Figure 1.
Normalized denitrification rates at different temperatures and salt concentrations.
The rates are normalized by percent of the maximum rate within each soil community replicate and modeled using a Gaussian function and a power equation for temperature (a) and salt concentration (b) gradients, respectively. The fitted curves and data points are colored by community and soil treatment: Red, community A, fallow; Green, community B, unfertilized; Blue, community C, nitrate fertilized; and Black, community J, cattle manure fertilized. Each field replicate within a treatment/community is represented by different symbols.
Table 1.
Model parameters representing the functional operating range for potential denitrification rates in assembled soil communities under temperature and salt concentration gradients modeled using a Gaussian function and power equation, respectively.
Figure 2.
Venn diagram representing shared and unique restriction fragment length polymorphisms (RFLP) groups for denitrifying communities.
The groups were detected by screening ∼100 nosZ gene clones retrived from soil communities A–C and J. Community A had 30, B had 34, C had 23 and J had 44 of the 64 groups in total.
Table 2.
Diversity indices of denitrifying bacterial communities determined from RFLP group membership using Chao and Shannon (H') metrics or by comparative sequence analysis for phylogenetic diversity (PD), net relatedness index (NRI), and nearest taxon index (NTI) based on nosZ gene clones from each soil community (n = 3).
Figure 3.
Non-metric multidimensional scaling of phylogeny-based composition of denitrifying communities.
The distance matrix was based on pairwise differences in the unique fraction of branches shared (UniFrac) for each soil community replicate in the maximum likelihood phylogentic tree of 400 nosZ gene sequences. Vectors indicate diversity metrics and modeled rate parameters that were significantly correlated with the ordination (P<0.1): Chao richness index, Shannon’s diversity index (H´), phylogenetic diversity (PD), width of the modeled temperature gradient curve (w), denitrifiction rate at temperature optimum (Tm), salt concentration when denitrification rate was zero (SA0) and salt concentration at the initiation of rate inhibition (SAI). Stress was 12.0.