Natural regeneration in mediterranean mixed forests: effect of environmental conditions on the physiological optimum niche of the species = Regeneración natural en masas mixtas mediterráneas: efecto de las condiciones ambientales en el nicho óptimo fisiológico de las especies

Los montes Mediterráneos han experimentado múltiples cambios en las últimas décadas (tanto en clima como en usos), lo que ha conducido a variaciones en la distribución de especies. El aumento previsto de las temperaturas medias junto con la mayor variabilidad intra e inter anual en cuanto a la ocurrencia de eventos extremos o disturbios naturales (como periodos prolongados de sequía, olas de frío o calor, incendios forestales o vendavales) pueden dañar significativamente al regenerado, llevándolo hasta la muerte, y jugando un papel decisivo en la composición de especies y en la dinámica del monte. La amplitud ecológica de muchas especies forestales puede verse afectada, de forma que se esperan cambios en sus nichos actuales de regeneración. Sin embargo, la migración latitudinal de las especies en busca de mejores condiciones, podría ser una explicación demasiado simplista de un proceso mucho más complejo de interacción entre la temperatura y la precipitación, que afectaría a cada especie de un modo distinto. En este sentido tanto la capacidad de adaptación al estrés ambiental de una determinada especie, así como su habilidad para competir por los recursos limitados, podría significar variaciones dentro de una comunidad. Las características fisiológicas y morfológicas propias de cada especie se encuentran fuertemente relacionadas con el lugar donde cada una puede surgir, qué especies pueden convivir y como éstas responden a las condiciones ambientales. En este sentido, el conocimiento sobre las distintas respuestas ecofisiológicas observadas ante cambios ambientales puede ser fundamentales para la predicción de variaciones en la distribución de especies, composición de la comunidad y productividad del monte ante el cambio global. En esta tesis investigamos el grado de tolerancia y sensibilidad que cada una de las tres especies de estudio, coexistentes en el interior peninsular ibérico (Pinus pinea, Quercus ilex y Juniperus oxycedrus), muestra ante los factores abióticos de estrés típicos de la región Mediterránea. Nuestro trabajo se ha basado en la definición del nicho óptimo fisiológico para el regenerado de cada especie a través de la investigación en profundidad del efecto de la sequía, la temperatura y el ambiente lumínico. Para ello, hemos desarrollado un modelo de predicción de la tasa de asimilación de carbono que nos ha permitido identificar las condiciones óptimas ambientales donde el regenerado de cada especie podría establecerse con mayor facilidad. En apoyo a este trabajo y con la idea de estudiar el efecto de la sequía a nivel de toda la planta hemos desarrollado un experimento paralelo en invernadero. Aquí se han aplicado dos regímenes hídricos para estudiar las características fisiológicas y morfológicas de cada especie, sobre todo a nivel de raíz y crecimiento del tallo, y relacionarlas con las diferentes estrategias en el uso del agua de las especies. Por último, hemos estudiado los patrones de aclimatación y desaclimatación al frio de cada especie, identificando los periodos de sensibilidad a heladas, así como cuellos de botella donde la competencia entre especies podría surgir. A pesar de que el pino piñonero ha sido la especie objeto de la gestión de estas masas durante siglos, actualmente se encuentra en la posición más desfavorable para combatir el cambio global, presentado el nicho fisiológico más estrecho de las tres especies. La encina sin embargo, ha resultado ser la especie mejor cualificada para afrontar este cambio, seguida muy de cerca por el enebro. Nuestros resultados sugieren una posible expansión en el rango de distribución de la encina, un aumento en la presencia del enebro y una disminución progresiva del pino piñonero a medio plazo en estas masas. ABSTRACT Mediterranean forests have undergone multiple changes over the last decades (in both climate and land use), which have lead to variations in the distribution of species. The expected increase in mean annual temperature together with the greater inter and intra-annual variability in extreme events and disturbances occurrence (such as prolonged drought periods, cold or heat waves, wildfires or strong winds) can significantly damage natural regeneration, up to causing death, playing a decisive role on species composition and forest dynamics. The ecological amplitude for adaptation of many species can be affected in such a way that changes in the current regeneration niches of many species are expected. However, the forecasted poleward migration of species seeking better conditions could be an oversimplification of what is a more complex phenomenon of interactions among temperature and precipitation, that would affect different species in different ways. In this regard, either the ability to adapt to environmental stresses or to compete for limited resources of a single species in a mixed forest could lead to variations within a community. The ecophysiological and morphological traits specific to each species are strongly related to the place where each species can emerge, which species can coexist, and how they respond to environmental conditions. In this regard, the understanding of the ecophysiological responses observed against changes in environmental conditions can be essential for predicting variations in species distribution, community composition, and forest productivity in the context of global change. In this thesis we investigated the degree of tolerance and sensitivity that each of the three studied species, co-occurring in central of the Iberian Peninsula (Pinus pinea, Quercus ilex and Juniperus oxycedrus), show against the typical abiotic stress factors in the Mediterranean region. Our work is based on the optimal physiological niche for regeneration of each species through in-depth research on the effect of drought, temperature and light environment. For this purpose, we developed a model to predict the carbon assimilation rate which allows us to identify the optimal environmental conditions where regeneration from each species could establish itself more easily. To obtain a better understanding about the effect of low temperature on regeneration, we studied the acclimation and deacclimation patterns to cold of each species, identifying period of frost sensitivity, as well as bottlenecks where competition between species can arise. Finally, to support our results about the effect of water availabilty, we conducted a greenhouse experiment with a view of studying the drought effect at the whole plant level. Here, two watering regimes were applied in order to study the physiological and morphological traits of each species, mainly at the level of the root system and stem growth, and so relate them to the different water use strategies of the species. Despite the fact that stone pine has been the target species for centuries, nowadays this species is in the most unfavorable position to cope with climate change. Holm oak, however, resulted the species that is best adapted to tolerate the predicted changes, followed closely by prickly juniper. Our results suggest a feasible expansion of the distribution range in holm oak, an increase in the prickly juniper presence and a progressive decreasing of stone pine presence in the medium term in these stone pine-holm oak-prickly juniper mixed forests.

