E4 Flashcards
Succession
the temporal change in community structure through time, begins with disturbance
Henry Chandler Cowles
he studied ecological succession in the Indiana dunes of northwest Indiana
led to efforts to preserve the Indiana dunes
FE Clements
described plant succession
characteristics of disturbance
four factors
1. the magnitude of the physical force, such as the strength of the wind, or the heat of the fire
2. morphological characteristics of the organisms that influence their response to disturbance
3. the nature of the substrate (soil). Is the soil wet or dry, clay or sand
4. the amount of aboveground biomass accumulation and height of vegetation
frequency
the mean number of disturbances that occur within a particular time interval
return interval
the interval between disturbance events
if intervals are long or frequency is low, biomass accumulates and the intensity of the disturbance can be high
what is the impact of return interval
in some communities the return interval of disturbance is roughly proportional to the life span of the dominant organisms
in forest communities with trees that potentially live for several hundred years, return intervals of disturbance are shorter than the life span of the trees
framework for examining community dynamics
- The fundamental niche of a species acts as a primary constraint on its distribution and abundance
- species vary in their fundamental niches (environmental tolerances)
- Environmental conditions change in time and space
- the fundamental niche is modified by species interactions (realized niche)
logging began in Michigan in 1880s
logs were sent down rivers to be milled
the land was nude
-following the logging era farmers tired and failed on the land
-fires in the early 20 century burn up slash
-causing further soil loss
-clements viewed succession as a process involving several phases, to each of which he gave his own terminology
-succession began with the development of a bare site called nudation (disturbance)
-nudation was followed by migration, the arrival of propagules onto the area
-migration was followed by the establishments and the initial growth of vegetation
-the outcome of the process was the replacement of one plant community by another reaching a phase called stabilization
-ice contact stratified outwash
-impact on streams: without forest cover streams heated up and sand eroded into the streams. the gravel bottoms of the streams were smothered in sand
trout were introduced
the grayling went extinct
-most trees in Michigan today are managed maple/beech forests
dominance shift of overstay and understory pine, to hardwood
in the early stages of plant succession, shade-intolerant species come to dominant as a result of their high growth rates
shade-intolerant species overtop and shade the slower-growing, shade tolerant species
as time progresses and light levels decline below the canopy, seedlings of the shade-intolerant species cannot grow and survive in the shaded conditions
at this time, although shade-intolerant species dominate the canopy, no new individuals are being recruited into the populations
hardwood (shade tolerant species) are able to grow and take over
climax community
according to classical ecology theory, succession stops when the sere has arrived at an equilibrium or steady sate with the physical and biotic environment
at this point the community is stable and self-replicating
barring major disturbances, it will persist indefinitely
the end point of succession is climax
characteristics of climax
- the vegetation is tolerant of the environmental conditions it has imposed upon itself
- it has a wide diversity of species
- complex food chains
- well-developed spatial structure
- individuals in the climax stage are supposedly replaced by others of the same kind. Thus the species composition maintains equilibrium
- The climax view of succession was later modified by tansley and whittaker
serotiny
jack pine have seeds that remain in the cone for years awaiting a fire
the fire melts the resins that kept the cone sealed up
then the pine seeds are ready for the newly repaired ground of ash
frequency rolling plains
how frequently a fire burns over a given area, and its return rate is influenced by the occurrence of droughts, accumulation and flammability of fuel, the resulting intensity of the burn, and human interference
in NA, grasslands have fires every 3 years
the time was needed for sufficient mulch, dead stems, and leaves to accumulate
wind as a force of succession
wind shapes the canopies of trees exposed to prevailing winds, affects their growth, and uproots them from the ground
trees weakened by fungal disease, insect damage, lightning strikes and tropical forests trees carrying a heavy load of epiphytes in their crowns are candidates for wind throw
hurricanes
a powerful recurring event of high intensity but low frequency
hurricanes, especially those with wind speeds of 166km/hr and rainfall of 200mm have a devastating impact
impacts of wind is accentuated when strong winds accompany heavy snowfall that weighs down trees or heavy rains that soften the soil about the roots
cyclic replacement in an old-field community in Michigan
the bare areas at the bottom are invaded by moss
mosses are invaded by Canada bluegrass and dock
the accumulated dead leaves of these plants are covered by lichens that crowd out the grass
rain, frost, and wind destroy the lichens to start the cycle with bare ground again
“return to the same place in the same cycle”
chronoseres/ chronosequences
patterns of diversity through succession have been investigated by comparing datable sites within an area that are in a different stages of succession
allogenic environmental change
purely abiotic environmental (allogenic) change can produce patterns of succession over time scales ranging from days to millennia or longer
annual fluctuations in temp and precipitation will influence the relative growth responses of different species in a forest community, but they will have little influence on the general patterns of secondary succession
in contrast, shifts in environmental conditions that occur at periods as long or longer than the organism’s life span are likely to results in shifts in species dominance
primary succession
begins on sites that have never supported life
ex: rock outcrops and cliffs, sand dunes, and newly exposed glacial till
diversity increases with
age
secondary succession
where life has been before
soil and nutrients are present
type of ecological succession in which plants and animals recolonize a habitat after a major disturbance—such as a devastating flood, wildfire, landslide, lava flow, or human activity (e.g., farming or road or building construction)—significantly alters an area but has not rendered it completely lifeless.
