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SER – Summer School 2009 – Münster University Department Biology Hamburg University The (potential) role of seed ecology in restoration: Germination, seed.

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Presentation on theme: "SER – Summer School 2009 – Münster University Department Biology Hamburg University The (potential) role of seed ecology in restoration: Germination, seed."— Presentation transcript:

1 SER – Summer School 2009 – Münster University Department Biology Hamburg University The (potential) role of seed ecology in restoration: Germination, seed banks and establishment Kai Jensen Applied Plant Ecology University of Hamburg kai.jensen@botanik.uni-hamburg.de

2 Outline Introduction Germination Influence of abiotic factors Persistence and Seed Banks Primary and secondary dormancy Seed bank types Dispersal Hydrochorous seed transport Establishment Seed- versus microsite-limitation Summary and conclusions 02.07.09 Kai JensenSER Summer School 2009 ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal

3 1000 m 1950 1985 2002 Drainage, Eutrophication Abandonment Changes of fen grassland area and distribution (1950 – 2002; Lake Vollstedt, Northern Germany 02.07.09 Kai JensenSER Summer School 2009 ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal Yacoub (2002)

4 Seed banks and succession in changing landscapes You have only to dig a pond anywhere … and you will soon have … the usual waterplants (Thoreau 1860) Early phase of farm abandonment in New England Forest recovery You have only to restore the site conditions including a proper hydroregime anywhere and you will soon have the usual wetland species Application of fertilizers led to an eutrophication of the landscape Widespread land use has greatly homogenized formerly dissimilar habitats Human development and land-use changes are accompanied with habitat fragmentation 02.07.09 Kai JensenSER Summer School 2009 ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal

5 Questions Are seed banks and seedling establishment important for the conservation and/or restoration of wetlands? Which factors affect the longevity of seeds in the soil? Germination requirements? Dormancy pattern? Seed morphology (weight, shape)? Which factors affect hydrochorous dispersal? Seed buyoancy? Seed production? Which factors limit the establishment of species in wetlands? Seed availability (seed banks, seed dispersal)? Microsite availability (gaps, disturbance)? 02.07.09 Kai JensenSER Summer School 2009 ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal

6 Germination Ecology Germination is a complex process which includes the imbibition of water, an increase in respiration activity, the mobilization of nutrient reserves and the initiation of growth in the embryo. Finally, germination results in the bursting of the testa and the extrusion of the plumule or radicle. How is germination of wetland species affected by abiotic factors? Temperature and temperature fluctuations Light quantity and light quality Salinity Do germination requirements of individual wetland species vary? Within individuals? Among populations? Temporally? 02.07.09 Kai JensenSER Summer School 2009 ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal

7 Temperature and germination Patzelt et al. (2001) Silene flos-cuculi Senecio aquaticus Germination [%] Temperature [°C] Methods Dry-stored seeds Constant tempe- ratures (3 – 35°C) Fluctuating tempe- ratures (5/15°C; 10/25°C) Diurnal light regime 02.07.09 Kai JensenSER Summer School 2009 ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal

8 Temperature fluctuations and germination Schütz (1999) Carex elongata Carex elata Germination [%] Amplitude [°C] Methods Dry-stored seeds Daily fluctuating temperatures (amplitudes from 0 – 16°C) Mean temperature 22°C ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

9 Canopy effects on light quantity and quality Above leaf-canopy red : far-red = 1.2 Below leaf-canopy red : far-red = 0.18 P FR PRPR R 660 FR 730 germi- nation Phytochrome-System ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009 Pons (19xy)

10 Light quality and germination Maas (1989) Primula farinosa Tofieldia calyculata ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

11 Seed mass and light-requirement for germination Jensen & Gutekunst (2003) ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

12 Germination in light and in darkness N = 25173523100 (2003) ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

13 Variation of germination within single inflorescences Number of germinated seeds Days Brändel (2004) Dispersal ability lowhigh Bidens frondosa 25°C 10/20°C ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

