INVESTIGADORES
GONZALEZ POLO Marina
congresos y reuniones científicas
Título:
Litter decomposition and nutrient release in the Patagonian steppe: carbon and nitrogen turnover decoupled?
Autor/es:
AUSTIN, A.T; VIVANCO, L.; GONZALEZ-POLO, M.
Lugar:
Memphis, Tenessee
Reunión:
Congreso; Annual meeting of the Ecological Society of America; 2006
Institución organizadora:
Ecological Society of America
Resumen:
Litter decomposition and nutrient release in water-limited ecosystems resultfrom the interaction of direct abiotic and biotic controls and are a criticallink in determining nutrient availability and retention, and quality of soilorganic matter. Evidence from various experiments in the Patagonian steppesuggest that the controls on carbon and nitrogen turnover in this ecosystemare distinct, and that traditional models from mesic ecosystems which linkcarbon and nutrient turnover may not apply. The patchy vegetation structureof the Patagonian steppe is reflected in high spatial heterogeneity in soilcharacterstics in vegetated and unvegetated areas. Measurements of both staticbiogeochemical parameters such as soil carbon and nitrogen content, as well asrates of turnover including beta-glucosidase enzyme activity (P<0.01) and netnitrogen mineralization (P<0.001) all demonstrate significantly higher ratesand concentration of nitrogen below shrub patches when compared to unvegetatedpatches. At the same time, litter decomposition shows precisely the oppositepattern, with maximum rates of mass loss occurring in bare soil or standingdead positions and minimum rates below shrubs. Direct manipulative experimentsof solar radiation and soil resource availability support this result ofdifferential controls on organic matter loss and nutrient release. Abovegroundlitter decomposition was strongly affected by intercepted solar radiation(P<0.001) but not through additions of soil substrate C and N, while nutrientrelease from litter demonstrated the opposite pattern, with no significanteffect of photodegradation and significant short-term immobilization of N withadditions of inorganic N and C+N (P<0.01). Taken together, these resultssuggest that carbon and nutrient mineralization in this ecosystem may havedifferent primary controls, with carbon loss largely driven by abioticphotodegradation, and nutrient mineralization mediated biotically, occurringin islands that are protected from the photooxidative effects on organicmatter.