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

Abstract

Tree 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−2 yr−1. It seems that these rates varied over time with probably a maximum during the Pleistocene/Holocene transition (58-91 t km−2 yr−1). 239+240Pu activities in the soils identified soil redistribution rates of 50 to >100 t km−2 yr−1 for the last decades and agree with results from the tree uprooting monitoring (<92 t km−2 yr−1). In-situ 10Be in soils gave similar denudation rates (58-76 t km−2 yr−1). Meteoric 10Be 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.

Topographic Roughness on Forested Hillslopes: A Theoretical Approach for Quantifying Hillslope Sediment Flux From Tree Throw

“…Tree throw episodically and suddenly creates topographic roughness, inverts the soil column, and has the potential to expose fresh bedrock. Each of these has potential implications to affect hydrologic pathways (Phillips et al., 2017), soil development (Šamonil et al., 2020), chemical weathering, and soil production rates (Gabet & Mudd, 2010). We anticipate that will be a valuable tool that is readily available for quantifying the magnitude and frequency of tree throw and its impact on the Critical Zone.…”

“…Note that Equation is a Gaussian in the ‐direction [L] and a derivative of a Gaussian in the ‐direction [L]. Previous work suggests alternative forms (two anti‐symmetric semi‐spheres) for the initial condition of pit‐mound couplets (Gabet & Mudd, 2010; Gabet et al., 2003; Martin et al., 2013; Šamonil et al., 2020); however, this formulation also approximates natural couplet geometries and is mathematically simple to work with.The form of Equation represents the initial condition of pit‐mound couplets once the tree roots have rotted away (5–10 years after the tree topples in temperate environments (Schaetzl & Follmer, 1990)) so that the couplet may evolve by creep‐like processes. With this definition of the initial condition, the “throw” component involves the tree toppling and the decay of roots, which drops particles and constructs smooth pit‐mound couplets.…”

“…However, identifying the value of for a particular landscape remains a challenge and is a source of uncertainty. There are also estimates of tree throw production rates (Phillips et al., 2017; Šamonil et al., 2020; Schaetzl et al., 1990), but the stochasticity of tree throw over timescales of decades to centuries limits the constraints of .…”

“…Tree throw has been the subject of many field and numerical studies that quantify the sediment flux (Gabet et al., 2003; Hancock & Lowry, 2021; Martin et al., 2013; Phillips et al., 2017; Šamonil et al., 2020) or demonstrate the consequences for weathering and soil production (Gabet & Mudd, 2010; Gallaway et al., 2009; Šamonil et al., 2013). Quantifying the sediment flux due to tree throw typically involves measuring the volumes of sediment attached to uprooted trees and constraining event frequency by either dating material deposited beneath mounds (Šamonil et al., 2013; Schaetzl & Follmer, 1990) or by tree census (Gallaway et al., 2009; Martin et al., 2013; Šamonil et al., 2020). However, tree throw is often caused by rare extreme wind events that impart a drag force on the canopy, which exceed a resisting force of the soil.…”

New estimate of chemical weathering rate in Xijiang River Basin based on multi-model

“…While the research on the chemical weathering intensity of the marine sedimentary carbonate rock formation is relatively few 19 , the actual scenario may be more complex. In addition, chemical weathering is also affected by geomorphological units 20 , 21 . In mountainous environments, different slope orientations have different weathering rates due to the differences in humidity 22 ; glaciers have strong physical and chemical weathering 23 .…”