Carbon Mineralization under Different Saline—Alkali Stress Conditions in Paddy Fields of Northeast China

Abstract

Soil organic carbon (SOC) mineralization (conversion of carbonaceous material to carbon dioxide) plays a central role in global carbon cycle. However, the effects of SOC mineralization under different saline–alkali stress conditions are poorly understood. In order to understand the carbon mineralization processes, four paddy fields with different saline and alkali degrees were chosen as the experimental samples and the soil CO2 emission fluxes at nine different time steps of the whole simulation experiment were observed. The physical and chemical properties of soils of four field conditions were compared for the dynamic changes of CO2 flux in the progress of paddy field cultivation simulations. The results showed that the first three fields (P1, P2, and P3) were weakly alkaline soils and the last one (P4) was strongly alkaline soil. The SOC content of each plot was significantly different and there was a near-surface enrichment, which was significantly negatively correlated with the degree of alkalization. The accumulation process of the SOC mineralization during the incubation time was consistent with the first-order kinetic model. In the initial stage of mineralization, the amount of CO2 released massively, and then the release intensity decreased rapidly. The mineralization rate decreased slowly with time and finally reached a minimum at the end of the incubation period. This study indicates that the SOC mineralization process is affected by a variety of factors. The main factors influencing SOC mineralization in the saline–alkaline soils are the exchangeable sodium percentage (ESP), followed by enzyme activities. Salinization of the soils inhibits the rate of soil carbon cycle, which has a greater impact on the carbon sequestration than on the carbon source process. The intensity and completeness of the SOC mineralization reactions increase with increasing SOC contents and decrease with increasing ESP levels.

The Development and Utilization of Saline–Alkali Land in Western Jilin Province Promoted the Sequestration of Organic Carbon Fractions in Soil Aggregates

“…PMC can be used to measure the content of soil organic matter that can be decomposed by microorganisms. It can represent the amount of carbon in the mineralized part of the soil in a certain sense, but it can also establish a certain relationship with soil fertility, environmental stress, cultivation time, and soil persistence [10]. It is of great significance to study the dynamic characteristics of SOC fractions in regulating soil nutrients, maintaining soil fertility, and improving the dynamic balance mechanism of soil carbon cycle.…”

Soil Restoration Practices Effects on Priming Effect Intensity and Carbon Fluxes

“…This further supports that the quality of added OM inducing the PE process is a major factor to take into account for SOC dynamics. In other words, this means that, depending of the land-use (such as degradation for farmland establishment) and agricultural practices (as input of highly degradable FOM), soils can become a signi cant source of CO 2 by the mineralization of large amount of stable C (Wang et al 2020). Yet it also means that with better understandings and practices, this agricultural soil has the potential to store at least -2.19 times more C (Minasny et al 2017), as its degraded counterpart and neighbor.…”

Rhizosphere Enzyme Activities and Microorganisms Drive the Transformation of Organic and Inorganic Carbon in Saline - Alkali Soil Region

“…The variation of SOC content depends on the input and output processes. The input mainly refers to the process of generating humus from plant litter under the action of microorganisms, and the output mainly refers to the mineralization process of SOM 28 . In addition, plants x atmospheric carbon into the soil through photosynthesis, which converts carbon dioxide from the air and releases it into the soil through well-developed plant roots.…”