Environmental determinants of global potential canopy height
Jingyu Dai, New Mexico State University, jydai@nmsu.edu (Presenter)
Qiuyan Yu, New Mexico State University, qiuyanyu@nmsu.edu
Michael G Ryan, USDA Forest Service, RMRS, mryan@lamar.colostate.edu
Niall Hanan, New Mexico State University, nhanan@nmsu.edu
Tree canopy height is a critical determinant of forest structure and functions. Though usually impacted by many kinds of disturbances, trees tend to have their maximum potential height, determined by genetically determined physiological limitations, climate, soil, and site characteristics. Understanding the geographical pattern and environmental determinants of global potential tree canopy height (Hp) is the first step to comprehensively reveal the patterns and formation of global tree height and biomass accumulation. The Global Ecosystem Dynamics Investigation (GEDI) light detection and ranging (lidar) is an unprecedented new approach providing accurate canopy height measurements at near-global scales (51.6°N to 51.6°S). In this study, we mapped the global pattern of Hp and revealed its environmental determinants with the massive GEDI dataset. We extracted data for >9,000 globally distributed sample plots (10 km × 10 km), empirically defined Hp as the 98th percentile of sampled GEDI-footprints tree heights (RH98) within the plots, interpolated it into a global potential canopy height map, and revealed its environmental determinants with random forest model and linear mixed models. The aridity index (AI, Precipitation/Evaporation) and terrain slope are two of the most important determinants to Hp in random forest model, both of which have strong and positive impacts on Hp, especially when regional mean slope is less than 15° or AI is less than 1.0. The random intercept model has the best prediction to Hp with sigmoid AI as the fixed effect, with slope as the random effect. In this way, AI and slope can explain 82% of global Hp variations. The effect of terrain slope on Hp in arid areas is larger than in humid areas. Our results suggests that water resource is the most important limitation to potential canopy height globally, while steeper terrain slope, especially in the arid area, will promote tree height growth, maybe by reducing local evapotranspiration on shaded slopes, thus improving plant water availability. Our study highlights accurate estimation and mechanistic explanation of the tree height and biomass global variations, providing important information to the dynamic vegetation models and sustainable ecosystem management.
Associated Project(s):
Poster Location ID: 1-60
Presentation Type: Poster
Session: Poster Session 1
Session Date: Tue (May 9) 5:00-7:00 PM
CCE Program: TE