Effects of Elevated CO2 on Tomato (Lycopersicon esculentum Mill.) Growth and Rhizosphere Soil Microbial Community Structure and Functionality

Abstract

Although elevated CO2 (eCO2) in the atmosphere is one of the main factors influencing climate and ecosystem stability, less research on eCO2 in greenhouse soil systems has been conducted, despite their prevalence. In this article, phospholipid fatty acid (PLFA) profiling, 16S rRNA and Internally Transcribed Spacer (ITS) gene sequencing and high-throughput quantity polymerase chain reactions (HT-qPCRs) for 72 biogeochemical cycling-related genes were used to reveal the comprehensive responses of microbes to 23 days eCO2 fumigation in the soil of a tomato greenhouse. Our results indicated that eCO2 significantly increased microbial biomass (p < 0.05). The fungal community was more susceptible to eCO2 than the bacterial community; the fungal alpha diversity indices decreased significantly under eCO2 (p < 0.05) and the abundance of Ascomycota and its lower level taxa also increased significantly (p < 0.01). The absolute abundance of numerous C, N, P, S and methane cycling related genes increased significantly (p < 0.05) under eCO2. Furthermore, the microbial community structure and function were correlated with certain measured plant characteristics. Hence, the microbial ecosystem of the tomato greenhouse soil system was stimulated under eCO2. These results contribute to a greater understanding of how eCO2 in the atmosphere affects terrestrial ecosystem stability.

Fungi Dominated the Incorporation of 13C-CO2 into Microbial Biomass in Tomato Rhizosphere Soil under Different CO2 Concentrations

“…During the 15 days of CO 2 fumigation, the absolute abundance of the total PLFAs was significantly ( p < 0.05) stimulated by eCO 2 treatment, while the overall microbial community structure (the PLFA profile) was not influenced by CO 2 concentration ( Figure 3 ), as confirmed by Adonis analysis and Mantel tests ( p > 0.05). The above results were similar to those of previous studies in which short-term eCO 2 fumigation usually led to increases in root rhizodeposition and microbial biomass [ 42 ] but had little influence on microbial community structure [ 27 , 43 , 44 ]. In fact, because of the differences in plant species, soil characteristics and experimental designs, the observed response of the microbial community structure to eCO 2 is not always the same [ 27 ].…”

“…The above results were similar to those of previous studies in which short-term eCO 2 fumigation usually led to increases in root rhizodeposition and microbial biomass [ 42 ] but had little influence on microbial community structure [ 27 , 43 , 44 ]. In fact, because of the differences in plant species, soil characteristics and experimental designs, the observed response of the microbial community structure to eCO 2 is not always the same [ 27 ]. A study conducted in a grassland revealed that even a longer period of eCO 2 fumigation produced no effect on the microbial community structure [ 45 ], which might be attributed to the specific ecosystem involved and the large pool of soil carbon underground.…”

“…To reflect the changes in the biochemical properties of the soils, the soil pH, moisture, DOC, DON, NO 3 − -N and NH 4 + -N were measured. The measurement details are available in a previous study [ 27 ]. In brief, the total C and total N levels in the soils were measured by an elemental analyzer (Elementar Vario MACRO cube, Langenselbold, Germany) according to the operating instructions.…”

“…PLFA extraction and analyses were performed according to the modified Bligh and Dyer method [ 37 ], the details of which were provided in a previous study [ 27 ]. The concentration and 13 C labeling of fatty acid methyl esters (FAMEs) were analyzed by using a Trace GC 1310 system with a combustion column attached via a GC IsoLink II system to a Delta V Advantage isotope ratio mass spectrometer (all Thermo Scientific, Germany) [ 36 ].…”

“…Soils managed under plastic tunnel greenhouses, which are widely used in fruit and vegetable plantations and characterized by lower pH levels and nutrient-poor conditions under longer planting durations, have rarely been studied under various CO 2 treatments [ 22 , 25 , 26 ]. The soil microbial community composition in the rhizosphere soils of tomato changed insignificantly under various CO 2 treatments in our previous study [ 27 ]. However, the changes in active microbial community structures incorporating root-derived C were largely unknown.…”