Mitochondrial response to fertilization and warming in dominant tundra species

Background/Question/Methods

The vegetation and soils of the Arctic store large amounts of the world’s carbon and global climate change is altering the balance of this system. To better predict the future effects on carbon storage in northern latitudes, there is a need for a greater understanding of plant responses to environmental change. Examining plant respiration, the process responsible for carbon efflux, will provide necessary information for refining predictions about tundra carbon fluxes. Using plant tissue from two dominant tundra species of different functional types, Eriophorum vaginatum (sedge) and Betula nana (woody shrub), respiration variables were measured from control, fertilization, warming, and fertilization with warming treatment plots at the Arctic LTER at Toolik Lake, AK. The treatment plots aim to simulate future climate change scenarios with warmer ambient temperatures and higher nutrient addition in the soil via increased microbial activity. Oxygen consumption, a correlate for mitochondrial respiration, was quantified using a Clark-type oxygen electrode, while mitochondrial density was quantified using transmission electron microscopy and scaled to cell area.

Results/Conclusions

Oxygen consumption rates varied both across species and treatments, with fertilization leading to increased rates more significantly than warming in all species. Mitochondrial density was significantly increased under fertilization in all species, but warming effects were species specific. The correlation of mitochondrial density and oxygen consumption (R²=0.51) across species indicates a fundamental structural-functional relationship rather than a taxon-specific characteristic. These changes may reflect a shift in plant metabolism and energy balance that may help to explain future the carbon balance at the species and community level under future climate change scenarios.