Soil fertility and plant productivity are known to vary across the Amazon Basin partially as a function of geomorphology and age of soils. Using data on herpetofaunal abundance collected from 5 × 5 m and 6 × 6 m plots in mature tropical forests, we tested whether variation in community biomass of litter frogs and lizards across ten Neotropical sites could be explained by cation exchange capacity, primary productivity or stem turnover rate. About half of the variation in frog biomass (48%) could be attributed to stem turnover rate, while over two-thirds of the variation in lizard biomass (69%) was explained by primary productivity. Biomass variation in frogs resulted from variation in abundance and size, and abundance was related to cation exchange capacity (45% of variation explained), but size was not. Lizard biomass across sites varied mostly with individual lizard size, but not with abundance, and size was highly dependent on primary productivity (85% of variation explained). Soil fertility and plant productivity apparently affect secondary consumers like frogs and lizards through food webs, as biomass is transferred from plants to herbivorous arthropods to secondary consumers.