Abstract
Deadwood is widely recognized as a source of carbon dioxide (CO 2 ) emissions during decomposition. Accurately assessing CO 2 fluxes from deadwood-influenced soil under field conditions is essential for understanding the role of deadwood in the carbon (C) cycle. To this end, we implemented a field-based, closed-chamber approach and measured CO 2 fluxes over a period of nearly 1.5 years at three different study sites, one on silicate and two on calcareous bedrock. We included different microsites in our measurements: lying deadwood, adjacent soil and corresponding controls without current deadwood impact. Soil temperature emerged as the main driver of seasonal variation in CO 2 fluxes across all microsites. CO 2 fluxes from control microsites varied significantly among sites, whereas CO 2 fluxes from deadwood and adjacent soil were relatively consistent across sites. Simultaneously, we assessed dissolved organic carbon (DOC) fluxes in soil adjacent to the same logs (deadwood-influenced soil) and in control microsites and related them to the CO 2 fluxes. DOC fluxes accounted for only 0.45 ± 0.12% of soil CO 2 fluxes in control soils and 0.84 ± 0.38% in deadwood-influenced soils. However, deadwood increased both CO 2 and DOC fluxes at the study sites. The magnitude of this increase was highly site-dependent: the strongest relative increase in DOC fluxes occurred at one of the calcareous sites, whereas the largest relative increase in CO 2 was observed at the silicate site. Our findings show that deadwood plays a dual role: C is primarily released as CO 2 from both the deadwood and the soil it influences, but it also contributes to DOC accumulation in the underlying soil. These findings highlight the importance of accounting for local soil conditions when evaluating the implications of deadwood retention on forest C balances. CO 2 measurements conducted with the closed-chamber approach were precise, supporting the reliability of the observed fluxes.