Studies of Atmospheric Environment and Its Effects on Forest Ecosystems in Japan and Other East Asian Countries

Abstract

Excess deposition of air pollutants derived from anthropogenic activities may disturb the material cycles and biological responses in forest ecosystems. The forest canopy is an important interface between the atmosphere and ecosystems, and epicuticular wax on a leaf surface quantitatively and chemically changes due to the atmospheric environment. Erosion and degradation of the wax and malfunction of the stomata due to particulate matter (PM) deposited on the leaf surface may accelerate tree water deficiency. The chemical properties of the wax are also related to a deposition process of the PM, such as elemental carbon, and PM-capturing/keeping mechanisms on the tree leaf surface should be investigated to efficiently utilize its air purification ability. Moreover, NO₃⁻ and NH₄⁺ absorptions and NH₃ emission on the leaf surface should also be investigated. In field studies of forested catchments with different climatic zones in the East Asian region, a sulfur isotopic analysis suggested that ecosystem responses are slow and recovery due to air pollution improvement requires time, even though SO₂ emissions and sulfur deposition are tending to decrease. The Asian climate seasonality largely controls the deposition processes of air pollutants and their dynamics in ecosystems. It is suggested that meteorological variations could play an important role, such as mobilization of the air-pollution legacy, especially in the recovery processes.