Environmental, reproductive, and nutrient drivers of three-dimensional growth in the forest lichen Lobaria pulmonaria.

Measuring growth dynamics has been fundamental to understanding lichen biology and ecology. In this integrative analysis, I synthesize and reanalyze published data on three-dimensional growth in the foliose cephalolichen Lobaria pulmonaria transplanted in pristine North American forests, encompassing thallus area expansion, biomass accumulation, thallus thickening, and reproductive investment across multiple environmental gradients. Best subset regression selection and linear mixed models were applied to identify the principal internal and external factors influencing growth, specifically thallus area expansion and thickening, quantified as increases in specific thallus mass. The analyses reveal pronounced intrathalline growth heterogeneity, significant trade-offs between reproductive investment and growth, and the multifactorial influences of bark pH, elevation, light regime, and phosphorus availability. Light was often a limiting growth factor within forest interiors, whereas excessive stand openness caused chlorophyll bleaching and reduced growth. Initial phosphorus enrichment enhanced thallus thickness but did not consistently promote area or biomass expansion. Taken together, these finding highlight the habitat specialization of L. pulmonaria and the importance of bark pH, light, hydration, and reproductive investment in shaping growth dynamics. The study advances the understanding of growth strategies in L. pulmonaria and provides a foundation for predicting responses to environmental change and guiding conservation efforts.