The Influence of Natural and Anthropogenic Perturbations on Lake Riparian Forest and Coarse Woody Debris

1. The Influence of Natural and Anthropogenic Perturbations on Lake Riparian Forest and Coarse Woody Debris Modeling Linkages Between Aquatic and Terrestrial Ecosystems September 26, 2002 Greg Sass

2. This is a collaborative effort! • NSF-Biocomplexity Project • Dr. Monica Turner • Dr. Stephen Carpenter • Isaac Kaplan, Anna Sugden-Newbery, Anthony Yannarell, Theodore Willis, Greg Sass • Scott van Egeren, Michelle Parara

3. Biocomplexity Riparian forest, land, people, and lakes http://limnology.wisc.edu Click on research link, follow to biocomplexity web page

4. Relationship between CWD density and shoreline development in N. Wisconsin lakes • Also true • for MN • macrophytes! CWD Density (no./km) Shoreline Development From Christensen et al. 1996

5. Relationship between fish growth and coarse woody debris (CWD) in N. Wisconsin lakes Undeveloped Undeveloped log Growth Rate (mm/yr) Low Development Low Development High Development High Development CWD Density (no./km) From Schindler et al. 2000

6. How are changes on land and land/water interface reflected in the adjacent lake ecosystem? • Does the riparian forest influence fish populations? • The riparian forest is linked to fish through Coarse Woody Debris (CWD)

7. CWD abundance influenced by: • Forest structure (Harmon et al. 1986, Hely et al. 2000) • Successional state • Natural and anthropogenic disturbance (Christensen et al. 1996, Guyette and Cole 1999 , Hely et al 2000) • Windthrows • Logging • Lakeshore development Photo courtesy of Michelle Parara

8. These are big systems with slow (and fast) dynamics!! Why model CWD dynamics? Photo courtesy of Michelle Parara

9. 923 year-old white pine in Swan Lake, Ontario Guyette and Cole 1999

10. Three Aspects Compose the Linked Terrestrial-Aquatic Model Terrestrial-Aquatic Interface Aquatic Terrestrial Fish Model Riparian Model

11. Main Goals of the Wood Model • Create CWD via riparian forest that can be affected by both natural and anthropogenic processes • Simulate realistic CWD densities that can be used to test hypotheses/ask questions about effect of CWD on fish communities

12. Snags Conceptual Structure of the Wood Model Recruitment Saplings Falling away from water Graduation Adults Trees that die and stay upright Trees that die and fall immediately CWD Falling Falling away from water Loss to decay and deep water

13. Two Pools of Trees: • “Softwoods” • Representative of early succession canopy • Paper birch (Betula papyrifera), aspens (Populus spp) • “Hardwoods” • Representative of mid-late succession canopy • White pine (Pinus strobus), sugar maple (Acer saccharum) Paper birch (Betula papyrifera) Big tooth aspen (Populus grandidentata) White pine (Pinus strobus) Sugar maple (Acer saccharum)

14. SAPLINGS Si(t+1) = Si(t) + {Ai(t)ri *(1-αjiAj(t)– αjiAi(t))} - Si(t)gi ADULT TREES Ai(t+1) = Ai(t) + Si(t)gi - mi Ai(t); STANDING SNAGS SSi(t+1) = SSi(t) + (1-Li) mi Ai(t) - fi SSi(t); COARSE WOODY DEBRIS Di(t+1) = Di(t) + (γfi SSi(t)) + {γfi SSi(t)Li mi Ai(t)} - (a11 + a21) Di(t) ; Riparian Model Formulas “Shading” terms

15. Conceptual Structure of the Wood Model Hardwood Saplings Softwood Saplings “Shading” (+) (+) (-) (-) Graduation Graduation Adult Hardwoods Adult Softwoods Recruitment Recruitment

16. Baseline Scenario Riparian forest density from Turner 2001 and Christensen et al. 1996 CWD values from undeveloped Little Rock Lake in Vilas County, WI Windthrow Scenario 65% instantaneous death of hardwood and softwood adults and snags Clearcut Scenario 95% instantaneous death of hardwood and softwood adults and snags Development Scenario 1% annual loss of adult hardwoods and softwoods 5% annual loss of Snags and CWD Model Scenarios Little Rock Lake

