Dynamics of ¹³C‐labeled mustard litter (Sinapis alba) in particle‐size and aggregate fractions in an agricultural cropland with high‐ and low‐yield areas

Abstract

The application of 13 C-labeled litter enables to study decomposition processes as well as the allocation of litter-derived carbon to different soil C pools. 13 Carbon-labeled mustard litter was used in order to compare decomposition processes in an agricultural cropland with high-yield (HY) and low-yield (LY) areas, the latter being characterized by a finer texture and a lower organic-C (OC) content. After tracer application, 13 C concentrations were monitored in topsoil samples in particulate organic matter (POM) and in fine mineral fractions (silt-and clay-sized fractions). After 568 d, approximately 5% and 10% of the initial 13 C amount were found in POM fractions of LY and HY areas, respectively. Higher amounts were found in POM occluded in aggregates than in free POM. Medium-term (0.5-2 y) storage of the initial 13 C in fine silt-and clay-sized fractions amounts to 10% in HY and LY soils, with faster enrichment but also faster disappearance of the 13 C signal from LY soils. Amounts of 80%-90% of the added 13 C were mineralized or leached in the observed period. Decomposition of free POM was faster in HY than in LY areas during the first year, but the remaining 13 C amounts in occluded-POM fractions were higher in HY soils after 568 d. High-yield and low-yield areas showed different 13 C dynamics in fine mineral fractions. In LY soils, 13 C amounts and concentrations in mineral-associated fractions increased within 160 d after application and decreased in the following time period. In HY areas, a significant increase in 13 C amounts did not occur until after 568 d. The results indicate initially faster decomposition processes in HY than in LY areas due to different soil conditions, such as soil texture and water regime. The higher silt and clay contents of LY areas seem to promote a faster aggregate formation and turnover, leading to a closer contact between POM and mineral surfaces in this area. This favors the OC storage in fine mineral fractions in the medium term. Lower aggregate formation and turnover in the coarser textured HY soil leads to a delayed C stabilization in silt-and clay-sized fractions.

Grazing changes topography-controlled topsoil properties and their interaction on different spatial scales in a semi-arid grassland of Inner Mongolia, P.R. China

“…The SOC balance of these soils is maintained by root and shoot litter inputs which enter the soil as particulate organic matter (POM). Characterised by high turnover rates and great lability, POM functions as an indicator for high C input and SOC turnover rates in different land use systems (Buyanovsky et al 1994;Kölbl et al 2006Kölbl et al , 2007Noellemeyer et al 2006), especially in systems characterised by a perennial grass sward (Dubeux et al 2006).…”

Simulating decomposition of 14C‐labelled fresh organic matter in bulk soil and soil particle fractions at various temperatures and moisture contents

“…It is worth noting that the is even greater than the initial 14 C distribution in this soil fraction. Therefore, it can be assumed that kinetic processes not only cause a decrease in the C content but also a redistribution of C from larger to smaller soil particle‐size fractions, which has already been observed by Buyanovsky et al (1994), Aita et al (1997), Anger & Recous (1997), Stemmer et al (1999), Gale & Cambardella (2000), Kölbl et al (2007) and others. Additionally, Figure 2 indicates that 70–80% of the residual 14 C is located in the 0–53‐µm soil particle fraction at the end of the incubation, compared with only 30% at the beginning of the experiments.…”

“…However, a concomitant integration of small FOM in soil aggregates increases its physical protection against decomposition (Sollins et al , 1996; Christensen, 2001; Six et al , 2002). Results on the effects of soil particle‐size fractions on the distribution and decomposition kinetics support these mechanisms under field and laboratory conditions (Buyanovsky et al , 1994; Balesdent, 1996; Aita et al , 1997; Stemmer et al , 1999; Gale & Cambardella, 2000; John et al , 2005; Kölbl et al , 2007). The decomposition results are generally fitted by single first‐order kinetics or a combination of parallel first‐order kinetics (Jenkinson, 1977).…”

Reply on RC1

“…Reported negative values for any of the considered quantities were removed, but if primary data showed major inconsistencies (e.g., negative fractions of remaining residues) that could not be explained even after contacting the authors, the whole study was excluded. After this screening, the database contained data from 39 published articles (Magid et al, 2002;Kölbl et al, 2006Kölbl et al, , 2007Cotrufo et al, 2015Cotrufo et al, , 2022Throckmorton et al, 2015;Haddix et al, 2016Haddix et al, , 2020Lian et al, 2016;Pries et al, 2017Pries et al, , 2018Wang et al, 2017;Lavallee et al, 2018;Mitchell et al, 2018;Fang et al, 2019;Fulton-Smith and Cotrufo, 2019;Sokol et al, 2019;Liebmann et al, 2020;Su et al, 2020;Almeida et al, 2021;Ferreira et al, Xu et al, 2022;Canisares et al, 2023;Cheng et al, 2023;Duan et al, 2023;Kou et al, 2023b;Lyu et al, 2023;Neupane et al, 2023;Poeplau et al, 2023;Schiedung et al, 2023;Even and Cotrufo, 2024). Some datasets were directly accessible from online repositories (Buckeridge, 2021;Craig et al, 2021;Huys et al, 2022b;Kou et al, 2023a;Ridgeway et al, 2023a).…”