Ecosystem Ecology I. Introduction II. Energy Flow III. Biogeochemical Cycles

Ecosystem Ecology III. Productivity, Diversity, and Stability

A. Productivity

1. Gross Primary Productivity

Total photosynthetic productivity;

CO2 + H20 -----> Glucose + O2

A. Productivity

2. Net Primary Productivity

NPP = GPP - respiration

(Plants use some of the energy they absorb; it is not stored as biomass. NPP is only the amount stored as new biomass.)

B. Diversity - Relationships with Productivity

1. Productivity increases diversity

- QUANTITATIVE EFFECT

If you have more productivity at the base of a food web, then you can build a longer food chain (adding additional levels AND species)…. And then get keystone effects.



- QUALITATIVE EFFECT

An increase in productivity may also occur because more types of food have been added. This may allow for more specialization at the next trophic level - and the coexistence of more species.





2. Diversity increases productivity

- Sampling Effects

More diverse communities are more likely to contain the most productive species, and thus raise the total productivity.

- Niche Complementarity

More diverse communities are more likely to contain different types of species that use different types of energy... thus more efficiently harvesting the available energy

Monoculture

They all need the same things at the same concentrations; have to place them far apart to reduce competition.

Polyculture

Combinations of different plants can be planted at higher density, and they use different "niches" and coexist. Even if abundance of "most productive" species, drops, this loss can be offset.

- Positive Interactions

More diverse communities may contain species that benefit other species, and thus increase the productivity of the whole community

Monoculture

They all need the same things at the same concentrations; have to place them far apart to reduce competition.

Polyculture

Nitrogen fixing legumes (beans) nutrify the soil, increasing the growth of other plants

without beans

with beans

Diversity and Productivity in a Long-Term Grassland Experiment Tilman, et al. 2001. Science 294. 843 - 845

Cedar Creek Ecosystem Science Reserve

- 168 9 m x 9 m plots - 1, 2, 4, 8, or 16 species randomly chosen from a pool of 18 species: 4 species, each, of C4 grasses, C3 grasses, legumes, non-legume forbs; 2 species of woody plants. - ~35 replicates of each treatment


Dotted line is biomass in a monoculture of the most productive species. Higher productivity than this, at higher richness values, means niche complementarity or positive effects must be occurring.



So, many random assemblages of multiple species have biomass above that of the most abundant monoculture (can’t just be sampling effect).



So, many random assemblages of multiple species have biomass above that of the most abundant monoculture.

And we might expect greater niche complementarity in natural systems…

Additional Experiments and Results:

- Foliar fungal disease incidence decreased at higher diversity because of greater distance between individuals of a species, and resultant lower rates of disease spread (Mitchell et al. 2002). (“Dilution Effect”)

- Greater plant diversity led to greater abundance and diversity of herbivorous insects, and this effect continued up the food web to predator and parasitoid insects (Haddad et al. 2001). (“Qualitative Effects of Diversity”)


- Fewer novel plant species invaded higher diversity treatments because of their lower soil NO3 levels, greater neighborhood crowding and competition, and greater chance that functionally similar species would occur in a given neighborhood (Figs 3; Naeem et al. 2000, Kennedy et al. 2002, Fargione et al. 2003, Fargione and Tilman 2005a, 2005b).

Greater plant species numbers led to greater ecosystem stability (lower year-to-year variation in total plant biomass) but to lower species stability (greater year-to-year variation in abundances of individual species), with the stabilizing effect of diversity mainly attributable to statistical averaging effects and overyielding effects (Fig 4; Tilman et al, submitted). Data gathered this past field season shows that soil total C has now become an increasing function of plant species numbers (Fig 5).


- Greater plant species numbers led to greater ecosystem stability (lower year-to-year variation in total plant biomass) but to lower species stability (greater year-to-year variation in abundances of individual species).


- Stored soil carbon increases with diversity.

- Effects of Genetic Diversity

Example Crutsinger, et al. 2006. Science 313: 966-968.

Methods:

- 63 1m2 plots, each containing 12 plants of all goldenrod.

- The plants in a plot represent either 1, 3, 6, or 12 genotypes, randomly selected from a pool of 21 genotypes.

- Example Crutsinger, et al. 2006. Science 313: 966-968.

Results:

1: ANPP correlated with number of genotypes in plot.


Results:

1: ANPP correlated with number of genotypes in plot.

2: Total insect species diversity, and diversity of herbivores and predators, correlate with ANPP and number of genotypes per plot.


Results:

4: ANPP increase is NOT due to a sampling effect. Evidence favors niche complementation (p = 0.07).


