Soil denudation rates in an old‐growth mountain temperate forest driven by tree uprooting dynamics, Central Europe

Abstract

AbstractTree uprooting may distinctly affect landscape dynamics and slope denudation. Little is known, however, about the corresponding soil redistribution rates (erosion and accumulation) on either a long‐term (millennia;10Be) or a short‐term (decades;239+240Pu) scale. We determined these rates in a well‐investigated forest reserve (Zofinsky primeval forest, Czech Republic) using complementary techniques: nuclides in soils and tors to derive short‐ to long‐term rates and monitoring data (43 years) of repeated tree censuses using tree uprooting data. Temporal trends of soil erosion rates were obtained by dating the timing of exhumation (10Be) of tors. The average long‐term denudation rates were about 30–40 t km−2yr−1. It seems that these rates varied over time with probably a maximum during the Pleistocene/Holocene transition (58–91 t km−2yr−1).239+240Pu activities in the soils identified soil redistribution rates of 50 to >100 t km−2yr−1for the last decades and agree with results from the tree uprooting monitoring (<92 t km−2yr−1). In‐situ10Be in soils gave similar denudation rates (58–76 t km−2yr−1). Meteoric10Be provided a mean residence time of a soil particle of 33–100 ka supporting the measured average long‐term erosion rates. Soil aggregates indicated stable physical conditions meaning that soil mass redistribution occurs only sporadically. It seems that the main driving factors of denudation changed over time. An erosion peak at the Pleistocene/Holocene transition (climate change) seems likely but needs further proof. Over the last few millennia, tree uprooting seems the main driver of soil erosion.