Abstract
Forest canopy structure (CS) controls many ecosystem functions and is highly variable across landscapes, but the magnitude and scale of this variation is not well understood. We used a portable canopy LiDAR system to characterize variation in five categories of CS along N = 3 transects (140–800 m long) at each of six forested landscapes within the eastern USA. The cumulative coefficient of variation was calculated for subsegments of each transect to determine the point of stability for individual CS metrics. We then quantified the scale at which CS is autocorrelated using Moran’s I in an Incremental Autocorrelation analysis. All CS metrics reached stable values within 300 m but varied substantially within and among forested landscapes. A stable point of 300 m for CS metrics corresponds with the spatial extent that many ecosystem functions are measured and modeled. Additionally, CS metrics were spatially autocorrelated at 40 to 88 m, suggesting that patch scale disturbance or environmental factors drive these patterns. Our study shows CS is heterogeneous across temperate forest landscapes at the scale of 10 s of meters, requiring a resolution of this size for upscaling CS with remote sensing to large spatial scales.
Highlights
In forested ecosystems, the density and spatial arrangement of vegetation, or canopy structure (CS), imposes strong controls on many scale-dependent ecosystem functions
Significant differences were observed among forested landscapes in the distance at which variation in mean outer canopy height (Figure 3A) and VAI (Figure 3E) stabilized
Our study shows that the spatial scale of stability in CS may be best characterized by terrestrial LiDAR and scaled up to a larger footprint with aerial LiDAR
Summary
In forested ecosystems, the density and spatial arrangement of vegetation, or canopy structure (CS), imposes strong controls on many scale-dependent ecosystem functions. CS in the form of leaf area and arrangement exerts a strong influence on forest production through its effects on light absorption [1] and light-use efficiency [2,3]. The spatial scale at which canopy structure exerts functionally meaningful effects on ecosystem processes varies depending on forest type and architecture, environmental factors, and the ecosystem functions and the CS element of interest. Inferring and scaling ecosystem functions from remotely sensed measurements of forest structure requires an understanding of how different measures of CS vary spatially across forested landscapes
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