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Soil geochemistry as a major driver of carbon allocation, stocks and dynamics in vegetation and soils of African tropical forests

Authors:

Abstract

The net primary productivity (NPP) of tropical forests is an important component of the global terrestrial carbon (C) cycle. The lack of field-based data, however, limits our mechanistic understanding of the drivers of NPP and C allocation. In consequence, the role of local edaphic factors for forest growth and C dynamics is unclear and introduces substantial uncertainty in estimating ecosystem C stock accrual. Here, we present data from field measurements on standing biomass as well as leaf, wood, and root production collected along topographic and geochemical gradients in old-growth African tropical mountain forests in the East African Rift System. We show that forests converge towards nutrient uptake more strongly when soil properties and parent material geochemistry indicate fertility constraints due to low amounts of rock-derived nutrients. In contrast, topography did not constrain the variability in C allocation and NPP fluxes. In consequence, aboveground:belowground biomass ratios and total NPP can differ greatly between geochemical regions for similar old-growth tropical forest types. Furthermore, soil organic carbon (SOC) stocks were not related to NPP C allocation and plant C input seemingly exceeding the maximum potential of these soils to stabilize C. We conclude that even after many millennia of weathering and the presence of deeply developed soils, tropical above and belowground C allocation, as well as soil C stocks, vary substantially due to the geochemical properties which soils inherit from parent material. Powered by TCPDF (www.tcpdf.org)
EGU22-2938
https://doi.org/10.5194/egusphere-egu22-2938
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.
Soil geochemistry as a major driver of carbon allocation, stocks and
dynamics in vegetation and soils of African tropical forests
Sebastian Doetterl1,2, Benjamin Bukombe2, Marijn Bauters3, Pascal Boeckx3, Landry Cizungu4,
Matthew Cooper1, Peter Fiener2, Laurent Kidinda5, Isaac Makelele4, Daniel Muhindo4, Boris
Rewald6, and Kris Verheyen3
1Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland (sdoetterl@usys.ethz.ch)
2Institute of Geography, Augsburg University, Augsburg, Germany
3Department of Environment, Ghent University, Gent, Belgium
4Faculty of Agricultural Sciences, Université Catholique de Bukavu, Bukavu, DR Congo
5Institute of Soil Science and Site Ecology, Technische Universität Dresden, Tharandt,
6Institute of Forest Ecology, University of Natural Resources and Life Sciences (BOKU), Vienna, Austria
The net primary productivity (NPP) of tropical forests is an important component of the global
terrestrial carbon (C) cycle. The lack of field-based data, however, limits our mechanistic
understanding of the drivers of NPP and C allocation. In consequence, the role of local edaphic
factors for forest growth and C dynamics is unclear and introduces substantial uncertainty in
estimating ecosystem C stock accrual. Here, we present data from field measurements on
standing biomass as well as leaf, wood, and root production collected along topographic and
geochemical gradients in old-growth African tropical mountain forests in the East African Rift
System. We show that forests converge towards nutrient uptake more strongly when soil
properties and parent material geochemistry indicate fertility constraints due to low amounts of
rock-derived nutrients. In contrast, topography did not constrain the variability in C allocation and
NPP fluxes. In consequence, aboveground:belowground biomass ratios and total NPP can differ
greatly between geochemical regions for similar old-growth tropical forest types. Furthermore, soil
organic carbon (SOC) stocks were not related to NPP C allocation and plant C input seemingly
exceeding the maximum potential of these soils to stabilize C. We conclude that even after many
millennia of weathering and the presence of deeply developed soils, tropical above and
belowground C allocation, as well as soil C stocks, vary substantially due to the geochemical
properties which soils inherit from parent material.
Powered by TCPDF (www.tcpdf.org)
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