Final Flashcards
What is mutualism?
a relationship that’s beneficial to both species
What’s an example of mutualism provided in the slides?
Lichen and Ants tending aphids -> aphids get protection from predators and ants get excretions from aphids which are full of sugar
What are the 4 characteristics of mutualism?
1) The benefits received
2) The degree of dependency
3) The degree of specificity = flowers depend on bees or butterflies for pollination, but some flowers can be pollinated by many different organisms, while others can only be pollinated by one type
4) The duration of intimacy = length/duration of the mutualistic connection that’s needed
What are the 4 benefits to mutualism?
1) provision of energy or minerals
2) protection from predators, parasites, or herbivores
3) reduced competition
4) dispersal of gametes or offspring
What could cause a relationship to switch from positive (e.g., facilitation) to negative (e.g., competition)?
Variation in the abiotic environment may cause a relationship to switch from positive (e.g. facilitation) to negative (e.g. competition). The influence of species interactions on community structure.
What did Callaway et al. 2002 study?
Study between competition and mutualism; is facilitation more important in shaping communities or is competition more important?
What was Callaway et al.’s experiment?
Went to communities and removed all individuals of the dominant plant species; did at high elevation (top of mountain) and low elevation (bottom of mountain). Nothing was removed from control plots.
In Callaway et al.’s experiment, what does a negative value mean for the community and what does a positive value mean?
Negative value = competition more important
Positive value = facilitation more important
What where Callaway et al.’s results?
At low elevation = increase in survival with removal of dominant species. At high elevation = decrease in survival with removal of dominant species. -> facilitation or positive interactions are more important at high elevation!!
Why would facilitation at higher elevations be more important?
at high elevations, temp, wind scouring, or soil instability may limit plant growth more than resource availability. Amelioration of these severe stresses by neighbours may favour growth more than competition for resources with the same neighbours since it could impair growth
Would you expect the same result achieved in Callaway et al.’s study in tropical regions at high and low elevations as results obtained from high and low elevations in the tundra?
Ecologists hypothesize that yes it’s the case, but they’re having a hard time demonstrating this.
What was Callaway et al.’s experiment proof of?
This experiment was the first compelling proof that facilitation can play a major role in determining the structure of communities, at least, in harsh conditions
What was the study conducted by Isaac and Gabriel?
they studied invasive species of trees in the tundra of california
What did Isaac and Gabriel get as results?
less mutualistic fungi (decrease in diversity) on the roots and more pathogenic fungi living on the roots of pine
Negative interactions with pathogenic fungi
Positive interactions with mutualist mycorrhizal fungi
What is a food chain?
a descriptive diagram that represents the flow of energy from prey to predator
What do arrows demonstrate in food webs?
The flow of energy
What is net primary productivity or NPP?
the amount of energy that’s being stored in plants in a given amount of time; related to producers
How do ecologists often simplify the representation of food webs?
They often simplify the representation of food webs by grouping species into broader categories that represent general feeding groups (trophic levels) based on the source from which they derive their energy
What are autotrophs?
Make their own food using light = primary producers
Why is the stability of a food web important?
It’s key to supporting diverse species
Is a food web more stable when it has more generalists of specialists?
MORE GENERALISTS
Food webs differ in connectance which are…
the proportion of all possible links
What is the formula for connectance (C)?
C = L/[S(S-1)/2]
L = # of links
S = Number of species in the food web
C = index of connectance in %
What does a Higher C % mean?
The higher the % means that each species interacts with a lot of other species which suggests that there are a lot of generalists and the food web is more stable.
What does a lower C % mean?
Lower # = more specialists and less food web stability.
What is linkage density?
the average # of links per species (average specialization)
What is the formula for linkage density?
L/S
What does a high linkage density mean?
High linkage density will mean high connectance because the 2 are very connected.
What was the hypothesis for Start et el. 2019?
As you go from a natural setup to a highly humanized ecosystem you would go from food webs that were big and complex to food webs that are smaller (decrease in species richness)
What does the thickness of the arrow mean in Start et al.’s study?
thick arrow = interaction is more common
thin arrow = less common interactions (rare species) -> likely to disappear first due to stochastic extinction
What were the results in Start et al.’s study?
when you’re in the forest there’s low linkage density, but there’s high richness especially of the primary consumers. In the city, you lose a lot of the primary consumers (rare/specialist species), but the linkage density and connectance increases. Therefore, the food web is more stable in Urban environments.
What do indirect interactions complicate the prediction of?
indirect interactions make it more difficult to predict what will happen if a species goes extinct
True or false: Community interactions can be understood simply using direct species interactions
FALSE: need both indirect and direct to understand community interactions
What indicates the proliferation of indirect species interactions?
food webs
What is an example of indirect interactions using lynx and snowshoe hare? (Adapted by Krebs et al. 2001)
Lynx directly affects herbivore #s (e.g., snowshoe hare) which enhances the survival of spruce seedlings and saplings. LYNX HAVE INDIRECT EFFECT ON SPRUCE
What is a summary of the negative and positive effects occurring in the lynx example of indirect effects?
- Predation of lynx and snowshoe hare is negative for the snowshoe hare
- Predation of snowshoe hare on spruce is negative for the spruce
- Conclusion: Lynx has a positive indirect effect on the spruce
what does lumping species into trophic levels raise questions about?
Lumping species into trophic levels raises questions about feeding-related control of community structure.
What are the 2 different views of food webs?
1) Top down control
2) Bottom up control
What is top-down control?
involves higher trophic levels regulating abundance and productivity of primary producers
What is bottom up control?
involves primary producers regulating the pops of highe trophic levels
What are trophic cascades?
the propagation of indirect effects b/w nonadjacent trophic levels in a food chain or food web
If a study finds evidence of the occurrence of a trophic cascade, what food web control does it support?
It supports the view that food webs are top-down regulated
What occurred in the O’Dowd at al. 2003 study on the invasion by the yellow crazy ant on Christmas Island?
Example of top-down control or trophic cascade: the yellow crazy ants invaded and ate the herbivorous red-land crab which resulted in a positive effect on the forest (primary producer)
What did Chen and Wise’s 1999 study on collembola and fungus demonstrate?
example of bottom-up control: In quadrats that had food enhancement, 6 weeks later, the abundance of collembola was much higher in the enhanced plot than the control plots. This study provided evidence of a direct positive effect; a bottom-up control which increases the abundance of consumers
What is the relationship between predators and collembola in Chen and Wise’s 1999 study?
Positive indirect effect of food addition on predators. This suggests that the relationship between collembola and their predators is negative. Food addition caused collembola to increase thus increasing the amount of food for predators and so they increased as well.
Why are values for predators occurring later (lag in effect) in Chen and Wise’s 1999 study?
It’s because to obtain results on predators, you have to wait to see an increase in their prey (collembola)
What do error bars signify?
the variation in results between different plots
What does a small error bar mean?
smaller the bar means that the #s obtained between plots was pretty consistent
What does no overlapping error bars mean?
that the p-value is likely significant
What type of food web are bottom-up effects important in?
detritus-based food web
What type of species is the american bison and what do they do in their habitats?
keystone species: it can inhibit woody encroachment within grasslands and parkland ecosystems
What do bioengineering keystone species do?
they can modify their habitat
What are 2 examples of bioengineering keystone species?
1) Beavers: can alter heterogeneity and local hydrology as a result of dam-building: create ponds = new habitat
2) Ants: can alter the physical and chemical structure of soil by digging holes and bringing food to their nest since they put garbage in their mounds = higher bacterial, microbial, insect, and plant activity
What do removal experiments do?
They’re employed to assess the influence of proposed keystone species on community structure?
Who conducted the most famous removal experiment on starfish pisaster?
Bob Paine
What occurred in Bob Paine’s removal experiment?
following the removal of the predatory starfish Pisaster, prey species dropped from 15 to 8: the starfish regulated the relative abundance of more competitive species such as several mussels and barnacle species; without it, sub-level predators overexploited the prey to extirpation
What is an observational study?
visit a bunch of places and measure variables then use statistical tests to see the significance or lack thereof between variables
What is an experimental study?
manipulate something on purpose (addition or removal of something) then perform statistical tests to see significance or lack thereof
What is the ultimate source of energy that keeps the planet functioning?
