The role of stored carbohydrates and nitrogen in the growth and stress tolerance of planted forest trees

Plants store compounds that supplement external resources to maintain primaryfunctions. We reviewed the role of stored non-structural carbohydrates (NSC) and nitrogen(N) in juvenile woody species for spring growth and cold and drought stress tolerance,which are crucial processes for early performance of forest plantations. Plant functionaltypes differed in NSC and N partitioning and allocation to new growth. In general,however, new leaves/shoots were more enriched in remobilized resources than new fineroots. Conifers used less remobilized resources than broadleaf species for fine root growth.New shoots/leaves were mostly comprised of remobilized N ([60 %) in conifers andbroadleaf deciduous species, while broadleaf evergreens relied more on soil N (\50 %remobilized N). In contrast, few differences among functional groups existed in the contributionof remobilized carbon (C) to new leaves/shoots, which comprised 28&-45 % ofstored C reflecting the importance of current photosynthesis and distinctions in C and N remobilization physiology. Organ source strength for remobilized N was positively related to its contribution to seedling N content. However, leaves are priority N sources in evergreens, which remobilized more N than predicted by their contribution to seedling N content. In contrast, roots in broadleaf evergreens and conifers were poor contributors of remobilized N. Under low stress, spring growth has little effect on NSC reserves. However, prolonged and intense photosynthesis depression strongly reduces NSC. In contrast, N reserves usually decline after planting and their replenishment takes longer than for NSC reserves. Strong storage reduction can hinder seedling stress acclimation and survival capacity. Accumulation of stored resources can be promoted in the nursery by arresting plant growth and supplying resources at a higher rate than seedling growth and maintenance rate. We conclude that the way in which woody plants manage stored resources drives their growth and stress tolerance. However, plant functional types differ in storage physiology, which should be considered in silvicultural managementMinisterio de Ciencia e InnovaciónComunidad de MadridUniversidad de Alcal

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

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

Seedling establishment in a deciduous and an evergreen oak under simulated climate change

Climate change constitutes a major threat to global biodiversity and to the success of natural and assisted tree regeneration. Oaks are among the most emblematic tree species in the Northern Hemisphere, so it is crucial to understand the impact of changing climate on seedling recruitment and early development. In this study, we investigated the effect of air warming on the early development of one deciduous species – Quercus faginea – and one evergreen species – Quercus ilex subsp. ballota. Acorns of both species were seeded in an alluvial valley in southern Spain and subjected to an air warming treatment with Open-Top Chambers (OTC), which increased air temperature by 2ºC. We monitored seedling emergence, growth, chlorophyll concentration, and mortality in the first growing season. The simulated climate change treatment accelerated plant emergence in early spring, reduced spring shoot growth, and increased mortality from ~23% in control plots to ~40% inside OTCs. Although Q. ilex and Q. faginea are sympatric species, Q. faginea showed lower performance under simulated climate change in terms of growth. In addition, acorn fresh weight was positively related with the probability and speed of emergence (only for Q. faginea), seedling size, and relative chlorophyll content, and plants that emerged earlier had a greater likelihood of surviving. In short, larger acorns partly counter-balanced the negative impact of temperature increase on plants. This study highlights the importance of understanding plant response to climate change both to forecast potential changes in species composition and to choose adequate species and traits such as acorn size in restoration projectsThis work was funded by the Spanish Ministerio de Ciencia, Innovación y Universidades/ FEDER (grant RTI2018-096187-J-100); the Spanish Ministerio de Universidades/ NextGerentationEU (grant Margarita Salas); Ministerio de Ciencia e Innovación/ NextGerentationEU (grant TED2021.130976B.I00); and Consejería de Economía, Conocimiento, Empresas y Universidad de la Junta de Andalucía/ FEDER (grant P18-RT-1927)

Foliar absorption and root translocation of nitrogen from different chemical forms in seedlings of two Mediterranean trees.

Along with root uptake, plants can also absorb N through leaves. There are few comparative studieson the foliar absorption of N from different chemical forms of N in forest tree species. We comparedthe foliar N absorption capacity in seedlings of two forest trees widespread in the Mediterranean basin,Quercus ilex and Pinus halepensis. Plants were sprayed with the following individual N forms at 40 mMN:15N-nitrate (NO3−),15N-ammonium (NH4+),15N-urea or13C and15N dual-labeled glycine. Cuticularconductance was used as a surrogate of cuticle permeability to water. Q. ilex had higher N foliar absorp-tion than P. hapelensis. Neither cuticular conductance nor shoot surface area explained N differences inabsorption rate between species, which were instead likely linked to differences in stomatal density andpresence of trichomes. In both species, foliar N absorption rate and N recovery differed among N forms:urea > NH4+≥ glycine ≥ NO3−. Differences in N absorption rate among N forms were correlated with theirphysico-chemical properties. The strong positive relationship between15N and13C uptake together withdetection in shoots of intact dual-labeled glycine (measured by gas chromatography&#-mass spectrome-try), indicated that a significant fraction of glycine was absorbed intact by the seedlings. In both species,higher cuticular conductance was related to faster N absorption from all forms except NO3&;8722#. Cuticularconductance had a stronger effect on N absorption from urea and NH4+than N absorption from glycine,and the effects were more intense in Q. ilex than in P. halepensis.Comunidad de MadridAustralian Research Counci

