Endemic Sand Dune Vegetation of the Northwest Iberian Peninsula

Journal of Coastal Research

24

2B

113–121

West Palm Beach, Florida

March 2008

Endemic Sand Dune Vegetation of the Northwest Iberian Peninsula: Diversity, Dynamics, and Significance for Bioindication and Monitoring of Coastal Landscapes Angela Lomba†, Paulo Alves‡, and Joaõ Honrado§ CIBIO (Centro de Investigaçaõ em Biodiversidade e Recursos Gene´ticos) Universidade do Porto Rua do Campo Alegre, 1191 4150-181 Porto, Portugal [email protected]

†

CIBIO (Centro de Investigaçaõ em Biodiversidade e Recursos Gene´ticos) Universidade do Porto Rua do Campo Alegre, 1191 4150-181 Porto, Portugal [email protected]

‡

CIBIO and Faculdade de Cieˆncias Universidade do Porto Rua do Campo Alegre, 1191 4150-181 Porto, Portugal

§

ABSTRACT LOMBA, A.; ALVES, P., and HONRADO, J., 2008. Endemic sand dune vegetation of the northwest Iberian peninsula: diversity, dynamics, and significance for bioindication and monitoring of coastal landscapes. Journal of Coastal Research, 24(2B), 113–121. West Palm Beach (Florida), ISSN 0749-0208. Coastal areas are sensitive systems suffering both natural and anthropic pressures. Specifically, coastal sand dune dynamics is related with observable modifications in plant communities, and this relationship is being pointed out in recent years as a monitoring tool in littoral areas. Plant community types, with a relatively stable floristic composition related to specific ecologic conditions (‘‘plant associations’’), provide a suitable tool for bioindication within monitoring processes and in the management of littoral areas. In this regard, recent bio-geologic studies performed in dune systems of Southwest Europe allowed the identification of a number of specific bioindicators for both mobile and interior dunes. In Northwest Iberian Peninsula, sand dune vegetation is distinguished by its transitional character between typical Atlantic and Mediterranean vegetation types, and its originality is still enhanced by the occurrence of narrow endemic species and by the fact that most vegetation types are endemic to the territory. The organisation of these community types within dune systems is strongly determined by specific dynamic processes mediated by both natural and anthropic disturbances, so they present a large potential for bioindication of coastal dynamics and conservation status. In this paper, the most significant ecologic, floristic and biogeographic characters of sand dune vegetation in Northwest Iberian Peninsula are discussed with the purpose of demonstrating the usefulness of well-defined vegetation types for bioindication within the context of both short- and long-term monitoring of coastal sand dune systems. ADDITIONAL INDEX WORDS: Coastal sand dunes, ecologic indicators, monitoring, plant communities.

INTRODUCTION Coastal areas are sensitive systems suffering several natural and anthropic pressures. Natural cyclic dynamics (e.g., sea level changes, geomorphologic modifications, climate features, sedimentary budget, and neotectonics) are known by their ability to induce dramatic changes in geoforms (FAVENNEC, 2002; GRANJA et al., 2000; SOARES DE CARVALHO et al., 2002). In the case of anthropic disturbance factors on coastal landscapes, they range from urban expansion to seasonal tourism exploitation (e.g., ARAU´JO et al., 2002; KUTIEL, ZHEVELEV, and HARRISON, 1999; SOARES DE CARVALHO et al., 2002). Coastal dynamics include the occurrence of both regression phases (inland beach migration and erosion) characterized by the disruption of littoral landforms and accretion phases with positive sedimentary budget. These natural changes in dune systems are related to observable modifications in coastal plant communities; in fact, because most community types are related to specific coastal geoforms, this relationship has DOI: 10.2112/05-0610.1 received 7 November 2005; accepted in revision 10 July 2006.

been pointed to in recent years as a monitoring tool in dune areas (e.g., ARAU´JO et al., 2002; LOMBA et al., 2005a). Phytosociologic plant community types (plant associations) are well-defined entities with a relatively stable floristic composition related to specific biotopes (i.e., plant associations are specific to determined environmental conditions) within a given (bio)geographical context (GE´HU and RIVAS-MARTIŃEZ, 1981; KENT and COKER, 1992). So, within the framework of bioindication in the assessment of coastal dynamics, plant associations provide a suitable tool for researchers/technicians to use in monitoring processes (LOIDI, 1994), in the establishment of science-based evolution scenarios, and, ultimately, in the management of littoral areas. In this paper, the most significant ecologic, floristic, and biogeographic characters of sand dune vegetation in the northwest Iberian peninsula are discussed within the framework of bioindication in coastal areas. Main vegetation types, most of which are narrowly endemic, are described, with particular emphasis on still unreported community types. The advantage of the use of well-defined vegetation types for bioindication is also discussed within the context of both short- and long-term monitoring of coastal sand dune systems.