The sun
How can solar energy (photons) be used as energy by plants?
Used by plants in photosynthesis and that energy is stored in the chemical bonds of carbon-based compounds. Then, this fixed energy in their tissues becomes available to primary consumers (herbivores)
What else can solar energy (photons) be used as energy?
It can be converted to heat which warms the Earth, warms the atmosphere, drives the water cycle, and causes the currents of air and water
Does energy flow or cycle?
Nutrients cycle, and energy flows through ecosystems
What is energy subject to?
physical laws
What are the 2 forms of energy?
1) potential: energy stored: available for performing work
2) kinetic: energy in motion and performs work at the expense of potential energy
What are the 2 laws of thermodynamics that govern the expenditure and storage of energy?
1) 1st law: energy cannot be created nor destroyed; it’s merely transformed or transferred
2) 2nd law: when energy is transferred or transformed, part of it assumes a form that cannot be passed on any further (lost as heat)
What is entropy?
the reduction in potential energy
What is primary productivity the measure of and how do ecologists use it?
It’s how we measure the rate of energy entering ecosystems and it’s a way for ecologists to quantify how well an ecosystem is performing
What is GPP?
Gross Primary Productivity: the total rate of photosynthesis, or energy assimilated by autotrophs (harder to quantify) (energy captured per unit of area per time). Some of this energy is sued by plants for metabolism/cellular respiration and growth.
How could you quantify GPP using an experimental study?
Collect water with photosynthetic organisms in bottles, and cover one with a cloth and put other bottle under a light. Then use a dissolved oxygen sensor to measure dissolved oxygen in each bottle. After a certain amount of time, collect measurements. Dark bottle measures respiration and light bottle measures photosynthesis and respiration (NPP). Subtract each of the final values for light and dark with their initial values, then take those values and add them = GPP.
What is NPP?
Net primary productivity: the rate of energy storage as organic matter after respiration; NPP = GPP - R. made available to other trophic levels
What is productivity?
the rate at which organic matter is created by photosynthesis
What is biomass?
the amount of organic matter present at any given time
What are 3 examples of units of productivity?
1) Energy/area/time = kcal/m2/yr
2) Mass of organic matter/area/time = g/m2/yr
3) Standing crop biomass = mass of organic matter/area = g/m2
How is NPP commonly measured?
commonly measured by estimating the change in standing crop biomass (SCB) over a given time interval
What are 2 possible losses of biomass?
1) death of plants (D)
2) consumption by consumer organisms (C)
Why are you likely to underestimate biomass?
Because it will likely be consumed or die
Terrestrial NPP increases with an increase in what 3 factors?
1) increase in mean annual temp
2) increase in length of growing season
3) increase in precipitation
What is mean annual temp and length of growing season directly related to?
directly related to the annual intercepted solar radiation at a site: more sun = more energy for primary producers
What does higher precipitation do for plants and thus NPP?
The higher the precipitation, the more water available for transpiration, therefore, stomata remain open to take in CO2 for longer amounts of time
Why does productivity change in different parts of the planet?
When there’s low precipitation you get less productivity than when there’s more precipitation. Additionally, as it gets warmer, you’re in places with a longer growing season and areas that receive more energy, so it’s easier to gain more biomass in a summer that lasts 6 months instead of 4 months.
What are the 3 interacting effects from temp and precipitation on primary productivity?
1) warm air temps increase the potential for evaporation and increase transpiration rates and water demand
2) if temps are low, rates of photosynthesis and productivity will be low regardless of water availability
3) High temps with low precipitation (deserts) = no vegetation
Why do northern states in study with dots, have lower NPP?
because the length of the photosynthetic period is shorter compared to more southern states (turquoise and blue) there’s more NPP because the growing season is longer.
What is the photosynthetic period?
Photosynthetic period = summer, growing season, length of time when photosynthesis can occur. This increases as you get closer to the equator.
Where are the regions with the highest rates of NPP?
located in the equatorial zone: Year-round warm temps and ample precipitation
How do you build a map that measures productivity ranges across the planet?
Energy proxy = AET and we found a way to measure AET
What is Actual evapotranspiration (AET) and how is it estimated?
the combined value of surface evaporation and transpiration. This is fairly easy to estimate as long as you know enough about temp and precipitation.
What is AET a proxy for?
AET = proxy for productivity/energy
What is a proxy?
A proxy is something that we know is strongly correlated with what we’re trying to measure, but it’s much easier to estimate.
In Chu et al. 2016’s study, how did they build a model to explain variation in NPP on the planet?
To predict NPP, you need to know how old the forest patch is and what was the initial biomass of the forest. Young forests grow much faster than old forests (gain more biomass faster) so you expect that young stem in succession
How did Chu et al. 2016’s study improve predictions of NPP?
They found a strong positive relationship between growing season, precipitation, temp, and initial biomass of stems. Thus, to make better predictions of NPP, we should consider the initial stem biomass
What did Reich et al. 2001’s study examine?
P. Reich examined the relationship between soil N availability and aboveground NPP in oak savannah stands
How did Reich et al. 2001’s study improve the predictions of NPP? (limiting nutrient)
He measured N mineralization in relation to NPP and he found a positive relationship. In areas of the ecosystem with low levels of N, there were low levels of NPP, but high levels of N gave high levels of NPP
What is mineralization?
Conversion of organic nitrogen to inorganic forms (e.g., ammonia) by decomposers (bacteria and fungi).
What is immobilization?
inorganic nutrients are taken up by soil microbes and become unavailable for plant uptake
What is N immobilization?
Microbial uptake of inorganic nitrogen for their own growth
What is net mineralization rate?
Difference between mineralization and immobilization
What is secondary productivity?
the productivity of consumers
Who is NPP available to?
NPP is energy available to heterotrophs
When is secondary productivity the greatest?
is the greatest when the birthrate of the pop and the growth rate of individuals are highest (growth of organisms and population)
what does secondary productivity depend on?
It depends on primary productivity for energy and thus primary productivity is a constraint on secondary productivity; primary productivity sets the amount of energy available to the ecosystem
What did S. McNaughton do?
compiled data from 69 studies that reported Net primary and secondary productivity for a wide range of terrestrial ecosystems
What did McNaughton et al. 1989’s study find while studying herbivores and net primary productivity?
When there’s more (NPP) productivity, herbivores can consume more grass in time. High NPP means the change in mass increases through time as well
Why is there considerable variation among consumer organisms in their efficiency to transform energy consumed into secondary growth (growth and reproduction)?
It’s because some organisms are very good at taking energy from plants and storing it into their tissue, while others can only store a little and use a lot for respiration = slow vs. fast metabolism
Do elephants have high or low consumer efficiency?
elephants don’t move much and spend lots of time eating so they probably store a lot of their energy in their tissue = high efficiency
do mice of high or low consumer efficiency?
Mice are always running around so they have a fast metabolism. Each time they eat something and move, they store less in their tissues since they’re burning all the energy
What is the assimilation efficiency?
-the ratio of assimilation to ingestion (A/I). The more you keep, the more you assimilate
-Ingested food (I) -> Assimilated (A) and Expelled (W)
What is production efficiency?
-the ratio of production to assimilation (P/A). Related to metabolism. Higher when you respire little vs how much you produce. How much assimilated energy you waste through respiration
-Assimilated energy (A) -> Respiration (R) and Production (P)
How much less efficient (in %) are small mammals at storing energy in their tissues?
at least 50% less efficient
What small creatures are surprisingly much more efficient in their productivity even compared to some large mammals?
Insects
How can secondary productivity be measured?
Weight gain
So who’s better at assimilation efficiency (A/I) between endotherms and ectotherms, and carnivores and herbivores?
Endotherms > ectotherms
Carnivores > herbivores
What are the production efficiencies (P/A) in % for invertebrates, ectotherms and endotherms?
1) invertebrates = 30-40%
2) Ectotherms = 10%
3) Endotherms = 1 to 2 %
What characteristic of endotherms affects their production efficiency?
