Rates of breakdown for five terrestrial litter types in an abandoned beaver pond followed the sequence Salix sp. leaves > Deschampsia cespitosa leaves and stems > Juncus tracyi leaves and stems > Pinus contorta needles > Picea glauca bark. Dry weight loss for all litter types showed a very close fit to Olson's (1963) negative exponential decay model but breakdown rates (k values of Olson) were low in comparison to those recorded for other aquatic systems. It is suggested that k values for litter in streams may be high due to physical fragmentation of litter by the current. In Salix, Pinus and Picea bark, significant nitrogen enrichment occurred but phosphorus was released slowly whereas in Juncus and Deschampsia nitrogen enrichment did not occur and phosphorus was released rapidly. Phosphorus immobilization appears to be linked to nitrogen enrichment. After an initial period of adjustment carbon/nitrogen and carbon/phosphorus ratios stabilized at the following values: for Salix (25:1 and 6000:1), for Deschampsia and Juncus (37.5:1 and 1600:1), for Pinus (45:1 and 1400:1) and for Picea bark (65:1 and 2000:1). Potassium was rapidly leached from all litter types until a critical carbon/potassium ratio of between 500:1 and 1000:1 was reached, beyond which it became relatively immobile.
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文章 : 英语