Natural Disturbance Units of the Prince George Forest Region

1. Natural Disturbance Units of the Prince George Forest Region The Mackenzie Story

2. Natural Range of Variability Concept • biota of a forest are adapted to the range of conditions created by natural disturbances and thus should be less impacted by forest management if the resulting patterns resemble those of natural disturbances

3. Natural range in variability concept

4. Why? • part of our commitment to mange for biological diversity • incorporated into CSA, SFI, SFM certification • often makes both ecological and economic sense (i.e., why are we still using the 60 ha rule) • being accepted internationally as the best way to manage forests for ecological sustainability

5. Disturbance Pattern Studies 1) Fire and Harvesting Comparison1 • conducted on broad plateau with homogeneous climate • compared rate of disturbance, patch size, shape, and residual elements within the disturbance 2) Climate and topography effects on fire return and patch size2 1DeLong and Tanner 1996 2DeLong 1998

6. Findings of Disturbance Pattern Studies • harvesting replacing wildfire • 0.1-1.2% of the landscape disturbed per year by wildfire prior to fire control • more area in larger and smaller patches for wildfire vs harvest • mid sized patches (50-100 ha) rare in the natural landscape

7. Findings of Disturbance Pattern Studies • wildfire pattern results in more interior forest conditions • wildfires more irregularly shaped • wildfires leave patches of mature timber behind

8. Natural Patch Size DistributionEcological Advantages • make for easier access control • results in lower active road densities • effective management strategy for woodland caribou

9. Natural Patch Size DistributionEconomic Advantages Reduce Costs of: • road building and maintenance • transportation of equipment and wood • development plans and prescriptions

10. 1995 Harvest area 610 ha Roads 28.4 km 1999 Harvest area 989 ha Roads 15.1km

11. Wet Montane Forest Stand Structure Study • Study Description • located in very wet sub-boreal spruce forests in northern Rocky Mountains • examined stands of different time since stand replacement wildfire

12. Wet Montane Forest Stand Structure Study • Findings • stands never close crown and lack typical stem exclusion stage of succession • stands multi-layered and with inverse j distribution of stems at young age (e.g., < 60 yrs)

13. Stand Structure Comparison Wet Montane Sub-boreal Moist Plateau Sub-boreal

14. Stand Development Comparison

15. Wet Montane Forest Stand Structure Study • Ecological Implications • crown closure and effect on understory vegetation • wildlife movement • grizzly bear?

16. Wet Montane Forest Stand Structure Study • Economic Implications • reduced planting costs • reduced site preparation costs (e.g., less mounds) • likely reduced vegetation management costs • unknown impacts on yield

17. Why change from the existing guidelines? • better information (scientifically based) • NDT’s were very coarse (do not reflect difference in succession, stand structure, etc.) • new units are easier to work with operationally and guidance is more flexible

20. Recommended practices based on understanding of natural disturbance dynamics • old growth management • patch size distribution • proportion of silviculture systems that approximate stand replacement vs gap replacement disturbance • management of species composition and stand structure

21. Strategies for Old Growth Management Rotating reserves • Boreal Plains, Moist Interior Fixed reserves in each watershed • Wet Mountain, Wet Trench Fixed reserves over multiple watersheds • all the rest

23. Patch Size Distribution for Clearcut Style Harvesting • emulating natural disturbance patch size would result in patches > 1,000 ha dominating most landscapes • uncertainty with respect to social acceptance

24. Stand Replacement vs Gap Replacement Pros • in current version of FSC • gap replacement style harvesting supported by environmental groups • more harvest potential in some units Cons • estimate based on expert opinion • lead to more partial cutting in some areas: problem with roads, more expensive

25. Succession and Stand Structure Development • very important component of guidance • a lot baseline data available • need to determine implications to stand yield • models need to be developed to accurately reflect growth of mixed stands, patchy stands, impact of insects and disease

26. Example 1 - Moist Interior Location, Climate, and Vegetation • mean annual precip. 481-727 mm • MAT 0.6 - 3.7oC • climax forests Sw and Sb but many forests At or Pl seral at low elev. due to disturbance history • stands of Ab and/or Sw along large rivers • stands of Fd in warmer portions on drier ridges

27. Moist Interior Natural Disturbance Ecology • fire and MPB are key stand-replacement disturbance agent • estimated fire cycle of 100 for low elevation and 200 for high elevation • estimated 20 - 29% of forest >140-yrs-old but stands generally don’t exceed 200 yrs at low elevation • estimated 44 - 57% >140-yrs-old at high elev.

28. Moist Interior Natural Disturbance Ecology - Uplands (cont.) • dense Pl or At stands often initiate after fire, self thin over 60 years • older stands more Sx, Bl, and Sb • remnant fire skips play an important role for maintaining biodiversity • little dispersed remnant structure over longer term (e.g., individual live trees that survived the fire)

29. Moist Interior Natural Disturbance Ecology - Upland (cont.) • 70% of stand replacement disturbance patches > 100ha at low elevation; 70%> 100 ha at high elev. • Generally > 100 snags/ha > 15cm dbh in older stands; average of 12 snags/ha in young stands • CWD variability very high, volumes generally >100 m3/ha in older conifer stands

30. Moist Interior Forest Management Effects • fire control has resulted in more old forest in remote areas or protected areas where harvesting not occurring • less young natural forest; some organisms fire obligates • alteration of patch size distribution in some areas

31. Moist Interior Recommended Practices • rotating reserves; some fixed reserves in ESSF • some proportion of landscape in young unsalvaged natural forest • patch size closer to natural • stocking levels >2000 sph on most sites at low elevation

32. Example 2 - Wet Trench Climate and Vegetation • mean annual precip. 840 - 1537 mm • MAT 3.3 - 4.8 C (valley) -0.1- 0.3 C (mountain) • climax forests dominated by Cw and Hw (ICH), Sx (SBS), Bl and Se (ESSF) • Bl increases with elevation

33. Wet Trench Natural Disturbance Ecology • stand replacement disturbance cycle of 600 (valley) 800 (mountain) • hemlock looper, root disease, and stem decay are major disturbance agents in the absence of fire • over 80% of forest estimated to be >140-yrs-old and stands often exceed 200 yrs • 10% of total disturbed area in patches > 1000 ha, 60% 100 - 1000

34. Wet Trench Natural Disturbance Ecology (cont.) • an estimated 40-60% of dead wood volume created by gap replacement events • generally > 100 snags/ha in older stands • lower temporal or spatial variability in CWD volume • CWD volume generally exceeds 200m3/ha

35. Wet Trench Forest Management Effects • significant reduction in old forest • more stands with higher component of Sx • significant alteration of patch size distribution and shift from gap to stand replacement

36. Wet Trench Recommended Practices • well distributed fixed old growth reserves along with large patches on extended rotation (>150 yrs) • intensive management on smaller landbase • some proportion of landscape in young unsalvaged natural forest • more partial cutting especially along permanent road corridors and on steep slopes where high lead systems can be used • greater use of cedar and hemlock