Abstract:
Sensitivity of forest mortality to drought in carbon- dense tropical forests remains
fraught with uncertainty, while extreme droughts are predicted to be more fre-
quent and intense. Here, the potential of temporal autocorrelation of high- frequency
variability in Landsat Enhanced Vegetation Index (EVI), an indicator of ecosystem
resilience, to predict spatial and temporal variations of forest biomass mortality is
evaluated against in situ census observations for 64 site- year combinations in Costa
Rican tropical dry forests during the 2015 ENSO drought. Temporal autocorrelation,
within the optimal moving window of 24 months, demonstrated robust predictive
power for in situ mortality (leave- one- out cross- validation R2
=
0.54), which allows for
estimates of annual biomass mortality patterns at 30 m resolution. Subsequent spa-
tial analysis showed substantial fine- scale heterogeneity of forest mortality patterns,
largely driven by drought intensity and ecosystem properties related to plant water
use such as forest deciduousness and topography. Highly deciduous forest patches
demonstrated much lower mortality sensitivity to drought stress than less deciduous
forest patches after elevation was controlled. Our results highlight the potential of
high- resolution remote sensing to “fingerprint” forest mortality and the significant
role of ecosystem heterogeneity in forest biomass resistance to drought.
