Changes of Soil Microbes Related with Carbon and Nitrogen Cycling after Long-Term CO2 Enrichment in a Typical Chinese Maize Field

Abstract

Elevated atmospheric CO 2 concentration (eCO 2 ) has been the most important driving factor and characteristic of climate change. To clarify the effects of eCO 2 on the soil microbes and on the concurrent status of soil carbon and nitrogen, an experiment was conducted in a typical summer maize field based on a 10-year mini FACE (Free Air Carbon Dioxide Enrichment) system in North China. Both rhizospheric and bulk soils were collected for measurement. The soil microbial carbon (MBC), nitrogen (MBN), and soil mineral N were measured at two stages. Characteristics of microbes were assayed for both rhizospheric soil and bulk soils at the key stage. We examined the plasmid copy numbers, diversities, and community structures of bacteria (in terms of 16s rRNA), fungi (in terms of ITS-internal transcribed spacer), ammonia oxidizing bacteria (AOB) and denitrifiers including nirK, nirS, and nosZ using the Miseq sequencing technique. Results showed that under eCO 2 conditions, both MBC and MBN in rhizospheric soil were increased significantly. The quantity of ITS was increased in the eCO 2 treatment compared with that in the ambient CO 2 (aCO 2 ) treatment, while the quantity of 16s rRNA in rhizospheric soil showed decrease in the rhizospheric soil in the eCO 2 treatment. ECO 2 changed the relative abundance of microbes in terms of compositional proportion of some orders or genera particularly in the rhizospheric soil-n particular, Chaetomium increased for ITS, Subgroups 4 and 6 increased for 16s rRNA, Nitrosospira decreased for AOB, and some genera showed increase for nirS, nirK, and nosZ. Nitrate N was the main inorganic nitrogen form at the tasseling stage and both quantities of AOB and denitrifiers, as well as the nosZ/(nirS+nirK) showed an increase under eCO 2 conditions particularly in the rhizospheric soil. The Nitrosospira decreased in abundance under eCO 2 conditions in the rhizospheric soil and some genera of denitrifiers also showed differences in abundance. ECO 2 did not change the diversities of microbes significantly. In general, results suggested that 10 years of eCO 2 did affect the active component of C and N pools (such as MBC and MBN) and both the quantities and relative abundance of microbes which are involved in carbon and nitrogen cycling, possibly due to the differences in both the quantities and component of substrate for relevant microbes in the rhizospheric soils.

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

“…A probable explanation for the high prevalence of fungi in our pots is that soil pH value of 4.2 in this study was most favorable for growth and survival of the fungus. Other study has been shown that pH has a decisive influence on fungal biomass [4,72]. Previous studies on the effects of eCO 2 on fungal community structure have documented a variety of responses, from no effect [66,73] to significant separations among communities [31,74,75].…”

“…Plant photosynthesis is a highly efficient and low-cost method of CO 2 absorption that might significantly affect soil ecosystems [2]. However, little research on the microbial community in the rhizosphere soils of greenhouse plants has been performed, even though greenhouses are widespread [3,4].…”

Impacts of Elevated Atmospheric CO2 and N Fertilization on N2O Emissions and Dynamics of Associated Soil Labile C Components and Mineral N in a Maize Field in the North China Plain

“…The error of measured data in eCO 2 during the summer maize growth period was controlled for within 20 ppm on more than 85% of days. The detailed description of this FACE experiment has been reported by Diao et al [47] and Han et al [48].…”

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

“…eCO 2 stimulates the C flow from plant roots to soils and promotes microbial activity. Greater utilization of additional C resources and root secretions [ 20 , 21 ], a significantly higher abundance of genes associated with C and N cycling [ 22 ] and increased enzyme activity [ 23 , 24 ] indicate rapid nutrient cycling and the stimulation of microbial activity under eCO 2 . Unfortunately, the isotope pulse-labeling technique used in previous studies was less stable than the steady isotope labeling technique, and little research has focused on the effects of various CO 2 concentrations, especially in greenhouse soil ecosystems.…”

“…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 ].…”