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Functions and Services of the
Soil Food Web:
Nematodes as Biological Indicators
Howard Ferris
Department of Nematology
University of California, Davis
[email protected]
February, 2008
Soil Food Web Functions - metabolic and behavioral activities
of organisms that impact the biotic or abiotic components of the ecosystem
Feeding:
Behavior:
Ingestion, assimilation, defecation and excretion
Movement, activity, migration
Functions may be classified, subjectively, as Services, Disservices
(or Neutral)
Disservices:
Damage plants of agricultural or ornamental significance
Injure humans and vertebrate animals
Services:
Sequester and redistribute minerals
Individual species
Mineralize organic molecules
services
Accelerate turnover
Regulate and suppress pests
Alter substrate to provide access to other organisms
Redistribute organisms in space
Reduce soil erosion
Aggregate
Increase agricultural production
food web services
Positive and Negative Feedback in Food Web Services
bacteria and bacterivore nematodes
0 nematodes
Bacterial Cells
100
Positive feedback
Overgrazing
80
with five nematodes
60
40
20
0
0
5
10
20
40
Nematode Abundance
Fu et al. 2005
with twenty nematodes
80
160
Linkages and Connectance among Functional Guilds
Nematodes at each trophic level
Soil Food Web Structure is strongly influenced
by nature and frequency of Carbon and Energy Input
•Carbon is respired by all
organisms in the web
•The amounts of Carbon and
Energy available limit the size
and activity of the web
perennial intermediate
wheatgrass
annual wheat
Soil Depth (m)
0
Soil Food Webs
1
Bottom up effects:
Resource availability
2
Photograph courtesy of
Dr. Jerry Glover
The Land Institute, Kansas
Soil Food Web: Functions and Services in relation to Structure
Effects of:
Mineralization
B
F
B
F
P
P
O
O
Pr
Regulation
Pr
tillage
tertilizers
pesticides
punctuated cropping
type and amount of organic input
Soil Food Webs – environmental factors affecting Structure
Environmental
heterogeneity
Separate
metacommunities?
Zones and
Gradients:
texture
structure
temperature
water
O2
CO2
NO3
NH4
minerals
Soil Food Webs – environmental effects on Structure
Standardized Counts
Nematode Sensitivity to Mineral Fertilizer
Ammonium sulfate
200
Nematode guild
150
c-p 1
c-p 2
c-p 3
c-p 4
X c-p 5
100 X
50
X X
0
0 0.02 0.05 0.1
X X
0.5
1
Concentration (mM-N)
Tenuta and Ferris, 2004
Soil Nematodes as Bioindicators: Functional Diversity
A milestone contribution:
When feeding on their prey, bacterial- and fungalfeeding nematodes excrete N that is in excess of their
structural and metabolic needs.
Ingham
Ingham, R.E., J.A. Trofymow, E.R. Ingham, and D.C. Coleman. 1985.
Interactions of bacteria, fungi, and their nematode grazers: Effects on
nutrient cycling and plant growth. Ecological Monographs 55:119-140.
Another milestone - calibration of ecosystem condition:
Maturity Index = MI 
Colonizer-persister Series
v p
i 1, f
opportunism
enrichment
1
i
i
structure
stability
2
3
4
5
Weighting:
• should the separations between the classes be equal?
Bongers
Issues of proportions:
• If the proportion of opportunists increases, the
proportion
of sensitive
speciesindex:
decreases.
Bongers,
T. 1990
The maturity
an ecological measure
disturbance
based
on nematode
• ofItenvironmental
should be possible
to increase
structure
withoutspecies
composition.
Oecologia 83:
14-19.
decreasing enrichment,
and
vice versa. The axes
should be independent.
An Enrichment Experiment
Rhabditidae
35,000
30,000
25,000
20,000
15,000
10,000
5,000
0
cp1 Nematodes
50,000
40,000
30,000
Not Enrich.