Root uptake of inorganic and organic N chemical forms in two coexisting Mediterranean forest trees

Background and aims Plants differ in their ability to usedifferent nitrogen (N) chemical forms, these differencescan be related to their ecology and drive communitystructure. The capacity to uptake intact organic N hasbeen observed in plants of several ecosystems. However,soil organic N uptake by Mediterranean plants is unknowndespite organic N being abundant inMediterranean ecosystems. We compare the uptake ofdifferent N forms in two widespread coexistingMediterranean forest trees with contrasting ecophysiologicalcharacteristics: Quercus ilex and Pinus halepensis.Methods To estimate root uptake rate of eachN form weused equimolar solutions (1 mM N) of 15NO3-, 15NH4+ and 15N-13C glycine.Results NH4+ and glycine were taken up at a similarrate, but faster than NO3− in both species. Intact duallabeled glycine was found in both species, demonstratingthat both species can absorb intact organic N. Conclusions: Despite their ecological differences, both species had similar preference for N forms suggesting no niche complementarity for N uptake. The higher preference for NH4 + and glycine over NO3 - possibly reflects adaptation to the differing proportions of N forms in Mediterranean soils.Ministerio de Educación y CienciaMinisterio de Ciencia e InnovaciónMinisterio de Economía y CompetitividadComunidad de Madri

Nitrogen form and concentration interact to affect the performance of two ecologically distinct Mediterranean forest trees

Most studies examining inorganic N formeffects on growth and nutrition of forest trees have beenconducted on single species from boreal or temperateenvironments, while comparative studies with species fromother biomes are scarce. We evaluated the response of twoMediterranean trees of contrasting ecology, Quercus ilex L.and Pinus halepensis Mill., to cultivation with distinctinorganic N forms. Seedlings were fertilized with differentNH4?/NO3- proportion at either 1 or 10 mM N. In bothspecies, N forms had small effects at low N concentration,but at high N concentration they markedly affected theplant performance. A greater proportion of NH4? in thefertilizer at high N caused toxicity as it reduced growth andcaused seedling death, with the effect being greater in Q.ilex than in P. halepensis. An increase in the proportion ofNO3- at high N strongly enhanced growth relative to lowN plants in P. halepensis but had minor effects in Q. ilex.Relatively more NH4? in the fertilizer enhanced plant Pconcentration but reduced K concentration in both species,while the opposite effect occurred with NO3-, and these effects were enhanced under high N concentration. We conclude that species responses to inorganic N forms were related to their ecology. P. halepensis, a pioneer tree, had improved performance with NO3 - at high N concentration and showed strong plasticity to changes in N supply. Q. ilex, a late successional tree, had low responsiveness to N form or concentration.Ministerio de Educación y CulturaMinisterio de Ciencia e InnovaciónComunidad de Madri

Manual de prácticas y Seminarios de Ecología. (2º de Grado en Ciencias Ambientales)

144 p

Ecophysiology of nitrogen in Mediterranean plants: strategies of nitrogen absorption, functional responses, and use of reserves for growth

Oliet Palá, Juan A., codir.El agua y la luz son considerados los principales recursos que condicionan la estructura y funcionamiento de las comunidades de ecosistemas mediterráneos. Sin embargo, la adquisición, el uso y la respuesta funcional a las distintas formas químicas de N podrían diferir entre las plantas mediterráneas, lo que contribuiría a explicar la alta diversidad taxonómica y funcional en ecosistemas mediterráneos. El objetivo general de esta Tesis es estudiar las estrategias de adquisición de las distintas formas químicas del N, el patrón de distribución y uso de las reservas de N y C, así como la respuesta morfo-fisiológica a las fuentes de N en plantas forestales mediterráneas. La hipótesis general de la Tesis es que el N juega un papel central en la ecología de las especies forestales mediterráneas, ya que éstas difieren su estrategia de uso del N en base a sus características funcionales. Para ello, se han estudiado tres principales procesos de la economía del N en las plantas: adquisición (tanto por vía radical -Capítulo 2- como foliar - Capítulo 3), distribución y removilización (Capítulo 4) y el efecto de las fuentes de N en el desarrollo vegetal (Capítulo 5). La conclusión general de esta Tesis es que las especies forestales mediterráneas presentan distintas capacidades de absorción y respuesta a las formas químicas de N, así como diferente uso de las reservas de N para apoyar el crecimiento de los nuevos órganos. Se demuestra que los aminoácidos son una fuente de N potencialmente importante en ecosistemas mediterráneos, ya que su abundancia en suelos es tan alta como la del N inorgánico y las especies mediterráneas son capaces de absorberlos intactos. Finalmente, las diferencias en la utilización de N pueden condicionar la velocidad de crecimiento de las plantas, un atributo clave para su eficacia biológica. Todo ello indica que las plantas mediterráneas tienen nichos fundamentales diferentes en base al uso del N y sugiere que este nutriente juega un papel significativo en la estructura y funcionamiento de las comunidades vegetales mediterráneas

Importancia de las reservas de nitrógeno para el crecimiento de las plantas leñosas mediterráneas en primavera. Implicaciones para el cultivo en vivero.

International audienc

Importancia de las reservas de nitrógeno para el crecimiento de las plantas leñosas mediterráneas en primavera implicaciones para el cultivo en vivero.

International audienc