Soil erosion and surface run off in secondary dipterocarp forest, annually burned and reforested grassland catchment [Philippines].
1987
Dumlao T.P.
The mean annual run off and run off coefficient were generally higher in the reforested grassland than in the annually burned grassland catchment because the former has higher drainage density. The secondary dipterocarp forest catchment had the lowest annual run off and run off coefficient due to its low drainage density and better vegetative cover. Surface run off was significantly correlated with rainfall amount and rainfall duration. High sediment concentration occurred at the first two months after the onset of the rainy season in the annually burned grassland catchment. Improvement of the vegetation cover by stopping annual burning and subsequent reforestation of the other grassland catchment markedly reduced sediment concentration. At the third year after the annual burning was stopped the sediment concentration of the reforested grassland was lower than that of the secondary dipterocarp forest catchment. The high surface run off of the reforested grassland catchment contributed to its high sediment yield inspite of low sediment concentration. Its mean annual sediment yield three years after reforestation was lower than that of the secondary dipterocarp forest catchment. The surface run off explained 60 to 97% in the variation of the sediment yield. Surface run off of the three catchments in August and November, 1984 had low nutrient content. The annually burned grassland had higher suspended sediment than the reforested grassland catchment.
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