TELSA (Tool for Exploratory Landscape Scenario Analyses) is a spatially explicit, strategic planning tool. The tool was developed by ESSA Technologies Ltd. TELSA was designed to predict the consequences of alternative management and natural disturbance scenarios at the scale of landscape units (up to about 250,000 ha or about 100,000 polygons) over various user-specified time frames.
The tool represents vegetation succession and the impacts of natural disturbances and management as changes in species composition, age, and structural stages of stands, using successional pathway diagrams (SPD) developed within the Vegetation Dynamics Development Tool.
TELSA Logo. Source: ESSA
Natural disturbances are represented in the model using the probabilities and pathways defined in the SPD, as well as additional information about the size-class distribution of the disturbances, the annual variation (e.g. amount of precipitation), and long-term trends (e.g., increasing fire risk). Management impacts are also defined in the pathway diagrams. Various management options are combined into management systems that define the sequence of activities to be applied to a polygon, the stand age for the activities, and various constraints on the size of management units (treatment blocks), adjacency (green-up), or on the total area affected by a management activity.
Additionally, the TELSA toolbox contains a tessellation tool capable of creating simulation polygons; a management unit building tool that groups and assigns polygons to management systems; a spatial analysis tool to calculate patch-size distributions, interior old- growth habitat, and border lengths; and user interfaces which can be used to edit the database or view graphs, tables, and maps of the simulation results (Kurz et al. 2000).
TELSA can aid resource managers and planners in assessing the consequences of alternative management scenarios at the landscape scale. One of the main advantages of TELSA is that it takes into account natural disturbances allowing users to observe how their defined management strategies will interact with vegetation succession and disturbances to modify landscape composition and structure.
TELSA can be used as a tool for landscape modelling, for adaptive management, or for any other planning process that involves different groups of experts and stakeholders who need to compare and assess the outcomes of different assumptions across space and time. TELSA simulates multiple scenarios, each characterized by different assumptions about management actions and natural disturbances. Since most of the natural disturbances are unpredictable, the model can use multiple stochastic simulations of each scenario to provide estimates of the mean, range and variability of future values of the selected performance indicators.
Diagrams developed with the Vegetation Dynamics Development Tool (VDDT) define the transition times between various state classes (combinations of species composition and structural stage) and the probabilities and impacts of disturbance by insects, fire or other agents. These diagrams also define the impacts of landscape management actions on structure and composition.
TELSA combines commercial software products (a Microsoft Access™ database and the ArcView / Spatial Analyst™ GIS) with a custom simulation model and interfaces to the database and GIS systems. TELSA uses numerous customized ArcView tools to automate the preparation of spatial files for use with the model and to facilitate the spatial display of output data from the database. Specialized graphing routines allow users to quickly view and compare the results from one or more simulations. TELSA is a toolbox of models and programs. The tools can help researchers to: • Prepare spatial and other model input data; • Define various management and natural disturbance scenarios; • Simulate these scenarios; and • Analyze compare and display simulation results.
TELSA runs on high-end PC platforms with Windows 2000 or XP operating systems. So far, TELSA does not work on ArcGIS version 10. The toolset can be used in all other older versions of ArcView. TELSA is designed to simulate landscapes that are up to approximately 800,000 ha, although larger landscapes have been simulated. TELSA is designed to run on high-end personal computers with the following minimum hardware requirements: • Pentium-class processor of 500 MHz or faster; • Monitor capable of 1024 X 768 resolution – small fonts highly recommended; • At least 64 megabytes of RAM (128 megabytes is ideal); and • 1 gigabyte or more of available hard drive space. The model runs under a 32-bit operating system such as Windows NT 4.0, 2000 or XP, and you must have the following software installed on your system: • ArcView GIS (version 3.1 to 9.3) • ESRI Spatial Analyst (version 1.1 or higher); • Microsoft Excel (97 or 2000); • The Vegetation Dynamics Development Tool (version 3.0 or higher); and • The software included in the TELSA toolbox.
TELSA requires the following input data from the user: • Transition pathway diagrams with succession, management, and disturbance pathways and transition probabilities (these diagrams can be developed using VDDT and imported to TELSA); • Landscape cover maps showing the distribution of vegetation cover and structure; • Maps of zones with different management constraints (such as parks, watersheds, riparian zones); • Management information (management limits, size classes of management units, age and order of activities); and • Disturbance size distributions, between-year variation and temporal trends.
TELSA divides the landscape into simulation polygons. This map shows the original forest cover polygons (black lines), riparian areas (red and tan) and the resulting tessellation (green lines) into the simulation units that are explicitly simulated. Source: ESSA
TELSA results can be viewed as maps, graphs, or tables, for the entire landscape or for specific section of the landscape. Since all results are stored in an Access database can compare results of different scenarios or multiple Monte Carlo runs of one or more scenarios. Basic information such as area disturbed (including the range of area disturbed or the frequency of disturbance for different polygons), age-class distribution (figure on left below), and seral stage distribution, can be graphed and mapped. Additional spatial information such as count and area distribution of patch size classes and interior habitat (figure on right below), and the length of edge between different seral stages or age classes are also calculated. Because the state of every polygon is known for every reporting time-step, further post-processing for wildlife habitat interpretation or other analyses is also possible.
A comparison of layout and age class distribution of two landscapes with different management and disturbance histories. Source: ESSA
A portion of a landscape showing areas of interior habitat. Source: ESSA
Kurz et al. 2000. Described the capabilities of TELSA for landscape studies.
Provencher et al. 2007. Used spatial simulations of 10 potential vegetation types to compare 6 management scenarios over 20 years in a 141,853 ha landscape in eastern Nevada.
Kurz WA, Beukema SJ, Klenner W, Greenough JA, Robinson DCE, Sharpe AD, and Webb TM. 2000. In COMPUTERS AND ELECTRONICS IN AGRICULTURE. 27 (1-3): 227-242.
Provencher L, Forbis TA, Frid L, and Medlyn G. 2007. In Ecological Modelling. 209 (2-4): 249-263.
ESSA Technologies Ltd. Website. http://essa.com