Role of Insect Herbivores in

1
Role of Insect Herbivores in Plant Community
Structure and Succession
Background Types of Evidence Experimental
Little, due to scale Natural
Ecosystems Large-scale-outbreaks relatively
rare Largely anecdotal Altered
Systems Agroecosystems Invasive
species Biological control of invasive
weeds Evaluation of Specific Processes
2
Landscape - Level Outcomes of Plant - Herbivore
Interactions
Forest Conversion
Canopy Thinning
Gap Formation
3
(No Transcript)
4
Interactions between Below- and Above- Ground
Herbivory
1. Root beetles colonize Vector fungi
4. Fungi pass through root grafts
2. Compromise defense in stem
3. Ips prefer root-infested trees
5
Likelihood of Mortality to Ips Increases with
Proximity to Leptographium - Infected
Trees Among-Stand (17 ) Analysis 1997 - 2000
Erbilgin Raffa 2003
6
Interactions between below- and above- ground
processes in Pinus resinosa mortality and gap
formation
Annual Survey
7
Conversion of conifer to angiosperm forest by
interaction of below- and above- ground
herbivory
1987
1997
2002
8
(No Transcript)
9
Saratoga Spittle Bug
10
(No Transcript)
11
(No Transcript)
12
Jack Pine Budworm
13
Defoliation by jack pine budworm
14
Region - wide Defoliation by Jack Pine Budworm
15
Spruce Budworm
16
Defoliation by Spruce Budworm
Natural Resources Canada, Can. For. Serv.,
Laurentian For. Cent., Pierre Therrien
17
Natural Resources Canada, Can. For. Serv.,
Laurentian For. Cent., René Pâquet
18
Natural Resources Canada, Can. For. Serv.,
Laurentian For. Cent., Claude Monnier
19
Natural Resources Canada, Can. For. Serv.,
Laurentian For. Cent., Jacques Morissette
20
Spruce Beetle
21
Spruce Beetle in Alaska
Eruptive Phase 1992-99 287,500 ha / yr.
Endemic Phase 1955-74 4,000 ha / yr
22
(No Transcript)
23
Conversion of spruce forests to birch and aspen
by spruce beetle in Kenai Peninsula, AK
24
Ecosystem Impacts of Spruce Beetle
Forest composition Succession Fire cycles Solar
reflectance Microclimate Tree-line Riparian
zone Soil nutrients microbiota Bird mammal
habitat
25
Mountain Pine Beetle in Rocky Mountains
Endemic phase
Eruptive phase
26
(No Transcript)
27
Lodgepole Pine Surrounded by Spruce in
BC Mortality to Mountain Pine Beetle
28
Current Outbreak of Mountain Pine Beetle in
British Columbia
Carroll, Taylor Regnierre 2003
29
Life History of Lodgepole Pine
30
(No Transcript)
31
(No Transcript)
32
Reproductive Ecology and Competitive Status of
Lodgepole Pine
0-40 Larch, Aspen 41-60 Larch, Aspen, LP
Pine 61-110 LP Pine 111-140 LPP, Doug Fir,
Spruce
33
Raffa Berryman 1987
34
Altered Systems Illustrate Potential of
Herbivory Agroecosystems Continual
outbreak Early successional plant
species Invasive species Gypsy moth in US, Fall
webworm in Eurasia, Balsam Woolly Adelgid in US,
Wood wasps in Australia, etc. Biological control
of invasive weeds Natural experiments Prickly
pear, St. Johnswort, etc.
35
Ecosystem Processes Natural Controlled
Conditions Compensatory Growth Chronic herbivory
in grasslands Growth release in trees Douglas
fir tussock moth Certain species favored -
differential impact on composition Can keep
community in early successional state Other
Differential Impacts Altered age structure, Can
accelerate succession. Increased Light
Reflectance .Jack pine budworm
36
Ecosystem Processes Natural Controlled
Conditions Increased Light Penetration Release
of understory plants - competition Warm, dry
soil Soil microbes, decomposers,
herbivores Altered Patterns of
Nutrification Increased nutrient leaching from
foliage (pre-autumnal foliage has higher
nutrients that normal leaf-fall) Litter is often
induced - high in digestion-inhibitors Deposition
of frass and cast skins Altered nutrient patterns
alter plant architecture Effects on
wildlife .Nutrient pulses into aquatic ecosystems
(bacterial blooms)
37
Ecosystem Processes Natural Controlled
Conditions Soil Erosion Altered Fire
Cycles. Altered Genetic Structure Herbivores
Select for diversity? Pollinators Promote
outcrossing Seed dispersers (e.g.) ants
Generate spatially local genetic structure
38
Experimental Approaches Ritchie, M.E. et al.
1998. Ecology Compared Caged and Uncaged Areas
of Oak Savannah Recorded observations over 6
yrs Plant group (Legumes, Grasses, Woody, Forbs)
composition (cover, biomass) and their
changes Nutrients Carbon and Nitrogen
Allocation Light