Abstract
The aim of the development of a forest soil carbon simulation model was to demonstrate the slow, but yet dynamic character of the forest soil C balance. We explored the sensitivity of total forest soil carbon stocks (forest floor + 0-100 cm) to litter inputs, tree root litter distributions, and iterated turnover rates in horizontal fixed depth soil sections to 1 meter depth. The intended use is mainly for outlier detection in resampling studies and teaching soil C dynamics. The simulation utilized repeated measurements of soil C (SINKS 2007-12) and will be validated with new data collected during the SINKS2 project (SINKS2 2014-2021). The horizontal layering of the model followed the sampling design of soils in the Danish forest soil inventory including the infrastructures of the National Forest Inventory and the Nitrate Monitoring Grid. Two important pedological processes in mineral forest soils, bioturbation by macrofauna (earthworms) and podzolisation were included, allowing transfer of SOC between the forest floor and mineral soil layers.
The forest soil carbon simulator incorporates all types of new and old organic matter into one pool. It is organized in six horizontal soil layers and runs for 40 years. The simulation is made in an Excel spreadsheet. Inputs to the spreadsheet are initial soil carbon content, annual aboveground litterfall, and root litter distribution to the six horizontal layers, and decomposition rates. Furthermore, the fraction of litter translocated by earthworms to mineral soil horizons and the fraction of the organic horizon that is translocated to spodic material in a B-horizon is to be chosen from a range of values. Four cases were selected in that reflect common forested soil types in Denmark. In the four selected cases turnover rates (k, year-1) were adjusted manually in the spreadsheet to fit observed change (18 years between 1990 and 2008-10) in C concentration in each of the six layers. The cases represent classes of subsoil texture and topsoil carbon content from the SINKS resampling study (1990 and 2008-10). The sensitivity of SOC stocks to the uncertainty of 1) the turnover rate of soil organic matter, 2) aboveground litter inputs, 3) root litter distribution, and 4) the earthworm effect was evaluated.
The simulated changes for typical combinations of subsoil texture class and initial soil carbon content may be compared with observed changes in the NFI and KN soil monitoring network when the next sampling period is finalized in 2021.
The forest soil carbon simulator incorporates all types of new and old organic matter into one pool. It is organized in six horizontal soil layers and runs for 40 years. The simulation is made in an Excel spreadsheet. Inputs to the spreadsheet are initial soil carbon content, annual aboveground litterfall, and root litter distribution to the six horizontal layers, and decomposition rates. Furthermore, the fraction of litter translocated by earthworms to mineral soil horizons and the fraction of the organic horizon that is translocated to spodic material in a B-horizon is to be chosen from a range of values. Four cases were selected in that reflect common forested soil types in Denmark. In the four selected cases turnover rates (k, year-1) were adjusted manually in the spreadsheet to fit observed change (18 years between 1990 and 2008-10) in C concentration in each of the six layers. The cases represent classes of subsoil texture and topsoil carbon content from the SINKS resampling study (1990 and 2008-10). The sensitivity of SOC stocks to the uncertainty of 1) the turnover rate of soil organic matter, 2) aboveground litter inputs, 3) root litter distribution, and 4) the earthworm effect was evaluated.
The simulated changes for typical combinations of subsoil texture class and initial soil carbon content may be compared with observed changes in the NFI and KN soil monitoring network when the next sampling period is finalized in 2021.
| Original language | English |
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| Publisher | Department of Geosciences and Natural Resource Management, University of Copenhagen |
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| Number of pages | 42 |
| ISBN (Electronic) | 978-87-7903-749-6 |
| Publication status | Published - 2016 |
| Series | IGN Report |
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