Progress 07/01/05 to 06/30/08
Outputs
OUTPUTS: We have developed a prototype simulation model for investigating apparent woodland expansion at the lower woodland-sagebrush ecotone, representative of the central Nevadan Great Basin. The model was developed within the SELES framework. SELES is a spatially explicit landscape event simulator. For purposes of model calibration and sensitivity analysis, we mapped pinyon-juniper distribution and age class structure for an approximately 20 sq. km. area. Although the project has formally ended, model outputs and still being analyzed to describe the reciprocal interactions among disturbance regime, the landscape-level seral stage mosaic, and the probability of cheatgrass dominance. An additional project output has been a spatial model of historical harvest probabilities from 1878 to 1895. Although the project has formally ended, we are still in the process of validating this model with field data on cut stumps, charcoal platforms, logging camps and other evidence of historical tree harvesting. A manuscript is in preparation describing this model and its application. We implemented a field study to quantify the relative error associated with alternative field-based and remote-sensing methods in pinyon-juniper woodlands. Results are summarized in a paper in press in the journal Forest Science. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Our canopy cover methodology study has led to specific recommendations for researchers seeking to monitor long-term changes in woodland distribution and extent using a combination of on-the-ground and aerial methods. The study of historical (early-settlement) tree harvesting indicates the importance of historical processes, which may no longer be evident on the landscape, for understanding current dynamics of rangeland succession and changing extent of tree-dominated areas. We have ported the general simulation modeling approach to a related project modeling the implications of alternative fire regime scenarios for the relative dominance of sagebrush and pinyon-juniper woodland communities on a given landscape. Once model testing has been completed, model outputs should provide managers with a quantitative means to distinguish landscape areas with persistent woodlands from areas where trees may be present today, but may not be likely to occur under particular disturbance regime scenarios.
Publications
- Ko, D., Bristow, N., Greenwood, D. L., Weisberg, P. J. 2009. Canopy cover estimation in semi-arid woodlands: comparison of field-based and remote sensing methods. Forest Science, in press.
- Weisberg, P.J., D. Ko, C. Py, and J. Bauer. 2008. Modeling fire and landform influences on the distribution of old-growth pinyon-juniper woodland. Landscape Ecology 23: 931-943.
- Weisberg, P.J., J. Bauer, D. Ko, and Z. Nelson. 2008. Fire regimes of pinyon-juniper woodlands: implications for landscape change. Society of American Foresters 2008 National Convention, 11/2008. Reno NV (conference abstract).
- Ko, D., P.J. Weisberg, A Sparrow, L. Condon. 2008. Fire regime, legacy effects, and cheatgrass invasion in the Great Basin of central Nevada. Annual meeting of the US-IALE (U.S. Chapter of the International Association for Landscape Ecology), Madison, WI. 4-7-2008. (conference abstract)
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Progress 01/01/07 to 12/31/07
Outputs
The goal of this research is to develop a prototype simulation model for investigating apparent woodland expansion at the lower woodland-sagebrush ecotone, for a large study landscape in the central Nevadan Great Basin. We are initially focusing on the Simpson Park Range northeast of Austin, where we have previously studied patterns and rates of changes in woodland area and tree cover. The purpose of the model is to explore the relative influences of climate change, grazing effects on plant competition, grazing effects on fire regime, tree harvesting during the early settlement period, rangeland restoration treatments, and modern fire suppression, on woodland dynamics in the central Nevada Great Basin. The model, originally developed within the TELSA framework, is being redesigned using the SELES framework. SELES is a spatially explicit landscape event simulator. Vegetation dynamics are modeled using a state-and-transition model, while ecological and cultural
disturbances are modeled using stochastic landscape spread models. For purposes of model calibration and sensitivity analysis, we have mapped pinyon-juniper distribution and age class structure for an approximately 20 sq. km. area. An object-oriented image analysis approach was used to derive vegetation polygons as homogeneous patches; patches were then classified using photointerpretation and field observations. A spatial model has been developed for estimating historical harvest probabilities from 1878 to 1895. Field data on evidence for historical disturbance have been collected and will be used to validate this model. A field study was implemented to quantify the relative error associated with alternative methods for estimating tree canopy cover in pinyon-juniper woodlands. In particular, we are interested in how field-based methods compare with methods utilizing aerial photography, and how to convert or translate estimates from one approach to another. A manuscript on this topic
has been submitted to a peer-reviewed journal.
Impacts
The modeling approach should provide managers with a quantitative means to identify which areas of pinyon-juniper woodland are appropriate for restoration to shrub or grassland dominated states. Model outputs will provide useful guidance for separating woodlands that have recently invaded non-woodland vegetation types from old-growth woodland types. The model development process will improve our understanding of vegetation dynamics in Great Basin montane systems, including recent processes of woodland expansion. Our work on canopy cover estimation methods demonstrates that researchers should match cover estimation methods to canopy structures of the system being investigated, and pay attention to the scale and range of canopy cover where bias and uncertainties dominate. It may be inaccurate to scale from field plot measurements to landscape-level cover estimates using simple areal extrapolation.
