Relations between climax vegetation and

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Relations between climax vegetation and isobioclimates in the Northwest of Spain (León province) a

b

David Ríos-Cornejo , Sara del Río & Ángel Penas

b

a

Departamento de Biodiversidad y Gestión Ambiental (Área de Botánica), Facultad de Ciencias Biológicas y Ambientales, Universidad de León, Campus de Vegazana, s/n., E-24071, León, Spain b

Departamento de Biodiversidad y Gestión Ambiental (Área de Botánica), Instituto de Ganadería de Montaña (Centro Mixto CSIC-ULE), Facultad de Ciencias Biológicas y Ambientales, Universidad de León, Campus de Vegazana, s/n., E-24071, León, Spain Version of record first published: 02 Aug 2012

To cite this article: David Ríos-Cornejo, Sara del Río & Ángel Penas (2012): Relations between climax vegetation and isobioclimates in the Northwest of Spain (León province), Acta Botanica Gallica, 159:2, 267-276 To link to this article: http://dx.doi.org/10.1080/12538078.2012.696939

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Acta Botanica Gallica: Botany Letters Vol. 159, No. 2, June 2012, 267–276

Société botanique de France

Relations between climax vegetation and isobioclimates in the Northwest of Spain (León province) Relations entre la végétation climax et les iso-bioclimats existants dans le Nord-Ouest de l’Espagne (province de León)

Downloaded by [Universidad de Leon], [Sara del Río] at 01:36 03 August 2012

David Ríos-Cornejoa, Sara del Ríob* and Ángel Penasb a Departamento de Biodiversidad y Gestión Ambiental (Área de Botánica), Facultad de Ciencias Biológicas y Ambientales, Universidad de León, Campus de Vegazana, s/n., E-24071 León, Spain; bDepartamento de Biodiversidad y Gestión Ambiental (Área de Botánica), Instituto de Ganadería de Montaña (Centro Mixto CSIC-ULE), Facultad de Ciencias Biológicas y Ambientales, Universidad de León, Campus de Vegazana, s/n., E-24071 León, Spain

Abstract: This paper determines the isobioclimates existing in the province of León (north-western Spain) as the result of combining macrobioclimates, bioclimates, bioclimatic variants, thermotypes, ombrotypes and their corresponding bioclimatic horizons, all obtained from the analysis of eighty-three transects distributed throughout the study area The relations between isobioclimates and climax vegetation are also analysed. Twenty-six different isobioclimates are identified (15 temperate and 11 Mediterranean). Most vegetation series develop in the supratemperate humid and hyperhumid isobioclimates. Keywords: isobioclimates; León province; Spain; vegetation series Résumé: Dans ce travail nous avons étudié différents iso-bioclimats existants dans la province de León (Nord-Ouest de l’Espagne), ce sont des unités résultantes de la combinaison des macro-bioclimats, bioclimats, variants bioclimatiques, thermotypes, ombrotypes et ses horizons bioclimatiques correspondants. Ces unités ont été obtenues à partir de l’analyse de quatre-vingt trois transepts, distribués par toute la zone d’étude Selon les données précédentes nous avons reconnu vingt-six différents iso-bioclimats (quinze Tempérés et onze Méditerranéens). C’est dans les iso-bioclimats supra-tempérés humide et hyper-humide où se développe la plupart de séries de végétation. Nous avons aussi analysé la relation entre ces iso-bioclimats et la végétation climax. Mots clés: Espagne; iso-bioclimats; province de León; séries de végétation

Introduction A detailed interpretation and analysis of the climate in a particular area is essential to understand the kind of vegetation that may develop in that area. Hence, considering the climatic and edaphic typology in a specific area, it is possible to predict the climactic vegetation developing in it. As a consequence, the study of the natural potential vegetation existing in a particular region is necessary to apply management and conservation actions. Bioclimatology, and more specifically Phytoclimatology, can be defined as the science dealing with the relationship between climate and the distribution of plant communities around the world. This reciprocity between climate and vegetation is useful when drawing bioclimatic and biogeographic maps. The main aim of this science is to describe the relationships between the main numeric climatic values (temperature and precipitation) and the distribution patterns of plant communities. *Corresponding author. Email: [email protected] ISSN 1253-8078 print/ISSN 2166-3408 online Copyright Ó 2012 Société botanique de France http://dx.doi.org/10.1080/12538078.2012.696939 http://www.tandfonline.com