Endotherm body size affects production efficiency
What are feeding relationships within food chains defined in terms of?
feeding relationships within a food chain are defined in terms of trophic or consumer levels
What are major feeding groups defined based on and what are the 3 groups?
common source of energy:
1) Autotrophs
2) Herbivores
3) Carnivores
What is the energy flow model for food chains?
energy flow in a trophic level decreases with each successive level of the food chain
What does the energy pyramid model depict for food chains?
Energy pyramid depicts the total energy processed by each trophic level
What is Trophic efficiency (TE)?
the ratio of productivity in a given trophic level (Pn) to the trophic level it feeds on (Pn – 1)
TE = Pn/Pn – 1
Will primary consumers that are good at storing energy absorbed from eating primary producers have high or low secondary productivity and TE?
High secondary productivity, and high TE
How can ecosystem pyramids be constructed?
ecosystem pyramids can be constructed by summing the biomass in each trophic level;
-decreasing energy transfer with increase in trophic level -> decrease standing biomass of organisms
What is the total mass supported at each level of ecosystem pyramids limited by?
The total mass supported at each level is limited by the rate at which energy is being stored at the next-lowest level = leads to general narrowing of the pyramid
Why is decomposition important for productivity?
Plants will die eventually or leaves are shed and branches are lost and when this occurs, nutrients stored in plant tissue could possibly become available to the plant. BUT for this to happen, there needs to be decomposition. The pool of nutrients is controlled by decomposers since they convert organic material into a form that can be absorbed again by plants.
What forms do plants to up inorganic N as?
ammonium (NH4+) and nitrate (NO3-)
What is nitrogen taken in by plants used for?
it’s used to produce proteins, and other nitrogen-based compounds. N is transformed from inorganic to organic form, incorporated into living plant tissues
What is senescence?
occurs throughout the lifespan, including during embryogenesis, and it’s the condition or process of deterioration with age
What happens when senescence occurs in ecosystems?
nutrients are returned to the soil as dead organic matter
What is the process of retranslocation?
plants absorb some of the nutrients from senescing tissues into the perennial parts to be stored and used in producing new tissues
What % of N do plants recover before leaves fall?
as much as 70%
What is decomposition?
The breakdown of dead organic matter (complex molecules) into simpler substances (e.g. CO2, water, sugars, mineral salts) by decomposers
What are the 3 processes of decomposition?
1) leaching
2) fragmentation
3) chemical breakdown
What is leaching?
water removes soluble compounds from matter
what is fragmentation?
physical breakdown by detritivores
What is chemical breakdown?
enzymes from microbes degrade organic matter
What’s the difference between detritivores and decomposers?
While decomposers break down dead, organic materials, detritivores—like millipedes, earthworms, and termites—eat dead organisms and wastes
What are the 2 major categories of decomposers and how do they decompose material?
1) Microflora: they secrete enzymes to breakdown the complex organic compounds
2) Invertebrate detritivores: they fragment organic matter
What are the 2 types of organisms within the microflora decomposer category?
1) Bacteria: aerobic (O2) or anaerobic (fermentation)
2) Fungi: extend hyphae into tissue, major decomposers of plants
What are the 4 types of organisms within the invertebrate detritivores decomposer category (order by size)?
1) Microfauna (<100 µm): Protozoans, nematodes
2) Mesofauna (100 µm–2 mm): Mites, springtails
3) Macrofauna (2–20 mm): Earthworms, millipedes
4) Megafauna (>20 mm): Snails, crabs
What do omnivorous nematodes feed on (Microfauna)?
feed on a combination of detritus, bacteria, fungi, and smaller organisms. One of the most common animals in the world in terms of biomass
What do Protozoans such as Amoeba feed on (Microfauna)?
consume fine organic particles, and microorganisms found on detritus. Use phagocytosis to engulf food particles and contribute to nutrient cycling
What’s the key takeaway for microfauna?
microfauna enhances decomposition by feeding on decomposer microbes, releasing nutrients for plants, and breaking down organic material, which increases surface area for further microbial activity for decomposition
What do mites such as Oribatid mites (Mesofauna) do in the ecosystem?
essential for breaking down organic detritus and distributing fungi
What do springtails (mesofauna) do for the ecosystem?
they are small soil-dwelling decomposers that feed on organic matter, fungi, and decaying plant material
What do Earthworms (macrofauna) do for the ecosystem?
moves litter from the soil surface into the mineral layer and deposits casts of mixed organic and mineral material back on the surface
What do millipedes (macrofauna) do for the ecosystem?
primarily consumes decaying wood and leaf litter
What do snails (megafauna) do for the ecosystem?
feed on decaying plant material, fungi, and detritus
What do crabs (megafauna) do for the ecosystem?
scavenge dead organic material and break it down, while their burrowing activity aerates the soil and enhances microbial processes -> they differ other detritivores bc of their burrowing + aerating
What do functional groups that simplify the understanding of ecosystem roles overlook?
may overlook species-level complexity
What reveals hidden feeding behaviours like omnivory and multichannel trophic interactions?
advances in tools (e.g., isotopes, DNA analysis)
What are multi-channel trophic interactions?
interactions that are occurring at multiple levels
What are some overlooked detritivores?
Lepidopterans: certain moth species feed on dead plant matter or dried organic material
What are 2 groups of lepidopterans that act as detritivores?
1) Grease moth: feeds on dried grain, dried insects, excrements and grease of dead bodies
2) Common clothes moth: feeds on dead organic material such as feathers, skin, hair, dried insects, clothing, and natural fibers
How do ants act as detritivores?
many ant species feed on dead organisms, such as animal carcasses and plant material and transport it inside of their nests which fragments decaying matter enhancing decomposition
In P. Schultheiss, S.S. Nooten, R. Wang, M.K.L. Wong, F. Brassard, & B. Guénard’s study on the abundance, biomass, and distribution of ants on Earth, what were their 2 sample methods?
1) leaf litter samples
2) pitfall traps -> abundance and activity
In P. Schultheiss, S.S. Nooten, R. Wang, M.K.L. Wong, F. Brassard, & B. Guénard’s study on the abundance, biomass, and distribution of ants on Earth, where did they find that ants were more abundant on the surface?
in tropical savannahs and tropical moist forest
In P. Schultheiss, S.S. Nooten, R. Wang, M.K.L. Wong, F. Brassard, & B. Guénard’s study on the abundance, biomass, and distribution of ants on Earth, what was their biomass?
ants = 12 megatons in biomass
In P. Schultheiss, S.S. Nooten, R. Wang, M.K.L. Wong, F. Brassard, & B. Guénard’s study on the abundance, biomass, and distribution of ants on Earth, when did they find that ants were more active and less active?
ants are more active and move more in hot, dry environments, where they might be a little less productive so they have to be more active and move to get food
How has the introduction of earthworms in North America transformed the environment?
It accelerated decomposition and it modified microbial communities; in Northern forests with thick layers of decaying matter, earthworms greatly reduced this layer by speeding up decomposition
What negative effect did the introduction of earthworms have on northern ecosystems?
caused a loss of native species which were unadapted to the new conditions created by exotic earthworm spp
How do you study decomposition in terrestrial and aquatic environments?
1) Terrestrial: litterbag experiments
2) Aquatic: Leaf pack experiments
-> weigh bags before and after: mass loss indicates decomposition rate
When studying decomposition using bags, what does mass loss indicate?
decomposition rate (e.g., carbon release as CO2). SO weigh bag before and after
In a litterbag experiment in central virginia, 3 different types of tree leaves were put into a bag. How did decomposition rates differ and why?
Red maple decomposed fastest, then white oak and lastly sycamore, this is because leaves/trees with high lignin content decompose slower. Rich in lignin = low quality
Why is lignin hard to decompose?
due to the complexity of its bonds and cross-linkages, and because it has a relatively low nitrogen content.
Why is decomposition in boreal forests very low?
Because conifers have needles which are very hard and therefore are very rich in lignin and in boreal forests, the majority of the trees are conifers = slow decomposition
What’s the difference between leaves with low lignin vs. those with high lignin?
