Temperate grasslands are one of the most threatened biomes globally, and with a 96% reduction of their historical extent, native grasslands in Minnesota are no exception. Increasingly degraded by invasive species, habitat loss, and fragmentation, these remnant grasslands now face the added threat of a rapidly changing climate and associated ecological stresses such as shifting species’ ranges and altered resource availability and timing. A critical challenge for effectively maintaining and restoring these ecosystems lies in our ability to understand and anticipate how changing climate and weather will affect prairie plant communities and how these effects will impact the efficacy of common management techniques, such as prescribed fire.
We leverage a unique 10-year dataset of 25 prairie sites spanning the latitudinal extent of Minnesota to examine how management actions interact with drought events and changing growing season lengths, both of which are known to influence community composition and are becoming more extreme. Using high resolution climate data and detailed relative cover and vegetation frequency data from 267 transects, we employ techniques from impact evaluations and econometrics to explore causal relationships between extreme weather, prescribed burning, and total invasive abundance, specifically we use fixed-effect panel regression models.
Results/Conclusions
We find a complex and influential effect of extreme weather on invasive species and, in some instances, significant interaction effects of burning and weather. In contrast to our expectations, changes to the growing season length did not have a significant effect on invasive abundance, including for warm and cool season grasses. This suggests that increasingly earlier springs may have little influence on prairie invasive dynamics. However, spring precipitation anomalies did significantly influence invasive abundance and alter the effectiveness of prescribed burning. Whereas burning generally decreased invasive cover and increased native species cover, its impact was sensitive to precipitation anomalies and varied greatly over time as well as between specific species, including invasive grass species which pose the greatest conservation threat.
While weather does influence prairie community composition and the effect of prescribed burning, overall, management-driven shifts in aggregate invasive abundance and dominance are more sensitive to the specific plant characteristics shared among species in each community, such as seasonality and phenological timing, as well as soil moisture preference. Thus, this trait-based sensitivity presents a challenge to managing invasive species as a collective unit. Ultimately, these results will be used to improve management recommendations for over 24,000 acres in MN.