Chapter 9: Marking and assessing forest heterogeneityAuthor(s): M. North; J. Sherlock
Source: In: North, Malcolm, ed. 2012. Managing Sierra Nevada forests. Gen. Tech. Rep. PSW-GTR-237. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. pp. 95-105
Publication Series: General Technical Report (GTR)
Station: Pacific Southwest Research Station
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Marking guidelines commonly use stocking level, crown class, and species preferences to meet management objectives. Traditionally, these guidelines were applied across the extent of the stand. Current marking guidelines are more flexible, responding to within-stand variability with different stocking level, crown class, and species preference guidelines in response to fine-scale variability in forest structure and composition. By varying marking guidelines within stands, managers can meet potentially conflicting prescription objectives such as reducing crown bulk density while maintaining an average target canopy cover (Sherlock 2007). In this chapter, we discuss marking guidelines that may help explicitly implement a fine-scale response to within-stand variability and provide ways of measuring and assessing posttreatment heterogeneity. The emphasis in U.S. Forest Service General Technical Report PSW-GTR-220 "An Ecosystem Management Strategy for Sierran Mixed-Conifer Forests" (North et al. 2009) is still on using topography to help vary treatments, but silviculturists also need to respond to the stand conditions they have to work with.
In forests with frequent, low-intensity fire regimes, fine-scale heterogeneity makes it difficult to identify and demarcate stands ("group(s) of trees and associated vegetation having similar structures and growing under similar soil and climatic conditions" [Oliver and Larson 1996]). Structure analysis at the Teakettle Experimental Forest found that mixed conifer was made up of three dominant vegetation conditions: tree groups, gaps, and shrub patches. An average "stand" in Teakettle's mixed-conifer forest supports about 70 percent of the stand area in tree groups or scattered large trees, 16 percent in gaps, and 14 percent in shrub patches (North et al. 2002). Teakettle studies also found that ecological processes were best understood at this patch scale, before and after fuels reduction treatments were applied (Ma et al. 2010, North and Chen 2005, Wayman and North 2007, Zald et al. 2008). These patches differed in size but most were between 0.02 to 0.3 ac, fitting the general patch size pattern noted by Knapp et al. (chapter 12). For ecological restoration and the provision of habitat and microclimate variability, marking and measuring forest structure at finer patch scales may be an important complement to stand average assessments.
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CitationNorth, M.; Sherlock, J. 2012. Chapter 9: Marking and assessing forest heterogeneity. In: North, Malcolm, ed. 2012. Managing Sierra Nevada forests. Gen. Tech. Rep. PSW-GTR-237. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. pp. 95-105.
- Chapter 1: Fire and fuels reduction
- Chapter 12: The variable-density thinning study at Stanislaus-Tuolumne Experimental Forest
- Vegetation and Ecological Characteristics of Mixed-Conifer and Red Fir Forests at the Teakettle Experimental Forest
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