1. Effects of Clearcut Harvesting & Alternative Vegetation Management on Forest Microclimate P.E. Reynolds Canadian Forest Service Sault Ste. Marie, Ontario, Canada

2. Cooperators Ontario Forest Research Institute: R.A. Lautenschlager & F.W. Bell & University of Guelph: A.M. Gordon, J.A. Simpson, & D.A. Gresch

3. Specials thanks to: D.A. Buckley Canadian Forest Service Sault Ste. Marie, Ontario, Canada Retired

4. Objectives: To quantify treatment-related microclimatic differences resulting from harvesting & alternative vegetation management practices To assess the duration of these differences

5. Treatments: Unharvested forest (F) blocks -- 100 yrs; aspen, fir, white birch Clearcut control (C) -- harvested 1986 through 1988; planted with spruce 2 alternative herbicides, glyphosate (G) & triclopyr (T), applied August 1993 2 alternative cutting methods, brushsaws (B) & Silvana mower (S), September 1993

6. Methods: Vegetation treatments applied to 4 clearcut blocks (30-60 ha each). Weather stations established in F, C, B, and G treatments on 3 blocks 1994-1998 Programmed to continuously monitor PAR, RH, & air temperatures at 0.25 & 2.0 m above forest floor & soil temps at 5 & 15 cm Repeated measures ANOVA on 5th yr data

7. Results: Are based upon daily measurements of PAR, air & soil temperatures, & RH for the period Jun 2 through October 14, 1998 Data are means for 2 replicate blocks 5 years after B & G treatments 12 years after harvesting Significant treatment differences for 20 of 22 measured parameters

8. Lines fitted to data for viewing:

9. Results: Lower PAR & higher RH were observed for the unharvested forest (F) compared with the clearcut control (C)

12. PAR (uMol. S-1. M-2)

15. PAR (Mol. M-2. D-1)

18. Minimum Relative Humidity (%)

19. Results: Seasonal air temperature extremes (o C), for daily highs and lows, were associated with the glyphosate (G) treatment, where non- woody vegetation was dominant (J. Sust. For. 10, No. 3/4, 2000, pp. 267-275)

24. Air Temperatures (o C)

25. Results: Mean seasonal soil temperatures at 15 cm depth (daily highs) remained highest for the glyphosate (G) treatment, and higher than for all other treatments

28. Maximum Soil Temperature (o C)

29. Conclusions: The effects of routine forestry practices in altering forest microclimate are longer- lasting than anticipated Changes in forest microclimate are likely contributing to global warming & to global environmental change The extent & significance of these contributions are yet to be determined

33. Maximum Relative Humidity (%)

36. Minimum Soil Temperature (o C)