The relative importance of changing temperatures versus precipitation for flowering phenologies in a northern tallgrass prairie

Background/Question/Methods

A growing body of evidence indicates that plant species across the globe are shifting flowering phenology in response to climate change.  In temperate latitudes, plants are flowering earlier in particular for early growing season species.  However, less is understood about the influence of changes in other climatic factors on phenological patterns. In particular, precipitation patterns are expected to change with increasing global temperatures but it is less clear how species may be responding to these changes in regards to reproduction. By analyzing a long-term dataset (1910-2012) of first flowering patterns in a tallgrass community near Fargo North Dakota we examined sensitivities of plant flowering time to temperature and precipitation changes.  Our goals were to 1) determine if plants are shifting earlier or later in their flowering patterns with increasing temperatures and changes in precipitation; 2) compare sensitivities to temperature versus precipitation; and 3) examine characteristics of negative and positive responders.

Results/Conclusions

We found that native and exotic species growing in the tallgrass community have a high prevalence of negative responders to higher temperatures but that positive responders tend to be late season species. Moreover, given the high inter-annual variance in temperature and precipitation there is a corresponding high variance in the strength of the relationship between first flowering date and sensitivity to temperature. Fourteen percent of the species monitored responded significantly to shifts in annual precipitation and over half of those flowered earlier in association with wetter years.  Exotic species tended to advance flowering and native species delayed flowering with higher precipitation levels.  These results suggest that flowering patterns and potentially reproductive success of tallgrass species are tracking multiple changes in climate and that grassland communities that are heavily influenced by precipitation levels may respond differently to climate change in comparison to other communities.