17. Hardwoods Softwoods Adult Tree and CWD Dynamics During Baseline Scenario Adult Trees CWD

18. Hardwoods Softwoods Adult Tree and CWD Dynamics During Windthrow Scenario Adult Trees CWD

19. CWD Dynamics During Windthrow Scenario

20. CWD Abundance (all Trees) Following FireDisturbance Hely et al. 2000

21. Hardwoods Softwoods Adult Tree and CWD Dynamics During Clearcut Scenario Adult Trees CWD

22. CWD Dynamics During Clearcut Scenario

23. Hardwoods Softwoods Adult Tree and CWD Dynamics During Development Scenario Adult Trees CWD

24. CWD Dynamics during Development Scenario

25. Can the model mimic ‘real’ history? Lakeshore Development Last ~50 years Skidding Logs, Upper Chippewa Basin, Circa 1890

26. Hardwoods Softwoods Taming the Northwoods Development Clear cut Adult Trees CWD

27. CWD Dynamics in Clearcut + Development Scenario

28. Summary of Wood Model • Model is simple, but fairly realistic • Windthrows and clearcuts have long-term effects on CWD pool • Development a powerful force

29. Conclusions • This ecosystem-level model is a useful tool for creating questions about CWD inputs/removals. • Can we devise ways to observe long-term changes in riparian forest and CWD structure? • Does indiscriminate thinning actually occur? • How long does it take for the CWD pool to recover? • How do changes in CWD abundance affect fish communities? • How can we obtain answers to these questions?

30. Biocomplexity Cross-lakes Crew • Led by Michelle Parara and Scott van Egeren • Riparian forest/CWD analysis: Anna Sugden-Newbery

31. Modeling linkages between terrestrial and aquatic ecosystems part II:The influence of riparian forest dynamics on aquatic food webs Isaac Kaplan, Tanya Havlicek, Pieter Johnson, Brian Roth,Greg Sass, Anna Sugden-Newbery, Theodore Willis, Anthony Yannarell, Monica Turner, and Steve Carpenter

32. Biocomplexity Riparian forest, land, people, and lakes

33. Relationship between fish growth and coarse woody debris in N. Wisconsin lakes Undeveloped Undeveloped log Growth Rate (mm/yr) Low Development Low Development High Development High Development Coarse Woody Debris Density (no./km) From Schindler et al. 2000

34. Conceptual Model Terrestrial Terrestrial-Aquatic interface Aquatic Growth Senescence Aquatic Food Web coarse woody debris Forest Windthrow Humans Fishing Development Decay/ Physical Transport

35. Questions • How does the aquatic food web respond to stable levels of coarse woody debris? • How does the food web respond to perturbations? - windthrow, development, fishing • How can we learn about effects of coarse woody debris on fish predation and growth rates in experimental lakes?

36. Fish biomass dynamics model adult piscivore juv. piscivore benthivore insects

37. Hypothesized Effects of Coarse Woody Debris on Fish Community

39. Fish Model: Benthivore Biomass Equation dB/dt=G-mB2-P2 –P3 G=fishC*g1 +BugC*g2 Bt+1=Bt-harvest ---------------------------------------------------Functional Response: Piscivory v1 c12 B2 B1-V1 V1 h1 hiding vulnerable predators

40. Hypothesis 1: Similar piscivore and benthivore behavioral response to logs

41. logs / km of shoreline

42. Hypothesis 2: Benthivore is less dependent on refuge than piscivore

43. logs / km of shoreline

44. Windthrow fishing starts

45. Development fishing starts

46. Conclusions • Coarse woody debris could be a major driver of fish community dynamics (and we will test this) • Effect of development is much greater than effect of windthrow • For benthivore, moderate reductions in coarse woody debris may be balanced by fishing on piscivore • Help Greg chop down trees this winter

47. Work in Progress Field experiments in N. Wisconsin: • Removal of coarse woody debris from Little Rock Lake • Addition of coarse woody debris to Camp Lake • Observations of growth and abundance • Estimation of predation and vulnerability parameters and hypothesis testing

48. Acknowledgements Michele Parara, Scott VanEgeren, and the Biocomplexity Field Crew This work is funded by the National Science Foundation under Cooperative Agreement #DEB-0083545

49. Increasing vulnerability of benthivore Increasing vulnerability of benthivore