Patterns in Species Diversity during Succession of Coastal Dunes

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<ul><li><p>BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, researchlibraries, and research funders in the common goal of maximizing access to critical research.</p><p>Patterns in Species Diversity during Succession of Coastal DunesAuthor(s): Maike IsermannSource: Journal of Coastal Research, 27(4):661-671. 2011.Published By: Coastal Education and Research FoundationDOI: http://dx.doi.org/10.2112/JCOASTRES-D-09-00040.1URL: http://www.bioone.org/doi/full/10.2112/JCOASTRES-D-09-00040.1</p><p>BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, andenvironmental sciences. BioOne provides a sustainable online platform for over 170 journals and books publishedby nonprofit societies, associations, museums, institutions, and presses.</p><p>Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance ofBioOnes Terms of Use, available at www.bioone.org/page/terms_of_use.</p><p>Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiriesor rights and permissions requests should be directed to the individual publisher as copyright holder.</p><p>http://dx.doi.org/10.2112/JCOASTRES-D-09-00040.1http://www.bioone.org/doi/full/10.2112/JCOASTRES-D-09-00040.1http://www.bioone.orghttp://www.bioone.org/page/terms_of_use</p></li><li><p>www.cerf-jcr.org</p><p>Patterns in Species Diversity during Succession ofCoastal Dunes</p><p>Maike Isermann</p><p>Vegetation Ecology and Conservation BiologyBremen UniversityLeobener Strasse, 28359 Bremen, Germanymaike.isermann@uni-bremen.de</p><p>ABSTRACT</p><p>ISERMANN, M., 2011. Patterns in species diversity during succession of coastal dunes. Journal of Coastal Research,27(4), 661671. West Palm Beach (Florida), ISSN 0749-0208.</p><p>The humped-back relationship in species diversity during succession was tested using vegetation in a coastal sand dunesystem of the German Wadden Sea island of Spiekeroog. Permanent plots were studied over 15 years along a spatialchronosequence from young grey dunes to old brown dunes. Species diversity, succession rate, and environmentalindicator value were used to evaluate multitemporal dynamics of the ecosystem. Long-term development of the dunevegetation was reflected along the chronosequence, whereas fluctuations of plant communities were analyzed by short-term changes of each permanent plot.</p><p>The study confirmed the intermediate stress theory, whereas highest species diversity was reached at the transitionzone of the environmental gradients. Total species richness showed humped-back relations along the xerosere. Hotspotsin species diversity varied with the life form group. Highest richness of herbaceous plants was reached in semidynamicyoung grey dunes, whereas highest richness of bryophytes and lichens shifted due to competition effects to the driestparts of the dune gradient in older successional stages.</p><p>Moreover, the study confirmed the biodiversity-stability theory, with highest ecosystem stability at highest diversity.More stable environments showed lower succession rates than dynamic, disturbed environments. Thus, duringsecondary succession with probably repeated disturbance, the succession rate was higher and no clear direction ofvegetation development was found in comparison to primary succession. The succession rate in a primary seriesrepresented a unimodal relation with total species richness. Thus, species-poor vegetation often dominated by onespecies, such as heathlands, as well as species-rich vegetation, showed lowest succession rates. These communitiesprobably are more stable due to a balanced species combination represented by higher evenness.</p><p>ADDITIONAL INDEX WORDS: Chronosequence, fluctuation, permanent plot, succession rate, time series, vegetationdynamics.</p><p>INTRODUCTION</p><p>Coastal dunes are one of the most vulnerable landscapes in</p><p>northwest Europe and include priority habitats, considering</p><p>the European Union Habitats and Species Directive. For</p><p>example, habitats with open, short, dry grasslands at the</p><p>mainland are often threatened due to agricultural use.