Prelim 3 Flashcards
bio/eco centric interest in biodiversity
intrinsic value, consequences for sustainability of communities and ecosystems
Anthropocentric interest in biodiversity
practical consequences of the loss of diversity for humans (including inspiration)
Elton’s observation of biodiversity in communities
simple communities are more easily upset than richer ones
taxonomic scales of diversity
- species (all are equal)
- functional groups (among species)
- phylogenetic (among species)
- genotypes (within species)
the narrower the resource partitioning, the (……) the number of species can exist
greater
mechanisms maintaining local diversity
- microhabitat partitioning
- food-type partitioning
- temporal partitioning
complementarity
as diversity increases, there will be greater community function, often through greater resource use (at a certain point there is redundancy in function)
ecosystem services derived from function include
- provision of materials
- cultural and psycho-spiritual well-being
- supporting services
- regulating services
positive effects of diversity
- drought resistance
- primary production
- resistance to invasion
- crop protection
positive effects of diversity: insurance effect
different species/genotypes/functional groups do better under different conditions
positive effects of diversity: negative covariance effect
in stressful environments, when one does well, others suffer
positive effects of diversity:
emergent/interaction effects
those benefits of diversity that cannot be predicted by species traits, but emerge from diversity per se, or interactions among the species
disturbance
a relatively discrete event in time and space that changes the structure of species composition, resource availability, and the physical environment
succession
a gradual change in community structure and ecosystem function over time, initiated by a disturbance
secondary succession
succession after disturbance that kills most species, but leaves behind some species, propagules (seedbank), or organic matter from prior ecosystem (post fire, hurricane, ice storm, logging, agriculture)
primary succession
succession on newly exposed mineral substrate, or after disturbances that remove virtually all traces of the prior ecosystem (living species and organic matter)
(lava flows, landslides, or after glacial melting)
chronosequence
a group of related communities that differ in development due to differences in age (space for time substitution)
mechanisms of succession: facilitation
one species helps the other species grow after a disturbance….early species pave the way for later ones
mechanisms of succession:
inhibition
once a colonist becomes established, it inhibits growth of subsequent arrivals by monopolizing space/resources
mechanisms of succession:
tolerance
late arriving species tolerate the presence of early species and grow despite the presence of early species because they are better competitors
characteristics of early successional plants
many seeds, small seed size, low root:shoot ratio, fast growth rate, small mature size, wind seed dispersal
characteristics of late successional plants
few seeds, large seed size, high root:shoot ratio, slow growth rate, large mature size, animal seed dispersal
pioneer community/early species
the first community, in a successional sequence of communities, to be established following a disturbance
climax community/late species
a community that occurs late in succession whose populations remain stable until disrupted by disturbance
intermediate disturbance hypothesis
at low frequency of disturbance/small disturbance, species diversity is low because of competitive exclusion (K species dominate). At high frequency of disturbance/large disturbance, few taxa can tolerate environment and r species dominate. in the middle, mix of r and K and a lot of species diversity
island biogeography: immigration rate
immigration rate declines as the number of species on the island approaches the number of species in the mainland species pool
island biogeography: extinction rate
extinction rates increase as the number of species on the island approaches the number of species in the mainland species pool
distance from mainland
as distinct from mainland increases, the equilibrium number of species on the island decreases
island size
as island size increases, the equilibrium number of species increases
immigration rates are expected to be _______for islands that are close to the mainland source pool
higher
extinction rates are expected to be ______for larger islands than smaller islands
lower
3 hypotheses of distributions of organisms
- convergence
- vicariance
- dispersal
vicariance
splitting of one contiguous population into two or more ranges, and often results from geologic events
latitudinal patterns of species diversity
species richness tends to increase towards equator
hypothesis for latitudinal gradient: habitat diversity and area and stable climate
area is large and climate is stable in tropics, promoting speciation and reducing extinction
hypothesis for latitudinal gradient: diversification rate
evolutionary rate (and mutation) is faster, due to higher temperatures and light effects on metabolism
hypothesis for latitudinal gradient: diversification time
historically the trophic covered more of earth’s surface. glaciation disproportionately impacted temperate areas. temperate species may be phylogenetically derived from tropical ancestors
hypothesis for latitudinal gradient: productivity promotes diversity
productivity (production of biomass) is highest in the tropics, and this estimates energy available for the whole community
umbrella species
cover ecosystems (conservation of umbrella species conserves others)
charismatic species
societal attention
8 biomes
desert, taiga, temperate forest, temperate grassland, tropical rain forest, tropical savanna, tropical seasonal forest, tundra
convergent evolution
selective pressure of climate leading to similar evolutionary outcomes, not necessary any common taxonomic/genetic background
pool/stock units
g/m^2
flux rate
g m^-2 y^-1
Gross primary production (GPP)
total rate of CO2 fixed into carbohydrate per unit time (total ecosystem photosynthesis)
autotroph respiration (RA)
respiration by autotrophs
net primary production (NPP)
net rate of organic matter fixation by autotrophs
NPP=GPP-RA
represents the total amount of new organic matter available for consumption by higher trophic levels
heterotroph respiration (RH)
respiration by heterotrophs
Net ecosystem production (NEP)
net rate of organic matter accumulation in an ecosystem
NEP=NPP-RH
NEP=GPP-RA-RH
eddy covariance
measures fluxes of CO2 going into and out from the top of a plant canopy
NEP=GPP-Re
which biomes display the greatest NPP per unit area?
tropics forest, wetlands, algal bed and reef, temperate forest
which biomes display the greatest NPP in Total earth?
tropical forest, open ocean, temperate forest
terrestrial NPP increases with
actual evapotranspiration
terrestrial and ocean NPP values _____
are similar
where do nutrients needed for primary production come from
recycled within ecosystem, small part comes from atmospheric deposition and newly added via weathering
plants limit their nutrient loss with
- reducing tissue turnover
- nutrient resorption–translocation
biological N fixation
inputs: stable N2 gas (inorganic)
outputs: organic N that can be absorbed by plants
denitrification
input: NO3- (nitrate)
output: N2
byproduct: N2O (greenhouse gas)
nitrification
input: NH4+ (ammonium)
output: NO3- (nitrate)
byproduct: (NO2)
bacterially driven process
mineralization
- mineralization by bacteria makes N bio-available
- recycling of nitrogen always greater than rate of N fixation
problems with N cycle
creation of reactive biologically available forms of nitrogen cause acidification and fertilization
eutrophication steps
1) more N=greater biomass to facilitate dominant species
2) greater biomass=more dead matter
3) heterotrophic consumption is amplified, resulting in higher CO2
4) low O2 entering hypoxia, bad for animals
phosphorus cycle
no gas transfers, phosphorus stays in same oxidation-reduction state