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RIVAS-MARTIŃEZ et al. (2002) for upper hierarchical levels (from classes to suballiances), of sand dune vegetation in the study area is presented in the Appendix. Nomenclature of plant taxa throughout the text follows standard Iberian floras (C ASTROVIEJO et al., 1986–2003; FRANCO, 1971, 1984; FRANCO and AFONSO, 1994, 1998, 2003), except in the case of Artemisia crithmifolia L. and Corynephorus canescens (L.) Beauv. var. maritimus Godr. (RIVASMARTIŃEZ et al., 2002).

Numerical Analyses

Figure 1. The study area (coastal zone of the northwest Iberian peninsula).

METHODS Study Area From both climatic and biogeographic points of view, the northwest Iberian coastline (Figure 1) includes the southernmost Atlantic dune system in Europe (CALDAS and HONRADO, 1998; RIVAS-MARTIŃEZ et al., 2002). In this sector, dune systems are usually quite narrow (generally less than 300 m wide), with a close succession of geoforms colonized by a dense mosaic of vegetation types. This shoreline is characterized by its predominantly submediterranean climate with a strong oceanic influence (C ALDAS and HONRADO, 1998; COSTA et al., 1998; HONRADO, ALVES, and CALDAS, 2002), which is reflected by the transitional character of the floristic composition of plant communities that are progressively richer in mediterranean elements toward the south. The richness of its flora and vegetation, characterized by a mixture of Atlantic and Mediterranean taxa and by the occurrence of a number of narrow endemics, gives this shoreline a remarkable value for conservation, recognized with a number of national (both Portuguese and Spanish) and international (e.g., European Union ‘‘Natura 2000’’) protected areas.

Numerical analyses were used to address the syntaxonomic validity of new vegetation types. Portuguese and Spanish rele´ve´s (i.e., vegetation samples) were compiled in a global data matrix, containing abundance indexes for the floristic elements within each rele´ve´. This data matrix was used to perform several complementary statistical analyses, including ordination methods and cluster analysis. Numerical classification, or cluster analysis, consists in grouping the vegetation samples into classes on the basis of their attributes—in this case, floristic composition (K ENT and COKER, 1992). Within cluster analysis, hierarchical methods, particularly agglomerative analysis according to Ward’s method, have been mentioned as a suitable approach in the analysis of plant communities (CAPELO, 2003). Hierarchical cluster analyses, according to Ward’s method (with Euclidean distance as the similarity measure), were performed with the Community Analysis Package 3.1威 (Pisces Conservation) software. Indirect ordination techniques consist of the relative arrangement of vegetation samples according to their similarity in terms of floristic composition (K ENT and COKER, 1992). Ordination analyses were performed with CANOCO 4.5威 for Windows (TER BRAAK and SMILAUER, 2002). A detrended correspondence analysis (DCA) was first performed to determine the length of the gradient within the dataset and then decide about the ordination method to use. Given the length of the gradient (⬎4 SD; VAN DEN BRINK, VAN DEN BRINK, and TER BRAAK, 2003) and the focus of this analysis on the compositional differences of samples/rele´ve´s, a unimodal response was assumed; therefore, a correspondence analysis (CA) was performed (TER BRAAK and SMILAUER, 2002; VAN DEN BRINK, VAN DEN BRINK, and TER BRAAK, 2003).

