Greenhouse gas emissions from riparian systems as affected by hydrological extremes: a mini-review

Increasing atmospheric greenhouse gas (GHG) concentrations causes global temperature rising as well as extreme hydrological events. Understanding the effects of climate change-induced severe hydrological events such as flooding and drought on soil properties and subsequent GHG emissions from soil has enabled scientists to optimize different land management and global warming potential mitigation of a system. Flooding and drought dynamics affect soil physicochemical properties and GHG emissions specifically from land use systems that are adjacent to streams like riparian buffers. Drivers of soil GHG emissions and the effect of extreme hydrological events on the GHG flux from riparian systems in three climate zones (Mediterranean, temperate, and tropical/subtropical) were investigated in this review utilizing Web of Science and Scopus databases. Wet soil conditions contribute more to global warming (7.2 Mg CO2eq-C ha-1 h-1) than dry soils (2.1 Mg CO2eq-C ha-1 h-1) in riparian systems. Temperate riparian systems showed the greatest soil N2O emissions (0.7 mg N2O-N m-2 h-1) after flooding events/during wet seasons. The greatest CH4 (12 mg CH4-C m-2 h-1) and CO2 (15.2 g CO2-C m-2 d-1) flux from wet soils were observed in tropical/subtropical riparian systems. Greater soil inorganic N content (NO3- and NH4+) in temperate riparian systems is responsible for the higher soil N2O flux during wet seasons. Intense precipitation events and greater soil carbon content in tropical/subtropical riparian systems contributed to more CO2 and CH4 emissions relative to the temperate and Mediterranean riparian systems.