Effectiveness and longevity of buffelgrass treatments in sAguaro National Park

Assessment and guidelines for determining effectiveness and longevity of buffelgrass treatments in southern Arizona

Effectiveness and longevity of buffelgrass treatments in sAguaro National ParkMolly HunterAssistant Research ProfessorNorthern Arizona University, School of ForestryMolly.hunter@nau.edu

ObjectivesAssess 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 characteristicsSaguaro National ParkExamined treatments from 2006 2010Data collected in 2010Two types of treatments Herbicide onlyManual pulling followed by herbicideTwo treatment seasonsWinter (October May)Summer (June September)

Rincon Mountain DistrictTucson Mountain DistrictTreatment regimeTreatment typeNumber of patchesDescriptionThree consecutive treatmentsChemical15Three herbicide treatments occurring in consecutive seasons. Three consecutive treatmentsChemical + manual11Three treatments (one manual followed by two herbicide) occurring in consecutive seasons.Two consecutive seasonsChemical28Two herbicide treatments occurring in consecutive seasons.Two consecutive seasonsChemical + manual15Two treatments (one manual followed by one herbicide) occurring in consecutive seasons.One skipped seasonChemical15Two herbicide treatments occurring in nonconsecutive season (one winter or summer season skipped)One skipped seasonChemical + manual10Two treatments (on manual followed by one herbicide) occurring in two nonconsecutive seasons (one winter or summer season skipped)Two skipped seasonsChemical 12Two herbicide treatments occurring in nonconsecutive seasons (one winter season and one summer season skipped)Other variablesRainfall (total rainfall 1 month prior to treatment)Aspect (N, S, E, W)Time since last treatment (months)Slope (%)Response variablesCurrent 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 densityPercent change in coverage

StatisticsCategorical variablesNon-parametric tests (van der Waerden chi square, Wilcoxon test)Continuous variablesSpearmans correlationResultsChange in patch size was lowest when two seasons were skippedNo other variables impacted by treatment regimeResultsCurrent buffelgrass coverage and density were lower in manual + herbicide treatments compared to herbicide onlyResultsPercent change in patch size was lower on south-facing aspectsResultsCurrent buffelgrass density and coverage were higher on south-facing aspectsResultsPercent 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)ResultsRainfall was positively correlated with percent change in coverage (0.27)

Rainfall was negatively correlated with current density (-0.23) and current coverage (-0.20)

UncertaintiesTime 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 assessedConclusionMost 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 slopesAcknowledgementsDana Backer and Perry Grissom (SNP)Leigh Perry (UA)NPS Fuels Reserve Fund