Changes in soil structure and hydraulic properties in regenerating rain forest

The structure of soils in areas of rain forest cleared for pasture is often compacted due to trampling by animals. Then pasture is abandoned, regenera tion of forest cover may be achieved from natural seed sources nearby. Howe ver, the regeneration of soil structure is also important for local hydrolo gy and successful establishment of some plant species. In this study we inv estigated changes in soil structure and hydraulic properties in a series of plots on volcanic soils in the San Luis Valley, Costa Rica. The plots were current pasture, 15- and 20-year-old regenerating forest, and primary rain forest. Infiltration rate increased with increasing forest age and the water releas e characteristic reverted gradually from one with greater water retention a t all matric potentials in the pasture plot towards that found in the prima ry forest. Compaction and low porosity were features of both the current pa sture and 15-year-old regenerating forest in comparison to the primary fore st.