Lichens containing cyanobacterial photosynthetic partners not only add biodiversity and habitat to forest ecosystems, but provide nutrients to flora and fauna through the fixation of atmospheric nitrogen. Although lab studies demonstrate some physiological requirements of cyanolichens, the literature lacks a climate-based distribution model for these organisms in the Pacific Northwest. Through the collection of quantitative field data, we help explain the distribution and habitat preferences of these organisms. This study documents lichen abundance and community composition in a west-east climate gradient across Oregon. Both epiphytes and ground-dwelling lichens are sampled in 32 Forest Inventory and Analysis (FIA) plots, established by the United States Forest Service, and 24 plots established in two other lichen ecology studies. Each of these plots already contained either epiphyte or ground-layer data. We supplement any missing areas to obtain total plot diversity in 56 plots ranging from central Oregon to the coast. We then use this data to address the following questions: 1) How does total plot diversity compare to epiphyte-only measurements in different climate zones? 2) Where are cyanolichens more relatively abundant in Oregon? 3) Do patterns of cyanolichen abundance in the epiphyte layer match the patterns of cyanolichens in the ground-layer?
Results/Conclusions
We analyzed lichen communities in relation to climatic and topographic variables such as elevation, mean annual precipitation, heat load, potential direct incident radiation, as well as in relation to dominance by hardwoods versus conifers. The community weighted averages of lichens containing cyanobacteria were calculated to compare relative community composition to climate. Results from preliminary ordination analyses suggest that lichen communities with higher proportions of cyanobacterial lichens tend to occur in plots with a higher ratio of hardwoods to conifers. Additionally, plots at lower elevations and higher precipitation appear to contain relatively higher cyanolichen abundances. We also found plots with bipartite lichens (those containing only one photobiont – either cyanobacteria or green algae), tend to include tripartite lichens (containing both cyanobacteria and green algae) as well. Future work will extend and intensify the sampling into the steppe region of central Oregon and provide a cohesive distribution model for cyanobacterial lichens in Oregon.