Results:

5: Increase in herbivorous insects due to both MORE food (ANPP - quantitative effect) and DIFFERENT food (niche differentiation - qualitative effect).


Results:

6: Increase in predator richness due to increase in herbivore richness, not AMOUNT of food.

Some herbivores were only associated with some genotypes.


Conclusions:

ANPP increased with genetic diversity, probably as a function of niche complementarity.


Conclusions:


Diversity in higher trophic levels increased with increased ANPP and greater genetic diversity. Herbivore richness is a function of both increased abundance and niche complementarity. Predators increase largely due to a greater variety of herbivores.


Conclusions:


Diversity in higher trophic levels increased with increased ANPP and greater genetic diversity. Herbivore richness is a function of both increased abundance and niche complementarity. Predators increase largely due to a greater variety of herbivores.

So, genetic variation WITHIN species, and not just diversity among species, may be critical to the conservation of productive and species-rich communities.

C. Effects on Stability


1. Types

- "resistance to change"

- "resilience after change"


1. Types

2. Relationships with diversity

- more diverse communities are less susceptible to single "types of disturbance" - (a pest, a flood, a drought) - because the many species are unlikely to be sensitive to the same thing.


Biodiversity and Ecosystem Functioning: Current Knowledge and Future Challenges. Loreau, et al. 2001. Science 294: 804 - 808

As richness increases, productivity become less variable (more stable).

C. Stability

1. Types

2. Relationships with diversity

- diverse communities may recover more rapidly, too (resilience).... but they may not.

Fisheries ... yes

Rain forest... maybe not

Decomposition rapid

Absorption rapid

Volatiles released

Stimulate condensation and precipitation

Rainforests feed themselves and water themselves.

CUT FOREST DOWN

Nutrient runoff… then reduced rainfall

INCREASE FIRE

Select for fire-adapted grasses.... rainforest doesn't come back....

RAINFOREST

(wet, few fires)

GRASSLAND

(dry, many fires)

"Multiple Stable States"

We are dependent on the environment for food and resources. Ideally, we would like a STABLE, PRODUCTIVE supply of these resources.... right??

FEAST

FAMINE

(We don't want "boom and bust", "feast and famine" scenarios....)

FEAST

FAMINE

We are dependent on the environment for food and resources. Ideally, we would like a STABLE, PRODUCTIVE supply of these resources.... right??

(We don't want "boom and bust", "feast and famine" scenarios....)

STABILITY

PRODUCTIVITY?

We are playing jenga with our life support systems...

de Ruiter et al. 2005. Food Web Ecology: Playing Jenga and Beyond Science 309:68 - 71

Simple

Predictable

Realistic?

Realistic

Complex

Predictable?

But what else does biodiversity

do??

2) Biodiversity improves ecosystem services

Estimates of various Ecosystem Services - $U.S. trillionsEcosystem services

Value(trillion $US)

Soil formation 17.1Recreation 3.0Nutrient cycling 2.3Water regulation and supply

2.3

Climate regulation (temperature and precipitation)

1.8

Habitat 1.4Flood and storm protection

1.1

Food and raw materials production

0.8

Genetic resources 0.8Atmospheric gas balance 0.7Pollination 0.4All other services 1.6Total value of ecosystem services

33.3

Source: Adapted from R. Costanza et al., “The Value of the World’s Ecosystem Services and Natural Capital,” Nature, Vol. 387 (1997), p. 256, Table 2. TOTAL GLOBAL GNP (1997) = 18 trillion.

GLOBAL GDP 2011: $75 trillion

GLOBAL GDP 2011: $75 trillion

Based on different criteria, this is the ecosystem value we lost in that 14 year span.

3) Aesthetics and Inspiration: Biodiversity enriches our cultures

Lyme Disease:

- fragmentation reduces patch size - abundance of predators like fox declined - white-footed mice (host of Borrela burgdorferi bacterium) increase. - increase host density, increase infection rate of ticks.

4) Fights Disease

West Nile Virus

Swaddle and Carlos, 2008. PLoS one 3:e2488

Low Diversity: High Relative Abundance of

Hosts

High Diversity: Low Relative Abundance of

Hosts

How is our biodiversity doing?

Genetic diversity within species

Species diversity in communities

Ecosystem diversity

How is our biodiversity doing? Humans used hundreds of crop species worldwide; now 3 species (rice, wheat, corn) provide 60% of our calories from crop plants.

According to the FAO of the UN, 70% of the genetic diversity of crop plants has been lost in the last 75 years as we’ve shifted to industrial farming and the use of GM strains.


