PhD Reza Erfanzadeh 2009 - Ghent Ecology - Universiteit Gent

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elationship between soil characteristics and vegetation is stronger in late successional than in early successional stages. 1.3.5 Seed bank and succession 16 Depth distribution of viable seeds is not merely of academic interest (Espinar et al. 2005). Indeed, for some restoration measures the knowledge of the depth distribution of viable seeds in soil is indispensable, e.g. for topsoil removal, a regularly applied restoration measure in some habitats (Grootjans et al. 2001), has a significant impact on seed availability. The soil removal treatment dramatically decreased the availability of seeds in the seed bank in dune slacks (Grootjans et al. 2001), flood meadows (Holzel & Otte 2003) and fen meadows (Ramseier 2000), indicating that soil seed bank density and composition decline monotonically with soil depth. Some studies conversely stated that viable seed density in deeper layers is higher than in shallow layers or that the distribution of seeds along depth is binomial (Espinar et al. 2005). Depth distribution is often a reasonably good indicator of seed longevity (Thompson et al. 1997; Bekker et al. 1998). Salt-marshes can differ in salt concentration (Adam 1990). Several studies have proven that salinity can delay or hamper the germination (Rubio-Casal et al. 2003). As a result, in higher salinity conditions it can be expected that a relatively higher number of seeds may penetrate to the soil compared with less saline conditions. In chapter 6, we will compare the depth distribution of seeds in two salt-marshes differing in salt concentration (euhaline and mesohaline). Seed bank and above-ground vegetation can have a mutual interaction. This interaction can be influenced by age (Wolters et al. 2002), as the above-ground vegetation changes during succession. In terrestrial habitats, several studies reported on the vertical and horizontal distribution of seeds in soil with respect to age (e.g. Bossuyt & Hermy 2003), while knowledge is scant for salt-marsh habitats (but see Wolters & Bakker 2002). Early
successional species tend to form persistent seed banks and late successional species tend to show a more transient seed bank (Bossuyt & Hermy, 2004). Therefore it can be expected that seed density and similarity between seed bank and above ground vegetation decrease along time. Seed bank density and similarity with above-ground vegetation will be compared for early and late successional stages in chapter 6. It is hypothesized that the vertical distribution of seeds is different for euhaline and mesohaline salt-marshes. In addition, it is further hypothesized that seed density and similarity between seed bank and above-ground vegetation in old salt-marsh is lower than in new salt-marsh. 1.4 The reasons why to study succession in a restoration program Successional vegetation processes are an important aspect in ecological restoration, because they determine the type and timing of restoration measures used and affect the final success. Therefore, vegetation succession and its study should be taken into account in virtually any restoration program. On the other hand, results of both spontaneous processes and restoration measures are usually intermingled and influence each other (Luken 1990). In some restoration programs, we can completely rely on spontaneous succession (Prach et al. 2001). Spontaneous succession is affected by many local biotic and abiotic factors and their interactions and, hence, will be different in different places. It is not possible to extrapolate the results of a study in a particular location to other locations (Eviner & Hawkes 2008). Many restoration failures can be attributed to site-specific issues that were not taken into account (Wassenaar et al. 2007), indicating the importance of studies on natural plant succession in each site separately. Beside the importance of vegetation succession studies in restoration programs, newly (by man or naturally) created substrates offer us unique opportunities to study plant succession fundamentally, in which salt-marshes are a remarkable habitat. Salt-marsh communities normally arise on bare substrate and when mature are often eroded, creating bare 17
Page 1: Ghent University Faculty of Science
Page 5: Spatio-temporal aspects of early ve
Page 9 and 10: Acknowledgements The accomplishment
Page 11: List of Abbreviations ADF Acid Dete
Page 14 and 15: XII 3.5 DISCUSSION ................
