A presentation by Dr. Jan lagerlöf

1. 5/27/2010
Trophic interactions among soil organisms in contrasting
land‐use systems in Kenya, studied with stable‐isotope Project facts
technique
• Research grants from Formas (Swedish Research Council for
Environment, Agricultural Sciences and Spatial Planning) in co‐operation
with Sida
Jan Lagerlöf1, Mary Gikungu2, Crispus Maribie3, Jamleck Muturi
John4, and Peter Okoth5
• Special call for Swedish scientists’ work at CGIAR Institutes: Five months
1 Swedish University of Agricultural Sciences (SLU), Dept. of work during two consecutive years + technical assistance, travelling,
work during two consecutive years + technical assistance travelling
Ecology, P.O.Box 7044, SE‐750 07 Uppsala, Sweden some equipment, etc
2National Museum of Kenya, P.O.Box 30197‐00100, Nairobi, Kenya • Two periods: 2008‐2009 + 2010‐2011
3 School of Biological Sciences, University of Nairobi, P.O.Box
30197‐00100, Nairobi, Kenya Encurrage
4 Dept. of Zoological Sciences, Kenyatta University, P.O.box 43844‐ Swedish
scientists to
00100, Nairobi, Kenya work with
5 TSBF‐CIAT, c/o ICRAF, Gigiri, P.O.Box 30677‐00100, Nairobi tropical
agriculture and
environment in
CGIAR
1 institutions 2
How to study food webs and feeding relationships
1. Gut content analyses:
– Microscope observations
– Immunological methods, ELISA
– Biochemical methods, e.g. DNA analysis
Collembola, Folsomia fimetaria gut content
Photo J. Lagerlöf
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FAO web page
How to study food webs and feeding relationships How to study food webs and feeding relationships
2. Observation of feeding behaviour
3. Attractiveness of different food sources 5. Trace food sources to the next trophic level by
4. Growth and reproduction on different food sources
– Radioactive isotopes (e.g. 14C)
– Stable isotopes (e.g. 13C, 15N)
Fungivorous nematodes
(Aphelenchus avenae) feeding on
Amoeba (Testacea) feeding
hyphae of the plant parasitic fungus on nematod
Verticillium dahliae
Photo SLU Photo J. Lagerlöf 5 6
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2. 5/27/2010
How to study food webs and feeding relationships
Types of studies that can be done with stable isotopes
Stable isotopes – can be analysed with mass spectrometer
• Ratios of natural abundances of stable isotopes in different parts of
• Isotope ratios (e.g. 13C/12C=R) are compared relative to a standard. The a food web – for studies of trophic levels
deviation (δ) of the ratio relative to the standard is expressed per
thousand (“per mil” or ‰)
Study 1 in BGBD Kenya: Natural isotope ratios of soil organisms in
• δX = [(R sample/R standard)‐1)]*1000 soil with different disturbance regimes
• X is either N or C • Enrichment of food items and follow the enrichment though the
food web – for studies of feeding relations:
• Organism tissues are more enriched in both the heavy isotopes of plant material → grazers → predators → top predators
nitrogen 15N and carbon 13C than their food source
Study 2 in BGBD Kenya: Enrichment of the growing crop with 13C
• → Increase of δN with approximately 3.4‰ per trophic level in field experiment ‐ following of 13C in the food web.
• → Increase of δC with approximately 1‰ per trophic level
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Study 1 in BGBD Kenya: Natural isotope ratios in of soil organisms in soil
Study 1 in BGBD Kenya: Natural isotope ratios in of soil
with different disturbance regimes
organisms in soil with different disturbance regimes
Procedure:
• Sampling microarthopods in the field Oct ‐ Nov 2008
• Extraction of microarthropods
• Sorting into taxonomic groups (family or genera for
collembola and mites, higher l l f
ll b l d i hi h level for others)
h )
• Drying freezing
Natural Forest Napier (fodder grass)
• Weighing into tin capsuls, 0.02‐0.2 mg dw per sample
• Hypothesis: Disturbed systems have shorter food chains and each species group • Analysis of δ13C and δ 15N signatures (‰) by mass
will have broader feeding niche than in less disturbed systems.
• Activity: Sampling of microarthropods in Natural Forest and Napier (fodder
spectrometry, in Sweden Lund University
grass), BGBD sites in Embu. Sorting into lower taxa. Determination of 13C/12C and
15N/14N ratios.
Start September – November 2008
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Photo J. Lagerlöf
Study 2 in BGBD Kenya: Enrichment of the growing crop with 13C in field
experiment ‐ following of 13C in the food web Study 2: Food webs in agricultural fields studied with 13C
labelling (control without labelling) four replicates
Start April 2009
Field experiment: Organic matter Field experiment,
• Hypothesis: KARI Research Station Embu, 4
‐ Certain soil animals and other organisms are linked to the growing crop replicates in blocks
(grazer food chain) as their primary food source, directly or indirectly.
‐ Others are linked to dead organic matter (decomposer food chain).
‐ This will vary with degree of organic matter amendment and Studied treatments: Maize Manure, 4 tons/ha/y
disturbance.
disturbance
Bare soil Manure, 4 tons/ha/y
• Questions asked: Maize NPK, 120 kg/y
‐ To what extent do taxonomic and functional groups of soil animals Bare soil NPK, 120 kg/y
derive their nourishment from the growing crop, directly of indirectly?