Using ecological niche models to support tree species selection for forest restoration planning in largely deforested regions

Species selection for forest restoration is often supported by expert knowledge on local distribution patterns of native tree species. This approach is not applicable to largely deforested regions unless enough data on pre-human tree species distribution is available. In such regions, ecological niche models may provide essential information to support species selection in the framework of forest restoration planning. In this study we used ecological niche models to predict habitat suitability for native tree species in "Tierra de Campos" region, an almost totally deforested area of the Duero Basin (Spain). Previously available models provide habitat suitability predictions for dominant native tree species, but including non-dominant tree species in the forest restoration planning may be desirable to promote biodiversity, specially in largely deforested areas were near seed sources are not expected. We used the Forest Map of Spain as species occurrence data source to maximize the number of modeled tree species. Penalized logistic regression was used to train models using climate and lithological predictors. Using model predictions a set of tools were developed to support species selection in forest restoration planning. Model predictions were used to build ordered lists of suitable species for each cell of the study area. The suitable species lists were summarized drawing maps that showed the two most suitable species for each cell. Additionally, potential distribution maps of the suitable species for the study area were drawn. For a scenario with two dominant species, the models predicted a mixed forest (Quercus ilex and a coniferous tree species) for almost one half of the study area. According to the models, 22 non-dominant native tree species are suitable for the study area, with up to six suitable species per cell. The model predictions pointed to Crataegus monogyna, Juniperus communis, J.oxycedrus and J.phoenicea as the most suitable non-dominant native tree species in the study area. Our results encourage further use of ecological niche models for forest restoration planning in largely deforested regions.

