Webbläsaren som du använder stöds inte av denna webbplats. Alla versioner av Internet Explorer stöds inte längre, av oss eller Microsoft (läs mer här: * https://www.microsoft.com/en-us/microsoft-365/windows/end-of-ie-support).

Var god och använd en modern webbläsare för att ta del av denna webbplats, som t.ex. nyaste versioner av Edge, Chrome, Firefox eller Safari osv.

Default user image.

Lars Eklundh

Professor

Default user image.

Modeling GPP in the Nordic forest landscape with MODIS time series data - comparison with the MODIS GPP product

Författare

  • Per Schubert
  • Fredrik Lagergren
  • Mika Aurela
  • Torben Christensen
  • Achim Grelle
  • Michal Heliasz
  • Leif Klemedtsson
  • Anders Lindroth
  • Kim Pilegaard
  • Timo Vesala
  • Lars Eklundh
Visa allt

Summary, in English

Satellite sensor-derived data are suitable for regional estimations of several important biophysical variables. Data with a finer spatial resolution should improve regional estimations of GPP (gross primary productivity), since they better capture the variation in a heterogeneous landscape. The main objective of this study was to investigate if MODIS 500 m reflectance data can be used to drive empirical models for regional estimations of GPP in Nordic forests. The performance of the proposed models was compared with the MODIS 1 km GPP product. Linear regression analyses were made on 8-day averages of eddy covariance GPP from three deciduous and ten coniferous sites in relation to MODIS 8-day composite data and 8-day averages of modeled incoming PPFD (photosynthetic photon flux density). Time series of EVI2 (two-band enhanced vegetation index) were calculated from MODIS 500 m reflectance data and smoothed by a curve fitting procedure. For most sites, GPP was fairly strongly to strongly related to the product of EVI2 and PPFD (Deciduous: R2 = 0.45–0.86, Coniferous: R2 = 0.49–0.90). Similar strengths were found between GPP and the product of EVI2 and MODIS 1 km daytime LST (land surface temperature) (R2 = 0.55–0.81, 0.57–0.77) and between GPP and EVI2, PPFD and daytime LST in multiple linear regressions (R2 = 0.73–0.89, 0.65–0.93). One year of data was collected from all coniferous sites to derive a general empirical model for GPP versus (1) the product of EVI2 and PPFD (R2 = 0.70), (2) the product of EVI2 and daytime LST (R2 = 0.62) and (3) EVI2, PPFD and daytime LST (R2 = 0.72). These three models were then validated at six sites for the remaining years by linearly relating eddy covariance GPP to modeled GPP, which resulted in fairly strong to strong relationships for most sites (R2 = 0.49–0.91, RMSE = 0.63–1.22 g C m− 2 day− 1, R2 = 0.53–0.73, RMSE = 0.90–1.43 g C m− 2 day− 1, R2 = 0.56–0.87, RMSE = 0.79–1.11 g C m− 2 day− 1). In comparison, similar validation strengths were found for the latest collection 5.1 of the MODIS 1 km GPP product (R2 = 0.59–0.88, RMSE = 0.80–1.16 g C m− 2 day− 1). The main conclusion is that the suggested empirical models driven by MODIS 500 m reflectance data can be used for regional estimations of Nordic forest GPP, while preserving a finer resolution than the MODIS 1 km GPP product.

Avdelning/ar

  • Institutionen för naturgeografi och ekosystemvetenskap
  • eSSENCE: The e-Science Collaboration
  • MERGE: ModElling the Regional and Global Earth system

Publiceringsår

2012

Språk

Engelska

Sidor

136-147

Publikation/Tidskrift/Serie

Remote Sensing of Environment

Volym

126

Dokumenttyp

Artikel i tidskrift

Förlag

Elsevier

Ämne

  • Physical Geography

Nyckelord

  • Moderate Resolution Imaging Spectroradiometer (MODIS)
  • Light use efficiency (ε)
  • Land surface temperature (LST)
  • Gross primary productivity (GPP)
  • Two-band enhanced vegetation index (EVI2)

Aktiv

Published

ISBN/ISSN/Övrigt

  • ISSN: 0034-4257