Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: Modeling Near-Surface Temperature and Moisture of Post-Wildfire Seedbed for Germination Response Predictions

Authors
item Flerchinger, Gerald
item Flerchinger, Gerald
item Hardegree, Stuart
item Hardegree, Stuart

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 14, 2004
Publication Date: July 18, 2004
Citation: Flerchinger, Gerald N., Hardegree, Stuart P., 2004. Modeling near-surface temperature and moisture of post-wildfire seebed for germination response predictions, Journal of Aird Environments 59, 369-385

Interpretive Summary: Rangelands comprise about 55% of the total land area of the United States and about 80% of the 17 western states. Resource values are impaired or threatened on millions of acres of these rangelands because of the expansion of undesirable non-native annual weeds following wildfire or other disturbance. New methodologies must be developed to determine the sequence of management actions that will result in the reestablishment desirable plant communities on our western rangelands. The purpose of this study was to simulate near-surface soil temperature and water conditions for predicting potential seed germination response for post-fire, revegetation applications. The Simultaneous Heat And Water (SHAW) model was applied to three soil types (sandy loam, loamy sand, silt loam) instrumented with soil moisture and temperature sensors. Estimates of germination time based on simulated temperature and water potential were compared with germination time estimates based on measured soil and water conditions. Based on simulation results, the SHAW model can be used in conjunction with a seedling germination model to give reliable predictions of germination times for most instances. Long-term simulation of seedbed microclimate in the field is necessary to evaluate potential germination response of revegetation species and their weedy competitors to optimize revegetation of desirable plant communities.

Technical Abstract: A major contributor to resource degradation on rangelands in the western United States is the expansion of undesirable non-native annual weeds following wildfire or other disturbance. The purpose of this study was to simulate near-surface soil temperature and water conditions for predicting potential seed germination response for post-fire, revegetation applications. The Simultaneous Heat And Water (SHAW) model was applied to three soil types (sandy loam, loamy sand, silt loam) instrumented with soil moisture and temperature sensors. Simulation results using three methods of parameter estimation were compared to determine the effect of model-parameter uncertainty on germination prediction. Near-surface soil temperatures were accurately simulated with model efficiencies of 0.89 to 0.96 for the 2-cm depth. Initial parameter estimates of the sandy loam soil yielded relatively poor soil water potential estimates, which resulted din an underprediction of germination times by 4.7 days for cheatgrass to 12.8 days for bluebunch wheatgrass. Model simulations based on measured moisture-release curves resulted in germination prediction within a few days of estimates based on measured temperature and water conditions for the loamy sand site. Predicted germination on the silt loam site was within 0.7 days for the initial simulation and within 3.8 days using measured moisture release curve parameters. Long-term simulation of seedbed microclimate in the field is necessary to evaluate potential germination response of revegetation species and their weedy competitors. Using a germination model to assess alternative soil parameterization scenarios allows one to optimize seedbed model output for this specific application.

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 14, 2004
Publication Date: July 18, 2004
Citation: Flerchinger, Gerald N., Hardegree, Stuart P., 2004. Modeling near-surface temperature and moisture of post-wildfire seebed for germination response predictions, Journal of Aird Environments 59, 369-385

Interpretive Summary: Rangelands comprise about 55% of the total land area of the United States and about 80% of the 17 western states. Resource values are impaired or threatened on millions of acres of these rangelands because of the expansion of undesirable non-native annual weeds following wildfire or other disturbance. New methodologies must be developed to determine the sequence of management actions that will result in the reestablishment desirable plant communities on our western rangelands. The purpose of this study was to simulate near-surface soil temperature and water conditions for predicting potential seed germination response for post-fire, revegetation applications. The Simultaneous Heat And Water (SHAW) model was applied to three soil types (sandy loam, loamy sand, silt loam) instrumented with soil moisture and temperature sensors. Estimates of germination time based on simulated temperature and water potential were compared with germination time estimates based on measured soil and water conditions. Based on simulation results, the SHAW model can be used in conjunction with a seedling germination model to give reliable predictions of germination times for most instances. Long-term simulation of seedbed microclimate in the field is necessary to evaluate potential germination response of revegetation species and their weedy competitors to optimize revegetation of desirable plant communities.

Technical Abstract: A major contributor to resource degradation on rangelands in the western United States is the expansion of undesirable non-native annual weeds following wildfire or other disturbance. The purpose of this study was to simulate near-surface soil temperature and water conditions for predicting potential seed germination response for post-fire, revegetation applications. The Simultaneous Heat And Water (SHAW) model was applied to three soil types (sandy loam, loamy sand, silt loam) instrumented with soil moisture and temperature sensors. Simulation results using three methods of parameter estimation were compared to determine the effect of model-parameter uncertainty on germination prediction. Near-surface soil temperatures were accurately simulated with model efficiencies of 0.89 to 0.96 for the 2-cm depth. Initial parameter estimates of the sandy loam soil yielded relatively poor soil water potential estimates, which resulted din an underprediction of germination times by 4.7 days for cheatgrass to 12.8 days for bluebunch wheatgrass. Model simulations based on measured moisture-release curves resulted in germination prediction within a few days of estimates based on measured temperature and water conditions for the loamy sand site. Predicted germination on the silt loam site was within 0.7 days for the initial simulation and within 3.8 days using measured moisture release curve parameters. Long-term simulation of seedbed microclimate in the field is necessary to evaluate potential germination response of revegetation species and their weedy competitors. Using a germination model to assess alternative soil parameterization scenarios allows one to optimize seedbed model output for this specific application.

Last Modified: 11/28/2014
Footer Content Back to Top of Page