Abstract
Quantification of climatic damage to forests and its differences among regions and species is essential for forestry and forest conservation. Drought risk of forests is one of the critical subject in recent years under the global warming. Temporal, regional, and among-species variations in drought damage at private forests in Japan were investigated based on statistical data from 1959 to 2014, especially concentrating on recent 36 years for which original detail data were available. 1- to 5-years-old stands of private planted forests (PPF1-5) account for 95.3% of actual loss area, which was calculated as the damaged area multiplied by the ratio of the number of damaged trees to that of planted trees, caused by drought damage at whole private forests. The mean annual ratio of actual loss area caused by drought damage to total forested area (rd_real) of PPF1-5 over Japan was 0.26% and showed large inter-annual fluctuation without significant temporal trend. In variation among prefectures, the mean annual rd_real at PPF1-5 were relatively large in Hokuriku, Koushin, Kinki, and Chugoku regions (the south western part of the main island of Japan) and Kagawa prefecture, and were small in Tohoku, Kanto, and Tokai regions (the north eastern part of the main island of Japan) and Hokkaido and Kyushu islands. Annual rd_real of Chamaecyparis obtusa at PPF1-5 was larger and smaller than those of Cryptomeria japonica in 17 and 2 prefectures, respectively. Considerable amount of actual loss area was reported at mature stands in Kyushu in 1994, in which rainfall was quite small than usual from summer to early autumn. As the drought damage at mature stands, which should cause greater economic loss and ecological disturbance, occurred infrequently, comprehensive and long-term monitoring of forest damage needs to be continued to evaluate the trend of drought damage at mature stands.
