BG Biogeosciences BG Biogeosciences 1726-4189 Copernicus Publications Göttingen, Germany 10.5194/bg-10-8129-2013 Extreme rainfall events can alter inter-annual biomass responses to water and N enrichment Kong D. L. 1 5 Lü X. T. https://orcid.org/0000-0001-5571-1895 2 5 Jiang L. L. 3 5 Wu H. F. 1 Miao Y. 1 Kardol P. 4 State Key Laboratory of Cotton Biology, College of Life Sciences, Henan University, Kaifeng 475004, China State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, 110016, Shenyang, China Institute of Tibetan Plateau Research, Chinese Academy of Sciences, 100101, Beijing, China Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 90183, Umeå, Sweden These authors contributed equally to this work. 11 12 2013 10 12 8129 8138 Copyright: © 2013 D. L. Kong et al. 2013 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://bg.copernicus.org/articles/10/8129/2013/bg-10-8129-2013.html The full text article is available as a PDF file from https://bg.copernicus.org/articles/10/8129/2013/bg-10-8129-2013.pdf

Water availability has profound effects on plant growth and productivity in temperate and semiarid grasslands. However, it remains unclear how variation of inter-annual precipitation by extreme rainfall events will alter the aboveground and belowground responses of plants, and how these responses may be contingent on N availability. In this study, we examined the interactive effects of inter-annual precipitation variation and N addition on aboveground and live fine root biomass of a semiarid grassland in northern China for two consecutive years (2007 and 2008). Inter-annual variation in precipitation resulting mainly from the occurrence of extreme rainfall events in 2008 significantly affected above- and belowground plant biomass responses to water addition. In addition, variation of inter-annual precipitation by this extreme rainfall event suppressed plant responses to nitrogen addition and reduced the interaction effects between water and nitrogen addition. These effects of inter-annual precipitation fluctuation could be attributed to the negative influence of the extreme rainfall event on soil N and water availability, ultimately reducing plant rainfall use efficiency and nitrogen use efficiency. In conclusion, our results suggest ecosystem responses to water and N enrichment could be altered by inter-annual variation of precipitation regime caused by the naturally occurring extreme rainfall events.

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