page_title: Ecosystem Functional Type
section_title: EFTs identification
hierarchical_section_title: Ecosystem Functional Type / EFTs identification
caption_attribution_description: English: Annual curve of spectral vegetation indexes (VI)
context_page_description: Ecosystem Functional Type is a new ecological concept to characterize ecosystem functioning. Ecosystem Functional Types are defined as groups of ecosystems or patches of the land surface that share similar dynamics of matter and energy exchanges between the biota and the physical environment. The EFT concept is analogous to the Plant Functional Types concept, but defined at a higher level of the biological organization. As plant species can be grouped according to common functional characteristics, ecosystems can be grouped according to their common functional behavior.
  One of the most used approaches to implement this concept has been the identification of EFTs from the satellite-derived dynamics of primary production, an essential and integrative descriptor of ecosystem functioning.
context_section_description: The functional classification of EFTs developed by Paruelo et al. (2001) and Alcaraz-Segura et al. (2006, 2013)   uses time series of spectral vegetation indexes to capture the carbon gains dynamics, the most integrative indicator of ecosystem functioning. To build EFTs, these authors derive three descriptors or metrics from the seasonal dynamics (annual curve) of spectral vegetation indexes (VI) that capture most of the variance in the time series (Fig.2): 
  Annual mean of VI (VI_Mean): estimator of annual primary production, one of the most essential and integrative descriptors of ecosystem functioning.
  Intra-annual coefficient of variation of VI (VI_sCV): descriptor of seasonality or differences in carbon gains between the growing and non growing seasons.
  Date of maximum VI value (VI_DMAX): phenological indicator of when in the year does the growing season take place.
  The range of values of each VI metric is divided into four intervals, giving the potential number of 4x4x4=64 EFTs. Each EFT is assigned a code of two letters and a number (three characters). The first letter of the code (capital) corresponds to the VI_Mean level, ranging from A to D for low to high (increasing) VI_Mean or productivity. The second letter (small) shows the seasonal CV, ranging from a to d for high (decreasing) to low VI_sCV or seasonality. The numbers refer to DMAX or phenology and indicate the season of maximum VI (1–4: spring, summer, autumn and winter).
caption: Fig.2: Annual curve of spectral vegetation indexes (VI: Enhanced Vegetation Index (MODIS-EVI)
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