Articles | Volume 14, issue 9
Biogeosciences, 14, 2513–2525, 2017
Biogeosciences, 14, 2513–2525, 2017

Research article 17 May 2017

Research article | 17 May 2017

Soil nitrogen transformation responses to seasonal precipitation changes are regulated by changes in functional microbial abundance in a subtropical forest

Jie Chen1,2,3,*, Guoliang Xiao1,2,*, Yakov Kuzyakov3,4, G. Darrel Jenerette5, Ying Ma1,2, Wei Liu1, Zhengfeng Wang1, and Weijun Shen1 Jie Chen et al.
  • 1Center for Ecological and Environmental Sciences, South China Botanical Garden, Chinese Academy of Sciences, 723 Xinke Rd. Tianhe District, Guangzhou 510650, PR China
  • 2University of Chinese Academy of Sciences, 19A Yuquan Road, Shijingshan District, Beijing 100049, PR China
  • 3Department of Soil Science of Temperate Ecosystems, University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany
  • 4Department of Agricultural Soil Science, University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany
  • 5Department of Botany and Plant Sciences, Center for Conservation Biology, University of California Riverside, Riverside, CA92521, USA
  • *These authors contributed equally to this work.

Abstract. The frequency of dry-season droughts and wet-season storms has been predicted to increase in subtropical areas in the coming decades. Since subtropical forest soils are significant sources of N2O and NO3, it is important to understand the features and determinants of N transformation responses to the predicted precipitation changes. A precipitation manipulation field experiment was conducted in a subtropical forest to reduce dry-season precipitation and increase wet-season precipitation, with annual precipitation unchanged. Net N mineralization, net nitrification, N2O emission, nitrifying (bacterial and archaeal amoA) and denitrifying (nirK, nirS and nosZ) gene abundance, microbial biomass carbon (MBC), extractable organic carbon (EOC), NO3, NH4+ and soil water content (SWC) were monitored to characterize and explain soil N transformation responses. Dry-season precipitation reduction decreased net nitrification and N mineralization rates by 13–20 %, while wet-season precipitation addition increased both rates by 50 %. More than 20 % of the total variation of net nitrification and N mineralization could be explained by microbial abundance and SWC. Notably, archaeal amoA abundance showed the strongest correlation with net N transformation rates (r  ≥  0.35), suggesting the critical role of archaeal amoA abundance in determining N transformations. Increased net nitrification in the wet season, together with large precipitation events, caused substantial NO3 losses via leaching. However, N2O emission decreased moderately in both dry and wet seasons due to changes in nosZ gene abundance, MBC, net nitrification and SWC (decreased by 10–21 %). We conclude that reducing dry-season precipitation and increasing wet-season precipitation affect soil N transformations through altering functional microbial abundance and MBC, which are further affected by changes in EOC and NH4+ availabilities.

Short summary
We conducted a field manipulation experiment by redistributing 67 % of dry-season rainfall into the wet season while keeping the annual rainfall unchanged in a subtropical forest. Soil net nitrification and N mineralization rates were decreased by 13–20 % in the dry season and increased by 50 % with an accelerated NO3 leaching in the wet season. Functional microbial gene abundance and microbial biomass were the main factors affecting the N-process responses to the rainfall seasonality changes.
Final-revised paper