Soil VOC Storage and Emissions Across Horizons in Douglas Fir and European Beech Forests

Soils are both significant carbon reservoirs and sources of carbon emissions, playing a critical role in the global carbon cycle. In addition to CO₂ emissions from soil respiration, volatile organic compounds (VOCs) significantly influence atmospheric chemistry, ecosystem processes, and climate feedback mechanisms. While biogenic VOCs (BVOCs) from plants are well-studied, the contribution of soil-emitted VOCs remains relatively underexplored, particularly their distribution and dynamics across soil depths in forest ecosystems. This study aimed to quantify depth-specific soil VOC storage and emissions, investigate their relationship with CO₂ emissions as an indicator of microbial activity, and assess how litter characteristics influence these dynamics.

The research was conducted in two forest plots at the ECOSENSE site located in the Black Forest, Germany. The plots were dominated by Douglas fir (coniferous) and European beech (broadleaf) trees. We examined VOC storage and emissions across soil depths, compared their proportions to CO₂ emissions, and assessed how microbial activity and litter properties shaped these soil VOC dynamics.

Our findings reveal that VOC storage and emissions varied significantly with soil depth and litter characteristics. More specifically, VOC storage and emissions were much higher in the Douglas fir plot than those in the European beech plot, highlighting the influence of tree species-specific chemical inputs. This foundational understanding of soil VOC dynamics provides critical insights into their potential role in climate feedback mechanisms and supports future efforts to model VOC fluxes under changing environmental conditions.