Ecology Comprehensive Final Exam (lect 20-end)

Total production of plant tissues

a low availability of soil nitrogen reduces net primary production as well as the nitrogen contentration of the plant tissues produced.

Resistance:

capacity of a community to maintain structure in face of disturbance -will not experience much change -it is resistant to disturbance in ecological change

Resilience:

capacity to recover to its former state after disturbance

Why does there appear to be a dead zone at the mouth of the Mississippi river?

caused by excess N from farm runoff, which increases the Gulf of Mexico marine productivity Nitrogen is the main nutrient used in fertilizers on terrestrial lands; runoff leads to algal blooms, when this algae dies many organisms feed on it and in doing so they deplete the oxygen in the system, creating a dead zone.

The highest rates of marine primary production occur in ____________: nutrients from land surface, upwelling.

coastal water

Actual Evapotranspiration: cold, dry ecosystems tend to have _____ AET; while warm and humid ones tend to have _____ AET.

cold, dry = low AET warm, humid = high AET

Ways we define communities. Ways we define ecosystems.

communities = composition, abundance, and diversity ecosystems = productivity, nutrient availability

The rate of _____________ is influenced by temperature, moisture, and chemical composition of both detritus and the environment.

decomposition

What is the primary way for nutrients to be returned to an ecosystem and become available again?

decomposition

With the exception of moisture, the same factors-leaf species, temperature, and nutrients-control ___________ in aquatic environments.

decomposition

______________ releases nutrients from dead organic matter.

decomposition

net mineralization rate

decomposition determines rate of transformation of organic nutrients into organic form

The __________ phosphorus atmospheric pools are in mineral deposits and marine sediments.

largest

"Climax community": Characteristics?

late successional community that remains stable until disrupted by disturbance slow growing, long lived, large, slow dispersal, low r -dominated by k or competitive species -bad dispersers, good competitors -continue indefinately

______ and ________ is dependent on whether or not stability exists.

spacial and temporal time scale.

Webster suggested that rather than a stationary cycle, stream nutrient dynamics are better represented by a _______.

spiral

Ecological succession starts w/ _______ communities, followed by a ______ community.

starts w/ pioneer community, followed by climax community

In the 1960's-70's there was a battle between detergent industry and scientists. What was it?

which element limited Aquatic primary production? Carbon or Phosphorous? -ecologists say P -detergent scientists say C

What does the loss of energy as energy is transferred from one trophic level to the next cause?

trophic pyramid of energy distribution and production

What are some of the highest areal production rates for terrestrial primary production? (biomes)

tropical forest (40.8 Pg C yr^-1), Tropical savannah and grassland (31.3) and Croplands (14.8). these have warm conditions with high water availability

P can be important in some parts of ocean:

unpolluted coastal zones and open ocean

In looking at evidence of stability, unstable ______ is a key parameter.

unstable temps = key parameter

_______ ________ (nutrients) can also impact primary production rates.

Soil Fertility

Energy flow in a temperature deciduous forest: of total solar energy coming in, how much is unavailable for use by second trophic level?

99%

Rate of primary production

=amount of energy fixed per area per time eg. kg/m2/yr

______ are largest pool of actively cycled C:

Oceans - about 70%

T or F. Invasive plants can substantially alter the nutrient dynamics of ecosystems?

TRUE

________ annual temps mean longer period when photosynthesis is possible.

Warmer

Nutrient cycling is controlled in part by __________________.

decomposition

Serengeti primary production: What effect does grazing have on primary production? Explain the mechanisms (4).

Plant consumption by grazers stimulates increased plant growth rate and therefore increased primary production. Green biomass increases on grazed areas but decreases on ungrazed areas. Mechanisms: 1) compensatory plant growth 2) lower biomass=lower respiration rate, more energy towards growth and productivity 3) reduced leaf area=reduced self-shading and improved water balance 4) reduced competition between plants for sunlight and nutrients

Once fixed, nitrogen becomes _________ to other organisms.

available

Species richness increases through out succession - ______ at first, then ____.

fast at first, then slower

What actually might be happening with mechanisms of succession; inhibition and facilitation in

intertidal zones

Physical retention

involves storage in wood detritus such as logs and snags, in debris caught in pools behind logs and boulders, in sediments, and in patches of aquatic vegetation

The conversion of organic to inorganic forms, driven by decomposition of bacteria, fungi, animal detrivores is called _______.

mineralization

Justus Liebig's "Law of _______" says what?

minimum; productivity will be limited by the nutrient in shortest supply

An important driver of decomposition rates?

moisture availability positive relationship

Higher rates of cycling in

more fertile systems

Plants in low-nutrient ecosystems tend to grow ________ to decrease their nutrient demand and allocate more resources to roots to access nutrients in the soil.

more slowly

Nutrient Fluxes

movement of nutrients among compartments

Nutrient Spiraling

in flowing-water ecosystems, the combined processes of nutrient cycling and downstream transport

Changing ecosystem properties during succession:

increase biomass, increase community respiration, increase PP, increase soil depth, and decrease stream spiraling lengths

Terrestrial NPP _________ with increases AET.

increases

Ecosystem changes during succession include _________, ___________, _________, and nutrient retention.

increases in biomass, primary production, respiration

Bottom-up controls -what is it? -provide an example -what is the primary control of primary productivity?

influences of physical and chemical factors in the environment, e.g., the influence of phosphorus and nitrogen in aquatic environments nutrients are the primary control of primary productivity

____________ carbon compounds play a large role in global climate (CO2, CH4).

inorganic

*Stability - fact or fiction?* Stability is the _______ of an ecological community over time (in the face of disturbance)

persistence

Marine sediments that contain ____________ turn into sedimentary rock that is uplifted, closing the cycle over geological time scales.

phosphorous

How does phosphorous differ from carbon and nitrogen?

phosphorous does not have a large atmospheric pool

C enters ecosystems through _____________, and leaves through __________.

photosynthesis; respiration

In deep aquatic systems, the two zones are _______ separated.

physically

Estuary

place where freshwater joins saltwater

In terrestrial systems, the two zones are linked directly by ____ ______. (same in shallow aquatic systems)

plant tissues

_____ and ____ can modify the distribution and cycling of nutrients in ecosystems.

plants and animals

Total number of plant species is increased with what?

