Comparative Wood Anatomy of Juniperus from Macaronesia
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186 IAWAIAWA Journal Journal 35 (2), 35 2014: (2), 2014 186–198 COMPARATIVE WOOD ANATOMY OF JUNIPERUS FROM MAcARONESIA Paloma de Palacios1,*, Luis G. Esteban1, Francisco G. Fernández1, Alberto García-Iruela1, María Conde2 and Elena Román-Jordán1 1Universidad Politécnica de Madrid, Escuela Técnica Superior de Ingenieros de Montes, Departamento de Ingeniería Forestal, Ciudad Universitaria s/n, 28040 Madrid, Spain 2CIFOR-INIA, Departamento de Productos Forestales, Carretera de la Coruña Km 7.5, 28040 Madrid, Spain *Corresponding author; e-mail: [email protected] ABSTRACT 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. phoeni- cea 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%. Keywords: Azores, Canary Islands, Juniperus brevifolia, Juniperus cedrus, Juniperus phoenicea var. canariensis. INTRODUCTION The genus Juniperus includes 52 species, 10 subspecies and 43 varieties distributed in the northern hemisphere from the subarctic tundra to the semi-desert, except J. procera, which is found south of the equator, in the east and south of tropical Africa (Farjon 2005). Macaronesia is home to three species: two in the Canary Islands (J. cedrus Webb & Berthel and J. phoenicea L. var. canariensis Guyot) and one in the Azores (J. brevifolia (Seub.) Antoine). Juniperus phoenicea var. canariensis occurs naturally in the Canary Islands on Tenerife, La Palma, El Hierro, Gran Canaria and La Gomera, normally below an altitude of 1000 m (Bramwell 1990). Adams et al. (2010a) considered that this species should be called Juniperus phoenicea var. turbinata because of its similarities to the species found in Morocco, even though the terpenoids in the oils of the Canary Islands species © International Association of Wood Anatomists, 2014 DOI 10.1163/22941932-00000059 Published by Koninklijke Brill NV, Leiden Downloaded from Brill.com10/08/2021 12:50:50PM via free access de Palacios et al. – Juniperus from Macaronesia 187 Figure 1. – A: Juniperus brevifolia, Fayal (The Azores). – B: J. cedrus, La Palma (Canary Is- lands). – C: J. phoenicea var. canariensis, El Hierro (Canary Islands). do not correspond to either of the varieties specified for this species (var. turbinata and var. phoenicea). Juniperus brevifolia is endemic to the Azores, where it occurs on the islands of Corvo, Faial, Flores, Pico, Santa Maria, São Jorge, São Miguel and Terceira, normally at altitudes from 240 to 800 m, although some individuals are found from sea level to 1500 m. These two species are normally shrubs or small trees, usu- Downloaded from Brill.com10/08/2021 12:50:50PM via free access 188 IAWA Journal 35 (2), 2014 ally branched from the base, with a height of up to 8 m. Juniperus cedrus, however, is capable of reaching tree heights of 15 m. Its distribution range is the islands of Tenerife, La Palma and Gran Canaria, although it has also been cited from Madeira (Fig. 1). Cavaleiro et al. (2001) studied the essential oils of the J. cedrus population in Madeira and concluded that they differed from the oils studied in the same species in the Canary Islands. Adams et al. (2010b) also considered that this Juniperus should be regarded as separate from J. cedrus and be called Juniperus maderensis, based on the volatile leaf oil composition and the DNA sequence data. The aromatic and decay-resistant nature of the wood of these three species has led to a decline in their numbers over the centuries through overharvesting. The IUCN Red List of Threatened Species includes J. cedrus as “endangered” (Rumeu Ruiz et al. 2011) and J. brevifolia as “vulnerable” (Thomas 2011). Studies on the anatomy of these species are very scarce. Moreover, in some cases samples were taken from branches, and other studies do not specify the origin of the samples. Greguss (1972) described J. brevifolia, using a sample of a 9-year-old branch sent by H. Gaussen from the Forest Laboratory in Toulouse, and J. cedrus, using a single sample from Kew Gardens, London. Peraza and López (1967) studied J. cedrus and J. phoenicea var. canariensis from a single provenance (La Gomera), but did not speci- fy the size of the sample or compare the anatomy of the two species. Esteban et al. (2009a) did not describe the anatomy of J. cedrus and J. phoenicea var. canariensis, although they applied artificial neural networks for the first time as a tool for identifying the wood of species with very similar structure, obtaining accuracy percentages of 92% in the differentiation of these species. Their study will enable hypotheses to be proposed about wood and