Influence of Soil Water Repellency on Seedling Emergence and Plant Survival in a Burned Semi-Arid Woodland

High intensity wildfires in semiarid shrub and woodland plant communities can leave ecosystems incapable of self-repair and susceptible to weed invasion. Subsequently, land managers need effective restoration tools to reseed native vegetation back into these degraded systems. 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 greenhouse study using soil cores obtained from beneath burned Juniperus osteosperma trees. Soil cores were seeded with either Elymus wawawaiensis or Agropyron cristatum, and watered with either a high (watered daily) or a low water regime ( watered every 5 days). During the first watering event, water repellency was ameliorated in half the cores by adding a wetting-agent comprised of alkylpolyglycoside-ethylene oxide/propylene oxide block copolymers. Results showed that water repellency reduced seedling emergence and seedling survival by decreasing soil moisture availability. Wetting-agents improved ecohydrologic properties required for plant growth by decreasing runoff and increasing the amount and duration of available water for seedling emergence, survival, and plant growth. These results indicate that soil water repellency can act as an ecological threshold by impairing establishment of reseeded species after afire. Where restoration efforts are limited by soil water repellency, wetting agents have the potential to improve the success of post-fire reseeding efforts. Future work is needed to validate these findings in the field.