14 Temporal changes of germination requirements Germination [%] 199119921993 Milberg (1994) primary dormancy secondary dormancy Dormancy release Dormancy induction Silene flos-cuculi ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

15 Germination ecology and zonation in wetlands Germination of both species is negatively affected by increased salinity Interaction between species and salinity Spartina has a higher germination percentage than Elymus at high salinity Elymus has a higher germination than Spartina at low salinities ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

16 Summary: Germination Most (temperate) wetland species germinate at a wide amplitude of temperatures, but have an optimum between 20 and 30°C Germination of many wetland species is increased by alternating temperatures, which might restrict germination to the spring Light requirement for germination is higher in small-seeded species than in large-seeded ones. The light requirement can be interpreted as an adaptation against fatal germination in the soil Germination requirements vary spatially (within inflorescences, among individuals, among populations) and temporally (dormancy cycles) ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

17 Seed persisitence and seed banks Circumstantial evidence for high longevity of seeds (e.g. Nelumbo nucifera: dried bed of a former lake in NE China; germinating seeds were radiocarbon-dated to be 1288 ± 250 years, Shen-Miller et al. 1995) Seed densities in the soil vary greatly (1 – 100,000 seeds/m²) between ecosystems In general, seed density of individual species exponentially declines after it disappeared in the vegetation ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

18 Seed bank types transient seed persistence in the soil for less than 1 year short-term-persistent seed persistence in the soil for at least 1 year, but less than 5 years play a role in the maintenance of plant populations after a bad year (e.g. poor seed set in a dry year) long-term persistent seed persistence in the soil for at least 5 years may contribute to the restoration of destroyed or degraded plant communities ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

19 Classification rules for seed bank types Present in vegetation or vegetation not described < 5 years since species last grew at site > 4 years since species last grew at site Soil layers not subdivided xxxxxxxxxxx xxxxx Species absent from the vegetation x AT LEAST SHORT-TERM PERSISTENT xxxxxxxxxx PRESENT xxxxxx LONG-TERM PERSISTENT xx Soil layers subdivided by depth xxxxxxxx Present in the seed bank xxxxxxxxxxx x Absent from the seed bank xxxxxxxxxxx x SHORT-TERM PERSISTENT xx xxxxxxxxxx TRANSIENT xxxxxx LONG-TERM PERSISTENT xx xxxxxxxxxx TRANSIENT xxxxxx > 4 years since species last grew at site LONG-TERM PERSISTENT xx A SPECIES FOUNDx Present in vegetation or vegetation not described Present only in surface soil xxxxxxxxx xxxxxxx More freq. in upper but present in lower soil layers At least as freq. in lower as in upper soil layers Species absent from the vegetation x < 5 years since species last grew at site Thompson et al. 1997 Criteria Presence/absence in vegetation and seed bank Depth distribution in the soil ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

20 Main conclusions of Thompson et al. (1997) Grassland species have in general a low seed persistence Rare species have a lower persistence than common ones Seed size and shape are good predictors of seed persistence Is that really true?? ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

21 Dormancy and seed longevity: Burial experiment with seeds of wetland species Jensen (2004) Germination [%] Date Mortality [%] Darkness Light Mortality Bromus racemosusSanguisorba officinalis ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

22 Dormancy and seed longevity: Burial experiment with seeds of wetland species Jensen (2004) Germination [%] Date 0 20 40 60 80 100 0 20 40 60 80 100 NovMarJulNovMarJul JanMaySepJanMaySep 199619971998 Mortality [%] Darkness Light Mortality Rhinanthus angustifoliusPedicularis palustris NovMarJulNovMarJul JanMaySepJanMaySep 199619971998 ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

