Global minimum temperatures (T-MIN) are increasing faster than maximum temperatures, but the ecological consequences of this are Largely unexplored. Long-term data sets from the shortgrass steppe were used to identify correlations between T-MIN and several vegetation variables. This ecosystem is potentially sensitive to increases in T-MIN. Most notably, increased spring T-MIN was correlated with decreased net primary production by the dominant C-4 grass (Bouteloua gracilis) and with increased abundance and production by exotic and native C-3 forbs. Reductions in B. gracilis may make this system more vulnerable to invasion by exotic species and less tolerant of drought and grazing.