20,000
Enriched
Not Enrich.
Enriched
Robbins
Leaves
10,000
Robbins
Soil
Hart Soil Placerville
Soil
Panagrolaimidae
0
Robbins
Leaves
Robbins
Soil
Hart Soil Placerville
Soil
15,000
10,000
Not Enrich.
cp2 Nematodes
Enriched
5,000
10,000
0
8,000
6,000
Not Enrich.
4,000
Enriched
Robbins
Leaves
2,000
Robbins
Soil
Hart Soil Placerville
Soil
Aphelenchoididae
0
Robbins
Leaves
Robbins
Soil
Hart Soil Placerville
Soil
10,000
8,000
6,000
Not Enrich.
4,000
Enriched
2,000
0
Robbins
Leaves
Robbins
Soil
Hart Soil Placerville
Soil
Enrichment Indicators
Rhabditidae
Panagrolaimidae
etc.
Short lifecycle
Small/ Mod. body size
High fecundity
Small eggs
Dauer stages
Wide amplitude
Opportunists
Disturbed conditions
Structure Indicators
Aporcelaimidae
Nygolaimidae
etc.
Basal Fauna
Cephalobidae
Aphelenchidae,
etc.
Moderate lifecycle
Small body size
Stress tolerant
Feeding adaptations
Present in all soils
Long lifecycle
Large body size
Low fecundity
Large eggs
Stress intolerant
Narrow amplitude
Undisturbed conditions
Nematode
Faunal Profiles
•Enrichment index
100 (w1.cp1 + w2.Fu2)
/ (w1.cp1 + w2.cp2 )
Enriched
Ba1
Structured
Fu2
fungivores
bacterivores
Fu2
Basal
condition
Basal
Ba2
Ca3
Fu3
Ba3
Om4
Ca4
Fu4
Ba4
omnivores
Om5
carnivores
Ca5
fungivores
Fu5
bacterivores
Ba5
Structure trajectory
Ferris et al., 2001
•Structure Index = 100 wi.cpi / (wi.cpi + w2.cp2 ) for i = 3-5
Nematode Indicators of Soil Food Web Structure and Function
•Disturbed
•N-enriched
•Low C:N
•Bacterial
•Conducive
Ba1
Enriched
Structured
Fu2
•Degraded
•Depleted
•High C:N
•Fungal
Basal
•Conducive
Fu2
Basal
condition
Ba2
Ca3
Fu3
Ba3
Om4
Ca4
Fu4
Ba4
Structure index
Ferris et al., 2001
•Maturing
•N-enriched
•Low C:N
•Bacterial
•Regulated
•Matured
•Fertile
•Mod. C:N
•Bact./Fungal
•Suppressive
Om5
Ca5
Fu5
Ba5
Model Verification….
Tomato
Systems
Yolo Co.
Enrichment Index
Faunal Analysis of some California Soil Systems
Mojave
Desert
100
Prune
Orchards
Yuba Co.
50
0
0
50
Structure Index
Redwood
Forest and
Grass
Mendocino
Co.
100
Model Verification….
Biological Associations in Crop Management Systems
Organic
Conventional
_
Association I
BaNem
PredNem
PredM
Association II
OCT/ONT
+
BI
CI
EI
SI
_
OmnNem
OmnM
FungSapM
ORG
Higher trophic levels
Sánchez-Moreno et al., subm.
