The ultimate source of water for plants is precipitation; rain falling upon soil penetrates it at a rate depending upon the physical properties of that particular soil; snow and hail do the same after melting. If the rate of rainfall or the rate of production of water by melting exceeds the infiltration rate, then surface runoff occurs and the excess water drains into streams and eventually reaches the sea. That water which penetrates the soil replenishes the soil reservoir and when this is filled to capacity (see chapter 3) the surplus drains through into the aquifers. These are strata such as sand or chalk which can hold substantial quantities of recoverable water. Water held in the soil reservoir is drawn into plant roots and up their stems to be evaporated from the leaves back into the atmosphere, where it rejoins water evaporated from the sea, lakes and rivers and from the surface of wet soil. This so-called hydrological cycle (figure 1.2) depends for its continuance upon energy derived from the sun’s radiation and as will be shown in later chapters its rate is governed largely by meteorological factors.

The Water Balance

Ecological Niche Models (ENMs) are increasingly used by ecologists to project species potential future distribution. However, the application of such models may be challenging, and some caveats have already been identified. While studies have generally shown that projections may be sensitive to the ENM applied or the emission scenario, to name just a few, the sensitivity of ENM-based scenarios to General Circulation Models (GCMs) has been often underappreciated. Here, using a multi-GCM and multi-emission scenario approach, we evaluated the variability in projected distributions under future climate conditions. We modeled the ecological realized niche (sensu Hutchinson) and predicted the baseline distribution of species with contrasting spatial patterns and representative of two major functional groups of European trees: the dwarf birch and the sweet chestnut. Their future distributions were then projected onto future climatic conditions derived from seven GCMs and four emissions scenarios using the new Representative Concentration Pathways (RCPs) developed for the Intergovernmental Panel on Climate Change (IPCC) AR5 report. Uncertainties arising from GCMs and those resulting from emissions scenarios were quantified and compared. Our study reveals that scenarios of future species distribution exhibit broad differences, depending not only on emissions scenarios but also on GCMs. We found that the between-GCM variability was greater than the between-RCP variability for the next decades and both types of variability reached a similar level at the end of this century. Our result highlights that a combined multi-GCM and multi-RCP approach is needed to better consider potential trajectories and uncertainties in future species distributions. In all cases, between-GCM variability increases with the level of warming, and if nothing is done to alleviate global warming, future species spatial distribution may become more and more difficult to anticipate. When future species spatial distributions are examined, we propose to use a large number of GCMs and RCPs to better anticipate potential trajectories and quantify uncertainties.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/ece3.1411

Uncertainties in the projection of species distributions related to general circulation models.

Aim Mediterranean terrestrial ecosystems serve as reference laboratories for the investigation of global change because of their transitional climate, the high spatiotemporal variability of their environmental conditions, a rich and unique biodiversity and a wide range of socio-economic conditions. As scientific development and environmental pressures increase, it is increasingly necessary to evaluate recent progress and to challenge research priorities in the face of global change. Location Mediterranean terrestrial ecosystems. Methods This article revisits the research priorities proposed in a 1998 assessment. Results A new set of research priorities is proposed: (1) to establish the role of the landscape mosaic on fire-spread; (2) to further research the combined effect of different drivers on pest expansion; (3) to address the interaction between drivers of global change and recent forest management practices; (4) to obtain more realistic information on the impacts of global change and ecosystem services; (5) to assess forest mortality events associated with climatic extremes; (6) to focus global change research on identifying and managing vulnerable areas; (7) to use the functional traits concept to study resilience after disturbance; (8) to study the relationship between genotypic and phenotypic diversity as a source of forest resilience; (9) to understand the balance between C storage and water resources; (10) to analyse the interplay between landscape-scale processes and biodiversity conservation; (11) to refine models by including interactions between drivers and socio-economic contexts; (12) to understand forest–atmosphere feedbacks; (13) to represent key mechanisms linking plant hydraulics with landscape hydrology. Main conclusions (1) The interactive nature of different global change drivers remains poorly understood. (2) There is a critical need for the rapid development of regional- and global-scale models that are more tightly connected with largescale experiments, data networks and management practice. (3) More attention should be directed to drought-related forest decline and the current relevance of historical land use.

/pdf/reassessing-global-change-research-priorities-in-5fhi5uyals.pdf

Reassessing global change research priorities in mediterranean terrestrial ecosystems: how far have we come and where do we go from here?

Geostatistical modelling of air temperature in a mountainous region of Northern Spain

Reassessing global change research priorities in the Mediterranean Basin: how far have we come and where do we go from here?

A stratified sampling on 22 plots has been carried out on chestnut (Castanea sativa Miller) stands in Galicia (Spain). Central and marginal parameters ranges have been stablished for defining physiographic, climatic and soil habitat diagrams of chetnut stands. Most stands are located between 400 and 750 m elevation, with around 1,300 mm annual rainfall. According to FAO criteria, soil are classified as distric Cambisols and distric Luvisols. Several silvicultural parameters have also been calculated. After their correlation with the ecological ones, it is concluded that the best Galician chestnut forest sites are located on northern aspects, with low summer drought and around 13 C/N ratio in soils. Finally, a comparative analysis between chestnut habitat and habitat of three other tree species of the region shows that chesnut has less ecological aptitude than pedunculate oak, Maritime pine and Monterrey pine.

