Succession
• There is always flux in community
composition, but there may be apparent
directional change (e.g. an orderly process of
community development that is reasonably
directional and somewhat predictable).
• Thus succession is a temporal change in
community composition
Succession
• Succession can be viewed as the temporal
changes in species composition following
natural or anthropogenic disturbances
• However, it can also be a series of minor
changes of structure and operation
accumulate over time
Succession
• Early studies documented dramatic temporal
changes in plant species composition
Succession Models
• These patterns of succession have been
documented in old fields from North Carolina
to New Jersey and to the mid-west
• Although the species composition varies
between sites and regions, there is a general
pattern: annuals, biennials, perennial herbs,
short-lived conifers, to a mature mixed
hardwood forest
Succession Models
• Succession can be viewed as primary
succession (sites without vegetation) or
secondary succession (sites with established
vegetation)
• During primary succession, propagules
typically arrive from distant locations
• Process may be relatively slow as secondary
colonizers cannot arrive until bare ground can
be transformed into suitable habitat
Succession
• Bare ground must be broken down and
enriched with nitrogen
Succession
• The successional paradigm works well for such
obvious examples as primary succession in the
wake of retreating glaciers or volcanic islands
Succession Models
• Secondary succession alters one vegetative
type into another
Succession Models
• Another way in which ecologists differentiate
between succession types is that of autogenic
succession (driven by processes operating
within a particular location) and allogenic
succession (driven by processes outside a
particular site)
Succession Models
• One of the goals in
understanding
succession is to help
predict and accelerate
community changes
after natural
disturbances such as
fires or storms
Succession Models
• Optimal ecological restoration of sites
disturbed by human activity clearly depends
upon knowledge of the factors that promote
rapid or otherwise desirable successional
changes
Succession Models
• There are other types of succession besides
primary or secondary succession
• Seasonal succession refers to a regular annual
phenology of abundance or activity that
occurs without the permanent loss or addition
of species from the community
Succession Models
• Examples include the sequence of flowering
by woodland plants, seasonal variation in
insect reproduction, or seasonal variation in
the activity and abundance of aquatic
microorganisms
Succession Models
• Cyclic succession occurs in special
circumstances in which a small number of
species tends to replace each other over time
• A classic example involves heather (Calluna)
and the bracken fern (Pteridium). Calluna can
invade stands of Pteridium under some
situations. However, as the Calluna plants age
and senesce, they can be replaced by Pteridium
Succession: a brief history
• Henry Chandler Cowles
(1899) was one of the first
individuals to recognize
succession as an
ecological phenomenon
• Using Lake Michigan
dunes of different ages,
he inferred successional
patterns
Succession: a brief history
• This approach, sometimes called space for
time substitution or chronoseries, can be
used to infer successional patterns
• Can you see the advantage?
• Can you see a potential disadvantage?
Succession: a brief history
• Clements, often viewed as the forefather of
successional theory, perceived succession as a
deterministic phenomenon, a development
within the community proceeding
directionally to some ‘climax’ community
through a series of distinct seral stages
• Different communities were the result of
environmental regimes
Succession: a brief history
• Succession was seen as convergent, with
communities of a wide variety of initial
starting points converging on a limited
number climax states
• This can be largely predictable
– E.g. if the succession is set-back, it will just pick up
on the same trajectory as to where it was heading
Succession: a brief history
• Conversely, other botanists such as Cooper,
Gleason, and Tinsley all viewed communities
as a more random assemblage of individuals
existing as snapshots in time and space
• Individuals abundances rise and fall somewhat
independent of one another (although similar
conditions may be driving changes)
Succession: a brief history
• Frank Egler (1952) provided the next important
conceptual development in succession promoting
the idea that became known as the initial floristic
composition hypothesis
• Addresses the pattern of secondary succession
and holds that succession at a site is determined
largely by the species composition of plant
propagules already present when the site is
disturbed
• Subsequent changes due to differing longevity
Succession: a brief history
• Eugene Odum (1969) viewed succession as an
orderly (i.e. predictable) pattern of
community development that produced
significant changes in a variety of ecosystem
attributes
• This orderly process was due to modifications
of the environment driven by the developing
community
Succession: a brief history
• Table 13-1 Morin
Succession: a brief history
• Drury and Nisbet (1973) preented a somewhat
more complex framework based upon
differential growth, survival, and colonizing
ability of species along various environmental
gradients
• Different species have different LHC and they
can exploit different environmental conditions
Succession: a brief history
• Once established at particular sites, individual
plants have a competitive advantage over
seedlings and immigrants of other species that
attempt to become established (not Clements)
• Although there is a trade-off in that colonizing
ability and somatic growth rates are inversely
correlated with longevity and maturity (weedy
colonists vs. slow-growing, large, dominant sp)
Succession: a brief history
• Connell and Slatyer (1977) emphasized the
different mechanisms that might be involved
in species-by-species replacements
• First, competition probably overemphasized
due to lack of succession experiments
• Second, succession could result from 3 basic
interactions
Succession Models
• Facilitation, in which early species enhance
establishment of later species
• Tolerance, in which early species have no
effect on later ones
• Inhibition, in which early species actively
inhibit establishment of later ones
Succession: a brief history
• In all of these interactions it is assumed that
early species cannot invade and grow once the
community is saturated
• There is some evidence for facilitation,
particularly among autotrophs during primary
succession and for the succession of groups of
heterotrophs in various kinds of decomposing
organisms
• Lots of evidence for inhibition, little for
tolerance
Succession: a brief history
• Walker and Chapin (1987) expanded the notion
of succession as a temporal gradient in the
importance of various interspecific interactions
and other events
• During colonization, maturation and
senescence the importance of seed dispersal,
availability of propagules on the site, the
importance of stochastic events, facilitation,
competition, maximum growth rates, longevity,
herbivory and others
Succession: a brief history
• Pickett and McDonnell (1989) expanded on
Walker and Chapin and suggested the whole
process of vegetation dynamics is the end
results of a hierarchy of interacting factors,
but again a very complex series of events that
are probablistic, not deterministic
Succession: a brief history
• Fig 13/2
Succession: effects on animals
• Given there are a number
of well-known plantanimal relationships,
plant succession may
have an impact on animal
assemblages
• However, few studies
attempt to examine this
Succession: effects on animals
• Changes in the animal community tend to be
correlative and typically only for a single group
in a study (birds)
Succession: effects on animals
• For example, the decline of
eastern bluebirds have been
ascribed to the loss of early
succession habitat (along with
several other early succession
associated species in the NE)
Succession: effects on animals
• Table 13-4
Succession: effects on animals
• Another example is the redcockaded woodpecker,
restricted to old-growth
longleaf pines (particularly
those infected with a
heartwood fungus); several
other sp. associated with
this habitat declining
Succession: effects on animals
• There is also a general relationship between
bird species richness (and density of breeding
birds) and seralstage
• Fig 13.8
Succession: effects on animals
• It is unclear what the
relationship between diversity
and seral stage exists for other
groups
• There are some groups,
perhaps arthropods, that are
likely to show strong plant
associations
Succession: effects on animals