Wood, 1985; Ljungdahl and Eriksson, 1985). The synthesis and activity of enzymes may

be most regulated through the induction by macrophytic and macromolecular substrates

present in the soils (Burns, 1986; Nausch et al., 1998), with strong relationships

established between lignocellulose-degrading enzymes and litter mass loss rates among

various litter qualities (Sinsabaugh et al., 1992a). Consequently, soils beneath different

plant species have been shown to support microbial communities that differ in both

structure and function (Degens and Harris, 1997; Grayston et al., 2001; Kourtev et al.,

2002a; Kourtev et al., 2003) and can affect sediment nutrients through plant uptake and

rhizosphere characteristics (Templer et al., 1998). Litter breakdown rates and enzyme

activities have been shown to vary among species and have been attributed to intrinsic

factors of the leaves (Linkins et al., 1990a & 1990b; Carreiro et al., 2000; Kourtev et al.,

2002b) such as specific chemical composition (Linkins et al., 1990a & 1990b). For

example, litter N content, presented as C:N or lignin:N are often used as predictors of

decomposition rates (Melillo and Aber., 1982; Sinsabaugh et al., 1993; DeBusk and

Reddy, 1998; Carreiro et al., 2000).

 Microbial degradation by-products and exogeneous nutrients may also influence

microbial activity. For example, polyphenols, the by-products of lignin degradation,

have the potential to inhibit enzyme complexes. These compounds can, in certain

appropriate environmental conditions, become the dominant regulatory mechanisms

involved in microbial respiration (McClaughtery and Linkins, 1990; Wetzel, 1993). The

availability of nitrogen and other nutrients has been shown to control the early phases of

decay, when mass loss is less than 30% (Taylor et al., 1989). Conversely, the addition of

N has been shown to retard the decomposition of large molecular weight organic matter