The increasingly detailed knowledge of vegetation distribution on Earth, together with aspect and composition modifications in plant communities and their vegetation stages, enables bioclimatic and vegetation boundaries to be recognized accurately and objectively, as it is possible to calculate statistically the threshold numeric values that define them (Rivas-Martínez et al. 2007). The relationship between climate and vegetation has been studied by various authors (Köppen 1948; Walter 1976; Prentice et al. 1992; Box 1996; Woodward and Cramer 1996; Foley et al. 1998; Gavilán, FernándezGonzález and Blassi 1998; Rivas-Martínez and Loidi 1999; Rivas-Martínez, Sánchez-Marta and Costa 1999; González-Rebollar et al. 2000; Oturbay and Loidi 2001; Rivas-Martínez 2002a, 2002b; Gordon et al. 2003; Hossell, Riding and Brown 2003; Sanz-Elorza et al. 2003; del Río 2005; del Río, Penas and Pérez-Romero 2005;

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D. Ríos-Cornejo et al.


del Río, Herrero and Penas 2007, 2009; Gavilán, 2005; del Río and Penas 2006a, 2006b; Gavilán et al. 2007). This paper establishes the altitudinal limits of different bioclimatic units (macrobioclimates, bioclimates, thermotypes and ombrotypes, and their corresponding bioclimatic horizons, together with bioclimatic variants) taking into account the bioclimatic analysis of 83 transects in the province of León. The combination of all the units recognized in the study area has made it possible to determine the different isobioclimates that exist in that area. This study has also analysed the relationship between these bioclimatic units and the climax vegetation in the province of León. Study area The province of León is located in north-western Spain (Figure 1) and belongs to the region of Castile and León, together with another eight provinces. León is the largest of all the provinces, with a land area of 15468 km2. There are two main geomorphological characteristics in the region: the mountains and the plateau. In addition, the province comprises the depression of El Bierzo in the west (Junta de Castilla y León 1988). The various mountainous areas in the province of León have been grouped as follows: North-western Cantabrian Range

Figure 1. Figure 1.

Situation of León province in Spain. Situation de la province de León en Espagne.

(including Sierra del Padrón, Sierra de los Ancares and Sierra del Caurel), Central Cantabrian Range (Sierra de La Filera, Sierra del Gistreo, Sierra de Los Grajos and Sierra de la Cuerna), North-eastern Cantabrian Range (Picos de Europa, Macizo de Peña Prieta, Sierra de Mampodre and Sierra de Riaño) and South-western Mountains (Montes Aquilianos, Montes de León, Sierra del Teleno, Sierra de la Cabrera Baja and Sierra Cabrera), as shown in Figure 1. The lowest altitude in the study area is 360 m, where León is bounded by the province of Orense. The highest altitude is 2648 m (Torre Cerredo) and is located in the North-east of the province (Picos de Europa). As there are remarkable topographic differences, there are also thermo-pluviometric variations in the study area. The precipitation is distributed very unevenly, with areas where the records show up to 1500 mm (in the Central Cantabrian Range) or about 2000 mm (in the North-western Cantabrian Range). On the other hand, precipitation values registered in the plateau are remarkably lower. This general trend is not valid in El Bierzo, where there is a staggered topographic distribution of precipitations, and the rugged relief causes numerous pluviometric contrasts. As far as temperatures are concerned, a long winter contrasts with the shortness of the warm and dry summer


Acta Botanica Gallica: Botany Letters (mainly in areas with Mediterranean macrobioclimate). The whole province has temperatures below zero on many days during the long winter, except in some microclimatic areas. These low temperatures usually start in September and end in May or June, so spring and autumn are consequently very short. As a result of the varied orography, climatology and edaphology in the study area, there is a significant number of vegetation series and permaseries. According to Penas, García and Herrero (1995) and Penas, García, Herrero and Puente (1995a), we have recognized two climax cryorotemperate grasslands vegetation permaseries (Oxytropido pyrenaicae-Elyno myosuroidis permasigmetum and Junco trifidi-Oreochloo blankae permasigmetum), four climax shrub vegetation series (Junipero nanae-Vaccinio microphylli S., Vaccinio myrtilli-Junipero nanae S., Daphno cantabricaeArctostaphylo uvae-ursi S. and Genisto sanabrensisJunipero nanae S.) and 14 forests vegetation series (Luzulo cantabricae-Betulo celtibericae S., Blechno-Fago sylvaticae S., Epipactido helleborines-Fago sylvaticae S., Carici sylvaticae-Fago sylvaticae S., Omphalodo nitidaeFago sylvaticae S., Linario triornithophorae-Querco petraeae S., Linario triornithophorae-Querco pyrenaicae S., Festuco braun-blanquetii-Querco pyrenaicae S., Genisto falcatae-Querco pyrenaicae S., Junipero sabinothuriferae S., Cephalanthero longifoliae-Querco rotundifoliae S., Junipero thuriferae-Querco rotundifoliae S., Junipero oxycedri-Querco rotundifoliae S. and Genisto hystricis-Querco rotundifoliae S.). Edaphohygrophilous vegetation series have not been considered in this study.