plot age

Trophic level

position in a food chain or food web, in terms of the number of transfers beyond primary producers

Higher _________ allows plants to.......

precip; allows plants to keep stomata open longer

*Consumer Control of Primary Production* Primary Production can also be controlled by top-down (biotic) processes. Examples?

predation, grazing

Rates of Nutrient Cycling: internal nutrient cycling depends on _______ ______ (uptake) and ________ (mineralization)

primary production and decomposition

Nutrient Uptake

primary productivity determines the rate of nutrient transfer from inorganic to organic form

Ecosystems follow _________ sequence.

seccessional. -sequence of community and ecosystem succession is NOT random

Nutrient pools:

the nutrients contained in ecosystem compartment

Plants and the nutrient dynamics of ecosystems: Plants can influence ecosystem nutrient dynamics by various ways. Name some.

-differences in plant species traits like nutrient uptake, allocation, and loss affect nutrient cycling

What is the "depth where photosynthesis exceeds respiration" called?

*compensation depth*

Another study in intertidal zone showed that

*facilitation can be important factor in intertidal community succession* -Oregan coast -late successional dominant was a flowering plant that Phylostat. that disperses using seeds. Seeds have barbed endings that entangle it in seaweeds to help it sprout w/ something to attach to. -Looked at how algae affects abundance of this plant -Control w/ algae undisturbed -Removal of algae plot looked at number of seeds present and seedlings that hatched. presence of algae (intermediate succession) increased number of seeds and adults. Later successional species was increased and facilitated.

Organisms and nutrient cycles: *invasive species*: Introduced organisms can affect nutrient dynamics. -Myrica faya: introduced N fixer in Hawaii

*increases N inputs to ecosystem, increased leaf litter N content, increased decomposition rates*

An example of ecosystem changes during succession in Glacier Bay:

*soil characteristics* increased organic content, increased moisture, increased soil depth. Changes in N&P conc. -Large increase in N -P drops off

What is primary production?

- fixation of energy by autotrophs (plants) in an ecosystem -where photoautotrophs use sun's energy to fix inorganic carbon

As in terrestrial ecosystems, litter chemistry and nutrient availability in the environment affect decomposition rates in aquatic ecosystems. Name 3 studies/patterns that emphasize the role played by the physical and chemical environment in the process of decomposition.

-*leaves with higher lignin content decomposed at slower rate. b/c high lignin inhibits colonization of leaves by fungi.* -*leaves decayed faster (had higher k) in streams with higher concentrations of nitrates.* -*leaf decomposition rates increased rapidly as phosphorous concentration increased. Rate then leveled off at higher concentrations of phosphorous*

Animal diversity follows a similar pattern (ex w/ birds)

-20 acre study sites ranging in successional ages 1-150yrs. vegetation ranging from grassland to mature oak-hickory forest. -almost parallel to that of woody plant diversity

Experiment on hawaiin islands looking at how soils can change over longer time scales:

-Chronological sequence experiment: looked at total organic carbon -all plots were similiar elevation, similar temp, so changes could be attributed to succession -Increased C and N in soil followed by drop off in old soils

How did they test this?

-D. Schindler and co-workers- whole lake fertilization experiments at ELA [separate lake w/ curtain. C&N on one side. C,N,&P on the other. If it was C, PP would increase where C was added. If phosphorous, pp would increase where P was added]

Productivity changes in flood disturbance

-Gross PP: fast increase followed by stabilization. -all have similar pattern; initial fast recovery followed by leveling off

In hawaiin nitrogen enrichment experiment, they compared Myrica to a native tree, Metrosideos.

-Myrica leaf tissues had higher concentration -higher nitrogen content of the leaves associated with higher rate of decomposition and greater nitrogen release during decomposition. -*Result is increased nitrogen content in the soils associated with Myrica*

In fertilization experiments looking at terrestrial PP and nutrient availability, what did they find?

-N tends to be nutrient in shortest supply -looked at fertilization in wet and dry alpine ecosystems; 3 exp plots; monitored NPP over time; found that wet meadows have higher nutrient availability & similar responses in each system. -*N+P stimulates greatest increase*

In studies of natural ecosystems looking at terrestrial PP and nutrient availability, what did they find?

-NPP of forests and Nitrogen mineralization

In Aquatic Primary Production in Marine Systems, what are the main limited nutrients in many ocean habitats?

-Nitrogen and Iron (N and Fe)

Nutrient (N) retention follows a slightly different path in flood disturbance:

-Nitrogen retention (amt of N kept inside stream) -if N conc are lower at downstream, some of the N was taken up and retained in plant and biomass. -If N conc are higher downstream, system is exporting N. -in early stages, as plant biomass builds up, N retention increases -after about 3 months, N is being exported (not clear why)

Ecosystem changes during succession in Glacier bay resulted in a large increase in Nitrogen, but drops off off in Phosphorous. Why?

-Phosphorous gets entered in through weathering of rocks. As time goes on, P gets weathered, leeched, and escapes the ecosystem so quantities decline.

Trophic cascade

-S. Carpenter: potential primary production in lakes determined by nutrients, actual production can be controlled by fish-propagation of indirect consumer effects influences of consumers on abundance of organisms in lower trophic levels (at least 1 level below) (include indirect effects), particularly primary producers

Changes in P concentration in hawaiin island experiments:

-Young sites have lots of weatherable P that can be taken up by plants. As time goes on, this decreases -As Nitrogen conc increases, the rate of N loss also increases. P decreases because it escapes from the system and ecosystem becomes more limited.

Community changes during succession: Secondary succession in Temperate Forests

-abandoned fields in N. Carolina created patches of various ages interspersed with areas of undisturbed forest -first species to colonize = crabgrass, ragweed, asters. -early establishment of pine canopy forms in ~10-20 years. Pine cannot grow in shade, but decidious trees can so -40 -50 yr old pine forests have well-developed understory of young deciduous trees like oak and hickory. -they become dominate and pines decline to few & scattered.

