Relationships between vegetation change and geomorphic conditions in suburban forests of Japan: Analysis by means of digital aerial photogrammetry and geographical information systems

Abstract

The relationships between successional vegetation change and geomorphic conditions were analyzed by using a high-resolution digital terrain model (DTM) and a time series of converted digital vegetation maps combined within a geographical information system (GIS). The results of the analysis confirmed that the pattern of vegetation change is a function of geomorphic conditions (measured in terms of spatio-statistical values of various parameters and time series of those values). Current geoecological studies are usually carried out by means of detailed field observations with high spatial resolution, and the results of our study suggest that a GIS can easily deal with such data over a large area and long time period. In the study area, unforested s ites were reforested using Japanese red pine (Pinus densiflora) as part of the forest rehabilitation work that occurred in the early 1950s. After that, two main patterns of vegetation change from pine forest to deciduous broadleaved forest occurred. In one type, the deciduous broadleaved forest reappeared quickly. In the other, the pine forests remained for a long time. Stands that underwent relatively rapid succession were found on north-facing gentle slopes close to large bodies of water. Stands that did not undergo rapid succession were found on steeper, warmer, and drier slopes (often south-facing slopes farther from bodies of water). The rate of forest succession towards deciduous broadleaved forest is a function of these geomorphic conditions. This suggests that forest succession is influenced by intermediate factors controlling by geomorphic conditions of site, such as soil moisture and soil thickness.