FIFTEEN YEARS OF CANOPY DYNAMICS ANALYZED BY AERIAL PHOTOGRAPHS IN A TEMPERATE DECIDUOUS FOREST, JAPAN

Abstract

Aerial photographs were used to analyze long-term canopy dynamics over 15 yr in a large area (25.25 ha) for a mixed deciduous forest in the Ogawa Forest Reserve, central Japan. Digital elevation models of canopy surface were made from aerial photo- graphs taken in four summers at 5-yr intervals from 1976 to 1991. A digital elevation model of ground surface was also made from the aerial photograph taken in winter 1991. The canopy height at each location was calculated from the elevational difference between the canopy and the ground, and the vegetation profile technique was applied to quantify canopy dynamics. The size distributions of gaps at each observation time and of gaps that were created between observation times followed a power function model. While the rates of gap formation and closure throughout the whole period were nearly balanced, they showed large temporal variations among the observation periods. Spatial distribution of newly created gaps was significantly biased toward the edges of old gaps. Probability of repeated gap creation was also significantly high. Analysis of changes in the canopy height profile by a transition probability matrix showed that gap area distribution of this forest may be nearly in a steady state.