Net primary Production

-amount of C left once autotrophs met own metabolic needs -he amount of energy left over after autotrophs have met their metabolic (including respiration) needs = accumulated biomass (leaves, branches, roots, etc.) available for consumption by other organisms

Nutrient cycling

-an essential process in all ecosystems and represents a direct (cyclic) link between NPP and decomposition. -Pathway of an element or nutrient through the ecosystem, from assimilation by organisms to release by decomposition.

Example with invasive species:

-an invading nitrogen-fixing tree, Myrica Faya, altered nitrogen dynamics of ecosystems in hawaii. -was planted for watershed reclamation; now has quickly spread -*has potential to modify nutrient dynamics of hawaiin ecosystems because it maintains a mutualistic relationship with a nitrogen-fixing fungus* -measured rate at which species adds nitrogen to ecosystem -found it was largest source of nitrogen input to ecosystem

Why does primary production rates tend to decrease as you go deeper into water?

-b/c light decreases as you go deeper

Secondary succession on the Piedmont Plateau. Number of wood plant species increased. -As in Glacier Bay, plant species diversity in abandoned fields increases during succession

-began with single species of woody plant invading soon after fields were abandoned and began to level off at 50-60 species after about 150 years. -this increase in species richness follows a logarithmic pattern like the one in Glacier Bay

When studying ecosystem ecology, ecologists look at

-biotic + interactions -abiotic + structure -energy movement -movement/cycling of nutrients

Community changes during succession: Succession in Rocky intertidal communities W. Sousa studied disturbance and succession in intertidal communities: What is the sequence and pattern of succession on rocky substrates?

-cleared boulders of their cover of attached organisms and monitored succession in new, freed up patches -a change from pioneer species to late succession species; increase in diversity -Note: Similar as forest succession. average species increased until about 1-1.5 yrs here then leveled off at about 5 species, but glacier bay was about 1500 yrs and Piedmont Plateau was about 150.

Hypolimnion

-deep water. cold and relatively low in oxygen -cold, oxygen-poor zone of a lake, below the thermocline.

Inhibition:

-early colonists inhibit establishment of later colonists. -they try to dominate the system and actively inhibit colonization of later species

Rapid recovery of primary producer biomass, productivity and ecosystem respiration

-ecosystem recovery following large flood -chlorophyl benthic levels changing following disturbance -as time goes on after flooding, biomass increases quickly at first then levels off about 30 days after flood

Phosphorous

-essential element for living systems; ATP, DNA/RNA, phosphlipids -not very abundant in biosphere

*Ecosystem changes during succession* How soils can change over longer time scales:

-ex = islands of hawaii lava; lava flow of different ages underlying the islands -succession happening over longer periods with some young and some old lava substrates on different islands

Describe the experiment in three lakes to display the increase/decrease in phytoplankton biomass

-experiment in 3 lakes: 2 manipulated (A&B), 1 as control (C) -removed bass from lake A, added to B -removed minnows from B, added to A

Example of decomposition in aquatic ecosystems?

-found that chemical composition of litter highly influences rates of decomposition -study looked at influence of litter chemistry on rate of leaf decomposition. included leaves of different tree species -results: leaves with higher lignin content decomposed at slower rate. b/c high lignin inhibits colonization of leaves by fungi.

Community changes during succession: Primary succession at Glacier Bay

-glacier in glacier bay (alaska) retreating for >250 years -opportunity to study primary succession on newly exposed substrates -pioneer community (10-20 years): herbs and low shrubs -~40 years: alder thickets with willows, poplars, spruce -~100 years: spruce dominates, hemlock appears -~200 years+: hemlock dominate starts out with pioneer community like shrubs and over time a climax community of hemlock

Turnover

-if surface waters become cooler than the deeper waters, they begin to sink, displacing deep waters to the surface -vertical mixing of layers in a body of water, brought about by seasonal changes in temp.

Benthic Zone

-in deeper water, the zones of decomposition in the bottom sediments and waters are physically separated from the surface waters, where temps and light availability support primary productivity. -the area of the sea bottom.

Evidence of Stability? -are meadow communities stable over tens of year? -Park grass results suggest that answer may depend on scale at which you ask question..

-looked at proportion of grass, legumes, and other species. plots that received fertilizer and plots that didn't -fluctuation happens but relative abundances are fairly similar - there is some variation but the relative abundances are possible evidence for stability -individual species behave different: some continuous. some increased through time. Different grass species had different patterns of behavior. This tell us lack of stability in different species doing different things during this period.

Disturbance and nutrient cycles: Hubbard brook watershed: clear cutting increased nutrient export

-measured how nutrient dynamics of stream ecosystems respond to variations in streamflow. -studied phosphorous dynamics -measured inputs and storage of Phosphorous.

Tolerance: (the intermediate)

-more neutral -all species can become established at a location at all stages of succession -life history is what shapes succession -early = more abundant -as time progresses, later successional species outcompete early colonists. *later eventually oucompetes early colonists. No facilitation or inhibition present*

What are 4 terms w/ nutrient cycling in ecosystems?

-nutrient pools -nutrient fluxes -nutrient sinks -nutrient sources

Epilimnion

-or surface water, is relatively warm because of the interception of solar radiation -warm, oxygen-rich upper layer of water in a lake or other body of water, usually seasonal.

Ecosystem changes during succession: Ecosystem changes at Glacier Bay

-succession involves change in ecosystem characteristics -total soild depth and depth of all major soil horizons show significant increases from pioneer community to spruce stage

Third example of decomposition in aquatic ecosystems. Draining a tropical rainforest in costa rica

-placed leaves of a tree common to central america at 16 stream sites that varied greatly in phosphorous concentration.

Another example of decomposition in aquatic ecosystems? How nutrient content of stream water can also influence rate of decomposition?

-placed yellow poplar leaves in several temperate zone streams differing in water chemistry. -yellow poplar leaves decomposte faster in streams with higher nitrate content. -"k" used as index of decay rate; found that k varied significantly in different streams -*leaves decayed faster (had higher k) in streams with higher concentrations of nitrates.*

Why was the idea that phosphorous plays a dominant role in fresh water aquatic ecosystems controversial?

