Modis EVI, NDVI, WDRVI, daily and composite: Looking for the best choice to estimate phenological parameters from deciduous forests

Surveying forest phenology through time helps evaluating climate change effects on ecosystems; Vegetation Indices (VIs) time series (TS) from MODIS imagery are key instruments to this. The objective of this work was to find the best combination of VI and MODIS data to estimate starting of season (SOS) dates on broad-leaved, temperate forests. We generated TS of EVI and NDVI and four WDRVI implementations using daily reflectances from MOD09GQ/MOD09GA products and 16-day composite VIs from the MOD13Q1 dataset from 2001 through 2012. MODIS-based SOS estimations were compared with phenological ground observations from the 50 broad-leaved plots of the RENECOFOR French forest network. Results showed that the use of composite TS led to estimations as good as daily TS. EVI, NDVI and, sometimes, WDRVI_0.20, were the best estimators of advanced SOS; moreover, SOS best matched ground observations respective to EOS in all comparisons.