Nematode Assemblages as Plant Health Indicators a soil

Nematode Assemblages as Plant Health Indicators - a soil food web perspective Howard Ferris Department of Nematology University of California, Davis hferris@ucdavis. edu July, 2007

Functional Diversity of Soil Nematodes

Soil Food Web Functions - metabolic and behavioral activities 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 or Disservices: Damage to plants of agricultural or ornamental significance Injury to humans and vertebrate animals Services: Sequestration and redistribution of minerals Mineralization of organic molecules Acceleration of turnover Regulation and suppression of pests Substrate alteration providing access to other organisms Phoretic redistribution of organisms

Functional Diversity in relation to Structure of the Soil Food Web Effects of: Mineralization B F P P O O Pr Regulation Pr tillage tertilizers pesticides punctuated cropping type and amount of organic input

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

Soil Food Web Structure is strongly influenced by nature and frequency of Carbon and Energy Input Resources • Carbon is respired by all organisms in the web • The amounts of Carbon and Energy available limit the size and activity of the web P F B O Pr

Soil Food Webs – environmental effects on Structure Environmental heterogeneity Separate metacommunities? Zones and Gradients: texture structure temperature water O 2 CO 2 NO 3 NH 4 minerals

Soil Food Webs – environmental effects on Structure Standardized Counts Nematode Sensitivity to Mineral Fertilizer Ammonium sulfate 200 Nematode guild 150 100 c-p 1 c-p 2 c-p 3 c-p 4 X c-p 5 X 50 X X 0 0 0. 02 0. 05 0. 1 X X 0. 5 1 Concentration (m. M-N) Tenuta and Ferris, 2004

Some soil nematodes 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)

Observation • A preponderance of herbivores in the nematode assemblage is an indicator that recent soil management has diminished functional diversity in the soil food web.

Indices of Structural Diversity are available • Species richness • Simpson’s diversity index • Shannon’s diversity index • etc. From these we infer ecosystem characteristics, e. g. , regulation …but they provide no information on food and feeders, prey and predators Functional Diversity is more difficult to assess

19 th Century to mid 20 th Century discovery of abundance and habitat diversity Maupas Bastian Cobb 20 th Century to present functional diversity and bioindicator potential Ingham Wall Bongers Yeates

A milestone contribution: 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. When feeding on their prey. bacterial- and fungalfeeding nematodes excrete N that is in excess of their structural and metabolic needs. Ingham

Calibration of Ecosystem Function: Colonizer-persister Series Maturity Index = opportunism structure enrichment stability 1 2 3 4 5 Bongers, 1990 Weighting: • should the separations between the classes be equal? Issues of proportions: • • Bongers 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.

t tr aje res riv o cte ba ore giv fun cto ry Enriched Ba 1 En ric hm en • Enrichment index 100 (w 1. cp 1 + w 2. Fu 2) / (w 1. cp 1 + w 2. cp 2 ) s Nematode Faunal Profiles Structured Fu 2 fungivores bacterivores Basal condition Fu 2 Basal Ba 2 Ca 3 Fu 3 Ba 3 Om 4 Ca 4 Fu 4 Ba 4 omnivores Om 5 carnivores Ca 5 fungivores Fu 5 bacterivores Ba 5 Structure trajectory Ferris et al. , 2001 • Structure Index = 100 wi. cpi / (wi. cpi + w 2. cp 2 ) for i = 3 -5

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

• Disturbed • N-enriched • Low C: N • Bacterial • Conducive Ba 1 Enriched • Maturing • N-enriched • Low C: N • Bacterial • Regulated En ric hm en t in de x Nematode Indicators of Soil Food Web Structure and Function • Degraded • Depleted • High C: N • Fungal Basal • Conducive Fu 2 Basal condition Structured Fu 2 Ba 2 Ca 3 Fu 3 Ba 3 Om 4 Ca 4 Fu 4 Ba 4 Structure index Ferris et al. , 2001 Om 5 Ca 5 Fu 5 Ba 5 • Matured • Fertile • Mod. C: N • Bact. /Fungal • Suppressive

Faunal Analysis of some California Soil Systems Enrichment Index Tomato Systems Yolo Co. Mojave Desert 100 Prune Orchards Yuba Co. 50 0 0 50 Structure Index Redwood Forest and Grass Mendocino Co. 100

Calibration of the N-Mineralization Service of Bacterivore Nematodes

Effects of Bacterivore Nematodes on N-Mineralization Rates 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 Irrigation temperature moisture T 0 activity M 0

Ferris et al. (2004)

The Importance of Diversity

Another Ecosystem Service: • The regulation of opportunistic species Enrichment Index 100 50 0 0 50 Structure Index 100 Woodland Vineyard

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

Managing Input Resources for Food Web Structure and Function: Carbon Pathways and Pools Herbivory Fungal Omnivory Decomposition Bacterial

B F P O Pr Structure of the Soil Food Web in relation to Resource Inputs

Indices are based on proportions What about biomass?

Higher trophic levels - food web shape

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

Infrequent Resource Input

Frequent Resource Input

Another Experiment: 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 Structure Index after changes in management may involve a prolonged period of recolonization by sensitive species, requiring many years. So…. Inoculate nematodes into the vacant niche…. Minoshima et al. (2007)

e em Nematodes are useful bioindicators of ag n a soil condition and Plant Health M • • • eb W Occupy key positions in soil food webs d o o Standard extraction proceduresoil F S t Identification based on morphology u o b a Clear relationship between n structure and function r a e l The most abundanttoof the metazoa h c Each sample has u high intrinsic information value m e v a h l l i st e w t u More information: http: //plpnemweb. ucdavis. edu/nemaplex B ! t n