269

Index), Itc (Compensated Thermicity Index), Io (Ombrothermic Index), Ios1 (Ombrothermic Index of the driest month of the summer quarter), Ios2 (Ombrothermic Index of the driest bimonth of the summer quarter), Ios3 (Ombrothermic Index of the summer quarter) and Ios4 (Ombrothermic Index of the summer quarter together with the immediately preceding month). These ombrothermic indices have a high discriminatory value to establish the boundary between Temperate and Mediterranean macrobioclimates (Rivas-Martínez et al. 2007). Once the diagnoses were known, we calculated the altitudinal limits between the following bioclimatic units in the study area: macrobioclimates, bioclimatic variants, bioclimates, thermotypes and ombrotypes and their bioclimatic horizons. After determining in each transect the macrobioclimates, the bioclimatic variants (if any) and the bioclimatic belts (thermotypes and ombrotypes) with their corresponding horizons, we defined the isobioclimates in the study area. Isobioclimates are bioclimatic units consisting of one type of bioclimate delimited by certain thermotypes and ombrotypes (Rivas-Martínez et al. 2007). The isobioclimate is the basic study unit in this paper. Relationship between isobioclimates and climax vegetation The data on vegetation series and permaseries (vegetation series map, 1: 400,000 scale, Penas, García, Herrero and Puente 1995a) and the isobioclimates identified in the study area were used to establish the relation between these bioclimatic units and the climacic vegetation in the province of León.

Material and methods Bioclimatic characterization Eighty-three geographic points were selected in some peaks throughout the province of León, and then a transect was drawn from each point following a north–south direction. The monthly temperature and precipitation average values (Ti and Pi, respectively) have been calculated taking into account Penas, García, Herrero and Puente (1995b), García, Herrero, Puente and de Godos (1995) and SánchezPalomares, Sánchez-Serrano and Carretero-Carrero (1999). The bioclimatic diagnosis of each transect was carried out according to the bioclimatic classification by RivasMartínez et al. (2007). To do this, the following bioclimatic parameters and indices were used: Ti (Average Temperature in every month of the year), Pi (Average Precipitation in every month of the year), Tp (Yearly Positive Temperature), Pp (Yearly Positive Precipitation), T (Yearly Temperature in degrees centigrade), M (Average maximum temperature of the coldest month of the year), m (Average minimum temperature of the coldest month of the year), Tmax (Average temperature of the warmest month), Tmin (Average temperature of the coldest month), Ic (Continentality Index), It (Thermicity

Results and discussion Limits between macrobioclimates and bioclimates The contact line between Temperate and Mediterranean macrobioclimates is the same as the one between Temperate oceanic and Mediterranean pluviseasonal oceanic bioclimates, and they vary all along the boundary line with changing altitude. In the North-eastern Cantabrian Range, it is dependent on which slope is referred to. Hence, in the northern slope this limit is below 600 m, whereas in the southern slope it lies at 1140 m, and this altitude is common in all the transects of the Northeastern Cantabrian Range. Generally, in the Léonese Central Cantabrian Range that limit was found at 1200 m, decreasing to 1170 m towards the western areas analysed. The limit was even found at 850–900 m, because the Ombrothermic Index in these areas is very high and the summer precipitation easily compensates the summer drought. This is the reason why the boundary between Mediterranean and Temperate macrobioclimate lies at a lower altitude. Finally, the Temperate–Mediterranean boundary in the Southwestern Mountains was found at 1220 m, slightly higher

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than in the other Leonese mountains, because of their southern latitude. These results are coincident with those found by Lence (2001) in the Valley of Valdeburón and by Alonso (2003) in the Upper Basin of the River Esla, both in the North-eastern Cantabrian Range. Findings by del Egido (2009) in the River Torío (Central Cantabrian Range), by Rivas-Martínez et al. (2002a) in Spain and Portugal and by del Río (2005) in Castile and León also confirm the results found in this paper.


