S.А. Blagodatsky , Е.V. Blagodatskaya, E.G. Demyanova, V.N. Kudeyarov

September 30, 2005 September 30, 2005 ICDC7 Boulder, ColoradoICDC7 Boulder, Colorado

SUBSTRATE INDUCED GROWTH SUBSTRATE INDUCED GROWTH RESPONSE OF SOIL AND RESPONSE OF SOIL AND

RHIZOSPHERE MICROBIAL RHIZOSPHERE MICROBIAL COMMUNITIES UNDER ELEVATED COCOMMUNITIES UNDER ELEVATED CO22

S.А. BlagodatskyS.А. Blagodatsky, Е.V. Blagodatskaya, E.G. Demyanova,, Е.V. Blagodatskaya, E.G. Demyanova,V.N. KudeyarovV.N. Kudeyarov

Institute of Institute of Physicochemical and Biological Problems in Soil Science, Physicochemical and Biological Problems in Soil Science, Pushchino, RussiaPushchino, Russia

Т.-H. Аnderson, H.-J. WeigelТ.-H. Аnderson, H.-J. WeigelInstitute of Agroecology (FAL), Braunschweig, GermanyInstitute of Agroecology (FAL), Braunschweig, Germany


OverviewOverview IntroductionIntroduction Experimental design and methodsExperimental design and methods Soil Microbial Biomass measured by Soil Microbial Biomass measured by

SIR and dsDNASIR and dsDNA Kinetic characteristics of substrate-Kinetic characteristics of substrate-

induced growth response on glucoseinduced growth response on glucose Discussion and conclusionsDiscussion and conclusions


Motivation: why it is necessary Motivation: why it is necessary to study ?to study ?

Soil microbial biomass and activity are key Soil microbial biomass and activity are key factors controlling C-turnover in soil and factors controlling C-turnover in soil and respectively acceleration/mitigation of respectively acceleration/mitigation of the the resultant COresultant CO22 flux from soil to atmosphere flux from soil to atmosphere in response to proposed increase of C in response to proposed increase of C input to soil in elevated COinput to soil in elevated CO2 2 worldworld

Contradictory effect of elevated COContradictory effect of elevated CO22 on on soil microbial biomass: some studies show soil microbial biomass: some studies show positive response and some show no positive response and some show no response or even negativeresponse or even negative


What could help:What could help:

Accounting for other important factors: soil Accounting for other important factors: soil N level, type of growing plant, soil N level, type of growing plant, soil moisture content, dynamic nature of moisture content, dynamic nature of observed effects, spatial distinction observed effects, spatial distinction between bare soil and rhizospherebetween bare soil and rhizosphere

More careful consideration of functional More careful consideration of functional properties and structure of soil microbial properties and structure of soil microbial communitycommunity


to study the to study the effect of elevated effect of elevated concentration of atmospheric COconcentration of atmospheric CO22 on on biomass and specific growth rates of biomass and specific growth rates of microbial communities of soil and microbial communities of soil and rhizosphere rhizosphere

AimAim

HypothesesHypotheses Elevated COElevated CO22 effects growth effects growth

characteristics characteristics of soil and of soil and rhizosphere microbial communitiesrhizosphere microbial communities


Biosphere 2 Center, Arizona, Biosphere 2 Center, Arizona, USAUSA

ambient (400 ppm) and elevated (800 or 1200 ppm) ambient (400 ppm) and elevated (800 or 1200 ppm) atmospheric COatmospheric CO22 concentrations concentrations

Cottonwood tree (Cottonwood tree (Populus deltoides)Populus deltoides)


Free Air Carbon Dioxide Enrichment Free Air Carbon Dioxide Enrichment (FACE) Braunschweig, Germany(FACE) Braunschweig, Germany

ambient (350-370 ppm) and elevated (550 ppm) ambient (350-370 ppm) and elevated (550 ppm) atmospheric COatmospheric CO22 concentrations concentrations

N fertilization at rates 126 and 63 kg·haN fertilization at rates 126 and 63 kg·ha-1-1·year·year-1-1 Sampling: 2001Sampling: 2001 - sugar beet, - sugar beet,

2002 and 2005 – winter wheat2002 and 2005 – winter wheat


Measured characteristics:Measured characteristics: Soil microbial biomass – SIR method Soil microbial biomass – SIR method

