A multi-temporal analysis of vegetation dynamics in the Iberian peninsula using MODIS-NDVI data
Ana Pérez-Hoyos, Beatriz Martínez, María Amparo Gilabert, and Francisco Javier García-Haro
The aim of this study is to characterise
the vegetation dynamics of the Iberian Peninsula using MODIS-NDVI time series
(2000-2008) at 1 km resolution. For this purpose, NDVI profiles are analysed
using filtered data derived from a spectral technique, a multi-resolution
analysis (MRA) based on the wavelet transform (WT). The
MRA results in an additive decomposition of the time series into several
components associated with variations on a particular temporal scale. First,
the functional diversity of the Iberian Peninsula is described by using several
metrics derived from the first component of the MRA (filtered time series).
Second, a trend analysis is performed with the fifth component of the MRA
having a semi-period around a year (inter-annual component) in order to detect
potential vegetation changes over the considered period. The 3-month scale Standard
Precipitation Index (SPI-3) was used to better identify changes. As a
result of the functional diversity a characterisation of the Ecosystem Function
Types (EFT) of the Iberian Peninsula with 30 representative classes is obtained. The EFT
present a decreasing northwest to southeast biomass gradient.
An exploratory analysis with the CORINE land cover classification revealed the importance
of land cover in explaining the functioning of particular ecosystems,
particularly for ecosystems showing a strong seasonal dynamics, such as rice
and non-irrigated crops. Finally, the trend analysis indicates that most
vegetation changes over the considered period are due to forest fires and are connected
to the SPI trend.