RESULTS AND DISCUSSION

Phytosociologic Data Phytosociologic data for sand dune vegetation in the northwest Iberian peninsula were collected from both Spanish (IZCO, GUITIAN, and GUITIAN, 1988; RODRI´GUEZ-OUBINÃ, ORTIZ, and PULGAR, 1998) and Portuguese (CALDAS, HONRADO, and PAIVA, 1999; HONRADO et al., 2004) coastal areas. Most data on coastal vegetation from this area have been collected following the concepts and methods of phytosociology (GE´HU and RIVAS-MARTIŃEZ, 1981; KENT and COKER, 1992; RIVAS-MARTIŃEZ, 2002), and so classified vegetation types (plant associations) are available for most coastal habitats (e.g., CALDAS and HONRADO, 1998; HONRADO, ALVES, and CALDAS, 2002). A full syntaxonomic checklist, following

An Overview of Sand Dune Vegetation in Northwest Iberian Peninsula Coastal dune systems are characterized by the existence of a complex environmental gradient related to the distance to the ocean. From the coastline inward, soil (sand) stability gradually increases and salt influence decreases, which reflect on the plant species and communities that colonize different areas of a dune system (Figure 2 and Table 1). Two major dune types can be distinguished within dune systems of the northwest Iberian peninsula from both geological and biological points of view: mobile dunes (embryonic foredunes and foredunes) and interior dunes (relatively stable dunes or

Journal of Coastal Research, Vol. 24, No. 2B (Supplement), 2008

Bioindication and Monitoring of Coastal Landscapes

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Figure 2. Schematic representation of the habitat sequence within a coastal sand dune system in the northwest Iberian peninsula.

grey dunes), with mobile dunes located closer to the sea under a stronger influence of both strong winds and salt spray.

Vegetation of Mobile Dunes Mobile dunes (including both embryonic foredunes and foredunes) in the northwest Iberian peninsula support a significant diversity of vegetation types, ranging from perennial grasslands to ephemeral communities of therophytes. Annual drift vegetation (class Cakiletea maritimae: association Honckenyo–Euphorbietum peplis) includes halonitrophilous pioneer communities dominated by Honckenya peploides and Cakile maritima subsp. integrifolia that can be found both in the foreshore and backshore and on embryonic dunes. However, the typical embryonic dune grasslands (class Ammophiletea: Euphorbio paraliae–Agropyretum junceiformis) are dominated by the rhizomatous perennial grass sand-couch (Elymus farctus subsp. boreali-atlanticus) and include a few other specialized taxa like Euphorbia paralias, Eryngium maritimum, and Calystegia soldanella. On the contrary, perennial grasslands (class Ammophiletea: Otantho–Ammophiletum australis) of foredune tops are typically dominated by marram (Ammophila arenaria) and include a number of other taxa, with Medicago marina, Otanthus maritimus, Eryngium maritimum, and Calystegia soldanella being the most common. In both embryonic foredunes and foredunes, annual grasslands of class Tuberarietea guttatae (association Violo–Silenetum littoreae) can be found in early spring; they are species-poor formations dominated by Silene littorea and characterized by the occurrence of the narrow endemic Viola kitaibeliana var. henriquesii.

Vegetation of Grey Dunes (Interior Dunes) Relatively stable dunes (⫽secondary or grey dunes) are characterized by both higher sand stability and lower influence of salt spray because of a gradually increasing distance from the sea. Because of its transitional character and the occurrence of endemic taxa, most vegetation types in grey dunes of the northwest Iberian peninsula are endemic to the territory. Low shrublands of association Iberidetum procumbentis (class Ammophiletea) are a northwest Iberian endemic vegetation type dominated by Artemisia crithmifolia, Crucianella maritima, and Helichrysum italicum subsp. picardi and char-