Not much lignin = thin leaves with a light green
VS.
Lots of lignin = thicker and harder to bend, with a darker green
What are 2 factors that influence the rates of decomposition?
1) litter quality (composition of the organic material)
2) abiotic factors (temp, moisture, and O2 availability)
What are the 3 levels of litter quality?
1) High quality carbon compounds (e.g., glucose) decompose quickly
2) Moderate-quality carbon compounds (e.g., cellulose) take longer to decompose
3) Low-quality carbon compounds (e.g., lignin) decompose very slowly due to complex structures and it yields little energy to decomposers
what were the results from the study smith and smith 2014 on carbon, cellulose and lignin decaying in leaves?
It shows how different compounds we find in leaves fluctuate in composition. Lignin remains in the leaf even after months because there are a lot of interactions within the molecule therefore it requires a lot of energy to break down the molecule. The amount of lignin in the leaf has a great impact on the rate of decomposition in the leaf
What compound in leaves demonstrated in smith and smith 2014’s study has a great impact on the decomposition rate in leaves?
Lignin is a complex molecule with many interactions, thus requiring a lot of energy to break down, so the amount of lignin in leaves has a great impact on the rate of decomposition in the leaf
What conditions favour microbial activity and thus faster decomposition?
warm and moist conditions
What conditions reduce microbial activity and thus slower decomposition?
low temps and dry conditions
In a figure adapted from Whitkamp and Fr4ank 1969, the blue line = temp and black line = amount of CO2 released from microbes. When is the activity of microbes the highest according to this figure?
When temps are the highest around noon is when the most amount of Co2 is released from microbes
In a Case Study on Red Maple Leaves by Smith & Smith 2014, how did decomposition rates vary across new hampshire, west virginia and virginia? And what do these findings demonstrate?
New Hampshire: cold and dry = slow decomp
West Virginia: warm and wetter = faster decomp
Virginia: warmest and wettest = fastest decomp
Findings demonstrate that abiotic and biotic influences on decomposition differs geographically
In a figure adapted from Valiela 1984 studying oxygen’s role in decomposition, what were the results?
Aerobic conditions (blue line) = accelerate decomp
Anaerobic conditions (pink line) = slower decomp
Findings demonstrate that in waterlogged environments, fungi, which require O2, are less active, slowing down lignin decomposition
Why is decomposition in peat bogs slow (4 reasons)?
1) Anaerobic conditions due to water conditions
2) acidic conditions created by acids released by Sphagnum mosses
3) many peat bogs are found in cold climates
4) plant material like sphagnum moss, contains lignin
Is higher nitrogen content better or worse for microbes and fungi?
higher nitrogen content = higher nutrient value for them
What are the rates of Nitrogen with immobilization and mineralization during decomposition?
Nitrogen increases above initial concentrations as the rate of immobilization exceeds the rate of mineralization. But, as decomposition proceeds, the rate of Nitrogen mineralization exceeds that of immobilization, and there is a net release of Nitrogen from the litter
What is the carbon to nitrogen ratio in plant litter?
50:1 to 100:1
What is the carbon to nitrogen ratio in microbial biomass?
10:1 to 15:1
Based on the plant litter to microbial biomass ratios of carbon to nitrogen, what occurs to this ratio with decomposition?
As microbes consume plant material, the carbon to nitrogen ratio declines: When carbon quality drops, mineralization exceeds immobilization, releasing nitrogen and other nutrients, leaving behind more recalcitrant compounds?
What does recalcitrant mean?
hard to break down
What is humus?
part of the organic layer which decomposes very slowly, but remains an important source of soil carbon, and nutrients
What occurs as you go from top of soil to lower in soil?
top soil = mostly organic, decomposing material to lower in soil = more minerals and recalcitrant molecules lignin and microbial mass (chitin) accumulates, forming humus
What are the main horizons of soil?
Organic (O), surface A, surface B and surface C, bedrock (R)
What is the rhizosphere?
the soil zone influenced by plant roots, with intense microbial activity
Is decomp faster or slower in rhizosphere in comparison to surrounding soil?
faster because there is more microbial activity in the rhizosphere, and root exudates (carbs) fuel microbial decomposers, but lack N, thus increasing decomp rates
What organisms make N available to plants and how?
Protozoa & nematodes eat bacteria, excreting nitrogen as ammonia, making it available to plants.
What are 3 factors influencing decomposition rate in aquatic environments?
1) submersion: permanently submerged litter decomposes faster due to better microbial activity and detritivore access
2) water flow: flowing water increases oxygen availability, while in still water, particulate organic matter (POM) settles, undergoing gradual decomp
3) Aerobic vs. anaerobic decomposition: surface has aerobic bacteria that break down matter rapidly. Deeper sediments undergo slower anaerobic bacterial decomp bc O2 is depleted
How does decomposition differ from terrestrial to aquatic envs?
Terrestrial: plants physically bridge the production (canopy) and decomposition (soil) zones enabling efficient nutrient transport via roots and vascular system
Aquatic: in shallow waters, rooted vegetation plays the same role, but in deeper waters, primary production at top (phytoplankton) and decomposition in benthic zone, are physically separated
What does Smith & Smith 2014’s study on nutrient distribution and seasonal productivity in aquatic ecosystems show?
Top of water is hot, middle has rapid change in temp which separates the lake into 2 phases since bottom will be cold with less light and top will be hot with lots of light. Then turnover during the spring and fall reintroduce nutrients to the surface
What is a nutrient trap in estuaries?
nutrients (like nitrogen and phosphorus) are retained or recycled rather than being flushed out to the open ocean. This typically happens due to the mixing of freshwater from rivers and saltwater from the sea
Why could nutrient trapping be bad and why can it be good?
Bad: too much can lead to eutrophication - harmful algal blooms and O2 depletion
Good: nutrient trapping leads to high productivity
What is the biogeochemical cycle?
the cyclic flow of nutrients from the nonliving to the living (e.g., N fixation) and back to the non-living (decomposition) components of the ecosystem
What are 2 crucial cycles for the maintenance of life on Earth?
1) carbon cycle
2) nitrogen cycle
What are the 2 types of biogeochemical cycles?
1) gaseous
2) sedimentary
What occurs in gaseous biogeochemical cycles?
the main pool of nutrients are the atmosphere and the oceans; nutrients exchanged in forms of gas. This cycle is a global cycle because it’s easy for gas to travel across the atmosphere
What occurs in sedimentary biogeochemical cycles?
the main pool of of nutrients is the soil, rocks, and minerals
What are 2 important processes in more local sedimentary cycles?
1) erosion of rocks
2) weathering of rocks
What is weathering?
the breaking down or dissolving of rocks and minerals on the surface of Earth. Example = lichens extracting minerals making them accessible to local organisms
What is erosion?
sediments taken from one place to another
What does weathering and erosion do?
These processes release inorganic sources of minerals making them accessible to living organisms
What is an example of a nutrient that is released from weathering and erosion?
Phosphorous
What is an example of a hybrid gaseous and sedimentary cycle?
sulfur
What are both gaseous and sedimentary cycles driven by?
driven by the flow of energy through the ecosystem (photosynthesis, respiration)
What are both gaseous and sedimentary cycles tied to?
the water cycle (rain, leaching, wetfall, percolation); biogeochemical cycles could not exist without the water cycle
What is leaching in the water cycle?
nutrients passing from dead organic matter to dissolving in water
What is percolation in the water cycle?
wetfall and rain end up on organic matter and minerals leach into the water and causing the minerals to percolate into the ground where they end up in a larger body of water and bring the nutrients to other ecosystems
What is dry fall?
nutrients brought in by airborne particles and aerosols
What is wetfall?
nutrients supplied by precipitation
What is the common structure of all biogeochemical cycles (3 processes)?
1) inputs
2) internal cycling
3) outputs: an output can be an input for another cycle
How are nutrients inputted into a gaseous cycle?
Nutrients in the gaseous cycle enter the ecosystem via the atmosphere
How are nutrients inputted into a sedimentary cycle?
Nutrients in the sedimentary cycle enter the ecosystem via the weathering or erosion of rocks which releases minerals
What are the 2 sources of nutrients for aquatic ecosystems?