Publications
- Weisberg, P.J., Bauer, J., Ko, D., Lingua, E. 2007. Published Abstract. Increased conifer dominance in the Nevada Great Basin, USA: landscape change in the context of fire, grazing and human influences. International Conference: Natural Hazards and Natural Disturbances in Mountain Forests. Trento, Italy.
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Progress 01/01/06 to 12/31/06
Outputs
The goal of this research is to develop a prototype simulation model for investigating apparent woodland expansion at the lower woodland-sagebrush ecotone, for a large study landscape in the central Nevadan Great Basin. We are initially focusing on the Simpson Park Range northeast of Austin, where we have previously studied patterns and rates of changes in woodland area and tree cover. The purpose of the model is to explore the relative influences of climate change, grazing effects on plant competition, grazing effects on fire regime, tree harvesting during the early settlement period, rangeland restoration treatments, and modern fire suppression, on woodland dynamics in the central Nevada Great Basin. A post-doctoral researcher, Dongwook Ko, has been hired (since 2-06) to work primarily on this project. The model structure has largely been developed, within the TELSA (Tool for Exploratory Landscape Scenario Analyses) framework for simulating vegetation disturbance
and succession. This is a spatially-explicit, state-and-transition landscape model which can incorporate natural and anthropogenic disturbances including their interaction with grazing effects. We are in the process of parameterizing and calibrating the model so that it realistically represents dynamics of Great Basin vegetation. In order to parameterize successional trajectories, fire regime and historical driving variables, we have initiated the following sets of analyses: (1) spatial analyses of old-growth pinyon-juniper (PJ) distribution; (2) acquisition and digitization of General Land Office survey records from the late 1800s and early 1900s; (3) spatial modeling of PJ distribution according to topographic and biophysical GIS data layers; (4) development of a separate model to simulate spatial distribution of historical grazing and logging impacts. The latter model of historical grazing impacts is implemented in S-Plus and C and uses a convection-diffusion approach to represent
movement of cattle and sheep from water sources. A cost-of-movement component, incorporating topographic and site productivity influences on grazing probability, is under development. Also under development is a similarly structured model of historical tree harvesting impacts due to the charcoal/mining industries and the needs of population centers. We have begun to develop the spatial datasets underlying this model, including digitization of 19th Century mining locations and production levels, and GIS modeling of charcoal platforms as a function of terrain and proximity to transportation corridors, using results from previous anthropological studies in the area.
Impacts
The modeling approach should provide managers with a quantitative means to identify which areas of pinyon-juniper woodland are appropriate for restoration to shrub or grassland dominated states. Model outputs will provide useful guidance for separating woodlands that have recently invaded non-woodland vegetation types from old-growth woodland types. The model development process will improve our understanding of vegetation dynamics in Great Basin montane systems, including recent processes of woodland expansion.
Publications
- Ko, D., P.J. Weisberg and A.D. Sparrow. 2007. Landscape simulation modeling of anthropogenic impacts on pinyon-juniper woodland distribution during early settlement: Nevada Great Basin. Published abstract, US-IALE (US chapter of the International Association for Landscape Ecology) 22nd Annual Conference, April 2007, Tucson AZ.
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Progress 07/01/05 to 12/31/05
Outputs
A postdoctoral research associate (Dr. Dongwook Ko) has been hired to take the lead on modeling activities associated with this project. Dr. Ko, whose prior experience has emphasized development and application of landscape vegetation models, will start in February 2006. The opportunity to hire a postdoc instead of a graduate student to work on this project has arisen because of a collaboration forged with Dr. Ashley Sparrow, who will contribute funds and act as co-PI in this investigation. Weisberg attended a TELSA landscape modeling workshop in January 2006, and we are strongly considering adaptation of TELSA for model development in this project. Weisberg and Ko will participate in stakeholder meetings planned by Cooperative Extension for Winter/Spring 2006, which will address state-and-transition models. Based upon these meetings, future stakeholder meetings will be planned to address the outreach and model development needs of this project. Finally, we have
initiated a comparative investigation of different spatial analytical methods for distinguishing areas of old-growth woodland from woodland expansion, including GIS-based and simple cellular automata modeling approaches. Results are still quite preliminary, but suggest that the spatial pattern of fuels is a more important predictor for locating old PJ woodlands than are topographic variables indicative of fire barriers and conduits, and that static GIS-based models give results comparable to those of simple dynamic disturbance propagation models.
Impacts
The modeling approach should provide managers with a quantitative means to identify which areas of pinyon-juniper woodland are appropriate for restoration to shrub or grassland dominated states. Model outputs will provide useful guidance for separating woodlands that have recently invaded non-woodland vegetation types from old-growth woodland types. The model development process will improve our understanding of vegetation dynamics in Great Basin montane systems, including recent processes of woodland expansion.
Publications
- No publications reported this period
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