Within these four groups, Group III had 68 nifH genes detected, and Groups I, IV, and II had 24, 22, and 5 genes detected, respectively. There were 28 nifH genes for the undefined group (Figure 5). In the major group (Group III), 21.3% and 25.7% relative abundances were detected from aCO2 and eCO2 samples, respectively. Similar

signal intensity distributions were observed in Group I, Group IV and the undefined Group with 7.2%, 8.3% and 7.0% relative abundances from the aCO2 samples and 11.8%, 9.3% and 8.9% from the eCO2 samples, respectively. check details Within five genes in Group II, the relative abundances from the two aCO2 genes and the three eCO2 were 0.2% and 0.3%, respectively. Among these five groups, significant increase in the total signal intensity under eCO2 was only observed in Group I, although higher total signal intensities at eCO2 were detected in all five groups (Figure 5). Figure 5 Maximum-likelihood phylogenetic tree of the deduced amino acid sequences of nifH sequences obtained from GeoChip 3.0, showing the phylogenetic relationship among the five nifH clusters. The depth and width of each wedge is proportional to the branch lengths and number of nifH

sequences, respectively. Some individual genes detected are shown in bold. The scale indicates the number of amino BIBF 1120 supplier acid substitutions per site and the tree is outgroup rooted with Q8VW94 (Nitrosomonas sp. ENI-11). Among the 60 nirS genes detected, 31 were shared by both aCO2 and eCO2 samples (Additional file 11), whereas 23 and six were unique to eCO2 and aCO2, respectively (Additional file 12). Details for nirS gene are described in the Additional file 5. The above results indicate that N cycling may

be significantly changed at eCO2, which was reflected in a significant increase in the abundance of detected nifH and nirS genes. Furthermore, the great nirS gene abundance would suggest the great N2O (a recognized greenhouse gas) emissions under eCO2 condition. Relationships between the microbial community structure and environmental factors The concentrations of atmospheric CO2 and nine environmental variables including four soil Dimethyl sulfoxide variables, soil N% at the depth of 0-10 cm (SN0-10) and 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 see more Bouteloua gracilis (BBG), biomass of legume plant species Lupinus perennis (BLP), belowground plant C percentage (BPC), and the number of plant functional groups (PFG) were selected by forward selection based on variance inflation factor (VIF) with 999 Monte Carlo permutations. The VIF of these ten parameters were all less than 6.5. Although the rates of biogeochemical processes about nitrification, ammonification and net N mineralization were also detected, these three parameters were rejected by forward selection since their VIF were all higher than 100.