Solar UV-B decreases decomposition in herbaceous plant litter in Tierra del Fuego, Argentina: Potential role of an altered decomposer community.

VERONICA ANDREA PANCOTTO; SALA, O. E.; CABELLO, M.; LOPEZ, N. I.; ROBSON, M.; BALLARÉ, C. A.; SCOPEL, A. L.; CALDWELL, M. M.

GLOBAL CHANGE BIOLOGY

Blackwell

Año: 2003 vol. 9 p. 1465 - 1474

1354-1013

Tierra del Fuego, Argentina (551S), receives increased solar ultraviolet-B radiation (UV-B)as a result of Antarctic stratospheric ozone depletion. We conducted a field study toexamine direct and indirect effects of solar UV-B radiation on decomposition of Gunneramagellanica, a native perennial herb, and on the native community of decomposerorganisms. In general, indirect effects of UV-B mostly occur due to changes in thechemical composition of litter, whereas direct effects during decomposition result fromchanges in decomposer organisms and/or differences in the photochemical breakdownof litter.We designed a full-factorial experiment using senescent leaves that had receivedeither near-ambient or attenuated UV-B during growth. The leaves were distributed inlitterbags and allowed to decompose under near-ambient or reduced solar UV-B duringthe growing season. We evaluated initial litter quality, mass loss, and nutrient release ofdecomposing litter, and microbial colonization of both initial litter and decomposedlitter. We found that litter that decomposed under near-ambient UV-B had significantlyless mass loss than litter that decomposed under reduced UV-B. The UV-B conditionsreceived by plants during growth, which did not affect mass loss and nutrientcomposition of litter, affected fungal species composition but in different waysthroughout the decomposition period. Before the decomposition trial, Beauveriabassiana and Penicillium frequentans were higher under reduced UV-B, whereasCladosporium herbarum and pigmented bacteria were more common under the nearambientcompared to the reduced UV-B treatment. After the decomposition period,leaves that had grown under reduced UV-B showed higher frequency of Penicilliumthomii and lower frequency of Trichoderma polysporum than leaves that had grownunder near-ambient conditions. The UV-B condition received during decomposition alsoaffected fungal colonization, with Penicillium chrysogenum being more frequent inleaves that had decomposed under reduced UV-B, while the other species were notaffected. Our results demonstrate that, in this ecosystem, the effects of UV-B radiation ondecomposition apparently occurred mostly through changes in the fungal community,while changes in photochemical breakdown appeared to be less important.