</p><p>Furthermore, many coastal dune habitats contain rare species</p><p>and are species rich (Doody, 2001). In general, species diversity</p><p>depends on different ecological features like plant productivity</p><p>(Rosenzweig, 1995), which is often correlated with environ-</p><p>mental factors like soil pH (Isermann, 2005) and scale</p><p>dependent (Auerbach and Shmida, 1987). Relationships among</p><p>the changes of species diversity in the course of ecological</p><p>succession are different. General models of ecological succes-</p><p>sion predict an increase of species diversity with increasing age</p><p>(Odum, 1971).</p><p>Vegetation succession is affected by external and internal</p><p>factors (Bakker et al., 1996). External effects, like atmo-</p><p>spherically nutrient deposition, often give rise to various</p><p>internal developments, such as soil acidification. Vegetation</p><p>composition is also affected by various internal mechanisms,</p><p>like altered competition interactions, and shows a feedback</p><p>mechanism by the vegetation itself (Bakker et al., 1996).</p><p>Vegetation development is controlled by processes, which often</p><p>differ during primary and secondary succession (Austin, 1981).</p><p>Most sand dunes are spatial sequences representing chron-</p><p>ological series (Salisbury, 1952), because the spatial series of</p><p>dune ridges from the sea inland developed one after another. In</p><p>general, these chronosequences describe the formation and</p><p>development of vegetation and environmental factors of the</p><p>dunes (Cowles, 1899; Ranwell, 1960). Mechanisms of direc-</p><p>tional changes in species composition are governed by abiotic</p><p>factors; species interactions or spread of dominant plant</p><p>species retrospectively affects abiotic conditions. Long-term</p><p>vegetation changes in dunes are especially linked with the</p><p>development of the soil (Salisbury, 1925). Strong relationships</p><p>between plant communities and soil parameters, especially the</p><p>C:N ratio and soil pH, were shown, e.g., along a dune zonation</p><p>DOI: 10.2112/JCOASTRES-D-09-00040.1 received 12 April 2009;accepted in revision 2 December 2009.</p><p> Coastal Education &amp; Research Foundation 2011</p><p>Journal of Coastal Research 27 4 661671 West Palm Beach, Florida July 2011</p></li><li><p>in Denmark (Frederiksen et al., 2006). Mechanisms determin-</p><p>ing dune plant patterns appear at both the individual and the</p><p>community level (Feagin et al., 2005), e.g., in changes of species</p><p>abundance and species composition of the plant community.</p><p>In view of their patterns of development, dunes are</p><p>particularly suitable for the study of the relationship between</p><p>succession and zonation (Johnson, 1997; Lichter, 1998).</p><p>Successional dynamics in vegetation have mostly been eval-</p><p>uated by using permanent plots and indirectly by using</p><p>chronosequence studies of the vegetation zonation (Foster</p><p>and Tilman, 2000). Investigations of chronosequences can</p><p>expose regional-scale successional trends due to changes of</p><p>vegetation and environment (Bakker et al., 1996); permanent</p><p>plots, on the other hand, can reveal changes on a local scale.</p><p>Nevertheless, directional vegetation change in dunes can be</p><p>overlaid by seasonal fluctuations, which are determined, e.g.,</p><p>by variation in precipitation and groundwater (Van Der</p><p>Maarel, 1978, 1981), wind disturbance, and associated sand</p><p>erosion and accumulation (Martnez, Vazquez, and Sanchez,</p><p>2001). Therefore, it is a methodological challenge to distinguish</p><p>between fluctuation and succession in dune vegetation using a</p><p>multitemporal approach.