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The effects of forestation on soil hydraulic properties in the Middle Hills of Nepal: a preliminary assessment

Publication Type  Journal Article
Year  1987
Authors  Gilmour, D. A.; Bonell, M.; Cassells, D. S.
Journal  Mountain Research and Development
Volume  7
Pages  239-249
Abstract  

Measurements of infiltration and permeability were made at 4 depths on 5 sites near Chautara: an area deforested >100 yr earlier and heavily grazed and trampled; a 5-yr-old Pinus patula stand and a 12-yr-old P. roxburghii stand, both established on heavily grazed sites; a 12-yr-old P. roxburghii stand where a short shrubby cover was present and grazing was not heavy before planting; and in a religious forest (a near-natural stand). Results indicated that the surface 10 cm of the deforested site was noticeably compacted. Under the prevailing rainfall regime, however, only 17% of the monsoon season rain days included rainfall events with a 5-min intensity exceeding the surface infiltration rate. Plantations on grazed sites had higher surface infiltration rates than the grazed sites, but not as high as rates on ungrazed or lightly grazed land. It is concluded that it is likely to be several decades before changes in soil conditions after reforestation approach those of near-natural forest, but that the increases in surface infiltration rates are likely to have no significant effect on the incidence of downstream flooding. It is emphasized that these results may be relevant only to humid areas and not to semi-arid areas.