Normally primary production is estimated by using eddy covariance based light use efficiency models. From the satellite data, vegetation index is used as a proxy to fraction of absorbed photosynthetic active radiation. I have developed my own vegetation index and now I have to find its usefulness in the ecosystem exchange processes. Can any expert in the field of primary production guide me how to start estimation the easiest process in the family of ecosystem exchange by combining EC and remote sensing data?
Regards,
Towers measure NEE. Vegetation indices are more related to GPP. Calibrating a satellite GPP estimate with a flux tower requires a model for respiration. This can be done, but ecosystems have more spatial variability than is captured in either ecosystem models or flux tower networks. You can always get flux estimates via this path, but they may or may not be useful. It is important to have data reserved for a cross-validation effort. I'll attach a couple paper from my group that work in this direction.
Article Evaluating terrestrial CO2 flux diagnoses and uncertainties ...
Article Uncertainty in model parameters and regional carbon fluxes: ...
Dear Prof. Davis,
I am very grateful to you for commenting on my question and sending me very informative papers. I hope these papers will be very helpful for me to understand CO2 flux estimates and finding my own research direction. your comments helped me a lot to get rid of some confusions.
Regards,
MODIS GPP is a good remotely-sensed product. It had be validated against a large number of towers covering most of the vegetation types. In water-limited periods and drought events the discrepancies between EC and satellite may be large.
Dear Prof. Serge Rambal,
Receiving your comment on my question gave me an honor as you are the legend in this field. My labmate told me that MODIS GPP was developed (may be by Running) a long time ago. So, it is not as robust as other models are. But it is reasonable to use it for comparing with one's own GPP model. As this area is new for me, so I wish to assess the usefulness of vegetation index (UNVI, developed by our group, and TCT) for estimating GPP in comparison with MODIS GPP. Do you think this approach is right?
Regards,
Dear Muhammad,
Another option is using sap flow data, which is available in many forest sites.
Please see attached more information on that.
Sincerely,
Tamir
Article Association between sap flow-derived and eddy covariance-der...
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