Canopy Rainfall Storage Capacity Quantified Across the Diversely Vegetated Sites of the United States National Ecological Observatory Network

ABSTRACT This study investigates canopy storage capacity ( S )—the maximum amount of rainfall stored in a forest canopy—using field data from 648 storm events across 15 diversely vegetated sites of the United States National Ecological Observatory Network (NEON). We compared these S values to remotely sensed and ground‐based vegetation metrics of leaf area index (LAI), mean canopy height, and biomass density. We found that S values were generally constrained within a narrow range (site‐level medians averaged 0.9 mm and ranged from 0.5 to 1.5 mm) relative to larger ranges in biomass, height, and LAI. Vegetation height partially explained this variation; other tested vegetation‐structure variables did not significantly explain S . Significant seasonal variations in S were also observed in a subset of sites. Within sites, S often varied with vegetation traits, but those relationships were inconsistent across sites. We also found that specific storage capacity ( S spec ; mm of S per unit LAI, as inferred from ground‐based LAI measurements), with site‐level median values averaging 0.6 and ranging from 0.3 to 1.7, was not effectively explained by variations in vegetation structure. The limited ability for vegetation metrics to explain S or S spec may be due to challenges in a single vegetation metric capturing the diverse traits that explain canopy storage, or due to scale mismatches in throughfall measurements relative to available vegetation‐structure data. Regardless of reason, our findings contrast with common assumptions and modelling conventions and do not suggest that using vegetation‐structure metrics to scale S is more appropriate than assuming S to be constant across forested sites.