With climate change being a certainty, which today is probably the biggest challenge humanity is facing, and also accepting that greenhouse gas emissions are the main cause accelerating climate change, there is an urgent need to find solutions that lead to the mitigation of the already intense, and in some cases, even violent, effects. Forests can most easily work as carbon sinks. However, it is convenient to analyze the residence time of this carbon in forests, as this residence time will depend on the type of forest management used. This paper aims to analyze forest management models from a perspective of carbon residence time in forests, dividing the models into three types: carbon conservation, carbon storage, and carbon substitution. Carbon conservation models are those models in which the amounts of carbon stored only replace the carbon released, mainly by the industrial use of raw materials. Carbon storage models are models that foster the growth of forest areas to ensure that the amount of carbon stored grows, and where the ratio clearly leans towards sequestration and storage. Carbon substitution models are models that move towards the substitution of fossil carbon by renewable carbon, thus contributing to the creation of a neutral flow.

A.

We present a revision of Glebionis coronaria in the Mediterranean area based on: a) micro-morphology of the disc floret cypselas observed with a high-resolution confocal microscopy; b) measurements of the disc cypsela with a stereoscopic microscope – duly scaled; c) its distribution in several bioclimatic belts; d) field observations; e) comparisons of herbarium samples. Because of this study, we propose the elevation of Glebionis coronaria var. discolor to the rank of species, as Glebionis discolor comb. & stat. nov., based on morphological and ecological characteristics such as the disposition of the intercostal glands, the size of the disc cypsela wings and its distribution according to the bioclimatic belts. Glebionis coronaria, with totally yellow ray florets and intercostal glands aligned, is exclusive to the thermo-Mediterranean bioclimatic belt, while Glebionis discolor, with white ray florets on a yellow base and intercostal glands arranged randomly, is found in the thermo- and meso-Mediterranean belt.Illustrations of micromorphological characteristics of the cypselas, an identification key, a taxonomic synopsis including information on nomenclatural types, synonyms, descriptions of the taxa, and, as supplementary information, a list of the specimens examined and bioclimatic classification of samples localities are also presented.

The fractal dimension (FD) is calculated for seven species of the genus Quercus L. in Calabria region (southern Italy), five of which have a marcescent-deciduous and two a sclerophyllous character. The fractal analysis applied to the leaves reveals different FD values for the two groups. The difference between the means and medians is very small in the case of the marcescent-deciduous group and very large when these differences are established between both groups: all this highlights the distance between the two groups in terms of similarity. Specifically, Q.crenata, which is hybridogenic in origin and whose parental species are Q.cerris and Q.suber, is more closely related to Q.cerris than to Q.suber, as also expressed in the molecular analysis. We consider that, in combination with other morphological, physiological and genetic parameters, the fractal dimension is a useful tool for studying similarities amongst species.

The plant variability in the southern Iberian Peninsula consists of around 3500 different taxa due to its high bioclimatic, geographic, and geological diversity. The deciduous forests in the southern Iberian Peninsula are located in regions with topographies and specific bioclimatic conditions that allow for the survival of taxa that are typical of cooler and wetter bioclimatic regions and therefore represent the relict evidence of colder and more humid paleoclimatic conditions. The floristic composition of 421 samples of deciduous forests in the south-central part of the Iberian Peninsula were analyzed. The ecological importance index (IVI) was calculated, where the most important tree species were Quercus pyrenaica, Acer opalus subsp. Granatensis, and Corylus avellana. These species are uncommon in the south-central part of the Iberian Peninsula, forming forests of little extension. An analysis of the vertical distribution of the species (stratum) shows that the majority of the species of stratum 3 (hemicriptophics, camephytes, geophites, and nanophanerophytes) are characteristic of deciduous forests, and their presence is positively correlated with high values of bioclimatic variables related to humidity and presence of water in the soil (nemoral environments), while they are negatively correlated with high values ​​of bioclimatic variables related to high temperatures, evapotranspiration, and aridity. This work demonstrates that several characteristic deciduous forest taxa are more vulnerable to disappearance due to the loss of their nemoral conditions caused by gaps in the tree or shrub canopy. These gaps lead to an increase in evapotranspiration, excess insolation, and a consequent loss of water and humidity in the microclimatic conditions.