Understanding Aspen Decline in Northern Wisconsin: Factors and Impact

1. Aspen Mortality in Northern Wisconsin – Legacy of FTC Defoliation (It’s All Kyoko’s Fault) (Biocontrol of Aspen with EAB?) (It Started and Stopped Before I Started)

2. 2008 Lincoln County

3. 2008 Oneida County

4. 2008 Oneida County

5. 2009 Langlade County

6. 2009 Langlade County

7. Aspen Decline Stand Characteristics • Lost 6 - 18 ft2/ac of basal area 2 years prior to survey (majority of losses may have happened prior to 2006) • Averaged 39 ft2/ac of aspen (nearby unaffected stands averaged 69 ft2/ac) • 28 – 40 years old • 65% of soils are sandy loams; 20% are loamy sands • No apparent site quality differences between declining and non-declining stands

8. 80 ft2/ac aspen

9. 40 ft2/ac aspen

10. What’s Killing the Aspens?

12. EAB IS KILLING OUR ASPENS!

14. Bronze Poplar Borers (Agrilus liragus) Are Contributing to Aspen Mortality

15. Armillaria & Hypoxylon Are Contributing to Aspen Mortality • Roughly half of nearly-dead aspens estimated to be colonized by Armillaria

16. Armillaria & Hypoxylon Are Contributing to Aspen Mortality • Roughly half of nearly-dead aspens estimated to be colonized by Armillaria • The impact of hypoxylon canker is probably underestimated in decline surveys

17. Hypoxylon Canker

18. Hypoxylon Canker • Hypoxylon was the main aspen killer 6 years after FTC defoliation in MN (Churchill et al. 1964) • Strong evidence that Entoleuca (syn. Hypoxylon) can be a bark endophyte • Low bark moisture promotes canker development • Drought-stressed aspen are more susceptible to Hypoxylon canker Ostry & Anderson, Forest Ecology & Management 257, 2009

19. = Defoliation

20. Drought and Forest Tent Caterpillar Defoliation in North Central Wisconsin \ = moderate drought X = severe drought XX = extreme drought * = forest tent caterpillar defoliation

24. FTC Defoliation 2000

25. FTC Defoliation 2001

26. It’s All Kyoko’s Fault

27. Problems with Aspen in MN Too scattered Defoliation and Decline of Aspen, Unknown Cause(s), 2010, MN DNR Annual Report

28. 2010 MN Aspen Decline Surveys • MN DNR mapped less aspen decline this past year 2010 MI Aspen Decline Surveys • Expansion of declining stands has stopped • No new declining stands were detected

29. Aspen Decline Summary • From 2006 – 2009, significant dieback and mortality was present in aspen stands in north central Wisconsin • Majority of mortality in Wisconsin likely occurred between 2002 and 2006 • The spatial distribution of mortality was not obvious

30. Aspen Decline Summary • All areas with decline experienced FTC defoliation and drought in the last decade • A similar aspen decline occurred after extreme drought in the UP in the late 70s • In the 60s in MN, stands defoliated by FTC for 3 continuous yrs had 24 - 49% mortality in the 6 years after defoliation ended • The rate of decline appears to have slowed in 2010 in the upper Great Lakes states • The bronze poplar borer, Armillaria, & Entoleuca contributed to mortality • Significant mortality should be expected after several years of consecutive defoliation

31. (Churchill et al., Ecology, 1964)

32. SAD (Sudden Aspen Decline) Is Not Occurring in Northern Wisconsin • s.w. CO, s. UT, n. AZ (13% of aspen cover type in CO) • Widespread, rapid, severe crown deterioration; lack of regen. after overstory death • Predisposing factors: lower elevations; S and SW aspects • Inciting factors: warm, dry conditions • Contributing factors: Cytospora canker, poplar borer, bronze poplar borer, and two bark beetles • By 2060, 76% of the sites now exhibiting sudden decline are projected to lie outside aspen’s climate profile

33. Kemp, USFS, from http://www.aspensite.org/

34. Worrall, USFS, from http://www.aspensite.org/

35. Worrall, USFS, from http://www.aspensite.org/

36. Predicted Suitable Habitat for Aspen in 2100 (USFS Tree Atlas 1999)

37. Predicted Suitable Habitat for Aspen in 2100 (USFS Tree Atlas 2007)

38. ?s