. Lichen mapping in Chiang Mai city
7.1.1 The method used is slightly modified from the VDI method (VDI, 1995). The study sites in urban and suburban areas of Chiang Mai city will be devided into grid-squares size of 0.5 x 0.5 km2 and 1.0 x 1.0 km2 , the center of the city and its surrounding, respectively. Six mango trees (Mangifera indica L.) was selected in each grid square for lichen frequency investigation.
7.1.2 Species and frequency of lichens on the tree trunk will be registered by using a grid-frame size of 20 x 50 cm2 which is divided to 10 subsquares, size of 10 x 10 cm2. Grid frame will be put on the trunk of selected mango trees in each grid square for lichen investigation.
7.1.3 Other environmental factors, for examples; trees diameter, type of bark, pH bark, the orientations where the grid frames place on the trunk will be recorded.
7.1.4 Frequency of lichens will be used to calculate indices which indicate air quality (AQI). A rich variety of lichen species exists more frequently in areas with clean air, while low frequency indicates poor air quality.
7.1.5 Air quality index will be used to produce a map to define the zones of different air quality in the study areas. The map will be produced by using Geographic Information System (GIS) program.
7.1.6 Some lichen species will be selected in oder to produce maps of their distribution.