Meoiterranean Woooy Plant Growth-Forms, Biomass Ano Proouction in the Eastern Part of the Iberian Peninsula
Total Page：16
File Type：pdf, Size：1020Kb
Homage to Ramon Marga/ef; or, Why there is such p/easure in studying nature 337 (J. D. Ros & N. Prat, eds.). 1991 . Oec% gia aquatica, 10: 337-349 MEOITERRANEAN WOOOY PLANT GROWTH-FORMS, BIOMASS ANO PROOUCTION IN THE EASTERN PART OF THE IBERIAN PENINSULA JAUME TERRADAS Centre de Recerca Ecológica i Aplicacions Forestals (CREAF). Universitat Autónoma de Barcelona. 08 193 Bellaterra. Barcelona. Spain. Received: February 1990 SUMMARY The major physiognomic features of Mediterranean vegetation in the eastem part of the Iberian Peninsula are described considering a coastal and a continental gradient and oro-Mediterranean formations. The main communities include broadleaved evergreen forest, maquis, pine woodlands, "garigue", matorral, thom-scrub and dwarf-shrub steppes along mesic-xeric gradients, and pine-juniper woodlands and xeroacanthic cushion-like formations as altitudinal stages. We discuss sorne morphologico- functional traits of dominant plants from these different formations as related to environmental conditions, and their corresponding energy use strategies. Even though there are relatively few data on biomass and production, a broad synthetic approach is given, with sorne reference values. KEY WORDS : Mediterranean vegetation, growth-forms, biomass, production, energy use strategy INTRODUCTION Different shifts could thus be expected in vegetation structure and plant-grawth forms Two major mesic-xeric gradients are following each gradient. Other factors, such observed in the eastern part of the Iberian as wind, soil, etc., can also affect plant Peninsula (Fig. 1). One runs from the fitness and modify adaptation features. Pyrenees to the south, fram areas with Moreover, there are local deviations fram 700- 1 000 mm annual rainfall to areas with climatic general patterns due to local 190-350 mm. The second runs fram the climatic circumstances that will not be northeast coast to continental areas, and its considered here. annual rainfall ranges fram 600-700 mm to Mediterranean climax ecosystems have 300-400. In what fo llows we refer to them been discussed on phytosociological as coastal gradient and continental gradient. grounds by BOLOS (1985) for most of the Different temperature changes occur along area (Catalan countries), RIVAS (1974) for both gradients. Along the coastal gradient, the southern part, and RIV AS (1987) for all there is an increase in summer length, Spain. BOLOS (1985) distinguishes average temperature and winter rninima. between a boreo-Mediterranean pravince, Along the continental gradient, both winter with climax cornrnunities corresponding to length and thermic amplitude increase, Quercion ilicis alliance, an austra whereas winter mínima decrease. Mediterranean pravince, with climax 338 TERRADAS commumt1es corresponding to Rhamno (1974) identifies mature commumtles as Quercion coccife rae and Oleo-Ceratonion included in Asparago-Rhamnion oleoidis alliances, and a westem oro-Mediterranean and Periplocion angustifoliae alliances. province, corresponding to high and Ebro river valley vegetation is puzzling, moderately high Mediterranean mountains, and a Rhamno-Quercion cocciferae climax with Pino-Juniperion sabinae, Xeracantho has been classically assumed (BRAUN Erinaceion and Hypericion balearici climax BLANQUET & BOLOS 1957), but this communities, the last one found only in might be an incomplete view Majorca. (TERRADAS, 1986). In the southem end of the area, RIVAS 'l �4' oo --- .:.::. : ::.:. � Q::::�:: � - 7,6 { �-----::::--�- CONTINENTAL GRADIENT 400;¡¡'�.,oornrn EIVISSA .",-... Palma de Malior<:8 (10m) 400rnrn � ~ D Boreo-Alpine and Eurosiberian Regions D Boreo-Mediterranean Province • Au s tro-Mediterranean Province FIGURE 1. The eastern lberían Península and major features referred to ín the text. MEDITERRANEAN WOODY PLANT PHYSIOGNOMY 339 A PHYSIOGNOMIC DESCRIPTION phanerophyte with long shoots and short OF VEGETATION shoots (dolichoblasts and brachiblasts) and marked seasonal heteromorphism, and the From a morphological point of view, dwarf palm Chamaerops humilis. mature vegetation along the coastal gradient Floristically, they are similar to maquis and changes from the broadleaved evergreen so they are inc1uded by phytosociologists in forest to tall thicket matorral and maquis the Rhamno-Quercion alliance, but the (Oleo-Ceratonion), and thom-scrub physiognomy has shifted. We are near the commumt1es (Oleo-Ceratonion and tree border (which is found somewhere Asparago-Rhamnion). Broadleaved between 350 and 400 mm of annual evergreen forests are dominated by Quercus rainfall). AIso replacing communities after ilex ssp. ilex or, on sandy soils in the disturbance are c1early different: large northem part