1) from surrounding land in form of drainage water, detritus, and sediment
2) from the atmosphere in form of precipitation
How is carbon outputted?
Release of CO2 from respiration by heterotrophic organisms, fire as well
What are the 2 ways that organic matter (which stores a lot of carbon) can be carried out of an ecosystem?
1) through water via surface flow or underground flow
2) by herbivores
What are 2 ways humans generated massive and rapid loss (output) of nutrients from ecosystems?
1) Human harvesting (farming and logging); nutrient loss must be replaced by fertilizers, otherwise system becomes impoverished
2) Fire converts a portion of the standing biomass and soil organic matter to ash = known as pyro-mineralization
How have we humans made ecosystems dependent on us?
because we input unnatural resources and lot of these ecosystems have lost their ability to absorb nutrients, so when large amounts of nutrients are inputted, the excess nutrients end up in lakes and rivers
What is the slash and burn approach?
slash and cut plants and burn the plants and this breaks down complex molecules into simpler ones. The amount of inorganic nutrients in the soil after burning is very high
How can the slash and burn approach lead to a massive and rapid output/loss in nutrients?
It releases a lot of inorganic material, and the time between burning and planting is often long which could lead to all the nutrients exiting the system through leaching into water then percolating into rivers and streams
How much carbon does the earth contain and where is most of this found?
The Earth contains 10^23 grams (or 100 million gigatonnes) of carbon! Most of this is found buried in sedimentary rock is not actively involved in the global carbon cycle
What organisms contain the most carbon biomass on earth?
Plants
What is a carbon sink?
a pool of carbon that tends to be growing in size and storing more carbon than it is releasing carbon from the atmosphere, sinks tend to sequester a lot of carbon
What is carbon sequestration?
The action of storing or accumulating carbon from the atmosphere into living or dead organic matter
What is a carbon source?
a pool of carbon which s shrinking in size and releasing more carbon in the atmosphere than it is sequestering
What is the largest carbon sink and why?
The ocean because of the constant passive diffusion between ocean and atmosphere
Why is land use change a cause of release of carbon in the atmosphere?
The typical way that we alter the use of lands is by deforestation and forests tend to sequester a lot of carbon, so we reduce the capacity of land to absorb carbon
What are the 2 man-made sources of carbon release in the atmosphere?
1) fossil fuel emissions
2) land-use change
How much carbon is involved in the global carbon cycle?
55 0000 gigatonnes (Gt)
Oceans contain 38 000 Gt of the total carbon in the carbon cycle. Is most of this contained in living or dead matter?
Both in oceans and terrestrial ecosystems, the amount of carbon stored in dead organic matter is greater than in living matter.
Is more carbon, in the terrestrial carbon sink, in soils or in living matter above gorund?
In soils = more carbon
What is the geographic trend for soils sequestering carbon?
the average carbon/volume of soil increases from the tropical regions poleward to the boreal forest and tundra
Why are peat bogs good at sequestering carbon (peat bog = carbon sink)?
The trees and sphagnum mosses in peat bogs are rich with lignin, thus slowing decomposition, additionally, sphagnum moss releases acid which also slows decomp
Where does the greatest accumulation of dead organic material occur?
in areas where decomp is inhibited (frozen or waterlogged soils)
Is it easier to link process and patter in experiments or observational studied?
experiments
Who introduced the concept of (eco)system ecology and when did it grow in prominence (with whom)?
by Paul Weis in 1920s and grew in prominence in the 60s with the work of Howard and Eugene Odum
What approach does system ecology take?
A holistic approach which focuses on the functioning entity rather than the sum of its parts
What is a system in regards to ecosystem ecology?
a set of interrelated parts that work together to perform functions within an environment; functioning system is more than the sum of its part. Systems can range from abiotic components to biotic ones
Why are feedbacks important to ecosystems?
they’re critical for ecosystem regulation
What does feedback refer to?
the output of one system process affecting (negative or positive) the process of another
What does a positive feedback (reinforcing feedback) result in?
results in the continued amplification of a process
What is an example of a + feedback loop?
Permafrost is melting due to global warming, but this releases methane and CO2 which causes more warming and thus more melting = continuous amplification
What does a negative feedback loop (correcting feedback) result in?
results in a damping of a process which keeps the ecosystem in check
What is an example of a negative feedback loop?
a caterpillar pop is large leading to a crash in milkweed pop, this makes it so that the next generation will have less food and the caterpillar pop will decrease, thus releasing pressure from the milkweed so it can bounce back
Which feedback loop is a mechanism by which ecosystems bounce back from disturbances?
- feedback loop
What is Homeorhesis?
a dynamic eqm that regulates ecosystem states
What is a dynamic eqm?
a regulatory process that returns a system back to a set point: Tendency of a community or ecosystem to fluctuate around an average -> never completely fixed
Is dynamic eqm steady through time?
No, probably not, but rather the ecosystem will be subject to periods of pulses caused by disturbances followed by negative feedbacks that return the system to an eqm point
What is a past theory that we discussed that has a similar concept of dynamic eqm?
Theory of Island Biogeography and the # of species at eqm on an island
what does dynamic eqm in ecosystems, which are the product of - feedback loops, provide?
resistance and resilience = the 2 stability concepts
What is resistance stability?
the tendency for the system to remain the same when subject to a disturbance; related to adaptations which provide resistance to disturbances
Simple words: the ability of a system to resist change
What is resilience stability?
the tendency to re-establish a former state after a change has occurred; ecosystem bounces back
Simple words: ability of a system to return to its original state
How can resistance stability be measured in an ecosystem?
Deviations from a normal operating range of ecosystem function = measure of resistance.
How can resilience stability be measured in an ecosystem?
time required to recover = measure of resilience
How could one forest be more resistant than another?
Certain tree species found in one forest could be more adapted to disturbances and be more resistant to them
Can resistance and resilience be decoupled?
Yes: high resistance, low resilience, and vice versa
In a figure adapted from Odum and Barrett 2005’s study, how was resistance and resilience measured?
ecosystem function varying through time, such as productivity, you will see fluctuations throughout time. Drop in NPP for a few years.
Possible exam question: what are some other ecosystem functions (other than NPP) that can be measured to determine the functioning of an ecosystem?
1) decomposition measured by rate of mineralization
2) microbial respiration rate -> decomp
3) pollinator visitation rates?
4) trophic interactions -> measured in herbivore biomass or consumption rates
Define stability in regards to ecosystems?
ability to stay within a normal range, so resistance and resilience push back against disturbance which would throw the ecosystem out of balance
What factors other than “feedback loops” are involved in the stability of ecosystem function?
Biodiversity
What was the first person to note that diversity influences ecosystem function?
Darwin
What did Charles Elton propose in regards to biodiversity and ecosystem functioning?
Charles Elton proposed that diversity is a buffer to ecosystem change = effect niche idea
What is the “effect niche” of a species idea proposed by Charles Elton?
It is a definition of niche that focuses on the “role” that species play within an ecosystem
What is the The diversity-stability (insurance) hypothesis?
It assumes that different species play different functions within the ecosystem, so high diversity should provide insurance against local extinction following disturbance; if extirpation does occur, there are more species to fill that ecological role
What was the most influential experiment for the past 40 years?
Experiment by Dave Tilman and Downing in 1993 where they created 400 plots with different #s of plant species
Who did the Cedar Creek experiment?
Dave Tilman and Downing in 1993 with hundreds of plant plots with different #s of species, replicated at a high degree
What were the results of Dave Tilman and Downing’s Cedar Creek Experiment?
Measured functioning by biomass before and after a drought. Results indicated that high diversity promotes stability in the face of disturbance. This is indicated by the fact that all plots with low species richness are further from the 0 line indicating that there was a change between initial and final biomass.
In Dave Tilman and Downing’s Cedar Creek Experiment, what does the 0 line indicate (dotted line)?
near 0 line means there is no change = definition of resistance and stability. Away from 0 = less stability/resistance. Gaining or losing biomass suggests instability!
