Patterns and drivers of global gross nitrogen mineralization in soils

Abstract

Soil gross nitrogen (N) mineralization (GNM), a key microbial process in the global N cycle, is mainly controlled by climate and soil properties. This study provides for the first time a comprehensive analysis of the role of soil physicochemical properties and climate and their interactions with soil microbial biomass (MB) in controlling GNM globally. Through a meta‐analysis of 970 observations from 337 published papers from various ecosystems, we found that GNM was positively correlated with MB, total carbon, total N and precipitation, and negatively correlated with bulk density (BD) and soil pH. Our multivariate analysis and structural equation modeling revealed that GNM is driven by MB and dominantly influenced by BD and precipitation. The higher total N accelerates GNM via increasing MB. The decrease in BD stimulates GNM via increasing total N and MB, whereas higher precipitation stimulates GNM via increasing total N. Moreover, the GNM varies with ecosystem type, being greater in forests and grasslands with high total carbon and MB contents and low BD and pH compared to croplands. The highest GNM was observed in tropical wet soils that receive high precipitation, which increases the supply of soil substrate (total N) to microbes. Our findings suggest that anthropogenic activities that affect soil microbial population size, BD, soil substrate availability, or soil pH may interact with changes in precipitation regime and land use to influence GNM, which may ultimately affect ecosystem productivity and N loss to the environment.

Global gross nitrification rates are dominantly driven by soil carbon‐to‐nitrogen stoichiometry and total nitrogen

“…Moreover, MB has a quick turnover rate of 0.84 year −1 and is the dominant force of the soil N cycle (Goyal et al, 1993; Inubushi & Acquaye, 2004). Soil microbes control gross N mineralization (Elrys et al, 2021), and ultimately, stimulate GN. These findings show that any changes in soil substrate quantity (total N) and quality (C:N and MB) due to anthropogenic activities may influence GN, and ultimately, NO 3 − ‐N availability.…”

“…Our global synthesis confirmed this point of view as soil total N drives GHN and is also an important factor controlling GAN. Soils with a higher total N content usually have a higher MB (Elrys et al, 2021) and higher AOB and AOA abundances (Cai et al, 2020), stimulating GN rates. Soil total N increased GN probably by directly providing NH 4 + substrate for soil microbes (Cai et al, 2020).…”

“…Precipitation and its impact on soil water content could influence the soil substrate quality, either by alterations resulting from decomposition processes, or via a shift in plant community structure, and consequently incoming litter quality (Zhao et al, 2017). On a global scale, soils with additional substrates (e.g., total N) have greater MB (Elrys et al, 2021; Serna‐Chavez et al, 2013). In grasslands, increased MAP caused a 20% increase in MB (Liu et al, 2009).…”

“…Soils with a low bulk density have a high soil porosity, improving the soil capacity to retain moisture but at the same time provide soil oxygen, thus enhancing the activity of soil microorganisms (Ishak et al, 2014). Soil bulk density, which negatively affects MB and soil total N, was higher in croplands than in forests (Elrys et al, 2021). Soil aggregate stability has increased dramatically with the change of land‐use from croplands to forests (Delelegn et al, 2017).…”

“…Across a wide range of forests, soil total N has been suggested to be the key determinant of GN (Wang et al, 2018). Moreover, soil C:N has a profound impact on GN (Baldos et al, 2015; Wang et al, 2018) through its effect on the abundances of ammonia‐oxidizing bacteria (AOB) and archaea (AOA) (Xiao et al, 2021) and rates of gross N mineralization (Elrys et al, 2021). Nitrification itself can occur as autotrophic (GAN) or heterotrophic (GHN) nitrification.…”