charcoal remains found at archaeological sites in both archipelagos and also about the palaeogeography of these species. A complete description of the wood of the three Macaronesian species, isolated for thousands of years in these Atlantic archipelagos, combined with a comparison through representative sample collections, would complement recent molecular phylogenetic studies on Juniperus in general (Mao et al. 2010) and more specifically on Juniperus in Macaronesia (Adams et al. 2010a, b; Rumeu et al. 2011). This study describes the wood anatomy of the three species of Juniperus in Maca- ronesia, defines their biometry, and determines whether the three species show differ- ences that will make it possible to differentiate them with qualitative and/or quantitative attributes. MATERIAL AND METHODS The samples were collected in the natural forests of the three species: Juniperus cedrus was collected only on the island of La Palma because of its level of protection; J. phoenicea var. canariensis on the islands of La Palma, la Gomera and El Hierro; and J. brevifolia on the island of Faial, from two areas of provenance, one at an altitude of approx. 70 m in the municipality of Castelete and the other in the area of Lagoa Do Capitao, at an altitude of 838 m. In each zone, five trees more than 70 years old and representative of the forest were felled, excluding compression wood. To locate the Canary Islands forests, the publication Downloaded from Brill.com10/08/2021 12:50:50PM via free access de Palacios et al. – Juniperus from Macaronesia 189 Figure 2– 8. Transverse sections. – 2: Sapwood and heartwood distinct (Juniperus brevifolia). – 3: Growth ring boundaries distinct (J. brevifolia). – 4: Abrupt transition from earlywood to latewood (J. brevifolia). – 5: Latewood only a few cells thick (J. phoenicea var. canariensis). – 6: Axial parenchyma diffuse and tangentially zonate (J. brevifolia). – 7: Intercellular spaces (J. phoenicea var. canariensis). – 8: Tracheid pits in tangential wall on growth ring boundary (J. phoenicea var. canariensis). — Scale bars for 3 & 6 = 250 μm; for 4 & 5 = 200 μm; for 7 & 8 = 100 μm. Downloaded from Brill.com10/08/2021 12:50:50PM via free access 190 IAWA Journal 35 (2), 2014 by Ceballos and Ortuño (1951) was used, and in the Azores, assistance was provided by the forest services of the island of Faial. Microscope slides were prepared following the usual methods of softening, section- ing, staining and mounting. Samples were observed without staining and stained with safranine for lignified cell walls and Sudan 4 for resin (Jane 1970). A Leica DM2500 light microscope with a DFC 420 camera was used, as well as image processing software IM50 v.5 release 220 and scanning electron microscopy (SEM) mod. JEOL JSM-6380. The anatomical descriptions were made in accordance with the IAWA Committee (2004). The biometry was conducted in three slides prepared from each tree, in all cases in mature wood, from a disc obtained 50 cm from the ground, between rings 70 and 100, using the WinCell image analysis programme. From each slide the following measure- ments were taken: 25 measurements of axial tracheid length and diameter, ray height (µm and number of cells), and number of pits per cross-field in the earlywood; 50 measurements of tracheid pit diameter and largest and smallest cross-field pit diameter in the earlywood; and five measurements of the number of rays per mm2. Tracheid length was measured following Ladell’s indirect method (Ladell 1959), ray frequency was measured in five different areas of one square millimetre on the tangential section. The standardised skewness and standardised kurtosis statistics were used to study normality and the ANOVA test was applied to analyse the samples and study the level of significance of the variables measured at species level. To determine the significant differences between species, multiple rank tests and LSD tests were applied using the ANOVA data, considering each species globally, without taking into account the different provenances in the cases of J. phoenicea and J. brevifolia. The study of the values of ray height in number of cells was performed using the frequency histogram and therefore the most frequent value does not correspond to the mean value but to the most frequent ray height. Statistical calculations were made with the Statgraphics Centurion Ver. 15.2 programme, for a 95% significance level. RESULTS Anatomical description General features — The wood of all three species is aromatic and the sapwood and heartwood are markedly different in colour: the sapwood is yellowish and the heartwood is reddish brown (Fig.