Journal of Geophysical Research: Earth Surface
© 2015 American Geophysical Union
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Online ISSN: 2169-9011
Associated Title(s): Journal of Geophysical Research
Reforesting degraded lands does not necessarily restore hydrological conditions
By the 1980s, forest lands in the Himalayas in central Nepal had become severely degraded as people cleared land for pastures. This led to lowered soil infiltration capacities, resulting in increased surface runoff, soil erosion, and flooding during the rainy season.
Between 1980 and 2000, forest managers attempted to restore previous hydrological conditions by reforesting considerable areas with fast-growing trees, mainly pines. Ghimire et al. studied how this reforestation effort and subsequent forest usage by the local population affected soil properties and hydrology by comparing degraded pasture, a footpath within the pasture, a 25-year-old pine reforestation, and a little-disturbed natural forest near Dhulikhel, central Nepal.
They found that reforestation did not restore soil hydrological functioning—runoff volumes were still at high levels. Heavily used planted forest areas were found to have soil hydraulic properties similar to degraded pasture and much lower soil hydraulic conductivity than undisturbed natural forest. The authors note that human activity, such as removal of litter from the forest floor, animal grazing, and harvesting of understory vegetation for fuel in the restored pine forest, appears to have contributed to the lack of restoration of hydrological functioning.