Needle Morphology Related to Chemical Contents in the Needles of Japanese Fir (Abies Firma) Trees Subjected to Acidic Depositions at Mt. Oyama, Eastern Japan

Abstract

Japanese fir (Abies firma) forests on the urban-facing side ofMt. Oyama, eastern Japan are frequently exposed to acidic depositions. These forests have been declining more severely than those on the mountain-facing side. Chlorophyll, N, Mg, K, Ca, P and Al contents were determined for current, one- and two-year-old needles collected from the crown surfaces of Japanese fir tree forming the forest canopy (ca. 30 m height) on both sides of Mt. Oyama. Needle dry mass per needle area on the urban-facing side was significantly smaller than that on the mountain-facing sides for each needle age class. This result suggests that the development of internal tissues of fir needles on the urban-facing side is defective. N and Chl contents per needle area on the urban-facing side were smaller than those on the mountain-facing sides, indicating that photosynthetic activity per needle area is suppressed in the needles from the urban-facing side. For each needle age class, both area- and mass-based Mg contents were smaller on the urban-facing side than on the mountain-facing side, but mass-based Al contents were greater on the urban-facing side. These results suggest that acidic depositions cause nutritional disorders, which, in turn, leads to decreased needle productivity in the fir trees on the urban-facing side.