Extended Data Fig. 3: Plant species that are near their northern range limit at our study site.

That is, these ten species are found in Minnesota, including at our study site, but not in Manitoba or Ontario, the Canadian Provinces that are more than 350 km north of study site. Gains of these species during our study could possibly be attributable to range shifts in response to climate change. However, 9 of these 10 species were already present at the beginning of these studies, observed in 1982, the first year of observations, or in 1983, the first year of observations in another survey of plants in these fields (E014), or in 1984 in another experiment (E002) that is also located in these same fields. Furthermore, an additional 166 plant species observed in our study are found in Minnesota and in Manitoba or Ontario and thus are not near their northern range limit. Thus, only 1 of the 176 plant species identified in our studies, Aristida tuberculosa, possibly arrived at the study site during recent decades due to a range shift in response to climate change. Even this species may have been present, but failed to be detected, during early years, due to dormancy or observation error.