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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2018-421
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2018-421
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 24 Oct 2018

Submitted as: research article | 24 Oct 2018

Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Biogeosciences (BG) and is expected to appear here in due course.

Response of Net Primary Productivity of Zambezi teak forests to climate change along a rainfall gradient in Zambia

Justine Ngoma1,2, Maarten C. Braakhekke4, Bart Kruijt2, Eddy Moors4,6, Iwan Supit2, James H. Speer3, Royd Vinya1, and Rik Leemans5 Justine Ngoma et al.
  • 1School of Natural Resources, The Copperbelt University, P.O. Box 21692, Kitwe, Zambia
  • 2Water Systems and Global Change Group, Wageningen University and Research, P.O. Box 47, 6700AA Wageningen, The Netherlands
  • 3Department of Earth and Environmental Systems, Indiana State University, Terre Haute, Indiana, 47809 USA
  • 4VU University Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
  • 5Environmental Systems Analysis Group, Wageningen University and Research, P.O. Box 47, 6700AA Wageningen, The Netherlands
  • 6IHE Delft Institute for Water Education, P.O. Box 3015, 2601 DA Delft, The Netherlands

Abstract. Understanding climate change effects on forests is important considering the role forests play in mitigating climate change. We studied the effects of changes in temperature, rainfall, atmospheric carbon dioxide (CO2) concentration, solar radiation, and number of wet days (as a measure of rainfall intensity) on net primary productivity (NPP) of the Zambian Zambezi teak forests along a rainfall gradient. Using 1960–1989 as base-line, we projected changes in NPP for the end of the 21st century (2070–2099). We adapted the parameters of the dynamic vegetation model, LPJ-GUESS, to simulate the growth of Zambian forests at three sites along a moisture gradient receiving annual rainfall of between 700 mm to more than 1000 mm. The thus adjusted plant functional type was tested against measured data. We forced the model with contemporary climate data (1960–2005) and with climatic forecasts of an ensemble of five General Circulation Models (GCMs) following RCP4.5 and RCP8.5. We used local soil parameter values to characterize texture and measured local tree parameter values for maximum crown area, wood density, leaf longevity, and allometry. While increased CO2 concentration enhances NPP at the wetter Kabompo and the intermediate Namwala sites, NPP decreases at the drier Sesheke site under both scenarios by the end of 21st century. The projected decreased NPP under RCP8.5 at the Sesheke site results from the reduced rainfall. We thus demonstrated that differences in rainfall pattern influence the way in which climate change will affect forests resources. We also showed that using local parameter values is essential to obtaining reasonably reliable simulations.

Justine Ngoma et al.
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Interactive discussion
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Justine Ngoma et al.
Justine Ngoma et al.
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Short summary
The Zambezi teak forests are a source of raw material for the timber industry. Through the application of LPJ-GUESS vegetation model, we determined the forests' response to climate change at the wetter Kabompo, drier Sesheke, and the intermediate Namwala sites in Zambia. While increased CO2 concentration enhances forests' productivity at Kabompo and Namwala, the decreased rainfall will reduce forests' productivity at Sesheke by the year 2099 resulting in reduced raw material for saw millers.
The Zambezi teak forests are a source of raw material for the timber industry. Through the...
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