Limits of the submediterranean variant Submediterraneity has also been found at different altitudes depending on the mountains we are referring to. Hence, in the North-eastern Cantabrian Range it has been found at 850 m on the northern slope and at 1750 m on the southern slope; it has been located at 1850 m in the Central Cantabrian Range, at 1300 m in the North-western Cantabrian Range and at 1820 m in the South-western Mountains. These results differ from those found by Lence (2001) (North-eastern Cantabrian Range), Alonso (2003) (North-eastern Cantabrian Range) and del Río (2005) because these authors based their studies on previous bioclimatic classifications (Rivas-Martínez and Loidi, 1999; Rivas-Martínez et al. 2002a). However, they are coincident with the studies carried out in the River Torío by del Egido (2009) (Central Cantabrian Range), as the same criterion was applied to determine the submediterranean bioclimatic variant as in this paper.

Figure 2. Areas (in km2 and%) of thermotypic horizons. mmes, upper mesomediterranean; smei, lower supramediterranean; smes, upper supramediterranean; mtes, upper mesotemperate; stei, lower supratemperate; stes, upper supratemperate; otei, lower orotemperate; otes, upper orotemperate; ctei, lower cryorotemperate. Figure 2. Surfaces (en km2 et%) des horizons thermotypiques. mmes, meso méditerranéen supérieur; smei, supraméditerranéen inférieur; smes, supra-méditerranéen supérieur; mtes, meso-tempéré supérieur; stei, supratemperate inférieur; stes, supratemperate supérieur; otei, oro-tempére inférieur; otes, oro-tempére supérieur; ctei, cryoro tempére inférieur.

The cryorotemperate thermotype was found only in specific areas over 2250 m in the North-eastern and Central Cantabrian Range. The boundary separating the upper and lower orotemperate horizons was found at 1880 m in the

Limits between thermotypes and their bioclimatic horizons Nine horizons (three Mediterranean and six Temperate ones) have been recognized, whose surface area and percentages are shown in Figure 2. The following Mediterranean thermotype horizons have been identified: upper supramediterranean, lower supramediterranean and upper mesomediterranean. The supramediterranean thermotype (upper and lower) covers 58.57% of the study area. Mesomediterranean thermotype covers 2.48% of El Bierzo exclusively at altitudes below 600 m. It is remarkable that these areas are the only ones in León where a mesomediterranean thermotype is found, according to Rivas-Martínez et al. (2002a) and del Río (2005). The limit between upper and lower supramediterranean thermotypes has been found at about 980 m in the South-west of the province, at about 960 m in the Northwest, and at 900 m in the eastern half of the province. On the other hand, the boundary between supratemperate and supramediterranean thermotypes is exactly the same as the Temperate–Mediterranean boundary. Temperate thermotypes and horizons found in the study area were: lower cryorotemperate, upper and lower orotemperate, upper and lower supratemperate and upper mesotemperate.

Figure 3. Areas (in km2 and%) of ombrotypic horizons. ses, upper dry; sui, lower subhumid; sus, upper subhumid; hui, lower humid; hus, upper humid; hhi, lower hyperhumid; hhs, upper hyperhumid; uhu, ultrahyperhumid. Figure 3. Surfaces (en km2 carrés et%) des horizons ombrotypiques. ses, sec supérieur; sui, sub-humide inférieur; sus, sub-humide supérieur; hui, humide inférieur; hus, humide supérieur; hhi, hyper-humide inférieur; hhs, hyper-humide supérieur; uhu, ultrahyper-humide.

Acta Botanica Gallica: Botany Letters

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Table 1. Temperate oceanic isobioclimates. Tableau 1. Iso-bioclimats Tempéré océanique. Ombrotypic horizons

Temperate oceanic bioclimate Thermotypic horizons

mte ste ote


cte

sup. inf. sup. inf. sup. inf.

hum

hhu

shu sup.

inf.

sup.

inf.

sup.

uhu inf.