+
CST
Fu Nem
PpNem
AlgM
Tests of Ecosystem Services:
The N-Mineralization Service of Bacterivore Nematodes
Effects of Bacterivore Nematodes on
N-Mineralization Rates
14
+Cephalobus
-Cephalobus
N (µg/g Soil)
12
10
8
6
4
2
0
5
10
15
20
25
30
35
40
45
Organic Matter C:N Ratio
C:
N=
4:1
Ferris, Venette and Lau, 1997
C:
N=
6:1
Soil Food Web Management – an experiment
Sustainable Agriculture
Farming Systems Project
1988-2000
Soil Food Web Management – an experiment
Cover crop
Cover crop
Irrigation
temperature
moisture
T0
activity
M0
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
50.00
45.00
40.00
N (ug/g soil)
35.00
30.00
+S+W+I
25.00
-S+W+I
20.00
15.00
-S-W+I
10.00
5.00
-S+W-I
0.00
60
80
100
120
140
160
-S-W-I
Julian Days
Tomato Yields - 1997
50.00
2
y=1 4 .6 - .0 0 5 x; r =0 .2 5 **
60
40.00
50
30.00
Tons/Acre
N (µg/g soil), May 9
60.00
20.00
10.00
0.00
0
1000
2000
3000
4000
5000
Bacterial-Feeding Nem atodes; May 9, 1997
Ferris et al. (2004)
6000
A
A
B
B
B
+I-S-W
-I-S+W
-I-S-W
40
30
20
10
0
+I+S+W
+I-S+W
The Importance
of Diversity
Bacterivore Nematode Abundance
Mesorhabditis
6000
Cruznema
5000
Rhabditis
4000
3000
2000
1000
22-Jul
29-Jul
17-Jun
24-Jun
1-Jul
27-May
15-Jul
24-Jun
20-May
10-Jun
17-Jun
13-May
8-Jul
10-Jun
6-May
3-Jun
27-May
20-May
13-May
6-May
29-Apr
The Service
Service -- N
N mineralization
mineralization
- Functional
Complementarity
- Functional
Redundancy
Mesorhabditis
Mesorhabditis
Cruznema
Cruznema
Rhabditis
Rhabditis
Total N
600
500
400
300
200
100
29-Jul
29-Jul
22-Jul
22-Jul
15-Jul
15-Jul
8-Jul
8-Jul
1-Jul
3-Jun
29-Apr
22-Apr
15-Apr
8-Apr
0
1-Apr
22-Apr
15-Apr
8-Apr
1-Apr
0
The Importance
of Diversity
Mesorhabditis and Acrobeloides Abundance
6000
Mesorhabditis
5000
Acrobeloides bod
4000
3000
2000
1000
900
800
700
600
500
400
300
200
100
0
29-Jul
22-Jul
15-Jul
8-Jul
1-Jul
24-Jun
17-Jun
10-Jun
3-Jun
27-May
20-May
13-May
6-May
The Service - N mineralization
- Functional Continuity
Mesorhabditis
Acrobeloides bod
29-Jul
22-Jul
15-Jul
8-Jul
1-Jul
24-Jun
17-Jun
10-Jun
3-Jun
27-May
20-May
13-May
6-May
29-Apr
22-Apr
15-Apr
8-Apr
Total N
1-Apr
29-Apr
22-Apr
15-Apr
8-Apr
1-Apr
0
Another Ecosystem Service:
• The regulation of opportunistic species
Enrichment Index
100
50
0
0
50
Structure Index
100
Woodland
Vineyard
Density-dependent predation
Soil Suppressiveness
100
95
90
85
80
0
0.1
0.2
Predator:
Prey Ratio
Predator:Prey
Ratio (Density
Class Averages)
Sánchez-Moreno et al., in press
0.3
Managing Input Resources for Food Web Structure and Function:
Carbon Pathways and Pools
Herbivory
(plant source)
Fungal
Omnivory
Decomposition
(detritus and exudates)
Bacterial
Structure of the Soil Food Web in relation to Resource Inputs
Pr
Intake Channel Analysis
%bacterial
B
F
P
O
%plant
%fungal
Resource Inputs: Indices are based on proportions
What about biomass?
