Effects of Nutrient Enrichment on Decomposition and Fungal Colonization of Sweet Chestnut Leaves in an Iberian Stream (Central Portugal) |
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Authors: | Manuela Abelho M A S Graça |
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Institution: | (1) Instituto Politécnico de Coimbra, Escola Superior Agrária, 3040-316 Coimbra, Portugal;(2) Departamento de Zoologia da Universidade de Coimbra, IMAR – Centro Interdisciplinar de Coimbra, Largo Marquês de Pombal, 3004-517 Coimbra, Portugal |
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Abstract: | This study assessed the effect of nutrient enrichment on rates of decomposition, ergosterol concentrations (as a measure of
fungal biomass), and rates of fungal sporulation of sweet chestnut (Castanea sativa Miller) leaves in a 3rd order stream (Central Portugal), with medium to high background values of nutrients. Coarse and fine
mesh leaf bags were attached to nutrient diffusing substrata containing NaNO3, KH2PO4, both nutrients, or no additions. Leaf breakdown rates were similar in the four treatments and in the two mesh sizes (k=−0.0155 to −0.0219 day−1). Phosphorus content of P or N + P enriched leaves was higher than in the other treatments after 28 days, but there were
no differences in N concentrations. Ergosterol concentrations associated with decomposing leaves were similar among treatments.
The peak sporulation rates of aquatic hyphomycetes were stimulated by the addition of N + P and N but not by P alone. Results
from the experiment provide evidence that leaf breakdown in the study stream, as a model for streams with naturally medium
to high level of nutrients, was not nutrient-limited, and that fungal reproductive activity was limited by dissolved N but
not by dissolved P in stream water. |
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Keywords: | aquatic fungi streams nitrogen phosphorus leaf breakdown fungal biomass ergosterol sporulation rates nutrient enrichment 3rd order stream Central Portugal |
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