Interactions between biogeochemical and management factors explain soil organic carbon in Pyrenean grasslands

Antonio Rodríguez*, Rosa Maria Canals, Josefina Plaixats, Elena Albanell, Haifa Debouk, Jordi Garcia-Pausas, Leticia San Emeterio, Àngela Ribas, Juan José Jimenez, M. Teresa Sebastià

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Grasslands are one of the major sinks of terrestrial soil organic carbon (SOC). Understanding how environmental and management factors drive SOC is challenging because they are scale-dependent, with large-scale drivers affecting SOC both directly and through drivers working at small scales. Here we addressed how regional, landscape and grazing management, soil properties and nutrients, and herbage quality factors affect 20 cm depth SOC stocks in mountain grasslands in the Pyrenees. Taking advantage of the high variety of environmental heterogeneity in the Pyrenees, we built a dataset (n = 128) that comprises a wide range of environmental and management conditions. This was used to understand the relationship between SOC stocks and their drivers considering multiple environments. We found that temperature seasonality (difference between mean summer temperature and mean annual temperature; TSIS) was the most important geophysical driver of SOC in our study, depending on topography and management. TSIS effects on SOC increased in exposed hillsides, slopy areas, and relatively intensively grazed grasslands. Increased TSIS probably favours plant biomass production, particularly at high altitudes, but landscape and grazing management factors regulate the accumulation of this biomass into SOC. Concerning biochemical SOC drivers, we found unexpected interactive effects between grazer type, soil nutrients and herbage quality. Soil N was a crucial SOC driver as expected but modulated by livestock species and neutral detergent fibre contenting plant biomass; herbage recalcitrance effects varied depending on grazer species. These results highlight the gaps in knowledge about SOC drivers in grasslands under different environmental and management conditions. They may also serve to generate testable hypotheses in later/future studies directed to climate change mitigation policies.

Original languageEnglish
Article number314
Pages (from-to)6033-6050
Number of pages18
JournalBiogeosciences
Volume17
Issue number23
DOIs
Publication statusPublished - 3 Dec 2020

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