Ecological interactions between fungi, other biota and forest litter composition in a unique Scottish woodland

The composition of forest litter and understorey layer, and fungal biomass (in terms of ergosterol) were measured in eight subplots over a winter-spring period (January to April). The sampling site was positioned in a range of woodland habitats (variously dominated by beech, Fagus sylvatica; birch, Betula pendula x pubescens, and oak Quercus petraea) and a clear area covered with grass (dominated by Holcus lanatus). The results were analysed together with data on bacteria and microinvertebrates available from parallel research. Levels of ergosterol in individual subplots ranged between 50 and 160 mu g g(-1) DW. Fungal biomass decreased in March, and then increased significantly in April. Stepwise regression models for ergosterol indicated positive relationships with moisture content (February), bacteria (all but February and March), flagellates (February) and plant-feeding nematodes and flies (January, overall). The relationships with roots, seeds, the collective variable 'other microinvertebrates' (all March), amoebae (February) and fragments (March, overall) were negative, while the relationship between fungi- and microbial-feeding nematodes changed sign between February (-) and March (+). Results of analysis of covariance for fungal ergosterol were significant only for January and the combined dataset. In January, fungi were shown to be significantly related to amoebae, bacteria and a collembolan Folsomia candida, while the only significant predictor returned by the overall model was bacteria. Correlation analysis confirmed some effects already noted, and revealed a number of further interactions. The results highlighted the complexity of factors influencing temporal dynamics and spatial variability of fungal biomass in forest litter. Most of the registered interactions appeared to be transient, and this should be taken into account while interpreting environmental observations. Interpretation of the specific relationships is given and implications for further research and overall ecosystem functioning are discussed.