Autoecología de los castañares de Galicia (España)

En el presente trabajo se han establecido los valores de los habitats centrales y marginales de la fisiografia, edafologia y climatologia de las masas de Castanea sativa Miller en las comunidades autonomas de Castilla y Leon, Castilla-La Mancha y Madrid. Se ha podido comprobar al respecto que los castanares se suelen encontrar entre los 620 y los 1.100 m de altitud, presentan una amplia variacion en su regimen pluviometrico, no asi en el termometrico. Los suelos de los castanares estudiados son fundamentalmente Cambisoles, Luvisoles y Umbrisoles, generalmente fuertemente acidos, francos o franco-arenosos y con baja relacion C/N. Tambien se establecen los criterios para interpretar los rangos de las habitats marginales respecto de los centrales a fin de poder realizar una valoracion del riesgo de efectuar la implantacion de esta especie en un terreno del ambito estudiado. El mayor riesgo se encontraria en terrenos cuyos parametros de precipitaciones otonales fueran inferiores a 220 mm, tierra fina inferior a 16,7 %, limo menor de 20,4 %, capacidad de retencion de agua inferior a 38 mm, materia organcia superficial menor del 2,1 %, oscilacion termica mayor de 18,5 C y permeabilidad superior a 4,75. El parametro selvicola que mejor describe las caracteristicas dasonomicas del conjunto de los castanares castellanos en relacion con los parametros evaluadores del biotopo es el indice de Hart por numero de cepas, el cual puede ser estimado con bastante aproximacion en funcion de la pendiente del terreno, la precipitacion de invierno, la suma de superavit y la permeabilidad del suelo.

Autoecología de los castañares de Castilla (España)

Este trabajo se ha realizado aplicando metodologias similares a las empleadas en los estudios autoecologicos parametricos realizados con anterioridad para Fagus sylvatica en otras regiones espanolas. Se ha estratificado el territorio ocupado por hayedos en Castilla y Leon (Espana) y se ha realizado un muestreo en un total de 37 parcelas representativas. A partir de los resultados de dicho muestreo, se han elaborado una serie de parametros fisiograficos, climaticos, edaficos y selvicolas. El analisis de los parametros elaborados ha permitido establecer los valores parametricos que definen los habitats centrales y marginales para el haya en Castilla y Leon. Un conjunto de analisis estadisticos multivariables han permitido elaborar modelos predictivos para variables selvicolas en relacion con las variables ambientales mas significativas. El conjunto de resultados obtenidos constituye una base importante para establecer la aptitud ecologica del territorio estudiado, con vistas a la implantacion de masas forestales estables de Fagus sylvatica.

Autoecología paramétrica de los hayedos de Castilla y León

Se han establecido los valores parametricos optimos y marginales que definen los habitats fisiografico, climatico y edafico de las masas de Castanea sativa Miller en Cataluna. Asi, se ha podido comprobar que la mayoria de los castanares catalanes se hallan sobre suelos formados a partir de rocas igneas, y en ellos predominan las texturas franco-arenosas. Los suelos, segun FAO, son mayoritariamente cambisoles. Aunque la capacidad de retencion de agua de estos suelos es escasa, la sequia fisiologica esta muy reducida. Los humus fundamentalmente pertenecen al tipo mull forestal, a pesar la elevada acidez. Ademas, se han elaborado una serie de parametros selvicolas que al correlacionarlos con los ecologicos nos ha permitido comprobar que los mejores castanares se encuentran entorno a los 750 m de altitud, con precipitaciones de primavera cercanas a 240 mm, temperaturas medias anuales sobre 11,5o C y temperaturas medias del mes mas calido proximas a 20o C.

Autoecologia de los castañares catalanes

Este estudio esta basado en el muestreo de campo y posterior analisis de 24 parcelas de hayedo seleccionadas mediante una estratificacion de su area de distribucion basada en la clasificacion CLATERES de la Ecorregion Catalano-Aragonesa. En cada parcela se han evaluado 3 parametros fisiograficos, 15 climaticos y 18 edaficos, a partir de los cuales se han establecido sus valores parametricos centrales y marginales que permiten definir los habitats fisiografico, climatico y edafico de las masas de Fagus sylvatica L. en Cataluna. Los hayedos catalanes se presentan sobre substratos litologicos muy diversos (plutonitas, vulcanitas, metamorfitas y sedimentitas, tanto acidas como basicas), con texturas predominantes francas, franco-arenosas o franco-limosas. Los suelos, segun FAO, son mayoritariamente cambisoles. A pesar de que la capacidad de retencion de agua de sus suelos es escasa, la sequia fisiologica es reducida. Los humus predominantemente pertenecen a los tipos mull forestal y mull calcico. Ademas, se presentan una serie de parametros selvicolas ( Densidad de pies y densidad de chirpiales, Area basimetrica, Altura Total dominante, Indices de Hart-Becking, Indice de Calidad de Estacion y Edad de la masa) que al correlacionarlos con los ecologicos nos ha permitido comprobar que los mejores hayedos se encuentran en las localizaciones mas termicas, en las que incluso se podria producir sequia fisiologica si no fuera por que existen suficientes precipitaciones estivales.

/pdf/autoecologia-de-los-hayedos-catalanes-fzs9cbofnv.pdf

Autoecología de los hayedos catalanes

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