
Reading for next lectures • Textbook Chapters 8, 10, 12, 13
Seminars • Dr. Julia Koricheva, University of Turku, Finland. Direct and indirect costs of plant resistance to herbivores. EECB seminar Thurs Feb 26, 4:00 PM OSN 120
Outline • Herbivory in Australian woodland • Introduction to community ecology • Introduction to ecosystems ecology • Community concepts • Ecosystems analysis
Questions • How does herbivory affect woodland species? • Does habitat alter response to grazing or impact of herbivores? • Do different herbivores have different effects?
Photo: Taronga Zoo, Sydney NSW Photo: CSIRO Wildlife and Ecology
Burrendong Dam Study Area • Approx. 100 km2 in the Central West Slopes region, NSW, Australia near the center of White Box distribution. • Mosaic of eucalypt woodland, native pine woodland, cleared grassland, and alluvial flats.
Study Design • Fencing treatments established in January and February 1997 • 4 treatments (control, stock fence, kangaroo fence, rabbit fence) • 2 habitats (eucalypt woodland, cleared grassland)
Study Design 25m by 25m fences, four replicates Woodland Grassland control stock control stock kangaroo complete kangaroo complete Four Blocks Four Blocks
Study Design Transplants: Eucalyptus albens, Callitris glaucophylla, andThemeda australis. Planted in grassland and woodland plots in Apr 1998.
Summary • Three groups of grazing animals: • Four treatments: • Two habitats: • Three target species: • Monitored survival for all species, and created models based on size growth for trees.
Browse preferences Grassland Woodland
C S K R C S K R Eucalyptus mortality C-control S-Stock K-Kangaroo R-Rabbit # Trees Dead Grassland Woodland
C S K R C S K R Callitris Mortality 1-control 2-Stcock 3-Kangaroo 4-Rabbit C-control S-Stock K-Kangaroo R-Rabbit # Trees Dead Grassland Woodland
C S K R C S K R Woodland Grassland Themeda mortality C-control S-Stock K-Kangaroo R-Rabbit # Plants Dead
“Life history” transition diagram • Transitions between 5 size (height) classes for trees; final stage is “escape from herbivory”. • Models created for each habitat and treatment combination.
P 35 P 25 P P 15 P 14 24 P 13 P P P S P S S S S 23 34 45 12 3 5 1 2 4 P P P P P 22 33 44 55 54 P P P P 21 18 11 43 P P P 51 52 53 P 42 P 41 P 31 S S S S S S S S S S Matrix Two 1 2 3 4 5 Matrix One 1 2 3 4 5 P P P P P S [<25 cm] 0 P 0 0 0 S [<25 cm] 11 21 31 41 51 1 21 1 P P P P P S [25 - 49 cm] 0 P 0 0 0 S [25 - 49 cm] 12 22 32 42 52 2 22 2 P P P P P S [50 - 74 cm] 0 P 0 0 0 S [50 - 74 cm] 13 23 33 43 53 3 23 3 P P P P P S [75 - 100 cm] 0 P 0 0 0 S [75 - 100 cm] 14 24 34 44 54 4 24 4 P P P P P S [ >100 cm] 0 P 0 0 0 S [ >100 cm] 15 25 35 45 55 5 25 5
Summary • Plants in productive environment better able to compensate (more rapid growth) • High herbivory rate in unfenced low productivity habitats prevented “escape”. • This could have population consequences even though mortality was fairly low. • Differences in herbivore preference could be translated to community composition. • Interaction between competition and herbivory…tradeoff.
Community and ecosystems ecology • Community ecology: study of all organisms (plants?) in a given area. = synecology; species/organism based. • Ecosystems ecology: study of energy and matter flows, productivity, and cycling. Process/energy based.
Community and ecosystems ecology • Forest and range ecosystem function, management, and productivity can be viewed from either community or ecosystem viewpoint:
Historic community concepts Clements (1905): “super-organism” concept. • Plant species associate/co-occur in a predictable way, proceeding to a “climax” configuration determined by climate. • A community has emergent organism-like properties; can be classified into distinct idealized types. • In North America, 3 climax types: grassland, scrub and forest. Divided into subtypes (e.g. true grasslands VS sedge meadows; sagebrush VS desert scrub VS chaparral; coastal VS montane forest), then into “associations” (= communities). • Distinctions often driven by most obvious plant species (e.g. trees) • Basis for ecological site types, potential vegetation, and community classifications used by BLM and USFS
Historic community concepts II Gleason (1917): individualistic concept • Each species responds individually to environment and species around it. • There are no predictable associations or emergent “organismal” properties • Plant associations do exist – we can see them, describe them, relate them to environment; BUT they are due simply to juxtaposition of individual plants • “[the community] is not an organism, but merely a coincidence” • Some argue that Gleason downplays importance of site characteristics (soils, water, nutrients) too much…
Current understanding • Closer to Gleason’s than to Clements’s view • Communities are identifiable, but boundaries can be vague • “Climax” now used for communities undisturbed long enough to pass through several generations of dominant species • “Super-organsism” concept still shows up in some definitions of ecosystems and ecosystem management • “Ecological site” descriptions try to include ecosystem properties as well as vegetation composition
Ecosystems ecology • Concerned with nutrient fluxes, biogeochemical cycles, and energy balances. • Ecosystems analysis (p 358 text). • Long term monitoring of ecosystem (watershed). • Measurement of nutrient and water fluxes andcycling, as well as productivity. • Create nutrient budgets. • Other means of investigating: microcosms; computer simulations.