Details of the study sites.

MAP is the mean annual precipitation of the site in mm. N is the number of isolated trees sampled at each site. Each site is replicated by four blocks. The mean height of sampled trees [Height] and standard deviation [StDev] in meters is also listed, as is the identity, and number sampled (in parentheses), of the dominant tree species at each site. The data gathered here have also been included in a larger dataset comprising similar data from Africa and North America as part of a larger-scale analysis of competitive-facilitative interactions in savannas [31].