Usnea lichen community biomass estimation on volcanic mesas, James Ross Island, Antarctica

Ground macrolichens dominated by several species of fruticose Usnea spp. with foliose Leptogium puberulum constitute an important component of the terrestrial ecosystem of James Ross Island. Long-term monitoring of lichen communities in respect to their reaction to ongoing climatic changes in this part of Antarctica became a research task for scientists in recent years. The non-destructive estimation of lichen biomass provides data necessary for the management and protection of Antarctica. We have developed and tested the methodology of non-destructive estimation of biomass of fruticose Usnea species, which predominate in the ice-free tertiary basalt outcrop areas on James Ross Island. In 38 experimental squares (non-destructive measurements), the density and height of lichen thalli were measured and digital photography with ground cover evaluation was performed. Lichen biomass was harvested from 14 experimental squares and analysed for dry mass, chlorophyll a, b content, and thalli surface area (TSA). Predictive linear models were constructed from available non-destructively measured variables with the aim to maximize predictive accuracy for the destructively measured attributes. A total of 82.3?% of variability in the TSA values was explained (87.5?% for biomass determination). Cross-validated prediction error for lichen TSA estimation was 423?cm² (11.5?% of the average TSA). In the case of lichen dry mass determination, cross-validated prediction error was 4.53?g?m^?2 (7.3?% of the average dry mass). This study proves that macrolichens in maritime Antarctica can be monitored non-destructively by simple field methods combining digital photography and measurements of lichen thalli in botanical squares.