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Physiological Keys for Natural and Artificial Regeneration of Oaks

2017; Springer International Publishing; Linguagem: Inglês

10.1007/978-3-319-69099-5_14

2542-971X

Jesús García, Esteban Chirino, Josep María Espelta, Douglass F. Jacobs, Paula Martín, Rafael M. Navarro‐Cerrillo, Juan A. Oliet, Alberto Vilagrosa, Pedro Villar‐Salvador, Eustaquio Gil‐Pelegrín,

Botany and Plant Ecology Studies

OakOak forests can naturally regenerate from seedSeed or from sprouts. Both strategies result in the establishment of a tree layer, but they involve a crucial difference: i.e. regenerationRegeneration from seeds affects populationPopulation genetics while sprouting assures the recovery of biomassBiomass after a disturbance but it does not involve sexual reproduction. In addition the two regenerationRegeneration mechanisms differ in their complexity and are affected by different constraints: i.e. regenerationRegeneration from seedSeed is a more intricate pathway with several potential bottlenecks (e.g. seedSeed and micro-sites availability, predation, seedlingSeedling -saplings conflicts) while sprouting is a much more straightforward process benefiting from the presence of an already established rootRoot system and more independent from environmentalEnvironmental regulation stochasticity. Ultimately, regenerationRegeneration from seeds or sprouts will result in contrasting forest structures (respectively, high-forests and coppices) with a different functioning and dynamics and requiring particular forestry practices. When natural regenerationRegeneration is not possible, oakOak forest restorationRestoration must be done using artificial regenerationRegeneration by seedingSeeding or plantingPlanting (traditionally, both methods have been recommended), provided that acornAcorn predators are controlled. Although similar results have been obtained with regard to survivalSurvival , under Mediterranean conditions, shootShoot growth patterns clearly differ for both methods. Indeed, one-year seedlings often discontinue their shootShoot elongation shortly after transplantingTransplanting , especially under droughtDrought or competition. At this time, a new taprootTaproot and fine lateral roots are formed. This observation suggests that the seedingSeeding and plantingPlanting techniques may bear different consequences with regard to rootRoot system development, which may ultimately affect seedlingSeedling establishment. SurvivalSurvival and growth planted seedlings depends on morphological and physiological attributes (Burdett in Can J For Res 20:415–427, 1990; Villar-Salvador et al. in New For 43:755–770, 2012; Grossnickle in New For 43:711–738, 2012). CultivationCultivation techniques strongly determine the functional attributes of seedlings by manipulating the amount of resources (water, mineral nutrients, light, space) and the conditions (temperatureTemperature , growing medium pH, photoperiod) for seedlingSeedling growth. Consequently, how seedlings are cultivated impacts on the performance of forest plantations. CultivationCultivation practices improve the ''seedlingSeedling physiological potential'', increasing the chances of survivalSurvival immediately after field plantingPlanting . Each of these has an influence and interacts with the others (Ketchum and Rose in Interaction of initial seedling size, fertilization and vegetation control. Redding, CA, pp 63–69, 2000), which should be taken into consideration when evaluating a reforestation proposal; otherwise, artificial forest regenerationRegeneration often results in unacceptably poor seedlingSeedling performance. PlantingPlanting date and site preparation, since they increase water availability, have been shown to be the factors most relevant to the survivalSurvival of Mediterranean species. However, in less restrictive conditions, the use of less intensive soilSoil preparation, on dates more favorable to the initial growth of the seedlings in the field, might be more efficient. Similarly, the use of tree shelters in oaks plantations is under debate, as its effects are species and environmental dependent. A better understanding of the ecophysiological seedlingSeedling response under the microenvironment of the tree shelterShelter is needed to improve the management of this protection tool. On the other side, the effects of cultivationCultivation practices can be linked closely to newly established seedlings (the post-plantingPlanting phenological cycle), and such benefits are ephemeral in nature; thus, the effects of cultivationCultivation practices have their greatest importance during the initial growing seasons (1–2 years), diminishing with time.