Soil formation and maintenance of soil surface elevation are critical for tree island habitat stability in forested freshwater wetlands of the Everglades, where inorganic sediment input is scarce, and belowground dynamics control soil formation. Determining processes that lead to soil formation on tree islands is essential to understand tree island development, habitat stability, and nutrient cycling. Our objective is to measure belowground processes along a nutrient and hydrological gradient on tree islands in the Central Everglades.  Since edaphic and hydrologic conditions might constrain tree island forest structure and productivity through differential allocation of biomass above- and belowground, we hypothesize that there are differences in belowground biomass and production between tree islands that experience contrasting hydrological regimes.  To test this, we estimated standing crop root biomass and belowground productivity along a hydrologic-soil fertility gradient.  Belowground biomass values ranged from 28.5 g m^-2 to 187 g m^-2, with significantly higher biomass in the long hydroperiod and nutrient-poor environments than on the short hydroperiod and nutrient-rich environments (p=0.003).  Belowground productivity values ranged from 8.5±7.6 g m^-2yr^-1 to 1140±565 g m^-2 yr^-1, with relative higher values on short hydroperiod environments and lower on long hydroperiod environments; however, differences were not significant (p=0.335).  These results suggest that belowground processes are linked to the environmental conditions that characterize tree islands; however, the role of hydroperiod on belowground processes and its contribution to soil formation is still unclear.  The key to management and restoration of these tree islands relies on our degree of understanding of these processes.