Temperature and moisture responses to carbon mineralization in the biochar-amended saline soil

Abstract

• Cumulative C min increases with biochar added and incubation temperature.• The temperature rise reduced the turnover time of C pools and Q 10 . This study assessed the effects of temperature and moisture on carbon mineralization (C min ) in a saline soil system with biochar amendment. The dynamics of C min were monitored in a biochar-amended saline soil for 220 days by incubation experiments under different conditions of temperature (15°C, 25°C and 35°C) and moisture (30%, 70% and 105% of the water-holding capacity). Results showed that as the incubation temperature rose, cumulative C min consistently increased in soil added with 0-4% biochar. The two-compartment model could well describe the dynamics of C min . The temperature rise increased the concentration of labile C in soil, but reduced the turnover time of labile and recalcitrant C pools and the value of temperature coefficient Q 10 . The response of C min to moisture was varying in soil amended with different levels of biochar. In the control treatment (soil alone), cumulative C min increased only when soil moisture was N105%. In the biochar treatments, however, 70% of waterholding capacity was optimal for C min , except for 2%-biochar treatment at 35°C. The findings highlight the necessity to consider the combined effects of soil moisture, temperature and the amount of biochar added for assessing C min in biochar-amended saline soils.

Q10 values vary with different kinetic properties of C mineralization

“…Consistent with previous studies (Bracho et al, 2016;Dalias et al, 2001;Sun et al, 2016), we found that the temperature sensitivity of the C mineralization varied not only with the rate constants (k) but also with the labile C pool size (a 0 ) in this laboratory experiment (Fig. 1A-F).…”

“…As previously reported (Bárcenas-Moreno et al, 2009;Hamdi et al, 2013;Ranneklev and Bååth, 2001), the varying temperature regime (V T ) can promote the optimal growth of most mesophilic microbial groups. In addition, highly diversified microbial pathways increase the exploitation of C resources and the size of the labile C pool (Bracho et al, 2016;Sun et al, 2016). Thus, the greatest potential C mineralization (i.e., the highest a 0 ) under the V T was reasonable in the current study (Tables SI-2 and SI-3).…”

“…Q 10 evaluation is usually based on instantaneous CO 2 flux rates (Chang et al, 2012;Fang and Moncrieff, 2001;Karhu et al, 2014;Sun et al, 2016;Waldrop et al, 2010), time spans needed for an identical amount of C mineralization (Bracho et al, 2016;Wang et al, 2013;Zhu and Cheng, 2011), cumulative C flux over a given time period (Conant et al, 2008;Hamdi et al, 2013;Podrebarac et al, 2016), or microbial activity as a function of temperature (Diakova et al, 2016;Karhu et al, 2014).…”

“…For instance, the "equal-time" approach always leads to great discrepancies in the degradation of fast-vs. slow-turnover C pools among samples along with increasing incubation temperature and time, while the "equal-C" approach can underestimate the contribution of more recalcitrant substrates (Hamdi et al, 2013). Although a first-order model has been applied to disentangle the C mineralization process to quantify the sizes of various labile and recalcitrant pools as well as their decomposition rate constants, the temperature sensitivity of the abovementioned kinetic parameters of C mineralization has seldom been investigated (Braakhekke and de Bruijn, 2007;Bracho et al, 2016;Rey et al, 2008;Sun et al, 2016). Although Rey and Jarvis (2006) found that the labile C proportion (a 0 ) did not vary among 4, 10, 20 and 30°C, their experimental data were only derived from upper mineral soils, whose estimated labile fraction from the two-compartment model might be too small (1-9%) to detect substantial differences.…”

Integration into plant biology and soil science has provided insights into the total environment

“…The following is to summarize the main results and their implications for the 20 accepted articles in the special topic. Xu et al (2016aXu et al ( , 2016bXu et al ( , 2016c and Sun et al (2016aSun et al ( , 2016b P NMR technique to analyze P transformation under different pyrolysis temperatures and further compared effects of biochar and P fertilizers on P availability and plant biomass, providing good reference for utilizing biochar amendment into salt-soil. Long et al (2016aLong et al ( , 2016b) discussed about the current status of developing coastal mudflat areas in China by taking Yancheng, Jiangsu as an example and basing on their practical work for more than 20 years.…”