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ProblemSolvingStrategies forCompacted Soils

Dr.SusanD.DayForest Resources &Environmental Conservation, Virginia Tech

• Understanding Compacted Soil Syndrome• When doyouact?

• Q&A• Strategiesand Tradeoffs• Technique: SPR• Implications forStormwater• MoreQ&A

BriefAgenda

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UnderstandingCompacted SoilSyndrome

AmericanElms

Worcester,Mass.1912

The fallbacksolution

Photo: P.EricWiseman

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Photo:RobertLlewellyn—Magnoliaacuminata (CucumberTree)TheRemarkableTrees ofVirginia

SustainableLandDevelopment?

Primefarmland soilwasgraded down3ft toredirectstormwater tobioinfiltration swale

At“peak”timeofyear(May)3yearslater, treedieback,thinturf,thincanopies,nutrientdeficiencies

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Compactedsoilsyndrome

Photo:RachelM.Layman

• At5-10cmmacroaggregates werereducedby44%

• Lost35%oftotalsoilorganiccarbon(0-10cm)• Lost47%ofmineral-boundcarbon• Subsurfacedrainagereducedfromabout3”anhourtolessthan½”anhour.

Photo: Jeannette E.Spaghetti (CC)

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Whataboutplants?

wetres=0.6MPa

moistres=1.75MPa

dryres=2.0MPa

SilverMapleatThreeLevelsofSoilStrength

Ascompaction increases

14-yearoldTilia tomentosa inasiltyclayloam(Day&Amateis2009)

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Sugarmapleroots

viewedthrough arhizotronwindow

Whendoyouact?—Determininganaction

threshold

Soil compactionMeasure bybulkdensityorpenetrationresistance

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Youcan’tinterpretsoilbulkdensitywithoutsoiltexture

Bulkdensity=1.4g•cm-3

sandyloam—noworriessiltyclayloam—watchout

Daddow andWarrington1983

%SAND

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Let’stakeaquestionbreak

StrategiesandTradeoffs

Blended andEngineered Soils

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Missing Soil?

DarrenDeStefanoUSTaxCourt

RecycledSoils

Photo:JayBanks

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Photo: Jeannette E.Spaghetti (CC)

Rehabilitating SoilinPlace

TECHNIQUE: SOILPROFILEREBUILDING

Remediates SoilCompaction

SetsSoil Formation Processes inGear

Increases Ksat, soil C, andtree growth

Specs areavailable online

Peer-reviewed science

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WillnotcorrectyoursoilpHproblems

Notforusearoundlargetrees

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Will reducecompaction,increase tree growth,improvepermeability, increase soilcarbonstores,andset long-term soilformationprocesses ontrack

Photo: Jeannette E.Spaghetti (CC)

Apply4inchesofcomposttograded subsoil

Soil ProfileRebuilding—Arehabilitationtechnique

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Backhoe to2ft,scoopupanddroptocreatecompostveins to2ft.

• Return topsoil asusual (4”min.)andtill 8”• Plant treesorother woody veg• Treatsurface toreduce erosion andmaintain

infiltration

8 cm

33cm

53 cm

18 cm

1.51

1.77

1.76

1.91(9mos)1.76(5yrs)

LowResistance(Topsoil)

HighResistance(Compactedsubsoil)

MediumResistance(Subsoil)

TypicalPractice

LoamSoil—SoilBulkDensityg/cm3

1.28

1.75

1.69

1.35 (9mos)1.49(5yrs)

ProfileRebuilding

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AdaptationofDaddow andWarrington,1983bySustainableSitesInitiative

Soil inTreeRootZone

Without Rehabyr 1=1.91gcm-3

WithRehabyr 1=1.35gcm-3

Without Rehabyr 5=1.76gcm-3

With Rehabyr 5=1.49gcm-3

CanopyAreaapproximatelydoubledafter7yearsincontrolled experiments

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CanopyAreainm2

Arlington County StreetMedians

DavidMitchell,2014

Implications forStormwater

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Site-level Effects SubsurfacePermeability 10-40cm(Ksat)

AgriculturalSoil—4to5cm/hrComparetoHSG B

Simplegrading,urbanlanddevelopment—1to2cm/hrComparetoHSG CorD

Rehabilitatedsoil—10to11cm/hrComparetoHSG AorB

Chenetal. ScienceoftheTotalEnvironment2014.

Urbanlanddevelopment

SoilManagement

Ksat

Atypicalsurfacetreatmentsforresearchpurposesresult inrestrictedflow

Bottleneckin“typicaldevelopedland”hasrapidwaterflow

Aggregate-associatedC

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Theurbanforestsystem

ComplexityoftheLandscape

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Chen, Y.,Day,S. D.,Shrestha, R.K.,Strahm, B.D.,Wiseman, P.E.,2014. Influenceofurban landdevelopment andsoil rehabilitation onsoil–atmospheregreenhouse gas fluxes.Geoderma 226,348-353.

Chen, Y.,Day,S. D.,Wick, A.F.,McGuire, K.J. ,2014. Influence ofurban landdevelopment andsubsequent soil rehabilitation onsoil aggregates, carbon, andhydraulic conductivity.Science of theTotal Environment.494–495, 329-336.

Chen, Y.,Day,S. D.,Wick, A.F., Strahm,B.D.,Wiseman, P.E.,Daniels, W.L.,2013.Changes in soil carbonpools andmicrobial biomass fromurban landdevelopment andsubsequent post-development soil rehabilitation. Soil BiologyandBiochemistry 66, 38-44.

Layman,R.M.,Day.S.D.,Mitchell, D.K.,Chen, Y.,Harris, J.R.,Daniels, W.L.2015.Below ground matters: Urbansoil rehabilitation increases treecanopyandspeeds establishment. Under review atUrban Forestry &Urban Greening

JournalArticlesforSPR

urbanforestry.frec.vt.edu

Wantmoreinfo?

• RecentArticleCityTrees(Sept/Oct)

• DownloadSpecificationsurbanforestry.frec.vt.edu/SRES

• Detailsunderproduction

THANKYOU

Collaborators:J. R.Harris,JosephDove,QingfuXiao,E.G.McPherson,N.Bassuk,BrianStrahm,AbbeyWick,W.LeeDaniels,P.EricWiseman,KevinMcGuire,Tess(Wynn)Thompson,andVincentVerweij

GraduateStudents:RachelLayman,YujuanChen,JuliaBartens,andDavidMitchell

SoilProfileRebuildingSpecificationsavailableaturbanforestry.frec.vt.edu/SRES

Partial supportprovidedbytheUSDA-ForestServiceNationalUrbanandCommunityForestryAdvisoryCouncil,TreeResearch&EducationFund,theInstituteforCriticalTechnologyandAppliedScienceatVirginia Tech,andtheUSDA’sMcIntire-Stennisprogram

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Photo: Peter Nijenhuis (CC)

Let’stalksomemoreaboutsoil!