Dynamics in the Microbial Dynamics in the Microbial Transformation of Organic C in SoilTransformation of Organic C in Soil
Jinshui WuJinshui Wu
Institute of Subtropical Agriculture,
the Chinese Academy of Sciences
Outlines
Concepts of soil microbial biomass and soil organic C transformations
Methodology for quantifying soil microbial biomass
Case studies on dynamics in the microbial transformations of organic C in soil
Outlines
Concepts of soil microbial biomass and soil organic C transformations
Methodology for quantifying soil microbial biomass
Case studies on dynamics in the microbial transformations of organic C in soil
土壤生物Microbial
CommunityOC
(N/P/S)CO2/CH4/NxO…HM/Minerals
Biogeochemical functions of the soil microbial community
土壤生物Microbial
CommunityOC
(N/P/S)CO2/CH4/NxO…HM/Minerals
Biogeochemical functions of the soil microbial community
Assumption: The soil microbial community mediate the transformation of all organic materials exiting in soil.
土壤生物Microbial
CommunityOC
(N/P/S)CO2/CH4/NxO…HM/Minerals
Biogeochemical functions of the soil microbial community
Assumption: The soil microbial community mediate the transformation of all organic materials exiting in soil.
Key issue: In which community levels can the fluxes (rates) of C and nutrients be quantified (single cells, species, functional groups, or the whole) ?
Soil microbial community: Population
Bacteria (No g-1)
108 - 109
Fungalhyphae (m g-1)
10–1000
Bacterial species: > 104 g-1 soil (Data from Prof. P. C. Brookes)
The concept of soil microbial biomass(Jenkinson and Brookes)
The sum of the masses of all the soil micro-organisms (as a single pool) Providing a definitive entity for the bio-chemical assessments of the soil microbial community (e.g. the pool size), and the fluxes of C and nutrients through the biomass pool.
Compositions Arable Grasslandkg ha-1
Dry matter 1100-3300 1600-7500C 500-1400 750-3500N 80-230 125-500
Soil microbial biomass (per ha)
50-350 sheep
=
Soil microbial community: Biomass
土壤生物Microbial
CommunityOC/
N/P/SCO2/CH4/NxO…
HM/Minerals
Quantity of the microbial biomass
Quantifying the dynamics parameters (the flux rates of OC/N/P/S, and the ratios of the products)
Defining the functional groups involved
Biogeochemical functions of the soil microbial community
Outlines
Concepts of soil microbial biomass and soil organic C transformations
Methodology for quantifying soil microbial biomass
Case studies on dynamics in the microbial transformations of organic C in soil
nucleus
extraction
chemicalanalysis
Microbial C, N, P, S
cytoplasm
lipidcellmembrane
Soil
CHCl dissolves cell membranes3
● Lyses > 95% cells.
● Does not alter the solubility and mineralizing activity of organic materials.
The fumigation-extraction method
Powlson & Jenkinson (1976), SBB
TOC
Reliable chemistry procedures Rapid and high accuracy analysis Suitable for large numbers of samples
The fumigation-extraction method
Automatic instrument analyses for the extracted biomass C, N, P, and S
(Wu et al., 1990, SBB; Shen et al, 1985, SBB; Wu et al., 1994, SBB; Wu et al., 2000, BFS)
Flow injection analyzer
The fumigation-extraction method
SBB selected papers of the Citation
Classics
Vance, Brookes and Jenkinson (1987). An extraction method for measuring soil microbial biomass C. Soil Biology & Biochemistry 19, 697-702.
Wu, J., R.G. Joergensen, B. Pommerening, R. Chaussod and P.C. Brookes (1990). Measurement of soil microbial biomass by fumigation-extraction - an automated procedure. Soil Biology and Biochemistry 22, 1167-1169.
