Data from: Predator density outweighs experimental warming effects on short-term carbon and nitrogen loss from arctic shrub litter

Rapid climate change in the Arctic is altering biological communities and
their subsequent effects on ecosystem functioning. For example,
warming-induced shrub expansion accelerates biogeochemical cycles in part
by increasing high-quality litter inputs. Likewise, warming may enable
higher densities of wolf spiders, which are dominant invertebrate
predators whose activities indirectly alter plant litter decomposition
rates. Although shrubs and wolf spiders are responding to climate change
simultaneously, it is unclear how more shrub litter and more spiders
together will influence elemental cycling in Arctic ecosystems. To test
how warming could influence these processes, we used a fully factorial
mesocosm experiment to quantify effects of wolf spiders on litter
decomposition of an expanding species of dwarf deciduous shrub (Betula
nana) under ambient and warmed conditions. We found higher densities of
wolf spiders were consistently associated with more litter mass loss and
more C and N release, regardless of warming treatment, indicating biotic
interactions may be a stronger driver of short-term B. nana litter
decomposition than warming when wolf spiders are present. Our findings
suggest the combined effects of warming-induced shifts in plant and
arthropod communities may further accelerate C and N cycling, which could
cause positive feedbacks on Arctic shrub expansion.