Soil N2O emission in Cinnamomum camphora plantations along an urbanization gradient altered by changes in litter input and microbial community composition

Urbanization can accelerate climate change by increasing soil N2O emission while reducing CH4 uptake

“…In addition to climate conditions, greater atmospheric N deposition (due to fossil fuel combustion and industrial processes) as well as anthropogenic management (e.g., N fertilization and irrigation) in urban greenspaces can result in increased abundances and activity of ammonia oxidizer and denitrifier populations, and higher soil inorganic N concentrations and soil TN content [as shown in this and previous (Dutt & Tanwar, 2020) studies]. These changes in soil nutrient concentrations and the soil microbiome in urban soils support greater rates of nitrification and denitrification and subsequent N 2 O emissions (Rao et al, 2014; Xu et al, 2022; Zhang, Zhang, et al, 2022). Higher rates of N cycling in urban soils usually leads to a reduction in CH 4 uptake by suppressing methanotroph populations and activities (Bodelier, 2011; Costa & Groffman, 2013; Kravchenko et al, 2002; Tate, 2015; Wu et al, 2022).…”

“…Urbanization significantly alters these factors due to heat island effects, increased atmospheric N deposition as a result of industrial and traffic emissions, and soil compaction and redistribution in the course of urban landscaping. This alteration affects C and N biogeochemical cycles in urban soils and associated production and consumption of CH 4 and N 2 O (Groffman et al, 2009; Kaye et al, 2006; Ni & Groffman, 2018; Xu et al, 2022). Previous studies have reported low or full inhibition of soil atmospheric CH 4 uptake in urban forests and lawns in China and the United States due to increases in soil bulk density (BD), which constrains diffusion of atmospheric CH 4 to sites of microbial CH 4 uptake by methanotrophs, or increases in soil N availability, which may directly inhibit CH 4 uptake (Groffman & Pouyat, 2009; Kaye et al, 2004; Zhang et al, 2014).…”

“…With regard to soil N 2 O emissions from urban greenspaces, contradictory results have been reported. While some studies have reported low N 2 O emissions from urban soils (e.g., Groffman et al, 2009), other studies have reported high fluxes, especially if soils were fertilized (e.g., lawns or golf courses) (Kaye et al, 2004; van Delden et al, 2018; Xu et al, 2022). Dutt and Tanwar (2020) conducted a meta‐analysis to evaluate the effect of fertilizer application on lawn N 2 O emissions, and found that lawn N 2 O emissions from fertilized plots were 41% (or 0.29 g N m −2 year −1 ) higher than those from non‐fertilized controls.…”