Development of measurement system for evaluating forest ecosystems: Measurement method of aboveground biomass growth by using airborne laser survey

In order to develop a monitoring system for evaluating forest ecosystems, a method of forest stand measurement using airborne laser survey was examined. The study area was a Larix leptolepis forest in the Tomakomai Flux Research Site. The laser survey data were taken in the year 1999, 2001 and 2003. A canopy DSM (Digital Surface Model) was constructed from first pulse of the laser survey data, and the DTM (Digital Terrain Model) was constructed from the last pulse of it. The DCHM (Digital Canopy Height Model) was made by the difference of the canopy DSM and DTM. The crowns of trees were extracted from the canopy DSM by the Watershed method. Tree height was measured by the DCHM within the crown. The stem volume of trees was calculated by using the relationship between tree height and the stem volume. Since the crowns of understorey tree could not be detected, the MNY method was used for the prediction of understorey trees. The results that the growth of the forest stand height was 0.23-0. 25cm·y^-1,and that the the growth of the forest stand height was 11m³·y^-1, both were near to the data obtained by complete enumeration, therefore, this method has a precision for the measurement of biomass growth.