Time-dependent regulation of respiration is widespread across plant evolution.

Establishing the temperature dependence of respiration is critical for accurate predictions of the global carbon cycle under climate change. Diurnal temperature fluctuations, or changes in substrate availability, lead to variations in leaf respiration. Additionally, recent studies hint that the thermal sensitivity of respiration could be time-dependent. However, the role for endogenous processes, independent from substrate availability, as drivers of temporal changes in the sensitivity of respiration to temperature across phylogenies has not yet been addressed. Here, we examined the diurnal variation in the response of respiration to temperatures (R-T relationship) for different lycophyte, fern, gymnosperm and angiosperm species. We tested whether time-dependent changes in the R-T relationship would impact leaf level respiration modelling. We hypothesized that interactions between endogenous processes, like the circadian clock, and leaf respiration would be independent from changes in substrate availability. Overall, we observed a time-dependent sensitivity in the R-T relationship across phylogenies, independent of temperature, that affected modelling parameters. These results are compatible with circadian gating of respiration, but further studies should analyse the possible involvement of the clock. Our results indicate time-dependent regulation of respiration might be widespread across phylogenies, and that endogenous regulation of respiration is likely affecting leaf-level respiration fluxes.

North-south antiphase of wildfire activity across the pyroregions of continental China driven by NAO and the Antarctic oscillation.

Wildfires are a natural disturbance in many parts of the world, but fire regimes are changing as a result of anthropogenic pressures. A key uncertainty towards anticipating future changes in burned area lies in understanding the effects of climate teleconnections (CTs). Here we test how different CTs impact burned area in China, a large country comprising different biomes and where similar fire-suppression and post-fire afforestation policies are implemented. We observed diverging temporal trends in burned area across the different pyroregions of China, from increases in the Northeastern grasslands and mixed forests pyroregion to decreases in the Southern tropical forests pyroregion. This North-South antiphase in fire activity was being partly driven by joint effects of the North Atlantic Oscillation and the Antarctic Oscillation, which exerted contrasting effects on fire weather across latitude. El Niño Southern Oscillation and the other examined teleconnections had minor effects over burned area. The increasing burned area in the NE-mixed forests pyroregion indicates that mega-fires may increase under global warming but their occurrence may be modulated by potential strengthening or weakening of NAO and AAO.