-scientists in the detergent industry were saying phosphorous was not a driver of poor water quality. they believed it was carbon -ecologists said that excessive nutrient loading was leading to water quality issues b/c of source from detergents

Factors affecting NPP are variable. They include

-seasonable -longer time scales -w/in seasons

Study that looked at successional changes in species diversity and composition in Glacier bay

-sites with similar physical features but differing ages -all sites on material deposited by a glacier -ranged in ages of 10 to 1,500 years since glacial retreat

Succession in intertidal zone example

-studies of benthic algae in rocky intertidal show inhibition can be important -how early colonists affect succession: inhibit late successional species, but more vulnerable to stress -removed Ulva and looked at how a middle successional species is affected by presence or removal of Ulva -Control: -Exp: *this example is inhibition*

Gross Primary Production

-total amount of C fixed (gross - plants own needs = net pp) -the total amount of energy fixed by autotrophs, including net primary production and respiration

Thermocline

-transition zone between the surface and deep waters. characterized by a steep temp gradient. -layer in a thermally stratified body of water in which temp changes rapidly relative to the remainder of the body.

Evidence of Stability What about thousands of years?

-tree history in central MN -forests at different time periods have gone through large changes. from pine dominated to oak domiated to birch dominated, etc.

Global patterns of marine primary production: Name 3 things that make continental margins high in nutrients and therefore foster regions of high primary production by marine phytoplankton.

1) nutrient run-off from land (rivers) 2) sediment disturbance 3) ocean current upwelling zones bring nutrients to surface waters (e.g., california currents)

What are 4 mechanisms of energy loss exhibited through trophic levels?

1. "sloppy feeding" 2. limited assimilation (assimilation=construction of new biomass, therefore, inability of consumer to use all energy to construct new biomass) 3. consumer respiration (lose energy to ecosystem) 4. heat production

Mechanisms of Succession: What are 3 potential competing mechanisms?

1. *Facilitation* 2. *Tolerance* 3. *inhibition*

Primary Production in aquatic environments is highest in

1. algal bed and reef 2. swamp and wetland 3. estuaries Mean NNP World NNP (g/m^2/yr) (10^9tons/yr)

Name 2 important topics in ecosystem level of organization

1. energy production and flow 2. nutrient cycling through the community

The main primary producers in aquatic habitats (from most to least important)

1. phytoplankton 2. attached (benthic) algae 3. vascular plants (macrophites)

What two abiotic factors can control terrestrial net primary production alone?

1. precipitation 2. soil fertility

How quickly material is moved downstream depends on: 1. 2.

1. water velocity 2. degree of physical and biological retention of organic matter (how much matter can the water carry?)

Name 3 Serengeti grazers

1. wildebeast 2. zebra 3. gazelles

Name: 1st trophic level 2nd trophic level 3rd trophic level 4th trophic level

1st trophic level=primary producers (plants) 2nd trophic level=primary consumers (herbivores & detritivores) 3rd trophic level=secondary consumers (carnivores that feed on primary consumers) 4th trophic level=tertiary consumers (carnivores that feed on secondary consumers)

Serengeti primary production: - How much is consumed by Serengeti grazers? - How much is controlled by grazers?

66% consumed by grazers 1% controlled by grazers

During primary succession at Glacier Bay, overall plant species diversity A) first increases rapidly, then levels off. B) increases steadily throughout succession. C) increases slowly at first, then more rapidly after a few hundred years. D) peaks at intermediate successional stages. E) decreases steadily throughout succession.

A

Joseph Connell's "intermediate disturbance hypothesis" proposes that A) species diversity is highest at intermediate frequencies of disturbance. B) species diversity is lowest at intermediate frequencies of disturbance. C) population growth rates are highest at intermediate frequencies of disturbance. D) competitive exclusion is fastest at intermediate levels of disturbance. E) None of the choices are correct.

A

On intertidal boulders in California, the diversity of diatoms and algae A) increases at first, but then declines late in succession. B) increases steadily through succession. C) increases slowly at first, but then rapidly late in succession. D) increases rapidly at first, then plateaus late in succession. E) first decreases, but later increases.

A

Preston graphed abundance of species in collections as frequency distribution and these resembled: A) bell-shaped curves B) sigmoidal tendencies C) transdential convergences

A

Upon death, nitrogen is released during decomposition as NH4+. This process is known as ____________.

Ammonification

_______ _________ ______________ captures interaction between temperature and precipitation.

Annual Actual Exapotranspiration (AET)

Evidence of Stability? Ex w/ 3 phytoplankton in lake Michigan

Are algal communities stable over a year? years? -later summer abundance increaes in cycotella. size of peaks and relative abundance is variable from year to year. -later part of summer = most abundance; may be sign of stability

Allogenic succession includes all the following changes except: A) those caused by long-term drought B) those caused by changes in soil due to plants C) those caused by introduction of exotics D) those caused by change in sea level or topography

B

Communities where small, random changes in plant numbers occur around some long-term mean: A) Apex community B) Climax community C) Seral community D) Typical community

B

During primary succession at Glacier Bay, species diversity continues to increase throughout succession for which group(s) of plants? A) tall shrubs and trees B) low shrubs and herbs C) mosses D) lichens E) all groups of plants

B

High nitrogen retention early in stream succession is probably due to A) nitrogen fixation by aquatic fungi. B) increasing biomass of algal and animal populations. C) increasing nitrogen inputs from surrounding terrestrial soils. D) increasing binding of nitrogen to developing organic sediments. E) reduced denitrification following disturbance.

B

In the "transition phase" of forest succession, A) biomass increases rapidly as the community reorganizes. B) biomass declines from an earlier peak. C) biomass stays constant, but species composition turns over rapidly. D) nutrient export increases dramatically and soils become depleted. E) one climax community gives way to another.

B

Robert MacArthur's study of forest warblers suggested that A) fewer warbler species can survive in more complex habitats. B) warbler species diversity increases with habitat complexity. C) warbler species diversity decreases with habitat complexity. D) most warblers have rather similar foraging niches. E) None of the choices are correct.

B

What nutrient is most limiting in the Baltic Sea (salt water)? What nutrient is most limiting in freshwater ecosystems?

