The Amazon rainforest acts as one of the largest terrestrial contributors to global carbon cycling. However, the response of Amazon forests to climate variability and long-term change is highly uncertain. We focus on investigations, encompassing the effects of climate, interacting with hydrologic, edaphic, and geomorphological variations across different forest ecotypes and over multiple events, on ecological responses to drought. Remotely-sensed greening/browning responses to multiple droughts are examined by identifying three regionally-affiliated Amazon forest ecotypes, defined by fertility, climate, and vegetation traits, with distinct drought responses. We found, in fertile Southern Amazonia, local hydrological environments structured drought response: remotely-sensed drought-associated “green-up” was greater in shallow water table forests (SWTF, whose greater water availability heightened responsiveness to excess sunlight) than those with deep water tables, but diminished with drought duration. In other regions, however, unexpected “green-up” during drought was driven instead by drought-associated relief from extreme wetness (in the Everwet northwest), or by presumed deep-water access of taller more resilient dense-wood trees (in the northeastern Guiana shield). These findings suggest that fertility, climate and community adaptations to local environments jointly determine forest vulnerability.
Amazon forest, photosynthesis, drought, remote sensing, hydrology