Abstract

A maximum entropy algorithm modelling program (MaxEnt 3.3.2) and a GIS software system (ArcGIS9.3) were used to study and model the distribution of 131 occurrences of Macromitrium and 66 occurrences of Orthotrichum in China in relation to 19 bioclimatic variables and percent tree cover. The information obtained can help predict the potential distribution range of these species in China, and also provide an understanding of factors influencing their current geographical distribution patterns so as to achieve better conservation of species diversity in the future. The species occurrence data were obtained from field work, relevant literature and herbarium specimens examined. Based on the integrated habitat suitability indices calculated, results show that Macromitrium have higher habitat suitability in the southeast and some southern provinces of China, i.e., in Zhejiang, Taiwan, Hainan, Fujian, Chongqing, and lower distribution probability in northwest, northeast and some northern provinces. Likewise, Orthotrichum has higher habitat suitability in Yunnan, Beijing, Liaoning, Jilin, Guizhou, Shanxi, Sichuan and Hebei, and lower distributional probability in the southwest. The distribution probability of Macromitrium increases with increased annual precipitation, precipitation in the wettest month, and in both the coldest and wettest quarter of the year. The distribution probability of Orthotrichum increases rapidly with increasing annual precipitation upto 200 mm, and then decreases when annual precipitation exceeds 200 mm. The distribution probability of Orthotrichum reaches its highest peak when the mean temperature of the warmest quarter is between 15 and 20℃. The relationship between species number (Y) of Macromitrium and annual rainfall (X₁) is described by the equation Y = –0.0369+0.0003X₁ (r = 0.5347, P<0.001, n = 131), and with the annual temperature (X₂) by Y = 0.0831e^0.001X2 (r = 0.5525, P<0.001, n = 131). The relationship between species number (Y) of Orthotrichum and annual rainfall (X₁) equates to Y = 1.0008–0.1184ln X₁ (r = 0.4199, P<0.001, n = 66), and with annual temperature (X₂) to Y = 1/(0.1309X₂+3.4581) (r = 0.2524, P<0.01, n = 66). Based on the data presented above and using the GIS software system (ArcGIS9.3), the distribution maps of predicted species number of Macromitrium and Orthotrichum in China in relation to annual temperature and rainfall are shown. The southeast, south and central regions of China, as well as southeastern areas of Yunnan and Xizang would have more Macromitrium species, and the northwest region, Qinghai-Tibet Plateau, Inner Mongolia and Heilongjiang would have more Orthotrichum species.