• + • • • •

• + + • • •

+ + + • • •

• + + + + •

• • + + + •

• • • • + +

shu, subhumid; hum, humid; hhu, hyperhumid; uhu, ultrahyperhumid; mte, mesotemperate; ste, supratemperate; ote, orotemperate; cte, cryorotemperate; sup., upper; inf., lower; +, presence; •, absence. shu, sub-humide; hum, humide; hhu, hyper-humide; uhu, ultrahyper-humide; mte, meso-tempéré; ste, supra-tempéré; ote, oro-tempéré; cte, cryorotempéré; sup., supérieur; inf., inférieur; +, présence; •, absence.

Table 2. Mediterranean pluviseasonal oceanic isobioclimates. Tableau 2. Iso-bioclimats Méditerranéen Pluvisaisonnier océanique. Ombrotypic horizons

Mediterranean pluviseasonal oceanic bioclimate Thermotypic horizons

mme sme

sup. inf. sup.

shu

hum

sec sup.

inf.

sup.

inf.

sup.

• + •

+ + •

+ + +

+ + +

• + +

sec, dry; shu, subhumid; hum, humid; mme, mesomediterranean; sme, supramediterranean; sup., upper; inf., lower; +, presence; •, absence. sec, sec; shu, sub-humide; hum, humide; hhu, hyper-humide; uhu, ultrahyper-humide; mme, meso-méditerranéen; sme, supra-méditerranéen; sup., supérieur; inf., inférieur; +, présence; •, absence.

Figure 4. Figure 4.

Areas (in km2 and%) of each identified isobioclimate. Abbreviations of isobioclimates in Appendix I. Surfaces (en km2 et%) de chaque iso-bioclimat identifiqué. Abréviations des iso-bioclimats dans l’annexe 1.


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Figure 5. Number of vegetation series and permaseries found in each isobioclimate. Abbreviations of isobioclimates in Appendix 1. Figure 5. Nombre de séries et permaséries de végétation trouvées dans chaque iso-bioclimat. Abréviations des iso-bioclimats dans l’annexe 1.

North-eastern and Central Cantabrian Range and at 1900 m in the South-western Mountains. The limit existing between orotemperate and supratemperate thermotypes was found at 1510 m. However, in the South-western Mountains it was recognized at 1530 m. These limits confirm those proposed by Lence (2001) (North-eastern Cantabrian Range) and del Egido (2009) (Central Cantabrian Range). Finally, the boundary between upper and lower supratemperate horizons shows moderate differences: in general, in the North-eastern, Central and part of the North-western Cantabrian Range, it was found at 1100 m, at 1060 m in the South of North-western Cantabrian Range and between 1100 m and 1180 m in the Southwestern Mountains. Mesotemperate thermotype has only been identified in two valleys (Cares and Sella) in the North-eastern Cantabrian Range, covering a very small area (0.06%). Roughly speaking, the limit between this thermotype and lower supratemperate one was found around 680 m. These results are coincident with those found by Rivas-Martínez et al. (2002a) and del Río (2005). Penas, García, Herrero, Puente and de Godos (1995d) also

obtained similar results, although they considered three horizons instead of two. Limits between ombrotypes and their bioclimatic horizons Ombrotypes and horizons found in the study area were: ultrahyperhumid, upper and lower hyperhumid, upper and lower humid, upper and lower subhumid and upper dry ones (Figure 3). Ultrahyperhumid ombrotype is very limited (0.09%) and has been identified occasionally in areas above 2220 m in the North-eastern Cantabrian Range and over 2095 m in the Central Cantabrian Range. The hyperhumid ombrotype covers one-quarter of the province (24.61%). The limit between upper and lower hyperhumid ombrotypes has been established at about 1500 m and 1600 m in the North-western Cantabrian Range, at about 1800 m and 1850 m in the Central Cantabrian Range, between 1650 m and 1750 m in the North-eastern Cantabrian Range, and finally at 1700 m in the South-western Mountains. The altitudinal limit between lower hyperhumid and upper humid types shows great variability: 1000 m in

Jt-Ob

• • • • • • • • • • • • • • • • • • • • • • • • • +

Op-Em

• • • • • • • • • • • • • • • • • • • • • • • • • +

• • • • • • • • • • • • • • • • • • • • + + + + + •

Jn-Vm

• • • • • • • • • • • • • • • • • • • • + + + + + •

Vm-Jn

Abbreviations in appendix 1. +, presence; •, absence. Abréviations dans l’annexe 1. +, présence; •, absence.

