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
Greg Sass

• Modeling Linkages Between Aquatic and Terrestrial
  Ecosystems
• September 26, 2002

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
Why model CWD dynamics?

• These are big systems with slow (and fast)
  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

1. Create CWD via riparian forest that can be
   affected by both natural and anthropogenic
   processes
2. Simulate realistic CWD densities that can be used
   to test hypotheses/ask questions about effect of
   CWD on fish communities

12
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)

Big tooth aspen (Populus grandidentata)
Paper birch (Betula papyrifera)
White pine (Pinus strobus)
Sugar maple (Acer saccharum)
14
Riparian Model Formulas

• SAPLINGS
• Si(t1) Si(t) Ai(t)ri (1-ajiAj(t)
  ajiAi(t)) - Si(t)gi
• ADULT TREES
• Ai(t1) Ai(t) Si(t)gi - mi Ai(t)
• STANDING SNAGS
• SSi(t1) SSi(t) (1-Li) mi Ai(t) - fi SSi(t)
• COARSE WOODY DEBRIS
• Di(t1) Di(t) (? fi SSi(t)) ? fi SSi(t) Li
  mi Ai(t) - (a11 a21) Di(t)

Shading terms
15
Conceptual Structure of the Wood Model
Hardwood Saplings
Softwood Saplings
Shading
()
()
(-)
(-)
Graduation
Graduation
Adult Hardwoods
Adult Softwoods
Recruitment
Recruitment
16
Model Scenarios

• 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

Little Rock Lake

• Development Scenario
• 1 annual loss of adult hardwoods and softwoods
• 5 annual loss of Snags and CWD

17
Adult Tree and CWD Dynamics During Baseline
Scenario
Adult Trees
CWD
18
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
Adult Tree and CWD Dynamics During Clearcut
Scenario
Adult Trees
CWD
22
CWD Dynamics During Clearcut Scenario
23
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
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
38
(No Transcript)
39
Fish Model Benthivore Biomass Equation

• dB/dtG-mB2-P2 P3
• GfishCg1 BugCg2
• Bt1Bt-harvest
• --------------------------------------------------
  -Functional Response
• Piscivory

v1
B2
c12
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