‐ To what extent do they use the dead organic matter as their basic food
source? Labelling: of growing maize crop (manure and
‐ How will this vary with organic matter amendment? NPK fertilized) with 13CO2, 27-28
April 2009
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3. 5/27/2010
13CO2 labelling of maize Embu April 2009
450,0
340,0
C 2 c n e tra ninc a b r p m
430,0
hme p
320,0
300,0
410,0
280,0
260,0
390,0
240,0
O o c n tio
220,0
370,0
200,0
180,0
350,0
160,0
140,0 330,0
-5 5 15 25 35 45 55
0 5 10 15 20 25 30 35 40
Time minutes
CO2 upptake in maize with CO2 emission from bare soil
NPK fertilization with NPK fertilization
300,0 570,0
Labelling of maize
250,0
with 13CO2 (above) 520,0
200,0
470,0
150,0
Monitoring of CO2 420,0
100,0
concentration in the
50,0 370,0
atmosphere of the
0,0
perpex box (left) 0 5 10 15 20 25 30 35
320,0
-50,0 0 5 10 15 20 25 30 35 40
CO2 upptake in maize with CO2 emission from bare soil
13 manure fertilzation with manure fertilization 14
Preliminary results study 1
Study 2:
Sampling: Soil, plants, roots and soil organisms (mesofauna, and Natural abundanceδ13C and δ15N signatures (‰) of Soil Arthropods
microorganisms) 2, 4 and 6 weeks after labelling from Natural Forest Embu, Kenya (each symbol representing one
Analyses: isotope ratios in animals, plantmaterial and soil - Mass observation)
spectrometer 35
In microorganisms – fatty acid analysis (PLFA) followed by mass 30 Coll
spectrometer analysis Oribat
25
Gamasina
20
δ15N‰
Uropodina
15 Trombid
10 Pseudoscorp
Chilopoda
5
Diplopod
0 Symphyla
‐30 ‐25 ‐20 ‐15 ‐10 ‐5 0 Ant
δ13C‰
15 16
Natural abundances of δ13C and δ15N signatures (‰) of Oribatid mite families
10
9 Brachyphy
δ 8 Carabodidae
Natural 1
Natural abundance δ13C and δ15N signatures (‰) 5
7 Damfielidae
forest 6 Eupthacaridae
of Soil Arthropods from Napier Field, Embu, Kenya N
5
‰ Galumnaeidae
(each symbol representing one measurement )
4 Hermannidae
3 Northridiidae
60 2 Oppiidae
1 Otocephidae
50 0
Ptacaridae
‐30 ‐25 ‐20 ‐15 ‐10 ‐5 0
δ 40
Coll δ13C‰
1
Oribat
5 30
60
Gamasina
N
‰ 20 Chilopoda
Napier δ 50
Ant 1
10 Trombid
5 40
Hermannidae
N
0 ‰ 30
Oppiidae
‐25 ‐20 ‐15 ‐10 ‐5 0 Otocepheidae
20
δ13C‰
10
0
‐25 ‐20 ‐15 ‐10 ‐5 0
17 δ13C‰ 18
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4. 5/27/2010
Natural abundances of δ13C and δ15N signatures (‰) of
Natural abundances of δ13C and δ15N signatures (‰) of
predatory mite Gamasina families
Collembola families
30
25 Brachystom
δ 20
Entom 10
Natural 1 Hypogastr 9
forest 5 15 8 Gamasina spp,
Isotomid
N
‰ Neanurid Natural 7 Laelapidae
10 δ
Odontellid forest 1
6 Liacaridae
5 Macrochelidae
5 Onychiur 5
Sminth N 4 Oligogamasidae
0 ‰ 3 Parasitidae
‐30
30 ‐25
25 ‐20
20 ‐15
15 ‐10
10 ‐5
5 0 2 Polyaspidae
δ13C‰ 1
Rhodacaridae
18 0
δ 16 ‐30 ‐25 ‐20 ‐15 ‐10 ‐5 0
Napier 1 14
δ13C‰
5
12
N
‰ 10 Poduridae
8
6
4
2
0
‐15 ‐14.8 ‐14.6 ‐14.4 ‐14.2 ‐14
δ13C‰
19 20
Preliminary conclusions:
Discussion and comments
-The technique functions
-There are differences in feeding among taxonomic groups
(family, genera) of mite and collembola – shown as different natural
• We are grateful for comments and
abundance δ13C and δ15N signatures suggestions.
Continuation of the work: • There is place for people to join in and study
-Continuation of analysis of δ13C and δ15N signatures i
C ti ti f l i f d i t in other organisms or questions in these
other organisms or questions in these
soil, microorganisms and microarthropods in study 1 and 2
ongoing or planned experiment.
- Collecton of more data on natural δ13C and δ15N for
microarthropods and other soil organism groups; • Suggestions for follow‐up studies and new
earthworms, enchytraieds, nematodes
applications for funding.
-Extended labelling experiment with sampling of larger number of
organism groups
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Thank you for your attention
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Photo: H. Friberg J. Lagerlöf & N.N.
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