Nematodes in the Soil Food Web

Servicios ecosistémicos de los
nematodos de vida libre del suelo
en plantaciones de banano
La salud del suelo
Nematodos como facilitadores y bioindicadores
Howard Ferris
Department of Entomology and Nematology
University of California, Davis
y Bioversity International
July, 2013
Bacteria
Protozoa
many soil organisms
Nematodes
Microarthropods
performing many ecosystem services
Soil Food Web: Nematodes
Resource Flow
as Bioindicators
among Functional Guilds
Regulaters
Top Predators
Mineralizers
Sources
Consumers
Fixers
Immobilizers
Producers
Opportunists
Photosynthates
osynthates
Some better-known ecosystem services of nematodes
1. N-mineralization
Soil Food Web Management – an analysis
experiment
Cover crop
Cover crop
Irrigation
N
temperature
moisture
T0
activity
M0
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Many soil organisms are predators….
Another ecosystem service experiment:
2. The regulation of opportunistic species
Soil Suppressiveness
100
95
90
85
80
0
0.1
0.2
Predator:
Prey Ratio
Predator:Prey
Ratio (Density
Class Averages)
0.3
Food Web Complexity and the
Regulation Function
Management practices in industrialized
agriculture result in:
Soil food web simplification
Reduction in higher trophic levels
We tested evolving nematode predator:prey hypotheses with data
from banana plantations in four Central American
countries……….
Predators and prey – the Apparent Competition Hypothesis
Target Prey
Plant-feeding Nematodes
Amplifiable Prey
Fungal-, bacterial-feeding
Nematodes
Generalist and
Specialist Predators
Amplifiable and target prey – the expanded model
A=favorable conditions for predators
Functional complementarity
B=co-location of predators and prey
+
E4
Other Prey
A
Predator Nematodes
-
Other Predators
+
+
B
-
B
+
A
E1
Amplifiable Prey
Target Prey
+
B
B
-
+
E2
-
Microbial Biomass
E5
+
E6
Nematophagous Fungi
Rhizosphere Bacteria
+
+
+
+
+
Protozoa
+
+
+
Organic Matter
E3
+
+
Plant Roots
Root Associate
Nematodes
Litter
+
+
Banana Plantations - Panama
Ln Predator-Target Prey Ratio
B
0
-0,5
-1
-1,5
-2
-2,5
y=-4.97+0.852 x; R2=0.33; p<0.0001
-3
-3,5
2,8
3,3
3,8
4,3
Ln Amplifiable Prey Abundance
Target Prey:
the ring nematode
Shared Predator:
Hirsutella rhossiliensis
Amplifiable Prey:
and
Connectance:bacterialthe proportion
of the potential links in a food web
fungal-feeding
that are (or can be) realized
nematodes
Enhancing Amplifiable Prey
Organic banana
production system
Costa Rica
Engineering Functional Connectance….
Consider effects of drip irrigation
Functional Connectance
Co-location of Predators and Prey
1
opportunism
2
3
4
enrichment
5
structure
stability
Colonizer-persister Series
Structure Indicators
Basal Fauna
Enrichment Indicators
Life course duration
Growth rates
Response to resources
Assessment of Function:
Nematode Faunal Profile: Food Web Structure and Function
•Disturbed
•N-enriched
•Low C:N
•Bacterial
•Conducive
Ba1
Enriched
Structured
Fu2
Fu2
Basal
condition
Ba2
•Maturing
•N-enriched
•Low C:N
•Bacterial
•Regulated
•Degraded
•Depleted
•High C:N
•Fungal
Basal
•Conducive
Ca3
Fu3
Ba3
Om4
Ca4
Fu4
Ba4
Structure index
•Matured
•Fertile
•Mod. C:N
•Bact./Fungal
•Suppressive
Om5
Ca5
Fu5
Ba5
What is the magnitude of the function or service?
How much carbon is being processed?
How much energy is being used?
