 |
| Titel |
Monitoring of carbon dioxide fluxes in a subalpine grassland ecosystem of the Italian Alps using a multispectral sensor |
| VerfasserIn |
K. Sakowska, L. Vescovo, B. Marcolla, R. Juszczak, J. Olejnik, D. Gianelle |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 17 ; Nr. 11, no. 17 (2014-09-08), S.4695-4712 |
| Datensatznummer |
250117578
|
| Publikation (Nr.) |
 copernicus.org/bg-11-4695-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
| The study investigates the potential of a commercially available proximal
sensing system – based on a 16-band multispectral sensor – for monitoring
mean midday gross ecosystem production (GEPm) in a subalpine grassland
of the Italian Alps equipped with an eddy covariance flux tower. Reflectance
observations were collected for 5 consecutive years, characterized by
different climatic conditions, together with turbulent carbon dioxide fluxes
and their meteorological drivers. Different models based on linear
regression (vegetation indices approach) and on multiple regression
(reflectance approach) were tested to estimateGEPm from optical data.
The overall performance of this relatively low-cost system was positive.
Chlorophyll-related indices including the red-edge part of the spectrum in
their formulation (red-edge normalized difference vegetation
index,
NDVIred-edge; chlorophyll index, CIred-edge) were the best
predictors of GEPm, explaining most of its variability during the
observation period. The use of the reflectance approach did not lead to
considerably improved results in estimating GEPm: the adjusted
R2 (adjR2) of the model based on linear regression – including all
the 5 years – was 0.74, while the adjR2 for the multiple regression
model was 0.79. Incorporating mean midday photosynthetically active
radiation (PARm) into the model resulted in a general decrease in the
accuracy of estimates, highlighting the complexity of the GEPm response to incident radiation. In fact, significantly higher
photosynthesis rates were observed under diffuse as regards direct
radiation conditions. The models which were observed to perform best were
then used to test the potential of optical data for GEPm gap filling.
Artificial gaps of three different lengths (1, 3 and 5 observation days)
were introduced in the GEPm time series. The values of adjR2 for
the three gap-filling scenarios showed that the accuracy of the gap filling
slightly decreased with gap length. However, on average, the GEPm gaps
were filled with an accuracy of 73% with the model fed with
NDVIred-edge, and of 76% with the model using reflectance at 681,
720 and 781 nm and PARm data. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|