Promoting mixed stands through conversion treatments. Effect of holm oak coppices thinning on black pine regeneration

The effects of conversion treatments, depending on ecological factors and silvicultural parameters (thinning intensity, thinning type and rotation, among others) have been studied during the last fifteen years in an experimental trial in Central Spain. The general climate is continental Mediterranean; soils are low depth and limy; vegetation is an homogeneous dense coppices of Quercus ilex with isolated Pinus nigra trees. The experimental design (three locations) includes different thinning intensities (from 0 to 100% of extracted basal area). Inventories have been carried out in 1994 and 2010; thinning treatments were done in 1995 and 2011. Analysis of the effects of the conversion treatment show the increment of diameter and height growth rates, the canopy recovery and the stand resprouting, finding differences in these effects between thinning treatments. Besides the induced changes at holm oak stand, the application of conversion treatment clearly changed the woodland dynamics. Fifteen years after the thinnings, floristic composition varied and an abundant pine regeneration was installed in the woodland. In this work we describe the changes between inventories in tree species composition and diameter distribution, specially in the case of black pine. The conversion treatment caused changes in forest dynamics in the short term, increasing biodiversity and diversifying the forest structure. The fast installation of Pinus regeneration suggests the potential of the zone for the establishment of multipurpose mixed Quercus-Pinus stands in wide areas where Quercus species were favoured by human populations for firewood production. Conversion treatment of coppices, with the creation of mixed stands, constitutes a good management alternative for extensive areas and an interesting technique to adaptation to global change.

Leftovers in seed dispersal: ecological implications of partial seed consumption for oak regeneration

1. Successful seed dispersal by animals is assumed to occur when undamaged seeds arrive at a favourable microsite. Most seed removal and dispersal studies consider only two possible seed fates, predation or escape intact. Whether partial consumption of seeds has ecological implications for natural regeneration is unclear. We studied partial consumption of seeds in a rodent-dispersed oak species. 2. Fifteen percent of dispersed acorns were found partially eaten in a field experiment. Most damage affected only the basal portion of the seeds, resulting in no embryo damage. Partially eaten acorns had no differences in dispersal distance compared to intact acorns but were recovered at farther distances than completely consumed acorns. 3. Partially eaten acorns were found under shrub cover unlike intact acorns that were mostly dispersed to open microhabitats. 4. Partially eaten acorns were not found buried proportionally more often than intact acorns, leading to desiccation and exposure to biotic agents (predators, bacteria and fungi). However, partial consumption caused more rapid germination, which enables the acorns to tolerate the negative effects of exposure. 5. Re-caching and shrub cover as microhabitat of destination promote partial seed consumption. Larger acorns escaped predation more often and had higher uneaten cotyledon mass. Satiation at seed level is the most plausible explanation for partial consumption. 6. Partial consumption caused no differences in root biomass when acorns experienced only small cotyledon loss. However, root biomass was lower when acorns experienced heavy loss of tissue but, surprisingly, they produced longer roots, which allow the seeds to gain access sooner to deeper resources. 7.Synthesis. Partial consumption of acorns is an important event in the oak regeneration process, both quantitatively and qualitatively. Most acorns were damaged non-lethally, without decreasing both dispersal distances and the probability of successful establishment. Faster germination and production of longer roots allow partially eaten seeds to tolerate better the exposure disadvantages caused by the removal of the pericarp and the non-buried deposition. Consequently, partially consumed seeds can contribute significantly to natural regeneration and must be considered in future seed dispersal studies.

Integrated planning for ecological urban regeneration

Considering that the vast majority of housing stock existing in 2011 will be used to satisfy residential needs in the year 2020 and beyond, ecological urban regeneration appears clearly as the key issue in relation to global urban sustainability for the most part of this century. Thus, if the 1992 Rio Summit identified the urban environment as the main arena where the global environmental crisis should be fought, 20 years later we must emphasize that it is mainly to the real cities and territories around us now where we should address our attention

Somatic embryogenesis as a regeneration method for clonal propagation of Mediterranean forest species