</p><p>The present study evaluates changes in plant diversity</p><p>during the past 15 years in dune vegetation influenced by</p><p>natural succession. The main scope of the study was to analyze</p><p>species diversity in relation to succession. Questions addressed</p><p>by this study are as follows: (1) Does species diversity of coastal</p><p>dune vegetation change in relation to succession in a humped-</p><p>back (&gt;) manner? (2) Does the chronosequence approach reflect</p><p>the time-related vegetation development? (3) Does a relation-</p><p>ship exist between succession rate and species diversity, and</p><p>are species-rich communities more stable? and (4) Do species of</p><p>later successional stages change in cover abundance strength</p><p>compared with those from earlier stages?</p><p>METHODS</p><p>Study Area</p><p>The study area was located on the German Wadden Sea</p><p>island of Spiekeroog (Figure 1). The area is protected as part of</p><p>the Wadden Sea National Park (intermediate protection zone).</p><p>The island can be divided in distinct areas of different age</p><p>(Figure 1). The oldest part originates from around AD 1650,</p><p>and the eastern part has developed since AD 1960 (Gerlach,</p><p>Albers, and Broedlin, 1994). Foredunes on Spiekeroog are due</p><p>to continuing sand dynamics up to 20 years old, the main yellow</p><p>dune ridges are 45 to 70 years old, the grey dunes are 70 to</p><p>170 years old, and the brown dunes are up to 270 years old</p><p>(Gerlach, Albers, and Broedlin, 1994). The study area was</p><p>composed of a dune chronosequence in the older, western part</p><p>of the island, and plot ages were estimated according to</p><p>Sindowski (1970).</p><p>The dry dune chronosequence, the xeroseries, is character-</p><p>ized by a typical vegetation zonation. On the beach driftline,</p><p>vegetation such as the Salsolo-Cakiletum maritimae occurs.</p><p>The xeroseries started with low embryonic dunes grown by the</p><p>Figure 1. The island Spiekeroog, the location of the permanent plots (Niedersachsisches Landesamt Fur Okologie, 1993), and the development of the dune</p><p>areas on the island (Gerlach, Albers, and Broedlin, 1994; according to Sindowski, 1970). A line represents the location of the chronosequence along which the</p><p>permanent plots were located. Plains (white) in the south are saltmarhes, in the centre reflect the village, and in the eastern part the white plains reflect</p><p>dunes in the north and salt marshes in the south. The geographic coordinates are for plot 1 (53u46933.80 N, 007u42948.40 E), plot 2 (53u46932.40 N, 007u42952.20E), plot 3 (53u46922.60 N, 007u42930.40 E), plot 4 (53u46927.20 N, 007u42934.90 E), plot 5 (53u46922.60 N; 007u42930.40 E), plot 6 (53u46920.40 N, 007u42948.70 E),plot 7 (53u46912.50 N, 007u43901.20 E), plot 8 (53u46918.70 N, 007u43901.80 E), plot 9 (53u46923.00 N, 007u42930.60 E), plot 10 (53u46907.00 N, 007u42957.50 E), andplot 11 (53u46906.60 N, 007u42956.70 E).</p><p>662 Isermann</p><p>Journal of Coastal Research, Vol. 27, No. 4, 2011</p></li><li><p>Honckenyo-Agropyretum juncei. In the case of sand accumula-</p><p>tion, dunes rise to higher yellow dunes, typically covered by the</p><p>Elymo-Ammophiletum and characterized by sparse vegetation</p><p>and a raw soil more or less without organic matter. With lesser</p><p>sand accumulation, shrublands like the Hippophao-Sambuce-</p><p>tum establish on the landwards slopes. Increased sand</p><p>stabilization, continued leaching out of nutrients by precipita-</p><p>tion, and increased vegetation cover support the origin of soil</p><p>organic matter, so that grey dunes develop. Grey dunes in</p><p>relation to a decreasing gradient of sand accumulation and in</p><p>relation to soil development, e.g., expressed as a decreasing soil</p><p>pH, are covered by plant communities like the Phleo-Tortule-</p><p>tum ruraliformis, the Festuco-Galietum veri, and the lichen-</p><p>and bryophyte-rich Violo-Corynephoretum. These grey dune</p><p>communities often contain many rare species and occur in less</p><p>disturbed conditions more often on the islands than on