Hourly and daily rainfall intensification causes opposing effects on C and N emissions, storage, and leaching in dry and wet grasslands

Journal Article · 25 June 2019 · Biogeochemistry

DOI: https://doi.org/10.1007/s10533-019-00580-7 · OSTI ID:1580888

Tang, Fiona H. M.  ^[1]; Riley, William J. ^[2]; Maggi, Federico ^[1]

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1. Univ. of Sydney, NSW (Australia)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Climate change is expected to alter hourly and daily rainfall regimes and, in turn, the dynamics of ecosystem processes controlling greenhouse gas emissions that affect climate. Here, we investigate the effects of expected twenty-first century changes in hourly and daily rainfall on soil carbon and nitrogen emissions, soil organic matter (SOM) stocks, and leaching using a coupled mechanistic carbon and nitrogen soil biogeochemical model (BAMS2). The model represents various abiotic and biotic processes involving 11 SOM pools. These processes include fungal depolymerization, heterotrophic bacterial mineralization, nitrification, denitrification, microbial mortality, necromass decomposition, microbial response to water stress, protection, aqueous advection and diffusion, aqueous complexation, and gaseous dissolution. Multi-decadal modeling with varying rainfall patterns was conducted on nine Australian grasslands in tropical, temperate, and semi-arid regions. Our results show that annual CO₂ emissions in the semi-arid grasslands increase by more than 20% with a 20% increase in annual rainfall (with no changes in the rainfall timing), but the tropical grasslands have opposite trends. A 20% increase in annual rainfall also increases annual N₂O and NO emissions in the semi-arid grasslands by more than 10% but decreases emissions by at least 25% in the temperate grasslands. When subjected to low frequency and high magnitude daily rainfall events with unchanged annual totals, the semi-arid grasslands are the most sensitive, but changes in annual CO₂ emissions and SOM stocks are less than 5 %. Finally, intensification of hourly rainfall did not significantly alter CO₂ emissions and SOM stocks but changed annual NH₃ emissions in the tropical grasslands by more than 300%.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1580888
• Journal Information: Biogeochemistry, Journal Name: Biogeochemistry Journal Issue: 2 Vol. 144; ISSN 0168-2563
• Publisher: SpringerCopyright Statement
• Country of Publication: United States
• Language: English