% Herbivore
% Bacteriivore
% Fungivore
% Bacteriivore
% Herbivore
Intake Channel Analysis
% Fungivore
Some soil organisms are Herbivores
Herbivory may be a Disservice
Or Herbivory may provide Services
1. It provides resources to the soil food web, often without
measurable plant damage, e.g., Tylenchidae
2. It may place weed species at a competitive disadvantage
Fiddleneck and Anguina amsinckiae
Silverleaf nightshade and Ditylenchus phyllobia
(but it is difficult to find convincing examples)
Intake Channel Analysis
Higher trophic levels
- food web shape
% Bacteriivore
% Herbivore
% Fungivore
Intake Channel Analysis
Higher trophic levels
- food web shape
% Bacteriivore
% Herbivore
% Fungivore
A
C supplied
C:N Low
100
Control
80
Enrichment Index
Resource Inputs:
Transformation
and Succession
C:N High
Plant Materials - Surface
60
40
20
0
0
300
600
900
1200
DD>10
BA
Plant Materials
- Incorporated
Plant Low
C:N
Community structure
shifts
Enrichment Index
Channel Index
100
100
80
80
1
C:N Med.
Control
Cont. Undist.
Cont. Incorp.
40
40
Pl. Incorp.
Pl. Undist.
20
20
0
0
0
B
C:N Low
6060
0
Ferris and Matute (2003)
C:N High
300
600
300 DD>10
600C
DD>10
900
1200
900
1200
Channel Index
Resource
transformation
800
Input Biomass
700
600
500
400
300
200
100
0
0
50
100
150
200
250
300
Time
Infrequent (Punctuated) Resource Input
350
400
800
Input Biomass
700
600
500
400
300
200
100
0
0
50
100
150
200
250
Time
Frequent (Continuous) Resource Input
300
350
400
An Experiment on Continuous Resource Input:
Soil Food Webs and Carbon Dynamics in Response to Conservation
Tillage in Legume Rotations in California
Observation:
The Structure Index did not increase in two years of
organic, no-till, continuous cropping.
Conclusion:
Increase in the Structure Index after changes in management may
involve a prolonged period of recolonization by sensitive species,
that requires many years.
So…. Inoculate nematodes into the vacant niche….
Minoshima et al. (2007)
Continuous input but without
diversity;
disrupted by pesticides and
Continuous
input with enormous
mineral fertilizers
diversity;
not chemically or physically
disrupted
Nematodes are useful bioindicators of
the structure and function of the soil ecosystem
•
•
•
•
•
•
Occupy key positions in soil food webs
Standard extraction procedures
Identification based on morphology
Clear relationship between structure and function
The most abundant of the metazoa
Each sample has high intrinsic information value
Some Literature
•Bongers, T., M. Bongers. 1998. Functional diversity of nematodes. Appl. Soil Ecol. 10, 239251.
•Bongers, T., H. Ferris. 1999. Nematode community structure as a bioindicator in
environmental monitoring. Trends Ecol. Evol. 14, 224-228.
•Ferris, H., T. Bongers, R.G.M. de Goede. 2001. A framework for soil food web diagnostics:
extension of the nematode faunal analysis concept. Appl. Soil Ecol. 18, 13-29.
•Ferris, H., M.M. Matute. 2003. Structural and functional succession in the nematode fauna of
a soil food web. Appl. Soil Ecol. 23:93-110.
•Tenuta, M., H. Ferris. 2004. Relationship between nematode life-history classification and
sensitivity to stressors: ionic and osmotic effects of nitrogenous solutions. J. Nematol. 36:8594.
•Ferris, H. and T. Bongers. 2006. Nematode indicators of organic enrichment. J. Nematol.
38:3-12.
•Sánchez-Moreno, S., H. Minoshima, H. Ferris and L.E. Jackson. 2006. Linking soil properties
and nematode community composition: effects of soil management on soil food webs.
Nematology 8:703-715.
•Sánchez-Moreno, S. and H. Ferris. 2007. Suppressive service of the soil food web: Effects of
environmental management. Agric. Ecosyst. Environ. 119:75-87.
More information:
http://plpnemweb.ucdavis.edu/nemaplex