Phenomorphology and Eco-Morphological Characters of Rhododendron Lauroid Forests in the Western Mediterranean (Iberian Peninsula, Spain)
Total Page：16
File Type：pdf, Size：1020Kb
Plant Ecology (2006) 187:227–247 Ó Springer 2006 DOI 10.1007/s11258-005-6574-0 -1 Phenomorphology and eco-morphological characters of Rhododendron lauroid forests in the Western Mediterranean (Iberian Peninsula, Spain) A.V. Pe´rez Latorre* and B. Cabezudo Departamento de Biologı´a Vegetal. Facultad de Ciencias, Universidad de Ma´laga, Apartado 59, E-29080 Ma´laga, Spain; *Author for correspondence (e-mail: [email protected]; fax: +34 952131944) Received 2 November 2004; accepted in revised form 25 April 2005 Key words: Functional types, Growth-forms, Phenophasic patterns, Relict, Rhododendron Abstract The evergreen broad-leaved forest of Rhododendron ponticum represents a special type of Mediterranean vegetation because of their relict nature (allegedly pre-glacial, Southern-Iberian and Pontic) and connection with Macaronesian-Atlantic flora. The findings of ecomorphological (growth forms) and phenological (phenology) studies point to characteristics typical of its relict character and its relationship with sub- tropical lauroid vegetation (greater forest stratification, larger leaves, high percentage of photosynthetic stems, scarce tomentosity, pre-flowering in a season different to Mediterranean species and closeness of autumn–winter flowering species). There are, however, links with typical Mediterranean vegetation (Quercus L. forests) that surrounds the Rhododendron stands, due to its adaptation to Mediterranean climate (sclerophyll leaves, plant and leaf duration, post-fire regeneration, fleshy fruit and fruit setting-seed dispersal seasonality). Within the community, different groups of plants show different adaptations to the same biotope, suggesting their distinct paleo-phytogeographical origins. The results confirm the singularity of this vegetation within the typically Mediterranean environment where it grows and its connections with other extra-Mediterranean types. Introduction (Box 1996), predicting its dynamism (Noble and Gitay 1996) even detecting species outside their The use of ecomorphology (growth forms) and ecological context (Herrera 1984, 1987). In the phenomorphology to study Mediterranean vege- case of Mediterranean vegetation, the standardi- tation and flora was first proposed by Orshan sation of methodology not only allows between (1982, 1983, 1986 and 1989). Growth forms pro- ecosystems comparison but also means it can be vide information on adaptive traits (Mooney 1974; used for describing as a function of ecomorpho- Le Roux et al. 1984; Pierce 1984), while a pheno- logical (growth forms) and phenomorphological morphological study provides data on the com- characteristics (Floret et al. 1987, 1990). The plete annual cycle concerning changes in the method has been used in Mediterranean regions of organs in relation to seasonal climatic changes and the world, including Australia (Pate et al. 1984), plant architecture. These methods, which may be Chile (Orshan et al. 1984; Montenegro et al. included in the broad definition of ‘functional 1989), France (Floret et al. 1987, 1990; Romane types’ (Box 1987), have confirmed excellent for 1987), Israel (Danin and Orshan 1990; Keshet cataloguing vegetation (Nemani and Running et al. 1990), South Africa (Le Roux et al. 1989) 1996), relating vegetation with climatic parameters and Spain (Cabezudo et al. 1992, 1993; Pe´rez 228 Latorre et al. 1995, 2001; Caritat et al. 1997; Pe´rez Latorre et al. 2000). Called ‘ojaranzal’ in Navarro and Cabezudo 1998; Castro Dı´ez and Spanish, this community is uniquely found in SW Montserrat Martı´1998; Pe´rez Latorre and Cab- Iberia within western Europe (Spain and Portugal) ezudo 2002). Pe´rez Latorre and Cabezudo (2002) (Pe´rez Latorre et al. 1996) and belongs to the proposed a synthesis of the Orshan’s method to be Western Mediterranean relict lauroid vegetation applicable to Mediterranean climate regions in the (Rhododendretalia pontici Pe´rez Latorre et al. world. The synthesis was applied to woodlands 2000, Pruno-Lauretea azoricae Oberdorfer ex (Quercus suber L., Fagaceae) and shrublands (Ci- Sunding 1972) (Cabezudo and Pe´rez Latorre stus L. spp., Cistaceae) in Spain, observing clear 2001). In Spain, its most important representative distinctions between the two formations as regards is found in Andalusia (Los Alcornocales Natural both ecomorphological (growth forms) and phe- Park, Cadiz Province; Pe´rez Latorre et al. 1999) nological parameters (phenophases and related while much smaller populations are found in the indexes). Sierras de Monchique and Vouzela in Portugal Here we continue this line of work by applying (Pereira Dı´as and Barros de Sa Nogueira 1973; the method proposed by Pe´rez Latorre and Cab- Malato Beliz 1982). The most unusual floristic ezudo (2002) to a type of vegetation of great paleo- characteristic of this community is the brio-pte- phytogeographical and conservation interest: the ridophytic stratum with species which have a paleomediterranean relict lauroid forests of Rho- Macaronesian-Atlantic optimum