REGULAR ARTICLE Soil moisture effects on gross nitrification differ between adjacent grassland and forested soils in central Alberta, Canada Yi Cheng & Zu-cong Cai & Jin-bo Zhang & Man Lang & Bruno Mary & Scott X. Chang Received: 26 April 2011 /Accepted: 9 September 2011 /Published online: 24 September 2011 # Springer Science+Business Media B.V. 2011 Abstract Background and aims Changes in soil moisture availability seasonally and as a result of climatic variability would influence soil nitrogen (N) cycling in different land use systems. This study aimed to understand mechanisms of soil moisture availability on gross N transformation rates. Methods A laboratory incubation experiment was conducted to evaluate the effects of soil moisture content (65 vs. 100% water holding capacity, WHC) on gross N transformation rates using the 15 N tracing technique (calculated by the numerical model FLUAZ) in adjacent grassland and forest soils in central Alberta, Canada. Results Gross N mineralization and gross NH 4 + immobilization rates were not influenced by soil moisture content for both soils. Gross nitrification rates were greater at 100 than at 65% WHC only in the forest soil. Denitrification rates during the 9 days of incubation were 2.47 and 4.91 mg N kg -1 soil d -1 in the grassland and forest soils, respectively, at 100% WHC, but were not different from zero at 65% WHC. In the forest soil, both the ratio of gross nitrification to gross NH 4 + immobilization rates (N/IA) and cumula- tive N 2 O emission were lower in the 65 than in the 100% WHC treatment, while in the grassland soil, the N/IA ratio was similar between the two soil moisture content treatments but cumulative N 2 O emission was lower at 65% WHC. Conclusions The effect of soil moisture content on gross nitrification rates differ between forest and grassland soils and decreasing soil moisture content from 100 to 65% WHC reduced N 2 O emissions in both soils. Keywords 15 N tracing technique . FLUAZ . Gross N mineralization . Gross nitrification . Soil moisture content . Denitrification Plant Soil (2012) 352:289–301 DOI 10.1007/s11104-011-0997-2 Responsible Editor: Per Ambus. Y. Cheng : Z.-c. Cai (*) : J.-b. Zhang State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China e-mail: zccai@issas.ac.cn Y. Cheng : S. X. Chang (*) Department of Renewable Resources, University of Alberta, 442 Earth Sciences Building, Edmonton T6G 2E3, Canada e-mail: scott.chang@ualberta.ca M. Lang College of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China B. Mary INRA, Unit Agro-Impact, Site de Laon, Pole du Griffon, 02000 Barenton-Bugny, France