Estimating underground biomass of bamboo [Phyllostachys sp.] stand using the digital photograph

In this research, the underground biomass of the Phyllostachys pubescens-Phyllostachys nigra mixed-stand was estimated in a 10m x 10m study area settled at Fujihashi village by using the digital photograph. Investigation was carried out with a high-pressure washing machine to avoid destroying the underground parts including stump, rhizome and root. After the underground parts of the bamboo stand were entirely exposed, photograph was taken with a digital camera for each sub-divided small plot of 2m x 2m. To each taken digital photograph, fine tuning was accomplished with Adobe Photoshop 6.0 so that the length of either the neighborhoods of right and left or the upper and lower sides may become the same, such items as fallen leaves, stones, and the stumps of trees were eliminated by visual decipherment. For the corrected picture, the areas of rhizome and root were computed through image processing with the digital number level, respectively. Then, the biomass of the rhizome and root was estimated according to the correlation between the area obtained from image analysis of the digital photograph and the actual dry weight, respectively (rhizome: r= 0.91, root: r=0.81). For living stumps, the biomass was estimated based on the allometric correlation between the diameter at the breast height (r= 0.98). While, for the dead stumps under the soil surface, the biomass was estimated using another allometric correlation established between the diameter at the top hairline of fine root and the dry weight of the shoot base died (r= 0.97). As a result, the biomass of the rhizome, root, and stump was estimated as 15.67, 9.51, and 10.01 t ha(-1), respectively, with the total underground biomass (R) of the mixed bamboo stand being established as 35.17 t ha(-1) for the area studied. The aboveground biomass (T) was obtained according to the allometric correlation between the diameter at the breast height and the surveyed aboveground dry weight, and the value of which was 23.31 t ha(-1). As the results, T/R ratio of the study area was calculated as 0.66 by comparing the total underground biomass with the aboveground one. Furthermore, it was decided that the minimum survey area was 16 - 36 m(2) for estimation of the underground biomass.