Production Ecology Flashcards
1
Q
Define productivity
A
the accumulation of matter and energy in biomass in terms of carbon
ie., carbon is what is being exchanged/accumulated
2
Q
Define primary productivity
A
photosynthesis
the conversion of light (electromagnetic) energy into chemical energy in the form of reduced carbon compounds
3
Q
Define secondary productivity
A
When heterotrophs consume plant material and convert the energy (carbon) into their biomass
4
Q
What is photosynthesis?
A
the process of converting light energy from the sun into chemical energy through atmospheric CO2 fixation
6 CO2 + 6 H2O + light –> C6H12O6 (glucose) + 6 O2
5
Q
what is respiration?
A
the process that occurs in organisms to extract the energy fixed in the reduced (converted) carbon compounds
C6H12O6 + 6 O2 –> energy + 6 CO2 + 6 H2O
6
Q
What is GPP?
A
gross primary productivity = the total amount of fixed CO2 by plants via photosynthesis by an ECOSYSTEM (large scale)
7
Q
What is NPP?
A
net primary productivity = the total amount of fixed CO2 via photosynthesis MINUS plant respiration
aka the biomass increment
8
Q
What measurement represents the biomass increment?
A
NPP
9
Q
What is NEP?
A
net ecosystem productivity = the total amount of fixed CO2 via photosynthesis MINUS the total ecosystem respiration
aka the total carbon or biomass gained for an ecosystem
10
Q
What measurement of productivity represents the total carbon or biomass gained for ecosystem ?
A
NEP
11
Q
How abundant is carbon in relation to other elements in the universe?
A
it’s the 4th most abundant
12
Q
T or F: C is the ‘backbone of life’
A
true
13
Q
What components of the universe are involved in the global carbon cycle/biogeochemical cycle?
A
biosphere
pedosphere (skin of the earth)
geosphere
hydrosphere
atmosphere
and is the overall exchange of energy
14
Q
What are the 2 elements of the carbon cycle?
A
fast and slow
15
Q
Describe the slow carbon cycle briefly
A
takes 100-200 my to cycle C between the rocks, ocean, and atmosphere and moves a much smaller amount of carbon (10-100 Mt annually)
16
Q
Describe the fast carbon cycle
A
takes ~90 yrs to move C through the biosphere (much shorter than slow)
moves 1000-100000 Mt of C per year (much more than slow)
C is fixed by autotrophs via photosynthesis
C is returned to atmosphere from respiration or fire
forests are key to this cycle
17
Q
How are forests related to the fast carbon cycle?
A
45% of carbon stored on land is stored in forests
18
Q
Where is the largest terrestrial natural storage sink of carbon on earth?
A
forests contain more C in biomass and soils than the atmosphere
19
Q
What % of the Earth’s terrestrial area do forests cover?
A
~30%
20
Q
What % of terrestrial GPP do forests produce? how much of the plant biomass on earth?
A
75% of GPP
80% of plant biomass on earth
21
Q
Which forest types contain the most biomass? explain
A
tropical, moist intact forests
especially tropical peatland and mangroves due to their large storage of C in roots and soils
22
Q
Which forest types have the lowest biomass? why?
A
boreal forests due to their low density of aboveground plant material
23
Q
How do tropical peatlands and mangroves have such high carbon density if they’re tree biomass is low?
A
their roots and soils contain a high density of C even if the aboveground doesn’t
24
Q
How much of the GPP does autotrophic respiration release? how does this affect NPP?
A
at least 50% of the CO2 fixed by plants is lost through respiration
so NPP = ~50% of GPP because P - R = NPP
25
What is the largest long term storage form of carbon in forests?
soil organic matter
26
What happens to most of the carbon fixed by primary producers?
lost as respiration from primary producers and heterotrophs and decomposers
27
~ how much energy is lost between trophic levels as respiration/heat?
90%
28
Of the NPP (CO2 fixed - respiration from plants), how much is consumed by heterotrophs? what happens to the rest?
