The effect of substrate age on lichen cover, on the Big Island of Hawaii

Byram, Lisa

The percentage of ground covered in lichens was estimated in three different 100 sq. ft squares on each of 11 basaltic lava flows dating between 34 and 5000 years of age on the S.W. of the big island of Hawaii. The age of the flow was then plotted against the percent coverage to establish a lichen coverage curve for the area. The growth curve established represents a rapid increase in coverage between 34 and 58 year of age, an uneven increase in the amount of rock covered in lichens between flows of 58 and 89 years of age with an initially rapid decrease followed by a steady decrease to 0.67 percent coverage in a flow of 3000 to 5000 years of age. These results reveal that lichen colony expansion in this climate occurs within the first 90 years of new substrate, after which lichen coverage decreases with vegetation succession. In order to establish a relative lichen growth curve it appears that more sites from 0 to 200 years of age would have to be visited. The findings do however give insight into the rate of succession within this climate in which lichen cover decreased from 80.33% on a flow of 89 years of age to 0.67 % in a flow of 3000-5000 years of age, which is also relevant information in the dating of substrates.