Baltic amber forest

327 Pages·2017·22.6 MB·English

Towards a new picture of the ‘Baltic amber
forest’  flora, habitat types, and palaeoecology

Dissertation
zur Erlangung des mathematisch-naturwissenschaftlichen Doktorgrades
"Doctor rerum naturalium"
der Georg-August-Universität Göttingen

im Promotionsprogramm Geoscience
der Georg-August University School of Science (GAUSS)

vorgelegt von
Eva-Maria Sadowski

aus Lüdenscheid
Göttingen, 2017

Betreuungsausschuss

Prof. Dr. Alexander Schmidt, Georg-August-Universität Göttingen, Abteilung
Geobiologie, Arbeitsgruppe "Evolution der Landpflanzen und Entwicklung der
terrestrischen Ökosysteme"

Dr. Leyla J. Seyfullah, Georg-August-Universität Göttingen, Abteilung Geobiologie,
Arbeitsgruppe "Evolution der Landpflanzen und Entwicklung der terrestrischen
Ökosysteme"

Dr. Lutz Kunzmann, Senckenberg Naturhistorische Sammlungen Dresden, Sektion
Paläobotanik

Mitglieder der Prüfungskommission

Referent:
Prof. Dr. Alexander Schmidt, Abteilung Geobiologie, Arbeitsgruppe "Evolution der
Landpflanzen und Entwicklung der terrestrischen Ökosysteme", Georg-August-
Universität Göttingen

Korreferent:
Dr. Lutz Kunzmann, Sektion Paläobotanik, Senckenberg Naturhistorische
Sammlungen Dresden

Prof. Dr. Hermann Behling, Abteilung Palynologie und Klimadynamik, Georg-
August-Universität Göttingen

PD Dr. Dirk Gansert, Abteilung Plfanzenökologie und Ökosystemforschung, Georg-
August-Universität Göttingen

Prof. Dr. Jouko Rikkinen, Finnish Museum of Natural History, University of
Helsinki

Dr. Leyla Seyfullah, Abteilung Geobiologie, Arbeitsgruppe "Evolution der
Landpflanzen und Entwicklung der terrestrischen Ökosysteme", Georg-August-
Universität Göttingen

Tag der mündlichen Prüfung: 14.06.2017

i
Content

Appendices ................................................................................................................. iv
List of tables and figures ............................................................................................ v

Summary ..................................................................................................................... 1
1. Introduction ............................................................................................................ 3
1.1. What is amber? ...................................................................................................... 3
1.2 Amberization and the formation of an amber deposit ........................................... 3
1.3 Amber deposits worldwide and in the Baltic area ................................................. 4
1.4 Amber classification .............................................................................................. 5
1.5 Abundance and formation of inclusions from Baltic amber ................................. 6
1.6 The Baltic amber mysteries ................................................................................... 9
1.6.1 Geographical location of the ‘Baltic amber forest’ and the age of
Baltic amber .................................................................................................................. 9
1.6.2 Putative source plants of Baltic amber .............................................................. 11
1.6.2.1 Morphological-anatomical implications from Baltic amber inclusions ........ 15
1.6.2.2 Chemical analyses for inferring the Baltic amber tree ................................... 15
1.6.2.3 Succinic acid – key component or diagenetic product? ................................. 16
1.6.3 The enigmatic ‘Baltic amber forest’ .................................................................. 17

2. Aims of this thesis ................................................................................................ 20

3. Material and methods .......................................................................................... 21
3.1 Specimens investigated......................................................................................... 21
3.2 Preparation, microscopy and imaging .................................................................. 21
3.3 Permanent preparation .......................................................................................... 22

4. Plant inclusions: their contribution to the understanding of vegetation,
palaeoecology and habitat structure of the ‘Baltic amber forest’ ........................ 24
4.1 Conifers ................................................................................................................ 24
4.1.1 Unexpected conifer diversity of the Baltic amber flora .................................... 24
4.1.2 Indeterminable conifers – challenges and preliminary results .......................... 27
4.1.3 Conifer inclusions revise our understanding of the Baltic amber source area .. 40
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4.1.4 New candidates for the Baltic amber source plant ............................................ 41
4.2 Angiosperms ......................................................................................................... 46
4.2.1 Angiosperm diversity of the Baltic amber flora ................................................ 46
4.2.2 Angiosperm inclusions and their potential as palaeoecological key taxa .......... 54
4.3 Indicators for life forms and microhabitat complexity ......................................... 58

