ROOT BIOMASS AND SURFACE-AREA IN 3 SUCCESSIONAL TROPICAL FORESTS

Total root biomass and surface area of fine roots (< 5 mm diameter) were determined to a depth of 85 cm in 1-, 8- and 70-yr-old tropical forests on the same soil type (Typic Dystrandept) at Turrialba, Costa Rica. Root biomass and root area index (RAI) increased with age: biomass = 219, 1291, and 1555 g/m2, and RAI = 1.34, 4.66, and 5.28 in the 1-, 8- and 70-yr-old stands, respectively. Fine roots were most concentrated in the surface 5 cm of soil at all three sites, but especially so in the 70-yr-old stand. The 1- and 8-yr-old vegetations had proportionally more fine roots below 25 cm than the 70-yr-old vegetation, but lacked the large-diameter roots characteristic of the 70-yr-old stand.