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State and Transition Modeling WorkshopUpdated 08/27/2009 Utah State University, Logan, Utah
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| Tuesday | |||
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| 8:30 AM | Welcome. | Fee Busby, Dean, College of Natural Resources, Utah State University, Logan, Utah | |
| 8:10 AM | Workshop Objectives | Larry Butler, USDA-NRCS, Grazing Lands Technology Institute, Fort Worth, TX | |
| 8:20 AM | Overview and Emerging Issues | Fee Busby, Dean, College of Natural Resources, Logan, Utah | |
| 8:50 AM |
Utilizing State and Transition Models to Aid in the Decision Making Process
(PPT, 334KB) Traditional range site descriptions described a single persistent vegetation state referred to as the climax plant community. Range condition was determined by comparing the species composition of present vegetation to the climax vegetation for the site. Ecological site descriptions will utilize the state and transition model to describe the dynamics of rangeland vegetation associated with each site. State and transition model offers a method to organize and communicate complex vegetation management information. Lack of common understanding as to what constitutes a state, transition and threshold has resulted in a tremendous variability in state and transition models that are being developed. A couple of examples of state and transition models that have been developed will be reviewed. One model was developed utilizing a broad approach in defining the different states and the other model was developed with a more detailed approach describing states that were important from a management point of view. As state and transition models are being developed, need to remember for whom we are developing these models and what information we want the model to provide. We need to agree on common definition for state, transition and threshold. We also need to develop a method to describe those plant communities that are important from a management point of view. State and transition models provide a repository for all of the information that we know about the ecological dynamics of the site. They are excellent communication tools to discuss the dynamics of the site with a land manager. Once developed, the state and transition model will assist land managers in making timely, well informed management decisions. |
George Peacock, USDA-NRCS, Grazing Lands Technology Institute, Fort Worth, TX | |
| 9:15 AM | Break | ||
| 9:30 AM |
Continued Development of Non-Equilibrium Ecology for Rangeland Application
(PPT, 1.6MB)
Concepts of non-equilibrium ecology have been apparent in the literature for a long period of time. During much of the past century however linear models, focused on systems at or near equilibrium, have driven succession theory. Some of these models have dealt with multiple pathways while others have depicted only one pathway as a linear continuum. The quantitative climax approach developed in the late 1940’s is one such model and has been the workhorse of rangeland ecology and management since its development. This model was developed in the Great Plains and has been applied to rangelands across the U.S. In the Great Plains, mountain grasslands, and various other systems, the quantitative climax model often works very well. However, many instances have been identified where the quantitative climax approach has not adequately described observed vegetation dynamics. As a result, many ecologists have looked to non-equilibrium ecological concepts and developed state and transition models in an effort to more adequately describe vegetation dynamics. Although the terms state, transition and threshold are commonly used in rangeland ecology, they have been defined by different individuals at various points in time. As a result, a universal set of definitions linking all of the terms together into a framework for state and transition models is lacking in the literature. A review of the literature reveals at least two different applications of the term ‘state’. One is a very broad interpretation where states encompass multiple expressions of plant communities, or seral stages of plant communities, among which reversible relationships are maintained. An alternative interpretation is of much more specific states that approximate seral stages or condition classes. Thresholds have been interpreted at least two ways, depending primarily on how authors have interpreted states. With specific states, thresholds are often placed between some, but not all states. In many of the broad applications of state, a threshold must be crossed in order for a state change to occur. A variety of state and transition model applications present in the literature were analyzed paying particular attention to the advantages each approach offered to the management of rangeland systems. These advantages were then considered and used to aid in the formulation of draft definitions and a proposed conceptual model linking the concepts of states, transitions and thresholds together. States are defined in terms of abiotic and biotic factors that form the foundation and framework of rangeland systems. Transitions and thresholds are defined relative to states and the proposed conceptual model provides visual representation of how the various components of non-equilibrium ecology may interact. It is recognized and appreciated that the quantitative climax model is appropriate in many systems and therefore, the proposed conceptual model was designed to build upon, rather than to replace it. At the present time, the authors of this effort view it as the next step in the continued development of non-equilibrium ecological models for rangeland applications, and not as a finished product. |
