: Ecologia e fauna do solo

Mário Dantas1 

1Empresa Brasileira de Pesquisa Agropecuária - EMBRAPA


RESUMO

Foram estudados os micro-artrópodos do solo, bem como a cobertura vegetal, fauna de cobertura, respiração edáfica, além de fatores físico-químicos do solo e climáticos, em pastagens artificiais de terra firme próximo a Manaus. De janeiro a dezembro de 1977 foram realizadas 21 amostragens, perfazendo 1304 unidades com 12,56 cm2de área e até 5 cm de profundidade. A fauna foi extraída pelo método Berlese-Tullgren, modificado. Acari o Collembola foram os grupos dominantes do solo em todos os ambientes. Foram encontrados até 22 grupos de artrópodes na pastagem e 26 grupos na floresta. Na pastagem, as densidades de Acari variam de 32.000 a 73.000/m2e de Collembola de 4.000 a 35.000/m2, Na floresta, urna única estimativa deu como resultado 49.000/m2para Acari e 12.000/m2para Collembola. A pastagem extensiva e o sistema rotacional não apresentaram diferenças na fauna do solo. Diferenças foram encontradas entre pastagens formadas por diversas gramíneas e com diferentes idades, e também entre pastagem e floresta primária, principalmente com relação ao número de grupos encontrados. As populações de artrópodes encontram-se agregadas e as de Acari e Collembola em particular são descritas satisfatoriamente pelo distribuição binomial negativa. A respiração edáfica sob Setaria sp. apresentou-se com média de 455,7 (dia) e 448,1 (noite) mg/CO2/m2/h e sob diversas espécies de Solanaceae de 507,0 (dia) e 483,6 (noite) mg/CO2/m2/h.

SUMMARY

The present work was comparative ecological study of soil fauna In several pasture systems and a nearby area of primary forest. A total of 1304 soil samples, each of 12,56 cm2 area to a depth of 5 cm, were taken on 21 dates between January and December of 1977. Fauna were extracted with a modified Berlese — Tullgren method, using 1% formol as the liquid collector. Identifications were made to the level of major group (subclass or order, or family). Study sites were in the municipalities of Silves and Itacoatiara, Amazonas, Brazil, with the primary locality at Fazenda Aruanã (3°08'S, 58°45'W). The soil was a heavy yellow latosol (oxisol) of pH 3,4 to 5,9. Environmental parameters measured included soil temperature, moisture, fertility organic matter content, vegetative cover of grasses and invading plants, and solar radiation. Climatic factors recorded were mean air temperature, relative humidity, and precipitation. Comparisons were made between intensive and extensive Setaria pasture systems extensive systems with other grasses and of several ages, and primary forest. Mites and Collembolans were the dominant soil fauna in all environments. Up to 22 groups (subclasses or orders) of Arthropods were found in the pasture and 26 in the forest. In the pasture mite densities varied between 32.000 and 73.000 per square metter and Collembolan densities between 4.000 and 35.000 per square meter. In the forest densities were 49.000 and 12.000 per square meter for mites and Collembolans respectively. There was no statistically significant difference between the soil faunas of the two Setaria pasture systems, there were differences between different grass species and different ages of extensive systems. The primary forest differed from the Setaria pastures pricipally in the number of groups of Arthropods found. There was an apparent difference in vegetative cover of intensive and extensive Setaria systems, but it is suspected that this was an incorrect result attributable to problems of methodology. The forest soil had more stable temperatures, higher and more constant moisture content throughout the year, lower fertility, and higher organic matter content than the pasture soil. In the forest solar energy at 1,5 m above the soil was only 0.06 cal/cm2/min while in the pasture it was 1,59 cal/cm2/min. The arthropod populations were found aggregated and those of the mites and Collembolans were satisfactorily described by the negative binomial distribution. In general there was no correlation between physical and edaphic factors and the soil fauna. Collembolans showed a negative correlation with air temperature and precipitation, and a positive correlation with relative humidity in pasture. Acari showed a positive correlation with organic matter content of the forest soil. There was a positive correlation between numbers of mites and Collembolans at least in the intensive Setaria pasture systems (calculated by the Spearman coeficient of rank correlation). Soil respiration under Setaria sp. was 455,7 (day) and 448,1 mg CO2/m2/h (night) and under Solanaceae was 507,0 (day) and 483,6 mg CO2/m2/h night).

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