Characterizing the vertical variability of canopy structure from space: Implications for biodiversity, productivity, and ecosystem functioning

Abstract

The vertical variability of canopy structure plays a crucial role in regulating turbulent flux exchange, biodiversity, and ecosystem functioning. However, accurately measuring this variability over large areas is challenging. We utilize the Global Ecosystem Dynamics Investigation (GEDI) data to characterize the spatio-temporal variability of canopy structure across India’s diverse forest ecosystems for the first time. The GEDI-derived canopy metrics exhibited right-skewness, bimodality, and left-skewness influenced by growth patterns, seasonality, human activities, and climate. The Plant Area Volume Density (PAVD) data from GEDI was used to fit the shape parameters of the beta distribution function, effectively estimating the vertical variability of canopy structure using minimal data. The results show that the beta distribution function shape parameters accurately captured the vertical variability of canopy structure across different biomes ($R^2$ = 0.76 to 0.87, RMSE= 0.1 to 0.2). Clustering the beta distribution parameters identified six distinct foliage profiles in India, which affected radiation interception both diurnally and seasonally at various canopy heights. Further, multivariate functional diversity indices, such as functional richness and functional divergence, captured the combined effects of canopy structural attributes including canopy height, density, complexity, and vertical heterogeneity on biodiversity and productivity. A significant correlation (r = 0.35–0.668, p $\le$ 0.05) was observed between these improved functional diversity metrics and above-ground biomass density across India’s forested regions. Additionally, we found that these functional diversity metrics are influenced by various environmental factors like climate, soil, and topography, which differ across forested regions. These findings enhance our understanding of the complex relationships between canopy structure, the environment, and productivity across India’s biomes and forest ecosystems from spaceborne observations.