Budburst timings of the dominant trees of lucidophyll forests in Japan.

Abstract

Budburst timings of Castanopsis, Machilus and Quercus (subgen. Cyclobalanopsis) were studied at 17 different areas, from Natori in the Tohoku District to Iriomote Island in the Ryukyu Islands. Budburst is defined here as a stage in which the blades of the first new leaves just begin to unfold. Firstly, sprouting processes of Castanopsis and Machilus shoots were frequently observed in Chiba. Secondly, sprouting stages of new shoots were recorded for these three genera at a suitable season in each area. Based on the data regarding sprouting processes obtained in Chiba, and the sprouting stages observed at different dates and areas, budburst timing at each area was determined. Resultant budburst timings of Castanopsis in the areas from south to north were as follows : late Dec. to early Jan. in Iriomote : mid-Feb. to early Mar. in Okinawa ; late Mar. in Tokunoshima ; mid-Mar. in Yakushima ; late Mar. to late Apr. in Ohsumi Peninsula ; late Apr. in Nara ; early Apr. to late Apr. in Boso Peninsula and early to middle May in Natori. Many of the Machilus and Cyclobalanopsis species also seemed to open their buds around the same time as the budburst of Castanopsis, at all the places. Dominant species of lucidophyll forests thus sprouted earlier in the south and later in the north, although the delay due to the variation of latitude and annual mean temperature was smaller in the north. These observations were generally consistent with the rough descriptions on shoot sprouting which is reported locally in other literatures. Therefore budburst timing of dominant species of lucidophyll forests in Japan seems to be delayed towards the north, while keeping its synchronism among species.