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<br />G007,)f <br /> <br />ate an estimated IOn,OO(J acres in thl~ Lowllr Hasin. <br />In the Upper Basin. these areas ma\' be even more <br />extensive, but the acreage is nut k~own. In forest <br />surveys, these areas iltC often included with as. <br />socia led noncommercial subalpine. aspen, and <br />mixed conifer fows!s. Climate is similar to the as- <br />sociated t~'pes, although wind is llsuall~' slronRer <br />in the large openings. Precipitalion averages 25 to <br />..W inches annually, and is mostly snow. Water <br />yield may range from 3 inches to as much as 15 <br />inches on the wetlt~sl sites. <br />The potential for increasing waler yield is be.. <br />Iie\'{'u to be less than in the alpine zone because of <br />less snow and wind. It has been estimated thai <br />streamflow from mountain grasslands in eastern <br />Arizona could he incn'aseu bl' 1.5 tn 2 inches if <br />snllw could be held in large drifts where it falls <br />instead of bt'ing blown lung distances across these <br />areas (Thompson tlf al. 1~1761. Again. an important <br />consideration is th(~ visual impact of SilO\\' fenccs. <br /> <br />RU(:ky .\fountain Suhalpine F()n~ls <br /> <br />Conifer fomsts. including spruce.fir. lodgepnlp <br />pinn. Douglas-fir. mixed conifers, and pOndtlrOsa <br />pine. cover nearly 15 million acres within the <br />Colorado River Basin, of which nearly 13 million <br /> <br />acres are c1assifil'd as commercial. Subalpine <br />forests (fig. 91. composed of spruce-fir. lodgepole <br />pine. and. for purposes of this report. Uouglas-fir. <br />occupy some 6.8 million acres in the Upper Basin: <br />5.5 million acres of these are considered corn. <br />mercial. The elevation of Ihese forests varies from <br />7.000 10 11.500 fflel. just below the alpin!:: zone. <br />The climate is cool and moist; mean temperature is <br />near freezing. Precipitation is about two-thirds <br />snow and a\'erages from 20 to as much as 55 inches <br />pt!r year. Water yield may vary from Stoas much as <br />40 inches per year.I<Jfgcly from snU\\'llIclt. Overall. <br />the a\'cragt! precipitation is estimated at 28-30 <br />inches and streilmllow (water yield} al 12-15 in. <br />ches (Leaf IY751. <br />The puh'lltial is good for increasing walt'r yield <br />in th~ subalpine type by managing for snow re. <br />distribution and transpiralion reduction in small <br />forest openings (Leaf 1975). Increases in WOller <br />~'ield of from 1 to 3 inches (fig. 10) can be expected. <br />depending on site factors and managemenl <br />strate~ies. Simulation harvest of lodf,wpole pine <br />{filo\. lOJ was by a series of patch cuts, 5 to R tree <br />heights in diameter, each CO\'llring about {me-third <br />of the planning unit. The cuts would be made at <br />30-year intervals spread o\'er a planning puriml of <br />120 years with periodic thinninf.\ ill the re- <br />generated stands. The matllJgement straltl~Y for the <br /> <br /> <br />Figure g.-Subalpine foreSls cower epprodmately 6.8 million acres in the Upper COlorado <br />Rinr Basin. The spruc.lir type, shown In this waterShed wiew In the ColoradO Rockies, <br />makes up about 50% 01 the tolal subalpine area. <br /> <br />9 <br />