Seasonal Changes in Interclone Variation Following Ozone Exposure on Three Major Gene Pools: An Analysis of Cryptomeria Japonica Clones

Takafumi Miyama,Takeshi Izuta,Hiroyuki Tobita,Kentaro Uchiyama,Saneyoshi Ueno,Mitsutoshi Kitao,Kenichi Yazaki,Asako Matsumoto,Akira Uemura

doi:10.3390/atmos10110643

Abstract

Recently, there has been a continuous increase in the concentration of tropospheric ozone in urban forests in Japan. Since monoterpenes are precursors to ozone, we need to evaluate the effects of ozone exposure on all tree species that are considered to be sources of monoterpenes. Cryptomeria japonica, which is the most widely planted afforestation tree, is classified into three different gene pools. However, the interclone variation for seasonal changes in the ozone exposure effect has not been evaluated. Thus, free-air ozone enhancement experiments were conducted using three representative clones of C. japonica in the summer and winter. After exposure to twice the ozone concentration in the ambient atmosphere, the effect on the monoterpene emission rate was found to be considerably different among the clones and for the different seasons. The monoterpene emission rate after ozone exposure increased in winter and summer in the native clones (Donden and Yakushima) in the snow area and heavy rain area, respectively. Since monoterpenes are antibacterial substances, each clone adapted sensitivity to stress during each season upon considerable damage. These results suggest that not only differences between tree species but also differences between clones are important for evaluating seasonal variation characteristics after ozone exposure.

Highlights

In recent years, there has been an increase in the concentration of ozone in Japan due to a decrease in NO titration and an increase in transboundary air pollution [1,2,3]
It the has ozone been in several that gymnosperms increase after exposure; reported in several studies that gymnosperms increase after ozone exposure; the ozone exposure effects were considerably different between tree species, the mechanism is still exposure effects were considerably different between species, the is still poorly understood
The results of this study indicated that there was an interclone change between the summer and winter after long-term ozone exposure

Summary

Introduction

There has been an increase in the concentration of ozone in Japan due to a decrease in NO titration and an increase in transboundary air pollution [1,2,3]. If Japanese forests emit more BVOCs because of an increase in the tropospheric ozone concentration, this may accelerate the increase in ozone concentration as a positive feedback effect because BVOCs play a role as a precursor to ozone. Atmosphere 2019, 10, 643 to estimate BVOC emissions throughout Japan led to significant differences in the concentrations of ozone and secondary organic aerosols in air quality simulations [8,9]. Monoterpenes (C10 H18 ) are BVOCs that are emitted from coniferous forests in Japan. They are considered to be important because it was estimated that they can produce more than 10 times the amount of ozone compared with isoprene (C5 H8 ) [10]. The planted area accounts for 18% of the entire forest

Methods

Results

Discussion

Conclusion