~3% moves through the trophic levels
the rest is lost from the plant as litter and moves into the decomposition food chain
29
What contributes to the NEP?
litter and soil OM accumulation + live biomass accumulation of plants + consumers
30
WHat are the 2 largest components of NEP in forests?
litter and soil OM accumulation + live biomass accumulation of plants
31
T or F: plant respiration has a large influence on NEP - explain
true
deciduous forests have high plant biomass and therefore a high GPP, but because there's so many plants, they have a high respiration cost = similar NEP to oak-pine forests that have much less plant biomass and lower GPP
32
explain why a deciduous forest with high plant biomass might have a similar NPP to an oak-pine forest with less plant biomass?
respiration!
the deciduous forest has more plants and a higher GPP but also that requires higher respiration rates = lower NPP
the oak-pine forest has less plants and lower GPP, less plants require lower respiration rates = higher NPP
these end up being relatively similar
33
What are the 2 components of total plant respiration?
respiration for construction and respiration for maintenance
34
How does NPP vary between ecosystems?
temperature and preciptation
35
Where is NPP highest globally?
closer to the equator
36
How does the NPP of forests compare to aquatic ecosystems?
NPP of forests are relatively high due to the generally large biomasses but some aquatic ecosystems have high NPP too (algal beds, reefs, estuaries)
37
Which terrestrial ecosystems have the highest NPP? the lowest?
swamps + marshes have highest
then tropical forests (highest forest)
then temperate forests
then boreal forests (lowest forest)
lowest overall is desert scrub
38
What infleunces the differences in ABOVEground NPP amongst forest types?
leaf area
water availability
nutrient availability
temperature
length of growing season
39
Why might coniferous forests have high NPPs comparable to tropical moist forests?
high leaf area of conifers
40
In what 5 pools does forest NEP accumulate in biomass?
1. above + belowground tree and plant tissues
2. above and belowground heterotrophic organism tissues
3. woody debris
4. forest floor
5. mineral soil
41
Define biomass
the dry mass of living organisms and dead OM
42
How does the total distribution of biomass (between the 5 pools) vary for a boreal forest vs. a coniferous temperate vs. a deciduous temperate vs. a tropical wet forest?
boreal: most biomass is in the mineral soil (belowground) because of the VERY slow decomposition rate
coniferous temperate: most of the biomass is in the overstorey (trees) because of the very large and abundant trees
deciduous temp: almost an even distribution between overstory and mineral soil
tropical: huge proportion of the biomass is stored in the overstorey (but still a larger amount stored in soil than others) due to the rapid decomposition
43
Which forest ecosystems allocate the highest amount of NPP to roots?
boreal and tropical deciduous
44
Which forest ecosystems allocate the lowest amount of NPP to roots?
coniferous temperate and tropical evergreen (wet)
45
As PP increases, how does the allocation of NPP to different tissue types change?
generally, foliage remains similar
boles + branches decrease
and belowground (roots) decreases
46
How much of NEP is belowground in a forest?
~75%
47
What are the 5 levels of a trophic food chain?
1 = primary producer
2 = primary consumer (herbivores)
3 = secondary consumer (consume herbivores)
4 = tertiary consumer (secondary carnivores)
5 = apex predators
48
Describe a food or trophic chain
a simplified sequence of how energy and nutrients are transferred within an ecosystem
49
What is a food or trophic WEB?
an interconnected network of feeding relationships (ie., network of trophic chains)
50
Where do decomposers fit into food chains?
at the end? because everything ends up being decomposed eventually?
along the side?
51
what is the 10% rule?
~10% of the energy consumed at each trophic level is assimilated into the organism that consumed the other
~90% is lost as heat/respiration for metabolism and growth
52
Which trophic levels help control lower level populations?
tertiary and apex predators
ex. wolves, eagles, weasels
53
What is the food chain length based on? what does this measurement tell us?
the number of links between a trophic consumer and the bottom of the web
tells us about the transfer of energy and an indicator of ecological structure
54
What is an energy/trophic/ecological pyramid?
a diagram of the flow of energy at each trophic level for an ecosystem
helps to demonstrate ecological efficiency at transferrin energy between trophic levels (~10% rule)
55
How is an energy pyramid created?
based on a biomass pyramid
56
Describe and compare the biomass pyramid for a pine forest's detrital food web vs. grazing food web and the corresponding energy flow pyramids
Biomass:
- detrital: large base of PP, significantly smaller going up the trophic levels = very small biomass in fungi, soil herbivores
- grazing: small leaf biomass and VERY small up the chain
energy flow:
- MASSIVE base of energy
- detrital: huge amounts of energy in the trophic levels
- grazing: huge loss of energy between PP and consumers
===== although detritivores make up a small portion of the biomass in a pine forest, they play a huge role in energy transfer
57
How are biomass pyramids infleunced at each level?
