Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2011
Publication Date: 3/1/2012
Publication URL: http://naldc.nal.usda.gov.d2.nal.usda.gov/catalog/54236
Citation: Madsen, M.D., Petersen, S.L., Roundy, B.A., Hopkins, B.G., Taylor, A.G. 2012. Comparison of postfire soil water repellency amelioration strategies on bluebunch wheatgrass and cheatgrass survival. Rangeland Ecology and Management. 65(2):182-188. Interpretive Summary: Reseeding pinyon-juniper woodlands after a fire can be an effective method for restoring desired plant communities. However, post-fire soil water repellency may have the potential to limit these reseeding efforts and promote cheatgrass invasion. In a glasshouse study, we evaluated revegetation success of a native grass and an invasive weed sown in water repellent soil, and compared the effectiveness of wetting agents and anchor chaining for improving plant growth and survival. Wetting agents were sprayed onto the soil during the first watering. Anchor chaining was simulated by tilling the soil. Results indicate that soil water repellency significantly reduces seedling emergence and plant survival of both species tested. Wetting agent and simulated anchor chaining treatments increased soil water content, plant density, and above and below ground plant biomass. This study increases the knowledge base of how soil water repellency influences revegetation success and has implications for land managers conducting rangeland reseedings.
Technical Abstract: Soil water repellency may significantly limit site recovery following wildfire. This study was designed to compare survival and growth of the native plant species bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) A. Löve) to the invasive annual weed cheatgrass (Bromus tectorum L.), and to compare the effectiveness of wetting agents and anchor chaining for improving plant survival and growth in water-repellent soil. Research was performed in a glasshouse using soil cores obtained from the subcanopy of burned juniper (Juniperus osteosperma (Torr.) Little) trees. Three treatments plus a control were tested in a randomized split-plot design: (1) control, (2) simulated anchor chaining (hereafter referred to as “till”), (3) wetting agent, and (4) till + wetting agent. Response variables measured included: soil water content, plant density, above and below-ground biomass, and soil and plant nitrate levels. Overall, response of bluebunch wheatgrass and cheatgrass was similar among treatments. Wetting agent and tilling both increased soil water content, with wetting agent significantly higher than the till treatment. Plant density was also highest in the wetting agent treated soil, and the till treatment was higher than the control. Cheatgrass plants grown in soil treated with wetting agent appeared to show signs of nitrogen deficiency. Subsequent analysis showed soil receiving the wetting agent treatment had significantly lower nitrate concentrations. Similarly, nitrate in cheatgrass biomass was lower in the wetting agent treatment in comparison to untreated soil. However, for bluebunch wheatgrass there was no significant difference in nitrate between the treatments. This study suggests that soil water repellency decreases soil water availability, which influences revegetation of both cheatgrass and bluebunch wheatgrass. Application of wetting agents promotes bluebunch wheatgrass survival. Further research is merited for determining the implications of water repellency on soil nutrient retention and cheatgrass survival, and evaluating these water repellency amelioration strategies in the field.