Baltic Sea (Saltwater): nitrogen/nitrate Freshwater: phosphorous

Why does succession proceed faster in abandoned fields than in Glacier Bay?

Because of secondary succession where the soil is already there

*Consumer Control of Primary Production* Primary production rates can be controlled by bottom-up (abiotic) processes. What are some examples?

Bottom-up = light, temp, water, nutrients

"Primary" succession is succession that A) involves establishment of primary producers where there were none. B) leads to establishment of a climax community dominated by primary producers. C) occurs on newly exposed geologic substrates, not organic soil. D) occurs where organic soils have been exposed but not destroyed by disturbance. E) occurs after fire or agricultural abandonment.

C

A ___________ is integral to the health of a ecosystem. A) dominant species B) Lotka species C) Keystone species D) Tertiary consumer

C

According to the "facilitation" hypothesis, pioneer species modify the environment in ways that A) make it more suitable for their own survival, and less suitable for other species. B) make it less suitable for their own survival, but more suitable for survival of other pioneer species. C) make it less suitable for their own survival, but more suitable for survival of late-successional species. D) make it less suitable for survival of all species. E) make it more suitable for survival of all species.

C

As Hawaiian lava flows age over 4 million years, A) total soil phosphorous levels decrease. B) total soil phosphorous levels increase. C) total soil phosphorous stays about the same, but more phosphorous becomes refractory. D) total soil phosphorous stays about the same, but more phosphorous becomes weatherable. E) phosphorous limitation of primary production becomes less important.

C

How does canopy shading influence succession of pines and deciduous trees in the Piedmont of North Carolina? A) Canopy shading by deciduous trees is required for growth of pines. B) Canopy shading by deciduous trees prevents establishment of pines until late in succession. C) Canopy shading by deciduous trees prevents persistence of pines in late successional stages. D) Canopy shading by pines prevents establishment of deciduous trees. E) Canopy shading by pines kills deciduous trees that were established early in succession.

C

In plants, a combination of growth dynamics and structure is known as ____? A) cohort B) guild C) life form D) phenotype E) B&D

C

In the area of Glacier Bay, Alaska, the climax community is A) hemlock forest. B) muskeg. C) hemlock forest on steep slopes, and muskeg on shallower slopes. D) hemlock forest on shallow slopes, and muskeg on steeper slopes. E) Dryas mats with scattered alders and cottonwoods.

C

Species diversity is composed of ______? A) Number of species present B) Population of members of species present C) A & B D) Not listed

C

Succession can be defined by all the following EXCEPT: A) an orderly and directional change in plant communities B) a predictable change in plant communities C) seasonal changes in plant communities D) changes in animal communities taken place in a span of time from 1 -500 years E) B & D

C

_________ occurs in areas where disturbance destroyed the previous community without destroying the soil. A) Pioneer succession B) Climax succession C) Secondary succession D) Primary succession E) Disturbance succession

C

Large atmospheric pool of C as

CO2

______ is an important energy source for lakes.

Carbon

_________ is an essential part of all organic molecules.

Carbon

Important elements in nutrient cycling?

Carbon, Nitrogen, and Phosphorous

Serengeti primary production: When is compensatory plant growth, and therefore productivity, highest, lowest?

Compensatory growth is highest at intermediate grazing intensity, therefore, intermediate grazing facilities highest productivity. Lowest in regions of light grazing and heavy grazing. Light grazing is insufficient to produce compensatory plant growth. Heavy grazing damages plants and reduces their capacity to recover.

The total amount of energy entering an ecosystem controls what factor of a food web, how?

Controls the number of trophic levels in a system because as energy losses between trophic levels accumulate, there is eventually insufficient energy left to support a viable population at a higher trophic level.

Disturbances can alter a community's stable environmental conditions, also called its A) frequency. B) intensity. C) heterogeneity. D) equilibrium. E) niche space.

D

In the Piedmont of North Carolina, as plant diversity increases through secondary succession, bird diversity A) increases at first, but then declines late in succession. B) increases steadily through succession. C) increases slowly at first, but then rapidly late in succession. D) increases rapidly at first, then plateaus late in succession. E) first decreases, but later increases.

D

The pioneer species at Glacier Bay, Alaska include A) mosses. B) Dryas. C) alders. D) horsetails. E) hemlocks.

D

Which statement about changing ecosystem properties during succession is false? A) biomass increases B) community respiration increases C) primary production increases D) soil depths decrease E) stream spiraling lengths decrease

D

An anaerobic energy-yielding process carried out by certain bacteria. It converts NO3- to N2, which enters the atmosphere where it can be re-fixed.

Dentrification

Nitrogen exits the organic matter pool of ecosystems via _______________.

Dentrification

Stability may exist (terrestrial biomes) Examples?

Different biomes have been at their locations for long time. Possible evidence of stability. -Also relationships between Net PP and herbivore biomass -Relationship between AET and Net PP. balance has been established in different ecosystems -predatory vs prey biomass

Disturbance and nutrient cycles:

Disturbance can have large impacts on nutrient dynamics.

A community is defined as A) a group of organisms that all make their living in a similar way. B) a group of individuals of a single species inhabiting a defined area. C) the portion of a defined area that supports life. D) a group of subpopulations living in separate locations with active exchange of individuals among subpopulations. E) an association of interacting species inhabiting a defined area.

E

Begins with the germination of r-selected species from seeds already in soil: A) Pioneer succession B) Autogenic succession C) Primary succession D) Xerarch succession E) Secondary succession

E

In most ecological communities, we find A) more rare species than moderately common or very common ones. B) more very common species than moderately common or rare ones. C) no rare species—apparently "rare" species are artifacts of incomplete sampling. D) roughly equal proportions of rare, moderately common, and very common species. E) more moderately common species than rare or very common ones.

E

In secondary succession on abandoned fields in the Piedmont of North Carolina, important pioneer species include A) horsetails. B) Dryas. C) broomsedge (Andropogon). D) pine seedlings. E) crabgrass and horseweed.

E

Prairie dog disturbances maximize plant diversity A) by burrowing and grazing. B) by creating patches open for dispersal. C) by allowing good competitors and good colonizers to coexist in the grassland. D) at intermediate levels. E) All of the choices are correct.