In Dave Tilman and Downing’s Cedar Creek Experiment, what does the width of the error bars indicate?
between the error bars = # of replications
Width of error bars = much larger when there’s less data points/replicates because if you have one weird value over 20 values, than the variance is smaller, whereas if you only have a few samples and 1 is quite different from the others, the error will be larger and you’ll be less confident in the average values
What are Alternative stable states by Holling 1973?
non-transitory states that arise when ecosystems are disturbed past a critical threshold and follow a path that does not restore them. Ecosystems may have more than 1 stable state. If a disturbance occurs, it may perturb the system and if it’s strong enough, it may shift the system into a new state
When did theoretical studies of the diversity-stability concept emerge?
in the 70s and ecologists eventually started to question its merits
What is the The biodiversity-ecosystem functioning (BEF) hypothesis?
This hypothesis posits that ecosystems with more species are likely to not only increase in stability, but also maximize ecosystem function (e.g., productivity)
What were the results of David Tilman’s 7-year study on the functional response of grasslands to varying species richness?
More species in an ecosystem, the more efficient the ecosystem; more species = more productivity. As the # of species increases, the total biomass also increases
Which hypothesis did David Tilman’s 7-year study on the functional response of grasslands to varying species richness, support?
Supported BEF hypothesis: diversity provides stability in face of disturbance, but diversity also promotes ecosystem function
Possible exam question: If you plug phylogenetic diversity in the x-axis in the graph produced by David Tilman’s study on functional response of grasslands to varying species richness, will the relationship get stronger and more linear?
YES because Phylogenetic diversity would be good for quantifying the # of functions fulfilled in your community: tropical niche conservatism; because it’s difficult to evolve new niches, typically 2 species close in the phylogenetic tree will have similar traits (less time since divergence) and therefore, occupy similar functions. So more phylogenetic diversity = more functions which would lead to more productivity
Why do we have a more productive and efficient ecosystem when there are more species?
more species supports niche complementarity: ecosystems will optimize resource use the more species are present with differing and complementary of niches -> creating synergies: altogether species have higher productivity than when they’re alone.
What is a synergy?
Once all the niches are filled, it creates a synergy; all together the species have higher productivity than when they’re alone. The whole is greater than the sum of its parts
Using species richness to determine productivity creates what problem?
This makes the assumption that each species play different roles and that there is a little functional redundancy, however, due to niche conservatism, species have a hard time diverging, so species close in phylogeny will likely have similar traits and play similar roles
Why is the the role that species richness plays on stability debated?
Because it assumes singularity: with each species added, you add a new function, however, we know that there is redundancy especially among closely phylogenetically related species
What are the 3 ways diversity and ecosystem function may be related Adapted from Naeem and Wright 2003?
1) functional redundancy: ecosystem function increases with diversity, reaching a plateau as (Eltonian) niches are filled
2) Singularity (rivet model): each species has a unique role, this declines once non-native species are introduced
3) Keystone
When would species richness and ecosystem by a positive linear relationship?
Species richness should be positively and linearly related to ecosystem function, only if there is no functional redundancy, this is bc complementarity depends on species filling different niches
What are the 3 biodiversity dimensions?
1) species richness: the # of species in a community (a.k.a. taxonomic richness). PROBLEM: All species are equally different. Each species added is adding a new function, but that’s not always true.
2) Functional richness: the # of ecosystem functions played by species in a community -> ex: functional groups (above). PROBLEM: don’t know if you measured all the traits that are relevant to quantifying functional diversity
3) Phylogenetic richness: the amount of evolutionary history represented by species in a community (i.e. total amount of branch length from the phylogenetic tree). Once you have a phylogeny, then you can quantify easily the phylogenetic diversity which will work better than species richness since it considers that 2 species close in phylogeny will likely be close in the functional role they play
Out of the 3 biodiversity dimensions, which would be the best to quantify the relationship between ecosystem function and the # of niches being filled/# of functions?
Phylogenetic richness: the amount of evolutionary history represented by species in a community, good since it considers that 2 species close in phylogeny will likely be close in the functional role they play instead of assuming that each new species = new function
In Thompson et al. 2019’s figure, which biodiversity dimension would be good for quantifying the # of functions fulfilled in the community?
Phylogenetic diversity: related to tropical niche conservatism hypothesis bc it’s difficult to evolve to fit into new niches, typically 2 species close in the phylogenetic tree will have similar traits (less time since divergence) and therefore, occupy similar functions. Better than functional diversity because it makes no assumption which traits might matter
In Cadotte et al. 2008’s study where they recreated Tilaman’s experiment and manipulated the # of functional groups and phylogenetic diversity in the plots, what were the results; which is the best for predicting productivity?
Turns out when you look at the R^2 value for a, b, and c, phylogenetic diversity (c) has the best R^2 value: R^2 method: varies between 0-1 and closer to 1 is better. If it’s 1, then the x-variable predicts perfectly the y-variable. The more aligned the dots are with the line = better ability to predict and better R^2 value
What is the R^2 method?
varies between 0-1 and closer to 1 is better. If it’s 1, then the x-variable predicts perfectly the y-variable. The more aligned the dots are with the line = better ability to predict and better R^2 value
Which approaches can be used to test BEF?
Quantify the phylogenetic diversity of trees in a plot and quantify the biomass in the plot and do a regression analysis to analyze their relationship, then you replicate the plot hundreds of times
What’s the problem with observational studies?
Don’t know what other variables correlate with biomass as well. Whereas, in experimental studies, you manipulate all variables except the one you want to measure.
Not all experiments on biodiversity-productivity were field-based, some were conducted in artificial systems of varying scales: what are 2 examples of smaller scale experiments?
1) microcosm
2) mesocosm
What is a microcosm?
a small self-contained system. It’s an approach where you control everything except the thing being measured
What is one pro and one con about microcosm experiments?
1) Pro: get answers quickly if the organism being studied has fast reproductive rate
2) Con: we don’t know if all the manipulated conditions can actually be related to nature bc it’s a controlled experiment, and it’s small so we don’t know if it can be up-scaled and applied to real world
What’s a mesocosm?
a large self-contained system (field experiment enclosure). Same level of control as microcosm, but more natural conditions and more at a scale found in nature
What is a pro and a con about mesocosm experiments?
1) Pro: same level of control as microcosm, but more natural conditions and more on a scale found in nature. Cattle tanks led to the most influential experiments recently
2) Con: they can get recolonized by the nearby environment, so you can’t run them too long or else the containers will sync in a way -> hard to relate to natural systems since they can only run for a few months
Possible exam question: Can you think of a manipulative experiment you could do in a mesocosm to test BEF?
In cattle tanks, put a variety of phylogenetically diverse decomposers such as fungi, N-fixing bacteria, and earthworms in a many different tanks. In other tanks, put only close phylogenetically related decomposers to act as a control (less functional diversity). Input decomposable material like leaf litter and replicate many times in different conditions with disturbances such as drought. Then measure the carbon biomass in and compare the 2 types of cattle tanks to see which tanks have less carbon biomass.
Possible exam question: Can you think of an observational study you could conduct to test BEF?
Create plots of same size across grasslands and record the species composition and calculate the phylogenetic diversity in each plots. Observe and record the plant biomass over the course of different conditions and different disturbances and compare plots that have less phylogenetic diversity to plots with more phylogenetic diversity; look at resistance and resilience as well as productivity
What are biodiversity hotspots?
places where species richness is high and where species-wide extinction rates are high
Why were biodiversity hotspots proposed?
concept proposed as a way to decide where conservation should be a priority. Has both idea of high diversity areas and areas especially vulnerable to anthropogenic activities
How do you know if a species will likely go extinct soon?
Species that are vulnerable to anthropogenic activities such as habitat destruction and characteristics of species including specialists for either type of habitat or resource
What is one of the leading causes of species endangerment?
Conversion of tropical forests into agricultural land
What are 5 Ecological characteristics of species that makes them vulnerable to extinction; also make species prone to extinction outside of the tropics?
1) species with limited distribution (endemics)
2) Small and/or few pops
3) Species with small ecological niche breadth
4) species that require a large home range
5) Species which migrate seasonally
How are species with small ecological niche breadth possibly endemics?
if the organism is specialized to a habitat or resource and it’s only found in one location, they will be limited to that location
Why are organisms with large home ranges potentially at risk species?
