FOREST REGENERATION IN ABANDONED LOGGING ROADS IN LOWLAND COSTA-RICA

We characterized plant regeneration in four old logging roads (700-100 0 m long), 12-17 yr after abandonment, in selectively logged forests i n lowland Costa Rica. Sets of 4-m(2) plots were laid out at 20-m inter vals in three distinct microhabitats: road crack (topsoil eliminated), road edge (where removed topsoil accumulates on the sides after road construction), and adjacent logged forest. Density of stems greater th an or equal to 1 m tall and less than or equal to 5 cm DBH (included c anopy tree, midstory tree, liana, palm, shrub, and tree fern species) was highest in the road edge plots than either the track or logged for est plots. This ''edge effect'' is presumably due to buried seed germi nation of light-demanding trees and shrubs after moderate soil disturb ance, less compaction, and higher substrate fertility than in road tra cks. Species richness was the lowest, but relative dominance the highe st, in the crack plots of all roads: 6-9 species comprised alone 50 pe rcent of the Importance Value Index (IVI), in contrast to 11-15 and 16 -22 species required to reach 50 percent IVI in edge and forest plots, respectively. We found evidence of soil compaction in tracks of three out of four roads which, in addition to low substrate fertility, and initial lack of on-sire plant propagules, could explain slower recover y of stem density and species richness compared to edge and logged for est plots. For stems >5 cm and less than or equal to 20 cm DBH, densit y and basal area in the track plots averaged about one-fourth of edge and logged forest plot values. We estimated recovery of basal area in road tracks to take at least 80 yr to reach the status Found in logged forest, and species richness over an even longer period. We suggest t hat abandoned logging roads serve as long corridors of relatively unif orm and long-lasting floristic and structural characteristics that may confer particular ecological roles in selectively logged forests.