The legacy of acidic deposition controls soil organic carbon pools in temperate forests across the Czech Republic

Abstract

AbstractTemperate forest ecosystems store most of the organic carbon in soils (SOC), and changes in the soil carbon stock due to climate change or land management can potentially have a large influence on carbon balance. The most important factors controlling the SOC pool on a global scale are generally agreed upon; however, estimations of SOC pools differ significantly among studies at regional and local scales due to different sampling protocols and local scale variability. This study evaluates the SOC pool in the forest floor and mineral soil sampled down to a depth of 80 cm in 14 forested catchments with variable environmental conditions and soil acidification and eutrophication legacies, and determines the best explanatory variables of the SOC pool. The average SOC pool of 34 t ha−1 measured in the forest floor (O horizon) was best explained by measures of historical sulphur (S) deposition (i.e., soil acidification legacy) and forest type (conifer vs. broadleaf forest). An average total SOC pool of 132 t ha−1, combining both the carbon pool in the mineral soil down to 80 cm and the carbon pool in forest floor, was best explained solely by elevation, which reflects temperature and precipitation gradients. However, when considering the coupled SOC pool in the forest floor and upper half of the sampled mineral soil (down to 40 cm), natural environmental factors were outweighed by anthropogenic ones (soil acidification legacy and forest type). This has important implications for understanding potential SOC pool changes under ongoing global climate change, especially in regions currently or historically affected by soil acidification caused by acid deposition. The acidification effect on the SOC accumulation and subsequent soil recovery after acidification retreat might affect carbon balance.Highlights The SOC pool is dependent on soil acidification legacy, forest type and climatic gradient. Anthropogenic factors outweigh the natural ones if shallow sampling is carried out. Shallow sampling commonly carried out in forest soils underestimates the SOC pool. Soil acidification caused SOC accumulation and subsequent soil recovery might lead to carbon loss.