Organic C
(14C)Biomass 14C
Metabolic-14C (humic substances)
14CO2
Turnover
Turnover
Combined the automated analysis procedures with 14C labelling technique
14C-labeling
Outlines
Concepts of soil microbial biomass and soil organic C transformations
Methodology for quantifying soil microbial biomass
Case studies on dynamics in the microbial transformations of organic C in soil
Yt=Y0 e-kt
ln(Yt) =ln(Y0) - kt
Case 1: The turnover rates of soil microbial biomass C and P
Assumption: The turnover of 14C-labelled biomass C follows the first-order kinetics
k: The turnover rate
1/k: The turnover time (days)
Changes in soil microbial biomass C labelled with 14C (by the amendment with 14C-lablled glucose and incubation at 25 oC)
(Wu et al., 2012, JSFA)
(μ
g g-1
)
Incubation time ( d )
Paddy soil Upland soil
Turnover rate of microbial biomass C in subtropical upland and paddy soils (China)
培养条件下 20 ~ 100 d 土壤
表观速率常数
(k, 10-3 d-1)
相关系数
(r)
周转时间
(d)
田间条件下
周转时间
(yr)
旱地 2.7 0.1 -0.92 370 13 2.2
稻田 8.1 0.9 -0.98 123 14 0.7
Site 1
Upland
Paddy
Turnover rate Turnover time
Field conditions
Wu et al., 2012, JSFA
At 25℃
The turnover time of biomass C affected by soil clay content and management
% Clay Turnover time at 25℃ Field conditions
39 383 4.022 201 2.115 126 1.3
Management Turnover time
at 25℃ Field conditionsGrassland 212 2.2
FYM 193 2.0Nil 178 1.9
Fallow 175 1.8
(22% clay)
(NPK)
Organic C Biomass C
Metabolites (humic substances)
CO2
Turnover
Turnover
Case 2: Quantifying the ratio of CO2 from biomass C and non-biomass organic C
Soil+14C-glucose
Incubation (20 d at 25 )℃
Ad-Rw (5 cycles; incubated for 7 d at 25
)℃
DeterminationsCO2\Bc\DOC
(total\14C-labelled)
0
20
40
60
80
0 7 14 21 28 35
0
500
1000
1500
0 7 14 21 28 35
CO2 evolved from a soil following the amendment of 14C-lablled glucose and 5 drying-rewetting cycles
(Wu et al., 2005, SBB)
Total 14C-labelled
(μg
C g
-1 s
oil)
Incubation time (days)
Proportions of CO2 evolved in a soil following 5 drying-rewetting Cycles (Wu et al., 2005, SBB)
0
20
40
60
80
100
1 2 3 4 5
来自微生物量来自微生物代谢
%
Biomass C (heavily 14C labeled) Organic C (lightly 14C labeled)
Case 3: The mechanisms of “priming effect”
Priming effects: Responses of the mineralization of soil organic C following the inputs of fresh organic materials.
Responses of CO2 evolution and biomass C to glucose (14C-lablled) addition
Mechanism I: Enhanced turnover of the biomass C which results in the ‘replacement’ of native biomass C (unlablled) by the newly formed biomass C (labelled) (Wu et al., 1993, SBB)
PE
Responses of CO2 evolution and biomass C to ryegrass (14C-lablled) addition
Mechanism II: Increased mineralization of the native soil organic C (unlabelled) by the activities of the prolonged increases of the microbial biomass (Wu et al., 1993, SBB)
Case 4: Quantifying the assimilation of atmospheric CO2 by autotrophic micro-
organisms in soils
Soil incubated for 80 d in the growth chamber with 14C-la
beled CO2
Soils (x 8)
(14C-CO2)
Incubate in dark(foam cover, 4 reps)
Incubate in light(no cover, 4 reps)
12 hr light cycle, incubate for 80 days
14C-MBC14C-OC DNARubisCo
cbbL (1A,1C); cbbL (1D)qPCR, cloning and sequencing
Functional micro-organisms
mg
C k
g -1 so
il
% o
f t
otal
SO
C
Microbial assimilation of atmospheric CO2 (14C-labelled) in subtropical soils
(Yuan et al., 2012, AEM; Ge et al., 2012, SBB)
mg
C k
g -1 so
il
% o
f t
otal
SO
C
Annual C assimilation: 100-500 kg C!
Microbial assimilation of atmospheric CO2 (14C-labelled) in subtropical soils
(Yuan et al., 2012, AEM; Ge et al., 2012, SBB)
(nm
ol C
O2 g
-1 m
in -
1)
RubisCO activity in the soils incubated for 80 d(Yuan et al., 2012, AEM; Ge et al., 2012, SBB)
Light
Dark
nd nd
*
*
*
**
*
*
0.0
0.5
1.0
1.5
P1 P2 P3 P4 U1 U2 U3
(×10
8 cop
ies g
-1 )
0.0
0.5
1.0
1.5
2.0
2.5
P1 P2 P3 P4 U1 U2 U3
(×10
6 cop
ies g
-1 )
Bacterial cbbL genes blue-green cbbL genes
0.0
0.5
1.0
1.5
2.0
P1 P2 P3 P4 U1 U2 U3
(×10
6 cop
ies g
-1)
Non-green cbbL genes
Abundance of cbbL genes encoding bacteria, blue-green and non-green algae in the soils(Yuan et al., 2012, AEM)
Light Dark
** *
*
* * *
**
* *
* * *
*
**
*
*
* *nd nd
0.0
0.5
1.0
1.5
2.0
2.5
1 20
2
4
6
8
10
1 2
Thiobacillus denitrificans
Ralstonia eutropha
Bradyrhizobium japonicum Azospirillum lipoferum
Rhodobacter azotoformans Aminobacter sp.
Rhodopseudomonas palustris
U1-lightP1-dark
(×10
7 cop
ies g
-1)
P1-light U1-dark
Rhodopseudomonas palustris
Bradyrhizobium japonicum Thiobacillus denitrificans
Aminobacter sp.Mycobacterium sp.
Bacterial cbbL taxa abundance in soils P1 and U1 (Yuan et al., 2012, AEM)
0
1
2
3
4
1 2 3 4
(×10
6 cop
ies g
-1)
Algal cbbL taxa abundance in soils P1 and U1(Yuan et al., 2012, AEM)
Blue-green algae
Non-green algae
P1-light P1-dark U1-light U1-dark
Oscillatoria sp.
Anabaena sp.
Fischerella thermalis
Tribonema viride
Porphyridium aerugineum
Sellaphora auldreekie
Thank for Your Attention !
Top Related