1. Community effects on ecosystem processes
CMM Chap. 12
I. Introduction
A. The context –
1. ClORPT
2. Loss of biodiversity
3. Species invasions
B. What is biodiversity?
C. What is ecosystem functioning?
II. Organism effects on ecosystem processes
A. Community determinants
B. Functional determinants: interactive controls
III. Effects of diversity on ecosystem processes
A. Magnitudes of processes
B. Stability of processes
C. Synthesis
Powerpoint modified from Chapin (

2. A.1. State factors and interactive controls:
Species effects on interactive controls determine ecosystem consequences
1.3
How will changing biodiversity affect ecosystem functioning?

3. 2. The context: altered biodiversity
Chapin et al. 2000

4. 2a. Loss of Global Biodiveristy: Current extinction rates are 10-100 fold higher than past
- Extinction rates ~ fold greater than background
- Caused by human activities
- What are the ecosystem consequences?
100 well-documented extinctions in last 100 years of birds, mammals and amphibians
Examples: great auks, passenger pigeons, numerous birds on guam (brown tree snake), others? Which? Where?
IUCN red list has 784 documented extinctions since 1500.
12.1

5. The “Sixth Extinction”?
2. Devonian 370 mya
5. Cretaceous 65 mya
1. Ordovician 440 mya
4. Triassic 210 mya
The scale of the current extinctions is on par with known extinctions from the geological record, of which there have been 5.
Most famous: end of the cretaceous when dinosaurs went extinct probably because of an asteroid impact. Biggest was the Permian extinction about 230 mya, when ~50% of families of taxa disappeared. Not known why.
3. Permian 250 mya
National Geographic 1999

6. 2b. Loss of Regional Biodiveristy:
Problems can occur long before species go extinct.
- Local or regional extinction (extirpation) can be just as important and maybe more important than global extinctions. It is certainly more common.
- Complete species loss from a given area not required
- Changes in relative abundance of native species can have
large impacts, especially if changes involve a
dominant species
- Caused by human activities
- What are the ecosystem consequences?
© National Geographic Magazine 2007

7. 3. Introductions of exotic species
Washington examples (to name just a few):
Cheatgrass (Bromus tectorum) (eastern WA)
Biotic change of global proportions
Local or regional “exotics”; e.g. Mountain Goats in the Olympics. Mountain goats are native to the Cascades but geologic evidence indicates they never occurred in the Olympics prior to introduction.
Spartina alterniflora (cordgrass) in Gray’s Harbor
European Green crab (Carcinus maenas)

8. Shifts in species can be difficult, expensive, or impossible to reverse.
Changes in species can lead to new ecosystem states from which it is very difficult to change back – difficult, expensive, time consuming if at all.
Costs: $138 billion/yr (1999 dollars) according to researchers at Cornell (OTA ~$1.1 billion/yr; NASA – billion/yr for monitoring, containment, eradication of invasive species ( compared to cost of war in Iraq ~$420 billion over the last 4 years. (
~$9 billion/mo as estimated by Congressional Budget Office (CBO) = $108 billion/yr (
Reed canary grass, Whatcom County

9. Introductions Establishment Invasions Noxious pests
Not all introduced species become problems in their new habitat, but those that do can cause extensive ecological and economic damage.
Introductions
Establishment
Invasions
Noxious pests

10. B.What is biodiversity? Genetic Species Functional groups
Effect
Response
Community types
Ecosystem arrangement on the landscape

11. Salmon - Genetic diversity maintains local adaptation
Risk of extinction of Chinook stocks
Individual stocks show a different picture, however.
Ok in AK, but S parts of range is problematic on both continents
Represents evolutionary potential
Augerot 2005

12. Functional group diversity: Need to understand how responses link to effects on processes.
Different response groups
Suding et al

13. Understanding interactions
Cows are good?!
Bay checkerspot
Invasive grasses
Plantago erecta
Need knowledge of biology – in this case grazing done in concert with conservation biologists assessing populations of the endangered Bay Checkerspot butterfly.
L. Gonzalez photos 2005
D. Hooper photos 2005

14. Ecosystem distribution matters for some services
Wetlands & riparian buffers:
Flood control,
Nutrient filtration
Good, Bad and Beauty.
Include student photos.