La mejora y conservación de recursos genéticos en especies forestales lleva siglos de retraso con respecto a las especies agrícolas. Los recursos forestales se han considerado tradicionalmente como recursos �mineros�, en los que primaba la mera extracción dejando exclusivamente a la regeneración natural la labor de sostenibilidad en los montes y dehesas o montados. Hoy en día, el necesario desarrollo del medio rural obliga a la explotación racional de los recursos como medio de garantizar su sostenibilidad. Por ello se está empezando a extender el criterio de que las especies forestales se pueden y deben �cultivar� en determinados espacios. Las características biológicas de las especies forestales las hacen, a menudo, recalcitrantes a las técnicas de mejora y conservación de recursos genéticos tradicionalmente aplicadas a especies agrícolas. En particular, la propagación vegetativa se ha utilizado ampliamente en muchos cultivos leñosos como una herramienta muy poderosa para capturar todo el potencial genético de combinaciones genéticas valiosas. En especies forestales, en particular en las mediterráneas, esta posibilidad raramente se ha podido aplicar debido a la baja capacidad morfogénica de estas especies y la fuerte influencia de la maduración o cambio de fase. En los últimos años la biotecnología forestal ha tenido un desarrollo espectacular. En particular las técnicas de regeneración clonal de plantas basadas en técnicas de cultivo in vitro, fundamentalmente vía embriogénesis somática, se están ya aplicando por muchas empresas privadas e instituciones públicas a nivel semi-operativo con diversas especies, para la conservación de material selecto y el establecimiento de ensayos clonales. Nuestros grupos de trabajo están desarrollando protocolos de regeneración por embriogénesis somática en distintas especies forestales. En esta comunicación se presenta el estado actual de los conocimientos en dos especies típicamente mediterráneas, el alcornoque (Quercus suber L.) y el pino piñonero (Pinus pinea L.), destacando los principales cuellos de botella para su aplicación a gran escala.

Plant regeneration from an endangered valuable cork oak tree by somatic embryogenesis.

Among the several applications of in vitro tissue culture techniques, the conservation of plant germplasm is one of the most widely used. The cork oak is one of the principal tree species in the Western Mediterranean región. Within this área, the Balearic Islands are considered to be a glacial refuge, and therefore a reservoir of genetic resources. A singular tree has been found in the small Minorca Island population. The haplotype of this tree is of Tyrrhenian origin, showing a past link between Minorca and Sardinia. Moreover, this tree do not bear a deletion within an ITS from ribosimic nuclear DNA, which is fairly common in many populations of this species, and indicates that ir may be the descendant of a very ancient population. This tree is currently in a precarious condition, and it has not produced acorns in the last years. Hence there is a clear need of vegetative propagation to conserve this genotype. We have previously developed methods to clone adult cork oak tres by somatic embryogenesis, and therefore the aim of the present work was to clone this singular tree. There braches from the corwn were collected in November 2004, and methods previously described were carried out. By February 2005 somatic embryogenesis was obtained from leaves of the tree with percentages on induction ranging from 17 to 54% depending on the branch, which may show a novel source of variation that requires further study. Spontaneously matured somatic embryos germinated at 46% in average, and the first somatic seedlings from the Alfavaret's cork oak tree were obtained. Therefore, this study shows one of the most relevant applications of somatic embryogenesis: the plant regeneration of valuable genotypes for the in situ and ex situ conservation of forest genetic resources.

An integral model for natural regeneration of Pinus pinea L. in the Northern Plateau (Spain) = Modelo integral de regeneración natural para Pinus pinea L. en la Meseta Norte (España)

