The Spatial Factor, Rather than Elevated CO 2 , Controls the Soil Bacterial Community in a Temperate Forest Ecosystem

Abstract

ABSTRACT The global atmospheric carbon dioxide (CO 2 ) concentration is expected to increase continuously over the next century. However, little is known about the responses of soil bacterial communities to elevated CO 2 in terrestrial ecosystems. This study aimed to partition the relative influences of CO 2 , nitrogen (N), and the spatial factor (different sampling plots) on soil bacterial communities at the free-air CO 2 enrichment research site in Duke Forest, North Carolina, by two independent techniques: an entirely sequencing-based approach and denaturing gradient gel electrophoresis. Multivariate regression tree analysis demonstrated that the spatial factor could explain more than 70% of the variation in soil bacterial diversity and 20% of the variation in community structure, while CO 2 or N treatment explains less than 3% of the variation. For the effects of soil environmental heterogeneity, the diversity estimates were distinguished mainly by the total soil N and C/N ratio. Bacterial diversity estimates were positively correlated with total soil N and negatively correlated with C/N ratio. There was no correlation between the overall bacterial community structures and the soil properties investigated. This study contributes to the information about the effects of elevated CO 2 and soil fertility on soil bacterial communities and the environmental factors shaping the distribution patterns of bacterial community diversity and structure in temperate forest soils.