Ecosystem Processes Consequences

While it is clear that many of the effects listed above could potentially lead to quite dramatic effects on various ecosystem processes, there is a dearth of studies which specifically look at this aspect, either qualitatively or quantitatively. Some microcosm studies have demonstrated increased nutrient mineralization from leaf litter colonized by Basidiomycota in the presence of soil fauna (Anderson et al., 1983). Somewhat surprisingly, Collembola grazing did not increase nitrogen mineralization from extra-resource mycelium of P. velutina growing from woody resources into the bulk soil (G.M. Tordoff et al., unpublished). Nonetheless, nutrient release from conservative mycelial systems of cord-forming Basidiomy-cota is likely to occur during grazing (along with during inter-specific mycelial interactions; Chapter 7). Changes in nutrient partitioning within mycelia have the potential to affect the dynamics and spatial heterogeneity of forest floor nutrients.

Basidiomycetes are the primary decomposers of wood and community composition plays an important role in determining the rate of associated ecosystem processes. Toljander et al. (2006) assembled 16 species of boreal wood decay fungi (Chapter 12), 8 brown-rot fungi and 8 white-rot fungi in artificial communities and studied the effect of different community species composition on species persistence, wood decomposition and metabolic efficiency. Decomposition was highest at intermediate diversity levels while metabolic efficiency, estimated as the amount of fungal mycelium formed per amount of degraded wood, decreased with increasing community complexity. A similar study exploring the significance of fungal diversity on ecosystem processes associated with the decomposition of different tropical leaf species suggested differential abundance of fungal species affects rates of decomposition dramatically (Santana et al., 2005). As grazing by invertebrates is known to influence, and in some cases modify (see above examples), fungal community structure the implications of faunal activity may be considerable. This area of study is ripe for further investigation!

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