Affiliation:
1. Soil Resources Department of Environmental Systems Science ETH Zurich Zurich Switzerland
2. Ronin Institute Montclair NJ USA
3. Lawrence Berkeley National Laboratory Berkeley CA USA
4. Department of Soil and Natural Resources Faculty of Agronomy University of Concepción Concepción Chile
5. Department of Green Chemistry and Technology Faculty of Bioscience Engineering Ghent University Gent Belgium
Abstract
AbstractOrganic matter accumulation in soil is understood as the result of the dynamics between mineral‐associated (more decomposed, microbial derived) organic matter and free particulate (less decomposed, plant derived) organic matter. However, from regional to global scales, patterns and drivers behind main soil organic carbon (SOC) fractions are not well understood and remain poorly linked to the pedogenetic variation across soil types. Here, we separated SOC associated with silt‐ and clay‐sized particles (S + C), stable aggregates (>63 μm, SA) and particulate organic matter (POM) from a diverse range of grassland topsoils sampled along a geoclimatic gradient. The relative contribution of the two mineral‐associated fractions (S + C & SA) to SOC differed significantly across the gradient, while POM was never the dominant SOC fraction. Stable aggregates (>63 μm) emerged as the major SOC fraction in carbon‐rich soils. The degree of decomposition of carbon in stable aggregates (>63 μm) was consistently between that of the S + C and POM fractions and did not change along the investigated gradient. In contrast, carbon associated with the S + C fraction was less microbially decomposed in carbon‐rich soils than in carbon‐poor soils. The amount of SOC in the S + C fraction was positively correlated to pedogenic oxide contents and texture, whereas the amount of SOC associated with stable aggregates (>63 μm) was positively correlated to pedogenic oxide contents and negatively to temperature. We present a conceptual summary of our findings, which integrates the role of stable aggregates (>63 μm) with other major SOC fractions and illustrates their changing importance across (soil‐)environmental gradients.
Funder
Fondo Nacional de Desarrollo Científico y Tecnológico
Eidgenössische Technische Hochschule Zürich
Publisher
American Geophysical Union (AGU)
Cited by
2 articles.
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