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Effectiveness and longevity of buffelgrass treatments in sAguaro National Park

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.

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Effectiveness and longevity of buffelgrass treatments in sAguaro National Park

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  1. 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

  2. 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

  3. 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)

  4. Rincon Mountain District Tucson Mountain District

  5. Other variables • Rainfall (total rainfall 1 month prior to treatment) • Aspect (N, S, E, W) • Time since last treatment (months) • Slope (%)

  6. 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

  7. Statistics • Categorical variables • Non-parametric tests (van der Waerden chi square, Wilcoxon test) • Continuous variables • Spearman’s correlation

  8. Results • Change in patch size was lowest when two seasons were skipped • No other variables impacted by treatment regime

  9. Results • Current buffelgrass coverage and density were lower in manual + herbicide treatments compared to herbicide only

  10. Results • Percent change in patch size was lower on south-facing aspects

  11. Results • Current buffelgrass density and coverage were higher on south-facing aspects

  12. 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)

  13. 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)

  14. 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

  15. 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

  16. Acknowledgements • Dana Backer and Perry Grissom (SNP) • Leigh Perry (UA) • NPS Fuels Reserve Fund

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