Effects of Gopher Mounds on Plant Species Diversity in a Meadow System

1
Effects of Gopher Mounds on Plant Species
Diversity in a Meadow System

• Nina Griffin
• EcoInformatics Summer Institute
• HJ Andrews Experimental Forest
• August 24, 2007

Advisor Dr. Charlie Halpern University of
Washington
2
Introduction

• Pocket Gophers
• Small rodents that tunnel underneath the soil and
  deposit as mounds.
• Diet Forbs mostly, and some grasses
• MoundsDisturbance
• Reduces competition
• Increases diversity

http//snohomish.wsu.edu/photos/gopher2.jpg
3
The Intermediate Disturbance Hypothesis

• When disturbance is too small and infrequent OR
  too large and frequent Little/no species
  diversity.
• At intermediate sizes and frequencies Maximum
  species diversity

http//www.epa.gov/watertrain/ecology/s18.jpg
4
Previous Research Diversity-Disturbance
Relationship

• IDH modeled in tropical rain forests, coral reef
  systems, phytoplankton marine communities
• Positive relationship
• Negative relationship
• No relationship
• Bimodal curve
• Each ecosystem is unique and needs to be studied
  individually.

5
Previous Research Gopher Mounds and Plant
Diversity

• Little research with conflicting results on
  gopher mounds in meadow systems.
• Rogers et al (2001) - Prairies ? Decrease
• Olff and Ritchie (1998) Grasslands ?
  Increase or decrease
• Huntly (1994) Meadows ? Increase

6
Objectives

• Relationship between mound activity and plant
  species diversity in a meadow ecosystem.
• Test IDH for this ecosystem.

7
Methods

• Site Lodgepole Pine Meadow, Bunchgrass Ridge,
  Oregon.

8
(No Transcript)
9
Methods

• Collection Ten - 2mx2m plots randomly
• 1mx1m subplots within
• Plant species and abundance
• Mound size and age
• Fresh, Young, Old
• Used Excel to analyze data

10
(No Transcript)
11
(No Transcript)
12
Grasses Abundance()
Agropyron repens 2.6
Bromus carinatus 12.8
Danthonia intermedia 4
Elymus glaucus lt1
Festuca idahoensis 44.6
Poa prantensis 1

Forbs
Achillea millefolium 8.3
Agoseris aurantiaca lt1
Aster occidentalis 1
Cirsium callilepis 4.1
Erigeron aliceae 5
Fragaria vesca 4
Hieracium gracile 3
Lupinus latifolius 1
Orthocarpus imbricatus 2.8
Phlox diffusa 12.5
Pteridium aquilinum 7
http//www.baynatives.com/plants/Festuca-idahoensi
s/
http//www.fs.fed.us/database/feis/plants/graminoi
d/brocar/all.html
http//www.larkspurbooks.com/Polem1.html
13
Results

• No clear relationship between species richness
  and disturbance.
• IDH is NOT followed.

14
Fresh mounds, 1mx1m subplots
Young mounds, 1mx1m subplots
Shannon-Weiner, 1mx1m subplots
IDH is not followed by this system on the scale
of one meadow.
15
Plant Cover

• Graminoidsgrasses
• Dominant plant type in meadow
• Lowest abundance on Fresh mounds
• Greatest on Old mounds
• Forbsnon-grasses
• Greatest abundance on Fresh mounds
• Lowest on Old mounds
• Fresh mounds DO reduce competition and alter the
  composition of the plots.

16
Factors that Affect Diversity

• Disturbance
• Soil composition
• Nutrient availability
• Precipitation
• Snow Pack
• Distance

17
Spatial Analysis

• Pairs of 1mx1m subplots (MM, NN, MN)
• Distance (meters) between
• Difference in species richness
• Difference in Shannon-Weiner Index
• Number of species shared

18
(No Transcript)
19
Number of species shared decreases with distance
20
Plot type Distance (m) Mean
M, M 0-2 0.38
N, N 0-2 0.46
M, N 0-2 1.00
Difference in species richness increases with
distance.
21
Spatial Analysis Conclusions

• Distance IS a confounding factor
• Subplots closer together shared more species than
  those further apart.
• Subplots further apart had a greater difference
  in species richness.
• Although mounds alone do not increase diversity,
  they contain different species and so add
  diversity.

