Plot size is an important design parameter in forest surveys,
because it has the potential to either dampen or inflate the impact of
edge effects and co-registration error. The edge-effect (noise)
associated with LiDAR metrics is largely unavoidable, and related to
the fact that trees located just outside the plot boundary (not included
in the ground sample) may still have some portion of their crowns
falling within the plot. As well, trees tallied within the plot may have
part of their crowns lying outside the plot boundaries (not measured
by LiDAR). Sample plots that have a large perimeter-to-area ratio will,
in theory, produce LiDAR metrics that are less precise and less
accurate, due to the inclusion of substantially more edge-induced
measurement error. Because the perimeter-to-area ratio of a square or
circular plot declines nonlinearly with increasing plot size, we expect
that larger plots may substantially reduce the negative impact of the
edge-effect on the magnitude and stability of LiDAR metrics.
Furthermore, larger plots maintain a higher degree of spatial overlap
in the presence of GPS positional errors (Flewelling, 2009), exhibit
less between-plot variance (Zeide, 1980), and are therefore less
affected by the co-registration error that inevitably occurs between
ground and LiDAR samples.