Effects on diversity measures
Overall, measures related to species diversity, i.e. richness, evenness and cover were all influenced by grassland type and showed no evidence of interactions. There was strong evidence of season having an effect on species richness. There was only weak evidence of prairie dog disturbance having an effect on cover, but on the other hand there was moderate evidence of prairie dog disturbance having interactive effects on functional diversity measures, specifically on FSpe and RaoQ (Table 2).
There was strong evidence of mountain grasslands having a positive effect on richness and cover, and these were higher than in all other grassland types (Fig. 2a & b). The wet season positively affected richness compared to the dry season (Fig 2d). There was weak evidence of prairie dog disturbance having a negative effect on cover (Fig. 2e). On the other hand, contrary to richness, there was strong evidence of evenness being higher in both agricultural and arid grasslands, compared to mountain grasslands which showed a negative effect (Fig. 2c).
There was no evidence that FEve was influenced by any of the variables nor their treatments or interactions, similar to FDiv which showed no evidence after pairwise post-hoc analysis (Appendix S3, Table S2). The FSpe model revealed strong evidence of grassland type moderating the effect of prairie dog disturbance on FSpe. This effect was particularly important for agricultural grasslands where sites with prairie dogs had a lower FSpe than sites without prairie dog disturbance (Fig 2f). RaoQ showed strong evidence of being influenced by the interaction of prairie dog disturbance and season. Grasslands without prairie dog disturbance (WOP) had higher RaoQ during the dry season compared to the wet season. There was no evidence of differences in RaoQ between seasons for grasslands disturbed by prairie dogs (WP). In the wet season, no evidence was shown regarding differences between conditions of prairie dog disturbance, in contrast to the dry season where RaoQ values varied greatly between conditions (Fig 2g).