Effects of topography, soil type and forest age on the frequency and size distribution of canopy gap disturbances in a tropical forest

[摘要] Treefall gaps are the major source of disturbance in most tropical forests.The frequency and size of these gaps have important implications for forestecosystem processes as they can influence the functional trait distributionof tree communities, stand-level aboveground biomass and productivity.However, we still know little about the relative importance of environmentaldrivers of gap disturbance regimes because existing studies vary greatly incriteria used for defining gaps, in the spatial extent of the study area, andthe spatial resolution of canopy height measurements. Here we use lidar(light detecting and ranging) to explore how forest age, topography and soiltype affect canopy disturbance patterns across a 1500 ha tropical forestlandscape in central Panama. We characterize disturbance based on thefrequency distribution of gap sizes (the "gap size distribution"), and thearea of the forest affected by gaps (the "gap area fraction"). We foundthat slope and forest age had significant effects on the gap sizedistribution, with a higher frequency of large gaps associated withold-growth forests and more gentle slopes. Slope and forest age had similareffects on the gap area fraction, however gap area fraction was also affectedby soil type and by aspect. We conclude that variation in disturbancepatterns across the landscape can be linked to factors that act at the finescale (such as aspect or slope), and factors that show heterogeneity atcoarser scales (such as forest age or soil type). Awareness of the role ofdifferent environmental factors influencing gap formation can help scale upthe impacts of canopy disturbance on forest communities measured at the plotscale to landscape and regional scales.

[学科分类] 地球化学与岩石