Contribution of litter layer to soil greenhouse gas emissions in a temperate beech forest

Background and aims

The litter layer is a major source of CO₂, and it also influences soil-atmosphere exchange of N₂O and CH₄. So far, it is not clear how much of soil greenhouse gas (GHG) emission derives from the litter layer itself or is litter-induced. The present study investigates how the litter layer controls soil GHG fluxes and microbial decomposer communities in a temperate beech forest.

Methods

We removed the litter layer in an Austrian beech forest and studied responses of soil CO₂, CH₄ and N₂O fluxes and the microbial community via phospholipid fatty acids (PLFA). Soil GHG fluxes were determined with static chambers on 22 occasions from July 2012 to February 2013, and soil samples collected at 8 sampling events.

Results

Litter removal reduced CO₂ emissions by 30 % and increased temperature sensitivity (Q₁₀) of CO₂ fluxes. Diffusion of CH₄ into soil was facilitated by litter removal and CH₄ uptake increased by 16 %. This effect was strongest in autumn and winter when soil moisture was high. Soils without litter turned from net N₂O sources to slight N₂O sinks because N₂O emissions peaked after rain events in summer and autumn, which was not the case in litter-removal plots. Microbial composition was only transiently affected by litter removal but strongly influenced by seasonality.

Conclusions

Litter layers must be considered in calculating forest GHG budgets, and their influence on temperature sensitivity of soil GHG fluxes taken into account for future climate scenarios.