acterized by the presence of the Portuguese endemic Jasione maritima var. sabularia (⫽Jasione lusitanica). Annual oligotrophic grasslands (class Tuberarietea: Polycarpo–Evacetum ramosissimi), also endemic, occur in open spaces between shrubs and are dominated by Evax pygmaea subsp. ramosissima, Xolantha guttata, and Polycarpum tetraphyllum subsp. diphyllum. Seasonally flooded slacks of grey dune depressions are typically colonized by dense, species-poor rush beds (class Molinio–Arrhenatheretea: association Holoschoeno–Juncetum acuti) dominated by Scirpoides holoschoenus and Agrostis stolonifera var. pseudopungens. In disturbed dunes, this vegetation mosaic is replaced by subnitrophilous vegetation of association Scrophulario frutescentis–Vulpietum alopecuroris (class Stellarietea mediae), a species-rich community type dominated by the Mediterranean annual grass Vulpia alopecuros. These formations colonize trampled areas in grey dunes, on which they tend to replace both the perennial and annual nonnitrophilous vegetation because of soil nitrification. Perennial acidophilous grasslands of class Koelerio–Corynephoretea are another vegetation type colonizing grey dunes. Specifically, they colonize decalcified sands in the most interior parts of coastal dune systems, and they are typically dominated by the caespitose grass Corynephorus canescens var. maritimus (RODWELL, 2000). RODRI´GUEZ-OUBINÃ, ORTIZ, and PULGAR (1998) described a northwest Iberian endemic association of perennial sand dune grasslands (Linario polygalifoliae–Corynephoretum canescentis), characterised by the dominance of Corynephorus canescens (var. maritimus), Sedum album, Sedum acre, and Linaria caesia subsp. decumbens. Although RODRI´GUEZ-OUBINÃ, ORTIZ, and PULGAR (1998) indicated Linario-Corynephoretum for all dune systems in the northwest Iberian peninsula, the fact is that Portuguese communities present some important differences, such as the presence of the national endemics Jasione maritima var. sabularia and Coincya johnstonii (Table 2), as well as the occurrence of Mediterranean differential taxa like Malcolmia littorea, Centaurea sphaerocephala subsp. polyacantha, Herniaria ciliolata subsp. robusta, and Paronychia argentea. The biogeographic character of these floristic differences justifies the recognition of a new southern vicarious association (Jasiono sabulariae–Corynephoretum maritimi ass. nova hoc loco; syntype: Table 2, rele´ve´ 12) to segregate Portuguese communities. Statistical analyses were performed to validate


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Table 1. Synthetic table of vegetation types and their ecologic position within sand dune systems in the northwest Iberian peninsula (the names of all taxa are indicated in the binomial form). Position

Mobile dunes (embryonic foredunes and foredunes)

Grey dunes

Vegetation Type

Plant Association

Annual drift vegetation

Honckenyo-Euphorbietum peplis

Embryonic dune perennial grasslands

Euphorbio paraliae-Agropyretum junceiformis

Foredune perennial grasslands

Otantho-Ammophiletum australis

Annual grasslands

Violo-Silenetum littoreae

Low shrublands

Iberidetum procumbentis

Annual oligotrophic grasslands

Polycarpo-Evacetum ramosissimi

Annual subnitrophilous grasslands

Scrophulario-Vulpietum alopecuroris

Rush beds

Holoschoeno-Juncetum acuti

Perennial acidophilous grasslands

Linario polygalifoliae-Corynephoretum canescentis

Jasiono sabulariae-Corynephoretum maritimi

the results from the classical phytosociologic approach. Cluster analysis clearly identified two distinct clusters (Figure 3): one concerning Spanish rele´ve´s (LCOR) and another including the Portuguese samples (JCOR). This result was also obtained from a CA (Figure 4), in which the two previous clusters occupy different areas of the ordination plot.

Vegetation Dynamics and the Establishment of Bioindication Models for the Monitoring of Dune Systems The Use of Plant Species and Communities as Bioindicators The introduction of concepts like ‘‘bioindicator’’ resulted from the recognition that living organisms show sensitive responses to environmental conditions and changes. On the basis of the early scientific work of H ILGARD, CLEMENTS (1928 in ISERENTANT and SLOOVER, 1976) wrote a treaty on ‘‘vegetal indicators,’’ in which he described the concept from the recognition that plant species and communities showed structural or physiologic variation when submitted to environmental variation (e.g., light, humidity, and temperature). More recently, BU¨CHS (2003) extensively revised both the concepts and pertinent literature concerning biotic indicators.

