Bryophyte microecosystem experiment

Ecosystems face multiple, potentially interacting, anthropogenic pressures
that can modify biodiversity and ecosystem functioning. Using a
bryophyte-microarthropod microecosystem we tested the combined effects of
habitat loss, episodic heat-shocks and an introduced non-native apex
predator on ecosystem function (chlorophyll fluorescence as an indicator
of photosystem II function) and microarthropod communities (abundance and
body size). Photosynthetic function was degraded by the sequence of
heat-shock episodes, but unaffected by microecosystem patch size or
top-down pressure from the introduced predator. In small microecosystem
patches without the non-native predator, Acari abundance decreased with
heat-shock frequency, while Collembola abundance increased. These trends
disappeared in larger microecosystem patches or when predators were
introduced, although Acari abundance was lower in large patches that
underwent heat shocks and were exposed to the predator. Mean assemblage
body length (Collembola) was reduced independently in small microecosystem
patches and with greater heat-shock frequency. Our experimental simulation
of episodic heat waves, habitat loss and non-native predation pressure in
microecosystems produced evidence of individual and potentially
synergistic and antagonistic effects on ecosystem function and
microarthropod communities. Such complex outcomes of interactions between
multiple stressors need to be considered when assessing anthropogenic
risks for biota and ecosystem functioning.