Alpha (α) diversity
Irrespective of the plot type, significantly (p <0.05) higher values of total observed OTUs and Chao1 estimator of bacterial communities were obtained in the high-altitude sites as compared to the low-altitude sites, though the pattern was inconsistent (Fig.3a, b and Appendix S3: Table S3). The Shannon index followed similar pattern, as observed above in case of observed OTUs in bacteria, reaching its peak at KU site followed by decline at KD site (Fig. 3c and Appendix S3: Table S3), however the Simpson index did not follow a monotonic trend along the altitudinal gradient but differed significantly between the plots and among the sites along the altitudinal gradient (Fig. 3d and Appendix S3: Table S3).
The observed OTUs and Chao1 estimator in fungal communities also followed a monotonic increase along the altitudinal gradient but dropped sharply at KD site – the highest altitudinal site (Fig. 3e, f and Appendix S3: Table S3). Overall, the alpha diversity of soil microbial communities increased from KZ to KU and differed significantly (p<0.05) between the invaded and uninvaded plots (Appendix S3: Table S3). The invaded plots at all sites showed higher diversity except KD, where opposite trend was observed. On the other hand, both Shannon and Simpson indices in fungal communities were significantly influenced by both the plot and site type (Fig. 3g, h and Appendix S3: Table S3). In particular, both indices were significantly higher in the invaded as compared to the uninvaded plots except KD site.