FIGURE 2.4 Maximum estimates of fungal hyphal length (open bars) and fungal biomass (hatched bars) in soils from a range of ecosystems. Source: From Kjøller and Struwe (1982).

In coniferous forests, plant biomass is high and litter fall is low, but accumulation occurs, mainly because of the recalcitrance of the litter to decomposition (low resource quality). Harborne (1997) describes the nature of plant phenolics, suggesting that external leaf phenolics are admixed with leaf waxes and have antifungal properties that reduce germination and growth of phyllosphere fungi (Table 2.10). The degree to which these phenolics inhibit or regulate rates of fungal colonization of leaf litter and interact with mycorrhizal fungi is an area of current research.