Should remnant trees be left clumped or dispersed to favor species at risk?

Short answer

The available evidence leads to the following recommendations:

• Maximize number of retained trees using dispersed patterns. This will maximize the rate of rebuilding populations of dispersal-limited species that tolerate canopy opening (such as Lobaria oregana).
• Retain some aggregates of remnant trees (for example, in areas of the stand where operational logistics make a dispersed pattern impractical). This will provide more shelter for species sensitive to sudden opening of the canopy.
• In younger stands leave aggregates of remnant trees and shrubs at hotspots of epiphyte diversity. This can be done on the basis of stand features that foresters can easily recognize.
  

See long answer