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An exploration into the chemicalmakeup of soil and its influence

on microbial soil profiles. Howdoes this affect the validity of

using decomposition microbes

found in soil, as forensic tools?

Catherine L. Aindow : 200805506 Project Supervisor: Dr L.

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Aims of this presentation

Pesticide application

Carbon: Nitrogen cycle

Vegetation type and density

Effects upon microbial soil populations

Can microbial soil profiles be linked tosites of cadaver decomposition?

Could these variables renderhypothesis untrue?

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Soil Composition andVariables Soil is a complex matrix of inorganic

and organic compounds.

Supports the growth of a variety of

microorganisms. Variables that affect chemical and

microbial composition within soil.

Influences the carbon to nitrogen bio-cycle within soil.

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Carbon : Nitrogen CycleClimate

Temperature, SoilFertility, WaterContent. Etc.

Plant growth

Labile litter androot fluids low

C:N ratio

Recalcitrant litterhigh C:N ratio

Carbonallocation to

plant roots

Bacteria(sacrophytic)

Fungi(sacrophytic)

EM,ECMfungi

(symbiotic)

AM fungi

(symbiotic)

Bacteria

(symbiotic)

N, P (mineral)

N, P (organic)

N (air)

high low

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Cadaver Decomposition

Cadaverdecomposition altersnatural bio-cycle within

soil. Release of lipids,

proteins and aminoacids into soil.

Influences the growthof specific microbes.

Microbial profiling may

distinguish sites of

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Effects of Pesticide Applicationupon Soil Communities

Study conducted to showthe effects of commonpesticide Carbendazim

upon chemical makeup ofsoil.

A range of organisms were

examined includingnematode populations.

Employed use of

microcosmic conditions.

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Methodology (Microcosm)

Addition of artificalrainwater 12 hour light-dark

cycle maintined.

6 samples (30 kgeach)

Polyethylene pipes Nylon mesh for

leachate collection. Addition of 3

earthworms persample

Sown with approx.

10 wheat seeds Soil-pesticide

mixtures thoroughlymixed beforepacked.

Did not account for daylightsaving

Method does not correctlyimitate the way in whichpesticide would settle upon

the soil.

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Methodology (The Process)

Dose sampleslabelled T0 up to T5

T0 Ionized water

T10.76

T22.28

T3 6.84

T4 20.52

T5 61.56 (concs: a.i. kg-1 soil

dry mass)

400 ml sprayed

Nitrogen andammonium concsmeasured beforetreatment and after7,14,28 and 56 days.

Extraction

Colorimetric methodused for quantification(650 nm).

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Nitrate Concentrations afterTreatment

Dose levels T4 & T5 increase nitrate

concentrations significantly in comparison toother dose levels.

Soil chemistry able to recover after 56 days.

Recovery may be due to shoot growth.

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Vegetationgrowth and

NitrateConcentrations

Shoot growth (grams) after treatment with knownconcentrations of Carbendazim

Nitrate concentration after treatment with knownconcentrations of Carbendazim

Shoot growth increasesdramatically after 56days of treatment with

all concentrations ofCarbendazim. Increase in shoot

growth is also seen incontrol.

Therefore pesticide

application does notseem to hindervegetation growth.

Correlation betweenvegetation growth andnitrate concentrations.

State of homeostasisachieved.

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Conclusion from experiment

Pesticide application does alter chemical

makeup of soil. Increases nitrate concentrations. Potentially would influence microbial

populations that thrive in low C:N

environments. Would render influence of cadaver

decomposition upon soil profilesirrelevant.

Vegetation growth may combat adverseeffects.

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The effects of vegetation type anddensity upon microbial soil

populations Study took place within a forest in Sweden

(Betsele).

3 transects of land: 90m long & between 25m and

70m apart. Dwarf shrub (DS), short herb (SH) and tall herb

(TH) vegetation types were analysed.

DS

E.g. species: Vacciniummyrtillus

Open and of low productivity.

SH

E.g. species: Oxalicacetosella

Characterized by severalshort herbs

TH

E.g. species: Actae spicata

Dominated by pineas abies

forest & has high soil pH andnitrogen.

