Is sulfur storage in grassland topsoils controlled by the same factors as carbon and nitrogen storage? A global meta-analysis

Abstract

As one of the major global biomes, grasslands contribute substantially to the storage of soil organic carbon (SOC) and macroelements such as nitrogen (N) and sulfur (S). However, while SOC and N storage in grassland soils have been extensively studied in the past, similar assessments for S are missing. We conducted a meta-analysis to determine which soil, climate or management parameters were most relevant in controlling S storage compared to SOC and N storage. We collected data on SOC, total N, and total S concentrations in grassland topsoils from previously published studies, along with data on mean annual temperature, mean annual precipitation, soil pH, and soil texture. We additionally classified conditions at each site according to Reference Soil Groups, Koeppen climate classes and management systems. Our data set includes a total of 248 observations from 30 studies in 15 different countries published between 1958 and 2024. We generally observed similar patterns in SOC, N, and S storage, with Reference Soil Group and Koeppen climate class as the most relevant parameters determining total element concentration or element ratios in grassland topsoils, while the type of grassland management did not consistently affect element concentrations and ratios. However, we observed that S concentration was increased especially in soils that were influenced by geogenic inputs of S from the parent material or with groundwater influx, with corresponding changes in C:S and N:S ratios. This resulted in larger variability in S storage in grassland soils compared to SOC and N storage.