Figure 1.
Long term ecological research (LTER) sites and the annual precipitation for the year 2009.
Two replica plots were sampled in each of the arid, semi-arid and dry Mediterranean sites; in the shoreline site, five plots were sampled, representing three distinct soil types at close proximity. Additionally, at the semi-aris site, fingerprints of subsamples were also studied. Map and precipitation data from www.usgs.gov.
Figure 2.
NMDS ordination of TRFLP fingerprints.
Actinobacterial (top), α-proteobacterial (center) and bacterial (bottom) communities were sampled from dry Mediterranean (○), semi-arid (×), arid (▪), shoreline alluvial (□), shoreline stable sand (+) and shoreline shifting sand (•) sites. Restriction enzymes used are given in parentheses. Convex hulls connect samples from each site. NMDS axes do not possess biological meaning. Stress<12% for all ordinations, confirming a good correlation between the data and its ordination.
Figure 3.
Differences in community structure between samples separated by different geographic distances and seasons.
Bray-Curtis dissimilarity = 1 indicates that communities are very different, whereas Bray-Curtis dissimilarity = 0 indicates that communities are very similar. Each marker was studied using three restriction enzymes; only one is depicted here (and its name is given in parentheses), but for each marker, the overall pattern was very similar using the other two restriction enzymes (data not shown). Different letters indicate significant groupings. Bet., between.
Figure 4.
NMDS ordination of bacterial communities from arid, semi-arid and dry Mediterranean soils (stress = 13%).
Closer points imply more similar communities. Bacterial communities differ significantly between the three locations (MRPP test, P<0.05). Axes of the ordination have no biological meaning; however, percentages of organic matter (OM), clay and water saturation (sat.) in the soils correlated well with axis 1 (see R2 values in graph) and can each reliably replace it.
Table 1.
Main characteristics of the soils at the six sampling sites at winter and summer.
Figure 5.
Higher differences in environmental parameters cause higher differences in community structure.
Each point in the graph represents a comparison between two samples: the X axis depicts the difference between the two samples with respect to the following environmental parameters in soils: OM – organic matter; Clay – clay percentage; Saturation – water saturation; km – geographic distance between the samples in kilometers; the Y axis is the significance of the dissimilarity (MRPP tests' P-value) between bacterial communities from the two samples. Trend lines are R2>0.8 for all environmental parameters. Values under the ‘0.05 line’ signify two bacterial communities that are significantly different (P<0.05).