Incorporating restoration in sustainable forestry management:: Using pine-bark mulch to improve native species establishment on tephra deposits

Native plant establishment is limited by harsh environmental conditions in areas affected by tephra deposition following volcanic eruptions. Late-successional species might be lacking even decades after the disturbance. We assessed the effectiveness of pine-bark mulch, a by-product of sustainable timber production in the study area, in promoting the establishment and survival of a late-successional species (Pinus pseudostrobus) and a nitrogen-fixing legume (Lupinus elegans). We established a factorial experiment in areas covered with tephra during the eruption of the Paricutin volcano in the state of Michoacan, Mexico. After 1 year, P. pseudostrobus survival was significantly higher (p < 0.001) in plots with pine-bark mulching (46.5%) than in plots without mulching (21.8%). After 2 years, surviving pines with mulching were significantly taller (p= 0.03) than pines without mulching (45.3 +/- 3.8 cm and 31.2 +/- 3.7 cm, respectively). Lupinus elegans plants survived longer when grown in plots with pine-bark mulching than without mulching. Mulching reduced tephra temperatures during the dry season (when temperatures can reach up to 58 degrees C 4 cm below the surface of bare tephra). Lupinus elegans plants were affected by herbivory by small rodents, run-off, and frost at the end of the growing season. Our results suggest that mulching can ameliorate harsh environmental conditions on sites covered with tephra while incorporating a by-product of sustainable forestry into restoration practice.