日本森林大气中过氧化物的浓度及其对森林植物的影响

为了研究森林衰退的原因,于2000,2001和2002年的8月,分别选择出现森林衰退的日本奥日光白根山落叶树森林和未出现森林衰退的长野县大芝高原红松森林设立监测点,对光化学氧化剂臭氧(O3)和过氧化物的浓度进行监测,同时利用人工气候室对森林植物山毛榉和白桦进行了50′10-9O3、100′10-9O3和50′10-9O3+2′10-9~3′10-9过氧化物(过氧化氢(H2O2)及甲基过氧化氢(MHP))的暴露实验.野外监测结果表明,监测期间奥日光和长野的O3平均浓度相同,奥日光的H2O2及MHP平均浓度均高于长野;大气中的H2O2和MHP总是与O3共存,并且其浓度随O3浓度的增加而增加.暴露实验结果表明,暴露于50′10-9O3+2′10-9~3′10-9过氧化物的山毛榉和白桦出现了不同于O3暴露的叶片伤害症状;与100′10-9O3相比,50′10-9O3+2′10-9~3′10-9过氧化物导致植物出现了严重的叶片伤害和显著的光合速率下降.研究结果表明,除O3外,大气中的过氧化物也是导致森林衰退的原因之一.

The concentrations of atmospheric peroxides and its effects on forest plants in Japan

In order to investigate the cause of forest decline, the field measurements of hydroperoxides and ozone were performed in declined defoliate forest located at Sirane Mountain in Oku-niko and red pine forest located at Oshiba-altiplano in Nagano. The exposure experiments to 50′10-9 O3, 100′10-9 O3 and mixture of 50′10-9 O3 + 2′10-9~3′10-9 peroxides on Beech and Birch were also conducted in outdoor chambers. The results of field measurements showed that there was no significant different in average concentrations of O3 between in Oku-niko and Nagano, however the average concentrations of hydrogen peroxide and methl hydroperoxide were higher in Oku-niko forest than that in Nagano. Atmospheric hydroperoxides always coexisted with O3, and its concentrations increased with rising O3 concentrations both in two site. The exposure experiments showed that different foliar injury symptoms from O3 induced were observed on Beech and birch exposed to 50′10-9 O3 + peroxides. Compared with 100′10-9 O3, 50′10-9O3 coupling with 2′10-9~3′10-9 peroxides induced more severe foliar injuries and greatly decrease in net photosynthetic rates. These results indicate that the mixture of O3 and peroxides were more responsible to the decline of wild forests than that of O3.