Abstract:
Ecosystem water regulation couples energy and water balance, depends on the integrity of the ecosystem, and
responds to changes in climate. Changes in tree-water relationships in the biodiversity hotspot of the tropical
Andes in southern Ecuador might be potentially observed at the level of individual trees, thus providing an ef?-
cient ecosystem monitoring method with applications in forest management and conservation at the tree and
landscape levels. In this study,we combine area-averagemeasurements froma laser scintillometer above the for-
est with optical satellite data at high spatial resolution to obtain area-wide evapotranspiration data. The process-
ing of ?eld data includes the calculation of energy storage in forest biomass and the partitioning of
evapotranspiration into transpiration and evaporation. Satellite-based estimates are calibrated by using tower
?ux measurements and meteorological data within periods of humid and less-humid atmosphere. The annual
evapotranspiration was 1316 mm, of which 1086 mm per year corresponds to the forest transpiration at the
study site. Average values of 4.7 and 4.1 mm d?1
per tree crown are observed under humid and less-humid at-
mospheric conditions, respectively, when applying high-resolution area-wide evapotranspiration in individual
crown analysis. Approximately 24% of the observed crowns show a positive monthly change in ET, and 51% of
the crowns show a signi?cant change in the daily ET, which can be considered sensitive individuals concerning
water relationships. The limitations in the area-wide evapotranspiration at the crown level can be explained
by considering the spectral responses of the crown individuals. The presented method can be robustly deployed
in the ecological monitoring of mountain forests.
