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Studies into the effect of soil type and soil layer on the in-ground decay of European beech
2022 - IRG/WP 22-20681
In this study, European beech (Fagus sylvatica L.) specimens were exposed to three different soil types; Podsol (Podzol), Braunerde (Cambisol), and Pararendzina (Regosol), in adapted terrestrial microcosm (TMC) tests according to CEN/TS 15083-2 (2005). Soils were sampled (250 mm deep) from field sites and separated into their constituent layers to deliver three TMC setups; mineral soil layer only (“M”), mineral and organic layers (“OM”), and mineral, organic and litter layers (“LOM”), to identify the effect of each respective soil layer on wood decay. Wood specimens (5 x 10 x 100 mm³) were measured for oven-dry mass loss (MLwood) after 16 weeks of exposure, and compared to MLwood predicted using a dose-response laboratory in-ground decay model developed by Marais et al. (2021) for European beech. To deliver predicted MLwood after 16 weeks of exposure, input variables included soil water-holding capacity (WHCsoil) and soil moisture content (MCsoil) of the sampled soils’ mineral layer, as well as soil temperature (Tsoil) and exposure time. The MCsoil of TMCs were set to 95 % of the mineral soil layers’ WHCsoil. The non-parametric Wilcoxon rank-sum test was used to compare medians between groups of measured and predicted MLwood. Simple modifying factors to account for the significant differences in MLwood groups were developed and the use of which subsequently illustrated. Overall, Podsol soils delivered the highest mean measured MLwood, while Braunerde soils the lowest. Braunerde in “M” was the only group to not register a significant difference between measured and predicted MLwood groups. Soil temperature and moisture conditions still played a dominant role in the resulting wood decay, however the need for a variable describing an additional soil property was shown. The study suggests further investigation into the development of modifying factors for different soil types, where the effect of moisture- and temperature-induced components alone cannot reliably predict wood decay in soils differing from a reference, like those used in laboratory-based TMC studies.
B N Marais, S Kovacs, M Jansen, C Brischke