Natural regeneration is an ecological key-process that makes plant persistence possible and, consequently, it constitutes an essential element of sustainable forest management. In this respect, natural regeneration in even-aged stands of Pinus pinea L. located in the Spanish Northern Plateau has not always been successfully achieved despite over a century of pine nut-based management. As a result, natural regeneration has recently become a major concern for forest managers when we are living a moment of rationalization of investment in silviculture. The present dissertation is addressed to provide answers to forest managers on this topic through the development of an integral regeneration multistage model for P. pinea stands in the region. From this model, recommendations for natural regeneration-based silviculture can be derived under present and future climate scenarios. Also, the model structure makes it possible to detect the likely bottlenecks affecting the process. The integral model consists of five submodels corresponding to each of the subprocesses linking the stages involved in natural regeneration (seed production, seed dispersal, seed germination, seed predation and seedling survival). The outputs of the submodels represent the transitional probabilities between these stages as a function of climatic and stand variables, which in turn are representative of the ecological factors driving regeneration. At subprocess level, the findings of this dissertation should be interpreted as follows. The scheduling of the shelterwood system currently conducted over low density stands leads to situations of dispersal limitation since the initial stages of the regeneration period. Concerning predation, predator activity appears to be only limited by the occurrence of severe summer droughts and masting events, the summer resulting in a favourable period for seed survival. Out of this time interval, predators were found to almost totally deplete seed crops. Given that P. pinea dissemination occurs in summer (i.e. the safe period against predation), the likelihood of a seed to not be destroyed is conditional to germination occurrence prior to the intensification of predator activity. However, the optimal conditions for germination seldom take place, restraining emergence to few days during the fall. Thus, the window to reach the seedling stage is narrow. In addition, the seedling survival submodel predicts extremely high seedling mortality rates and therefore only some individuals from large cohorts will be able to persist. These facts, along with the strong climate-mediated masting habit exhibited by P. pinea, reveal that viii the overall probability of establishment is low. Given this background, current management –low final stand densities resulting from intense thinning and strict felling schedules– conditions the occurrence of enough favourable events to achieve natural regeneration during the current rotation time. Stochastic simulation and optimisation computed through the integral model confirm this circumstance, suggesting that more flexible and progressive regeneration fellings should be conducted. From an ecological standpoint, these results inform a reproductive strategy leading to uneven-aged stand structures, in full accordance with the medium shade-tolerant behaviour of the species. As a final remark, stochastic simulations performed under a climate-change scenario show that regeneration in the species will not be strongly hampered in the future. This resilient behaviour highlights the fundamental ecological role played by P. pinea in demanding areas where other tree species fail to persist.

Connexin-43 in the osteogenic BM niche regulates its cellular composition and the bidirectional traffic of hematopoietic stem cells and progenitors

Connexin-43 (Cx43), a gap junction protein involved in control of cell proliferation, differentiation and migration, has been suggested to have a role in hematopoiesis. Cx43 is highly expressed in osteoblasts and osteogenic progenitors (OB/P). To elucidate the biologic function of Cx43 in the hematopoietic microenvironment (HM) and its influence in hematopoietic stem cell (HSC) activity, we studied the hematopoietic function in an in vivo model of constitutive deficiency of Cx43 in OB/P. The deficiency of Cx43 in OB/P cells does not impair the steady state hematopoiesis, but disrupts the directional trafficking of HSC/progenitors (Ps) between the bone marrow (BM) and peripheral blood (PB). OB/P Cx43 is a crucial positive regulator of transstromal migration and homing of both HSCs and progenitors in an irradiated microenvironment. However, OB/P Cx43 deficiency in nonmyeloablated animals does not result in a homing defect but induces increased endosteal lodging and decreased mobilization of HSC/Ps associated with proliferation and expansion of Cxcl12-secreting mesenchymal/osteolineage cells in the BM HM in vivo. Cx43 controls the cellular content of the BM osteogenic microenvironment and is required for homing of HSC/Ps in myeloablated animals

Modelling Pinus pinea forest management to attain natural regeneration under present and future climatic scenarios

Natural regeneration-based silviculture has been increasingly regarded as a reliable option in sustainable forest management. However, successful natural regeneration is not always easy to achieve. Recently, new concerns have arisen because of changing future climate. To date, regeneration models have proved helpful in decision-making concerning natural regeneration. The implementation of such models into optimization routines is a promising approach in providing forest managers with accurate tools for forest planning. In the present study, we present a stochastic multistage regeneration model for Pinus pinea L. managed woodlands in Central Spain, where regeneration has been historically unsuccessful. The model is able to quantify recruitment under different silviculture alternatives and varying climatic scenarios, with further application to optimize management scheduling. The regeneration process in the species showed high between-year variation, with all subprocesses (seed production, dispersal, germination, predation, and seedling survival) having the potential to become bottlenecks. However, model simulations demonstrate that current intensive management is responsible for regeneration failure in the long term. Specifically, stand densities at rotation age are too low to guarantee adequate dispersal, the optimal density of seed-producing trees being around 150 stems·ha−1. In addition, rotation length needs to be extended up to 120 years to benefit from the higher seed production of older trees. Stochastic optimization confirms these results. Regeneration does not appear to worsen under climate change conditions; the species exhibiting resilience worthy of broader consideration in Mediterranean silviculture.

