Download Exotic grass and forb control in a California grassland - Cal-IPC

Non-native grass and forb
control in a California
grassland
S.J.M. Dickens & E.B. Allen
University of California-Riverside
Outline
• Overview:
– non-natives in grasslands
– prescribed burns
•
•
•
•
•
Santa Rosa Plateau Ecological Reserve
Objectives and hypotheses
Methods
Results
Conclusion, implications and future work
Non-natives in California Grasslands
• Non-native grasses arrived about 250 years ago
• Pre-invasion plant community unknown
• Non-native grasses compete with and displace native
plant species.
– Water, Nutrients, Space, Light
• In the presence of non-native annual grasses, non-native
forbs act as place holders for native forbs, without
grasses they can become competitors (Gillespie & Allen
2004).
Prescribed Fire
• Can reduce seed input by 96% (Moyes et al 2005)
• Prescribed fire may reduce non-native annual grass
cover but may not increase native forb cover (Dickens &
Allen 2009).
1cm
• Non-native forbs, specifically Erodium spp., often replace
non-native grass after fire (Dickens & Allen 2009).
Santa Rosa Plateau
Ecological Reserve
• 8000 acres of land and 5 distinct habitats
• 48cm precipitation annually, most of which falls
from November to April
• Historically grazed by cattle
• Home to many rare and
endangered plants and animals
Major Non-native Grasses of Santa Rosa Plateau
Amsinckia menziesii
Calandrinia ciliata
Viola pedunculata
Nassella
Avena
fatua
Bromus
Hordeum
Vulpia
Bromus
Bromus
Eschscholzia californica
Sidalcea malvaeflora
pulchra
& A. barbata
rubens
spp
myuros hordeaceus diandrus
Prescribed Fire History
• 1988 Prescribed burning program began
– Spring burns to capture seed on standing
biomass
– Burns reduce non-native grass seed input and
thatch cover (Hervey 1949, Moyes et al 2005,
White et al 2006)
Objectives: Assess effectiveness of fire and
weeding of non-natives in releasing native
species from competition.
Hypothesis:
• fire will reduce exotic grass cover and increase
native cover.
• weeding of non-natives will further increase
native cover and richness.
Methods
• Wildfire of 2006
Picture: Don Baccus
• 27 1x1m plots were established in burned and unburned
areas (unburned, burned, burn + weeded)
• Plots were weeded up to 3 weeks before data collection.
• Plant cover and richness recorded at peak of season
Unburned
Burned
Burned + Weed
Total Monthly Precipitation
Total monthly precipitation (cm)
50
Annual Totals
2005 = 128
2006 = 41
2007 = 12
2008 = 50
2009 = 41
40
30
20
10
0
2005
2006
2007
2008
2009
Data supplied by Riverside County Flood Control and Water Conservation District
Species Richness
Non-native
Native
10
10
8
Unburned
Burned
Burned + Weed
A
A
8
A
B
6
B
AA
B
4
4
B
A A
2
0
A
A
B
2006
2
AB
B
A
B
B
2007
2008
6
2009
2006
Total species richness per 0.5m2.
ANOVA’s from individual years.
0
2007
2008
2009
Non-native Species Percent Cover
Grass
Forb
60
50
100
Unburned
Burned
Burned + Weed
A
A
80
A
A
40
60
A
B
30
40
20
A
10
2007
B
C
C
B B
2006
20
A
C
0
B
A
B
B
2008
2009
0
2006
2007
Non-native species percent cover per 0.5m2.
ANOVA’s from individual years.
2008
2009
Native Species Percent Cover
Grass
Forb
25
20
80
Unburned
Burned
Burned + Weed
A
A
A
60
AB
15
40
B
10
B
B
B
B
5
AB
0
2006
2007
2008
2009
2006
20
0
2007
Native species percent cover per 0.5m2.
ANOVA’s from individual years.
2008
2009
Conclusions
• Fire decreased non-native grass cover for the length of
the study.
• Native species richness was initially increased with both
fire treatments.
• The increase in native diversity is mainly in fire following
species.
• Non-native forb cover increased with burning
• Native forb cover increased in burn + weeding
treatments.
• Erodium spp are competing with Nassella pulchra
slowing recovery.
Management Implications
• Weeding is not logistically realistic for large
areas. Further research using herbicide
following fire is necessary.
• Management practices may take multiple years
of application.
• Precipitation in the season of and following
management will be important but unpredictable.
Future work
• Following the plant community recovery one
more year.
• Testing herbicide methods for non-native forb
control after fire.
– Roundup and Fusilade following Erodium spp
germination.
– seeding treatments to test seed-bank limitations.
Acknowledgements
• Dr. Edith Allen
Funding Sources:
• Carole Bell
– Skinner-Shipley/Riverside
• The Dr. E.B. Allen & Dr L.
County Endowment
Santiago Laboratories
• Santa Rosa Plateau Ecological
– University of California
Riverside Department of Botany
Reserve
and Plant Sciences
• California Department of Fish
and Game
• The Nature Conservancy