Reconstruction of forest site history in Ethiopian highlands based on C-13natural abundance of soils

Deforestation has been occurring in Ethiopia for millenia and has accelerat ed during the last century. On the other hand, historical accounts indicate that restricted afforestation of mountainous areas was initiated already 5 50 years ago. One of these areas was the Menagesha Forest. To reconstruct f orest site history, soil samples from the Menagesha Forest and Wendo-Genet areas were analyzed for C-13 natural abundance and C concentration. In soil s from Menagesha, delta(13)C values ranged from -17 parts per thousand to - 23 parts per thousand in the deeper horizons, and from -24 parts per thousa nd to -27 parts per thousand in the surface mineral soils and litter layer. This indicates that C-4 grasses were once an important component of this e cosystem, and supports the historical accounts. In the Wendo-Genet area, de lta(13)C values ranged from -16 parts per thousand to -14 parts per thousan d in the deeper horizons, and from -23 parts per thousand to -16 parts per thousand in the topsoil in both cultivated lands and forested sites, sugges ting more recent shifts from grassland to woodland or forest. With regard t o reforestation and soil conservation, it is encouraging that productive fo rest with high soil organic carbon concentration could be established on th e steep slopes at Menagesha. The study also shows that Ethiopian forest his tory is more complex than commonly appreciated, and that there has not been a simple unbroken trend of deforestation.