| Institution: | (1) Centre for Ecology and Hydrology–Bangor, Orton Building, Deiniol Rd., Bangor, Gwynedd LL572UP, United Kingdom;(2) RISØ National Laboratory, P.O. Box 49, DK-4000 Roskilde, Denmark;(3) Plant Ecophysiological Unit, CSIC–CEAB–CREAF, Edifici C, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain;(4) Center for Geo-ecological Research (ICG), Institute for Biodiversity and Ecosystem Dynamics (IBED)–Physical Geography, University of Amsterdam, Nieuwe Achtergracht 166, 1018, WV Amsterdam, The Netherlands;;(5) Danish Institute of Agricultural Sciences, P.O. Box 102, DK-5792 Aarslev, Denmark;(6) Countryside Council for Wales, Penrhos Road, Bangor, Gwynedd, United Kingdom;(7) Danish Forest and Landscape Research Institute, Hørshom Kongevej 11, DK-2970 Hørsholm, Denmark |
| Abstract: | Predicted changes in climate may affect key soil processes such as respiration and net nitrogen (N) mineralization and thus key ecosystem functions such as carbon (C) storage and nutrient availability. To identify the sensitivity of shrubland soils to predicted climate changes, we have carried out experimental manipulations involving ecosystem warming and prolonged summer drought in ericaceous shrublands across a European climate gradient. We used retractable covers to create artificial nighttime warming and prolonged summer drought to 20-m2 experimental plots. Combining the data from across the environmental gradient with the results from the manipulation experiments provides evidence for strong climate controls on soil respiration, net N mineralization and nitrification, and litter decomposition. Trends of 0%–19% increases of soil respiration in response to warming and decreases of 3%–29% in response to drought were observed. Across the environmental gradient and below soil temperatures of 20°C at a depth of 5–10 cm, a mean Q10 of 4.1 in respiration rates was observed although this varied from 2.4 to 7.0 between sites. Highest Q10 values were observed in Spain and the UK and were therefore not correlated with soil temperature. A trend of increased accumulated surface litter mass loss was observed with experimental warming (2%– 22%) but there was no consistent response to experimental drought. In contrast to soil respiration and decomposition, variability in net N mineralization was best explained by soil moisture rather than temperature. When water was neither limiting or in excess, a Q10 of 1.5 was observed for net N mineralization rates. These data suggest that key soil processes will be differentially affected by predicted changes in rainfall pattern and temperature and the net effect on ecosystem functioning will be difficult to predict without a greater understanding of the controls underlying the sensitivity of soils to climate variables. |