E

Species dominance within a community can be measured by which of the following: A) cover B) density C) frequency D) importance value E) B & C F) all

F

What effect does soil fertility have on terrestrial NPP? Discuss several lines of evidence associated with tundras.

Experimental manipulations of soil fertility influenced NPP. (1) The addition of fertilizer containing nitrogen, phosphorus and potassium to a tundra led to doubled primary production. (2) Dry tundra meadow: the addition of phosphorus alone was negligible, but the addition of nitrogen alone had significant effects; therefore, nitrogen is the main limiting nutrient to net primary productivity in dry tundra meadows. (3) Wet tundra meadow: the addition of both phosphorus and nitrogen alone resulted in significant increases in NPP, suggesting that both are jointly limited and thereby limit production in wet meadows. *when both nitrogen and phosphorus were simultaneously added in the dry and wet meadows, they had an interactive effect such that production increased to greater than it was for either nutrient alone.

Bacterial processes drive much of the global N cycle, but humans have large impacts also. Examples include

Fertilizers, fossil fuel combustion -Assimilation, Nitrification, Ammonification, Detrification

The use of _________ __________ has greatly accelerated the carbon cycle.

Fossil Fuels

Serengeti grasslands offer example of consumer control. What is primary production in the Serengeti impacted by?

Grazers - consume 66% of annual PP

Results of species richness experiment in Glacier bay?

Group-specific differences in diversity patterns: -mossed and lichens peak early, plateau -tall shrubs, trees increase, then decrease in diversity -low shrubs and herbs continue increasing in diversity

There is a ______ feedback loop between nutrient availability, primary production, and decomposition. In high nutrient conditions: In low nutrient conditions:

High nutrient = high uptake rates, leads to high PP. High nutrients leads to quicker remineralization and recycling nutrients back to the soil for use. Low nutrients= low uptake, low concentration of nutrients in primary producers so PP rate goes down. Leaves and tissues low in nutrients and low remineralization of nutrients.

What does the trophic cascade hypothesis propose about primary production in lakes?

Hypothesizes that feeding by piscivores and planktivorous fish affect the rate of primary production. Specifically, manipulating the piscivore biomass will lead to changes in biomass and predation of planktivores, herbivores and phytoplankton. An increase in piscivore biomass leads to a decrease in planktivore biomass, and consequently an increase in herbivore biomass (e.g., zooplankton like daphnia) and finally a decrease in phytoplankton biomass.

Where is light most available in the water column?

In the upper tidal zones

What happens when piscivore biomass is increased or decreased in lake systems?

Increase piscivore biomass (bass) --> decrease planktivores (minnows) --> increase herbivorous zooplankton --> decreased phytoplankton and rate of primary production. Decreased piscivore biomass (bass) --> increased planktivores (minnows) --> decrease in herbivorous zooplankton --> increase in phytoplankton and rate of primary production

What evidence is there to support that primary production in marine systems is nutrient limited?

Increased nutrients in the Baltic Sea led to increased chlorophyll concentrations (=increased algal biomass). The addition of phosphorus had negligible effects but the addition of nitrogen had significant effects on productivity. Marine studies show that N and Fe are main limited nutrients in many ocean habitats. P can be important in some parts; unpolluted coastal zones, open ocean

Studies of natural ecosystems and fertilization experiments demonstrate strong effects of nutrients on ________ and _______ _______.

NPP and plant biomass.

Global patterns of marine primary production: what is often a limiting nutrient in pelagic environments of the open ocean?

Iron (Fe)

Stability may exist. Example with

Lake superior

Unlike phosphorus, nitrogen has a _________ atmospheric pool (N2 gas). Only nitrogen-fixing bacteria can access this source.

Large N2 is not available to plants - can only use NH4+ or NO3-

Who suggested grouping organisms within an ecosystem into trophic levels? What is important about the feeding of each trophic level?

Lindeman each trophic level feeds on the level immediately below it

Terrestrial decomposition is often studied using what type of experiments?

Liter bag experiments

An energetically expensive process-triple bonds must be broken.

Nitrogen Fixation -very energetically expensive -"bacterial fixation" - bottleneck process; slow and expensive

Ammonium can be converted to nitrate (NO3-) by certain bacteria. This process is known as ________.

Nitrification

This element forms key biomolecules; amino acids and nucleic acids.

Nitrogen

This element turns over every ~625 years. It takes thousands of years for phosphorus.

Nitrogen

What is the most limiting nutrient in estuaries? Provide an example estuary.

Nitrogen Chesapeake bay

________ availability can affect how productive whole ecosystems are.

Nutrient

________ levels in water can also affect decomposition rates.

Nutrient

These elements are taken up, released upon death, and become available for uptake again. This use, transformation, movement, and reuse of essential elements is called ___________ ___________.

Nutrient Cycling

Oligotrophic versus eutrophic lakes

Oligotrophic lakes are low in productivity and therefore low in algae; since there is less algae disrupting the view, you can see further in oligotrophic waters. Eutrophic lakes are high in productivity and therefore have high algae concentrations.

The shortcoming of marine studies is their small scale. This is because it is difficult to do whole-system manipulation. What experiment comes closest?

Pelagic Fe Enrichment Experiments -where they fertilize the ocean with Fe. this can be way to manipulate climate change

________ is the primary limiting nutrient in lake ecosystems.

Phosphorous

What effect does precipitation have on terrestrial NPP? Discuss a line of evidence.

Precipitation - greater precip leads to more productive areas. When comparing grasslands environments east to west at the same latitude in the US, thereby controlling for temperature, primary production in grasslands increase with greater annual perception.

*Nutrient Cycles* Energy is lost as it travels through ("up") the biosphere; nutrients are often tightly cycled between comparements

Remember: as energy travels up the food web it is often lost

Spiraling length can be measured by the equation

S=VT v= velocity a nutrient atom moves downstream T=average time to complete cycle -if V is low and T is short, nutrient spiraling length is short

Higher species evenness in a community can be measured by a shallower slope on a rank-abundance curve. True False

T

_____ also has a strong positive effect on decomposition rates.

Temperature

T or F. Carbon must dissolve in water before becoming available to aquatic primary producers?

