## 3 Results
### Co-Occurrence Network Analysis of Fungal and Bacterial Taxa in Rice Field Soils  
The distributions of dominant fungal (19 total) and bacterial (34 total) OTUs were used to construct fungal and bacterial co-occurrence networks [Figure 5a], With bacterial and fungal networks analyzed separately in [Figure 5b,c]. The characteristic path length (CPL) of the fungal-bacterial co-occurrence network was 1.59 cm (Figure 5), with a diameter of 5.00 cm, and a clustering coefficient (CC) of 0.35. The bacterial-only co-occurrence network also contained 53 nodes that were significantly correlated, comprising a total of 502 edges representing 293 and 209 positive and negative correlations, respectively. Thus, putative mutualistic or cooperative relationships between bacterial and fungal taxa (58.36%) were more apparent than putative competitive associations (41.64%). The OTUs with the highest connectivity in the fungal and bacterial networks were identified as top network taxa. The top taxa in KA soil networks included OTU69 (_Emericellopsis_) (connectivity of 31) in addition to OTUs 1599 (Acidobacteria Gp6) and 1133 (Acidobacteria Gp6) (both with a connectivity of 24), which were mutually exclusive. The top fungal and bacterial taxa in NKA were OTU139 (Sordarias) and OTU9 (_Nitrospira_) (connectivity of 26), respectively, which exhibited a positive correlation with one another. The CPL of the bacterial correlation network was 1.38 cm [Figure 5b], while the diameter was 3.00 cm, and the clustering coefficient (CC) was 0.41. The network consisted of 34 nodes and 329 edges representing 229 positive and 100 negative correlations. The CPL of the network in module 1 was 1.254 cm, and the diameter was 3.00 cm, while the CC was 0.43, and the module comprised 29 nodes and 296 edges (196 positive and 100 negative correlations). The top bacterial OTUs, OTU1599 (Acidobacteria Gp6) and OTU9 (Nitrospira), were present in module 1. The top bacteria of KA was OTU1599 (Acidobacteria Gp6), which exhibited positive correlations with OTU1603 (Burkholderiales), OTU3528 (_Phycioccus_), and OTU835 (\(\beta\)-proteobacteria). The top bacteria in NKA included OTU9 (_Nitrospira_), which exhibited mutually exclusive relationships with OTU835 (\(\beta\)-proteobacteria), OTU3528 (_Phycioccus_), and OTU1603 (Burkholderiales). The internal fungal correlation network CPL was 1.39 cm, its diameter was 3.00 cm, and its CC was 0.28 [Figure 5c]. The network consisted of 19 nodes and 38 edges representing 30 positive and 8 negative correlations. The network CPL for module 1 was 1.23 cm, its diameter was 2.00 cm, and its CC was 0.41. The network consisted of 9 nodes and 27 edges, with 22 positive and 5 negative correlations. The network CPL for module 2 was 1.17 cm, while its diameter was 2.00 cm, and its CC was 0.42. The network consisted of four nodes and four positively correlated edges. The top fungal taxa, OTU69 (_Emericellopsis_) and OTU139 (Sordarias), in KA were present in module 1. Both the OTUs exhibited positive correlations with OTU3379 (Gaeumannomyces), OTU81 (Sordariaceae), and OTU63 (_Fusarium_). Figure 5: (**a**): Co-occurrence network analysis of dominant fungal and bacterial taxa; (**b**): Co-occurrence network and modules comprising dominant bacterial OTUs among KA and NKA soils; (**c**): Co-occurrence network and modules of dominant fungal OTUs among KA and NKA soils. Note: KA, karst areas; NKA, non-karst areas. Different colored nodes in [Figure 5a] represent different clades of bacteria and fungi, with the value on the node indicating the OTU number for the particular taxa, and node size representing the abundance of the taxa. Different colored nodes in [Figure 5b] represent the different phylum classifications for bacterial OTUs; and the value on the node represents the number of each bacterial OTU, while the size of the node indicates abundance.