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This study by Molly Hunter from Northern Arizona University evaluates the effectiveness of buffelgrass control treatments in Saguaro National Park from 2006 to 2010. By analyzing various factors such as treatment timing, frequency, and site characteristics, the research aims to provide insights into improving buffelgrass management strategies. Results indicate the impact of treatment regimes, aspect, rainfall, and slope on buffelgrass density and coverage.
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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 Molly.hunter@nau.edu
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
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
Results • Current buffelgrass coverage and density were lower in manual + herbicide treatments compared to herbicide only
Results • Percent change in patch size was lower on south-facing aspects
Results • Current buffelgrass density and coverage were higher on south-facing aspects
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