What Research Has Found about
Cogongrass Spread and Control in the
Longleaf Pine Ecosystem?
Shibu Jose
School of Forest Resources and Conservation
University of Florida
Can species rich longleaf
pine ecosystem resist
invasion by cogongrass?
Hypotheses
• Diverse communities use resources
more completely and are therefore
more resistant to invasion
• Diverse communities are more
probable to have a species that can
outcompete cogongrass or that can
limit congongrass growth and spread
Study 1: Black water river state forest
Study 1: Black water river state forest
• Selected four patches
per site
• Set up 20 2m x 1m
plots
• Used flags to mark
edge
• Remarked edge at each
observation interval
Study 1: Black water river state forest
• Once plots were
established, conducted
plant surveys
• Group plant species
into one of 5 functional
groups: annual forbs,
perennial forbs,
grasses, shrubs and
trees
2
1.80
2
Cogongrass Area Advanced (m /year)
2.00
Cogon grass Area Advanced (m /year)
Study 1: Species Richness or Functional
Richness Didn’t Matter!!!
1.60
1.40
1.20
1.00
0.80
0.60
y = 0.1232x + 0.5717
0.40
R2 = 0.112
P = 0.24
0.20
0.00
4.00
5.00
6.00
7.00
8.00
Species Richness/ m2
9.00
10.00
2.00
1.80
1.60
1.40
1.20
1.00
0.80
0.60
0.40
0.20
0.00
2.50
y = 0.0525x + 1.2125
R2 = 0.0015
P = 0.37
2.70
2.90
3.10
3.30
3.50
3.70
Functional richness/ m2
Collins et al. 2007, Biological Invasions
3.90
Native Plant Cover(%)
What does it mean for the longleaf pine
ecosystem?
y = 0.0199x 2 - 3.583x + 158.63
R2 = 0.8754
100
80
60
40
20
0
0
20
40
60
80
100
Cogongrass cover(%)
Reduction in species richness and diversity
Loss of Key Species?
Wiregrass
Cogongrass
Other Spp
.
Other Spp.
Non-infested area
Infested area
25
5.16
5.14
5.12
5.1
5.08
5.06
5.04
5.02
5
4.98
4.96
Available K (mg/kg)
pH
Changes in soil Properties
20
15
10
Cogongrass
Native
Cogongrass
Native
Shifts in ecosystem N pools
(E.g. 1 year-old-stand with and without cogongrass understory)
Pine
Below
Pine
Below
Above
Above
Changes in Fire Regime and Species Composition:
Mortality of Longleaf pine Seedlings and Saplings
100
% Mortality
Cogongrass
80
Sandhill
60
40
20
0
0-0.49
0.50-0.99
1.0-1.50
Height Class (m)
Lippincot, 1997
Mean Maximum Temp ( C)
Cogongrass burns hotter !!!
350
Cogongrass
Sandhill
300
250
200
150
100
0
0.5
1.5
Height (m)
Lippincot, 1997
Study 2. Are there any species out there
that could outcompete cogongrass?
Study 2. Treatments
Treatment
1. Control
2. A. stricta monoculture
3. A. viriginicus monoculture
4. I. glabra monoculture
5. C. fasciculata monoculture
6. P. graminifolia monoculture
7. Grass mix - A. stricta and A. viriginicus
8. Forbs mix - C. fasciculata and P.
graminifolia
9. 3-Species A. stricta, I. glabra, and C.
fasciculata
10. 5-Species A. stricta, A. viriginicus, I. glabra,
C. fasciculata, and P. graminifolia
Functional group(s)
Grass
Grass
Shrub
Forb
Forb
Grasses
Forbs
Richness
0
1
1
1
1
1
2
2
Grass, Shrub, Forb
3
Grass, Shrub, Forb
5
Daneshgar 2007
Gallberry (Ilex glabra)
Broomsedge (Andropogon virginicus)
Narrowleaf Silkgrass
(Pityopsis graminifolia)
Wiregrass (Aristida stricta)
Partridge Pea (Chamaecrista fasciculata)
Study 2. Cogongrass Introduction and
Measurements
Mesocosm communities were
established and allowed to
grow for one year
Cogongrass was introduced
as a single seedling in the
center of the mesocosm in
April
Allowed to grow until midAugust; % cover estimated
biweekly; above and
belowground biomass
harvested and weighed
% cover of cogongrass
Study 2. Again, species richness or
functional richness didn’t matter!!
% cover of native species
Daneshgar and Jose 2007, in review
Study 2. Sampling effect was more
pronounced than diversity effect!!
Control
Gallberry
wiregrass
Partridge pea
Broomsedge
Daneshgar and Jose 2007, in review
Study 2. How does A. virginicus resist the
invasion by cogongrass?
Percent root mass at different soil depth by species
Species
A. stricta
In monoculture
0-20 cm 20-40 cm 40-60 cm
87.5
12.5
0
With competition
0-20 cm 20-40 cm 40-60 cm
98
2
0
I. glabra
59.5
28.75
11.75
100
0
0
C. fasciculata
98.25
1.75
0
100
0
0
P. graminifolia
91
9
0
100
0
0
A. virginicus
77.5
17
5.5
75
19
6
I. cylindrica
75
24
1
95
4
1
Daneshgar and Jose 2007, in review
How can we restore infested longleaf pine
stands?
• Depends on the degree of infestation
– Young or sparse infestations - chemical
control
– Well-established dense infestations –
• First line of attack - mechanical, including fire
depending on stand conditions
• Then chemical control
• Ultimately revegetation with species or species
mixes that can outcompete cogongrass
Successful Restoration: Which ladder do
you take when it comes to cogongrass
control?
THANK YOU