Canopy throughfall links canopy epiphytes to terrestrial vegetation in pristine conifer forests

Abstract

To what extent does epiphytic community composition in boreal forests reflect soil nutrient status? To answer this question, we investigated potential links between terrestrial plants and lichen-dominated communities in Picea glauca x engelmannii canopies in south-central British Columbia. We combined original data on vegetational composition in the ground and tree layers with published data on elemental uptake in standardized transplants of the lichen Lobaria pumonaria affixed to the lower branches of studied trees. Procrustean association metrics revealed a significant concordance between community composition among the epiphytic and terrestrial vegetation, which was stronger in Mn-enriched conifer canopy settings, and weaker within the cation-enriched dripzones of adjacent Populus trees. We also found that the NMDS1-gradient for each vegetation layer was strongly correlated with base cations (and inversely with Mn) in canopy throughfall, as well as with soil and bark pH. We conclude that elemental composition in canopy throughfall forms a functional link between terrestrial and epiphytic vegetation. • Epiphytes in the lower canopy and plants in the rooting zone of Picea were recorded • There was a concordance between community composition for epiphytes and plants • Across canopy settings, a throughfall gradient underlined both vegetation layers • The gradient ranked from Ca, Mg, K-rich Populus dripzones to Mn-rich conifer stands • Throughfall chemistry likely mediated the link between plants and epiphytes