Hongxiao Jin
Researcher
First assessment of the plant phenology index (PPI) for estimating gross primary productivity in African semi-arid ecosystems
Author
Summary, in English
The importance of semi-arid ecosystems in the global carbon cycle as sinks for CO
2
emissions has recently been highlighted. Africa is a carbon sink and nearly half its area comprises arid and semi-arid ecosystems. However, there are uncertainties regarding CO
2
fluxes for semi-arid ecosystems in Africa, particularly savannas and dry tropical woodlands. In order to improve on existing remote-sensing based methods for estimating carbon uptake across semi-arid Africa we applied and tested the recently developed plant phenology index (PPI). We developed a PPI-based model estimating gross primary productivity (GPP) that accounts for canopy water stress, and compared it against three other Earth observation-based GPP models: the temperature and greenness (T-G) model, the greenness and radiation (GöR) model and a light use efficiency model (MOD17). The models were evaluated against in situ data from four semi-arid sites in Africa with varying tree canopy cover (3–65%). Evaluation results from the four GPP models showed reasonable agreement with in situ GPP measured from eddy covariance flux towers (EC GPP) based on coefficient of variation (R
2
), root-mean-square error (RMSE), and Bayesian information criterion (BIC). The GöR model produced R
2
= 0.73, RMSE = 1.45 g C m
−2
d
−1
, and BIC = 678; the T-G model produced R
2
= 0.68, RMSE = 1.57 g C m
−2
d
−1
, and BIC = 707; the MOD17 model produced R
2
= 0.49, RMSE = 1.98 g C m
−2
d
−1
, and BIC = 800. The PPI-based GPP model was able to capture the magnitude of EC GPP better than the other tested models (R
2
= 0.77, RMSE = 1.32 g C m
−2
d
−1
, and BIC = 631). These results show that a PPI-based GPP model is a promising tool for the estimation of GPP in the semi-arid ecosystems of Africa.
Department/s
- Dept of Physical Geography and Ecosystem Science
- Centre for Environmental and Climate Science (CEC)
- BECC: Biodiversity and Ecosystem services in a Changing Climate
- MERGE: ModElling the Regional and Global Earth system
Publishing year
2019
Language
English
Pages
249-260
Publication/Series
International Journal of Applied Earth Observation and Geoinformation
Volume
78
Document type
Journal article
Publisher
Elsevier
Topic
- Physical Geography
- Environmental Sciences
- Remote Sensing
Keywords
- Drylands
- Eddy covariance
- Remote sensing
- Earth observation
- Gross primary productivity
- Land surface temperature
- Africa
- Plant phenology index
Status
Published
Project
- Global Savannah Phenology: Integrating Earth Observation, Ecosystem Modeling, and PhenoCams
ISBN/ISSN/Other
- ISSN: 1569-8432