Because a large home ranges means that the likelihood that no part of the range is under human disturbance is very unlikely. Additionally, it means the organism needs a lot of resources to do well, thus a large area to find those resources, and those resources could be depleted if the range is depleted
What is an example of a species at risk due to its large home range?
Wolves have a large home range (territory) and they are loyal to this territory and will remain there for 20 years. Wolves have a home range of approximately 500-800 m^2.
What is a home range?
The area that one organism needs daily, monthly or annually, to cover its needs. Characteristic of an individual
What is a geographic range?
The entire area globally that a species occupies. Characteristic of a species. Must distinguish between summer range and winter range for migratory species
Why are organisms that migrate seasonally at risk?
when you migrate, you rely on 2 habitats so you have double the chance that your habitat will be destroyed. Additionally, migratory animals are at risk while migrating.
Why are habitat specialists possibly at greater risk of extinction?
Habitat specialists are more at risk of extinction if their habitat is uncommon; also often means that you’re an endemic species of the habitat only exists in one area on the entire planet
Why are endemic species the first to go?
Endemic species means you’re only one area, so when their habitat experiences a disturbance, the whole species is destroyed. Also more likely to go extinct just by chance.
What are the 3 classifications for threatened species by the International Union for the Conservation of Nature (IUCN)?
1) Critically endangered species
2) Endangered species
3) Vulnerable species
Assigning a species to one of the IUCN categories requires having at least one of the 3 following types of info to build a predictive model:
1) observable decline in #s of individuals
2) The geographic area occupied by a species and the # of pops
3) the geographic area of individuals alive and the # of breeding individuals
Demographic info acquired is used to build models that make predictions on what 2 things?
1) The expected decline in the #s of individuals if current and projected trends in pop decline or if habitat degradation continues
2) The probability of the species going extinct in a certain # of years or generations: Used by IUCN to classify species endangerment level
What is a critically endangered species according to the IUCN?
species that have a 50% or greater probability of extinction within 10 years or 3 generations, whichever is longer
What’s an example of a Canadian species that’s critically endangered and why?
The American burying beetle, endangered due to habitat destruction
What is an endangered species according to the IUCN?
species that have a 20% probability of extinction within 20 years or 5 generations
What is an example of a Canadian endangered species and why is it now endangered?
The blue whale is endangered due to hunting and boat traffic. The home range of a blue whale is massive and they eat a massive amount of krill and so that increases the chance of them being hit by a boat. Additionally, they’re migratory species again increasing the chances of being hit by a boat
What is a vulnerable species according to the IUCN?
species that have a 10% or greater probability of extinction within 100 years
What is an example of a vulnerable Canadian species and why is it vulnerable?
The Box turtle: due to degradation, fragmentation and destruction of their habitat
Why are there more mammal and bird species that have been evaluated for risk of extinction by the IUCN?
There’s a strong bias in the type of organisms that we study and care more for. Mammals and birds, all named species were evaluated for level of endangerment. Insects are very under prioritized as the # of the species described was 1,000,000 and only 3000 were evaluated for risk of extinction
What tools have aided in the under prioritization of assessing insects for risk of extinction?
identification apps such as inaturalist
What is COSEWIC?
the Committee on the Status of Endangered Wildlife in Canada
What does COSEWIC do?
Using government and academic data COSEWIC makes decisions on whether a taxa should be listed under Canada’s Species at Risk Act, however, Canada puts more priority on COSEWIC than on international assessments so there can be discrepancies in the species being labelled as endangered
What is the most efficient conservation approach?
Find areas with high richness, lots of endemic species, and lots of threatened species. Then invest money in these areas
Jenkins et al. PNAS 2013: map shows where endemic species are clustered in the world; where is a large portion of threatened species and why?
A large proportion of threatened or “at risk” species are in the tropics because many tropical species are endemics, and worldwide rates of habitat destruction are highest in the tropics
What % of at risk species are endemics?
91%
Biodiversity hotspots are regions with what 3 characteristics?
1) species richness
2) endemism
3) level of threats
Possible exam question: Why are most endemics in the tropics? What makes them hotspots? Why do we think there are tons of endemics in these areas?
Most endemics are in the tropics because of tropical niche conservatism: the world was all tropics until temps started to change and temperate biomes were created. However, due to tropical niche conservatism, many species had trouble adapting, leading to many endemics and a large amount of species remaining in the tropics. Additionally, past climate-change velocity shows that tropics had less change and at a slower rate as well as more light and resources, allowing for more species to build up and be adapted to those conditions. Furthermore, what makes them hotspots is the fact that many species live there (high richness) including specialists which are endemics live in the tropics, and the rates of habitat destruction are the highest in the tropics which means they are at a high risk of extinction.
Where in the world have we found the most new species of birds, mammals, and amphibians and why?
mostly tropics and Australia (desert shrubland) because it’s a difficult area to access so they weren’t discovered prior to the 50s
How is Phylogenetic endemism is calculated?
It’s calculated as the phylogenetic dissimilarity between the focal region and all other regions
What do the colours demonstrate on the Map of phylogenetic endemism for terrestrial zoogeographic regions of the world based on data for 21,037 species of vertebrates?
Colours indicate the degree to which each regions differs from all other regions. Regions colored in dark red have the highest level of phylogenetic endemism. Dotted regions have no species records, and Antarctica is not included in the analyses.
What drives the high level of phylogenetic endemism in Australia?
most ancient mammals that are represented by 5 species of monotremes are all found in Australia making it highly phylogenetically different from all other regions
Should we give more value to places based on their evolutionary uniqueness because they represent history?
In Favor of Valuing Evolutionary Uniqueness:
1) Preserving Irreplaceable History
2) Intrinsic Value of Diversity
3) Functional Importance
What is the key anatomical difference b/w monotremes and other mammals?
monotreme means ‘single opening’ in Greek and comes from the fact that their urinary, defecatory, and reproductive systems all open into the a single duct = cloaca
What are 3 other unique features of monotremes?
1) lay eggs that are retained in mother for some time which actively provides the egg with nutrients
2) lactate, but have no defined nipples, excreting milk from mammary glands via openings in their skin
3) all species are long-lived with low reproductive rates and relatively long prolonged parental care of infants
What is the primary cause of species extinctions?
habitat destruction/habitat modification
What is the largest cause of land transformation?
Expansion of agricultural lands
EXAM QUESTION: Slash and burn deforestation in Brazil; what might be a negative consequence of slash and burn for the ecosystem?
When you burn a forest, you’re doing pyro-mineralization; turning organic form to a largely inorganic form by fire. If there’s a lot of rain, there could be a major loss of minerals due to leaching. The period between growing crops and slash and burning is a delicate period since if it rains before you plant crops, the minerals will leach into the ground and percolate into nearby streams = net loss. This will alter the community composition, favouring species that are adapted to modified habitat.
What are 2 examples of habitat destruction leading to threats to endemic species?
1) Madagascar: 90% of the original forest cover removed: Likely affected Lemurs which are endemic to Madagascar.
2) Borneo (partly owned by Malaysia and Indonesia): There is still primary forest left and Orangutans are endemic to Borneo
Prairie conservation (grasslands) failed in the 1990s, why?:
Main reason is because habitat destruction led to fragmentation which prevented the rescue effect into smaller and farther patches leading to extirpation
What are “reservoirs” of biodiversity?
Natural habitats within highly modified landscapes can act as “reservoirs” of biodiversity
What were the results of Kremen et al. 2002’s study that examined how the proximity of our forests to agricultural fields affect the diversity of bees that are pollinating the crops?
The diversity if pollinators visiting Organic near is greater = 8 compared to organic far = 4 and the error bars do not overlap signifying that the p-value is likely significant. There’s also more pollen in Organic near. Therefore, keeping crops near forests will increase the diversity and abundance of pollinators meaning greater pollination of the crops
What is a criticism on the design of Kremen et al. 2002’s study?
