Table 2.

Average plant–soil feedbacks for S. columbaria and S. minor, calculated using the equation 100(biomass of each conspecific − average biomass of heterospecific)/average biomass of heterospecific (van der Putten et al. 2007)

Conspecific	Heterospecific	Watering treatment	Total biomass	Belowground biomass	Aboveground biomass
S. columbaria plant in S. columbaria soil	S. columbaria plant in S. minor soil	Drought	56.90**	56.62**	57.21**
		Well-watered	− 52.81*	− 55.10*	− 50.33*
S. minor plant in S. minor soil	S. minor plant in S. columbaria soil	Drought	8.48	12.21	5.82
		Well-watered	25.49*	33.53	19.59

Droughted pots are compared to droughted pots, and well-watered to well-watered. Negative values indicate that the plant is smaller in conspecific soil than heterospecific, while positive values mean the plant is bigger. Significance stars refer to differences from zero using a two-tailed t test