Arctic and alpine ecosystems are likely to experience a faster rate of warming than most due to climate change. This is expected to cause shifts in the range and abundance of plant communities in these fragile ecosystems. Bryophytes (liverworts, hornworts and mosses) are particularly vulnerable to environmental change as many have low-temperature optima for photosynthesis and a narrow range of suitable temperatures for net photosynthetic gain.
Bryophytes in Arctic and alpine regions are important in terms of biodiversity, typically exhibiting almost double the species richness of vascular plants in the Arctic. They are also important contributors to cover and biomass. Yet, most previous long-term studies have focused on the impacts of warming on the vascular plants of these ecosystems rather than bryophytes.
In their new study published in AoBP, Alatalo et al. describe the long-term effects of experimental warming on bryophytes in a high alpine heath and a meadow community in northern Sweden. Experimental warming with open-top chambers (OTCs) was applied for 18 years from 1995 to 2013. The authors found warming to cause bryophyte cover to decrease by 75% and 48% in the heath and meadow, respectively, over 18 years. Bryophyte species richness also declined, by 39% and 26%.
The decline in bryophyte cover observed in this study was driven by a general decline in abundance of many species and was first observed after seven years and accelerating after this time. The authors concluded that increased litter fall and increasing deciduous shrub cover were the main factors leading to the decline in bryophyte cover. The non-linear response to warming over time underlines the importance of long-term experiments and monitoring studies such as this.