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

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

Fast growth involves high dependence on stored resources for shoot growth in Mediterranean evergreen trees

Background and Aims The carbon (C) and nitrogen (N) needed for plant growth can come either from soil Nand current photosynthesis or through remobilization of stored resources. The contribution of remobilization to neworgan growth on a whole-plant basis is quite well known in deciduous woody plants and evergreen conifers, but thisinformation is very limited in broadleaf evergreen trees. This study compares the contribution of remobilized C andN to the construction of new organs in spring, and assesses the importance of different organs as C and N sources in1-year-old potted seedlings of four ecologically distinct evergreen Mediterranean trees, namely Quercus ilex, Q.coccifera, Olea europaea and Pinus hapelensis. Methods Dual 13C and 15N isotope labelling was used to unravel the contribution of currently taken up and storedC and N to new growth. Stored C was labelled under simulated winter conditions. Soil N was labelled with the fertilizationduring the spring growth. Key results Oaks allocated most C assimilated under simulated winter conditions to coarse roots, while O. europaeaand P. halepensis allocated it to the leaves. Remobilization was the main N source (>74 %) for new fine-rootgrowth in early spring, but by mid-spring soil supplied most of the N required for new growth (>64 %). Currentphotosynthesis supplied >60 % of the C in new fine roots by mid-spring in most species. Across species, the proportionof remobilized C and N in new shoots increased with the relative growth rateComunidad de MadridMinisterio de Educación, Cultura y Deport

Minority grapevine varieties as climate change adaptation strategy: Exploring heat tolerance plasticity

Climate change is increasing average temperatures and intensity and frequency of extreme eventssuch as heat waves. Productivity declines and plant damage due to those changes are already described for severalmajority varieties, especially in the Mediterranean basin. Less explored minority varieties can arise asalternatives due high heat tolerance, or for having high acclimation potential to heat. We evaluated the heattolerance after acclimation in three summer thermic environments of four Spanish varieties: two majority(Tempranillo, Airén) and two minority (Jarrosuelto, Morate). Summer thermic environments differed inaverage temperature, and length of the warm period. Varieties differed in heat tolerance and its plasticity due tothe acclimation to the environments. Within the majority varieties, Tempranillo showed low heat tolerance andmoderate plasticity in heat tolerance highlighting its susceptibility to climate change. Airén had slightly highertolerance than Tempranillo and certain adaptation capacity to environments. Within the minority, Jarrosueltohad high tolerance to heat events but low heat tolerance plasticity. Morate was the variety with highest heattolerance plasticity, indicating its strong adaptive potential. Majority varieties displayed susceptibility to heatevents and global warming negative effects. However, minority varieties can offer solutions either by havinghigh tolerance to heat or by having high acclimatio