True

True or False: Nitrogen is not the only nutrient that limits rates of decomposition.

True

True or False: Nitrogen-fixing bacteria and lightning are the only two sources of "new" Nitrogen.

True

T or F. Micro/macronutrients can limit plant productivity?

True. Justus Liebig's "Law of Minimum"

Discuss the whole-lake fertilization experiment conducted in Experimental Lakes in Ontario, Canada

Two lakes supporting similar phytoplankton biomass were used for the experiment. One was used as the control and one received an addition of fertilizer (carbon, nitrogen and phosphorus). After fertilization, phytoplankton biomass increased in the experimental lake. When fertilizing stopped, phytoplankton biomass decrease in the experimental lake.

Global patterns of marine primary production: what is the main nutrient source in open oceans?

Vertical Mixing

Energy flow in a temperature deciduous forest: of total solar energy coming in, how much is... a) reflected? b) converted to heat? c) absorbed during evapotranspiration? d) fixed by plants as gross primary production? e) used in plant respiration? f) left for net primary production?

a) reflected = 15% b) converted to heat = 41% c) absorbed during evapotranspiration = 42% d) fixed by plants as gross primary production = 2.2% e) used in plant respiration = 1.2% f) left for net primary production = 1%

What is terrestrial net primary production (NPP) limited by?

actual evapotranspiration

Actual evapotranspiration: what two factors is it effected by?

affected by precip and temp -such that it increases with increasing precip and temp

Water Phosphorous concentrations are positively correlated to ________ ________ and primary production rates.

algal biomass (chlorophyll concentrations) [graph shows increased phosphorous = increased pp]

Primary Production Rate:

amount of carbon fixed or biomass produced/unit of time

Actual evapotranspiration (AET)

annual amount of evaporation plus transpiration in a landscape

Temperature is also important for decomposition in aquatic ecosystems.

as temp increases, decomposition increases

Photic Zone

as water depth increases, primary production is dominated by free-floating phytoplankton within the upper waters. -lightened water column of a lake or ocean, inhabited by plankton.

What are the only depths where NPP is possible?

at depths where photosynethsis exceeds respiration

Overall, why is primary production higher on land?

b/c the ocean occupies a larger portion of land surface but only contributes less than half

Why does primary productivity generally decrease in winter?

because the ice cover reduces light

Aquatic Primary Production in Streams and Rivers are mainly _______ _______ and ______ _______.

benthic algae and vascular plants

nutrient release

both the quantity and quality of organic matter as a food source of decomposers directly influence the rates of decomposition and nitrogen minteralization

______ and ________ properties of material are also important:

chemical and physical -soft, high N leafs decompose faster

Studies of succession of Glacier Bay shows

complex combination of inhibition and facilitation -spruce experience both facilitation and inhibition at different stages of succession

Ecosystem Ecology

concerned with the flow of nutrients and energy

Phosphorus is absorbed by plants and microbes and ________ through ecosystems. It eventually gets washed into the ocean.

cycles

Disturbance and Nutrient Cycles: _____ generally increases nutrient loss from ecosystems.

disturbance

The introduction of exotic plants to ecosystems may be considered a type of ____________.

disturbance

Most trophic cascae examples from aquatic systems: simple food webs, less structural complexity

ex is with otters, sea urchins, keps, whales (ex of cascade)

Water currents move nutrients ________

downstream

Coriolis Effect

drives patterns of surface currents

When does species richness increase?

during early years of succession and more slowly during later stages.

Factilitation:

during this, early colonists change environment to make it more suitable to later colonists. -pioneer communities change to make it less suitable for them, but more suitable for later species. -helping to establish later, larger species.

Pioneer community: Characteristics?

early succession species - high growth rate, short life span, small size, good dispersal, high r -shortly after disturbance. don't persist long.

*Ecosystem Changes During Succession* Succession involves changes in _________ characteristics.

ecosystem

What concept is fundamental to the study of energy transfer within an environment?

ecosystem concept

What determines how much primary production there will be in terrestrial primary production and soil fertility?

element in shortest supply will determine how much pp there will be.

What happens as energy is transferred from one trophic level to another?

energy is lost and degraded

Both temperature and precipitation in terrestrial primary production show dispersal/variability. This is because they two quantities may interact, so they can be combined to ________________.

evapotranspiration

Spruce in Glacier Bay experience both

facilitation and inhibition -early pioneer stages: Dryas stages: -Alder stages: -Spruce Stages: *key point: often see different processes happening at the same time, contributing to successional sequence.

Disturbance and Nutrient Cycles: _____ can have large effects on stream ecosystem nutrient balance.

floods -peak in P associated with autumn leaf fall -export associated with spring snowmelt -*Most P export was irregular b/c it was driven by flooding from intense storms* -*If we consider floods as source of disturbance, the generalization that disturbance increases loss of nutrients from ecosystems is consistent*

Global patterns of marine primary production: Where are the highest rates of primary production by marine phytoplankton?

generally concentrated in areas with higher levels of nutrient availability therefore, highest rates along continental margins and in shallow seas rather than nutrient poor open oceans

Freshwater primary production is a tiny fraction of ________ _________.

global productivity

What is Ecological Succession?

gradual change in plant and animal communities in an area following disturbance. -ecological communities (composition, abundance, diversity) and ecosystems (productivity, nutrient availability) change through time.

slower water, _______ able to carry particles

less

Aquatic primary production is limited by ______ and ______ availability.

light and nutrient

Two major factors of aquatic primary production?

light and nutrients

________ _______ and _______ control stream PP rates.

light availability and nutrients

Nitrogen fixation also occurs abiotically via __________.

lightening

Global patterns of marine primary production: at what latitudes is there little vertical mixing, why?

little vertical mixing occurs at low latitude pelagic zones of the ocean because waters are warmer and thermally stratified.

