effectiveness and longevity of buffelgrass treatments in saguaro national park
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Effectiveness and longevity of buffelgrass treatments in sAguaro National Park. Molly Hunter Assistant Research Professor Northern Arizona University, School of Forestry [email protected]. Objectives. - PowerPoint PPT PresentationTRANSCRIPT
EFFECTIVENESS AND LONGEVITY OF BUFFELGRASS TREATMENTS IN SAGUARO NATIONAL PARK
Molly HunterAssistant Research ProfessorNorthern Arizona University, School of [email protected]
Objectives• Assess the effectiveness of different buffelgrass control
treatments (i.e. manual pulling, herbicide application)
• Determine how buffelgrass treatment effectiveness is impacted by factors such as treatment timing, treatment frequency, and site characteristics
Saguaro National Park• Examined treatments from 2006
– 2010• Data collected in 2010• Two types of treatments
• Herbicide only• Manual pulling followed by herbicide
• Two treatment seasons• Winter (October – May)• Summer (June – September)
Rincon Mountain District Tucson Mountain District
Treatment regime Treatment type
Number of patches
Description
Three consecutive treatments
Chemical 15 Three herbicide treatments occurring in consecutive seasons.
Three consecutive treatments
Chemical + manual
11 Three treatments (one manual followed by two herbicide) occurring in consecutive seasons.
Two consecutive seasons
Chemical 28 Two herbicide treatments occurring in consecutive seasons.
Two consecutive seasons
Chemical + manual
15 Two treatments (one manual followed by one herbicide) occurring in consecutive seasons.
One skipped season Chemical 15 Two herbicide treatments occurring in nonconsecutive season (one winter or summer season skipped)
One skipped season Chemical + manual
10 Two treatments (on manual followed by one herbicide) occurring in two nonconsecutive seasons (one winter or summer season skipped)
Two skipped seasons Chemical 12 Two herbicide treatments occurring in nonconsecutive seasons (one winter season and one summer season skipped)
Other variables• Rainfall (total rainfall 1 month prior to treatment)• Aspect (N, S, E, W)• Time since last treatment (months)• Slope (%)
Response variables• Current density (individuals m-2)• Current coverage (m2 – percent cover X patch size)• Percent change in patch size (time of first treatment
compared to summer 2010)• Percent change in density• Percent change in coverage
Statistics• Categorical variables
• Non-parametric tests (van der Waerden chi square, Wilcoxon test)• Continuous variables
• Spearman’s correlation
Results• Change in patch size was lowest when two seasons were skipped
• No other variables impacted by treatment regime
0
10
20
30
40
50
60
70
80
90
100
Cha
nge
in p
atch
siz
e (%
) ab a a
b
Results• Current buffelgrass coverage and density were lower in
manual + herbicide treatments compared to herbicide only
Chemical only Manual and Chemical0
0.2
0.4
0.6
0.8
1
1.2
1.4
Cur
rent
buf
felg
rass
indi
vid-
uals
m-2
Chemical only Manual and Chemical0
1
2
3
4
5
6
7
Cur
rent
buf
felg
rass
cov
erag
e (
m2)
Results• Percent change in patch size was lower on south-facing aspects
North East South West0
20
40
60
80
100
120
Cha
nge
in p
atch
siz
e (%
)
a a ab
b
Results• Current buffelgrass density and coverage were higher on
south-facing aspects
North East South West0
1
2
3
4
5
6
7
8
Dominant aspect
Cur
rent
buf
felg
rass
cov
erag
e
b
ab
a a
North East South West0
0.5
1
1.5
2
2.5
Dominant aspect
Cur
rent
buf
felg
rass
indi
vid-
uals
m2 b
a
ab
a
Results• Percent slope was negatively correlated with change in
patch size (-0.24) and change in density (-0.30)
• Percent slope was positively correlated with current density (0.32) and current coverage (0.35)
Results• Rainfall was positively correlated with percent change in
coverage (0.27)
• Rainfall was negatively correlated with current density (-0.23) and current coverage (-0.20)
Uncertainties• Time since last treatment was not significant, but time
frame of study was short
• Distance to roads/trails/drainages, soil type, and temperature not assessed
• Influence of original patch size, cover and density not assessed
Conclusion• Most plots showed reductions in patch area greater than 90%
• Skipping two full treatment seasons (one winter and one summer) may result in less successful control of buffelgrass
• Combination treatments may be slightly more effective than herbicide only treatments
• Buffelgrass abundance measures were consistently higher on south-facing aspects
• Buffelgrass treatments were less effective on steep slopes
Acknowledgements• Dana Backer and Perry Grissom (SNP)• Leigh Perry (UA)• NPS Fuels Reserve Fund