Landscape-scale changes in forest structure and functional traits along an Andes-to-Amazon elevation gradient

[摘要] Elevation gradients provide opportunities to explore environmental controlson forest structure and functioning. We used airborne imaging spectroscopyand lidar (light detection and ranging) to quantify changes inthree-dimensional forest structure and canopy functional traits in twenty25 ha landscapes distributed along a 3300 m elevation gradient from lowlandAmazonia to treeline in the Peruvian Andes. Elevation was positivelycorrelated with lidar-estimated canopy gap density and understory vegetationcover, and negatively related to canopy height and the vertical partitioningof vegetation in canopies. Increases in canopy gap density were tightlylinked to increases in understory plant cover, and larger gaps(20–200 m²) produced 25–30 times the response in understory coverthan did smaller gaps (< 5 m²). Vegetation NDVI andphotosynthetic fractional cover decreased, while exposed non-photosyntheticvegetation and bare soil increased, with elevation. Scaling of gap size togap frequency (λ) was, however, nearly constant along the elevationgradient. When combined with other canopy structural and functional traitinformation, this suggests near-constant canopy turnover rates from thelowlands to treeline, which occurs independent of decreasing biomass orproductivity with increasing elevation. Our results provide the firstlandscape-scale quantification of forest structure and canopy functionaltraits with changing elevation, thereby improving our understanding ofdisturbance, demography and ecosystem processes in the Andes-to-Amazoncorridor.

[学科分类] 地球化学与岩石