the</p><p>mainland, so they are highly valuable in the sense of nature</p><p>conservation. The following brown dunes with low soil pH and</p><p>high organic matter content are characterized, on the one</p><p>hand, by short, dense grasslands like the Carex arenaria</p><p>[Koelerio-Corynephoretea] community and, on the other hand,</p><p>by heathlands, which on Spiekeroog are represented by the</p><p>Carici arenariae-Empetretum. The oldest dune parts are</p><p>grown by dune woodlands, including Betula pubescens, Pinus</p><p>silvestris, Populus tremula, Quercus robur, and since about</p><p>10 years ago, Fagus sylvatica.</p><p>Dunes are in general characterized by sand dynamic, which</p><p>supports small-scale vegetation mosaics and younger vegeta-</p><p>tion stagesespecially in grey dunes. Therefore, natural and</p><p>human-induced disturbance plays an important role. The</p><p>dunes on Spiekeroog were grazed by cattle and sheep until</p><p>about 1900; rabbits have been eradicated since 1880 (Meyer-</p><p>Deepen and Meijering, 1970), only hares and pheasants with</p><p>lower scrabbling activities occur. Many parts of the outer dunes</p><p>are stabilized by planting of marram grass; thus, higher sand</p><p>accumulation into the following dunes is more or less stopped.</p><p>Only beach and foredunes show higher sand dynamic,</p><p>particularly due to recreation activities. During the past</p><p>15 years, disturbance in the inner dunes was low, including</p><p>human impacts, e.g., due to recreation activities. Establish-</p><p>ment of the national park and general enhanced public</p><p>environmental awareness, combined with increased respon-</p><p>siveness of global change, e.g., the importance of dunes in</p><p>relation to sea-level rise, support the decline in human dune</p><p>disturbance.</p><p>During the last century, land use changed and in the</p><p>following dunes developed to be more fixed and without an</p><p>appreciable amount of open sandy areas (Meyer-Deepen and</p><p>Meijering, 1970). Due to changes in land use, dunes in the</p><p>North Sea area are, since the middle of the last century,</p><p>characterized by an increase in various scrub vegetation, e.g.,</p><p>native shrubs such as Crataegus monogyna, Hippophae</p><p>rhamnoides, and Ligustrum vulgare and nonnative ones like</p><p>Rosa rugosa (Isermann and Cordes, 1992; Van Der Laan,</p><p>1985). The development towards older successional stages on</p><p>Spiekeroog was already visible around 1950 (Wiemann and</p><p>Domke, 1959). Further changes of the dune vegetation were</p><p>analyzed in 1990 on the landscape scale using vegetation maps</p><p>(Isermann and Cordes, 1992), and recent changes were studied</p><p>on a smaller scale with permanent plots.</p><p>Sampling</p><p>Along a transect from (young) grey to (old) brown dunes, 11</p><p>permanent plots (Figure 1), placed in typical plant commu-</p><p>nities, were established in 1990. In comparison to strictly</p><p>random sampling design (Frederiksen et al., 2006), the</p><p>permanent plots were established in typical plant commu-</p><p>nities, initially with plots containing only one plant community</p><p>instead of a possible mixture of different communities in one</p><p>plot. Moreover, this sampling design was used because a long-</p><p>term development was of primary interest instead of a short-</p><p>term competition approach between two plant species. Along</p><p>the chronosequence, vegetation changes with indirect and</p><p>direct methods were compared. Moreover, vegetation changes</p><p>were compared on large and small spatial scales, as well as</p><p>considered on different temporal scales, and time-intensive</p><p>vegetation mapping (Isermann and Cordes, 1992) and perma-</p><p>nent plots were combined.</p><p>Permanent plots were recorded to detect long-time vegeta-</p><p>tion changes. Because of sand mobility, it was not possible to set</p><p>up plots in dunes more seawards. Plots, 1 m2 in size, were</p><p>marked with a wooden pe...</p></li></ul>