Post on 29-Mar-2015
SE
R –
Sum
mer
Sch
ool 2
009
– M
ünst
er U
nive
rsity
Department Biology
HamburgUniversity
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
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
02.07.09Kai Jensen SER Summer School 2009
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
1000 m
1950
1985
2002
Drainage, Eutrophication
Abandonment
Changes of fen grassland area and distribution
(1950 – 2002; Lake Vollstedt, Northern Germany
02.07.09Kai Jensen SER Summer School 2009
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
Yacoub (2002)
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
02.07.09Kai Jensen SER Summer School 2009
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
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)?
02.07.09Kai Jensen SER Summer School 2009
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
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?
02.07.09Kai Jensen SER Summer School 2009
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
Temperature and germination
Patzelt et al. (2001)
Silene flos-cuculi
Senecio aquaticus
0
20
40
60
80
100
0
20
40
60
80
100
Ger
min
atio
n [
%]
Temperature [°C]
Methods
• Dry-stored seeds
• Constant tempe-ratures (3 – 35°C)
• Fluctuating tempe-ratures (5/15°C; 10/25°C)
• Diurnal light regime
02.07.09Kai Jensen SER Summer School 2009
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
Temperature fluctuations and germination
Schütz (1999)
Carex elongata
Carex elata
Ger
min
atio
n [
%]
0
20
40
60
80
100
0 2 4 6 8 10 12 14 16
light
darkness
0
20
40
60
80
100
0 2 4 6 8 10 12 14 16
Amplitude [°C]
Methods
• Dry-stored seeds
• Daily fluctuating temperatures (amplitudes from 0 – 16°C)
• Mean temperature 22°C
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Canopy effects on light quantity and quality
Above leaf-canopy
• red : far-red = 1.2
Below leaf-canopy
• red : far-red = 0.18
PFRPR
R660
FR730
germi-nation
Phytochrome-System
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Pons (19xy)
Light quality and germination
Maas (1989)
0
20
40
60
80
100
white dark red far_red
Ge
rmin
ati
on
[%
]
0
20
40
60
80
100
white dark red far_red
Ge
rmin
ati
on
[%
]
Primula farinosa
Tofieldia calyculata
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Seed mass and light-requirement for germination
Seed mass [mg]
Pro
po
rtio
n o
f g
erm
inat
ion
in d
arkn
ess
inre
lati
on
to
ger
min
atio
n in
lig
ht
[%]
0
20
40
60
80
100
0.01 0.10 1.00 10.00
r = 0.57 p < 0.001
Jensen & Gutekunst (2003)
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Germination in light and in darkness
0.00
0.20
0.40
0.60
0.80
1.00
Maas (1989)
Jensen(1999)
Jensen &Gutekunst(in press)
Schütz &Rave(1999)
total
unaffected
promoted by light
N = 25 17 35 23 100
(2003)
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Variation of germination within single inflorescences
0
5
10
15
20
25
30
35
40
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Days
center
margin
0
5
10
15
20
25
30
35
40
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Days
centre
margin
Nu
mb
er o
f g
erm
inat
ed s
eed
s
Days Brändel (2004)
Dispersal ability
low high
Bidens
frondosa
25°C
10/20°C
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Temporal changes of germination requirements
0
20
40
60
80
100
oct
dec
feb
apr
jun aug
oct
dec
feb
apr
jun aug
oct
light
darkness
Ger
min
atio
n [
%]
1991 1992 1993
Milberg (1994)
primary dormancy
secondary dormancy
Dormancy release
Dormancy induction
Silene flos-cuculi
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Germination ecology and zonation in wetlands
Salinity [%]
Ger
min
atio
n p
erce
nta
ge
0.0 0.7 1.4 2.1 2.8 3.5
0
20
40
60
80
100Elymus athericus
Spartina anglica 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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
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
xxxxxxxxxxxxxxxx
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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Dormancy and seed longevity:Burial experiment with seeds of wetland species
Jensen (2004)
Ger
min
atio
n [
%]
Date
0
20
40
60
80
100
Sep Jan May Sep FebNov Mar Jul Nov Apr
Jun
0
20
40
60
80
100
Nov Mar Jul Nov Mar JulJan May Sep Jan May Sep
1997 1998 1999 1996 1997 1998
Mo
rtality [%]
DarknessLight
Mortality
Bromus racemosus Sanguisorba officinalis
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Dormancy and seed longevity:Burial experiment with seeds of wetland species
Jensen (2004)
Ger
min
atio
n [
%]
Date
0
20
40
60
80
100
0
20
40
60
80
100
Nov Mar Jul Nov Mar JulJan May Sep Jan May Sep
1996 1997 1998
Mo
rtality [%]
DarknessLight
Mortality
Rhinanthus angustifolius Pedicularis palustris
Nov Mar Jul Nov Mar JulJan May Sep Jan May Sep
1996 1997 1998
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Ger
min
atio
n [
%]
Date
0
20
40
60
80
100
0
20
40
60
80
100
Nov Mar Jul Nov Mar JulJan May Sep Jan May Sep
1996 1997 1998
Mo
rtality [%]
Viola palustris Carex echinata
Nov Mar Jul Nov Mar JulJan May Sep Jan May Sep
1996 1997 1998
DarknessLight
