A closeup study of early beech litter decomposition: potential drivers and microbial interactions on a changing substrate.

Aims: Litter decomposition and subsequent nutrient release play a major role in forest carbon and nutrient cycling. To elucidate how soluble or bulk nutrient ratios affect the decomposition process of beech ( L.) litter, we conducted a microcosm experiment over an 8 week period. Specifically, we investigated leaf-litter from four Austrian forested sites, which varied in elemental composition (C:N:P ratio). Our aim was to gain a mechanistic understanding of early decomposition processes and to determine microbial community changes.

Methods: We measured initial litter chemistry, microbial activity in terms of respiration (CO), litter mass loss, microbial biomass C and N (C and N), non purgeable organic carbon (NPOC), total dissolved nitrogen (TDN), NH, NO and microbial community composition (phospholipid fatty acids - PLFAs).

Results: At the beginning of the experiment microbial biomass increased and pools of inorganic nitrogen (N) decreased, followed by an increase in fungal PLFAs. Sites higher in NPOC:TDN (C:N of non purgeable organic C and total dissolved N), K and Mn showed higher respiration.

Conclusions: The C:N ratio of the dissolved pool, rather than the quantity of N, was the major driver of decomposition rates. We saw dynamic changes in the microbial community from the beginning through the termination of the experiment.