The Beauty of Green-Tree Retention
Harvests in Vista Views:
How Much do Cut Level, Pattern and Harvest-Unit Design Matter to People?

Robert G. Ribe

Department of Landscape Architecture &
Institute for a Sustainable Environment
University of Oregon
Eugene, Oregon  97403
rribe@darkwing.uoregon.edu

In designing timber harvests to reduce visual impacts, three major factors may be varied:

(1) amount of green-tree retention,

(2) pattern of retention (aggregated or dispersed),

(3) design of harvest form to look more "natural" (as per conventional visual resources management). 

In this study, images were photographed and simulated to exhibit all possible combinations of these three harvest attributes at five levels of  retention: 0, 15, 40, 75, and 100% of basal area.  Examples of four combinations of “pattern” and “design” at 15% basal area retention are illustrated here.  Only the two “square” harvest scenes are actual photos of DEMO treatment units;the other two scenes are simulated:

15% aggregated retention with no visual impact mitigation	15% aggregated retention with visual impact mitigation
15% dispersed retention with no visual impact mitigation	15% dispersed retention with visual impact mitigation

In a mail survey completed by 331 respondents, color scenes were rated for ugliness or scenic beauty on a scale of -5 to +5.  The results of this survey are summarized graphically, below.

 

Key findings:

• If green-tree retention is dispersed, higher levels of retention produce higher perceived scenic beauty.  (This is contrary to Northwest Forest Plan [NFP] guidelines which currently emphasize aggregated retention.)

• If retention is aggregated, increasing levels of retention produce only slight increases in perceived scenic beauty and little visual impact mitigation.  (Same note as for finding above.

• Harvest unit design as currently employed by the USS Scenery Management System (SMS) is only slightly effective and of little value in visual impact mitigation.  (The SMS needs to more aggressively incorporate green-tree retention as a visual management tool.)

•   Dispersed retention harvests require about 25% retention to avoid average perceptions of ugliness.  (This is higher than the 15% standard of the NFP.)

• Dispersed retention harvests require at least 40% retention to garner average perceptions of beauty.  (This amount should be the standard for harvests in landscapes requiring high and moderate levels of SMS scenic integrity.)

For more information on DEMO social perceptions research
http://gladstone.uoregon.edu/~enviro/criticalperceptions.html