Figure 16.3 Interactions among resources. The small balsam plant experienced little growth when light intensity was increased under low soil fertility. However, when light intensity and fertility were both increased, the large amount of growth that followed was much higher than the sum of the two separate effects. Error bars are 95 percent confidence intervals.

Data from W. J. H. Peace, and P. J. Grubb, Interaction of light and mineral nutrient supply in the growth of Impatiens parviflora, New Phytologist 90 (1982): 127–150.