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Estimating terrestrial gross primary productivity in water limited ecosystems across Africa using the Southampton Carbon Flux (SCARF) model

Estimating terrestrial gross primary productivity in water limited ecosystems across Africa using the Southampton Carbon Flux (SCARF) model
Estimating terrestrial gross primary productivity in water limited ecosystems across Africa using the Southampton Carbon Flux (SCARF) model

The amount of carbon uptake by vegetation is an important component to understand the functioning of ecosystem processes and their response/feedback to climate. Recently, a new diagnostic model called the Southampton Carbon Flux (SCARF) Model driven by remote sensing data was developed to predict terrestrial gross primary productivity (GPP) and successfully applied in temperate regions. The model is based on the concept of quantum yield of plants and improves on the previous diagnostic models by (i) using the fraction of photosynthetic active radiation absorbed by the photosynthetic pigment (FAPARps) and (ii) using direct quantum yield by classifying the vegetation into C3 or C4 classes. In this paper, we calibrated and applied the model to evaluate GPP across various ecosystems in Africa. The performance of the model was evaluated using data from seven eddy covariance flux tower sites. Overall, the modelled GPP values showed good correlation (R > 0.59, p < 0.0001) with estimated flux tower GPP at most sites (except at a tropical rainforest site, R = 0.38, p = 0.02) in terms of their seasonality and absolute values. Mean daily GPP across the investigated period varied significantly across sites depending on the vegetation types from a minimum of 0.44 g C m−2 day−1 at the semi-arid and sub-humid savanna grassland sites to a maximum of 9.86 g C m−2 day−1 at the woodland and tropical rain forest sites. Generally, strong correlation is observed in savanna woodlands and grasslands where vegetation follows a prescribed seasonal cycle as determined by changes in canopy chlorophyll content and leaf area index. Finally, the mean annual GPP value for Africa predicted by the model was 35.25 Pg C yr−1. The good performance of the SCARF model in water-limited ecosystems across Africa extends its potential for global application.

C3/C4 photosynthesis, Carbon exchange, Diagnostic model, Gross primary productivity, Photosynthetic quantum yield, Remote sensing
0048-9697
1472-1483
Chiwara, P.
60d3cd5b-4573-422b-922c-d430dfb00dfb
Ogutu, B.O.
4e36f1d2-f417-4274-8f9c-4470d4808746
Dash, J.
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Milton, E.J.
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Ardö, J.
9d2ee0ea-b86b-4100-af77-53d1683c7e14
Saunders, M.
bdbd3b73-bebb-4e39-89ed-f204b31d0612
Nicolini, G.
6744360a-4297-4e2f-853e-5a33560d7bc1
Chiwara, P.
60d3cd5b-4573-422b-922c-d430dfb00dfb
Ogutu, B.O.
4e36f1d2-f417-4274-8f9c-4470d4808746
Dash, J.
51468afb-3d56-4d3a-aace-736b63e9fac8
Milton, E.J.
f6cb5c0d-a5d4-47d7-860f-096de08e0c24
Ardö, J.
9d2ee0ea-b86b-4100-af77-53d1683c7e14
Saunders, M.
bdbd3b73-bebb-4e39-89ed-f204b31d0612
Nicolini, G.
6744360a-4297-4e2f-853e-5a33560d7bc1

Chiwara, P., Ogutu, B.O., Dash, J., Milton, E.J., Ardö, J., Saunders, M. and Nicolini, G. (2018) Estimating terrestrial gross primary productivity in water limited ecosystems across Africa using the Southampton Carbon Flux (SCARF) model. Science of the Total Environment, 630, 1472-1483. (doi:10.1016/j.scitotenv.2018.02.314).

Record type: Article

Abstract

The amount of carbon uptake by vegetation is an important component to understand the functioning of ecosystem processes and their response/feedback to climate. Recently, a new diagnostic model called the Southampton Carbon Flux (SCARF) Model driven by remote sensing data was developed to predict terrestrial gross primary productivity (GPP) and successfully applied in temperate regions. The model is based on the concept of quantum yield of plants and improves on the previous diagnostic models by (i) using the fraction of photosynthetic active radiation absorbed by the photosynthetic pigment (FAPARps) and (ii) using direct quantum yield by classifying the vegetation into C3 or C4 classes. In this paper, we calibrated and applied the model to evaluate GPP across various ecosystems in Africa. The performance of the model was evaluated using data from seven eddy covariance flux tower sites. Overall, the modelled GPP values showed good correlation (R > 0.59, p < 0.0001) with estimated flux tower GPP at most sites (except at a tropical rainforest site, R = 0.38, p = 0.02) in terms of their seasonality and absolute values. Mean daily GPP across the investigated period varied significantly across sites depending on the vegetation types from a minimum of 0.44 g C m−2 day−1 at the semi-arid and sub-humid savanna grassland sites to a maximum of 9.86 g C m−2 day−1 at the woodland and tropical rain forest sites. Generally, strong correlation is observed in savanna woodlands and grasslands where vegetation follows a prescribed seasonal cycle as determined by changes in canopy chlorophyll content and leaf area index. Finally, the mean annual GPP value for Africa predicted by the model was 35.25 Pg C yr−1. The good performance of the SCARF model in water-limited ecosystems across Africa extends its potential for global application.

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Estimation_Carbon_Africa - Accepted Manuscript
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More information

Accepted/In Press date: 26 February 2018
e-pub ahead of print date: 7 March 2018
Published date: 15 July 2018
Keywords: C3/C4 photosynthesis, Carbon exchange, Diagnostic model, Gross primary productivity, Photosynthetic quantum yield, Remote sensing

Identifiers

Local EPrints ID: 418727
URI: http://eprints.soton.ac.uk/id/eprint/418727
ISSN: 0048-9697
PURE UUID: 695bc2a3-c710-465e-9b91-bec441ed750c
ORCID for B.O. Ogutu: ORCID iD orcid.org/0000-0002-1804-6205
ORCID for J. Dash: ORCID iD orcid.org/0000-0002-5444-2109

Catalogue record

Date deposited: 20 Mar 2018 17:30
Last modified: 18 Feb 2021 17:12

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