Indicator Species

Honckenya peploides Cakile integrifolia Elymus boreali-atlanticus Euphorbia paralias Eryngium maritimum Calystegia soldanella Ammophila arenaria Medicago marina Otanthus maritimus Eryngium maritimum Silene littorea Viola henriquesii Pseudorlaya minuscula Cerastium diffusum Artemisia crithmifolia Crucianella maritima Helichrysum picardii Jasione sabularia Evax ramosissima Xolantha guttata Polycarpon diphyllum Paronychia argentea Vulpia alopecuros Lagurus ovatus Scrophularia frutescens Scirpoides holoschoenus Juncus acutus Corynephorus canescens (var. maritimus) Sedum album Sedum acre Linaria decumbens Corynephorus canescens (var. maritimus) Jasione sabularia Coincya johnstonii

Even though the term ‘‘bioindicator’’ is still mostly used for individual species, this concept fits particularly well with plant communities (ARAU´JO et al., 2002; ISERENTANT and SLOOVER, 1976; LOIDI, 1994) because their floristic composition is closely related to specific ecologic conditions within a given geographic circumscription. In fact, other early authors like CHAMBERLIN (1877 in ISERENTANT and SLOOVER, 1976) had already stressed that plant communities are more accurate bioindicators of environmental conditions than individual species because they are usually defined by a combination of character species that require specific environmental conditions to coexist. To address the usefulness of plant communities for bioindication, a solid classification of community types is obviously required. The phytosociologic classification of community types as plant associations within a hierarchical system is based on the presence of a group of characteristic species related to specific environmental/ecologic conditions (G E´HU and RIVAS-MARTIŃEZ, 1981; KENT and COKER, 1992). This floristic-ecologic equivalence is particularly visible in areas submitted to severe environmental conditions (e.g., coastal habitats) in which plant communities can be considered highly reliable indicators for both short- and long-term monitoring



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Figure 3. Cluster diagram demonstrating a clear floristic segregation between Portuguese (JCOR) and Spanish (LCOR) releve´s (Ward’s method, Euclidean distance).

of environmental changes (ARAU´JO et al., 2002; GAINES, HARROD, and LEHMKUHL, 1999; LOMBA et al., 2005a).

Bioindication by Plant Communities in Coastal Areas: Examples from the Northwest Iberian Peninsula The possibility of using plant communities/vegetation in landscape evaluation and land management has been addressed by several authors, and recent studies have stressed the necessity of performing integrated research (ARAU´JO et al., 2002; FAVENNEC, 2002; LOIDI, 1994; LOMBA et al., 2005a,b). In the case of coastal areas, recent studies have reported the use of landforms and related plant communities as indicators of their conservation status, including the discrimination of stability and instability situations (e.g., ARAU´JO et al., 2002; BUSH et al., 1999). This close relationship between coastal geoforms and certain plant community types allows researchers and trained technicians to perform in situ evaluations of the conservation status and even to conjecture

about putative scenarios of coastal evolution within the framework of long-term monitoring. Most indicators of coastal conservation reported in previous studies are related to the presence/absence of specific vegetation types (e.g., GRANJA et al., 2000; LOMBA et al., 2005a,b), to the abundance of species and character species in each vegetation type, and to the occurrence of vegetation types in secondary (⫽atypical) positions within the dune system (e.g., ARAU´JO et al., 2002; GRANJA et al., 2000; LOMBA et al., 2005a,b). Integrated biogeologic studies performed in dune systems of southwestern Europe (HONRADO, ALVES, and CALDAS, 2002; LOMBA et al., 2005a,b) allowed the identification of an array of specific indicators for both mobile and grey dunes, as described in the next paragraphs. Embryonic foredunes are landforms strongly related to beach dynamics that can be considered efficient geoindicators of recent coastal evolution (BUSH et al., 1999; FAVENNEC, 2002). Considering the contact between the beach and the dune system, several situations can be identified: (i) absence of embryonic foredunes (regression phases), (ii) presence of


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Table 2. Phytosociologic table of Jasiono sabulariae-Corynephoretum maritimi ass. nova (the names of all taxa are indicated in the binomial form). Rele´ve´ no.* Area (m2) Altitude (m) No. of taxa Releve´ code (numerical analyses)

