Submitted to: Arid Land Research and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2011
Publication Date: 9/17/2012
Publication URL: http://handle.nal.usda.gov/10113/56072
Citation: Madsen, M.D., Petersen, S.L., Fernelius, K.J., Roundy, B.A., Taylor, A.G., Hopkins, B.G. 2012. Influence of soil water repellency on seedling emergence and plant survival in a burned semi-arid woodland. Arid Land Research and Management. 26:236-249. Interpretive Summary: There is a high failure rate for post-fire rangeland reseedings. In order to develop successful restoration approaches, it is critical that we understand the factors that impair reseeding success. Hydrophobicity, or soil water repellency is commonly documented in rangeland ecosystems after a fire, but its influence on revegetation success is poorly understood. In this study we examined the influence of soil water repellency on reseeding success and evaluated the use of wetting-agents as a post-fire restoration approach. Research was performed in a glasshouse on soil collected under burned Utah juniper trees. Our results indicate that soil water repellency can significantly limit seedling emergence and survival through increased runoff, and decreased moisture availability. We also showed that wetting agents can enhance soil infiltration and moisture which increases seedling emergence and survival.
Technical Abstract: Despite post-fire reseeding efforts, Pinus-Juniperus (piñon-juniper) woodlands often become invaded by annual weeds that out-compete native species, degrade ecological processes, and modify natural fire patterns. In order to develop successful post-fire restoration approaches in these communities, it is critical that we understand the mechanisms that impair reseeding success. Our objective was to quantify the influence of soil water repellency on seedling emergence, and plant growth in a glasshouse study using soil cores obtained from underneath burned Juniperus osteosperma trees. Cores were seeded with either Elymus wawawaiensis (Snake River wheatgrass) or Agropyron cristatum (crested wheatgrass), and watered with either a high or a low water regime. During the first watering, water repellency was ameliorated in half the cores by adding a wetting agent comprised of alkylpolyglycoside-ethylene oxide/propylene oxide block copolymers. Results implied that water repellency reduced seedling emergence and seedling survival by decreasing soil moisture availability through: promoting runoff, decreasing soil moisture storage capacity, and disconnecting soil surface layers from underlying moisture reserves. Wetting-agents improved ecohydrologic properties required for plant growth by decreasing runoff and increasing the amount and duration of available water for seed germination and seedling survival. For example, at the conclusion of the study, seedling density of wetting agent treated cores were 292.0% and 49.6% higher than untreated soils, for low and high watering regimes, respectively. These results may indicate that in semi-arid environments, soil water repellency acts as a temporary ecological threshold by impairing establishment of reseeded species after a fire.