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
Slide 2 Soil Food Web Functions - metabolic and behavioral
activities of organisms that impact the biotic or abiotic
components of the ecosystem Feeding: Ingestion, assimilation,
defecation and excretion Behavior: 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 Mineralize organic
molecules Accelerate turnover Regulate and suppress pests Alter
substrate to provide access to other organisms Redistribute
organisms in space Reduce soil erosion Increase agricultural
production Individual species services Aggregate food web services
Slide 3 Positive and Negative Feedback in Food Web Services
bacteria and bacterivore nematodes with twenty nematodes 0
nematodeswith five nematodes Fu et al. 2005 Slide 4 Linkages and
Connectance among Functional Guilds Nematodes at each trophic level
Slide 5 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 Slide 6 Photograph courtesy
of Dr. Jerry Glover The Land Institute, Kansas 1 2 Soil Depth (m) 0
annual wheatperennial intermediate wheatgrass Bottom up effects:
Resource availability Soil Food Webs Slide 7 OPr B F P O B F P
Mineralization Regulation Effects of: tillage tertilizers
pesticides punctuated cropping type and amount of organic input
Soil Food Web: Functions and Services in relation to Structure
Slide 8 Environmental heterogeneity Zones and Gradients: texture
structure temperature water O 2 CO 2 NO 3 NH 4 minerals Soil Food
Webs environmental factors affecting Structure Separate
metacommunities? Slide 9 Nematode Sensitivity to Mineral Fertilizer
Tenuta and Ferris, 2004 Soil Food Webs environmental effects on
Structure Slide 10 Soil Nematodes as Bioindicators: Functional
Diversity Slide 11 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. A milestone contribution: When
feeding on their prey, bacterial- and fungal- feeding nematodes
excrete N that is in excess of their structural and metabolic
needs. Slide 12 12345 enrichmentstability opportunismstructure
Colonizer-persister Series Weighting: should the separations
between the classes be equal? Bongers Another milestone -
calibration of ecosystem condition: Maturity Index = Bongers, T.
1990 The maturity index: an ecological measure of environmental
disturbance based on nematode species composition. Oecologia 83:
14-19. Issues of proportions: If the proportion of opportunists
increases, the proportion of sensitive species decreases. It should
be possible to increase structure without decreasing enrichment,
and vice versa. The axes should be independent. Slide 13 An
Enrichment Experiment Slide 14 Slide 15 Rhabditidae Panagrolaimidae
etc. Short lifecycle Small/ Mod. body size High fecundity Small
eggs Dauer stages Wide amplitude Opportunists Disturbed conditions
Aporcelaimidae Nygolaimidae etc. Long lifecycle Large body size Low
fecundity Large eggs Stress intolerant Narrow amplitude Undisturbed
conditions Enrichment Indicators Structure Indicators Cephalobidae
Aphelenchidae, etc. Moderate lifecycle Small body size Stress
tolerant Feeding adaptations Present in all soils Basal Fauna Slide
16 Ba 2 Fu 2 Ba 1 Ba 3 Fu 3 Ca 3 Ba 4 Fu 4 Ca 4 Om 4 Ba 5 Fu 5 Ca 5
Om 5 Enriched Structured Basal condition Structure trajectory
Enrichment trajectory omnivores carnivores fungivores bacterivores
fungivores bacterivores fungivores bacterivores Nematode Faunal
Profiles Enrichment index 100 (w1.cp1 + w2.Fu2) / (w1.cp1 + w2.cp2
) Structure Index = 100 wi.cpi / (wi.cpi + w2.cp2 ) for i = 3-5
Ferris et al., 2001 Slide 17 Ba 2 Fu 2 Ba 1 Ba 3 Fu 3 Ca 3 Ba 4 Fu
4 Ca 4 Om 4 Ba 5 Fu 5 Ca 5 Om 5 Enriched Structured Basal condition
Structure index Enrichment index Disturbed N-enriched Low C:N
Bacterial Conducive Maturing N-enriched Low C:N Bacterial Regulated
Matured Fertile Mod. C:N Bact./Fungal Suppressive Degraded Depleted
High C:N Fungal Conducive Nematode Indicators of Soil Food Web
Structure and Function Ferris et al., 2001 Slide 18 0 50 100 050100
Structure Index Enrichment Index Prune Orchards Yuba Co. Mojave
Desert Tomato Systems Yolo Co. Redwood Forest and Grass Mendocino
Co. Faunal Analysis of some California Soil Systems Model
Verification. Slide 19 OmnNem OmnM FungSapM Biological Associations
in Crop Management Systems Model Verification. Snchez-Moreno et
al., subm. Higher trophic levels OrganicConventional Slide 20 Tests
of Ecosystem Services: The N-Mineralization Service of Bacterivore
Nematodes Slide 21 Effects of Bacterivore Nematodes on
N-Mineralization Rates Ferris, Venette and Lau, 1997 C: N = 4:1 C:
N = 6:1 Slide 22 Sustainable Agriculture Farming Systems Project
1988-2000 Soil Food Web Management an experiment Slide 23 Cover
crop Irrigation temperature moisture activity T0T0 M0M0 Soil Food
Web Management an experiment Slide 24 Ferris et al. (2004) Slide 25
The Importance of Diversity Slide 26 The Importance of Diversity
Slide 27 Another Ecosystem Service: The regulation of opportunistic
species Slide 28 Density-dependent predation Predator: Prey Ratio
Snchez-Moreno et al., in press Slide 29 Managing Input Resources
for Food Web Structure and Function: Carbon Pathways and Pools
Omnivory Decomposition Herbivory Bacterial Fungal (plant source)
(detritus and exudates) Slide 30 OPr B F P Structure of the Soil
Food Web in relation to Resource Inputs Intake Channel Analysis
Slide 31 Resource Inputs: Indices are based on proportions What
about biomass? Intake Channel Analysis Slide 32 Some soil organisms
are Herbivores Slide 33 Herbivory may be a Disservice Slide 34 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) Or Herbivory may provide
Services Slide 35 Higher trophic levels - food web shape Intake
Channel Analysis Slide 36 Higher trophic levels - food web shape
Intake Channel Analysis Slide 37 C supplied Resource transformation
Community structure shifts Ferris and Matute (2003) Resource
Inputs: Transformation and Succession Slide 38 Infrequent
(Punctuated) Resource Input Slide 39 Frequent (Continuous) Resource
Input Slide 40 An Experiment on Continuous Resource Input: Soil
Food Webs and Carbon Dynamics in Response to Conservation Tillage
in Legume Rotations in California So. Inoculate nematodes into the
vacant niche. Minoshima et al. (2007) 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. Slide 41 Continuous
input but without diversity; disrupted by pesticides and mineral
fertilizers Continuous input with enormous diversity; not
chemically or physically disrupted Slide 42 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 Nematodes are useful bioindicators of the
structure and function of the soil ecosystem But we have more to
learn about management of higher trophic levels in the Soil Food
Web Slide 43 Bongers, T., M. Bongers. 1998. Functional diversity of
nematodes. Appl. Soil Ecol. 10, 239- 251. 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. 36:85- 94. Ferris, H. and T. Bongers. 2006.
Nematode indicators of organic enrichment. J. Nematol. 38:3-12.
Snchez-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.
Snchez-Moreno, S. and H. Ferris. 2007. Suppressive service of the
soil food web: Effects of environmental management. Agric. Ecosyst.
Environ. 119:75-87. Some Literature More information:
http://plpnemweb.ucdavis.edu/nemaplex