The indices are useful, but…..…
They do not indicate biomass, metabolic activity or magnitude
of functions/services – so, we develop the Metabolic Footprint
based upon growth and metabolic rates
Nematode Faunal Profiles and the Metabolic Footprint
Enriched
•Enrichment index
100 (w1.cp1 + w2.Fu2)
/ (w1.cp1 + w2.cp2 )
Ba1
Structured
Fu2
fungivores
bacterivores
Fu2
Basal
condition
Basal
Ba2
Ca3
Fu3
Ba3
Om4
Ca4
Fu4
Ba4
Structure trajectory
Om5
Ca5
Fu5
Ba5
omnivores
carnivores
f g
fungivores
bacterivores
The Importance of Diversity
Spatial Diversity of Microsites and their Temporal
Dynamics
gradient drivers:
temperature
moisture
aeration
organic
residues
roots
soil texture
particle size
temporal drivers:
diurnal
seasonal
life course
phenology
degree-days
stochastic factors:
roots
patch distribution
patch composition
weather events
burrows
stones
restrictive
layers
1
2
•
Different numbers of species of each
functional guild in each patch
•
The abundance of individuals of each
species varies among patches and
through time
3
Functional Species Diversity Calculations
Total species diversity
y
where pi is the proportional
abundance of taxon i of the S taxa
Guild diversity
where pj is the proportional
abundance of guild j of the G guilds
Within guild species diversity
y
where pij is the proportional
abundance of taxon i
in guild j
Abundance may be measured as number of individuals, biomass,
metabolic footprint of each type
Abundance measured as number of individuals
1
2
3
4
5
6
7
8
9
10
11
12
12
Cruz Mesor Panag Rhab A’boid Acrob Ceph Monh Plect Wilso Aphel Aphoi Dityl
14
15
16
17
18
Filen Achro Dipht Alaim Tylol
b1
b1
b1
b1
b2
b2
b2
b2
b2
b2
f2
f2
f2
f2
b3
f3
b4
f4
75
22
82
55
120
18
5
13
10
2
15
22
2
5
1
6
5
6
Total species diversity = 6.8
Guild diversity = 2.5
Total
464
(effective number of species)
(effective number of guilds)
Mean within-guild species diversity = 2.7
Abundance measured as biomass
1
2
3
4
5
6
7
8
9
10
11
12
12
Cruz Mesor Panag Rhab A’boid Acrob Ceph Monh Plect Wilso Aphel Aphoi Dityl
14
15
16
17
18
Filen Achro Dipht Alaim Tylol
Total
b1
b1
b1
b1
b2
b2
b2
b2
b2
b2
f2
f2
f2
f2
b3
f3
b4
f4
75
22
82
55
120
18
5
13
10
2
15
22
2
5
1
6
5
6
464
776
12
50
412
18
15
1
15
10
0.1
3
4
1
0.5
0.3
4
2
5
1330
Total species diversity = 2.3
Guild diversity = 1.1
(effective number of species)
(effective number of guilds)
Mean within-guild species diversity = 2.1
A working hypothesis:
effective number of species within guilds
(mean within-guild species diversity)
Complementarity of ecosystem function in relation to species diversity
within and among functional guilds
exploitative
species
diversity
sustained
function
1
successional
guild
diversity
effective number of guilds
(total guild diversity)
2
3
Management of sustainable systems
requires maintaining the flow of
energy to each trophic level and
providing a favorable environment
for the higher trophic levels
Economies of Ecosystems: Carbon and Energy are the Currencies
CO2
carbohydrates
and
proteins
carbohydrates C
and
amino acids N
CO2
CO2
bacteria
protozoa
nematodes
nematodes
nematodes
other
arthropods
organisms
fungi
fungi
NO3
Carbon and energy transfer
CO2
arthropods
nematodes
•Carbon
is respired by all
organisms in the food web
Carbon and
NH3 •The amounts
NHof
NH3
3
Energy available limit the size
and activity of the web
Winter cover crop – bell beans
Soil Food Web Stewardship
California, 2006
•Soil fertility
•Organic matter
•Food web activity
•Soil structure
•Fossil fuel reduction
•Habitat conservation
•Food web activity
•Soil structure
Constraints to species diversity and abundance
Standardized Counts
Example: 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
0
X X
0 0.02 0.05 0.1
X X
0.5
1
Concentration (mM-N)
Soil Food Web
Ecosystem Services
The Nematode Assemblage - Tools for Soil Health Assessment
• Nematode Faunal Profile:
Enrichment and Structure Indices
• Metabolic Footprints:
Magnitude of Ecosystem Services
• Functional Diversity:
Complementarity of Ecosystem Services
Muchas gracias!
http://plpnemweb.ucdavis.edu/nemaplex