ARS | Publication request: MODELING NEAR-SURFACE SOIL TEMPERATURE AND MOISTURE FOR SEEDLING GERMINATION RESPONSE

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Proceedings
Publication Acceptance Date: February 14, 2000
Publication Date: N/A

Technical Abstract: A major contributor to resource degradation on western rangelands lands is the invasion of undesirable non-native annual weeds following wildfire or other disturbance. Critical factors determining the success of seeding efforts are the spatial and temporal distribution of soil heat and water relative to germination and growth response of both desirable and undesirable plant species. This study demonstrates the utility of the Simultaneous Heat And Water (SHAW) model for addressing seedling germination processes for post-fire revegetation applications by assessing its ability to simulate soil temperature and water content. The model was also applied to three bare soil plots representing a post-fire revegetation scenario. The three plots had widely varying soil textures and were instrumented with soil water and temperature profiles. The root-mean- square deviation (RMSD) between measured and simulated temperatures for the emonths of March through May for all three plots ranged from approximately 3.5 C for near surface depths to 0.4 C for 100-cm depths. Uncalibrated runs using soil parameters based solely on texture yielded an RMSD for the 2-cm soil water content of 0.02 cm3/cm3 for the clay loam site, 0.05 cm3/cm for the sandy loam site, and 0.03 for the loamy sand site. Simulations using soil parameters based on moisture release curve data resulted in an RMSD for 2-cm water content of 0.02 to 0.03 cm3/cm3. RMSD for between simulated estimated soil water potential at a depth of 2 cm ranged between 3 to 5 bars for the three plots. The effect of the uncertainty in simulated soil temperature and water potential on the timing of seedling germination was investigated using a seed germination model.