________ may increase nutrient retention by stream ecosystems.

macroinvertebrates

When spiraling lengths are short, a nutrient may be used _______ times before it is washed out of a stream system.

many

What do liter bag experiments determine?

mass and nutrient loss rates from dead OM take portion of plant material, weigh, bag & leave in ecosystem for period of time. Then reanalyze change in comp. to see if mineralization has occured

What trophic levels do generalist species occupy?

may occupy intermediate, or multiple trophic levels

Spiraling

measured as the distance needed to complete one cycle

Primary productivity in marine systems is ___________ limited.

nutrient

In aquatic systems, decomposition is important to __________ _______.

nutrient availability

What controls the rate of primary production in freshwater ecosystems, why? What evidence is there to support this?

nutrient availability because the rate of primary production is determined by algal biomass - as algal biomass increases, so does the rate of PP evidence: there is a linear increase in phytoplankton biomass as a function of phosphorus concentration

What are aquatic and marine environments primarily limited by? Respectively?

nutrient concentration aquatic: phosphorous marine: nitrogen

Nutrient Cycling in streams and lakes: because nutrients in streams are subject to downstream transport, there is little ______ ______ in one place.

nutrient cycling

Detailed phosphorous budget in Bear Creek show high flow periods increase _____ ______.

nutrient export

Water flow affects nutrient dynamics:

nutrient spiraling

term to describe stream nutrient dynamics;

nutrient spiraling

Terrestrial and aquatic systems: Aquatic primary productivity depends on return of ________ (released by decomposition)

nutrients

Biological Retention

occurs through the uptake and storage of nutrients in animal and plant tissue

What is primary succession?

on newly created sites - "completely reset" -succession on newly exposed geological substrates, not significatly modified by organisms; for instance on newly formed volcanic lava or on substrate exposed during the retreat of a glacier.no soil, nothing for new things to develop. -"starting from scratch"

What is secondary succession?

only biological community is destroyed - "partial reset" -succession where disturbance has destroyed a community without destroying the soil; for instance, forest succession following a forest fire or logging.

Other soil properties that changed during succession at Glacier Bay study sites:

organic content, moisture, nitrogen concentration of soils all increased greatly. -soil bulk density, pH, and P concentration decreased.

Nutrient supply in terrestrial systems depends on conversion from _______ to ________ (available) form.

organic to inorganic

What is Global GPP?

overall total contribution to primary productivity

Nutrient sources

part of biosphere from where nutrients are released (like stream bringing nutrients into lakes)

Nutrient sinks:

part of biosphere to which nutrients are lost (like in sediments)

Plants in low-nutrient ecosystems produce litter with ___________ and ________ content that decomposes slowly and deter herbivory.

produce litter with high-lignin and low nutrient content

Primary production limits secondary production:

production of consumer biomass

Serengeti primary production: what abiotic factor is the rate of primary production positively correlated with?

rainfall

Ecosystems with greater nutrient availability generally support plant species that grow _______ and that allocate more to shoots and leave that contain nutrient levels that promote decomposition.

rapidly

Some carbon pools cycle ___________ while other sequester carbon for long periods (soil, peat, fossil fuels, carbonate rock). In the absence of human activity, these would take a very long time to return to the atmosphere.

rapidly

Energy loss with movement up the food web means

reduced energy available to each successive trophic level. -results in Pyramid Shaped energy distribution in food webs

Phosphorus is slowly released into the ecosystem through __________ weathering.

rock

Many of the factors controlling primary production rates among systems also affect _______ and _________ rates of primary production within systems.

seasonal and interannual rates

Most C is in ________ and is not in active cycling.

sedimentary rocks

Light in small streams is often function of _____________, not depth.

shading by trees

Flood disturbance in stream ecosystems is an example of ecosystem succession on _______ time scale.

short

What is the shortcoming of marine studies? Why?

shortcoming is their small scale -it is difficult to do whole-system manipulation

In addition to climate, local variation in _______ ________ _______ affects decomposition rates: positive relationship

soil nutrient content

Plant and animal community structure changes during primary and secondary succession. Many ecosystem properties also change during succession. For instance,

soil properties, such as nutrient and organic matter content, change during the course of succession

Ecosystems are powered by _______ _____. CO2 to simple sugars is ________ _________.

solar energy; primary production

These ecological studies showed that physical and biological properties of ecosystems are inseparable. Organisms acting upon mineral substrates contribute to the building of soils upon which spruce forests eventually grow around Glacier Bay. Soils, in turn,

strongly influence the kind of organisms that grow in a place.

Most ecosystems are powered by the ________.

sun

Terrestrial Primary Productivity is controlled by a combo of _______ and _________

temp and precip

Two main factors of terrestrial primary production?

temp and precip

Decomposition in aquatic systems is controlled by _________, ______, and ______.

temperature, composition of dead material, and ambient nutrient concentrations

What three things is terrestrial primary production limited by?

temperature, moisture, soil nutrients

The global annual PP is ~105 Gt of C ~55% of which is ______________

terrestrial

Stability =

the absence of change in aspects of community structure

Spiraling is measured as

the distance needed to complete one cycle - the longer the distance, the more open the spiral

Nutrient retentiveness

the tendency of an ecosystem to retain nutrients

The relationship between primary and secondary production is not 1:1. why?

there is loss of energy at every transfer between trophic levels -typical transfer efficiencies ~10%

With secondary succession in N. Carolina abandoned fields, the deciduous trees like oak and hickory eventually dominate. why?

they can reproduce in their own shade whereas the pine cannot develop in shade. -*Late successional oak-hickory forest is considered the climax-stage*

Top down controls

trophic cascade

T or F. number of trophic levels can be constrained by energy loss?

true.

____ ______ and ______play important roles in nutrient cycling in lakes and oceans.

vertical mixing and stratification -highest PP is early summer/late spring -lots of mixing in winter so nutrients are high, but light availability is low -vice versa in summer

Terrestrial and Aquatic Systems: In many ecosystems, a _____ separation between zone of production and zone of decomposition.

vertical.

How do consumers contribute to the control of productivity?

via top down control, trophic cascades

Spiral length depends on _____ ____ and ____ ______ of uptake and release

water velocity and biological processes

Terrestrial and aquatic systems: Nutrients enter streams from ______, _______, and ______ _____.

watershed, atmosphere, and ground water

Decomposition is much faster at the _______ site.

wet

What did they find?

whole lake-experiments showed that *P is main limited nutrient, with N as secondary limiting element*