Partitioning abiotic effects and biotic associations on decadal wetland plant community turnover

Background/Question/Methods

Assessing patterns of community dynamics through time can be improved by not only determining species-specific responses to multiple, potentially interacting environmental change drivers, but also by identifying interactions between species. Understanding how species-environment responses and species-species interactions shape species turnover, community structure, and diversity is key to managing biodiverse ecosystems that host rare species and are already facing degradation pressures (e.g., altered hydrology, herbivory). Using long-term monitoring data from the Rocky Mountain Inventory & Monitoring Network, we asked: Q1) To what degree are patterns of species turnover driven by changes in environmental drivers vs. species interactions? Q2) Are species interactions across these ecosystems typically positive, negative, or neutral? Using a hierarchical modeling of species communities approach, we jointly estimated 1) environmental filtering - the influence of temperature, precipitation, climatic water deficit, depth to water, herbivory, and beaver activity, 2) biotic interactions, and 3) random processes in riparian, fen, and wet meadow ecosystems over approximately a 10 year time period.

Results/Conclusions

Species turnover was most strongly explained by changes in climatic water deficit, temperature, and precipitation. Other environmental variables such as ungulate and beaver activity only explained a small proportion of variance in species turnover. Surprisingly, depth to water, thought to be a strong environmental driver of wetland systems, only explained a small proportion of variance in species turnover. The distribution of species associations across wetland types were typically equally positive and negative. Together, these results highlight the primary importance of environmental filtering and secondary importance of biotic interactions on wetland plant community assembly, in line with existing literature. With quantitative species-specific predictions of species-environment and species-species responses, future management can monitor species of concern for conservation and restoration purposes that have relatively strong responses to these community assembly processes in the face of environmental change.