@article{fdi:010069406,
  title = {{M}odelling spatial and temporal dynamics of gross primary production in the {S}ahel from earth-observation-based photosynthetic capacity and quantum efficiency},
  author = {{T}agesson, {T}. and {A}rdo, {J}. and {C}appelaere, {B}ernard and {K}ergoat, {L}. and {A}bdi, {A}. and {H}orion, {S}. and {F}ensholt, {R}.},
  editor = {},
  language = {{ENG}},
  abstract = {{I}t has been shown that vegetation growth in semiarid regions is important to the global terrestrial {CO}2 sink, which indicates the strong need for improved understanding and spatially explicit estimates of {CO}2 uptake (gross primary production; {GPP}) in semi-arid ecosystems. {T}his study has three aims: (1) to evaluate the {MOD}17{A}2{H} {GPP} (collection 6) product against {GPP} based on eddy covariance ({EC}) for six sites across the {S}ahel; (2) to characterize relationships between spatial and temporal variability in {EC}-based photosynthetic capacity ({F}-opt) and quantum efficiency (alpha) and vegetation indices based on earth observation ({EO}) (normalized difference vegetation index ({NDVI}), renormalized difference vegetation index ({RDVI}), enhanced vegetation index ({EVI}) and shortwave infrared water stress index ({SIWSI})); and (3) to study the applicability of {EO} upscaled {F}-opt and alpha for {GPP} modelling purposes. {MOD}17{A}2{H} {GPP} (collection 6) drastically underestimated {GPP}, most likely because maximum light use efficiency is set too low for semi-arid ecosystems in the {MODIS} algorithm. {I}ntra-annual dynamics in {F}-opt were closely related to {SIWSI} being sensitive to equivalent water thickness, whereas alpha was closely related to {RDVI} being affected by chlorophyll abundance. {S}patial and inter-annual dynamics in {F}-opt and alpha were closely coupled to {NDVI} and {RDVI}, respectively. {M}odelled {GPP} based on {F}-opt and alpha upscaled using {EO}-based indices reproduced in situ {GPP} well for all except a cropped site that was strongly im-pacted by anthropogenic land use. {U}pscaled {GPP} for the {S}ahel 2001-2014 was 736 +/- 39 g{C}m(-2) yr(-1). {T}his study indicates the strong applicability of {EO} as a tool for spatially explicit estimates of {GPP}, {F}-opt and alpha; incorporating {EO}-based {F}-opt and alpha in dynamic global vegetation models could improve estimates of vegetation production and simulations of ecosystem processes and hydro-biochemical cycles.},
  keywords = {{SAHEL} ; {ZONE} {SEMIARIDE}},
  booktitle = {},
  journal = {{B}iogeosciences},
  volume = {14},
  numero = {5},
  pages = {1333--1348},
  ISSN = {1726-4170},
  year = {2017},
  DOI = {10.5194/bg-14-1333-2017},
  URL = {https://www.documentation.ird.fr/hor/fdi:010069406},
}