1 9 ⬍5 8

2 9 ⬍5 8

3 16 ⬍5 9

4 16 ⬍5 9

5 9 ⬍5 9

6 9 ⬍5 10

7 25 ⬍5 11

8 9 ⬍5 11

9 9 ⬍5 11

10 9 ⬍5 12

11 25 ⬍5 14

12 9 ⬍5 14

13 9 ⬍5 15

14 9 ⬍5 17

JCOR6 JCOR11 JCOR12 JCOR3 JCOR5 JCOR2 JCOR13 JCOR4 JCOR8 JCOR9 JCOR14 JCOR1 JCOR10 JCOR7

Characteristic and differential taxa Corynephorous maritimus Jasione sabularia Carex arenaria Malcolmia littorea Linaria decumbens Paronychia argentea Herniaria robusta Sedum acre Anthyllis iberica Centaurea polyacantha Silene niceensis Coincya johnstonii Sedum album Sesamoides purpurascens

3 2

⫹

3 1 ⫹ 1 ⫹

3 2

4 3

1

⫹ ⫹ 2

3

4 2

4 2 2 ⫹

3 2 1 ⫹

3 2

4 2 2

3 3 2 1

1 1

1

1 2 1 ⫹

3 3 1

1

2

1

⫹

⫹

3 1

3 3 ⫹

1

2

2 3

⫹

1 1

1

3 1 ⫹ 1 1 1 ⫹ 1 1

2 1

1 2

Companion taxa Plantago coronopus Vulpia alopecuros Silene portensis Evax ramosissima Lagurus ovatus Leontodon taraxacoides Erodium bipinnatum Xolantha guttata Hypochoeris glabra Hypochoeris radicata Lupinus angustifolius Ammophila arundinacea Corrigiola litoralis Silene littorea Aira praecox Anagallis microphylla Briza maxima Calystegia soldanella Cerastium diffusum Echium rosulatum Euphorbia portlandica Euphorbia terracina Linaria spartea Mibora minima Ornithopus pinnatus Pancratium maritimum Rumex angiocarpus Scrophularia frutescens Sedum brevifolium Sedum sediforme Silene scabriflora Tolpis barbata Trifolium scabrum

⫹ ⫹

1 2

⫹

1 2 1

⫹ ⫹

1 1

1

⫹ 1

1

1 1 1 1 2 1 1

2 2 ⫹

1 1 1

2 1 1 1

1

1 2

1

1

1 1 1 2

⫹ 2

⫹ 1

1 1 1 ⫹

⫹ ⫹ ⫹

1 ⫹ ⫹

1

1

⫹

⫹

⫹

⫹

⫹ 1

⫹ 1

⫹ ⫹

⫹

⫹

⫹ 1

⫹ 1 2

⫹ 1

⫹ ⫹

⫹ ⫹

* Sites (northwest Portugal): Releve´s 1 and 14—Matosinhos. Releve´s 2, 5, 8, 9, 10, and 13—Ovar: Furadouro. Releve´s 3, 7, and 11—Viana do Castelo: Rodanho. Releve´s 4, 6, and 12—Vila do Conde: Mindelo.

embryonic foredunes (accretion phases), and (iii) accretion vs. regression phases. Cases of absence of embryonic foredunes are characteristic of coastal areas under continuous erosion phenomena and can be recognized according to both geomorphologic (contact between beach and dune system is by sand cliffs) and phytosociologic (absence of Euphorbio–Agropyretum junceiformis vegetation) features. In the case of stable

embryonic foredunes, a balanced sediment budget produces a gradual and smooth contact between the beach and the dunes, with Euphorbio-Agropyretum communities usually well developed. Situations in which accretion phases alternate with regression periods usually exhibit atypical characteristics, which indicates complex coastline dynamics. Geomorphologic events in mobile dunes (both embryonic



Figure 4. Correspondence analysis (CA) ordination diagram of Portuguese (JCOR) and Spanish (LCOR) releve´s of perennial acidophilous grasslands (class Koelerio-Corynephoretea).

foredunes and foredunes) induce severe changes on the more interior areas of the dune system because mobile dunes provide a defensive physical barrier of interior plant formations regarding severe environmental conditions. In fact, disruptions of mobile dunes promote strong accumulation of mobile sand in interior areas, and this phenomenon has drastic consequences on plant communities of grey dunes, namely (i) the occurrence of vegetation types that are normally typical of embryonic foredunes (Euphorbio–Agropyretum junceiformis) and foredune tops (Otantho–Ammophiletum australis) and (ii) a decrease in the number of character species of both the Iberidetum procumbentis (typical perennial vegetation) and the nonnitrophilous annual communities of grey dunes (Polycarpo-Evacetum), whereas character species of both the Euphorbio-Agropyretum and the annual pioneer vegetation of highly mobile foredune sands (Violo-Silenetum) typically increase. Anthropic influences (e.g., trampling and driving on dunes) act as a complement of natural causes, promoting both the disruption of foredunes and embryonic foredunes and the replacement of Iberidetum procumbentis by the annual nitrophilous formations of class Stellarietea mediae (ARAU´JO et al., 2002).

