Nutrient limitation reduces land carbon uptake in simulations with a model of combined carbon, nitrogen and phosphorus cycling 1International Max Planck Research School on Earth-System Modelling, Hamburg, Germany
06 Sep 2012
2Max Planck Institute for Meteorology, Hamburg, Germany
3Max Planck Institute for Biogeochemistry, Jena, Germany
4Department of Forest Resources, University of Minnesota, St. Paul, Minnesota, USA
5Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, Australia
6Department of Systems Ecology, Vrije Universiteit, Amsterdam, The Netherlands
7Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Tartu, Estonia
*now at: Institute of the Environment and Sustainability, University of California, Los Angeles, USA
Received: 07 December 2011 – Published in Biogeosciences Discuss.: 16 March 2012 Abstract. Terrestrial carbon (C) cycle models applied for climate projections simulate
a strong increase in net primary productivity (NPP) due to elevated
atmospheric CO2 concentration during the 21st century.
These models usually neglect the limited availability of nitrogen (N) and
phosphorus (P), nutrients that commonly limit plant growth and soil carbon
turnover. To investigate how the projected C sequestration is altered when
stoichiometric constraints on C cycling are considered, we incorporated a P
cycle into the land surface model JSBACH (Jena Scheme for Biosphere–Atmosphere Coupling in Hamburg), which already includes
representations of coupled C and N cycles.
Revised: 10 July 2012 – Accepted: 26 July 2012 – Published: 06 September 2012
The model reveals a distinct geographic pattern of P and N limitation. Under
the SRES (Special Report on Emissions Scenarios) A1B scenario, the accumulated land C uptake between 1860 and 2100 is
13% (particularly at high latitudes) and 16% (particularly at low
latitudes) lower in simulations with N and P cycling, respectively, than in
simulations without nutrient cycles. The combined effect of both nutrients
reduces land C uptake by 25% compared to simulations without N or P cycling.
Nutrient limitation in general may be biased by the model simplicity, but
the ranking of limitations is robust against the parameterization and the inflexibility of stoichiometry.
After 2100, increased temperature and high CO2
concentration cause a shift from N to P limitation at high latitudes, while
nutrient limitation in the tropics declines. The increase in P limitation at
high-latitudes is induced by a strong increase in NPP and the low P sorption
capacity of soils, while a decline in tropical NPP due to high autotrophic
respiration rates alleviates N and P limitations.
The quantification of P limitation remains challenging.
The poorly constrained processes of soil P sorption and biochemical mineralization
are identified as the main uncertainties in the strength of P limitation.
Even so, our findings indicate that
global land C uptake in the 21st century is likely overestimated
in models that neglect P and N limitations. In the long term, insufficient P
availability might become an important constraint on C cycling at high
latitudes. Accordingly, we argue that the P cycle must be included in global
models used for C cycle projections.
Citation: Goll, D. S., Brovkin, V., Parida, B. R., Reick, C. H., Kattge, J., Reich, P. B., van Bodegom, P. M., and Niinemets, Ü.: Nutrient limitation reduces land carbon uptake in simulations with a model of combined carbon, nitrogen and phosphorus cycling, Biogeosciences, 9, 3547-3569, doi:10.5194/bg-9-3547-2012, 2012.