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Francisco Esteban Bara and Maria Rosa Buxarrais Estrada

Luis García Esteban, Paloma de Palacios, Francisco García Fernández and Ruth Moreno

The literature on the wood anatomy of the genus Abies is reviewed and discussed, and complemented with a detailed study of 33 species, 1 subspecies and 4 varieties. In general, the species studied do not show diagnostic interspecific differences, although it is possible to establish differences between groups of species using certain quantitative and qualitative features.

The marginal axial parenchyma consisting of single cells and the ray parenchyma cells with distinctly pitted horizontal walls, nodular end walls and presence of indentures are constant for the genus, although these features also occur in the other genera of the Abietoideae. The absence of ray tracheids in Abies can be used to distinguish it from Cedrus and Tsuga, and the irregularly shaped parenchymatous marginal ray cells are only shared with Cedrus. The absence of resin canals enables Abies to be distinguished from very closely related genera such as Keteleeria and Nothotsuga. The crystals in the ray cells, taxodioid cross-field pitting and the warty layer in the tracheids can be regarded as diagnostic generic features.

Elena Román-Jordán, Luis G. Esteban, Paloma de Palacios and Francisco G. Fernández

The wood anatomy of 14 species of Cupressus was studied to determine whether there is a pattern of wood anatomical diversity between the species from the North and Central American (western) region and the Eurasian (eastern) region. Xanthocyparis vietnamensis and Chamaecyparis nootkatensis (syn. Xanthocyparis nootkatensis) were also studied to compare their wood anatomy, given their recent inclusion by some authors in Cupressus. The arrangement of the axial parenchyma, morphology of the transverse end walls of the axial parenchyma, presence of ray tracheids, typology of the end walls of the ray parenchyma cells and ray height support to some extent the division of Cupressus into two large groups: the American group (western region) and the Eurasian group (eastern region), as proposed in molecular phylogenetic studies. The wood anatomy of Chamaecyparis nootkatensis shares the presence of ray tracheids and the same ray typology with American Cupressus, and has the same ray height as Eurasian Cupressus. In contrast, Xanthocyparis vietnamensis shares the absence of ray tracheids and the same ray typology with Eurasian Cupressus, and has the same ray height as American Cupressus.

Luis García Esteban, Paloma de Palacios, Antonio Guindeo and Francisco García Fernández

This study describes the structure of the wood of Abies pinsapo from samples taken from its three natural distribution areas in the Iberian Peninsula (Sierra de Grazalema, Sierra de las Nieves and Sierra Bermeja) and compares them with the varieties from the north of Africa, Abies pinsapo var. marocana from the Talassemtane mountains and A. pinsapo var. tazaotana from the Tazaout mountains. All the samples were collected in their regions of provenance. To put the results into perspective, a comparison was also made with the wood of Abies alba and A. numidica. The wood of the Iberian A. pinsapo and of its two varieties from the Rif mountains in Morocco is anatomically similar, and there are no qualitative differences that enable the wood to be differentiated except for the presence of resin deposits in the tracheids adjacent to the rays in the samples from Grazalema. Quantitatively, for tracheid diameter and tracheid length there are statistically significantly differences (p<0.05) between those of Spanish provenance and the Moroccan varieties, but for tracheid pit diameter, largest diameter of cross-field pits and tall ray frequency the samples from Sierra Bermeja have more in common with the African samples.

Luis García Esteban, Francisco García Fernández, Paloma de Palacios de Palacios, Ruth Moreno Romero and Nieves Navarro Cano

Neural networks are complex mathematical structures inspired on biological neural networks, capable of learning from examples (training group) and extrapolating knowledge to an unknown sample (testing group). The similarity of wood structure in many species, particularly in the case of conifers, means that they cannot be differentiated using traditional methods. The use of neural networks can be an effective tool for identifying similar species with a high percentage of accuracy. This predictive method was used to differentiate Juniperus cedrus and J. phoenicea var. canariensis, both from the Canary Islands. The anatomical features of their wood are so similar that it is not possible to differentiate them using traditional methods. An artificial neural network was used to determine if this method could differentiate the two species with a high degree of probability through the biometry of their anatomy. To achieve the differentiation, a feedforward multilayer percepton network was designed, which attained 98.6% success in the training group and 92.0% success in the testing or unknown group. The proposed neural network is satisfactory for the desired purpose and enables J. cedrus and J. phoenicea var. canariensis to be differentiated with a 92% probability.

Paloma de Palacios, Luis G. Esteban, Francisco G. Fernández, Alberto García-Iruela, María Conde and Elena Román-Jordán

The wood anatomy of the three species of Juniperus occurring in Macaronesia is compared for the first time using representative samples of each species collected in its natural region of provenance: J. cedrus Webb & Berthel and J. phoenicea L. var. canariensis Guyot, in the Canary Islands, and J. brevifolia (Seub.) Antoine, in the Azores. The three species are anatomically similar, although some qualitative differences were observed: distribution of axial parenchyma very scarce in J. phoenicea compared with the other two species, presence of crassulae only in J. phoenicea, presence of torus extensions and notches on pit borders in the radial walls of J. brevifolia, and ray parenchyma end walls slightly nodular in J. cedrus as opposed to very nodular in J. phoenicea and J. brevifolia. In addition, the biometry of tracheid pit diameter in the radial walls, ray height in number of cells, and largest and smallest diameters of cross-field pits shows differences for a significance level of 95%.

Luis G. Esteban, Paloma de Palacios, Alberto García-Iruela, Elena Román-Jordán, Francisco G. Fernández, Sandra Díaz Fernández and María Conde

For the first time, the wood anatomy of Tetraclinis articulata (Vahl) Masters has been studied using representative samples from its natural distribution area in Spain, in Sierra de Cartagena (Region of Murcia). Mature wood was collected from five individuals representative of the forest stand and their anatomy was compared with other genera of the Cupressaceae. Axial tracheids without helical thickenings, low homogeneous rays, cupressoid pits and the absence of normal axial resin canals are characteristic features of this monotypic genus, as they are of most other Cupressaceae genera. An obvious warty layer separates this wood from the genera sharing its territory (Cupressus and Juniperus) and its semi-spherical, slightly anastomosed warts distinguish it from other, geographically distant genera (Actinostrobus and Callitris). The presence of traumatic axial resin canals is reported for the first time and supports the occurrence of this feature outside the Pinaceae. The wood anatomical diversity within the clade comprising Tetraclinis, Microbiota and Platycladus, as reconstructed by molecular analysis, is discussed.