Biogeography Final

Front 1

Succession

Back 1

temporal sequenceof compositional or structural change in vegetation. Recovery after disturbance or colonization of formally unvegetated area.

Front 2

Primary Succession

Back 2

occurs on newly uncovered bare ground that has not supported vegetation before (e.g. volcanic activity, glacier ablation zones).
Hydrarch succession – succession on wetter sites, wetness decreases over time. Probably takes a minimum of 200 years, likely many more.
Xerarch succession – dry sites where soil is created from parent material and wetness increases over time.

Front 3

Autogenic Succession

Back 3

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

Front 4

Allogenic Succession

Back 4

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

Front 5

Secondary Succession

Back 5

occurs on disturbed ground that previously supported vegetation (e.g. Fire, flood, logging, hurricanes, canopy gaps, pathogens).

Front 6

Clementsian Succession

Back 6

Clements viewed communities as discrete well defined entities, the community-unit concept. One of the first scholars to examine the idea of vegetation succession, proposed theory.
– A predetermined sequence of developmental stages, or sere, that ultimately leads to a self-perpetuating, stable community called ‘climatic climax vegetation’.
– Pioneer species establish, alter the environment so that the next group of species can colonize, continuing until a stable equilibrium community evolves

Front 7

Clementsian Succession (6 stages)

Back 7

• There are 6 stages to Clementsian succession:
– Nudation – area left completely bare after disturbance.
– Migration – species arrive as seeds, spores, etc...
– Ecesis – the plants establish.
– Competition – established plants start to compete for resources.
– Reaction – established plants alter their environment and enable other new species to arrive and establish.
– Stabilization – after several waves of colonization, an enduring equilibrium climax has achieved.

Front 8

Monoclimax, or climatic climax

Back 8

(Clementsian Succession cont.)
a reasonably permanent stage of succession given climatic conditions.
– Species present have similar habitat requirements, where a similar set of conditions are found you will find the same community.
– Narrow ecotones, or abrupt transitions, between communities (Discrete view).

Front 9

Organismic view of community

Back 9

(Clementsian Succession cont.)
plants functioning together as organs for an entity, the community, or superorganism. The development of a community is similar to that of an organism, youth, middle age, old.

Front 10

Relay floristics

Back 10

(Clementsian Succession cont.)
each stage prepares site for next, goes away, and hands off site to next stage.

Front 11

Polyclimax hypothesis (Tansley,1939)

Back 11

there are several climax communities that could exist in an area with the same regional climate owing to different soil moisture, nutrient levels, fire frequency, topography, etc... (i.e. site characteristics other than climate have effect on succession).

Front 12

Equilibrium

Back 12

if a disturbance occurs the vegetation will recover quickly back to a stable state, negative feedback within the vegetation leads to a stable persistent state of vegetation, endogenous processes (competition) are the dominant structural processes.