Humus plays an important role in the functioning of forest ecosystems. It acts as a link between above- and below-ground ecosystem compartments. The fall and decomposition of organic matter return minerals and energy to the soil biota. The forest floor is the most dynamic part of soil organic matter (Yanai et al. 2003). Previous studies about nutrient release from forest litters, formed under various tree species, show significant differences in dynamics of nutrients. The release of nutrient elements during decomposition of forest floor is an important internal pathway in nutrient flux of forested ecosystems. Nutrients may be released from ectohumus horizons by leaching or mineralization (Regina, 2000). Nutrient release from decomposing litter affects the primary productivity of ecosystem, since these nutrients become available for plant uptake and are not lost in the ecosystem. The rate at which nutrients are released depends on several factors: the chemical composition of the forest litter, the structural nature of the nutrient in the litter matrix, the microbial demand for the nutrient, and the availability of exogenous substance sources for example from anthropogenic activity (Brown et al., 1999). Litter quality affects the rates of mass loss, but also the patterns and rates of nutrient immobilization or release. Forest litter highly contaminated with heavy metals may effect nutrient cycling throughout the whole ecosystem (Tyler, 1974). Many reports have shown that short-term or long-term exposure to toxic metals results in the reduction of microbial diversity and activity which is mainly observed in inhibiting litter decomposition and increase of undecomposed organic matter in humus layer (Berg et al., 1991). From the other hand, forest litter acts like a sink for contaminants, regulating the amount of heavy metals leaching to deeper soil layers (Medynska and Kaba?a, 2007 Laskowski et al. 1995). Dynamics of heavy metals in contaminated forest floor is exceptionally investigated, and in particular - on recently afforested soils, where the ectohumus layer has been already formed.
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