Changing enzymatic activities and mycorrhizal infections in a chronosequence of secondary and mature forests of eastern Amazonia
Cláudio José
Reis de Carvalho, Embrapa Amazônia Oriental, carvalho.bel@terra.com.br
(Presenting)
Eric
Atlas
Davidson, The Woods Hole Research Center, edavidson@whrc.org
Tereza
Primo dos
Santos, Instituto de Pesquisa Ambiental da Amazônia, tereza@cpatu.embrapa.br
Fábio
Carneiro
Dutra, Bolsista DTI, CNPQ/LBA, dutrafc@bol.com.br
Bruno
de Oliveira
Serrão, Bolsista ITI, CNPQ/LBA, bruno_serrao@hotmail.com
The availability of nitrogen and phosphorus may limit rates of regrowth of secondary forests in Amazonia. The highly weathered soils are nutrient poor, and numerous cycles of slash and burn can further impoverish nutrient stocks and lead to site degradation. The mineralization of N and P from soil and litter by enzymatic activity and the acquisition of nutrients by mycorrhizae could be important for the recuperation of nutrient cycles during secondary forest succession. These processes were studied in a secondary forest chronosequence (5, 8, 12, 22, 42, and 72 years), a recently abandoned black pepper plantation, and a remnant mature forest in the municipality of São Francisco do Pará. At the end of the rainy season, samples of soil and roots were collected from the litter-soil interface and at 0-5, 5-15, and 15-30 cm depths in mineral soil. Available P, total N, extractable NH4+ and NO3-, urease and acid phosphatase activity, the number of fungal spores, and concentrations of total and readily extractable glomalin were measured. Infections of mycorrhizae were counted in roots. The number of spores and mycorrhizal infections decreased with increasing age of the forest, whereas the activity of acid phosphatase increased with forest age. The concentration of NH4+ and readily extractable glomalin tended to increase with forest age, and NO3- was significantly higher in the mature forest soil. The results indicate that some, but not all, of these indicators of nutrient mineralization and acquisition become similar to the mature forest within 8 years of secondary forest succession.
Submetido por Claudio José Reis de Carvalho em 18-MAR-2004