Marta Pardos

La planta ideal: revisión del concepto, parámetros definitorios e implementación práctica

El objetivo de este articulo es examinar de una forma ordenada lo que constituye una planta ideal y como concretar este concepto en un programa operacional. Con el fin de alcanzar estos objetivos se discuten, en primer lugar, varios conceptos: la influencia de las practicas culturales en vivero sobre las caracteristicas de la planta, la fenologia de la misma, y los procesos implicados en la supervivencia y crecimiento en campo. A continuacion, se pasa revista a algunos de los posibles atributos de estado y de comportamiento de la planta que pueden servir para definir la planta ideal. Finalmente, se presentan las lineas maestras de lo que constituiria un programa operacional de planta ideal.

Freezing injury in primary and secondary needles of Mediterranean pine species of contrasting ecological niches.

Abstract• Pine seedlings show a marked ontogenetic difference between primary and secondary needles, the latter prevailing with a different timing among species.• Using the electrolyte leakage method following an artificial freezing test, we aimed at (1) determining the differences in freezing tolerance between primary and secondary needles in eight pines of contrasting thermal habitats: P. canariensis, P. pinea, P. halepensis, P. brutia, P. pinaster, P. nigra, P. sylvestris and P. radiata, (2) evaluating the relation between freezing tolerance and sclerophylly and (3) relating freezing tolerance with the climate of origin.• Primary needles were significantly more sensitive to freezing than secondary needles in Pinus halepensis, P. brutia, P. pinaster and P. nigra, whereas no differences were found in P. canariensis, P. pinea and P. radiata. LT50 was uncorrelated with needle sclerophylly but very highly correlated with the mean temperature of the coldest month at the seed source.• Results support an adaptive role of secondary needles in the mountain Mediterranean pines P. nigra, P. pinaster and P. brutia, while the more complex responses in coastal Mediterranean pines can be interpreted in the light of seedling ontogeny and species’ ecological niches.Résumé• Les jeunes plants de pin présentent une nette différence ontogénétique entre aiguilles primaires et secondaires, les secondes devenant dominantes après des délais variables selon les espèces.• À l’aide d’une expérience de gel artificiel et à l’aide de la méthode de perte d’électrolyte, nous avons visé à : (1) déterminer les différences de tolérance au gel entre aiguilles primaires et secondaires de huit espèces de pins présentant des habitats thermiques contrastés : P. canariensis, P. pinea, P. halepensis, P. brutia, P. pinaster, P. nigra, P. sylvestris et P. radiata, (2) évaluer la relation entre tolérance au gel et degré de sclérophyllie, et (3) mettre en relation tolérance au gel et climat d’origine.• Les aiguilles primaires étaient beaucoup plus sensibles au gel que les aiguilles secondaires chez Pinus halepensis, P. brutia, P. pinaster et P. nigra, alors qu’aucune différence n’a été constatée chez P. canariensis, P. pinea et P. radiata. La température induisant 50 % de mortalité n’était pas corrélée avec la sclérophyllie des aiguilles mais très fortement avec la température moyenne du mois le plus froid de la provenance des semences.• Les résultats corroborent l’idée d’un rôle adaptatif des aiguilles secondaires des pins méditerranéens montagnards P. nigra, P. pinaster et P. brutia, tandis que les réponses plus complexes des pins méditerranéens côtiers peuvent être interprétées à la lumière de l’ontogénie des semis et des niches écologiques des espèces.

Shoot growth components and flowering phenology in grafted Pinus halepensis Mill.

Shoot elongation and flowering were assessed for a season (January–November) in 25 grafts from five clones of Pinus halepensis growing in a seed orchard. A co-dominant shoot from the upper crown and a dominated, low shoot were measured from each ramet. Upper shoots elongated continuously from a variable onset date between January and March and followed a logistic function against Julian day and a Gompertz function against heat sum above 0°C. Three to seven (averaging five) successive cycles were formed through the growing season; usually, two of them were preformed in the terminal bud (spring cycles) and one to four were neo-formed, summer cycles. The number of summer cycles and their contribution to the annual shoot growth were the only variables with a significant clonal influence. Ovulate strobili appeared from February to April and in October. Some ramets showing two female flowering cycles in the same shoot were observed. Lower shoots, bearing pollinate strobili always displayed a single spring cycle preformed in the winter bud.