2000 Pacific Island bird species (15% of global total) have gone extinct after human colonization

20 of the 297 mussel species in N.A. have gone extinct in the last 100 years; 60% are endangered

40 of 950 fish species in N. A. have gone extinct in the last century; 35% are threatened or endangered

http://www.americanscientist.org/issues/pub/the-real-biodiversity-crisis/1

http://www.nps.gov/sacn/planyourvisit/st-croix-currents.htm?customel_dataPageID_206517=289024

http://www.fishdecoys.net/pages/LDC_Collection/BenzieJoDecoys.htm

Yellow-finned cutthroat trout


1 in 4 mammal species is endangered

1 in 8 bird species is endangered

1 in 3 amphibian species is endangered

48% of primate species are threatened

Data from: http://iucn.org/what/tpas/biodiversity/


35% of mangrove habitat has been lost in the last 20 years

In the Caribbean, hard coral cover has declined from 50% to 10% in the last 20 years

Since 2000, 232,000 sq miles of old growth forest have been lost (size of Texas).

7 billion in 2011 (12 years later)

http://news.mongabay.com/2011/1009-amazon_deforestation_revised.html

13,000 sq kilometers is about the size of Connecticut

http://mvh.sr.unh.edu/mvhinvestigations/old_growth_forests.htm

Extent of Virgin Forest, Contiguous U. S.

Millenium Assessment 2006

1

10 million?

Humans use/control 40% of the ‘food’ produced on the planet.

Habitat loss, Fragmentation, Climate Change

PLANTS

HERBIVORES

CARNIVORES

LARGE AREA OF HABITAT

Area Effects

Fragmentation

HABITAT FRAGMENTATION

Fragmentation

HABITAT FRAGMENTATION

Fragmentation

1)Carnivores lost - (reduce diversity)2)Herbivores compete – (reduce diversity)3)Plants overgrazed – (reduce diversity)

We are a geological force, operating on an ecological timescale

Mountaintop removal in West Virginia


Gold mining in Peruvian Amazon

All genera

“well described” genera

The “big five” Mass Extinction Events

http://en.wikipedia.org/wiki/File:Phanerozoic_biodiversity_blank_01.png

Millions of Years Ago

Th

ou

san

ds

of

Gen

era

Sixth major mass extinction event - NOW

22 May 2010 –Secretary-General Ban Ki-moon:

“Biodiversity loss is moving ecological systems ever closer to a tipping point beyond which they will no longer be able to fulfill their vital functions.”

What Can We Do?

We need to protect and preserve large intact, biodiverse ecosystems.

This is great, but it ain’t gonna do it…

We need to rethink our model of community…

Development

nature

nature

Development

Development

Development

We need to find out what’s out there!

We need to appreciate the societal and economic value of biodiversity

Corporate Social Responsibility (CSR)http://www.justmeans.com/Stop-Loss-CSR-Biodiversity/28856.html

“Protection of biodiversity should be the underlying reason for every CSR effort. Biodiversity loss is the most severe threat to human-wellbeing on the planet. It rates even higher than climate change and related problems….

The head of Deutsche Bank's Global Markets predicts that our current rate of biodiversity loss could see 6% of global GDP wiped out as early as 2050.

The Economics of Ecosystems and Biodiversity executive summary (2010) reports that “over 50% of CEOs surveyed in Latin America and 45% in Africa see declines in biodiversity as a challenge to business growth. In contrast, less than 20% of their counterparts in Western Europe share such concerns”

If we recognize the grandeur of life, we might appreciate it…

If we appreciate it, we might value it…

If we value it, we might sustain it…

If we sustain it, we might be able to sustain our societies and economies, as well.

ECONOMY

SOCIETY

ENVIRONMENT

If we don’t, we won’t…

A few extinct animal species.

Thylacine - 1936

Quogga - 1883

Golden Toad - 1989

Tecopa Pupfish - 1981

Yangtze River Dolphin - 2006

Vietnamese Rhinoceros - 2010

We abuse land because we regard it as a commodity belonging to us. When we see land as a community to which we belong, we may begin to use it with love and respect.” – Aldo Leopold - 1949

“The last word in ignorance is the man who says of an animal or plant, “What good is it?” If the land mechanism as a whole is good, then every part is good, whether we understand it or not. If the biota, in the course of aeons, has built something we like but do not understand, then who but a fool would discard seemingly useless parts? To keep every cog and wheel is the first precaution of intelligent tinkering.”

Ecosystem Ecology I. Introduction II. Energy Flow III. Biogeochemical Cycles

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