An assessment for the Clallam County noxious weed control program of $3.60 per parcel and $0.31 per acre on all property not classified as forest land shall be imposed annually. Under RCW 17.10.240, forest lands may be subject to an annual noxious weed assessment that does not exceed one-tenth of the weighted average of the per acre and per parcel rate levied on other lands that are subject to the weed assessment. Property classified as forest land, as defined in RCW 84.33.035, which is used solely for the planting, growing or harvesting of trees and which is typified, except for a single five-year period following clear-cut logging, by canopies so dense as to prohibit the growth of an understory, shall be assessed at the rate of $0.36 per parcel and $0.031 per acre.