High late-summer rainfall in a temperate forest ecosystem impacts soil methane uptake and microbial enzyme activities
Katy J. Faulkner 1, Simon Oakley 2, Niall P. McNamara 2, Christopher J. van der Gast 3, Sami Ullah 4, Gary D. Bending 1
1 School of Life Sciences, University of Warwick, CV4 7AL, *katy.faulkner@warwick.ac.uk
2 UK Centre for Ecology & Hydrology, Lancaster, LA1 4AP
3 Department of Life Sciences, Manchester Metropolitan University, M1 5GD
4 School of Geography, Earth and Environmental Sciences, University of Birmingham, B15 2TT.
Climate change is expected to alter global precipitation patterns, with unknown impacts on biodiversity and ecosystem functioning. Temperate forests are one of the largest terrestrial carbon stocks, acting as sinks for greenhouse gases such as carbon dioxide and methane thus playing a major role in ameliorating global warming. Predicted changes to precipitation intensity and timing under future climates are likely to result in the alteration of soil moisture dynamics in forest soils. This will impact soil microbial functions, when the soil environment switches from oxic to anoxic conditions with consequent effects on microbial metabolism and microbially-mediated nutrient cycling. The impacts of these changes on the terrestrial carbon balance is currently not known. Using an in situ peristaltic pumping system set up in a mature temperate forest in Staffordshire (Birmingham Institute of Forest Research, UK), soil moisture was continuously elevated by ~ 25% in treatment plots with artificial rainwater. Here we show that a 4-week elevation in rainfall and soil moisture had significant impacts on soil functioning. The soil methane sink was significantly reduced in the high-rainfall treated soils by ~ 45%, resulting in greater methane accumulation in the atmosphere. The activities of soil extracellular enzymes, involved in the breakdown of organic carbon, nitrogen and phosphorus compounds, were reduced during the high-rainfall treatment. Despite alteration to soil enzymatic activity, the soil carbon dioxide flux was unchanged. Detecting changes in soil microbial respiration may be confounded by the coinciding contributions of root respiration to the overall flux. Our results demonstrate that important soil functional changes occur during high precipitation events, with potential impacts on temperate forest biogeochemical cycling.