Page 16 and 17: 1.1 What is succession? 2 Successio
Page 18 and 19: completely destroy the existing veg
Page 20 and 21: also occur in salt-marsh habitat, a
Page 22 and 23: seed production (Willson 1983; Pric
Page 24 and 25: 1.3.2 Inundation, vegetation and su
Page 26 and 27: affected plant species richness in
Page 28 and 29: 14 In chapter 4, the effects of she
Page 32 and 33: areas which are re-colonized. They
Page 34 and 35: Fig. 1.4. The position of the newly
Page 36 and 37: 22 There are some photos available
Page 38 and 39: were collected systematically along
Page 40 and 41: Table 1.1. Materials and methods us
Page 42 and 43: with one or more reference sites (T
Page 44 and 45: pilot study performed in the area i
Page 46 and 47: Fig. 1.7. The conceptual framework
Page 48 and 49: 2.1 Abstract Restoration of salt-ma
Page 50 and 51: 2.2 Introduction The successful res
Page 52 and 53: physiological process depending on
Page 54 and 55: separated from it by a dike (with a
Page 56 and 57: scale (Londo 1976). According to th
Page 58 and 59: 2.4.2 Seed bank at the restoration
Page 60 and 61: Table 2.3. Average (± SE) species
Page 62 and 63: particular those species coming fro
Page 64 and 65: germinate, the seeds should have ap
Page 66 and 67: the restoration site along a strong
Page 68 and 69: 3.1 Abstract 54 The effect of inund
Page 70 and 71: 3.2 Introduction 56 Tidal marshes a
Page 72 and 73: more stable. Consequently, species
Page 74 and 75: 3.3.2.2 Inundation frequency 60 The
Page 76 and 77: and 2007) for those variables that
Page 78 and 79: maritima) increased over time (Fig.
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perennial species between years, wi
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68 Perennial richness 1.4 1.2 1 0.8
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70 Species turnover 1.2 1 0.8 0.6 0
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Reznicek 1986). They therefore play
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Suaeda maritima. Spartina is well k
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4.1 Abstract 76 In this paper, the
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4.2 Introduction 78 Salt-marshes ar
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available on the influence of sheep
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consecutive months, sampling effort
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factor was applied. In case of sign
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Table 4.1. The result of repeated m
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88 Cover(%) 2.5 2 1.5 1 0.5 0 C a b
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90 2.5 2 1.5 1 0.5 0 a b a b Grazed
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succession leading to rapid vegetat
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(van Wijnen et al. 1997). In additi
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5.1 Abstract 96 It is generally acc
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5.2 Introduction 98 One of the main
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area started in 2002, when part of
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high and highly significant (see Ta
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104 Although the percentage of spec
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5.5 Discussion 106 Not surprisingly
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europaea zone as long as the elevat
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110
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6.1 Abstract 112 Seed bank density
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6.2 Introduction 114 The persistenc
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116 Our study area consists of thre
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were also placed randomly on the sh
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Seed density(m²) Seed density(m²)
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122 Plant species in the above-grou
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6.4.2 Seed bank properties and sali
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Seed density(m²) Seed density(m²)
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conclude that Suaeda seeds are most
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130 Both the similarity between sta
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marsh were found not to be fundamen
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134 Permanent plots in this study g
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(soil and elevation), and between v
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138 In literature it is generally a
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ecome extinct, some palatable and s
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production, but their massive produ
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144 Grazing in the entire year migh
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146
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Bakker, E.S. & Olff, H. 2003. The i
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Bertness, M.D., Wise C. & Ellison A
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Burrows, C.J. 1990. Processes of ve
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de Leeuw, J. 1992. Dynamics of salt
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Egler, F.E. 1954. Vegetation scienc
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Garbutt, A. & Wolters, M. 2008. The
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Harper, J.L. 1961. Approaches to th
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Hoffmann, M. 2006a. 5. De natuurher
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Janssen, J.A.M. & Schaminée, J.H.J
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Klotzli, F. & Grootjans, A.P. 2001.
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Levine, J.M., Brewer, J.S. & Bertne
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Myster, R.W. & Pickett, S.T.A. 1990
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Packham, J.R. & Willis, A.J. 1997.
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Poschlod, P., Tackenberg, O. & Bonn
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Rozema, J. & Blom B. 1977. Effects
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Smith, T.B., Kark, S., Schneider, C
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Thompson, K., Bakker, J.P. & Bekker
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van Leeuwen, C.G. 1966. A relation
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Wijnen, H.J.V. & Bakker, J.P. 1999.
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186
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of a continuous water bridge betwee
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Appendix F - Continued Samolus vala
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Appendix G - Continued Rubus caesio
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PhD Reza Erfanzadeh 2009 - Ghent Ecology - Universiteit Gent

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