State and Transition Modeling Workshop

Updated 06/09/2006

Questions addressed during the workshop:

1. What is a state?

   The discussion opened with a response of the group to the definition proposed in the presentation by Meiman, Krueger and Stringham,"A recognizable complex of two resilient and stable substates: the abiotic foundation and the biotic framework" (for further explanation, see presentation). Discussion from the group was as follows: The biotic substate can change without changing the site The abiotic substate can not change without changing the site States should be defined in the broadest interpretation (i.e. states are only valid when separated by thresholds). Changes within a state should be referred to as "communities" that may include both plant and animal populations as indicators. These communities represent natural variation within a state and are reversible with only minimum input and/or natural climatic variability. Communities may represent the results of management actions within a state and can represent critical management decision points. States are probably best defined at the level of growth form, life form or functional group relationships, rather than exhaustive species list. Communities can be described at the species level. Relative risk of communities within a state crossing a threshold should be described.

2. What is a transition?

   In response to the definition presented by Meiman, Krueger, and Stringham, "trajectory of system change, triggered by natural events, management or both, that upon crossing a threshold, is irreversible and will not come to rest before the establishment of a new state". The group suggested: Irreversible was an inappropriate term and should be defined in terms of the energy required (practices) and time to return to the original state. The term "Transitions" should only be used to describe changes between states. Changes between communities should be referred to as "community pathways." Factors that drive change, such as climate and/or management actions, should be described in terms of soil, water, air, plants, and animals.

3. What are thresholds and how do we describe them?

   The definition of "thresholds" provided by Meiman, Krueger and Stringham as "boundary in space and time between states, or along transitions such that an abiotic or biotic process or resource has been irreversibly changed and must be actively restored before return to a previous state is possible" was discussed and the following points were emphasized: Irreversible is an inappropriate term and thresholds should be defined by the amount of energy and/or the time required to effect the change. Vegetation management practices (i.e. prescribed grazing and prescribed burning to simulate natural components of the system, etc.) and facilitating practices (fencing, water development, stock trails, etc.) are associated with change along a "community pathway". Accelerating practices (brush management, range planting, etc.) are associated with changes along thresholds. It was pointed out and accepted by the group that the use of the terms management, facilitating, and accelerating practices should be, and commonly are, used within the context of management systems, such as in conservation planning and the application of resource management systems. A threshold is not necessarily a single point in time or space along the transition trajectory, but probably is a region along that continuum. Thresholds may be crossed in which the site is no longer capable of supporting the same suite of states, such as irreversible loss of soil physical and chemical properties, and a new site is described

4. What about soil loss/erosion?

   Does it represent a change of state or a change of site? If the soil does not change, then the site remains the same and community changes can be described as changes within or between states. If the soil characteristics change to the degree that the soil will no longer support the original suite of states, it becomes a new site. A change in soil characteristics that results in a change in the taxonomic classification or series name or the soil, or a designation with a different soil map unit phase term such as eroded or drained, usually indicates a new site. Exceptions to using a change in soil name to indicate a new site may occur where the soil is highly resilient, such as in humid areas. If a new site is described due to changes in soil properties, it is important to maintain the link between the initial site and the new site in order to insure the integrity and accuracy of previous inventories.

5. What are the time frames and how do we express them?

   In the text portion of the site description, it is preferable to separate longer-term ecological processes and changes from shorter-term management actions. Time frames should be discussed in terms meaningful to management.

6. Is there a way to integrate wildlife responses into the STMs?

   Wildlife responses should be integrated into the interpretations section, just as with any other land use activities. If there is evidence that changes in animal populations (presence/absence or numbers) are agents that drive change between either states or communities, those drivers should be incorporated into transition descriptions.

7. Should riparian plant communities be separate sites or described inside the appropriate ecological site?

   Procedures exist within the soil survey for delineating riparian areas as separate map units. Procedures exist within the site description format to describe water features influencing the site. The size and extent of riparian areas will vary by region and landscape and the responsible site description authors should use best judgement.

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