of the area, by Quercus suber. surfaces are covered by chamaephytes, i. e. These forests are often replaced by "tomillares" (Thymo-Siderition leucanthae), pine-oak mixed forests, by Quercion-ilicis or halophytic, nitrophilous or gypsophylous maquis with Arbutus unedo and Erica commumtIes, and by dry therophytic scoparia, or by matorral: Cistion grasslands. The typical thorny shrub mediomediterraneum on siliceous soils and growth-form diversifies to the south, when Quercus coccife ra "garigues" or c1imate becomes drier, with plants like Rosmarino-Ericion scrub on limestone, all Maytenus europaeus, Periploca of them often with pines. Forests, maquis angustifolia, Ziziphus lotus, Asparagus and "garigues" are commumt1es with albus or Lycium intricatum added to phanerophytes with plane leaves, often Rhamnus lycioides (Asparago-Rhamnion coriaceous or sc1erophyIlous and entire, as and Periplocion alliances). the dominant plants, whereas matorral The continental gradient begins at the commumt1es are richer in northeast edge with the broadleaved nanophanerophytes or chamaephytes with sc1erophyl1ous forest or maquis near the soft (malacophyllous) leaves, sometimes coast, which is soon replaced by an plane (like in Cistus species) but in other impoverished Quercus ilex ssp. cases leptophyllous (Erica) or linear. rotundifolia forest with Quercus coccife ra The austro-Mediterranean Oleo- "garigues " , Rosmarino-Ericion matorral or Ceratonion maquis is also dominated by pine woodlands as successional stages. At phanerophytes with coriaceous or sc1erophyllous leaves, mostly medium or ME IC small sized or divided (as in Ceratonia Quercus ilex evergreen sclerophyllous forest siliqua Pistacia lentiscus). or But this () Continental "- sc1erophyllous vegetation has very often ffix Pine Q.rotundifolia Maquis. "garigue" Steppe een been replaced by Cistion or Rosmarino �:�;�� '-- Mato rral Ericion cornmumtles. Malacophyllous ;�:�:��iS '" : Maquis plants beco me more frequent and diverse in Matorral o '---- this area. () In the southem part of the territory, eciduous forest maquis broadleaved evergreen Thorn-scrub phanerophytes like Olea europaea, Quercus Ev����:�n-oak "---- Dwarf-shru coccifera Pistacia lentiscus b and are XERIC steppe progressi vely replaced in mature F I GURE 2 . Major plant formations along the two communities by a thom-scrub. These mesic-xeric gradients and on Mediterranean communities are at first dominated by mountains. For the coastal gradient, degradation series Rhamnus lycioides, a malacophyllous are shown. 340 TERRADAS the Ebro valley, rainfall decreases fast and A dense forest is rarely obtained. broadleaved trees disappear, and are Summits of Iberían mountains and southem replaced by a pine woodland with a shrub "sierras" are occupied by spiny cushion-like understory also c1assified Xeracantho-Erinaceion communities, in a phytosociologically as Rhamno-Quercion poor forro if compared with Sierra Nevada coccife rae. Therroophyllous species of thís and Atlas equivalents. community, inc1uding the pine itself, are Spiny cushion-like shrubs are also gradually disappearing to the centre of the present aboye 1100 m in Majorca Ebro valley, where the winter c1imate (Hypericion balearici), with a different becomes colder. There, on gypsic ground, floristic composition. Xeroacanthic shrubs slopes and shallow soils are mostly covered can be considered as an interesting case of by a nitrophilous or gypsophilous evolutionary convergence in oro chamaephyte semidesert or steppe Mediterranean c1imates: different families (Salsolo-Peganion, Gypsophylion), whereas are represented by species with similar fine-textured loams are occupied by morphology in these highly fluctuating hemicryptophytic or rhizomatous geophytic windy environments. Similar forros are also perennial grasses (Agropyro-Lygeion). In found on the coasts of the Balearic islands, this landscape, a high diversity of in windy environments too. therophytes covers the free spaces between perennial grasses or shrubs during the short wet periods. Halophytic chamaephytes or DOMINANT WOODY GROWTH nanophanerophytes appear on saline soils, FORM near the bottom of undrained valleys. Further up the mountains in the northem We will now try to summarize the major part of the territory, extra-Mediterranean woody plant growth forros that dominate conditions are soon fo und, which Mediterranean landscapes in our terri tory . correspond to the Euro-Siberian or MARGARIS (198 1) has suggested two Boreo-Alpine regions. But in the Iberían main adaptation syndromes for and southem (sub-Betic, Betic and Mediterranean environments: maquis Penibetic) mountains, sorne features of plants, corresponding to typical Mediterranean c1imates reach higher sc1erophyllous woody plants, and phrygana altitudes. According to BOLOS (1985), plants (equi valents are said