Paul Meiman, Department of Rangeland Resources Oregon State University, Corvallis, Oregon, and USDA-Agricultural Research Service, Northwest Watershed Research Center, Boise, Idaho Dr. W. C. Krueger and Dr. Tamzen Stringham, Department of Rangeland Resources Pat Shaver, USDA-Natural Resources Conservation Service |
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| 10:20 AM |
Changes in Soil Properties: Relevance to State and Transition Models
(PPT, 118KB)
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Arlene Tugel, USDA-NRCS, Soil Quality Institute, Las Cruces, NM | |
| 10:40 AM |
Ecological Site Description Database (PPT, 2MB) The Ecological Site Description database is an internet based program for entering, storing, and retrieving ecological site description information. Ecological site descriptions for rangeland and forestland can be entered into the database. Once a site description has been entered it is immediately available for viewing by anyone. Entering or editing data requires a login and password. These will be distributed to appropriate specialists in each state. The remainder of the presentation will review the different sections of the ecological site description, data elements associated with each section, and how the data can be entered into the site. With the increased use of the internet there is a greater demand to have information such as the Ecological Site Description available and easily accessible. |
Arnold Mendenhall, USDA-NRCS, National Soil Survey Center, Lincoln, NE | |
| 11:00 AM | Development of State and Transition Models | Chuck Ring, USDA-NRCS, Cheyenne, WY and Gary Brackley, USDA-NRCS, Reno, NV | |
| 11:45 AM | Lunch | ||
| 12:45 PM | Group discussion on the development of state and transition models. Addressing the issues, questions, and concerns that have arisen in regards to developing models. | Facilitated by Joel Brown, USDA-NRCS, Cooperating Scientist, Las Cruces, NM | |
| Wednesday | |||
| 8:00 AM | Continued discussion on development of state and transition models. | ||
| 10:00 AM | Break | ||
| 10:20 AM | Wrap up and review of discussions | ||
| 11:00 AM | Strategies for Development of Ecological Site Descriptions | George Peacock, USDA-NRCS, Grazing Lands Technology Institute. Fort Worth, TX | |
| 11:45 AM | Workshop evaluation and adjourn | ||
The NRCS system of range site descriptions has provided guidance for more than 50 years of solid, ecologically- based land management decisions. Describing the interactions among soils, vegetation and land management provided decision-makers with vital information to help set and achieve goals and objectives. However, over half a century of experience in observing ecosystem dynamics coupled with the emergence of a host of new land owners, land uses, management objectives and threats to sustainable management dictate that we redesign our system of land description if we are to continue to provide high quality assistance. In addition, the public interest in sustainable land management requires that we have a firm scientific basis for inventories and assessments of ecosystem health. The conceptual foundation for such a system of site descriptions has been laid in the recently released National Range and Pasture Handbook (Chapter 3, Section 1).
The core information of the Ecological Site Description is the vegetation dynamics model. This model describes how different disturbances (fire, grazing, flooding, mechanical) and stresses (drought, increased precipitation, climate change and variability, exotic species) affect the soil/vegetation interactions on a particular soil. The State and Transition Model (STM) as proposed by Westoby et al is currently regarded as the most accurate, robust and accessible method for describing soil/vegetation dynamics in a decision making context.
Although the concept of STMs has been around for over a decade now, acceptance and implementation at the field level has only recently become a priority. Inconsistencies and ambiguities in terminology and interpretation are currently limiting the efficiency. These inconsistencies need to be resolved to insure that the ecological site description effort is cost-effective and provides accurate information to all users.
Field experience and several recent workshops have identified several aspects of terminology and implementation that need to be resolved. Therefore, NRCS, with the assistance of USU hosted a workshop attended by a variety of agency, academic and research technicians and scientists to develop solutions to these problems.
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