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    The density and development of greenleaf manzanita, other shrubs, and graminoids were evaluated in a young ponderosa pine plantation on a poor site in northern California from 1988 through 1997. Manual grubbing to a 5-foot radius created treatment regimes that lasted for 3 to 6 years and vegetation recovery times of 4 to 10 years. The duration and timing of the grubbing constitued the treatments. Greeenleaf manzanita was the dominant shrub in the former brushfied and again dominated after site preparation and release, in 1988 its density in the control aveaged 123,500 plants per acre, in 1997 density had declined to 44,450 plants per acre, but its foliar cover had increased to 34,600 ft² per acre and its height to 3.2 feet–values that were significantly larger than counterparts in any other treatment. Early release provided pine seedlings with a significant advantage in average height and diameter if continued each year for the first 3 years and first 6 years. However, manually grubbing the last 3 of the first 6 years gave no biological advantage and was more expensive. Delaying grubbing for the first 3 years and then grubbing each year for the next 3 years (years 4-6) also provided pine seedlings with a significant growth advantage over counterparts in the control, but was expensive. Delayed grubbing usually is biologically ineffective, but on poor sites such as this, any release is beneficial.

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    McDonald, Philip M.; Fiddler, Gary O. 2001. Timing and duration of release affect vegetation development in a young ponderosa pine plantation. Res. Paper PSW-RP-245. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; 15 p


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    competing vegetation, northern California, plant succession, ponderosa pine seedlings, poor site, timing of release

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