mmesposui mmesposus mmespohui smeiposes smeiposui smeiposus smeipohui smeipohus smesposus smespohui smespohus mtesohus steiosus steiohui steiohus steiohhi stesohui stesohus stesohhi stesohhs oteiohhi oteiohhs otesohhi otesohhs otesouhu cteiouhu

Isobioclimates • • • • • • • • • • • • • • • • • + + + + + + + + •

Dc-Au • • • • • • • • • • • • • • • • • • • • + + + + + •

Gs-Jn • • • • • • • • • • • • • • • • • + + + + + • • • •

L-Bc • • • • • • • • • • • • • • • • • + + + • • • • • •

B-Fs • • • • • • • • • • • + • • + + • + + • • • • • • •

Eh-Fs • • • • • • • • • • • • • • • • • + + + • • • • • •

Cs-Fs • • • • • • • • • • • • • • • • • • + + • • • • • •

On-Fs

Vegetation • • • • • • • • • • • • • • • • • + + + • • • • • •

Lt-Qpe

Table 3. Relation between vegetation series and permaseries developing in different isobioclimates. Tableau 3. Relation entre les séries et permaséries de végétation et les iso-bioclimats présents dans la zone d’étude.

• • • • • • • • • • • • + + + • + + • • • • • • • •

Lt-Qpy • • • • • • • • + + + • • • • • • • • • • • • • • •

Pl-Qp


• + + • + + + + • + + • • + + + + + + • • • • • • •

Gf-Qp • • • • • • • • • • • • • + • • + + • • • • • • • •

Js-t • • • • • • • • • • • + • + + • • • • • • • • • • •

Cl-Qr

• • • + + • • • • • • • • • • • • • • • • • • • • •

Jt-Qr

• • • + + • • • + + • • • • • • • • • • • • • • • •

Jo-Qr

+ + + • + + • • • • • • • • • • • • • • • • • • • •

Gh-Qr

Acta Botanica Gallica: Botany Letters 273


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the North-western Cantabrian Range; between 1300 and 1350 m in the Central Cantabrian Range; about 1250 m and 1300 m in the North-eastern Cantabrian Range, and between 1250 m and 1350 m in the South-western Mountains. These results coincide with those found by del Egido (2009) in the Upper Basin of the River Torío (Central Cantabrian Range). The limit between upper and lower humid ombrotypes was found at 1100 m in the eastern half of the province, at 1000 m in the South-western Mountains and at 720 m in El Bierzo. Humid and subhumid ombrotypes contact at 850 m throughout the study area except in El Bierzo, where it was found between 600 and 700 m. The limit between upper and lower subhumid types was found at 860 m in the plateau, at 800 m in the South-west and at about 450 m and 550 m in El Bierzo. Subhumid territories represent 32.65% of the study area. Dry ombrotype, covering 9.14% of the province, was found below 780 m in the western half of the plateau and below 830 m in the eastern half. These results differ from those indicated by Penas, García, Herrero and Puente (1995b), but this is because their calculations were based on yearly precipitation and not on the Ombrothermic Index. In addition, these authors considered three horizons instead of two. Isobioclimates The number of isobioclimates identified as the result of combining macrobioclimates, bioclimates, bioclimatic belts and their bioclimatic horizons in the province of León was twenty-six (Tables 1 and 2). Figure 4 represents the surface areas (in km2 and%) of those isobioclimates. Of the 26 isobioclimates, 15 are Temperate and 11 are Mediterranean, although the latter cover much more land than the Temperate ones. A higher bioclimatic diversity was found in Temperate areas despite the fact that they were smaller. The most common isobioclimate in the province is the lower supramediterranean pluviseasonal oceanic lower subhumid type, and the least common is the upper oceanic orotemperate ultrahyperhumid type. Relation between isobioclimates and climax vegetation Knowing the isobioclimates in the province of León has enabled us to establish the relation between them and the climax vegetation developing in this area. Table 3 shows the vegetation series and permaseries which may develop in each isobioclimate identified. Temperate isobioclimates are the ones that may be home to the highest number of vegetation series and permaseries; in particular, upper oceanic supratemperate upper humid type is quite remarkable because it may be home to nine different vegetation series, and upper supratemperate oceanic lower hyperhumid type may be home to eight vegetation series. On the other hand, it may be seen that in highmountain isobioclimates, that is, mainly lower cryoro-

