3.5 Bacterial general co-occurrence network in different land
uses
We constructed four co-occurrence networks based on OTU-OTU correlations
for different land uses and seasons, and found striking differences in
the network size between land uses (Figure 8). There were three main
clusters in maize field for both seasons, while only one main cluster in
woodland. The networks of maize field in the spring and autumn (376 and
371 nodes) were more complex than that of woodland (278 and 334 nodes).
Positive correlation (co-occurrences) displayed as edges was
significantly higher than negative ones (mutual exclusions) in all the
networks (Table 2). As shown in Table 2, network topological parameters
varied in two land uses. The woodland network exhibited considerably
higher average degrees, higher clustering coefficient and higher network
density compared with the maize field network. The highest positive and
negative correlation were recorded in maize field in the spring and
woodland in the autumn, respectively, while the lowest positive and
negative correlation were both recorded in the maize field in the
autumn.
More
than 70% of all nodes were assigned to five dominant phyla includingProteobacteria , Acidobacteria, Actinobacteria andChloroflexi . Interestingly, Bacteroidetes was found as the
dominant group in the maize field co-occurrence network, while not shown
in woodland network (Figure 8).