The forgotten ecosystem engineers: community and functional ecology of pioneer wood decay fungi in the canopy of beech trees

Dead wood is a vital, diverse habitat which contributes substantially to woodland ecosystem function and biogeochemical processes. The major original source of woody debris is to be found in the canopy in the form of dead attached branches. Such branches also provide major habitat for the pioneer wood decay community which is known to influence the assembly trajectory, and therefore functioning, of later successional stages through priority effects. Very little is known however about the pioneer community’s own structure and functioning. This thesis sets out to shine a light on these forgotten engineers of our woodland ecosystems. Natural pioneer communities in dead attached beech branches were examined through isolation techniques and Sanger sequencing. Community structure was found to be driven predominantly by physical characteristics of tree branches, including their diameter and the gradient of decomposition. Pure spatial factors played a lesser role, indicating that mycelial spatial configuration results predominantly from the influence of environmental gradients. No relationship was found between community diversity and branch volume indicating that community establishment is driven by a race for space in a highly homogeneous resource. Natural community function was examined using quantitative enzyme assays and untargeted GC-MS metabolomics. Laccase activity increase over the decay gradient suggesting development of an increasingly toxic environment. Untargeted metabolomics was applied to naturally decaying wood samples for the first time, highlighting a linear covariance of laccase activity with the metabolome. GCMS metabolomics was also applied in combination with direct shotgun LC-MS/MS proteomics to experimental wood systems. There was considerable evidence that a variable temperature regime may enhance lignin degradation in Oudemansiella mucida compared with stable temperature. A clear priority effect was exerted on the proteome of Exidia glandulosa by earlier arriving species, but not by different temperature regimes, suggesting that biotic interactions may play a more important role in the pioneer community than previously thought.