Abstract
Stand structure plays an important role in forest ecosystem management. In this study, we
examined the immediate and 3-yr effects of patch thinning treatments on the stand structure
of overstory trees in a 35-yr-old Japanese cedar (Cryptomeria japonica) plantation located in
the Zenlen area, central Taiwan. Among twelve 1-ha plots, 4 plots were randomly assigned to 1
of 3 patch thinning intensities in a randomized complete block design: no removal (control),
and 25 and 50% tree removal in the area. The stand structure of the residual overstory trees
was examined immediately after thinning and again after 3 yr using non-spatial stand structural indices (vertical evenness and the diameter at breast height (DBH) distribution), a pair correlation function (G function), and spatial stand structural indices (diameter differentiation index and
structural complexity index). The vertical evenness of the overstory tree canopy was reduced
after thinning. Unlike the left-truncated Weibull DBH distribution commonly caused by thinning
from below, no notable left-truncated Weibull distribution caused by patch thinning was detected.
The change in the spatial point pattern expressed by the G function with scale-up at a distance
scale was influenced by the intensity of the thinning. The stand structural complexity was
affected by the spatial scale used and stand attributes surveyed, and it was reduced immediately after thinning but had varying impacts on the DBH and tree height.