Soils and topography drive large and predictable shifts in canopy dynamics across tropical forest landscapes

Tropical forests can vary enormously in their 3D structure and dynamics across surprisingly small spatial scales. However, the drivers that underpin this local-scale variation in forest structure and dynamics remain poorly understood. We acquired repeat airborne laser scanning data across an old-growth tropical forest landscape in Malaysian Borneo, characterized by a steep gradient in soil fertility and topography that gives rise to large variability in canopy 3D structure. Using this unique dataset, we explored how local-scale variation in topography and forest structure shapes rates of gap formation, closure, and canopy growth across the landscape. We found that both canopy gains and losses were 2.5-4.7 times greater in low-lying alluvial forests on fertile soils than in nearby nutrient-depleted kerangas forests on hilltops. Moreover, we found that variation in canopy 3D structure and dynamics was tightly coupled across the landscape, with taller and more structurally heterogeneous canopies also experiencing faster rates of gap dynamics. Our study highlights the key role that soils and topography play in shaping the structural complexity and dynamics of tropical forest landscapes.