or paleomedi- dodendron ponticum L. (Ericaceae). These date terranean origin (such as Lepidopilum virens Card., from the end of the Tertiary (Que´zel 1985; Mai Tetrastichium fontanum (Mitt.) Card., Neckera 1989) and are now relegated to the extreme en- intermedia var. laevifolia (Schiffn.) Renauld and claves of western (Strait of Gibraltar) to eastern Cardot, Homalia webbiana Mont., Isopterygium (Bosphorus) Mediterranean, showing climatic bottini (Breidl.) Broth-Bryophyta-. Culcita macro- peculiarities in both sites. carpa C. Presl., Diplazium caudatum (Cav.) Jer- The main objective of this work is to characte- myPteris incompleta Cav., Vandenboschia speciosa rise and describe this kind of plant community (Willd.) Kunkel -Pteridophyta-) (Salvo 1990; Gu- using ecomorphology and phenomorphology and erra et al. 2003). to study the relationships with the ecological parameters of the biotope where it develops. An- other objective is to analyse the standardised data Study site to discuss the originality or similarity of Rhodo- dendron forest to other kind of typically Mediter- The study site was chosen taking into consideration ranean forest (Quercus suber). We also try to make the presence of most of the species belonging to the an approach to eco-phenomorphological grouping community and the state of conservation. The se- of species following a combination of their eco- lected R. ponticum stand (Figure 1) lies within a morphological and phenophasic patterns. Finally, protected area (Los Alcornocales Natural Park, we try to find characters that support the relict Los Barrios municipality, Dehesa de Oje´n) in the origin of Rhododendron forests and its eco-phe- province of Cadiz (Spain). The riparian site occu- nomorphological relations to present lauroid veg- pies a 10 m wide, 20 m long stretch at 350 m a.s.l. etation. (5°36¢ W/36°7¢ N). A permanent stream flows on siliceous sands, the bed of which contains large rocky blocks. The soil data (Table 1) point to a low Methods pH and the absence of carbonates, while climatic data (Figure 2, Table 2) reveal a typically Medi- Vegetation terranean warm climate (thermomediterranean bioclimatic belt with an average annual tempera- The studied vegetation type corresponds to ripar- ture of 17.6 °C) and much rain (humid ombrotype, ian forest dominated by Rhododendron ponticum average annual rainfall of 1078 mm) although with (Scrophulario laxiflorae–Rhododendretum pontici a dry period between July and August. 229 Figure 1. Little rectangle: distribution of Rhododendron ponticum L. in Spain and general view of the study area. Black dot: location of the selected plot in the Natural Park of ‘Los Alcornocales’ (Sierra de Oje´n, Ca´diz province). White dots correspond to other R. ponticum forests (localities taken from (Pe´rez Latorre et al. 1999, 2000). 230 Table 1. Main soil characteristics in the area of the study site. Table 2. Weather station at Los Barrios (Polvorilla), Ca´diz (5°34¢ W/36°15¢ N). Parameter Type/data JFMAMJJASOND Soil type Alfisol Rock type Siliceous sandstones Mean annual rainfall (mm) 163.5 169.5 104.7 84.7 50.5 14.8 0.9 2.9 27.7 101.8 191.5 165.8 pH horizon A (H2O) 5.6 C/N horizon A 15.7 Mean annual temperature (°C) 13.2 14.6 15.2 15.9 18.2 21.3 23 22.4 20.8 16.9 15.3 14.3 CO3 horizon A 0 pH horizon B (H O) 4.7 2 It (Thermicity index) = 425, lower thermomediterranean bio- C/N horizon B 11.2 climatic belt with lower humid ombrotype (Rivas Martı´nez CO horizon B 0 3 classification 1987). Mean annual temperature = 17.6 °C. Absolute minimum temperature = 2 °C. Absolute maximum temperature = 40 °C. Mean annual rainfall = 1078 mm. Days of rainfall = 61.5. 120 Mean annual rainfall (mm)/2 ephemerals (terophytes) and ephemeroids (some geophytes and hemicryptophytes) were not in- 100 Mean annual temperature (ºC) cluded in the studies, because their shoots disap- pear during the unfavourable season (Evenari 80 et al. 1975). The ecomorphological characters (growth forms) were determined for each species in 60 the field. Twenty-eight characters of those pro- posed by Orshan (1986) were studied as well as 40 fruit type (fleshy, dry), as proposed in (Pe´rez La- torre et al. 1995). Afterwards a species/character 20 data matrix was made and the percentage of presence of each character expression was calcu- 0 lated on the basis of number of species showing JFMAMJJASOND that character (see Appendix A). For the eco- Figure 2. Climatic diagram of the study area. morphological description of the communities and the subsequent comparison, we used the characters and indices proposed by Pe´rez Latorre and Cab- Ecomorphology ezudo (2002) including Estimated Biomass of the Species (EBS) = plant height (m) · crown diam- For this ecomorphological study, we used the eter (m) · canopy or branch density (%), and method standardised by Orshan (1982, 1986), Estimated Biomass of the Community while following the proposal by Orshan (1989) for (EBC) = sum of EBS’s of all the species. Figure 3 the phenological study. A selective plant inventory shows the relative flat form of each species and its was made in the locality, according to the presence positioning into the community structure.