B21F-0536
Contrasting Responses of Ecosystem Carbon Gain (Input) and Soil Carbon Efflux (Output) to Warming and Drought Across a European Aridity Gradient
Tuesday, 15 December 2015
Poster Hall (Moscone South)
Sabine Reinsch1, Jack Cosby1, Eva Koehler1, Giovanbattista de Dato2, Marc Estiarte3, Gabriele Guidolotti4, Edith Kovacs-Lang5, Jeffrey Dukes6, György Kröel-Dulay5, Klaus Stenberg Larsen7, Eszter Lellei-Kovács5, Dario Liberati8, Johannes Ransijn9, Inger K Schmidt10, Andrew R Smith11, Alwyn Sowerby1 and Bridget Emmett1, (1)Centre for Ecology and Hydrology, Bangor, United Kingdom, (2)Council for Agricultural Research and Economics, Arezzo, Italy, (3)CREAF, Cerdanyola Del Valle, Spain, (4)CNR-IBAF, Porano, Italy, (5)Institute of Ecology and Botany, MTA Centre for Ecological Research, Vácrátót, Hungary, (6)Purdue University, Department of Forestry and Natural Resources, West Lafayette, IN, United States, (7)University of Copenhagen, Copenhagen, Denmark, (8)University of Tuscia, Viterbo, Italy, (9)University of Copenhagen, Dept Geosci & Nat Resources, Copenhagen, Denmark, (10)Copenhagen University, Department of Geoscience and Natural Resource Management, Copenhagen, Denmark, (11)Bangor University, Bangor, United Kingdom
Abstract:
Understanding the relationship between aboveground and belowground processes are crucial to understand if we are to forecast feedbacks between terrestrial carbon (C) dynamics and future climate. To test if climate induced changes in annual aboveground net primary production (ANPP) will drive changes in C loss by soil respiration (Rs) we integrated data across a European temperature and precipitation gradient. Six European shrublands were exposed to year-round, night time warming (+1.5 oC) or repeated drought (-30% annual rain) during the plants growth season for over a decade, using an identical experimental approach. As a result, drought reduced ecosystem C gain as ANPP by 50% (compared to an untreated control) at the driest xeric site with effects reducing in intensity across the aridity gradient to a 15% ANPP-C gain at the wettest hydric site (slope=1.2, R2=0.76). In contrast, reductions in Rs-C loss were of a lower magnitude (0-15%) and increased in intensity across the aridity gradient (slope=-0.44, R2=0.76) if the hydric site was excluded. These results suggest (i) above and belowground C fluxes responses do not track each other in response to drought and (ii) whilst ANPP at our hydric sites follows that predicted from an aridity gradient, Rs responses did not. Results from the warming treatments were generally of lower magnitude and opposite direction indicating different mechanisms were driving responses. Overall, these results suggest that ANPP is more sensitive than Rs to climate stresses and soil respiration C fluxes are not predictable from changes in plant productivity. Indirect effects on soil properties and/or microbial communities need to be explored. As we observed no acclimation of either ANPP or Rs after over a decade of treatments, feedbacks between the terrestrial C cycle and climate may not weaken over decadal timescales at larger, continental scales.
