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Variance and Silviculture: Lessons and Directions

Variance and Silviculture: Lessons and Directions. Nick Som FS 533. Web of Science Search for silviculture related variance, (auto)covariance, spatial statistics 3 matches mean or average 133 matches Ratio: 0.023. Forest Science Search for silviculture related

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Variance and Silviculture: Lessons and Directions

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  1. Variance and Silviculture:Lessons and Directions Nick Som FS 533

  2. Web of Science Search for silviculture related variance, (auto)covariance, spatial statistics 3 matches mean or average 133 matches Ratio: 0.023 Forest Science Search for silviculture related variance, (auto)covariance, spatial statistics 91 matches mean or average 14,174 matches Ratio: 0.006 Where’s the focus?

  3. Scott et al 1998 • “The two highest densities averaged better percent survival than lower densities,” • “mean height increased as planting density increased,” • “…mean DBH also increased with closer planting density, “ • “…proportion of large trees was greater in the denser spacings, “ • “ trees in denser spaced plots averaged greater DBH and height than those in …” • EVIDENCE???!!!! • nope

  4. Figure 1: Average percentage of trees in relative DBH classes for the 300-, 1360-, and 2960-tph planting densities across all locations (Scott et al 1998).

  5. 1* SE Just put the confidence interval on there. 1.96*SE 2.xx*SE Is it that much harder? Figure 2c: Effects of opening size and edge orientation on windthrow of live subalpine fir at 5 m (dark circles) and 25 m (open triangles) from edge of openings. Error bars are 1SE, based on three replicate units for each point (Huggard et al 1999).

  6. Getting Better • Basics can still lack • More sophisticated use of variance • Hey, this stuff works • And it works better

  7. Bibliography • Huggard, D.J., W. Klenner, and A. Vyse. 1999. Windthrow following four harvest treatments in an Englemann spruce- subalpine fir forest in southern interior British Columbia, Canada. Canadian Journal of Forest Research 29: 1547-1556. • Scott, W., R. Meade, R. Leon, D. Hyink, and R. Miller. 1998. Planting density and tree-size relations in coast Douglas-fir. Canadian Journal of Forest Research 28: 74-78.

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