Evaluating the potential for long-term elevated CO2 exposure studies using CO2 springs in Japan

Japan contains an estimated 3, 865 mineral springs, 82 of which are CO2 emitting springs and the 54 cold springs (less than 20°C) of them can potentially be used as surrogates for assessing the long-term (decades-centuries-millennia) effects of elevated CO2 on natural vegetation. Because some mineral springs can emit CO2 over centuries-millennia, they represent the only feasible means for investigating the long-term effects of elevated CO2 on natural vegetation, and depending on output, can provide a free source of CO2 for short-term elevated CO2 manipulative experiments. Little is known regarding the location of CO2 springs in Japan, rates of CO2 emission, and feasibility for conducting elevated CO2 research on natural vegetation. In March of 1998, twelve mineral springs in the Oita, Gifu, and Toyama Prefectures of Japan were surveyed for their potential for studying the effects of long-term elevated CO2 on the physiology of natural vegetation. Analysis of atmospheric gas samples and the 14C content of leaf material indicate that the vegetation surrounding these springs had been exposed to elevated levels of CO2. Most of the springs were not suitable for elevated CO2 research because they were either impacted by human activities (e.g., were pumped, surrounded by cement, or altered for bathing), or were not surrounded by intact natural vegetation. However, one spring (Rindo, Toyama Prefecture) emitted large rates of CO2 within a relatively undisturbed deciduous forest, and thus, represents one of the only known opportunities to study the direct effects of long-term elevated CO2 exposure on deciduous forests. With ca. 40 more known CO2 springs to be surveyed, the potential for conducting elevated CO2 research using CO2 springs in Japan is higher than most other parts of the world.