Area: 15.6 ha
Elevation: 503-716 m
Gage type: V-notch weir
Initial year: 1957
Objective: To assess the ecosystem response to deforestation.
Description: The major objective of the W2 experiment, which involved clear-felling with followup herbicide applications, was to eliminate transpiring vegetation to evaluate its influence on streamflow and nutrient cycling. All woody vegetation in W2 was cut between 18 November and 31 December 1965, during which time the ground was covered by at least 30 cm of snow. Stems and branches were lopped to a maximum height of 1 m above the ground and the cut trees were left in place. No roads or trails were constructed, and no vehicles were permitted in the area to minimize site disturbance. Herbicides were applied during the following three growing seasons to suppress regrowth and kill herbaceous vegetation. During the first growing season after the cut (1966), bromicil was sprayed by helicopter at a rate of 27 kg per hectare in a mixture of 120 g of 80% bromacil per liter of water (Pierce 1969). During the subsequent two growing seasons (1967 and 1968), the herbicide 2,4,5-T was mixed with water (1:25) and applied by personnel carrying backpack mist blowers. The amount of vegetative regrowth before spraying was about the same during the three summers herbicides were applied, and the applications were equal ly effective in eliminating most of the vegetative regrowth.
Treatment: Clear-felling and herbiciding,1965-1968
- Devegetated for three years, 1965-1967.
- In December 1965, all the trees and shrubs on Watershed 2 were felled and left in place.
- During the growing seasons of 1966, 1967 and 1968 the watershed herbicides were applied to prevent vegetation regrowth.
- Discharge of snowmelt was advanced by several days.
- Annual streamflow increased by 40, 28 and 26 percent during the 3 years of devegetation.
- Annual average weighted value of nitrate in streamwater increased from <1 mg/L in 1965-1966 to >50 mg/L two years later.
Continued research/treatment: Monitor changes in water yield and stream chemistry.
|•||Sediment yield in weir basin|