15. C. What is ecosystem functioning?
Ecosystem properties (non-qualitative) (production, nutrient cycling, energy flux, etc.)
Ecosystem goods – (“Provisioning services”) directly marketable
Ecosystem services – benefit human endeavor, but harder to quantify in economic terms
Regulating: pollination, pest control, water purification, maintenance of soil fertility, climate regulation, etc.;
Cultural: recreational, educational, spiritual, etc.

16. II. Organism effects on ecosystem processes
A. Community context

17. Impact of organisms on ecosystems depends on:
D. Species interactions
What are keystone species?

18. B. Functional Effect Traits
Species’ functional traits influence ecosystem properties via direct processing (2)(e.g., photosynthesis, trophic interactions) and by altering other interactive controls: 3a – limiting resources, 3b – disturbance regime, and 3c – “modulators” such as temperature.
3a: water; plants differ in rooting depths? Differences in water use efficiency influence water available for run-off and transfer of water from soil to atmos.?
3b. Species differ in flammability
3c. Moss cover in boreal forests insulate soil from warm summer air temp; keep soil temp low; cold anaerobic soils with reduced decomposition; enhance peat formation, tie up nutrients. influence permafrost?
Effect and respons groups
Chapin et al. 2000

19. Species effects are an important interactive control
Affect most ecosystem processes

20. 1. Species effects on resource supply:
Invasion of exotic N fixer augments N cycling
Myrica faya is a N-fixing exotic tree in Hawaii

21. Deep-rooted species access more resources Enhanced NPP
Alters ecosystem structure and functioning
Native perennial bunch grasses of Calif. Have been replaced either by European annual grasses or by deep-rooted Eucalyptus trees that can access more water and nutrients

22. Deep-rooted species access more water
Augments water available to support NPP

23. Relative growth rate is key trait with strong ecosystem impacts
Determines NPP
Influences nutrient requirement and litter quality

24. Plant species differ predictably in litter quality
High-resource-adapted leaves decompose quickly
Enhance nutrient cycling rates

25. Species effects on nitrogen mineralization
Associated with differences in litter quality
Agrostis scabra (As)
Agroyron repens
Poa pratensis
Schizachyrium scoparium
Andropogon gerardii
12.5

26. 2. Species effects on climate
a. in tropical forests
Climate changes predicted for the Amazon Basin if rain forests were replaced by pasture.

27. 2. Species effects on climate
b. in boreal forest

28. 3. Species effects on disturbance
a. Many animals are ecosystem engineers
Soil disturbance (worms, gophers, ants)
Landscape disturbance (beavers)
Harvester ant
mound

29. 3. Species effects on disturbance
b. Plants influence disturbance
Decrease: Stabilize soils (e.g., sand dunes)
Increase: Fire probability

30. Linked response and effect? Species effects on succession

31. Boreal conifer forests are born to burn
After fire are replaced by less flammable deciduous forests
(effect and response functional groups differ)

32. Fire in California chaparral (effect and response groups the same)

33. Fire in Hawaiian woodlands (effects of invasive grasses)
- Schizachrium scoparium is an invasive grass that both promotes fire and resprouts quickly after burning.
- Effect and response groups are the same  positive feedback.
- Native Hawaiian shrubs and trees are not adapted to frequent fire and are eliminated.