22
Why is this important?

• Grassland and meadow biodiversity
• Herbivores controlling species diversity
• Gophers labeled as pests
• This study suggests that they arent!

23
Future Studies

• Look at other factors soil, precipitation.
• Larger spatial scale multiple meadows
• Create a model to show succession in the system
  over time and the effects on plant species.

24
Acknowledgements

• National Science Foundation
• Charlie Halpern, Desiree Tullos, Nicole
  Czarnomski, Julia Jones, and Jorge Ramirez.

25
Works Cited
Aronson, R.B., and Precht, W.F. 1995. Landscape
patters of reef coral diversity a test of the
intermediate disturbance hypothesis. Journal of
Experimental Marine Biology and Ecology 1921-14.
Coggins, S.T. and Conover, M.R. 2005. Effects
of pocket gophers on the herbaceous vegetation
growing in aspen meadows. Wildlife Society
Bulletin 331210-1215. Fox, J.F., and Connell,
J.H. 1979. Intermediate-Disturbance Hypothesis.
Science 204 1344-1345. Gibson, D.J. 1989.
Effects of Animal Disturbance on Tallgrass
Prairie Vegetation. American Midland Naturalist
121144-154. Huntly, N., and Reichman, O.J.
1994. Effects of subterranean mammalian
herbivores on vegetation. Journal of Mammalogy
75 852-859. Inouye, R.S., N. Huntly, and Wasley
G.A. 1997. Effects of pocket gophers (Geomys
bursarius) on microtopographic variation.
Journal of Mammalogy 78 1144-1148. Inouye, R.S.,
N.J. Huntly, D. Tilman, and Tester, J.R. 1987.
Pocket gophers (Geomys bursarius), vegetation,
and soil nitrogen along a successional sere in
east central Minnesota. Oceologia 73
178-184. Johst, K., and Huth, A. 2005. Testing
the Intermediate Disturbance Hypothesis When
will there be two peaks of diversity? Diversity
and Disturbances 11111-120. Jones, C. C.,
Halpern, C. B., and Niederer, J. In review. 
Plant succession on gopher mounds in western
Cascade meadows  consequences for species
diversity and heterogeneity. American Midland
Naturalist. Klaas, B.A., Danielson, B.J.,
Moloney, K.A. 1998. Influence of pocket gophers
on meadow boles in a tallgrass prairie. Journal
of Mammalogy 79942-952. Kondoh, M. 2001.
Unifying the relationships of species richness to
productivity and disturbance. Biological
Sciences 268269-271. Kovacs, M. ed. 1992.
Biological Indicators in Environmental
Protection. Ellis Horwood, London, England, pgs
23-24. Molino, J-F., and Sabatier, D. 2001. Tree
diversity in tropical rain forests a validation
of the Intermediate Disturbance Hypothesis.
Science 2941702-1704.
Olff H. and Ritchie, M.E. 1998. Effects of
herbivores on grassland plant diversity. TREE
13261-266. Pain. R.T. 1966. Food web
complexity and species diversity. The American
Naturalist 10065-75. Proulx, M., and Mazumder,
A. 1998. Reversal of grazing impact on plant
species richness in nutrient-poor vs.
nutrient-rich ecosystems. Ecology
792581-2592. Rogers, W.E., Hartnett D.C., and
Elder, B. 2001. Effects of plains Pocket Gopher
(Geomys bursarius) disturbances on
tallgrass-prairie plant community structure.
American Midland Naturalist 145344-357.
Sommer, U. 1995. An experimental test of the
intermediate disturbance hypothesis using
cultures of marine phytoplankton. Limnology and
Oceanography 401271-1277. Teipner, C.L., Garton,
E.O., and Nelson, L. 1983. Pocket Gophers in
Forest Ecosystems. Ogden, Utah U.S. Dept. of
Agriculture, Forest Service, Intermountain Forest
and Range Experiment Station.