Mortality
Jensen (2004)
Dormancy and seed longevity:Burial experiment with seeds of wetland species
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Seedbank typeYear 1 Year 2 Year 5 Year 1 Year 2 Year 5
Bromus racemosus 50.0 - - 53.0 100.0 100.0 transientSanguisorba officinalis 90.7 - - 22.7 100.0 100.0 transientSuccisa pratensis 78.8 - - 54.5 100.0 100.0 transient
Angelica sylvestris 63.7 8.3 - 27.1 95.0 100.0 short-term persistentBriza media 98.9 4.2 - 29.9 81.8 100.0 short-term persistentGalium uliginosum 61.9 18.3 (1) 51.1 65.5 99.3 short-term persistentParnassia palustris 39.3 6.2 0.0 - - - short-term persistentPeucedanum palustre 93.0 44.5 - 13.1 32.0 100.0 short-term persistentRhinanthus angustifolius agg. 47.5 28.6 - 7.2 87.0 100.0 short-term persistentThalictrum flavum 84.8 40.6 (1) 19.8 51.7 99.3 short-term persistentTriglochin palustre 92.0 29.4 - 21.0 64.4 100.0 short-term persistentValeriana dioica 48.4 34.8 - 68.4 86.2 100.0 short-term persistent
Carex demissa 58.0 25.5 66.9 8.7 9.7 35.0 long-term persistentCarex echinata 80.0 44.1 95.8 5.0 12.7 38.8 long-term persistentCarex panicea 14.9 83.4 92.6 5.5 20.0 33.6 long-term persistentJuncus filiformis 166.5 230.0 69.3 - - - long-term persistentPedicularis palustris 76.6 93.5 58.3 41.3 56.4 75.0 long-term persistentPotentilla palustris 68.9 23.8 40.2 12.1 21.1 45.2 long-term persistentSilene flos-cuculi 84.8 90.8 72.6 18.7 30.0 50.0 long-term persistentViola palustris 89.8 58.8 80.4 13.7 24.7 53.0 long-term persistent
Germination [%] Mortality [%]
Jensen (2004)
Dormancy and seed longevity:Burial experiment with seeds of wetland species
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
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
xxxxxxxxxxxxxxxx
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 soilAll COUNTSREAL SEEDBANK COUNTS
Classification rules for seed bank types
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
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
transient short-term persistent
long-term-persistent
LI
All counts 34 52 30 0.7Real seedbank counts 6 52 30 0.9Burial experiments 0 2 2 1.0
LI = short-term + long-term persistent records
transient + short-term + long-term persistent records
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Seed persistence of species groups
LI All counts Real seedbank counts Burial experiments
0.0
0.2
0.4
0.6
0.8
1.0
Fo
rag
e g
rass
lan
d
Oth
ers
Ru
der
al
Wet
gra
ssla
nd
Ree
d
Fen
Fo
rag
e g
rass
lan
d
Oth
ers
Ru
der
al
Wet
gra
ssla
nd
Ree
d
Fen
Fo
rag
e g
rass
lan
d
Oth
ers
Ru
der
al
Wet
gra
ssla
nd
Ree
d
Fen
aba
ab
b
abab
nsLow habitat specifity
High habitat specifity ab
aab
b ab
ab
Kruskall-Wallis-Test
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Habitat specifity, rarity and seed persistence
Low habitat specifity
High habitat specifity
Lo
ng
evit
y -
Ind
ex
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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
controlmowing
small gapslarge gaps
Disturbance treatment
2
10
20
40
Nu
mb
er o
f in
div
idu
als
Pedicularis palustris
250 1250 5000
Sowing density[seeds/m²]
July 2002
controlmowing
small gapslarge gaps
Disturbance treatment
2
10
20
40
Rhinanthus angustifolius
Nu
mb
er o
f in
div
idu
als
• 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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Rasran, Vogt & Jensen (2006)
Field experiment in floodplain grasslands (Soomaa NP, Estonia)
Drift line
Dis
turb
ance
yes no
no
small gaps
large gaps
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Effects of seed banks and dispersal on wetlands
Sp
ecie
s n
um
ber
of
recr
uit
ing
se
edli
ng
s p
er 6
25cm
²
0
4
8
12
yes no
16
no small gaps
large gaps
Drift line Disturbance
a
b
c
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Wanner (2002)
Effects of seed banks and dispersal on wetlands: Baltic coastal grasslands
Nu
mb
er o
f se
edli
ng
s p
er g
ap
Yes NoSeed Bank
0
5
10
15
20
25
30
35
40
45
50
Yes No
without vegetative regrowth
with vegetative regrowth
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
Ludewig (2009)
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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
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 banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009
PostdocMarkus BrändelAntonia Wanner
Technische MitarbeiterClaudia MählmannJutta KrügerDetlev Böhm
Doktoranden und wiss. MitarbeiterKati VogtLeonid RasranWiebke SchoenbergSonja HeemannSigrid SuchrowGesine EngelsEbrahem MohamedKristin LudewigFrauke MüllerSebastian SchmidtKatharina SchmidtChristian Butzeck
Vielen Dank
AbschlussarbeitenSandra BurmeierAnke BrandtDirk LübsenJessica HenselJan SchwertdfegerMarie HrachNina PohlmannFelix HeydelJessica EhrhardtJessica KlepgenChristian KlausLotte KorrellAgathe SchaddachJule KrauseKatharina KleißFriederike FreiwaldSinaida AlbrechtFrauke BrunckhorstCarolin GallinatJana Melanie HankeCaroline ThiemNina Moniac
ConclusionsEstablishmentSeed banksGerminationIntroduction Dispersal
02.07.09Kai Jensen SER Summer School 2009