secondary succession- farmer
old-field succession in the Piedmont of North Carolina
-a famed crop land is abandoned, the ground in claimed by crabgrass, whose seeds lying dormant in the soil, respond to light and moisture and germinate
-in late summer seeds horse weed ripen
-the following spring horse weed, claims the field over crabgrass
-by the third summer broomsedge a perennial bunchgrass, invades the field
about this pine seedlings, find room to grow in open places among the clumps of broomsedge invade the field
-within five years the pines are tall enough to shade out the broomsedge
-eventually hardwood species, such as oaks and ash, grow up through the pines and the pines die
-development of the hardwood forest continues as shade tolerant trees and shrubs fill the understory
autogenic change (self-generated)
one feature common to all plant succession is autogenic environmental change. In both primary and secondary succession, the colonization of an area by plants alters the environmental conditions
one clear example is the alteration of the light environment
influence of herbivores on community dynamics
herbivores modify community dynamics, directly and indirectly
by selecting certain plant species, herbivores directly influence mortality and recruitment, favoring the population the population growth of one species over another
moose on isle royale in Lake Superior selectively feed on the seedlings and saplings of deciduous hardwood tree species of aspen, birch, ash, and maple, ignoring the conifer species
long-term experiments using exclosures to exclude moose from certain areas have changed the community structure of the island. In the exclosures, the abundance of the deciduous hardwood species is much higher
degradative succession
succession that occurs on dead organic matter over a relatively short time-scale. Detritivores feed in sequence, each group releasing nutrients that are utilized by the next group in the sequence until the resources are exhausted.
shifting mosaic
the process of succession is never ending, brought about by the continuous processes of birth, growth, and death of individuals within the community
this view of succession suggests a shifting mosaic steady state
the community being composed of a mosaic of patches, each in a phase of successional development
A. thinenmann
introduced the idea of nutrient cycling, trophic feeding levels, and the trophic pyramid
producers and consumers terms
first law of thermodynamics
states that energy is neither created nor destroyed. Energy is simply converted from one form to another
second law of thermodynamics
states that when energy is transferred or transformed, part of the energy is lost as waste and cannot be passed on any further. The second law, theoretically, applies only to a closed system which the Earth is not
primary production
energy accumulation by plants is called production, because it is the first and most basic form of energy storage in an ecosystem
gross primary production (gpp)
all of the energy that is assimilated in photosynthesis
net primary production (npp)
energy remaining after respiration and stored. as organic matter
productivity is highest
in warm wet environments
energy allocations
net primary production represents the storage of organic matter in plant tissue in excess of respiration
a portion is allocated to growth, the buildup of components such as stems and leaves that promote further acquisition of energy and nutrients
Herbaceous plants
in perennials, once the plant is ready to flower, it diverts its production away from storage to production of flowers and seeds
in late spring and early summer, they produce more leaves that generate photosynthate, which is sent back to the roots to build up capital for next year’s blooms
woody plants
woody plants must invest their energy into woody tissue and roots
in the spring the tree draws on at least one-third of the reserves to get its new leaves started
a tree’s most expensive drain on its annual energy budget is the production of fruit
major food chains
within any ecosystem there are two major food chains, the grazing food chain and the detrital food chain (distinguished by their source of energy or food for the initial consumers)
grazing food chain
living plant tissues, are the primary source of energy for the initial consumers the herbivores
detrital food chain
the initial consumers, primarily bacteria and fungi, use dead organic matter, detritus, as their source of energy
Golly
carefully worked out a grazing food chain for old-field vegetation, meadow mice, and weasels
the mice are herbivores and weasels live mainly on mice
the vegetation converts about 1% of the solar energy into net production, or plant tissue
the mice consume about 2% of the plant food
the weasels eat about 31% of the mice
of the energy assimilated, the plants lose about 15% through respiration, the mice 68%, and the weasels 93%
the weasels use so much of their assimilated energy in maintenance that a carnivore preying on weasels could not exist
the major pathway of energy flow in littoral and terrestrial ecosystems
detrital food chains
interactions between food chains
grazer and detrital are combined to produce a generalized model of trophic structure
saprotroph
an organism that feeds on or derives nourishment from decaying organic matter
ex: mushrooms
supplementary food chains
parasites and scavengers
ecological pyramids
energy is transformed through the ecosystem by way of the grazing chains is reduced by a magnitude of 10 from one level to the next
aquatic pyramids
primary production- phytoplankton
planktonic algae have a short life cycle, multiply rapidly, accumulate little organic matter, and are heavily exploited by herbivorous zooplankton
standing crop is low
base of pyramid is much smaller than the structure it supports
dry soil
pull stem off
wet soil
pull entire plant and roots
more diversity
more productivity
overfishing
a main problem of overfishing is the “open access” nature of fisheries. Because there are no or few property rights there is a lack of incentive for fishermen to leave fish in the water
bycatch
things that are caught that the fishermen don’t want and throw back in, these marine animals are often injured due to fishing gear and die
turtle excluder device
used by shrimp fishery
A turtle excluder device is a specialized device that allows a captured sea turtle (or other large marine animals) to escape when caught in a fisherman’s net.
