Anticipated atmospheric CO2 elevation differentially influenced the soil microbial diversities in crop, grassland, and forest: A meta-analysis

Abstract

The increasing of atmospheric carbon dioxide (CO2) has a greater impact on soil microbial diversity and related soil nutrient dynamics under different ecology. In our study, a global database of 572 observations from 202 research publications analysed to explore the impacts of increased atmospheric CO2 on soil microbial diversities. The soil microbial biomass carbon (MBC), structural (microbial populations), and functional (enzymatic activities) microbial diversities were analysed across 22 nations and 108 crops (including forest, grassland and C3 plants). The impact of three elevated CO2 (eCO2) concentrations i.e., <25%, 25–50% and >50% over ambient in three-time scale (1970–1989, 1990–2009 and 2010–2020) and two region (tropical and temperate) on the above parameters were studied. Higher MBC contents were found under eCO2 level (>50%) followed by eCO2 level 25–50% and <25% over ambient in C3 plants and forest ecology, however, in grassland the average MBC content was higher under eCO2 level 25–50%. Soil enzymatic activities were higher under eCO2 (25–50%) than other elevated CO2 conditions in the forest and C3 plants, whereas in grasslands, the enzymatic activities decreased with an increase in CO2 concentrations. These findings suggested that grassland was more sensitive to elevated CO2 as such compared to the forest and C3 plants. Both the bacterial and fungal populations were higher only up to eCO2 level (25–50% over ambient) in all the vegetations. So, higher microbial populations and soil enzymatic activities were noticed up to 50% elevation of CO2 over ambient conditions irrespective of the vegetation and region indicating higher belowground soil activities. Therefore, the findings suggested that there would be higher belowground soil activities in increased CO2 levels (anticipated climate change scenario) in agriculture and forest crop up to a certain threshold elevation of CO2 which needs better water and nutrient management for getting sustainable yield. The finding also suggested region and vegetation-specific (crop/forest/grassland) management options are necessary for fetching advantage of CO2 fertilization and to tackle the abiotic stress management of crops.