Modelling Gas Exchange and Biomass Production in West African Sahelian and Sudanian Ecological Zones

DOI

West African Sahelian and Sudanian ecosystems are providing essential services to people and also play a significant role within the global carbon cycle. However, climate and land use are dynamically changing and it remains uncertain how these changes will affect the potential of these regions for providing food and fodder resources or the biosphere-atmosphere exchange of CO2. In this study, we investigate the capacity of a process-based biogeochemical model, LandscapeDNDC, to simulate net ecosystem exchange (NEE) and aboveground biomass of typical managed and natural Sahelian and Sudanian savanna ecosystems. We tested the model for various sites with different proportions of trees and grasses, as well as for the most typical arable cropping systems of the region. In order to describe the phenological development with a common parameterization across all ecosystem types, we introduced soil-water availability in addition to temperature as a driver as seasonal soil water-shortage is a common feature for all these systems. The new approach was tested by using a sample of sites (calibration sites) that provided NEE from flux tower observations and leaf area index data from satellite images (MODIS). For assessing the simulation accuracy, we applied the calibrated model to 42 additional sites (validation sites) across West Africa for which measured aboveground biomass data were available. The model showed a good performance regarding simulated biomass development. Overall, the comparison of simulated and observed biomass at sites with a dominating land cover of crops, grass or trees yielded correlation coefficients of 0.82, 0.94, and 0.77 and the Root Mean Square Error of 0.15, 0.22, and 0.12 kg m−2, respectively. In absolute terms, the model results indicate above-ground carbon stocks up to 1733, 3291, and 5377 kg C ha−1 yr−1 for agricultural, savanna grasslands, and savanna mixed tree-grassland sites. Carbon stocks as well as exchange rates correlated in particular with the abundance of trees. The simulations indicate higher grass biomass and crop yields under more humid climatic conditions as can be found in the Sudanian savanna region. Our study shows the capability of LandscapeDNDC to accurately simulate carbon balances in natural and agricultural ecosystems in semi-arid West Africa under a wide range of conditions, so that it might be used to assess the impact of land-use and climate change on the regional biomass productivity.

The authors are thankful to the UPSCALERS project (AURG II-1-074-2016) which is part of the African Union Research Grants financed through the Agreement between the European Commission and the African Union Commission (DCI-PANAF/2015/307-078), to the EU-Aid funded project CASSECS, and to the AMMA-CATCH observatory (http://www.amma-catch.org/?lang=en) that all supplied basic data. Special funding was supplied by the Swedish National Space Agency (SNSA). Furthermore, part of the climate data was obtained from the NASA Langley Research Center (LaRC) POWER Project funded through the NASA Earth Science/Applied Science Program.

Identifier
DOI https://doi.org/10.35097/437
Related Identifier https://doi.org/10.5194/gmd-2020-417
Metadata Access https://www.radar-service.eu/oai/OAIHandler?verb=GetRecord&metadataPrefix=datacite&identifier=10.35097/437
Provenance
Creator Rahimi, Jaber (Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany); Ago, Expedit Evariste (Laboratoire d’Ecologie Appliquée, Faculté des Sciences Agronomiques, Université d’Abomey-Calavi, Cotonou, Bénin); Ayantunde, Augustine (International Livestock Research Institute (ILRI), Ouagadougou, Burkina Faso); Bogaert, Jan (Biodiversity and Landscape Unit, Université de Liège Gembloux Agro-Bio Tech, Gembloux, Belgium); Butterbach-Bahl, Klaus (Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany); Cappelaere, Bernard (HydroSciences Montpellier, Univ. Montpellier, IRD, CNRS, Montpellier, France); Demarty, Jérôme (HydroSciences Montpellier, Univ. Montpellier, IRD, CNRS, Montpellier, France); Diouf, Abdoul Aziz (Centre de Suivi Ecologique (CSE), Dakar, Senegal); Falk, Ulrike (Satellite-based Climate Monitoring, Deutscher Wetterdienst (DWD), Offenbach, Germany); Haas, Edwin (Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany); Hiernaux, Pierre (Géosciences Environnement Toulouse (GET), CNRS, IRD, UPS, Toulouse, France); Kraus, David (Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany); Roupsard, Olivier (CIRAD, UMR Eco&Sols, BP1386, CP18524, Dakar, Senegal); Scheer, Clemens (Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany); Srivastava, Amit Kumar (Institute of Crop Science and Resource Conservation, University of Bonn, Bonn, Germany); Tagesson, Torbern (Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark); Grote, Rüdiger (Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany)
Publisher Karlsruhe Institute of Technology (KIT)
Contributor RADAR
Publication Year 2021
Funding Reference African Union Research Grant, AURG II 1 074 2016
Rights CC BY-ND 4.0 Attribution-NoDerivs
OpenAccess true
Representation
Language English
Resource Type Dataset
Format application/zip
Discipline Biospheric Sciences; Ecology; Geosciences; Natural Sciences