Changes in bacterial communities and Azospirillum diversity in soil fractions of a tropical soil under 3 or 19 years of natural fallow
The effects of 3 and 19 yr natural fallows on soil structure and soil bacteria were assessed by aggregate size fractionation of a tropical sandy soil (0–10 cm). Bulk unfractionated soil and fractions including particulate coarse organic residues (COR), and four fractions (>2000, 50–2000, 2–50 and...
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Veröffentlicht in: | Soil biology & biochemistry 2002-08, Vol.34 (8), p.1083-1092 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | The effects of 3 and 19
yr natural fallows on soil structure and soil bacteria were assessed by aggregate size fractionation of a tropical sandy soil (0–10
cm). Bulk unfractionated soil and fractions including particulate coarse organic residues (COR), and four fractions (>2000, 50–2000, 2–50 and 50
μm), suggesting that these microhabitats were favourable to active N
2 fixers. In contrast, more than 70% of the N
2 fixing microorganisms and 90% of the recovered
Azospirillum were isolated from the dispersible clay fraction (0–2
μm). Diversity of
Azospirillum species was assessed by hybridisation with specific genetic probes on colonies within each fraction. This approach revealed the abundance of
Azospirillum irakense in the 3
yr fallow soil fractions only and a selective effect of fallow on
Azospirillum brasilense/
Azospirillum amazonense genomic species in the 19
yr fallow soil. These changes would remain hidden, if the investigation had been restricted to the unfractionated soil. |
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ISSN: | 0038-0717 1879-3428 |
DOI: | 10.1016/S0038-0717(02)00041-X |