Water yield from harvesting and thinning southwestern mountain forests: Historical experience from US Forest Service research

摘要

Subsequent to the extreme fire seasons of 2000 and 2002, extensivethinning of Southwestern mountain forests has been designated as the preferredpractice to minimize the likelihood of widespread stand-replacing fires.Concurrently, historical hydrologic research been incorrectly popularized to indicatethat forest canopy removal can measurably augment water yields from forestedwatersheds. A popular misconception has therefore arisen that these two usuallyincompatible goals can be achieved simultaneously on the same land. Responsibleand appropriate silvicultural activities for other purposes, such as fire risk reduction,may increase water yield from upper elevation forests or improve water balancewithin lower elevation forests, depending on the intensity of canopy removal, treespecies, latitude, elevation, and aspect. These same activities may also restore otherdesirable landscape characteristics and should not be directed solely at water yield.Increases in water yield will be difficult to quantify, especially at the scale of largebasins, like the Salt River, that provide for large municipalities. Therefore, short termincreases in water yield from forest canopy removal should be considered aserendipitous benefit if and when it occurs in conjunction with other advantageousresults.