An exponential fertilization dose–response model to promote restoration of the Mediterranean oak Quercus ilex

Abstract

Nursery nitrogen (N) fertilization influences seedling N reserves, morphology, photosynthesis rate and stress tolerance and frequently enhances outplanting performance. Although mineral nutrition is a critical aspect of seedling quality, fertility targets of Mediterranean sclerophylous species have not been thoroughly quantified. We sought to define those fertility targets for seedlings of Quercus ilex, a key species in Mediterranean areas. Nine fertility treatments, ranging from 0 to 200 mg N seedling -1 applied under an exponential regime were tested in a greenhouse dose response trial in which phosphorus (P) and potassium (K) were increased in the same proportion as N (15N:5P:15K). Height and diameter growth were measured weekly, and biomass and nutritional status were analyzed at the end of culture (24 week). Plant growth and nutritional response to increased fertilization followed a curvilinear pattern depicting phases that ranged from deficiency to luxury consumption. Seedling dry mass production was maximized at 125 mg N seedling -1 (sufficiency level). N content and concentration increased with fertilization, reaching a maximum at 200 mg N seedling -1 (luxury consumption). P and K concentrations peaked at 75 and 25 mg N, respectively, suggesting a dilution effect of these nutrients. Root volume increased linearly up to 100 mg N and declined thereafter. The sufficiency level for Q. ilex (125 mg of applied N seedling -1 ) is notably higher than for other Quercus species from other biomes but intermediate to other Mediterranean Quercus species. No toxicity was observed at the highest treatment rate (200 mg N) suggesting that increased exponential N rates along with greater P and K proportions than those used in our experiment may further maximize nutrient storage.

Fertilisation of Quercus seedlings inoculated with Tuber melanosporum: effects on growth and mycorrhization of two host species and two inoculation methods

“…The response of non-inoculated Q. ilex seedlings to fertilisation follows a pattern similar to other Mediterranean Quercus such as Q. faginea, but different from Quercus from other biomes which show lower sufficiency levels (Uscola et al 2015). Castellano & Molina (1989) warned that response of EM fungi to fertilisation was influenced not only by the dose but also by fertiliser type and form, as well as application system (timing, rate and method).…”

Restoring forests: regeneration and ecosystem function for the future

“…Stocktypes, fertilization or irrigation regimes and hardening practices can be manipulated in the nursery to tailor morphological and physiological seedling attributes to optimize performance under the conditions of a given outplanting site (Grossnickle and El-Kassaby 2015;Dumroese et al 2016). Seedling size is positively correlated with plant content of nitrogen and carbohydrates and seedlings may remobilize these stored reserves in order to resist environmental stresses on the planting site (Villar-Salvador et al 2015;Uscola et al 2015). Thus, while a shift away from planting older and larger seedlings toward younger and smaller seedlings has occurred in some boreal regions (Löf 2017), the opposite trend prevails for restoration under harsh, dry site conditions, such as in Mediterranean regions (Villar-Salvador et al 2012).…”

Nursery Cultural Techniques Facilitate Restoration of Acacia koa Competing with Invasive Grass in a Dry Tropical Forest

“…For example, taller seedlings are more competitive on sites with high vegetative competition that limit light [18][19][20][21][22], and seedlings with large root systems [16,23,24], and balanced shoot-to-root ratio to reduce transpirational demand [25,26] may perform better on drought-prone sites. Nursery fertilization regimes may also be adjusted to optimize nutrient levels in seedlings, often through inducing luxury nutrient consumption [27][28][29][30]. Thus, through the manipulation of cultural conditions (e.g., container volume or configuration; fertilization or irrigation regimes), forest nurseries can produce a wide variety of stocktypes tailored to perform well on a given outplanting site [13,[31][32][33][34].…”