Abstract: Based on field investigations of species of epiphytic bryophytes and their distribution, frequency and coverage in one of most polluted areas in southwest China, the IAP (Index of Atmospheric Purity) was calculated. According to the results, the area investigated could be divided into three regions: 1) seriously polluted region, with 0—2 species of epiphytic bryophytes, IAP <10 and precipitation pH3—3.5; 2) polluted region, with 4—13 species of epiphytic bryophytes, IAP10—30 and precipitation pH4—5; and 3) basically no-polluted region, with more than19 species of epiphytic bryophytes, IAP40—90 and precipitation pH5.5—6.5. The experiments of effects of artificial acid rain on bryophytes growth showed that most of sampled species died within a half year under the acid rain with pH<3; 80% plants died in a year under the acid rain with pH4.5, and some species tolerating to acidity could grow well after a year under the acid rain with pH3.

Key words: Bryophytes, Air pollution, Acid rain