Phylloenvironments (leaf environments) stand at the nexus of ecological and Earth systems science. Integrating leaf ecophysiology, phenology, plant water relations, and atmospheric and solar radiative conditions, phylloenvironments play key roles in determining vegetation controls on the atmosphere, regeneration dynamics, and productivity. Advances in technology to probe plant canopies, including with 3-D remote sensing and sensor networks, are transforming measurement of canopy properties, allowing for the inference of leaf environmental conditions and variation. We explore frontiers in phylloenvironmental approaches applied in central Amazonian forests. Using 2+ years of monthly Profiling Canopy Lidar (PCL) surveys we investigate leaf area seasonality and response to a 2015 El Niño associated drought in contrasting canopy positions (heights) and vertical strata (light environments). We also illustrate ongoing work collecting leaf temperature and light environment measurements with a vertically and environmentally stratified within-canopy sensor network in the central Amazon, to parameterize and test radiation transmission and leaf interception and energy balance models driven with 3-D high density Aerial Scanning Lidar.
Results/Conclusions
PCL time series analysis revealed divergent dry season and El Niño drought responses of leaf area at or near canopy surfaces (i.e., high light and temperature environment) vs. in the deep dark understory: leaf area of the uppermost layers declined, while leaf area of the deepest layers showed no change, or even increased (during the drought), in response to water stress or associated increases in light penetration from upper canopy leaf area losses. Intriguingly, canopy position (height) critically mediated these responses, indicating potential tree size dependent ecohydrological differences impacting leaf processes. In sum, with these new data streams on leaf environments, ecophysiological and eco-evolutionary mechanisms dependent on spatiotemporal variation in canopy function and leaf stress can be tested with new rigor. Answering these questions and monitoring phylloenvironments are essential for a predictive understanding of vegetation vulnerability to climate change—particularly, to rapidly improve understanding of the causes and consequences of globally widespread tree loss and die off.