GROUND OBSERVATION OF WALNUT PHENOLOGY FOR VALIDATION OF MODIS/NDVI IN MONITORING DECIDUOUS FOREST PHENOLOGY

摘要

Phenology of deciduous broadleaf forest from periodical MODIS/NDVI images was validated with the ground observed phenology of walnut trees (Juglans mandshurica Maxim.) at different altitude levels. Thirteen walnut trees were selected between 583m and 1249m asl, along the mountainous roads of Takayama district in central Japan. Different growing stages were observed visually and by measuring leaf chlorophyll concentration during 118 to 325 day of year, with an interval of 1-2 weeks.It was observed from ground data that phenological events of walnut trees were affected by temperature in spring time, and the length of leaf development had a negative correlation with altitude levels. On the other hand, seasonal 8-day composite MODIS/NDVI also showed distinct phenological events for deciduous forests in Takayama. But, some discrepancies were found while validating with the ground observed data of walnut trees. Existence of floor vegetation and snow-melting might be the cause for the inconsistency in monitoring phenology from MODIS/NDVI images, before full expansion of canopy.