Soil net nitrogen mineralisation across global grasslands.

Area of Science:

• Soil Science
• Ecology
• Biogeochemistry

Background:

• Soil nitrogen mineralisation (N_min) converts organic nitrogen to inorganic forms, vital for soil productivity and nutrient cycling.
• The balance between nitrogen mineralisation and immobilisation (net N_min) is influenced by soil properties and climate.
• Global assessments of net N_min often rely on laboratory data, limiting understanding of field conditions and real-world soil functioning.

Purpose of the Study:

• To investigate the drivers of realised (field) and potential (laboratory) soil net nitrogen mineralisation across global grasslands.
• To compare field-measured N_min with laboratory-based potential N_min.
• To develop a framework for predicting realised N_min using readily available soil and climate data.

Main Methods:

• Conducted field and laboratory incubations of soil samples from 30 grassland sites worldwide.
• Analyzed soil properties (e.g., microbial biomass, clay content, bulk density) and climatic variables (e.g., temperature, precipitation).
• Utilized statistical models to identify key drivers of realised and potential net N_min.

Main Results:

• Realised net N_min in grasslands was primarily explained by temperature during the wettest quarter, microbial biomass, clay content, and bulk density.
• Potential N_min showed a weak correlation with realised N_min.
• Combining potential N_min with soil and climatic variables improved the prediction of realised net N_min.

Conclusions:

• Field conditions significantly regulate soil nitrogen mineralisation, with distinct drivers compared to laboratory settings.
• Potential N_min data can be enhanced with soil and climate information to better predict realised N_min.
• This study offers critical insights into global soil nitrogen cycling under field conditions.