costs of overfishing
lost way of life when this is not a viable source of income
biomagnifier
the process by which a compound (such as a pollutant or pesticide) increases its concentration in the tissues of organisms as it travels up the food chain
fish accumulate mercury more rapidly than they excrete it, and every fish up the aquatic food chain contains more than the one it just ate.
ocean acidification
since the beginning of the industrial revolution, the pH of surface ocean waters has fallen by .01 pH units. Since the pH scale, like the Richter scale, is logarithmic, this change represents approximately a 30% increase in acidity
organisms with shells cannot extract the carbonate ion they need in order to make shells because it is converted to bicarbonate ions
more carbon dioxide in the ocean is decreasing the pH of the ocean, carbonate ions will bind to excess protons to try to increase pH and make more basic
less carbonate ions are available for calcification
if pH is too low, calcification of shells cannot occur, in 2100 predicted pH and carbonate levels, a shell would dissolve in 45 days
marine reserves (solution to overfishing)
When New Zealand’s first marine reserve was proposed in 1965, at Goat island, some local folks screamed in protest
after many battles, most New Zealanders now value reserves for promoting education, recreation, and tourism, as well as conservation
31 havens, goal: to set aside 10% of coastal waters by 2010
fish stock can recover in this zone
community
the collection of animal and plant populations interacting directly or indirectly is referred to as a community
guilds
feeding groups ex: birds feeding on mainly on insects, makes up an insect feeding guild
therophytes
annuals survive unfavorable periods as seeds. complete life cycle from seed to seed in one season.
geophytes
crytophytes
buds buried in the ground on a bulb or rhizome
hemicryptophytes
perennial shoots or buds close to the surface of the ground; often covered with litter
chamaephytes
perennial shoots or buds on the surface of the ground to about 25 cm above the surface
phanerophytes
perennial buds carried well up in the air, over 25 cm
trees, shrubs, and vines
epiphytes
plants growing on other plants; roots up in the air
disturbance
is a temporary change in environmental conditions that causes a pronounced change in an ecosystem.
phenology
the study of cyclic and seasonal natural phenomena, especially in relation to climate and plant and animal life
biological structure of a community
the mix of species, including both their number and relative abundance
keystone
sometimes a predator controls the structure of the community and so must be regarded as the dominant species
dominance=
basal area or aerial coverage, species A/ area sampled
relative dominance
basal area or coverage, species A/ total basal area or coverage, all species
Shannon Weiner index
this formula is used to measure the evenness of diversity where fi is the number of individuals in a given species
bottom up regulation
emphasizes the limitations imposed by the availability of food resources, level above is influenced by the resources provided by the level below
carboniferous forests
did not decompose in the way plants do today
the first termite was 100 years in the future
oxygen concentration was double that of today, consequently insects with no lungs could get much bigger
today fossil forests are the worlds coal reserves
plant and animal material was trapped, buried, and fossilized, now is being mined and the carbon that was previously trapped is now being emitted
where do 800,000 year old data come from
bubbles in ice
fossil fuels
US greatest contributor
OIL and GAS
abundant
make a lot of things from it- plastics
it is an emitter and oil spills occur
NEEDED: significant volume, transportation infrastructure, refining capability, political stability, market
natural gas
abundant
cleanest burning of fossil fuels
embargo on russia
cannot be stored and has to be burned and wasted
coal
abundant
dirtiest and most expensive
tough on earth- mining and burning it
coal ash and toxins
coal use is in decline
nuclear power
atomic meltdowns- radioactive water spills
low-carbon energy sources
reliable and cost-effective
hydroelectric
zero emitter
changes ecology: river into a lake
if there is a drought, this is not an option
solar
cheap
abundant
zero emitter
only works during the day unless a battery stories energy
can put solar panels anywhere, saves money on electric bill
Wind
1 source of energy in tx
can be stored in batteries
damages wildlife
only when wind blows
biofuels
emit when growing
burning is clean
pull carbon out first
marine turbines
always going and water is always moving
marine life damaged