An Integrated Approach for Short- and Long-Term Monitoring of Dune Systems The biogeomorphologic approach described above clearly stresses that landforms and associated plant communities

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constitute suitable indicators of coastal dynamics and should therefore be used for evaluating and monitoring coastal areas. First, this approach provides the possibility of determining the current conservation status of dune systems from both bio- and geoindicators. This is particularly useful in the case of coastal areas exhibiting natural regressive dynamics (inland beach migration), but some indicators can also be used to address natural and human disturbance in grey dunes. Second, those indicators can also be used for both short- and long-term coastal monitoring because plant communities (both their presence/absence and species composition) can be compared along time periods. Although the model presented here is based on solid scientific grounds (both biological and geological), the assessment of its indicators is simple enough to make it usable by technicians and stakeholders in monitoring programs. Regarding long-term monitoring, this biogeoindication model also provides the potential for developing predictive models for coastal evolution. Long-term monitoring has experienced major advances with the development of Geographical Information Systems (GISs), which have allowed researchers to store and analyze large spatial datasets more effectively (e.g., environmental or vegetation data). In the case of coastal areas, accurate analyses of changes in landforms and vegetation types can be performed through GIS comparison of chronologic sequences of aerial photographs from the same area, which have been proved to be particularly useful in the determination of erosion/accretion phenomena and related indices (KUTIEL et al., 2004; LEVIN and BEN-DOR, 2004). This type of information can also be used in the development of GIS-based models for coastal dynamics, therefore allowing researchers to predict and compare distinct scenarios for the evolution of sand dune systems, which is most useful for optimizing the choice of indicators within monitoring programs.

CONCLUDING REMARKS Sandy coastal areas are highly sensitive systems, strongly influenced by both natural and man-induced geomorphologic dynamics. Natural phenomena are nowadays considered an important factor in inland beach migration (the so-called coastal erosion) and induce significant changes on both geoforms and related plant communities. The integrated biogeomorphologic model described here identifies coastal landforms and specific plant communities as suitable indicators for monitoring coastal areas, providing the possibility of determining the current conservation status of dune systems. Also, the importance of a solid classification of community types for their use in bioindication has been particularly stressed and demonstrated. In this regard, the close relationship between species composition and local ecologic features is particularly useful in areas submitted to severe environmental conditions (e.g., coastal habitats) in which plant communities can be considered highly reliable indicators of environmental changes. Phytocoenotic indicators like presence/ absence of specific vegetation types, abundance of species and


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of character-species in each vegetation type, and occurrence of vegetation types in ‘‘secondary’’ positions have been used to address the conservation status of dune systems. Also, these bioindicators have been shown to be related to specific geomorphic changes (geoindicators), particularly in mobile dunes. The proposed set of bio- and geoindicators can be used by technicians and stakeholders for the purpose of short-term coastal monitoring. Also, this biogeomorphologic model provides a scientific basis for long-term monitoring programs because it provides the potential for constructing predictive models for coastal evolution. In this regard, recent advances in the use of GIS tools allow more accurate analyses of changes in landforms and vegetation types, and in the construction of GIS-based evolution models to predict and compare putative scenarios for coastal dynamics.