Future ecosystem services from European mountain forests under climate change

Summary 1.Ecosystem services (ES) from mountain forests are highly relevant for human societies. ES with a direct economic support function (e.g. timber production), regulatory services (e.g. protection from natural hazards) and cultural services (e.g. recreation) are likely to be affected strongly by a rapidly changing climate. To evaluate whether adverse climate change effects on ES can be counteracted by adapting management, dynamic models and indicator-based assessments are needed. 2.We applied a forest dynamic model in case study areas of four European mountain regions and evaluated the future supply of four ES - timber production, carbon sequestration, biodiversity, and protection against natural hazards - using state-of-the-art ES indicators. Forest dynamics were simulated under three management scenarios (no management, business-as-usual, and alternative management) and five climate change projections for selected representative stand types in each region. We analysed potential trade-offs and synergies between ES, and evaluated future changes among regions, forest stands, climate and management scenarios. 3.Impacts of climate change on the provision of multiple ES were found to be highly heterogeneous and to depend on the region, site, and future climate. In the absence of large-scale natural disturbance (not considered), protection services, carbon stock and deadwood abundance (proxy for biodiversity) benefitted from no management in all regions. Negative impacts of climate change were evident for the provision of multiple ES but limited to the most severe climate scenarios and low-elevation stands. Synergies and trade-offs between the majority of ES were found to be sensitive to the choice of management strategy and – in some regions – to climate change. 4.Synthesis and applications. Management regimes in European mountain forests should be regionally adapted to stand and site conditions. Although in some cases alternative management regimes may be more suitable than current management for supporting multiple ecosystem services, adaptation options should be evaluated carefully at the local scale due to the highly different magnitude of the impacts of climate change in different regions and along elevation gradients. This article is protected by copyright. All rights reserved.

Growth, nutrient, water relations, and gas exchange in a holm oak plantation in response to irrigation and fertilization

Abstract.Eighty 6-years-old Quercus ilex L. subsp. ballota seedlings planted on a former agricultural land were subjected during two growing seasons to one of four treatments: fertilization and irrigation, irrigation, fertilization, and control. Seasonal and between-treatment variations on water relations, gas exchange parameters, growth and nutrient status were analyzed. Water potential (Ψ) was related to climatic conditions. Thus, the frequent rain storms during the summer allow seedlings to maintain relatively high Ψ values, joined to moderate photosynthetic activity. Differences on Ψ, photosynthesis and stomatal conductance due to irrigation were shown at the onset and end of growth, related with lower water availability. Fertilization had a greater effect on growth than irrigation. Both fertilization and irrigation positively affected the relative increment on leaf nutrient concentration at the end of the second year. The results indicate that water availability was not a limited factor, thus irrigation is not justified; while fertilization improve growth.

Difference in cuticular transpiration and sclerophylly in juvenile and adult pine needles relates to the species-specific rates of development

Pinus species show remarkable ontogenetic differences in needle morphology (heterophylly) between juvenile and adult vegetative phases. This developmental shift may play an adaptative role in their success under diverse habitats. As a first step to know the functional differences between each vegetative phase, we compared water loss through the cuticles of juvenile and adult needles of 21-month-old nursery-grown seedlings of nine hard pine species. Cuticular transpiration (CT), calculated after complete stomatal closure, was obtained by leaf-drying curves, and was related to leaf, ontogenetic and climatic parameters. The rate of cuticular transpiration (RCT) between juvenile and adult needles differed across pine species, and in particular segregated the Mediterranean species Pinus canariensis and P. halepensis, from the Eurasian P. uncinata and introduced species P. radiata. For these species, RCT was always higher in juvenile needles. The different leaf and ontogenic parameters studied were correlated with the variation in RCT among the nine pine species. We discuss this relationship in the light of the species ecology. Besides their possible adaptive interpretation, these results suggest an underlying need to consider the ontogenetic heterophylly when assessing functional traits in hard pine seedlings, in particular those traits that govern water relations.

The role of developmental stage in frost tolerance of Pinus pinea L. seedlings and saplings

ContextAlthough drought is generally considered the main environmental constraint in Mediterranean environments, the ability to acclimate to and tolerate frost in early developmental stages can be a determinant for seedling survival of many Mediterranean tree species like stone pine (Pinus pinea L.).AimsThe aim of this study was to assess the impact of the developmental stage of naturally regenerated stone pine individuals on tolerance to low temperature (LT) from summer to late autumn and in spring, at a highly continental site in central Spain. Specifically, we tested to what extent the differences in tolerance are related to shoot heteroblasty.MethodsWe assessed LT tolerance of needles from individuals at three age classes (class C1: seedlings, class C2: 4- to 8-year-old saplings and class C3: >9-year-old saplings) over nine dates from summer to spring.ResultsLT tolerance displayed severe seasonal trends and differed between age classes. It usually increased with sapling age. Such differences were tightly related to heteroblasty of the shoots. Our results point to a higher LT tolerance associated with larger leaf dry mass per unit area (LMA) values. No impact of late frosts on shoot growth rates was detected during this study.ConclusionsDevelopmental changes during early plant growth seem to play a role in frost tolerance of stone pine seedlings, a finding which furthers our understanding of regeneration dynamics in this species in areas with continental influence.

