The area studied is situated at an altitude of about 300 m near the Narugo spa in the northwestern part of Miyagi Prefecture. In the central part of the area there is a small lake, Katanuma ; this was a crater of the ancient Nargo volcano. Though the volcano is not active, gas containing hydrogen sulfide and sulfurous oxide, etc. has been issuing through many small holes on the bottom and shore of tne lake for more than 20 years. And, a solfatara field was established. A small factory refining the sulfur from the sulfur deposit at the bottom of the lake, was constructed on the northern shore of the lake about 30 years ago. The vegetation of the area has been wasted by such harmful gases as hydrogen sulfide and sulfurous oxide. Subsequently the greater part of the area become covered by characteristic plant communities. Based on the physiognomy and floristic composition the vegetation of the area can be distinguished into eight plant communities as follows ; Carex angustisquama community, Miscanthus sinensis community, Miscanthus sinensis-Cladonia crassensis subsp. japonica community, Sasa palmata community, Sasa palmata-Miscanthus sinensis community, Vaccinium ovalifolium-Vaccinium hirtum community the secondary forest of Quercus serrata and the planted forest of Pinus densiflora. With the decreasing of the harmful action of the gases, the vegetation changed and can arranged in the following order : the bare ground-the Carex angustisquama community-Miscanthus sinensis-Cladonia crassensis subsp. japonica community-Vaccinium ovalifotium-Vaccinium hirtum community or Sasa palmata community. By the intense weathering has of the original solfatara soil, the crystaline minerals were destroyed and aluminum, iron and other cations washed away, resulitng in a white silica-rich material. Mineralogical study showed the existence of volcanic ash soil at some places. With the increasing of the distance from the solfatara, the extent of the mixing of volcanic ash soil increases. A clear relationship can be recognized between the soil and the vegetation. Successions of the soils in the solfatara field is influenced by both the mixing of volcanic ash soil and the plant succession.