It’s missing a treatment: in theory, you would need another treatment such as conventional near in order to properly assess the impact of organic and conventional as well as the impact of near and far
How would Kremen et al. 2002’s study be applied to temperate regions since it was done in the tropics?
Solid evidence provided by multiple experiments around the world demonstrates the same results; replicates around the world in different regions can provide significance
Why should we preserve habitats for native bees if European honey bees can do the job?
Certain flowers such as those that require vibration to get pollen loose, can only be pollinated by bumble bees which vibrate whereas European honey bees cannot. Additionally, if honey bees were to go extinct, we would have no basically no large native pollinators
What is the most effective way to preserve biological diversity?
By protecting habitats and whole ecological communities; can also combine the reintroduction of extirpated species
What are 2 species that were extirpated and are being reintroduced?
1) swift fox into Canada
2) Atlantic Salmon
Why do larger areas generally contain more species than smaller areas?
Larger areas are often more heterogeneous and can provide for a greater variety of species
For conservation purposes, why is it best to protect as large of an area as possible?
1) Larger areas are often more heterogeneous and can provide for a greater variety of species
2) Larger organisms have larger home ranges, requiring larger areas
3) smaller patches have greater edge-to-area ratio that poses constraints for interior species: edge of a forest patch is more prone to wind and is exposed to more sun creating a different habitat
4) Species that are locally rare require a larger area to be present in large-enough numbers to sustain viable populations
5) Smaller patches can only support small pops which are more prone to stochastic extinction.
What is the sloss debate?
single large or several small protected areas
So is a single large or several small protected areas better?
Best approach might be case-specific: Protecting Caribou or wolves require large territories so they have to have larger patches. But smaller species require less room
What are the 2 most common ways of establishing protracted areas?
1) governmental action
2) purchase of lands by private individuals or non-governmental conservation organizations
The IUCN has developed a classification system for protected areas (I to VI): which are the most to least protected?
Categories I (strictly protected) through V can be considered as truly protected areas
Category VI protecting biodiversity is only one of several management objectives
What are the 3 most highly protected areas in Qc?
1) Biodiversity or Ecological Reserves
2) Natural Parks
3) Wildlife reserves
What is the goal of Biodiversity or Ecological Reserves in Qc?
goal is purely to protect, no infrastructure, no eco-tourism, only biologists/ecologists
What is the goal of national parks in Qc?
goal is purely to protect, but infrastructure and eco-tourism are present; camping, hiking and it plays the purpose of educating people about protecting biodiversity (intrinsic value)
What is the goal of wildlife reserves in Qc?
Goal is to protect, but controlled exploitation of natural resources occurs (timber harvest, fishing, hunting)
How much has CO2 concentrations increased over the past 1000 years?
by 25%
When did CO2 concentrations start to rise exponentially?
CO2 concentrations have risen exponentially since the mid-19th century, after the onset of the Industrial Revolution (combustion of fossil fuels)
What % of CO2 emissions comes from burning fossil duels from developed countries?
70%: Of this, the US accounts for more than 22%!
What were the results of experiments done at the Duke Experimental Forest that were geared towards understanding how an increase in the amount of CO2 can affect communities?
Towers that released CO2 in Duke experimental forest showed that CO2 can accelerate net primary productivity because NPP has to do with rates of photosynthesis. So by inputting a lot of Carbon, plants have more things to perform photosynthesis with and convert into their tissue
What’s the problem with the CO2 experiments done in Duke Experimental Forest?
It’s extremely expensive to build these experiments, so with a sample of 3 or 4, it’s difficult to come to a conclusion; if one plot acts differently from the rest, it’s hard to derive a conclusion. Because there’s a global network of these carbon tower experiments across the globe, we can now derive a proper conclusion.
The larger the scale of the experiment, the lower the replication
What was the hottest year since temp global records began in 1850 and how much above average was it?
2023 at 1.18 C above the 20th-century average of 13.9 C
What’s wrong the the models that predict future global temps?
many stochastic processes dictates processes of nature and because of this, all of the predictive models use the part of nature that’s deterministic making them less accurate
What have General Circulation Models (GCMs) been developed for?
have been developed to help scientists determine how increasing concentrations of greenhouse gases may influence large-scale patterns of global climate
Although GCMs from different research institutions differ in their predictions, certain patterns consistently emerge, what are these 3 common patterns among GCMs?
1) predict an increase in the average global temp and precipitation
2) expect warming to be the greatest during the winter months in the northern latitude
3) predict increase in variability of climate (e.g., more storms and hurricanes)
Climate influences what 7 things?
1) water availability
2) physiological and behavioral responses of organisms
3) birth, death, and growth rates of pops
4) relative competitive abilities of species
5) community structure
6) productivity
7) cycling of nutrients
What is the CC influence which research is currently focused on?
the response of individuals, pops, communities, and ecosystems to greenhouse warming
What are 2 main approaches to study climate change effects?
1) Modeling
2) Experiments
Why are CC models useful?
can help predict where species will be in the future using their range and predicting where their future range will be based on temps
What type of simplistic, easy-to-use, models do we rely on to forecast future distributions of species?
Environmental niche models (ENMs)
What do ENMs use to predict distributions of species in the future?
ENMs use the correlation between species distributions and climate today, to forecast what it will be in the future
Why are ENMs often questioned in their accuracy?
Often fail to account for the influence of dispersal limitations (hard to predict bc stochastic) and biotic interactions (competition)
What did David Currie do to try and predict future range of species with CC?
He used environmental niche models to create range maps for birds and mammals in NA and then looked at the range overlap in each grid cell to know the species richness. He projected into the future using future climate models to determine the range of mammals and birds in the future. Then he then looked at the species richness by looking at overlap in grid cells in the new range map. Predicted that species will move North.
What are some experiments done to look at the influences of CC?
Open top chamber experiments (small greenhouses) mostly done in the arctic bc they need an open area to see how ecosystem function will change when heating up the soil.
What does the international tundra experiment (ITEX) aim to understand?
aims to understand the potential impact of warming at high latitudes on tundra ecosystems
What were the results of International Tundra Experiment (ITEX) that used open top chambers?
Saw more reproduction and growth in plant communities as they were warmed, and there was no change in community composition suggesting resilience
Why is Holt unconvinced by the results of the international tundra experiment which suggested resilience of communities in the face of warming?
Because this experiment doesn’t observe how immigration and emigration will change with an increase in temp so of course there wasn’t a change in composition
What will occur due to the shift of species’ distributions with climate change?
The collective shifts in individual species’ distributions will change regional patterns of species diversity: hard to predict how this will change
What do Biogeographical models that relate the distribution of whole-ecosystems due to climate lack to take into account?
All of these models don’t take into account the ability of species to evolve. So it could be that the niche of species could evolve.
What are the 3 options for species under the effects of climate change?
1) migrate
2) adapt
3) die
IMPORTANT: What were the results of Moritz, C. et al. 2008’s study that focused on how recent climate change has affected mammals along an elevational gradient (bottom of mountain to top)?
They compared current distribution to historical distribution for 3 species of squirrels:
1) Tamias almpinus: Black line = result of distribution model in the past: predicted that they peaked in abundance at about 2700m. Red line = result of distribution model currently: predicts that their abundance peaks at 3500m
2) Neotoma cinera: (1) they migrated downward, the peak of distribution used to be higher compared to now. (2) Probability of finding the species in general decreased demonstrating that there was a species collapse. (3) They used to be found at a wide variety of elevations, but they are currently only found at one elevation: Elevational Range Contraction
3) Peromyscus truei: (1) An up slope shift; peak of distribution used to be around 500m now it’s around 1000m. (2) Population collapse; probability of finding them anywhere has decreased. (3) Distributional elevational range increased
conclusion: difficult to predict the range of species due to climate change
What are the results of predictions made by Environment Canada with a doubling of CO2 levels?
would cause major shifts in the ecoclimatic provinces and their associated vegetation by 2050. Predictions (a lot of them are based on problematic models that are exaggerated):
Arctic and Sub-Arctic = decline by 20%
Boreal = decline by 14%
Grasslands = increase by 15%
Semi-deserts = increase by 2%
