The samples from aCO2 and eCO2 were well separated by the first axis of RDA with 19.4% explained

by the first axis and a total of 47.6% explained with microbial communities (p = 0.047). Similar RDA results were obtained for subsets of functional genes, with 48.1% of the total variance explained for the C check details cycling genes (p = 0.037) and 48.2% of the total variance explained for the N cycling genes (p = 0.044). Within these variables, all detected functional genes and subsets of those genes were significantly different between CO2 treatments (p = 0.001). Figure 6 Biplot of redundancy analysis (RDA) of entire functional gene communities of soil samples from aCO 2 and eCO 2 conditions. Open circles represent samples PF-6463922 collected from aCO2, whereas solid circles represent samples

collected from eCO2. Four soil variables: soil N% at the depth of 0–10 ( SN0-10) and MK-4827 10–20 cm (SN10-20), soil C and N ratio at the depth of 10–20 cm (SCNR10-20) and soil pH (pH), and five plant variables: biomass of C4 plant species Andropogon gerardi (BAG) and Bouteloua gracilis (BBG), biomass of legume plant species Lupinus perennis (BLP), below ground plant C percentage (BPC), and the number of plant functional groups (PFG), were selected by forward selection based variance inflation factor (VIF) with 999 Monte Carlo permutations. To better understand the relationships between the functional structure of soil microbial communities and the plant and soil variables, variation partitioning analysis (VPA) was performed. After accounting for the effects of the CO2 treatment, the nine environmental variables could explain 42.2%, 42.8% and 42.8% of the total variation for all detected genes (p = 0.098), C cycling genes (p = 0.072), and N cycling genes (p = 0.087), respectively (Table 1). clonidine These five selected plant variables could significantly explain

24.7% (p = 0.010) of the variance for all detected genes, 24.6% (p = 0.022) for detected C cycling genes, and 25.1% (p = 0.014) for detected N cycling genes (Table 1). For the soil variables, these four selected variables also could explain 19.4% (p = 0.053) of the variance for all detected genes, 19.0% (p = 0.146) for detected C cycling genes, and 19.7% (p = 0.067) for detected N cycling genes (Table 1). Within these nine selected parameters, distinct differences were observed between the samples from aCO2 and eCO2 (p values ranged from 0.023 to 0.092), and the variance explained by four of the important variables, including pH (r = 0.411, p = 0.046), BLP (r = 0.378, p = 0.069), BPC (r = −0.345, p = 0.098), and PFG (r = 0.385, p = 0.063). Table 1 The relationships of microbial community functional structure to plant and soil characteristics by RDA and VPA a     All genes detected C cycling genes N cycling genes With nine selected variables First axis explanation (%) 19.