Land use impact on carbon mineralization in well aerated soils is mainly explained by variations of particulate organic matter rather than of soil structure

• Published in: Soil 2022-04, Vol.8 (1), p.253-267
• Main Authors: Schlüter, Steffen, Roussety, Tim, Rohe, Lena, Guliyev, Vusal, Blagodatskaya, Evgenia, Reitz, Thomas
• Format: Article
• Language: English
• Subjects: Aeration; Agricultural land; Biological activity; Biomass; Bioturbation; Carbon; Carbon cycle; Carbon sequestration; Computed tomography; Cores; Decomposition; Diameters; Environmental conditions; Grasslands; Growing season; Image processing; Image resolution; Land management; Land use; Land use management; Loam soils; Mass; Microbial activity; Microorganisms; Microstructure; Mineralization; Moisture effects; Organic farming; Organic matter; Particulate organic matter; Pasture; Plant growth; Properties; Residues; Respiration; Respirometry; Soil; Soil aeration; Soil compaction; Soil investigations; Soil moisture; Soil stresses; Soil structure; Soil water; Substrates; Tillage; Tomography; Topsoil
• ISSN: 2199-398X; 2199-3971; 2199-398X; 2199-3971
• DOI: 10.5194/soil-8-253-2022

Land use is known to exert a dominant impact on a range of essential soil functions like water retention, carbon sequestration, organic matter cycling and plant growth. At the same time, land use management is known to have a strong influence on soil structure, e.g., through bioturbation, tillage and compaction. However, it is often unclear whether the differences in soil structure are the actual cause of the differences in soil functions or if they only co-occur. This impact of land use (conventional and organic farming, intensive and extensive meadow, extensive pasture) on the relationship between soil structure and short-term carbon mineralization was investigated at the Global Change Exploratory Facility, in Bad Lauchstädt, Germany. Intact topsoil cores (upper 10 cm, n=75) were sampled from all land use types at the early growing season. Soil structure and microbial activity were measured using X-ray-computed tomography and respirometry, respectively. Differences in microstructural properties between land uses were small in comparison to the variation within land uses. The most striking difference between land uses was larger macropore diameters in grassland soils due to the presence of large biopores that are periodically destroyed in croplands. Grasslands had larger amounts of particulate organic matter (POM), including root biomass, and also greater microbial activity than croplands, both in terms of basal respiration and rate of carbon mineralization during growth. Basal respiration among soil cores varied by more than 1 order of magnitude (0.08–1.42 µg CO2-C h−1 g−1 soil) and was best explained by POM mass (R2=0.53, p