Interactive responses of Quercus suber L. seedlings to light and mild water stress: effects on morphology and gas exchange traits

Abstract• The combined effect of water stress and light on seedlings of forest species is a key factor to determine the best silvicultural and afforestation practices in the Mediterranean area.• The aims of this work was (1) to determine the optimal light level for the early development of cork oak seedlings under mild water stress and (2) to test if the combined effect of water stress and light followed the trade-off, the facilitation or the orthogonal hypothesis.• Shade reduced instantaneous photosynthetic rates and water use efficiency in cork oak. However, seedlings grown under moderate shade (15% of full sunlight) were capable to accumulate similar amount of biomass than those grown under more illuminated environments by increasing their specific leaf area. Absolute differences in net photosynthesis between light treatments were higher in well watered than in water stressed seedlings. However, the impact of both factors on overall growth was orthogonal.• We concluded that cork oak development is impaired under deep shade (5% of full sunlight) but it can be optimal under moderate shade (15% of full sunlight) even under moderate water stress. Implications of these patterns on regeneration, cultivation and afforestation of cork oak are discussed.Résumé• L’effet combiné du stress hydrique et de la lumière sur les semis est un facteur clé pour déterminer les meilleures pratiques pour la sylviculture et le reboisement dans la région méditerranéenne.• Le but de ce travail a été (1) de déterminer le niveau optimal de lumière pour le développement précoce des semis de chêne liège soumis à un stress hydrique modéré et (2) de tester si l’effet combiné du stress hydrique et de la lumière suit l’hypothèse de compensation, de facilitation ou d’orthogonalité.• L’ombre réduit le taux instantané de photosynthèse et l’efficience d’utilisation de l’eau chez le chêne liège. Cependant, les semis qui ont poussé sous une ombre modérée (15 % de la pleine lumière) ont été capables d’accumuler une biomasse totale similaire à celle des semis qui ont poussé sous de meilleures conditions d’éclairement en accroissant leur surface foliaire spécifique. Les différences absolues pour la photosynthèse nette, entre les traitements lumineux, ont été plus importantes pour les traitements bien alimentés en eau que pour les semis soumis à un stress hydrique. Cependant, l’impact des deux facteurs sur l’ensemble de la croissance a été orthogonal.• Nous en avons déduit que le développement du chêne liège est diminué sous une ombre profonde (5 % du plein éclairement) mais il peut être optimal sous une ombre modérée (15 % du plein éclairement) même en conditions de stress hydrique modéré. Les implications de ces modèles pour le chêne liège ont été discutées pour ce qui concerne la régénération, la culture et le reboisement.

Climatic factors control rodent seed predation in Pinus pinea L. stands in Central Spain

Abstract• ContextPinus pinea L. presents serious problems of natural regeneration in managed forest of Central Spain. The species exhibits specific traits linked to frugivore activity. Therefore, information on plant–animal interactions may be crucial to understand regeneration failure.• AimsDetermining the spatio-temporal pattern of P. pinea seed predation by Apodemus sylvaticus L. and the factors involved. Exploring the importance of A. sylvaticus L. as a disperser of P. pinea. Identifying other frugivores and their seasonal patterns.• MethodsAn intensive 24-month seed predation trial was carried out. The probability of seeds escaping predation was modelled through a zero-inflated binomial mixed model. Experiments on seed dispersal by A. sylvaticus were conducted. Cameras were set up to identify other potential frugivores.• ResultsDecreasing rodent population in summer and masting enhances seed survival. Seeds were exploited more rapidly nearby parent trees and shelters. A. sylvaticus dispersal activity was found to be scarce. Corvids marginally preyed upon P. pinea seeds.• ConclusionsSurvival of P. pinea seeds is climate-controlled through the timing of the dry period together with masting occurrence. Should germination not take place during the survival period, establishment may be limited. A. sylvaticus-mediated dispersal does not modify the seed shadow. Seasonality of corvid activity points to a role of corvids in dispersal.

Can CO2 enrichment modify the effect of water and high light stress on biomass allocation and relative growth rate of cork oak seedlings

To test whether the impact of an enriched-CO2 environment on the growth and biomass allocation of first-season Quercus suber L. seedlings can modify the drought response under shade or sun conditions, seedlings were grown in pots at two CO2 concentrations × two watering regimes × two irradiances. Compared to CO2, light and water treatment had greater effects on all morphological traits measured (height, stem diameter, number of leaves, leaf area, biomass fractions). Cork oak showed particularly large increases in biomass in response to elevated CO2 under low-watered (W−) and high-illuminated conditions (L+). Allocation shifted from shoot to root under increasing irradiance (L+), but was not affected by CO2. Changes in allocation related to water limitation were only modest, and changed over time. Relative growth rate (RGR) and net assimilation rate (NAR) were significantly greatest in the L+/W+ treatment for both CO2 concentrations. Changes in RGR were mainly due to NAR. Growth responses to increased light, water or CO2 were strongest with light, medium with water availability and smallest for CO2, in terms of RGR. The rise in NAR for light and water treatments was counterbalanced by a decrease in SLA (specific leaf area) and LMF (leaf mass fraction). Results suggest that elevated CO2 caused cork oak seedlings to improve their performance in dry and high light environments to a greater extent than in well-irrigated and low light ones, thus ameliorating the effects of soil water stress and high light loads on growth.