Module #11: Succession

Question 1

Succession

Answer 1

The temporal sequence of compositional or structural changes in vegetation. (change in vegetation communities)

-Usually after disturbance recovery or previously unvegetated area

Question 2

Primary Succession

Answer 2

Occurs on newly uncovered bare ground that has not supported vegetation before (such as in volcanic activity or glacier zones)

-usually undeveloped soil
-need dispersal of propagules to site
-rate of vegetation development controlled by soil development
-will take over 1,000+ years

Question 3

Hydrarch succession

Answer 3

(type of primary succession): Succession on wet sites in which wetness decreases over time.

-usually takes 200+ years to dehydrate land

example:

water vegetation -> emerging vegetation -> dried out, trees coming in

usually:

open freshwater -> submerged plants -> marsh -> swamp -> woodland

Question 4

Xerarch succession

Answer 4

(type of primary succession): Dry sites where soil is created from parent material and wetness increases over time.

example:

lichens -> mosses -> annuals -> perennial herbs -> xeric shrubs and trees

Question 5

Autogenic Succession

Answer 5

The community itself propels a directional sequence of community and related ecosystem changes that follow the opening up of a new habitat.

*using resources, competition, symbiosis, etc. in which organisms change the environment

Question 6

Allogenic Succession

Answer 6

Fluctuations and directional changes in the physical environment steer succession. Environmental factors disturb communities and ecosystems by disrupting the interactions between individuals and species.

Question 7

Secondary Succession

Answer 7

Occurs on disturbed ground that previously supported vegetation.

-disturbances such as fire, flood, and hurricane changed the landscape and therefore community composition

-biotic processes usually determine time frame, usually a few hundred year cycle or less
-soil is already present, so not limiting

Question 8

Clementsian Succession

Answer 8

Frederic Clements- Viewed communities as discrete, well defined entities, proposed the “community-unit” theory

-A predetermined sequence of developmental stages (sere) that ultimately leads to a self-perpetuating, stable community called the “climactic climax vegetation.”

Question 9

Six stages of Clementsian Succession

Answer 9

1. Nudation: area left completely bare after disturbance
2. Migration: Species arrive via spores, seeds, etc
3. Ecesis: Plants establish
4. Competition: Established plants compete for resources
5. Reaction: Established plants alter their environment and enable other new species to arrive and establish
6. Stabilization: After several waves of colonization, an ending equilibrium climax is acheived.

Question 10

Monoclimax/Climactic Climax

Answer 10

A reasonably permanent stage of succession given climactic conditions.

-species present have similar habitat requirements, where a similar set of conditions are found, you will find the same community

-narrow ecotones (abrupt transitions) between communities

Question 11

Organismic View of Community

Answer 11

Plants functioning together as organs for an entity, the community, or superorganism. The development of a community is similar to that of an organism: in which it has youth, mature, and old stages.

Question 12

Relay Floristics

Answer 12

Each stage prepares the site for the next, goes away, and hands off site to next stage

(referring to the organismic view, and how a community has a youth, mature, and old stage)

-Groups of species successively enter and leave the site. Species make the conditions unsuitable for themselves and more suitable for later species

Question 13

Polyclimax Hypothesis (Tansley, 1939)

Answer 13

There are several climax communities that can exist in an area, despite having the same regional climate due to other factors such as soil moisture, nutrient levels, fire frequency, topography, etc.

Basically, climate is only one factor in creating a community, and does not dictate everything.

Question 14

Steady state Equilibrium

Answer 14

An unvarying condition in a physical or biological process

Question 15

Dynamic Equilibrium

Answer 15

Demonstrates a trend over some period of time, but fluctuates around an average value. It may be long term cyclical change.

Question 16

Metastable Equilibrium

Answer 16

Proceeds in a step-wise fashion, once past the unstable point/threshold, you will not be able to return back to the previous state.

Question 17

Non-equilibrium

Answer 17

There is no single or multiple steady states, just multiple possible states, and always in some type of change.

-external factors play a larger role in the behavior of the ecosystem (in contrast with equilibrium, in which internal factors such as competition play a large role)
-disturbance, dispersal, and historical legacy can influence multiple trajectories

Question 18

Gleason and Watt (1920’s, the non-equilibrium idea)

Answer 18

Succession is a population-level process, dispersal and colonization are important, which propagules can disperse to a site and establish.

-succession leads no where in particular

Question 19

Whittaker and the Individualistic View (1950s)

Answer 19

Individualistic view- each species in a community is unique and has its own life history traits way of interacting with the environment.

-rejection of the superorganism view, and believes that organisms aren’t working together towards a collective “goal,” each acts in their own best interest

Question 20

Initial Floristics (Egler 1950s)

Answer 20

Any species may be found initially on a site, although early succession species may dominate at the beginning, and others become dominant over time.

-dispersal plays a role in what species are initially there,
-then competition and environmental interaction determine who stays

-all species are present from the beginning, and each group drops out in turn until only trees dominate in an equilibrium state.

Question 21

Catalino et al. (1979)

Answer 21

-Conducted a study in glacier national park montana
-Modeled several different pathways in GNP depending on timing of disturbance events and key-life history traits
-life-history traits of each species play an important role in determining the sequence of compositional changes and end-products of vegetation recovery processes.