Respuestas ecofisiológicas y demográficas de "Quercus Ilex" L. a alteraciones del balance facilitación-competencia del matorral en un ambiente semiárido

Abstract

The forest restoration after the elimination of 852 ha of eucalyptuses in Monfragüe National Park allowed us to study shrub-holm oak seedling interactions, and the long-term effects of the eucalyptuses over the soil. Two main research objectives were addressed: long term monitoring of the soil properties and performance of shrubs and oak seedlings. We used two levels of approach: (1) Intensive study of shrub-oak seedling interactions, in which three cohorts of 1000 seedlings were monitored under four experimental treatments (control, shade, shrub cut down and ploughed). (2) Extensive study of soil properties and vegetation (shrubs and oak seedlings) recover: we monitored soil properties, growth and survival of 2000 seedlings in 20 permanent plots in each soil treatment. Two soil treatment based on the soil alteration were used in the elimination-afforestation settings: �Intense� (low slope, terraces and eucalyptuses eliminated by ploughing) and �Moderate� (high slope, pre-existing terraces conserved and eucalyptuses eliminated individual). Forest operation and eucalyptuses decreased chemistry soil fertility. The Intense treatment increased the gully and laminate erosion, the subsurface density and nitrogen loss. This scenario increased survival of the plantation but limited natural regeneration of the shrubs as compared to the Moderate treatment. Deer browsed intensively in both scenarios, thus limiting the seedling growth. The competitive effects exercised by rock-rose out-weighted facilitation effect via microclimate. Hence its use as nurse plants does not seem advisable in the semiarid environment. Natural regeneration of oaks increased at intermediate shrub density, where competition was less intense. These results could allow a better design of restoration techniques in future interventions.