Plant Community Succession and Ecological Transitions
States and Transitions in Succession
Plant Community Succession
(Initial Ideas – F.E. Clements)
Natural Potential
Large Variation
Between Years
Climax or Potential
Natural Community
Pioneer/Early
Late
Seral Stage
Plant Community Succession
(Initial Ideas -- Clements)
Natural Potential
Pioneer/Early
Late
Seral Stage
Climax or Potential
Natural Community
Example
-Succession in the western juniper woodland
Grassland after fire
Stand initiation
juniper
Open young juniper
Young multistory
juniper
Old multistory
juniper
Mountain big
sagebrush steppe
Cyclic Patterns creating a “Dynamic Equilibrium”
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Problems with Succession Model
Wyoming big sagebrush/bluebunch
wheatgrass steppe near Mtn. Home, ID
Wyoming big sagebrush/bluebunch
wheatgrass steppe, central Idaho
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Two examples of stable states for same ecological site
Problems with Succession Model
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State and Transition Models
1989 - Westoby, Walker and Noy-Meir
State A
State D
State C
State B
Focus on
States
of communities
and
Transitions
between states
Creosotebush community -this ecological site may have always
been creosotebush dominated, or degraded long ago.
States and Transitions depend on biotic &
abiotic conditions
States are relatively stable
but some states are more stable than others
States and Transitions depend on biotic &
abiotic conditions
Higher
Elevation
Central Idaho
Lower Elevation
Central Idaho
Higher Elevation
Southwestern Idaho
Juniper Present
Cheatgrass Risk
Low Cheatgrass Risk
States and stability depends on factors such as
elevation & climate
Example
-
Sagebrush Steppe States
Fire transition
Succession transition
Improper grazing transition
Transitions= compositional change resulting in the
change in plant community (state)
Thresholds
= transitions that are nearly
irreversible & sometimes unpredictable.
Sagebrush Steppe State
The information required to develop these models:
•
potential alternative vegetation states on a site
•
potential transitions between states
•
opportunities to achieve favorable transitions between
vegetation states and hazards to avoid unfavorable
transitions
Rangelands are
Dynamic
!
Rangeland Ecology and Management
•
But, dynamic
patterns can be
describe in state
and transition
models.
•
We manage
transitions
Explore the dynamic process of plant community succession, from pioneer stages to climax communities, and the intricate patterns of transitions in ecological systems. Discover the variability and stability of different states within ecosystems, highlighting the complexities of natural ecological dynamics.
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Presentation Transcript
Plant Community Succession (Initial Ideas F.E. Clements) Climax or Potential Natural Community Large Variation Between Years Natural Potential Pioneer/Early Late Seral Stage
Plant Community Succession (Initial Ideas -- Clements) Climax or Potential Natural Community Natural Potential Pioneer/Early Late Seral Stage
Example-Succession in the western juniper woodland Mountain big sagebrush steppe Grassland after fire Stand initiation juniper Old multistory juniper Young multistory juniper Open young juniper
Cyclic Patterns creating a Dynamic Equilibrium 1979 - Pre-burn 1980- 1st year after fire 1994 1983 1989
Problems with Succession Model multiple pathways of succession multiple stable vegetation types no single and certain end-point Two examples of stable states for same ecological site Wyoming big sagebrush/bluebunch wheatgrass steppe, central Idaho Wyoming big sagebrush/bluebunch wheatgrass steppe near Mtn. Home, ID
Problems with Succession Model multiple pathways of succession multiple stable vegetation types no single and certain end-point State and Transition Models 1989 - Westoby, Walker and Noy-Meir
Focus on States of communities and Transitions between states State A State D State B State C
States and Transitions depend on biotic & abiotic conditions States are relatively stable but some states are more stable than others Creosotebush community -this ecological site may have always been creosotebush dominated, or degraded long ago.
States and Transitions depend on biotic & abiotic conditions Juniper Present Low Cheatgrass Risk Higher Elevation Southwestern Idaho Higher Elevation Central Idaho Cheatgrass Risk Lower Elevation Central Idaho States and stability depends on factors such as elevation & climate
Example - Sagebrush Steppe States Open Sagebrush Grassland Depleted Sagebrush Closed Sagebrush Transitions= compositional change resulting in the change in plant community (state) Fire transition Succession transition Improper grazing transition
Sagebrush Steppe State Open Sagebrush Grassland Depleted Sagebrush Closed Sagebrush Threshold Annual Grass Dominated State Grazing reduces likelihood of fire Thresholds = transitions that are nearly irreversible & sometimes unpredictable.
The information required to develop these models: potential alternative vegetation states on a site potential transitions between states opportunities to achieve favorable transitions between vegetation states and hazards to avoid unfavorable transitions
Rangeland Ecology and Management Rangeland Ecology and Management Rangelands are Dynamic! But, dynamic patterns can be describe in state and transition models. We manage transitions
