Data from: Environmental change alters nitrogen fixation rates and microbial parameters in a subarctic biological crust

Together, Biological Soil Crust (BSC) and other cryptogamic groundcovers
can contribute up to half of the global nitrogen (N) fixation. BSC also
stabilizes the soil (reducing erosion and dust emissions), fixes carbon
(C), retains moisture, and acts as a hotspot of microbial diversity and
activity. Much of the knowledge about how climate change is affecting the
composition and functioning of BSC comes from hot arid and semiarid
regions. The comparatively smaller body of research on BSC from cold and
mesic environments has been primarily observational, for example along
chronosequences after a glacier retreat. Few studies have experimentally
investigated the effects of the environment on BSC from high latitudes.
Such experiments allow unraveling of relationships at a resolution that
can only be achieved by controlling for confounding factors. We measured
short-term (2-4 days) responses of a liverwort-based (Anthelia juratzkana)
BSC from the south of Iceland to a range of temperature, moisture and
light conditions. Warming increased N fixation rates, especially when
moisture was at a saturation level, and only when light was not limiting.
A correlation analysis suggests that increases in N fixation rates were
linked to cyanobacterial abundance on the BSC surface and to the rates of
their metabolic activity. Warming and moisture changes also induced
compositional and structural modification of the bacterial community, with
consequences at the functional level. In contrast to many observations on
BSC from hot drylands, the BSC from our cold and mesic study site is more
limited by low temperature and light than by moisture. Our findings show
possible ways in which BSC from cold and mesic ecosystems can respond to
short-term manifestations of climate change, such as increasingly frequent
heat waves.