(Anderson, Domsch, 1978)(Anderson, Domsch, 1978) Soil dsDNA – Soil dsDNA – direct extraction and direct extraction and

measurement of fluorescence after dyeing with measurement of fluorescence after dyeing with Picogreen (Marstorp, Witter, 1999; Blagodatskaya Picogreen (Marstorp, Witter, 1999; Blagodatskaya et al., 2004)et al., 2004)

Kinetic parameters of substrate-Kinetic parameters of substrate-induced growth response of soil induced growth response of soil microorganisms, total and active microorganisms, total and active microbial biomass by SIGR methodmicrobial biomass by SIGR method – – fitting the data on respiration rates measured fitting the data on respiration rates measured after soil amendment with glucose + NPK and/or after soil amendment with glucose + NPK and/or yeast extracts (Panikov et al., 1991; Blagodatsky yeast extracts (Panikov et al., 1991; Blagodatsky et al., 2000)et al., 2000)


Basic principle of SIGR methodBasic principle of SIGR method ((Panikov et al., 1991)Panikov et al., 1991)

COCO22 evolution rate after substrate evolution rate after substrate amendment (amendment ( ): ):

v(t) = A + B * exp(v(t) = A + B * exp(mm*t)*t) , where , where

A – A – initial rate of uncoupled (non-growth) initial rate of uncoupled (non-growth)

respirationrespiration

B – B – initial rate of coupled (growth) respirationinitial rate of coupled (growth) respiration

mm –– Maximal specific growth rateMaximal specific growth rate

t -t - timetime


Calculation of active and total Calculation of active and total microbial biomass based on SIGRmicrobial biomass based on SIGR

Active microbial biomass:Active microbial biomass:

X’ = B / X’ = B / mm

Total microbial biomass:Total microbial biomass:

X = X’ * rX = X’ * r00, where, where

rr0 0 – activity status calculated from – activity status calculated from the ratio between A and Bthe ratio between A and B


Soil microbial biomass in intensive Soil microbial biomass in intensive agroforestry biome of Biosphere 2 Centeragroforestry biome of Biosphere 2 Center

Microbial biomass (SIR)

0

100

200

300

400

500

600

700

800

900

400ppm 800ppm 1200ppm

CO2 concentration in atmosphere

g

C *

g s

oil-1 Rhizosphere

Bare soil

Please, seealso posterHI-396 byKudeyarov et al.


Rhizosphere Rhizosphere effect on effect on microbial microbial biomass (SIR) biomass (SIR) and dsDNA in and dsDNA in soil under sugar soil under sugar beets grown at beets grown at different different atmospheric COatmospheric CO22 concentrationsconcentrations

Microbial biomass

0

50

100

150

200

250

300

350

400

100% N 50% N

µg

C*g

-1

Ambient CO2,rhizosphere

Elevated CO2,rhizosphere

Ambient CO2,soil

Elevated CO2,soil

dsDNA in soil

0

10

20

30

40

50

60

70

80

90

100% N 50% N

µg

*g-1

Increase in microbial biomass (SIR) under Increase in microbial biomass (SIR) under elevated COelevated CO22 was only transient and was was only transient and was not supported by data on dsDNA contentnot supported by data on dsDNA content


Atmospheric COAtmospheric CO22 effect on SIGR: effect on SIGR:

soil under cottonwood tree soil under cottonwood tree (Populus (Populus deltoides)deltoides)

