Exam 4 Flashcards
therophytes
annuals survive unfavorable periods as seeds. Complete life cycle from seed to seed in one season
geophytes (cryptophytes)
buds buried in the ground on a bulb or rhizome
hemicryptophytes
perennial shoots or buds on 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
community
the collection if animal and plant populations interacting directly or indirectly
guilds
feeding groups
bird species become more diverse as vertical stratification
increases in forest ecosystems
vertical stratification
vertical layering of a habitat; the arrangement of vegetation in layers, a key factor for structuring their species richness and biodiversity
phenology
the study of cyclic and seasonal natural phenomena, especially in relation to climate and plant and animal life
keystone
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
H = n log n - sum fi log fi /n
this formula is used to measure the evenness of diversity
fi= the number of individuals in a given species
competition if more evident among
the species of the same guild (eating the same food) ex: chipmunks
food chain
feeding relationships in nature are not simple straight-line chains but complex webs
grass > grasshopper > flycatcher > hawk
what limit herbivores
autotrophs
what does the bottom-up regulation view emphasize
the limitations imposed by the availability of food resources
succession
in its most general definition is the temporal change in community structure through time, begins with disturbance
Henry Chandler Cowles
studied ecological succession in the Indiana Dines of Northwest Indiana. This led to efforts to preserve the Indiana Dunes
FE Clements
described plant succession (the word)
characteristics of disturbance
4 factors
1. the magnitude of the physical force, such as the strength of the wind, or the heat of a fire
2. the morphological characteristics of the organisms that influence their response to the disturbance
3. the nature of the substrate (soil). Is the soil wet, 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 between disturbances are long, or frequency is low
biomass accumulates and the intensity of disturbance can be high
four premises of 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 story
succession began with the development of a bare site, called nutation (disturbance)
nutation was followed by migration, the arrival of propagules onto the area
migration was followed by the establishment and initial growth of vegetation
the outcome of the process was the replacement of one plant community by another reaching a phase called stabilization
maple and beech seeds are distributed by
wind
pine seeds are distributed by
animals
dominance of short overstay and understory of pine to hardwood
in the early stages of plant succession, shade-tolerant species come to dominate 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 the shade-intolerant species dominate the canopy, no new individuals are being recruited into the populations
climax
end point of succession
classical ecological theory
succession stops when the sere has arrived at an equilibrium or steady state with the physical and biotic environment, at this point the community is stable and self-replicating
characteristics of climax
the vegetation is tolerant of the environmental condition 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 an equilibrium
Jack Pine Forests
jack pine is a fire adapted species found in the Great Lakes region of North America
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 rely prepared ground of ash
Kirtland’s Warbler
endangered; limited geographical range
nest in jack pine trees, cowbird trapping to save the warblers, if human involvement stops, could become endangered again
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
what seed reserves become depleted with too many fires
shrubs in chaparral of cali
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 epithets in their crowns are candidates for wind throw
hurricane
a powerful recurring event of high intensity but low frequency
those with speeds in excess of 166km/hr and associated rainfall of 200mm, have devastating impact on ecosystems
affect of strong winds with heavy snowfall
weighs down trees and heavy rains soften the soil about the roots
cyclic replacement in an oil-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
chronoseres
come back
chronosequences
come back
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 never have supported life
examples of primary succession
rock outcrops and cliffs, sand dunes, and newly exposed glacial till
soil succession
light is not the only environmental factor that changes over the course of succession
atmospheric nitrogen must fix and be incorporated into the plants, where it can later be broken down and made available in the soil through the process of decomposition
nitrogen fixing rhizobium, such as with alder, can grow and dominate a “new” site
this pattern of increasing accumulation of litter and other nutrients was shown in primary succession at glacier bay, alaska
plant diversity increases with
site age
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
secondary succession
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
temporal changes in dominant phytoplankton
seasonal changes in temperature, photoperiod, and light intensity produce a well-known succession of dominant phytoplankton in freshwater lakes, which is repeated with little variation each year
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