by the size of the organisms at each level
ex. because trees are huge, the PP biomass level of forests is usually very large, but as consumers (ex. insects) decrease in size, the pyramid steeply drops off
58
What is the best model to convey energy flow? why?
energy/carbon flow models
biomass pyramids don't convey the flux of energy and miss a lot of detail; energy flow pyramids are based off the biomass ones
59
T or F: size and trophic position are strongly correlated in forest ecosystems
false - trees are massive but are PP
60
Explain the forest energy/carbon flow model
high NPP = large biomass of plants
large amount of NPP from plants is transferred to detritus, some assimilated by herbivores
this supports a huge density of decomposers which pass on a fairly large amount of energy to predators
the small amount assimilated by herbivores supports a small amount of herbivores which pass on a relatively high amount to predators
61
Where are the pools of C in the energy flow model for forests?
largest in autotrophs then detritus then decomposers then predators and smallest in herbivores
62
What creates competition between species?
when species are in the same trophic level their niches may overlap if they use the same resource (if the resource is not limiting)
63
What may plants be competing for?
light
nutrients
water
64
What reduces direct interspecific competition?
territoriality and habitat selection (birds, mammals)
niche diversification (use same resource at different times) - ex. nocturnal v. diurnal
specialization for timing of food, type of food, place of feeding etc.
65
What is the potential end result of diversification?
a keystone species that has a unique function
66
What is a point of vulnerability in an ecosystem? why?
a keystone species because they perform a specific role which if lost, that function is also lost from the ecosystem
67
What light wavelengths are photosynthetically active for plants (PAR)?
400-700 nm (visible wavelength spectrum) but specifically 400 and 750 nm
68
Of the total incident energy (sunlight) on a leaf, how much is converted into a carbohydrate via photosynthesis?
~5%
69
What influences the % of incident PAR energy (sunlight hitting the leaf) that is captured by plants?
photosynthetic efficiency
70
What is photosynthetic efficiency?
Ps efficiency = NPP / incident PAR
how well a plant leaf can capture PAR energy and convert it into carbohydrates
71
What determines Ps efficiency?
available resources = light, water, nutrients
72
What does the proportion of PAR incident that is captured in a forest depend on?
plant density
leaf surface area per plant
leaf Ps efficiency
73
What is the LAI?
the leaf area index aka = plant density + leaf surface area
LAI = project leaf surface area / unit ground surface area
74
What determines LAI?
the available resources = light, water, nutrients (and the species type)
75
How are LAI and Ps efficiency related to resource availability?
as resources increase, both increase but LAI increases faster
76
How much of the captured energy in forests is lost to autotrophic respiration?
30-70%
77
What factors influence autotrophic respiration?
temperature
plant size
growth rate
health
78
What are the global trends for autotrophic R?
losses increase towards equator (warmer days + nights) = higher R rates
79
What are the trends for stand age and autotrophic R? How does this affect NPP?
R losses increase with stand age (higher R rates) causing NPP to decline
stand age = increased woody tissue = a lot more tissue is non-photosynthetic but still requires maintenance
80
Why would stand age cause increased respiration losses?
older trees have more woody tissues which do do not do photosynthesis but still require maintenance
81
What does the alternative hypothesis state about how GPP, NPP and R are related to forest stand age?
all are declining
NPP declines because GPP is declining due to increasing age
more water stress?
nutrient allocation to more places?
82
What form is most NPP lost in forests?
as litter (mostly leaf litter)
83
How does litter loss trend globally?
increased litter loss towards equator
high growth = high litter loss
less litter is produced and lost in latitudes further from the equator where temperatures are cooler and soils are less rich in nutrients
84
Where does most of the biomass turnover occur in most forests (above or belowground)?
belowground
85
How does fine root litter production compare to leaf litter production?
fine root litter can be 40-330% more than leaf litter production
significantly higher turnover
86
What is necromass?
dead organic matter in soils, litter, deadwood
87
Is carbon in forest necromass or biomass larger globally?
necromass is larger
can account for ~58% of an ecosystem's total carbon
88
How does the boreal forests necromass compare to temperate forests? tropical?
necromass in boreal >> temperate and tropical
temperate > tropical
89
T or F: often in forest ecosystems, the detritus food web is most of the post-producer energy flow
true!!
