Southern Research Station

Title: Determining productivity gains from herbaceous vegetation management with 'age-shift' calculations

Author: South, David B.; Miller, James H.; Kimberley, Mark O.; Vanderschaaf, Curtis L.

Date: 2006

Source: Forestry 79(1):43-56

Description: Gains in stand volume that result from competition control and fertilization are sometimes reported as 'percentage gains'. Because percentage gains arithmetically decline over time asstand volume increases, plantation managers have difficultyin using percentage gains to project growth and revenues. The 'age-shift' method quantifies the year advancementsin stand growth due to silvicultural treatments and, for herbaceousvegetation management, it has been proposed that this metricis less likely to change after the juvenile growth phase. Totest the sensitivity of the 'age-shift' method to time and hardwood competition, we used 20-year volume data from 11 loblolly pine (Pinus taeda L.) studies that had early complete herbaceous and woody competition control. Volume growth gains were expressed in terms of percentages and 'age-shifts'. On all sites with no woody competition, percentage gains declinedfrom age 8 years to age 20 years. In contrast, age-shift estimateson these plots either remained constant or increased over time. However, in four cases where woody basal areas were greaterthan 4 m² ha^–1 at age 15 years, age-shift gains due toherbaceous control decreased and eventually resulted in volumelosses. When evaluating the response to early herbaceous competitioncontrol, age-shift calculations have promise as a useful predictivetool on sites with low levels of hardwood competition. Fivemethods for calculating age-shift are presented.

Keywords: 

View and Print this Publication (174 KB)

Publication Notes: 

• We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
• This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

 Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility

Citation

South, David B.; Miller, James H.; Kimberley, Mark O.; Vanderschaaf, Curtis L.  2006.  Determining productivity gains from herbaceous vegetation management with 'age-shift' calculations.   Forestry 79(1):43-56