5. What is new about the picture of the ‘Baltic amber forest’? ........................... 64
5.1. Habitat heterogeneity and stratification of the ‘Baltic amber forest’ .................. 64
5.2. Palaeoclimatic estimations of the ‘Baltic amber forest’ ...................................... 66
5.3. Wheeler’s dilemma, the Eridanos river and the quest for mountains in the
‘Baltic amber forest’ ................................................................................................... 68
5.4. Geoflora concept – does it apply to the ‘Baltic amber forest’? ........................... 72

6. Conclusions and outlook ...................................................................................... 75
7. Acknowledgements ............................................................................................... 76
8. References ............................................................................................................. 77

Versicherung ............................................................................................................... 97
Declaration about own contributions to the papers included in this thesis ................. 98
Appendices ................................................................................................................ 101

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Appendices

[1] Seyfullah, L. J., E.-M. Sadowski, and A. R. Schmidt. 2015. Species-level
determination of closely related araucarian resins using FTIR spectroscopy and its
implications for the provenance of New Zealand amber. PeerJ 3:e1067, doi:
10.7717/peerj.1067.

[2] Kettunen, E., H. Grabenhorst, C. Gröhn, H. Dörfelt, E.-M. Sadowski, J.
Rikkinen, and A. R. Schmidt. 2015. The enigmatic hyphomycete Torula sensu
Caspary revisited. Review of Palaeobotany and Palynology 219:183-193.

[3] Sadowski, E.-M., A. R. Schmidt, L. Kunzmann, C. Gröhn, and L. J. Seyfullah.
2016a. Sciadopitys cladodes from Eocene Baltic amber. Botanical Journal of the
Linnean Society 180:258-268.

[4] Sadowski, E.-M., A. R. Schmidt, P. J. Rudall, D. A. Simpson, C. Gröhn, J.
Wunderlich, and L. J. Seyfullah. 2016b. Graminids from Eocene Baltic amber.
Review of Palaeobotany and Palynology 233:116-168.

[5] Sadowski, E.-M., A. R. Schmidt, L. J. Seyfullah, and L. Kunzmann. 2017a.
Conifers of the ‘Baltic amber forest’ and their palaeoecological significance. Stapfia
(in press).

[6] Sadowski, E.-M., L. J. Seyfullah, C. A. Wilson, C. L. Calvin, and A. R. Schmidt.
2017b. Diverse early dwarf mistletoes (Arceuthobium), ecological keystones of the
Eocene Baltic amber biota. American Journal of Botany 104: 1-25.
doi:10.3732/ajb.1600390.

iv
List of tables and figures

Tables

Tab. 1: Classification system for ambers ......................................................................... 6
Tab. 2: Suggested source plants of Baltic amber ........................................................... 14
Tab. 3: Perceptions of the ‘Baltic amber forest’. ........................................................... 19
Tab. 4: Baltic amber collections examined for this thesis ............................................. 21
Tab. 5: Updated list of coniferous inclusions from Baltic amber .................................. 25
Tab. 6: Preliminary results of morphotypes of cupressaceous twig fragment
inclusions from Baltic amber .......................................................................................... 31
Tab. 7: Preliminary results of cupressaceous pollen cone types from Baltic amber ..... 36
Tab. 8: Arguments for and against different suggested source trees of Baltic
succinite .......................................................................................................................... 45
Tab. 9: Current list of angiosperms from Baltic amber ................................................. 47
Tab. 10: Angiosperm families described from Baltic amber and their suggested
geographical affinity, after Czeczott (1961). .................................................................. 55

Figures

Fig. 1: Cupressaceous twig fragment inclusions from Baltic amber, assigned to shoot
type 1 ............................................................................................................................... 30
Fig. 2: Cupressaceous twig fragment inclusion from Baltic amber, assigned to shoot
type 2 ............................................................................................................................... 33
Fig. 3: Cupressaceous twig fragment inclusions from Baltic amber, assigned to shoot
type 3 ............................................................................................................................... 34
Fig. 4: Cupressaceous pollen cone inclusions from Baltic amber, assigned to pollen
cone type 1 to 3 ............................................................................................................... 38
Fig. 5: A carnivorous leaf inclusion from Baltic amber and extant Roridulaceae ......... 49
Fig. 6: Inclusions of fagaceous male inflorescences from Baltic amber ........................ 51
Fig. 7: Inclusions of ericoid twig framgents from Baltic amber .................................... 53
Fig. 8: Extant dwarf mistletoe species (Arceuthobium spp., Viscaceae) from the
United States ................................................................................................................... 60
v