34. III. Effects of species diversity
A. Magnitudes of processes
Enhance efficiency of resource use
Primary productivity
Mechanisms
B. Stability of ecosystem processes
C. Synthesis

35. Efficiency of resource capture/retention
- greater plant species richness led to lower pool sizes of available N
- from greater plant uptake?
12.8
Hooper & Vitousek 1997

36. 2. Responses of Primary Productivity to Changing Plant Diversity
Tilman et al. 1996
Hector et al. 2001
A number of experiments
debate about both pattern and mechanism
particularly, degree of comp vs. sampling effect
define
yr)
Hooper and Vitousek 1997
Figure from Inchausti 2001

37. 3. Mechanisms of diversity effects
Complementarity - niche differentiation that leads to greater overall resource use in more diverse communities.
My initial results seemed to indicate that compositional effects outweighed complementarity effects in productivity and nutrient retention. But I wanted to revisit the question of complementarity in more depth, for a couple of reasons.

38. Complementarity in plants with strong functional differences
(Gulmon et al. 1983)
Rooting depth E L
(Vandermeer 1990)
Light interception
First I had assigned functional groups based on strong differences among species in phenology, rooting depth and other traits that I would expect would lead to complementarity.
Opportunities for complementarity among plants in terms of “feeding niches” seem fewer than perhaps for animals - all plants depend on water, light, CO2 and the same suite of mineral nutrients for growth.
But can have spatial and temporal separation of maximum demand.
Examples from intercropping and serpentine grassland.
Also nitrogen type (NO3, NH4, DON) as seen in some Arctic tundra species.

39. 3. Mechanisms of diversity effects
Complementarity - niche differentiation that leads to greater overall resource use in more diverse communities.
Sampling - statistical probability of choosing a highly productive species.
My initial results seemed to indicate that compositional effects outweighed complementarity effects in productivity and nutrient retention. But I wanted to revisit the question of complementarity in more depth, for a couple of reasons.

40. Detecting complementarity
Sampling for dominant
Complementarity
Tilman et al. 1997

41. NO comp.
General trend
Again significant diffs among SFG’s, P’s highest, E’s, N’s lowest. Important for understanding effects later.
but note that not all mixtures have L’s, the most prod. monoculture

42. B. Stability of ecosystem properties 1. Different kinds of stability
a. Resistance
b. Resilience
2. Mechanisms of diversity effects
a. Compensation
12.2
Species richness
Process rate

43. Response variation in species leads to less variation in ecosystems
Portfolio effect
Too technical?
Cottingham et al. 2001

44. Many species with a continuum of trait differences can lead to compensation.
12.9
There may be little compensation for species with very distinct functional roles (e.g., keystone species)
12.2

45. B.3. Experimental tests of diversity effects on stability of ecosystem properties
Note experimental difficulties
12.10
What else could cause this pattern?

46. Microbial diversity decreases ecosystem variability
Focus on “supporting” services
That’s fine in a microcosm, what about in the real world?
McGrady-Steed et al. 1997

47. Report Warns of ‘Global Collapse’ of Fishing By CORNELIA DEAN Published: November 2, 2006
(Worm et al Science)
Extinction
Collapse
A paper by Boris Worm and colleagues in the journal Science got a lot of press last fall
If you extrapolate this line down, you get to all fisheries collapsed by about 2048 – assuming we keep doing just what we’re doing now.
Inset shows how collapses correlate with species richness in various regions of the world. Note that this is correlation, not causation!
One implication is that less diverse systems less resistant to the disturbance imposed by harvest, and therefore less able to provide food in the long term.
SYMBOLS???

48. Correlated response and effect traits: large ecosystem change
Land use change and pollinator loss: effects on pollination efficiency
Different response groups
Suding et al. 2008
(data from Larsen et al. 2005)

49. C. Synthesis of diversity effects
Figure from Field 1996
One year/one site
Zone accessible to intensive management
+ site to site variation
+ year to year variation
+ different successional stages
Without knowledge of exact functional roles

50. Summary
Differences in species functional traits can influence ecosystem properties (effect and response groups)
Direct effects and effects on interactive controls (climate, disturbance, resource availability)
Diversity effects
Magnitudes of processes
Stability of processes
Understanding mechanisms needs critical evaluation of alternative hypotheses.