Soil carbon stocks in temperate grasslands differ strongly across sites but are insensitive to decade‐long fertilization

Abstract

Copyright statement: This manuscript has been authored by UT-Battelle, LLC, under contract no. DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downl oads/doe-publi cacce ss-plan).

Nitrogen increases early‐stage and slows late‐stage decomposition across diverse grasslands

“…By contrast, larger slowly decomposing litter fractions could promote he accumulation of particulate organic matter (POM) and total SOM (Cotrufo et al, 2015). Interestingly, a study conducted in nine North American NutNet sites found no effects of N on MAOM or POM (Keller et al, 2022), raising uncertainty about whether differential effects of N over the course of litter decomposition have consistent consequences for SOM.…”

“…The effects of N deposition on grassland C cycling will likely depend on the supplies of other nutrients, since NPP in grasslands is often co‐limited by multiple nutrients, with N limitation more prevalent at higher latitudes (Cleland et al, 2019; Du et al, 2020; Fay et al, 2015). On the other hand, grassland surface soil C stocks are relatively insensitive to N and P addition, with strong but unexplained response variability across sites (Crowther et al, 2019; Keller et al, 2022), but increase with short‐term addition of K with micronutrients (Crowther et al, 2019). This inconsistency between nutrient effects on plant biomass production (NPP) and soil C accumulation indicates a gap in understanding of nutrient effects on litter and soil organic matter (SOM) decomposition across diverse grasslands.…”

Realistic rates of nitrogen addition increase carbon flux rates but do not change soil carbon stocks in a temperate grassland

“…Therefore, N has the potential to influence grassland C accumulation by concurrently changing plant biomass, detritus, and rates of decomposition. Adding N alone can have positive, negative, and neutral effects on soil C (e.g., Crowther et al, 2019; Keller et al, 2021), even when N increases aboveground plant biomass accumulation (Fay et al, 2015) and reduces the rate of litter and soil organic matter (SOM) decomposition (Gill et al, 2021; e.g., Riggs et al, 2015; Riggs & Hobbie, 2016).…”

Impacts of nutrient addition on soil carbon and nitrogen stoichiometry and stability in globally-distributed grasslands

“…Grasslands are crucial areas for SOM storage, covering 30-40% of the global land surface (Reynolds 2005;Petri et al 2009) and storing 16% of global soil C (Anderson 1991). Previous research has revealed that grassland SOM C is affected by nutrient availability, depending on environmental conditions (Yue et al 2017;Crowther et al 2019;Keller et al 2021). However, investigating SOM C and N coupling and distribution between functionally different pools of SOM can provide new insight for soil responses to global change, such as model constraints for microbial metabolism or vulnerability of soil C to warming (Buchkowski et al 2019;Rocci et al 2021).…”