Climatic, vegetative, and disturbance predictors of lichen species’ height in Arctic Alaska, USA

Abstract

Lichens cover approximately 8% of land surface, primarily in alpine and polar habitats. Lichen biomass is often correlated with cover and thallus height, but quick and effective methods of lichen biomass estimation have not been tested across large areas. We utilize a dataset of over 7800 height measurements made throughout the Arctic Network of National Parks in the US to model mat-forming macrolichen height by species as a function of morphological, climatic, and habitat factors. Our goal was to understand how lichen height, as proxy for biomass, varied by species in different areas, and determine which factors best predict lichen height. We found that the single best predictor of lichen height was surface downwelling shortwave radiation. Climatic, vegetative, and other physiographic variables were moderate predictors of lichen height. We determined that differences in height observed between species were not explained by the degree of branching nor thallus width. Our findings highlight that the key factors predicting lichen height may not be easy to mitigate through management (e.g., radiation, vapor pressure deficit, length of growing season), yet may be altered in future climate change scenarios. Further, rapid height field measurements, like those used in our study, could improve our understanding of the drivers of lichen biomass, underscore its variability across species, and could be used for other applications. Accurate biomass measurements are necessary for landscape-scale monitoring and predictions of future lichen biomass in the face of climate perturbations.