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Methodology

Aimed to identifychemical andmicrobiologicaldifferences betweenbiomes.

Soil samples taken in

triplicate on 18th

August2004

Samples were taken viaa 0.15m auger and thenincorporated into onebulk sample for eachtransect.

Samples were siftedthrough sieve

Chemical analysis

PLFA analysis

Sample storage

NOTE After sifting samples were weighed out into

appropriate amounts no value was stated. Extraction method Bligh & Dyer method PLFA analysis silica gel columns, then eluted

in sequence with chloroform acetone andmethanol.

Specific method of chemical testing was also

not stated.

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Results(Chemistry)

Soil chemistry observed in Betsele sites

Site ForestType

Treat-ment

pH C to NRatio

NH4-N(g g-1

o.m.)

NO3-N(g g-1

o.m.)

Betsele

DS - 4.0 38.1 4.6 0.9

SH - 4.6 22.9 5.2 0.7

TH - 5.3 14.9 15.9 3.4

P-value

- -

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PLFA Analysis No significant

difference withintotal PLFA massbetween biomes

Fungal bacteriamass decreased asvegetation thickened

Total amount ofbacteria increasesas vegetationthickened.

Due to an increasein gram negativebacterial levels.

Gram positivebacterial levels did

not alter significantly. Fungi to bacteria

ratio decreased asvegetationthickened.

Distinctive microbialprofiling betweendifferent biomes.

Combination of highpH and highnitrogen levelsfavours the growthof gram negativebacteria.

Deters growth offungi.

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Effects of nitrogen loading uponcarbon: nitrogen ratio Site in Sweden (Norrliden)

All sites DS

Total of 15 plots investigated(4 concs - 3 replicates foreach).

4 concentrations of nitrogen(in form of NH4NO4)

1 control (given aconcentration of 3kg N ha-1year-1)

N3 was discontinued at anearlier date to see how soilchemistry would recoverfrom loading

N0 control

N1 34 kg N ha-1 year-1 N2 68 kg N ha-1 year-1

N3 108 kg N ha-1 year-1

N1 & N2 treated from 1971-2004

N2 treated from 1971 1990 Samples were taken on 25th

August 2004

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NORRLIDEN RESULTS(CHEMISTRY)Site Forest

TypeTreatment pH C to N

ratioNH4-N(g g-1o.m.)

NO3-N(g g-1o.m.)

Norrliden

DS N0 4.1 37.5 0.5 0.7

DS N1 4.1 31.1 39.9 1.5

DS N2 4.2 27.7 88.4 7.3

DS N3 4.1 27.2 3.3 0.6

P-Value - -

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Nitrogen loadingPLFA results

(Norrliden site) Total PLFA contentdecreases with highlevels of nitrogenloading.

Fungal biomass also

decreases with theaddition of nitrogenhowever appears torecover aftertreatmentdiscontinuation.

No significant changeis seen within thebacterial populations,though there is aslight increase in

gram positivebiomarkers asnitrogen levelsincrease.

Fungi to bacteria

ratio decreases asfungi biomarkerlevels drop and grampositive bacteriabiomarkers increase(slightly).

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Discussion

Many similarities betweenmicrobial communities that havesame biome.

Gram positive markers able towithstand nitrogen loading and

therefore would withstandchanges made by pesticides.

Gram positive bacteriabiomarker levels did not differacross different biomes

Further study conductedshowed no change in gram

positive PLFA biomarkersacross a tree-girdlingexperiment. (Not affected bywater content).

Since gram positive bacteriado not change across biomes

and across different chemicalmakeups, could be a goodcandidate for a decompositionbiomarker.

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How would it work?

Decomposition ofcadaver wouldrelease intestinal

bacteria. Would also alter

chemical makeupof soil.

Which wouldinfluence changeswithin soil profiles

Increase in grampositive bacteriawithin soil samples

could only then beattributed tocadaverassociation

May also indicatewhere body hasbeen moved from.

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Problems

No concreteground for provingthis hypothesis.

More work wouldneed to be carriedout.

Too many

variables andinfluences.

No soil profile is

the same.

Just too much toconsider to rely on

decompositionmicrobes as aforensic tools.

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Any Questions?