Abstract
Polar systems are experiencing rapid climate change and the high sensitivity of these Arctic and Antarctic ecosystems make them especially vulnerable to accelerated ecological transformation. In Antarctica, warming results in a mosaic of ice-free terrestrial habitats dominated by a diverse assemblage of cryptogamic plants (i.e. mosses and lichens). Although these plants provide key habitat for a wide array of microorganisms and invertebrates, we have little understanding of the interaction between trophic levels in this terrestrial ecosystem and whether there are functional effects of plant species on higher trophic levels that may alter with warming. Here, we used open top chambers on Fildes Peninsula, King George Island, Antarctica, to examine the effects of passive warming and moss species on the abiotic environment and ultimately on higher trophic levels. For the dominant mosses, Polytrichastrum alpinum and Sanionia georgicouncinata, we found species-specific effects on the abiotic environment, including moss canopy temperature and soil moisture. In addition, we found distinct shifts in sexual expression in P. alpinum plants under warming compared to mosses without warming, and invertebrate communities in this moss species were strongly correlated with plant reproduction. Mosses under warming had substantially larger total invertebrate communities, and some invertebrate taxa were influenced differentially by moss species. However, warmed moss plants showed lower fungal biomass than control moss plants, and fungal biomass differed between moss species. Our results indicate that continued warming may impact the reproductive output of Antarctic moss species, potentially altering terrestrial ecosystems dynamics from the bottom up. Understanding these effects requires clarifying the foundational, mechanistic role that individual plant species play in mediating complex interactions in Antarctica's terrestrial food webs.
Highlights
Arctic and Antarctic ecosystems have experienced a rapid climate change the rate of change has altered over time and the degree of climate change has been widely variable [1,2]
Moss effects on abiotic conditions. Temperatures in both P. alpinum and S. georgicouncinata mosses were significantly higher in open top chambers (OTCs) compared to control plots (n = 172,800, F = 9906.59, p < 0.0001, figure 1a)
While S. georgicouncinata control plots were significantly warmer than P. alpinum controls (n = 86 400, F = 5.51, p = 0.02, figure 1a), 7 the opposite was true for OTC treatments
Summary
Arctic and Antarctic ecosystems have experienced a rapid climate change the rate of change has altered over time and the degree of climate change has been widely variable [1,2]. The Western Antarctic Peninsula and the Scotia Arc region of the Southern Ocean have been among the fastest warming polar regions [2,8]. Records show a 0.2°C increase per decade from 1950s to 1990s in the Scotia Arc region and an even greater increase of 0.54°C per decade recorded at the Faraday/Vernadsky Station on the western side of the Antarctic Peninsula (maritime Antarctica) [2]. Carbon isotope data from peat cores on Signy Island in the Scotia Arc region suggest that the climate in the past 50 plus years has become both warmer and wetter [10], presumably due to the increase in precipitation, in the form of rain, as well as from glacier melt in summer months. Biodiversity, including plant diversity, in Antarctica is strongly driven by patterns of water availability [11,12,13], and the increase in water availability with climate changes will probably alter patterns of diversity and expose new potential habitats to be colonized by terrestrial biota, pioneer species such as lichens and bryophytes [5,8]
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