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APPENDIX Syntaxonomic Checklist of Sand Dune Vegetation in the Northwest Iberian Peninsula Ammophiletea Br.-Bl. & Tu¨xen ex Westhoff, Dijk, & Passchier 1946 Ammophiletalia Br.-Bl. 1933 Ammophilion australis Br.-Bl. 1921 corr. Rivas-Martıńez, Costa & Izco in Rivas-Martıńez, Lousa˜, T. E. Dıáz, Fernańdez-Gonza´lez, & J.C. Costa 1990 Ammophilenion australis Rivas-Martıńez & Ge´hu in Rivas-Martıńez, Costa, Castroviejo, & E. Valdeˆs 1980 nom. mut. propos. Rivas-Martıńez et al. 2002 Otantho maritimi–Ammophiletum australis Ge´hu & Tu¨xen 1975 corr. Fernańdez Prieto & T.E. Dıáz 1991 Honckenyo peploidis–Elytrigion boreoatlanticae Tu¨xen in Br.-Bl. & Tu¨xen nom. mut. propos. Rivas-Martıńez et al. 2002 Elytrigienion boreoatlanticae Rivas-Martıńez & Ge´hu in Rivas-Martıńez, Costa, Castroviejo, & E. Valdeˆs 1980 nom. mut. propos. Rivas-Martıńez et al. 2002 Euphorbio paraliae–Agropyretum junceiformis Tu¨xen corr. Darimont, Duvigneaud & Lambinon 1962. Crucianelletalia maritimae Sissingh 1974 Helichrysion picardii (Rivas-Martıńez, Costa & Izco in Rivas-Martıńez, Lousa˜, T.E. Dıáz, Fernańdez-

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Gonza´lez, & J.C. Costa 1990) ex Rivas-Martıńez, Fernańdez-Gonza´lez, & Loidi 1999 Iberidetum procumbentis Bellot 1996 Cakiletea maritimae Tu¨xen & Preising in Tu¨xen 1950 Cakiletalia integrifoliae Tu¨xen ex Oberdorfer 1950 corr. Rivas-Martıńez, Costa, & Loidi 1992 Atriplicion littoralis Nordhagen 1940 Honckenyo–Euphorbietum peplis Tu¨xen ex Ge´hu 1964 Koelerio-Corynephoretea Klika in Klika & Nova´k 1941 Corynephoretalia canescentis Klika 1934 Koelerion arenariae Tu¨xen 1937 nom. mut. propos. Rivas-Martıńez et al. 2002 Linario polygalifoliae–Corynephoretum canescentis J. Rodrı´guez, Ortiz, & Pulgar 1988 Jasiono sabulariae–Corynephoretum maritimi A. Lomba, P. Alves, & J. Honrado ass. nova Molinio-Arrhenatheretea Tu¨xen 1937 Holoschoenetalia Br.-Bl. ex Tchou 1948 Molinio–Holoschoenion vulgaris Br.-Bl. ex Tchou 1948 Brizo-Holoschoenenion (Rivas Goday 1964) Rivas-Martıńez in Rivas-Martıńez, Costa, Castroviejo, & E. Valde´s 1980 Holoschoeno–Juncetum acuti Rivas-Martıńez & Costa in Rivas-Martıńez, Costa, Castroviejo, & E. Valde´s 1980 Stellarietea mediae Tu¨xen, Lohmeyer & Preising ex von Rochow 1951 Chenopodio-Stellarienea Rivas Goday 1956 Thero-Brometalia (Rivas Goday & Rivas-Martıńez ex Esteve 1973) O. Bolo`s 1975 Linario polygalifoliae–Vulpion alopecuroris Br.-Bl., Rozeira, & P. Silva in Br.-Bl., G. Br.-Bl., Rozeira, & P. Silva 1972 Scrophulario frutescentis–Vulpietum alopecuroris Br.-Bl., Rozeira, & P. Silva in Br.-Bl., G. Br.Bl., Rozeira, & P. Silva 1972 Tuberarietea guttatae (Br.-Bl. in Br.-Bl., Roussine & Ne`gre 1952) Rivas Goday & Rivas-Martıńez 1963 nom. mut. propos. Rivas-Martıńez et al. 2002 Tuberarietea guttatae Br.-Bl. in Br.-Bl., Molinier & Wagner nom. mut. propos. Rivas-Martıńez et al. 2002 Thero-Airion Tu¨xen & Oberdorfer 1958 Polycarpo diphylli–Evacetum ramosissimae Ortiz, Pulgar, & Rodrı´guez Oubinã 2001 Cutandietalia maritimae Rivas-Martıńez, Dıéz Garretas, & Asensi 2002 Linarion pedunculatae Diez Garretas, Asensi, & Esteve in Diez Garretas 1984 Violo henriquesii–Silenetum littoreae Izco & Guitiań 1988
