Simulated wild boar bioturbation increases the stability of forest soil carbon

Abstract

Abstract. Most forest soils are characterised by a steep carbon gradient from the forest floor to the mineral soil, indicating that carbon is prevented from entry into the soil. Bioturbation can facilitate the incorporation of litter-derived carbon into the mineral soil. Wild boar are effective at mixing and grubbing in the soil and wild boar populations are increasing in many parts of the world. In a 6-year field study, we investigated the effect of simulated wild boar bioturbation on the stocks and stability of soil organic carbon in two forest areas. Regular bioturbation mimicking grubbing by wild boar was performed artificially in 23 plots, and the organic layer and mineral soil down to 15 cm depth were then sampled. No significant changes in soil organic carbon stocks were detected in the bioturbation plots compared with non-disturbed reference plots. However, around 50 % of forest floor carbon was transferred with bioturbation to mineral soil carbon, and the stock of stabilised mineral-associated carbon increased by 28 %. Thus, a large proportion of the labile carbon in the forest floor was transformed into more stable carbon. Carbon saturation of mineral surfaces was not detected, but carbon loading per unit mineral surface increased by on average 66 % in the forest floor due to bioturbation. This indicates that mineral forest soils have non-used capacity to stabilise and store carbon. Transfer of aboveground litter into the mineral soil is the only rate-limiting process. Wild boar may speed up this process with their grubbing activity.

Depletion of soil carbon and aggregation after strong warming of a subarctic Andosol under forest and grassland cover

“…However, relative losses in SOC were even more pronounced in the subsoil, indicating that the sampling bias might have been small. However, it should be mentioned that mass-based instead of depth-based sampling (Don et al, 2019) or at least an a posteriori soil mass correction (Ellert and Bettany, 1995) would be indispensable to accurately estimate SOC stock changes.…”

No threat to global soil carbon stocks by wild boar grubbing

“…In a controlled experiment, regular grubbing by wild boar was simulated in two forest areas in Germany in 24 plots for 6 years. Don et al (2019) found no effects of grubbing disturbance on SOC stocks, but in contrast, labile SOC from the forest floor became protected and partly stabilized in the mineral soil. Thus, wild boar grubbing actually enhanced SOC stability.…”

The role of large wild animals in climate change mitigation and adaptation

“…The impact of large animals on soil carbon stocks varies, partly due to differences between biomes and scales, herbivore assemblages and densities and soil community adaptation (Figure 1 and Tables 1 and S1) 6,[54][55][56][57] . For example, herbivores can help preserve soil carbon by maintaining permafrost in the Arctic 58 , maintaining below-ground carbon in fire-prone ecosystems 59,60 , stabilising soil carbon through soil mixing 61 and through the activities of their associated soil macrofauna (e.g. earthworms, dung beetles [62][63][64] ).…”