Nature 449, 599–602 (2007)

In the Supplementary Information of this Letter, no biomass data were given for the two basal food-web compartments: roots and detritus. These were not measured in the soil samples (see also ref. 2). We used values for root biomass of 900 kg C ha-1 cm depth-1 in all webs with roots present. We used values for detritus biomass of 4, 25, 250 and 2,500 kg C ha-1 cm depth-1 for the successional stages 1 to 4, respectively, of both series (roughly corresponding to the increase in organic matter along the productivity gradients). Other than in the one replicate in stage 1 (Schiermonnikoog) where phytophageous nematodes were present (for which basal values of stage 2 were used), we assumed the same values for the replicates within each stage. The choice of these particular values does not affect our key findings. The data to do the stability analyses are provided in the Letter, its Supplementary Information or via refs 2 and 17. The estimated physiological parameter values, the matrix of feeding relations and prey preferences, formalization of detritus feedbacks and an example (Jacobian) community matrix are provided in the Supplementary Information to this Addendum.