23 Germination [%] Date 0 20 40 60 80 100 0 20 40 60 80 100 NovMarJulNovMarJul JanMaySepJanMaySep 199619971998 Mortality [%] Viola palustrisCarex echinata NovMarJulNovMarJul JanMaySepJanMaySep 199619971998 Darkness Light Mortality Jensen (2004) Dormancy and seed longevity: Burial experiment with seeds of wetland species ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

24 Jensen (2004) Dormancy and seed longevity: Burial experiment with seeds of wetland species ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

25 Seed bank analysis 31 wet grasslands in Northern Germany Meso- and eutrophic fen grasslands (Scheuchzerio-Caricetea, Calthion, Lolio-Potentillion) Managed and abandoned sites Burial experiments 45 species of the regional fen flora Carex (Schütz 1997, 1998, 1999) Regional rare species (Jensen 2001, 2004) Asteraceae and Lamiaceae (Brändel 2004) Database and literature survey Thompson-Database (Thompson et al. 1997) 16 seed bank studies (wet grasslands, 143 sites in Europe) Database on seed banks of wetland species ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

26 Present in vegetation or vegetation not described < 5 years since species last grew at site > 4 years since species last grew at site Soil layers not subdivided xxxxxxxxxxx xxxxx Species absent from the vegetation x AT LEAST SHORT-TERM PERSISTENT xxxxxxxxxx PRESENT xxxxxx LONG-TERM PERSISTENT xx Soil layers subdivided by depth xxxxxxxx Present in the seed bank xxxxxxxxxxx x Absent from the seed bank xxxxxxxxxxx x SHORT-TERM PERSISTENT xx xxxxxxxxxx TRANSIENT xxxxxx LONG-TERM PERSISTENT xx xxxxxxxxxx TRANSIENT xxxxxx > 4 years since species last grew at site LONG-TERM PERSISTENT xx A SPECIES FOUNDx Present in vegetation or vegetation not described Present only in surface soil xxxxxxxxx xxxxxxx More freq. in upper but present in lower soil layers At least as freq. in lower as in upper soil layers Species absent from the vegetation x < 5 years since species last grew at site Thompson et al. 1997 Criteria Presence/absence in vegetation and seed bank Depth distribution in the soil All COUNTS REAL SEEDBANK COUNTS Classification rules for seed bank types ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

27 Classification of species to seed bank types Indirect procedure following Thompson et al. (1997): All counts, Real seedbank counts Direct procedure (burial experiments) Calculation of the Longevity-Index (LI, Bekker et al. 1998) Silene flos-cuculi Methods: Seed bank research transientshort-term persistent long-term- persistent LI All counts3452300.7 Real seedbank counts652300.9 Burial experiments0221.0 LI = short-term + long-term persistent records transient + short-term + long-term persistent records ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

28 Seed persistence of species groups LI All countsReal seedbank countsBurial experiments 0.0 0.2 0.4 0.6 0.8 1.0 Forage grasslandOthersRuderalWet grasslandReedFenForage grasslandOthersRuderalWet grasslandReedFenForage grasslandOthersRuderalWet grasslandReedFen ab a b ns Low habitat specifity High habitat specifity ab a b Kruskall-Wallis-Test ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

29 Habitat specifity, rarity and seed persistence Low habitat specifity High habitat specifity Longevity - Index 0.0 0.2 0.4 0.6 0.8 1.0 *** All counts Real seedbank counts Burial experi- ments Common Rare All counts Real seedbank counts Burial experi- ments ** Mann-Whitney-U-Test ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

30 Summary: Persistence and seed banks Seed banks of many wet grassland species are at least short-term persistent Rare or endangered wet grassland species do not have a lower persistence than common species Seed persistence in the soil has been underestimated by the methods applied by Thompson et al. (1997) Seed banks can be an important factor for the conservation or restoration of species-rich wet grasslands ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

