Leaf traits interact with management and water table to modulate ecosystem properties in fen peatlands

Trade-offs between slow and fast nutrient turnover rates among plants may affect soil properties and biomass production. We examined how plant traits interact with abiotic variables to modulate ecosystem properties (soil C, soil C/N ratio, aboveground biomass) in peatlands. We determined the interacting effects of abiotic variables (vegetation management, water table height) and leaf traits (specific leaf area, leaf dry-matter content, leaf C/N ratio) on ecosystem properties in two lowland fens in East Anglia, UK using structural equation modelling. Our models explained between 21% and 95% of the variability in ecosystem properties. Leaf traits directly influenced soil nutrient content and plant biomass and mediated the effects of abiotic variables on ecosystem properties. Abiotic variables exerted larger effects on ecosystem properties among herbaceous communities, but leaf traits were equally important when modelling all communities in combination. The expected trade-offs between exploitative and conservative life strategies among species scaled-up to changes in soil properties and biomass production, even in fen habitats where abiotic variables play an important role through marked seasonal variations. Our findings suggest an important role of leaf economics in the functioning of fens, but their effects on ecosystems may be highly dependent on local conditions.