Ecological and Physiological Studies on the Vegetation of Mt. Shimagare

Photosynthesis, respiration, needle thickness and nitrogen content were measured in the domidant, intermediate and suppressed trees in a 20-year-old Abies stand of the subalpine coniferous forest on Mt. Shimagare.<br>1. Needle thickness increased with needle ages and with size classes of the trees. In general, the thickness was larger in A. Mariesii than in A. Veitchii.<br>2. Photosynthesis and respiration decreased with ageing of the needles and with size diminution of the trees. The same trends were observed pertaining to the nitrogen content of needles. These functions and content were generally higher in A. Veitchii than in A. Mariesii, especially on a weight basis.<br>3. The needles of the dominant trees showed the characteristics of sun-leaves, and those of the suppressed, of shade-leaves, because these tree classes were situated in totally different light conditions within the Abies stand.<br>4. The leaf temperature optimal for gross photosynthesis was in the Abies species about 20°, which was fairly lower in comparison with the optimum temperature determined in broad-leaved evergreen trees in southern Japan, as accorded with the colder habitat of Mt. Shimagare.<br>5. Respiration and nitrogen content in branchlet decreased on a dry weight basis, but increased on a surface area basis, with its increasing diameter. In the respiration of entire trunk and root system, the intermediate (and dominant) was higher than the suppressed. Between the two Abies species there was little difference in all these measures.