Functions and Services of the Soil Food Web: Nematodes as Biological Indicators Howard Ferris Department of Nematology University of California, Davis February, 2008

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

Positive and Negative Feedback in Food Web Services bacteria and bacterivore nematodes with twenty nematodes 0 nematodeswith five nematodes Fu et al. 2005

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

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

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

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?

Nematode Sensitivity to Mineral Fertilizer Tenuta and Ferris, 2004 Soil Food Webs – environmental effects on Structure

Soil Nematodes as Bioindicators: Functional Diversity

Ingham Ingham, R.E., J.A. Trofymow, E.R. Ingham, and D.C. Coleman Interactions of bacteria, fungi, and their nematode grazers: Effects on nutrient cycling and plant growth. Ecological Monographs 55: 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.

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 The maturity index: an ecological measure of environmental disturbance based on nematode species composition. Oecologia 83: 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.

An Enrichment Experiment

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

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

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

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….

OmnNem OmnM FungSapM Biological Associations in Crop Management Systems Model Verification…. Sánchez-Moreno et al., subm. Higher trophic levels OrganicConventional

Tests of Ecosystem Services: The N-Mineralization Service of Bacterivore Nematodes

Effects of Bacterivore Nematodes on N-Mineralization Rates Ferris, Venette and Lau, 1997 C: N = 4:1 C: N = 6:1

Sustainable Agriculture Farming Systems Project Soil Food Web Management – an experiment

Cover crop Irrigation temperature moisture activity T0T0 M0M0 Soil Food Web Management – an experiment

Ferris et al. (2004)

The Importance of Diversity

The Importance of Diversity

Another Ecosystem Service: The regulation of opportunistic species

Density-dependent predation Predator: Prey Ratio Sánchez-Moreno et al., in press

Managing Input Resources for Food Web Structure and Function: Carbon Pathways and Pools Omnivory Decomposition Herbivory Bacterial Fungal (plant source) (detritus and exudates)

OPr B F P Structure of the Soil Food Web in relation to Resource Inputs Intake Channel Analysis

Resource Inputs: Indices are based on proportions What about biomass? Intake Channel Analysis

Some soil organisms are Herbivores

Herbivory may be a Disservice

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

Higher trophic levels - food web shape Intake Channel Analysis

Higher trophic levels - food web shape Intake Channel Analysis

C supplied Resource transformation Community structure shifts Ferris and Matute (2003) Resource Inputs: Transformation and Succession

Infrequent (Punctuated) Resource Input

Frequent (Continuous) Resource Input

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.

Continuous input but without diversity; disrupted by pesticides and mineral fertilizers Continuous input with enormous diversity; not chemically or physically disrupted

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

Bongers, T., M. Bongers Functional diversity of nematodes. Appl. Soil Ecol. 10, Bongers, T., H. Ferris Nematode community structure as a bioindicator in environmental monitoring. Trends Ecol. Evol. 14, Ferris, H., T. Bongers, R.G.M. de Goede A framework for soil food web diagnostics: extension of the nematode faunal analysis concept. Appl. Soil Ecol. 18, Ferris, H., M.M. Matute Structural and functional succession in the nematode fauna of a soil food web. Appl. Soil Ecol. 23: Tenuta, M., H. Ferris Relationship between nematode life-history classification and sensitivity to stressors: ionic and osmotic effects of nitrogenous solutions. J. Nematol. 36: Ferris, H. and T. Bongers Nematode indicators of organic enrichment. J. Nematol. 38:3-12. Sánchez-Moreno, S., H. Minoshima, H. Ferris and L.E. Jackson Linking soil properties and nematode community composition: effects of soil management on soil food webs. Nematology 8: Sánchez-Moreno, S. and H. Ferris Suppressive service of the soil food web: Effects of environmental management. Agric. Ecosyst. Environ. 119: Some Literature More information: