Comparing Stand Age 140 Basal Area per Acre Outputs from the DFC, FVS and ORGANON Models

1. Comparing Stand Age 140 Basal Area per Acre Outputs from the DFC, FVS and ORGANON Models • Steve McConnell • Forest Integrity • Spokane, WA • Growth Model Users Group Meeting • December 9, 2011 • Portland, OR

2. The DFC Model • Used for managing riparian forests in Washington State. • Predicts basal area growth based on site class, tree species and stand inventory data • Provides harvest prescriptions based on management option, site class, stream size and projected stand age-140 basal area

3. The DFC Model • Derived from ORGANON • In use for management purposes since 2001 • Never compared against other commonly used models

4. Riparian Management Zones • Management Focused on Inner Zone

5. Provides Two Management Options 1.Thin from below 2. Leave Trees Closest to Stream How does thinning response compare to other commonly used models?

6. Used Data from the Desktop Analysis Study • 150 FPAs from 2003 and 2004, 75 from each year • Some would not meet now-current DFC Target (325) but allow for comparing model outcomes • Compared old vs. new DFC Model outcomes and determined they were reasonably similar – used old Model

7. Important Characteristics of DFC Model • Works off total stand age • Uses 50-yr site index • Has different variants for WH or DF • Simulates as if stands were all WH or DF • Has a background “kill function” for hardwood to simulate senescence

8. Site Index Values • Douglas-fir: 145, 125, 105, 85, 65 for Site Class 1-5, respectively • Western hemlock: 20’ less for each Site Class, 1-4

9. Hardwood Senescence • Stand age 55, reduce hardwood 20% • Stand age 65, reduce hardwood 25% • Stand age 75, reduce hardwood 33% • Stand age 85, reduce hardwood 50% • Stand age 95, reduce hardwood 100%

13. Thinning from Below • Less preferred option where Option 2, leave trees closest the stream option is available • Only option available on Site Class 4, 5 and Site Class 3 Large Stream

14. Thinning from Below • Questions raised post-thinning growth response • Easier to do using ORGANON – get rid of hardwood at outset so don’t need to replicate senescence scenario • Time between implementing cut and stage 140 is usually about 80 years

15. For Comparison Against FVS and ORGANON • Converted DFC data to a per acre basis – “expansion factor” • Set Site Index and age to match those used in the DFC Model • Used quantitative data from DFC Model as prescription to compare against using FVS and ORGANON

16. Forest Vegetation Simulator • Used PN Variant – 50-yr site index • For coastal stands used Quinault Location • For inland stands used Olympic Location • Hard-wired Site Index and left Habitat Type blank • Found and used elevation but left slope and aspect at default values

17. Forest Vegetation Simulator (Continued) • Created addfiles to set stand age to a divisor of ten in first cycle and used ten-year cycles thereafter to age 140 • Created an addfile to replicate hardwood senescence in DFC Model • Created addfiles for each stand to simulate 100% hardwood removal and thin from below

18. ORGANON • Used Management function to 1st remove all hardwood and then thin conifers from below matching the DFC Model harvest • Grew stand to 138 to 142 yrs old – five-year cycles, no way to adjust