90
How do soil fauna increase the rate of decomposition? give examples of fauna
ex. worms, beetles, millipedes, springtails
degrade organic particles = increase SA
they remove wax and cuticles = easier to decompose
mix in organic particles into the mineral soil = increase moisture
91
After soil fauna break down the organic particles, what follows in the detrital food chain?
bacteria and fungal decay!
92
Why is bacterial decay faster than fungal?
bacteria love neutral pH and warm soils and can quickly decay high quality (angiosperm) litter but rely on soil fauna to first mix in the OM into the soil
fungi are good at decomposing in cold, acidic soils (slow) and more recalcitrant (lower quality) OM and can grow/reach OM without it being mixed into the soil
93
who eats bacteria and fungi?
micro-invertebrates
94
What is high quality litter?
LOW C:N ratio (more N per C) is easier to degrade
from angiosperms
95
What 7 factors affect decomposition rates?
temp
moisture
pH
oxygen
soil fauna
chemical characteristics of litter
physical characteristics of litter
these all affect abundance of fungi and bacteria
96
What is a LOW C:N ratio?
low N to C
25:1 or lower is optimal for decomposers
97
Why is wood and bark decomposition slow?
because only fungi can do it
and because the C:N ratio is super high (500:1) - Nitrogen is super limiting here
98
What are optimal conditions for decomposition?
5-80% water retention
2-40d C
proper aeration, not compacted or water logged
4-10 pH
low C:N ratio
99
How does decomposition vary globally?
fastest at equator
100
Where are forest floors the thickest, globally?
toward the poles (unless frequent fire) because of very SLOW decomposition
101
How does plant type influence decomposition rates?
different plants will have different litter quality (C:N ratios) which will affect decomposition rates
102
In what (general) ways might climate change effect forest productivity
changes to temperature, precipitation
seasonal shifts (frost delays, bud flush delays)
higher CO2 (improve water and N use)
disturbances (fires, floods, etc)
shifts in community structures - decomposition, transition from coniferous to deciduous?
103
Why might NPP rise with increased CO2?
increase of CO2 in atmosphere allows for increased CO2 fixation by plants
104
What kind of study designs were used to look at whether increased tree growth via CO2 fertilization can be sustained long term and be beneficial long term?
Free Air Carbon dioxide Enrichment (FACE) and Open Top studies to look at ecosystem level responses to experimentally increased CO2
105
How is tree growth effected by increased CO2?
increased carbon availability and/or
increased water uptake and use efficiency (plants don't have to open their stomata as wide or as long)
106
In the meta-analysis of FACE and OTC studies, what did they find for above and belowground biomass and growth responses to increased CO2?
biomass increased significantly for both AG and BG
both showed greater growth with higher N
107
Overall, how does increased CO2 affect the system?
increased plant growth = increased soil carbon input BUT
the effects of CO2 fertilization will be limited by nitrogen and will not be sustained because
when there's high N = soil C input > C mineralization loss and there's sequestration but
When N is limiting, the soil C input = the C mineralization adn there's no sequestration (normal conditions)
SO only when there's additional N or nutrients added to the system can N-fixers support high C sequestration
108
What are the advantages and disadvantages of monoculture forests?
adv:
- easier to maintain
- plant species with desirable characteristics to improve growth rate + quality of wood
- even aged, high density, accessible = high yields
- efficient, uniform
dis:
- soil productivity and fertility can decrease
- disruption of hydro cycles
- risks of disease, invasives, lower resilience/resistance to disturbances
- reduce biodiversity of ecosystem
109
What are the advantages and disadvantages of mixed-species forests?
adv:
- support greater biodiversity by creating more ecological niches
- more biodiversity = more productivity and stability
- more stable in response to disturbances and stresses (ex. resistance to fire or disease outbreak)
dis:
- lower tree growth
- lower species value
110
Is a mixed or monoculture forest generally more productive? why?
mixed! because they can provide more resources and stability = more productivity overall
111
in what situations will NPP be greater in a mixed stand than in a monoculture?
- more resources = more efficient use of environment
- mix of species is more stable against stresses
