Priming effects on labile and stable soil organic carbon decomposition: Pulse dynamics over two years

Abstract

Soil organic carbon (SOC) is a major component in the global carbon cycle. Yet how input of plant litter may influence the loss of SOC through a phenomenon called priming effect remains highly uncertain. Most published results about the priming effect came from short-term investigations for a few weeks or at the most for a few months in duration. The priming effect has not been studied at the annual time scale. In this study for 815 days, we investigated the priming effect of added maize leaves on SOC decomposition of two soil types and two treatments (bare fallow for 23 years, and adjacent old-field, represent stable and relatively labile SOC, respectively) of SOC stabilities within each soil type, using a natural 13C-isotope method. Results showed that the variation of the priming effect through time had three distinctive phases for all soils: (1) a strong negative priming phase during the first period (≈0–90 days); (2) a pulse of positive priming phase in the middle (≈70–160 and 140–350 days for soils from Hailun and Shenyang stations, respectively); and (3) a relatively stabilized phase of priming during the last stage of the incubation (>160 days and >350 days for soils from Hailun and Shenyang stations, respectively). Because of major differences in soil properties, the two soil types produced different cumulative priming effects at the end of the experiment, a positive priming effect of 3–7% for the Mollisol and a negative priming effect of 4–8% for the Alfisol. Although soil types and measurement times modulated most of the variability of the priming effect, relative SOC stabilities also influenced the priming effect for a particular soil type and at a particular dynamic phase. The stable SOC from the bare fallow treatment tended to produce a narrower variability during the first phase of negative priming and also during the second phase of positive priming. Averaged over the entire experiment, the stable SOC (i.e., the bare fallow) was at least as responsive to priming as the relatively labile SOC (i.e., the old-field) if not more responsive. The annual time scale of our experiment allowed us to demonstrate the three distinctive phases of the priming effect. Our results highlight the importance of studying the priming effect by investigating the temporal dynamics over longer time scales.

Carbon mineralization, biological indicators, and phytotoxicity to assess the impact of urban sewage sludge on two light‐textured soils in a microcosm

“…Several studies have reported on immediate C mineralization after sludge application (Armenta, Vaca, Lugo, & Del Aguila, 2012;Franco-Otero, Soler-Rovira, Hernandez, Lopez-de-Sa, & Plaza, 2012;Hamdi, Benzarti, Manusadžianas, Aoyama, & Jedidi, 2007b;Obriot et al, 2016) as well as for other exogenous organic matter (Balota, Machineski, & Matos, 2012;Poulsen, Magid, Luxhoi, & De Neergaard, 2013). The same phases of cumulative CO 2 variation with time were previously described; an intense microbial activity during the first 10-16 d of incubation, called the "priming effect," corresponds to the rapid degradation of easily metabolized substrates already present in soil or brought along with the USS (Zhang, Han, Yu, Wang, & Cheng, 2017).…”

Soil quality indicators as influenced by 5-year diversified and monoculture cropping systems

“…Compared with CWC and CWN, HWC and HWN have higher biodegradability rate and can supply higher nutrients and energy for plant and microbes (Gregorich et al ., 2003). The findings in the current study showed that all labile C and N fractions under all cropping systems had similar performance in both years (Table 2), also associated with the turnover rate of labile C and N fractions (Jandl and Sollins, 1997; Zhang et al ., 2017). These findings are consistent with the results of a long-term study in the USA conducted by Alhameid et al .…”

Aridity thresholds of soil microbial metabolic indices along a 3,200 km transect across arid and semi-arid regions in Northern China

“…After the pre-incubation, soil basal respiration was immediately measured directly in the soil columns placed in the PPR plastic container by a soil respiration system originally described by Cheng & Virginia (1993) and further modified by Zhang et al (2017).This system consists of a LICOR CO 2 analyzer (Li-6262; Li-COR Biosciences, Lincoln, NE, USA) a water bath for maintaining a stable temperature at 25 °C, a mass flow meter (GFM; Aalborg Ltd, Orangeburg, New York, USA) for determining air flow velocity, and an air pump connected with a soda-lime column which provided CO 2 -free air. The CO 2 -free air was passed through a copper coil submerged in the water bath for equilibrating the air temperature with the water bath temperature before reaching a manifold with 30 outflow tubes.…”