Optical regeneration based on noise generated in bistable devices: going from 2R to 3R

In this paper we propose to employ an instability that occurs in bistable devices as a control signal at the reception stage to generate the clock signal. One of the adopted configurations is composed of two semiconductor optical amplifiers arranged in a cascaded structure. This configuration has an output equivalent to that obtained from Self-Electrooptic Effect Devices (SEEDs), and it can implement the main Boolean functions of two binary inputs. These outputs, obtained from the addition of two binary signals, show a short spike in the transition from "1" to "2" in the internal processing. A similar result is obtained for a simple semiconductor amplifier with bistable behavior. The paper will show how these structures may help recover clock signals in any optical transmission system

On the improvement of urban regeneration processes from more than thirty years of rehabilitation experiences

At this moment of extended economic, social and environmental crisis within which new interventions on the consolidated city are being set out, it is essential to count on the acquired experience in urban rehabilitation processes that were carried out in Spain during the last thirty years. Despite the complexity of this kind of processes and the diversity of the situations and actions that happened, this paper addresses the analysis of common patterns in twenty urban rehabilitation experiences. Different stages of the processes were studied, from the management to the regenerated areas in order to ease the design of new intervention initiatives.

The role of the urban support in the regeneration of vulnerable neighbourhoods

The processes of social and urban segregation have got worse during the last decades. Several studies have deepened into the analysis of the causes and consequences of these processes and have tried to define solutions that beyond eradicating some specific problems, were aimed at the consolidation of sustainable urban environments. This paper presents an approach to the problem of urban inequality based on the concept of urban vulnerability as something that goes beyond the social and economic problems. In exclusion processes it is very important to consider the urban context and the physical and structural conditions not only in each neighborhood but also in the city as a whole. The paper seeks to pose a reflection on the urban support, which is understood in all its complexity and thought to be a key to ensure access and the right to the city of the citizens most in need.

Post-embryonic organogenesis and plant regeneration from tissues: two sides of the same coin?

Plants have extraordinary developmental plasticity as they continuously form organs during post-embryonic development. In addition they may regenerate organs upon in vitro hormonal induction. Advances in the field of plant regeneration show that the first steps of de novo organogenesis through in vitro culture in hormone containing media (via formation of a proliferating mass of cells or callus) require root post-embryonic developmental programs as well as regulators of auxin and cytokinin signaling pathways. We review how hormonal regulation is delivered during lateral root initiation and callus formation. Implications in reprograming, cell fate and pluripotency acquisition are discussed. Finally, we analyze the function of cell cycle regulators and connections with epigenetic regulation. Future work dissecting plant organogenesis driven by both endogenous and exogenous cues (upon hormonal induction) may reveal new paradigms of common regulation.

Brown trout thermal niche and climate change: expected changes in the distribution of cold-water fish in central Spain

This paper addresses the determination of the realized thermal niche and the effects of climate change on the range distribution of two brown trout populations inhabiting two streams in the Duero River basin (Iberian Peninsula) at the edge of the natural distribution area of this species. For reaching these goals, new methodological developments were applied to improve reliability of forecasts. Water temperature data were collected using 11 thermographs located along the altitudinal gradient, and they were used to model the relationship between stream temperature and air temperature along the river continuum. Trout abundance was studied using electrofishing at 37 sites to determine the current distribution. The RCP4.5 and RCP8.5 change scenarios adopted by the International Panel of Climate Change for its Fifth Assessment Report were used for simulations and local downscaling in this study. We found more reliable results using the daily mean stream temperature than maximum daily temperature and their respective seven days moving-average to determine the distribution thresholds. Thereby, the observed limits of the summer distribution of brown trout were linked to thresholds between 18.1ºC and 18.7ºC. These temperatures characterise a realised thermal niche narrower than the physiological thermal range. In the most unfavourable climate change scenario, the thermal habitat loss of brown trout increased to 38% (Cega stream) and 11% (Pirón stream) in the upstream direction at the end of the century; however, at the Cega stream, the range reduction could reach 56% due to the effect of a ?warm-window? opening in the piedmont reach.