Carbon and water fluxes over a temperate Eucalyptus forest and a tropical wet/dry savanna in Australia: measurements and comparison with MODIS remote sensing estimates

Measurements of Lai and gross primary production (PG) at the two sites were compared to estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS) remote sensing data products. The MOD15 algorithm overestimated Lai by a factor of two at Tumbarumba but gave reasonable magnitudes and seasonal variation for the savanna. At Tumbarumba, MOD17 gave excellent estimates of the annual amplitude in PG but was less satisfactory in predicting the phase of the variations. MOD17 overestimated PG at Virginia Park during the dry season and the low-rainfall summer of 2002-2003 but gave satisfactory results during the other two wet seasons. Most of the variance in PG at both sites was explained by absorbed photosynthetically active radiation. Significantly improved predictions were obtained for the savanna by modifying the MOD17 algorithm to account for rainfall and potential evaporation in the antecedent 3 months, a surrogate for soil water availability.