Respiration rate

0

50

100

150

0 5 10 15 20

hours

g

C-C

O2

*g-1

*h-1 400 ppm

800 ppm

1200 ppm

CO2 conc. max

400ppm 0.30 ± 0.01

800ppm 0.39 ± 0.04

1200ppm 0.47 ± 0.06



soil under sugar beetssoil under sugar beets

0

50

100

0 5 10 15 20 25

hoursµg С

-СО

2*h

-1*g

-1

Rhizosphere, 100% N

0

50

100

0 5 10 15 20 25

hours

µg С

-СО

2*h

-1*g

-1 Soil, 100% N

0

50

100

0 5 10 15 20 25

hoursµg С

-СО

2*h

-1*g

-1

Rhizosphere, 50% N

0

50

100

0 5 10 15 20 25

hoursµg

С-С

О2*h

-1*g

-1

Soil, 50% N

Elevated CO2 Ambient CO2



soil under winter wheatsoil under winter wheat - 2002 - 2002

0

50

100

0 5 10 15 20 25 30

hoursµg С

-СО

2*h

-1*g

-1

Rhizosphere, 50% N

0

50

100

0 5 10 15 20 25 30

hoursµg

С-С

О2*h

-1*g

-1 Soil, 100% N

0

50

100

0 5 10 15 20 25 30

hoursµg

С-С

О2*h

-1*g

-1

Rhizosphere, 100% N

0

50

100

0 5 10 15 20 25 30

hoursµg С

-СО

2*h

-1*g

-1 Soil, 50% N




soil under winter wheat - 2005soil under winter wheat - 2005


Rhizosphere, 50% N

0

25

50

75

100

0 5 10 15 20 25 30 35

hours

C-C

O2,

g

g-1

h-1

Soil, 100% N

0

25

50

75

100

0 5 10 15 20 25 30 35

hoursC-C

O2, g

g-1

h-1

Soil, 50% N

0

25

50

75

100

0 5 10 15 20 25 30 35

hoursC-C

O2,

g

g-1

h-1

Rhizosphere, 100% N

0

25

50

75

100

0 5 10 15 20 25 30 35

hoursC-C

O2,

g

g-1

h-1


3-way ANOVA,3-way ANOVA,Soil under sugar beets,Soil under sugar beets,Contribution of Contribution of independent factors: independent factors: elevated COelevated CO22, rate of , rate of N-N-

fertilizersfertilizers and distance and distance from root surface on total from root surface on total variation of maximal variation of maximal specific growth rate of soil specific growth rate of soil microorganisms, total and microorganisms, total and active microbial biomassactive microbial biomass

Specific growth rate Rest4%

CO2*N*Rhi 4%

N16%

12%Rhi

6%

CO2*Rhi

CO2,

57%

Total microbial biomassRest11%CO2*N*Rhi

3%

N10%

48%Rhi

CO2,

26%

Growing microbial biomass

CO2,

24%

11%N*Rhi

22%

CO2*Rhi8%Rhi

N13%

CO2*N*Rhi 9%

Rest12%


3-way ANOVA3-way ANOVA , ,Soil under winter wheat,Soil under winter wheat,

Contribution of Contribution of independent factors: independent factors: elevated COelevated CO22, rate of , rate of N-N-

fertilizersfertilizers and distance and distance from root surface on total from root surface on total variation of maximal variation of maximal specific growth rate of specific growth rate of soil microorganisms, soil microorganisms, total and active microbial total and active microbial biomassbiomass

Specific growth rate,

CO2,

36%

CO2*N

0% 3%Rhi*N

N26%

CO2*N*Rhi

18%

Rest17%

Total microbial biomass

CO2, 4%

Rhi*N28%

Rhi3,9%

N2%CO2*N*Rhi

5,2%

Rest56%

Growing microbialbiomass Rhi

10%

CO2*N31%

N5%

CO2*Rhi2%

Rest26%

CO2*Rhi*N24%


Effect of COEffect of CO22 enrichment on enrichment on

microbial turnover in soilmicrobial turnover in soil

Exudation Humification

CO2

Respiration

Shift to r-strategy

Human activities

Photosynthesis


Critical question for warming Critical question for warming potential acceleration / mitigationpotential acceleration / mitigation

How will change the ratio How will change the ratio respiration/humification after respiration/humification after changing of atmospheric COchanging of atmospheric CO22 concentration ? concentration ?

Further studies combining kinetic Further studies combining kinetic approach with C and N labeling are approach with C and N labeling are

neededneeded


ConclusionsConclusions

Elevated COElevated CO22 affects the functional affects the functional structure of soil microbial communitystructure of soil microbial community

The size of active/total soil microbial The size of active/total soil microbial biomass depends on elevated CObiomass depends on elevated CO22 in in a lesser extenta lesser extent

Specific growth rate (µSpecific growth rate (µmm) – the most ) – the most sensitive parameter reflecting sensitive parameter reflecting changes in ecological strategy of changes in ecological strategy of microbial communities microbial communities


Thank you for attention!Thank you for attention!

ACKNOWLEDGEMENTSACKNOWLEDGEMENTS •Research was supported by BMVEL, DAAD and Research was supported by BMVEL, DAAD and Russian Foundation for Basic Research Russian Foundation for Basic Research •Sponsorship of ICDC7 supporting agencies and Sponsorship of ICDC7 supporting agencies and decision of Scientific Committee enabled participation decision of Scientific Committee enabled participation of first author in conferenceof first author in conference•Special thanks to Karl Bil’ - Biosphere 2 CenterSpecial thanks to Karl Bil’ - Biosphere 2 Center

S.А. Blagodatsky , Е.V. Blagodatskaya, E.G. Demyanova, V.N. Kudeyarov

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