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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 9 | Copyright
Biogeosciences, 15, 2723-2742, 2018
https://doi.org/10.5194/bg-15-2723-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 07 May 2018

Research article | 07 May 2018

Remote sensing of canopy nitrogen at regional scale in Mediterranean forests using the spaceborne MERIS Terrestrial Chlorophyll Index

Yasmina Loozen1, Karin T. Rebel1, Derek Karssenberg2, Martin J. Wassen1, Jordi Sardans3,4, Josep Peñuelas3,4, and Steven M. De Jong2 Yasmina Loozen et al.
  • 1Copernicus Institute of sustainable development, Faculty of Geosciences, Utrecht University, Utrecht, the Netherlands
  • 2Physiscal geography, Faculty of Geosciences, Utrecht University, Utrecht, the Netherlands
  • 3CSIC, Global Ecology Unit CREAF-CSIC-UAB, Bellaterra, Catalonia, Spain
  • 4CREAF, Cerdanyola del Vallès, Catalonia, Spain

Abstract. Canopy nitrogen (N) concentration and content are linked to several vegetation processes. Therefore, canopy N concentration is a state variable in global vegetation models with coupled carbon (C) and N cycles. While there are ample C data available to constrain the models, widespread N data are lacking. Remotely sensed vegetation indices have been used to detect canopy N concentration and canopy N content at the local scale in grasslands and forests. Vegetation indices could be a valuable tool to detect canopy N concentration and canopy N content at larger scale. In this paper, we conducted a regional case-study analysis to investigate the relationship between the Medium Resolution Imaging Spectrometer (MERIS) Terrestrial Chlorophyll Index (MTCI) time series from European Space Agency (ESA) Envisat satellite at 1km spatial resolution and both canopy N concentration (%N) and canopy N content (Ngm−2, of ground area) from a Mediterranean forest inventory in the region of Catalonia, in the northeast of Spain. The relationships between the datasets were studied after resampling both datasets to lower spatial resolutions (20, 15, 10 and 5km) and at the original spatial resolution of 1km. The results at higher spatial resolution (1km) yielded significant log–linear relationships between MTCI and both canopy N concentration and content: r2 = 0.32 and r2 = 0.17, respectively. We also investigated these relationships per plant functional type. While the relationship between MTCI and canopy N concentration was strongest for deciduous broadleaf and mixed plots (r2 = 0.24 and r2 = 0.44, respectively), the relationship between MTCI and canopy N content was strongest for evergreen needleleaf trees (r2 = 0.19). At the species level, canopy N concentration was strongly related to MTCI for European beech plots (r2 = 0.69). These results present a new perspective on the application of MTCI time series for canopy N detection.

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Nitrogen (N) is an essential nutrient for plant growth. It would be interesting to detect it using satellite data. The goal was to investigate if it is possible to remotely sense the canopy nitrogen concentration and content of Mediterranean trees using a product calculated from satellite reflectance data, the MERIS Terrestrial Chlorophyll Index (MTCI). The tree plots were located in Catalonia, NE Spain. The relationship between MTCI and canopy N was present but dependent on the type of trees.
Nitrogen (N) is an essential nutrient for plant growth. It would be interesting to detect it...
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