Terrestrial lidar scanning reveals fine-scale linkages between microstructure and photosynthetic functioning of small-stature spruce trees at the forest-tundra ecotone

•The forest-tundra ecotone exhibits myriad responses to environmental change.•We related TLS-derived microstructure to photosynthetic functioning of spruce trees.•Microstructure alone explained 28% of the variance in photosynthetic functioning.•Canopy roughness and insolation were most important and were scale-dependent.•Results suggest microstructure may modulate FTE trees’ sensitivity to climate change.