経年空中写真

As the forest growth slowly, the change in it’s condition is relatively small. The mentioned change will be clearer if it is observed periodically with an interval of several years. A continuous aerial photographs is one of the tool can be applied for this purpose. In relation to this, an interpretation of several fixed observation points on a continuous aerial photographs has been conducted to explain the change in forest environmental condition. The observation object is Kyushu University Forests in Kasuya District with an area of 486.19ha. A serial of continuous aerial photographs taken in 1963, 1974, 1981 and 1986 has been applied in this study (Refer to Fig.1, Table 1 and Fig.2). Kasuya University Forests has been devided into 5 block namely A, B, C, D, and E. The observation point on aerial photographs has been plotted systematically with an interval of d=√<A/N>×100=√<486.19/316>×100=124.04≒120m, where A and n are forest area and the number of compartment in Kasuya University Forests, respectively. Accordingly, there are 308 observation point has been plotted on every set of aerial photographs (Refer to Table 2).Further, several classification has been made as the standard for interpretation of every observation point on aerial photographs as follows; (1) Species: Cryptomeria japonica(Sugi=S), Chamaecyparis obtusa (Hinoki =H), Pinus (Matsu=M), broadleaved (L), (2)Crown density dense (D_1), medium (D_2), sparse (D_3), (3) Crown diameter: small (C_1) medium (C_2), large (C_3), (4) Tree height: small (H_1), medium (H_2), high (H_3), and (5) Stand ages: juvenile (A_1), medium (A_2) and old (H_3), as presented in Table 3. The interpretation result for 4 sets of continuous aerial photographs are presented in Table 4. Regarding the factors that can not be clearly interpreted on aerial photographs, field observations have been conducted From the interpretation result was found that the corresponding occupied area of every observation point, α is equal to 1.44ha. The estimation of corresponding area for every factor on observation point was conducted and the actual area was observed plantation statistic data and forest survey statistic data (the expection for the corresponding area of photographs taken in 1963 where available data were not found). Then, t-test has been conducted to clearity the difference between estimated area and actual area for every species and age class (Refer to Table 5). As the result, the estimated area and actual area were not differ significantly. This mean that the estimated area to be fitted well to the actual area Further, crown density (D), crown diameter (C), tree height (H), and stand age (A) in every observation point were also interpreted and the interpretation result is presented in percentage (Refer to Table 8). Also, the relationship between interpreted and measured factors in every block are presented in graph. As the result, it was found that there is as mall variation in every block. However, in overall, there is a constant rate of forest to be preserved, especialy in the whole of observed area, the development of forest from the juvenile and medium to the old one is clearly observable. This mean that the original social function of forest expressed by forest environmental condition is being prevented well. Fig.3 shows the resultant figure of block A, B, C, D and E.