temperate oceanic ultrahyperhumid type and upper orotemperate oceanic ultrahyperhumid type, the number of series developing in them is low (two and four, respectively). The same is true of other isobioclimates such as upper mesomediterranean pluviseasonal oceanic lower subhumid type, lower supramediterranean pluviseasonal oceanic lower humid type, lower supramediterranean pluviseasonal oceanic upper humid type and lower supramediterranean pluviseasonal oceanic upper subhumid type, in which only one vegetation series develops. Many vegetation series can live in the same isobioclimate in the province of Léon because there are many relevant factors involved (characteristics of soil, geomorphology, biogeography, etc.). Conclusions The following conclusions can be reached on the basis of this study. The following bioclimatic units have been identified in the study area: two macrobioclimates, three bioclimates, nine thermotypic horizons, eight ombrotypic horizons and twenty-six isobioclimates. The bioclimatic belt in which most of the vegetation series and permaseries can develop is upper supratemperate oceanic upper humid type. The correlation between isobioclimates and vegetation series and permaseries is not bi-univocal, because other factors, such as edaphology and geomorphology, determine an important variability of vegetation units (subseries).

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Appendix 1. Abbreviations used in the text. Annexe 1. Abréviations Vegetation series and permaseries: Op-Em, Oxytropido pyrenaicae-Elyno myosuroidis permasigmetum; Jt-Ob, Junco trifidi-Oreochloo blankae permasigmetum; Jn-Vm, Junipero nanae-Vaccinio microphylli S.; Vm-Jn, Vaccinio myrtilli-Junipero nanae S.; Dc-Au, Daphno cantabricaeArctostaphylo uvae-ursi S.; Gs-Jn, Genisto sanabrensisJunipero nanae S.; L-Bc, Luzulo-Betulo celtibericae S.; B-Fs, Blechno-Fago sylvaticae S.; Eh-Fs, Epipactido helleborines-Fago sylvaticae S.; Cs-Fs, Carici sylvaticaeFago sylvaticae S.; On-Fs, Omphalodo nitidae-Fago sylvaticae S.; Lt-Qpe, Linario triornithophorae-Querco petraeae S.; Lt-Qpy, Linario triornithophorae-Querco pyrenaicae S.; Pl-Qp, Pulmonario longifoliae-Querco pyrenaicae S.; Gf-Qp, Genisto falcatae-Querco pyrenaicae S.; Js-t, Junipero sabino-thuriferae S.; Cl-Qr, Cephalanthero longifoliae-Querco rotundifoliae S.; Jt-Qr, Junipero thuriferae-Querco rotundifoliae S.; Jo-Qr,

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Junipero oxycedri-Querco rotundifoliae S.; Gh-Qr, Genisto hystricis-Querco rotundifoliae S. Isobioclimates: mmesposui, upper mesomediterranean pluviseasonal oceanic lower subhumid; mmesposus, upper mesomediterranean pluviseasonal oceanic upper subhumid; mmespohui, upper mesomediterranean pluviseasonal oceanic lower humid; smeiposes, lower supramediterranean pluviseasonal oceanic upper dry; smeiposui, lower supramediterranean pluviseasonal oceanic lower subhumid; smeiposus, lower supramediterranean pluviseasonal oceanic upper subhumid; smeipohui, lower supramediterranean pluviseasonal oceanic lower humid; smeipohus, lower supramediterranean pluviseasonal oceanic upper humid; smesposus, upper supramediterranean pluviseasonal oceanic upper subhumid; smespohui, upper supramediterranean pluviseasonal oceanic lower humid; smespohus, upper supramediterranean

pluviseasonal oceanic upper humid; mtesohus, upper mesotemperate oceanic upper humid; steiosus, lower supratemperate oceanic upper subhumid; steiohui, lower supratemperate oceanic lower humid; steiohus, lower supratemperate oceanic upper humid; steiohhi, lower supratemperate oceanic lower hyperhumid; stesohui, upper supratemperate oceanic lower humid; stesohus, upper supratemperate oceanic upper humid; stesohhi, upper supratemperate oceanic lower hyperhumid; stesohhs, upper supratemperate oceanic upper hyperhumid; oteiohhi, lower orotemperate oceanic lower hyperhumid; oteiohhs, lower orotemperate oceanic upper hyperhumid; otesohhi, upper orotemperate oceanic lower hyperhumid; otesohhs, upper orotemperate oceanic upper hyperhumid; otesouhu, upper orotemperate oceanic ultrahyperhumid; cteiouhu, lower cryorotemperate oceanic ultrahyperhumid.