Arctic and Antarctic ecosystems are experiencing rapid climate change and because Polar ecosystems are highly sensitive to change, the impacts will be pronounced in these regions. The western Antarctic Peninsula is one of the fastest warming regions on Earth, resulting in a mosaic of ice-free terrestrial habitats. The ice-free areas of the Antarctic Peninsula are dominated by cryptogamic flora, particularly a diverse assemblage of bryophytes (>100 species). Mosses provide habitat for a diversity of microorganisms and invertebrates, forming complex food webs that regulate organic matter decomposition, carbon sequestration and nutrient cycling. Further, the presence of dense moss mats provides a high-level of soil thermal insulation, further highlighting the important role of mosses in linking above- and below-ground ecosystem processes in Polar regions. In this research we investigated the impacts of passive warming by Open Top Chambers (OTCs) in moss-dominated ecosystems on Fildes Peninsula, King George Island, Antarctica, a region of increased climate warming. We compared species-specific temperature effects, moss canopy morphology, sexual reproductive effort and invertebrate communities between OTC and control moss communities for two moss species, Polytrichastrum alpinum and Sanionia uncinata, that make up over 65% of the terrestrial vegetative cover in the area.
We found distinct reproductive shifts in P. alpinum under passive warming compared to those without warming. On the other hand, S. uncinata was never reproductive during the warming experiment. Moss communities under warming also had substantially larger total invertebrate communities than those in control moss communities, and invertebrate communities were significantly affected by moss species and moss reproductive effort. We further observed substantial species-specific thermal differences among contiguous patches of these dominant moss species. Our results suggest that continued warming will differentially impact the reproductive output of Antarctic moss species and is likely to dramatically alter terrestrial ecosystems dynamics from the bottom up, understanding these effects will require clarifying the foundational mechanistic roles that individual moss species play in mediating complex interactions in Antarctica’s terrestrial food-webs.