31 Seed transport by running water Seed trapping (Eider: 2 years; Soomaa: 1 summer) Recapture experiment (Eider) Dispersal of seed mimics (Elbe) Modelling of hydrochorous seed transport (Elbe) Seed sedimentation during flooding Drift-line material (Eider, Soomaa, Elbe) Astroturf mats (Eider and Elbe: 2002, 2004) Dispersal by wind and animals Community seed rain (Eider; Jensen 1998) Seed shadow of wet grassland species Seed content of cattle faeces Methods: Seed dispersal research ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

32 Establishment: Methods and questions Factorial field experiments. Manipulation of … Seed availability (e.g. sowing, removal of the seed bank, exclosure of seed dispersal, application of seed-containing drift-line material) Microsite availabilty (e.g. creation of gaps, mowing) Is seedling establishment of wetland species limited by seed or by microsite availability? Is species richness of wetlands limited by seed or by microsite availability? ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

33 Large gaps Small gaps Control Mowing Sowing experiment (Pedicularis and Rhinanthus) 10 blocks per species 4 disturbance treatments (control, mowing, small gaps, large gaps) 4 sowing densities (control, 250, 1250, 5000 seeds per m²) Monitoring of recruitment, survival and reproduction ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

34 Number of individuals bienniel Seed weight: 1.1 mg Limited by seed and by microsite availability annual Seed weight: 2.2 mg Limited only by seed availabilty ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009 Rasran, Vogt & Jensen (2006)

35 Field experiment in floodplain grasslands (Soomaa NP, Estonia) Drift line Disturbance yesno small gaps large gaps ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

36 Effects of seed banks and dispersal on wetlands Species number of recruiting seedlings per 625cm² 0 4 8 12 yesno 16 nosmall gaps large gaps Drift lineDisturbance a b c ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009 Wanner (2002)

37 Effects of seed banks and dispersal on wetlands: Baltic coastal grasslands Number of seedlings per gap YesNo Seed Bank 0 5 10 15 20 25 30 35 40 45 50 YesNo without vegetative regrowth with vegetative regrowth ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009 Ludewig (2009)

38 Species not present in the vegetation are in general limited by seed availability (Pedicularis, Rhinanthus) Species with high seed densities in the seed bank or with high potential of hydrochorous seed dispersal might establish after some kind of soil disturbance Germination from seed banks might contribute to species richness in wetlands (floodplain grasslands, coastal grasslands) Summary: Establishment ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

39 Summary and conclusion Many wetland species have persistent seed banks Hydrochorous dispersal enables wetland species to move large distances and to reach new habitats Seed banks and seed dispersal can significantly contribute to nature management and restoration of wetlands Conservation of still existing wetland patches should obtain priority Restoration success of wetlands depends on: site conditions, management, spatial and temporal aspects ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

40 THM You have only to dig a pond anywhere … and you will soon have … the usual waterplants (Thoreau 1860) You have only to restore the site conditions and a proper hydrological management anywhere and you will soon have the usual wetland species ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009

41 Postdoc Markus Brändel Antonia Wanner Technische Mitarbeiter Claudia Mählmann Jutta Krüger Detlev Böhm Doktoranden und wiss. Mitarbeiter Kati Vogt Leonid Rasran Wiebke Schoenberg Sonja Heemann Sigrid Suchrow Gesine Engels Ebrahem Mohamed Kristin Ludewig Frauke Müller Sebastian Schmidt Katharina Schmidt Christian Butzeck Vielen Dank Abschlussarbeiten Sandra Burmeier Anke Brandt Dirk Lübsen Jessica Hensel Jan Schwertdfeger Marie Hrach Nina Pohlmann Felix Heydel Jessica Ehrhardt Jessica Klepgen Christian Klaus Lotte Korrell Agathe Schaddach Jule Krause Katharina Kleiß Friederike Freiwald Sinaida Albrecht Frauke Brunckhorst Carolin Gallinat Jana Melanie Hanke Caroline Thiem Nina Moniac ConclusionsEstablishmentSeed banksGerminationIntroductionDispersal 02.07.09 Kai JensenSER Summer School 2009


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