Phenology of the natural vegetation: A land cover specific approach for a reference dataset in Central Africa

In order to study anomalies and trends of the land surface phenology for different vegetation types in the world and more specifically in tropical regions, the design of a phenological reference dataset is investigated. The main objective is to get a description of the seasonal behaviour and interannual variations in order to study anomalies and potential trends of the vegetation. The work was based on time series acquired during the last 10 years by the SPOT VEGETATION sensor with a 1km spatial resolution. The NDVI was used as an indicator of the vegetation growing cycle. Daily surface reflectance values were composited into decades to reduce clouds and haze effects, using the mean compositing algorithm. The decadal NDVI values were spatially averaged for each pixels belonging to a similar vegetation type and temporally for the 10 years of data. The result is a smooth profile representing the seasonal reference pattern as well as the interannual variability inherent to a specific vegetation type.