Transcript Document

Mechanisms driving nonnative
plant-mediated change in small
mammal populations and
communities
Dan Bachen
Approach and Methods
http://www.stolaf.edu/depts/environmental-studies/courses/es-399%20home/
es-399-05/Projects/Jared's%20Senior%20Seminar%20Research%20Page/htt.htm
Question 1
Do invasive species alter the structure of the
vegetation and the food resources within the
ecosystem?
• Answering question will provide:
– What factors change
• native vs. invasive dominated
– Quantifications of these changes
• To answer:
– Literature Review
– Focused Research at Site
Types of factors:
• Vegetation
• Food resources
– Granivorous
– Insectivorous
– Herbivorous
Vegetation analysis
• Horizontal vs vertical
Measurement Techniques:
Vegetation
• Horizontal Structure:
• Techniques:
– Quadrat
• % cover
– Stem/area
Measurement Techniques:
Vegetation
• Vertical Structure
• Techniques:
– Sidelook
Measurement Techniques:
Food Resources
• Grain
• Techniques:
– Count -> Density
• Biomass
http://www.nouriche.com/NutriorWheatProtein.html
Measurement Techniques:
Food Resources
• Arthropods
• Techniques:
– Pitfall
– biomass
Measurement Techniques:
Food Resources
• Edible Vegetation
• Techniques:
– % cover
– Clip-> dry weight
– Biomass
Question 2
Is there evidence that small mammal communities and
species abundance are influenced by the structure of
their habitat’s vegetation and by the available food
resources?
• Answering question will provide:
– Basis for asking future questions
• To answer:
– Literature review
• Established correlation
Question 3
Can native plant communities be manipulated in such a
way that the alterations mimic those induced by the
presence of non-native plants?
• Answering question will provide:
– Tested treatments of isolated factors
• To answer:
– Use previous knowledge to ID important potential factors
– Test treatments for factors
– Confirm
Question 3
• Use previous knowledge to ID important potential
factors
– Question 1: All potential factors
– Question 2: Factors previously correlated
– Combination
Question 3
• Test
– 10x10 m test plot(s)
– Control
– Quantify
• Measurement methods used in Question 1
– Success of treatment based on ability to mimic
characteristic of invasion
Question 4
Can the consequences of manipulating the
physiognomy of the vegetation and the available food
resources be quantified in small mammal community
structure and species abundance? If so what are the
effects?
• Answering question will provide:
• To answer:
– Treat plots
– Assess:
•
•
•
•
small mammal population demography
species abundance
Species richness
Vegetation
Experimental Design
• Sample Plots
– 1ha (100m x 100m)
• Selection
– Random sampling
– Randomization of treatments
• Treatment plots
• Control plots
• Grid numbers sampled
– Replicate plots per treatment
– Paired with 4 “control” plots
Experiment Design
– Trapping
• Each plot trapped 5 nights
• 10x10 grid of Sherman live traps
http://www.depauw.edu/univ/naturepark/classes/sma
ll%20mammals.asp
Capture Mark Recapture
• Marks
– Ear tag
– Sharpie marker
• Processing
–
–
–
–
–
Species
Age-class
Sex
Reproductive status
Weight
http://www.flickr.com/photos/captainschlumpy/3961667069/
Analysis of Data
• Species Abundance: estimate of number of
animals per plot
– Ideally by age class
• Account for age-class heterogeneity
– CMR Data
– Model in Program Mark
– Results expected
Analysis of Data
• Species richness: Measure of number of
species on each plot
– Similar to CMR for species but uses species as
“individuals”
• Accounts for species heterogeneity
– Analyzed in MARK
– Expected Results
Analysis of Data
• Species demographics: The proportion of
animals in a given age class in a population
– Data from CMR
– Analyzed in MARK
– Expected results
– Important Why?
Analysis of Data
• Method of comparison
– Treatment vs Control
– Two sample t-test
– Significance level
Vegetation confirmation
• Re-sample vegetation
– Confirmation of isolation of factor
– If different provide opportunity to reassess
statistical methods
Question 4
Can the consequences of manipulating the
physiognomy of the vegetation and the available food
resources be quantified in small mammal community
structure and species abundance? If so what are the
effects?
Question 5
Is there a plausible explanation for how the treatments
affected (or didn’t affect) the community structure and
species abundance of the small mammals?
• Answering question will provide:
– Confidence in results
• To answer:
– Explore logical explanations
Summary
• Do invasive species affect habitat?
• Does habitat affect small mammals?
• Can I mimic the habitat alterations caused by
invasive plants?
• What are the effects of the application of
these treatments on small mammals?
• Do the effects seen make logical sense?
Questions?