Problems and solutions to cork oak (Quercus suber L.) regeneration: a review

Abstract

Biogeosciences and Forestry Biogeosciences and ForestryProblems and solutions to cork oak (Quercus suber L.) regeneration: a review Taher Mechergui (1-2) , Marta Pardos (3) , Naceur Boussaidi (2) , Douglass F Jacobs (4) , Filipe Xavier Catry (5) This study aimed to review the requirements and difficulties of natural and artificial regeneration of cork oak (Quercus suber L.) in the Mediterranean Basin. Cork oak regeneration is achieved naturally by means of sexual or vegetative reproduction (by seeds or by sprouting), or artificially through direct seeding, or seedling planting. Both natural and artificial regeneration of cork oak frequently encounter numerous difficulties which limit the ecological conditions for cork oak regeneration, including acorn predation, slow growth, vegetative competition, browsing of seedlings, fires, pests and diseases, and summer drought. We reviewed the state of the art of these difficulties and s ummarize the potential solutions for each regeneration form.

Spicing up oak forest restoration: a preliminary report of the protective use of chili peppers in direct seeding of acorns

“…Our results show that acorns introduced into Capsicum fruits germinated at the same rate as uncovered acorns under both greenhouse and field conditions. The germination speed of acorns has also been related to acorn predation probability since faster germination and seedling emergence allow a greater proportion of acorns to escape predation by reducing the time of exposure to predators, such as mice (Mechergui et al 2023; García‐Hernández & López‐Barrera 2024). Oak species with acorns that germinate immediately upon seed fall (white oaks such as Quercus germana ) are detected by squirrels due to their odor, and the embryos are removed before the seeds are cached.…”

“…The most significant result from the greenhouse trial was that the seedling emergence of Q. germana acorns introduced into Capsicum pubescens fruits doubled in value compared to unprotected acorns. Acorns from humid forest oak species tolerate desiccation to only a very small extent, and their ability to emerge can decrease rapidly with even small losses of moisture (Mechergui et al 2023; Liu et al 2024). Our results could be related to the stability in humidity conferred by the Capsicum fruits to the acorn surface, while the natural capsaicin contained in the fruit did not affect the embryo and plumule as reported by Leverkus et al (2013) when using a seed coating containing capsaicin.…”

“…In many ecosystems, acorns placed in humid substrates can germinate. Seedlings emerge even in the absence of light, but in open areas subject to variations in soil and air humidity, a lack or excess of humidity may also be detrimental to acorns exposed either to desiccation or to fungal attacks and decomposition (Mechergui et al 2023; García‐Hernández & López‐Barrera 2024; Liu et al 2024).…”

Seed Germination Characteristics of a Critically Endangered Evergreen Oak—Quercus marlipoensis (Fagaceae) and Their Conservation Implications

“…Temperature and moisture (water potential) are the key environmental factors impacting seed germination [12,29]. Oak seeds are mostly recalcitrant, with a moisture content of 30%-55%, and seed moisture loss significantly decreases the germination ratio [30][31][32][33][34]. The majority of seeds exhibit rapid germination and continuously maintain high activity without dormancy characteristics post-maturation [35,36]; however, a small percentage of oak seeds may undergo dormancy [37], influenced by the effects of growth regulators, pericarp restrictions, or a combination of both [38,39], breaking dormancy in oak seeds typically requires stratification or pericarp abrasion [40].…”