Summary

Amber is fossilized resin that was excreted by conifers or angiosperms. Plant and
animal remains which got caught inside of these ancient resin flows are called
‘inclusions’ and are often preserved with high fidelity. Amber deposits which are
remarkably rich in inclusions mainly occur in Cretaceous and Cenozoic sediments.
The Eocene Baltic amber is a prominent example which constitutes the largest amber
deposit worldwide and is famous for its plenitude of inclusions that mainly comprise
arthropod taxa.
This thesis, however, focuses on plant inclusions from Baltic amber, which
are rare, and less studied than the arthropod inclusions. Despite their rareness, plant
inclusions are significant for the reconstruction of the palaeoecosystem from which
the amber derives, the so-called ‘Baltic amber forest’. Up to now, knowledge about
the ‘Baltic amber forest’ is mainly based on historic descriptions of plant inclusions
from the 19th century and on the interpretation of animal inclusions. Contradictory
pictures of the ‘Baltic amber forest’ exist, ranging from tropical lowland rainforests
with neighbouring subtropical to temperate mountain forests to steppe forests and
pure, dense conifer stands that only intermingled with angiosperm trees along their
margins. The topography of the Baltic amber source area is mainly interpreted as
mountainous, but also theories about a plain landscape exist. Further debates are
related to the age of Baltic amber, as well as the locality of its source forests and its
botanical origin. These questions were summarized as ‘Baltic amber mysteries’.
The primary focus of this thesis is to achieve a new picture of the ‘Baltic
amber forest’ by predominantly using plant inclusions. Amber inclusions from
museum and private collections were used to revise described historic specimens and
to identify undescribed plant taxa from Baltic amber. Identified plant taxa were then
compared to their fossil and extant analogues. This comparison served to reconstruct
the potential palaeoecology of plant taxa, as well as their habitat preferences and
palaeoclimatic requirements. With this information, plant diversity, habitat types and
their structure were reconstructed, thus synthesising a new picture of the ‘Baltic
amber forest’.
In this thesis, ten conifer genera were identified from Baltic amber:
Calocedrus, Quasisequoia and Taxodium (Cupressaceae), Cupressospermum
(Geinitziaceae), Abies, Cathaya, Nothotsuga, Pseudolarix and Pinus (Pinaceae), and
Sciadopitys (Sciadopityaceae). The diversity of Cupressaceae is actually higher,
since three morphological complexes of Cupressaceous twig fragments and pollen
cones were also classified. The majority of all identified conifers has not been
verified from Baltic amber before; thus, new candidates for a Baltic amber source
plant should be restudied. In addition, newly discovered or revised angiosperm
inclusions confirm the presence of Poaceae, Cyperaceae (Rhynchospora),
Roridulaceae, Myricaceae (Comptonia), Viscaceae (six species of Arceuthobium),
Ericaceae (Cassiope or Calluna), and Fagaceae (quercoid and castaneoid taxa) in the
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‘Baltic amber forest’. The named conifers and angiosperms allowed the
reconstruction of several habitat types with their respective plant communities from
the Baltic amber source area: coastal lowland swamps under brackish-water
influence, raised bog habitats, non-brackish inundated back swamps and riparian
forests, non-inundated mixed-mesophytic angiosperm-conifer forests with both open
habitat patches (such as meadows) and canopy gaps. Moreover, different life forms
could be reconstructed, such as parasitic (dwarf mistletoes, Arceuthobium) and
carnivorous (Roridulaceae) plants. Previous studies about ferns, bryophytes,
liverworts, fungi and lichens from Baltic amber were also considered in the
interpretation of the microhabitats of the ‘Baltic amber forest’. They indicated
complex and highly diverse communities with epiphytic, terrestrial, saprophytic and
parasitic components.
From a palaeobotanical perspective, there is neither evidence of a
(sub)tropical ‘Baltic amber forest’, nor of an altitudinal stratification of the source
area. This is supported by previous geological studies of the Baltic amber deposit,
which suggest a local amber formation and deposition in the Baltic region during the
late Eocene. No orogenic events took place in the Baltic region, precluding the
presence of mountains in the Baltic amber source area. Comparisons of the Baltic
amber flora with fossil assemblages from the central European Palaeogene showed
clear differences to (sub)tropical fossil floras. Instead the Baltic amber flora indicates
a warm-temperate palaeoclimate with affinities to the extant warm-temperate to
temperate floras of East Asia and North America.
The thorough analyses of available plant inclusions from Baltic amber reveal
a heterogeneous mosaic-like landscape of the Baltic amber source area in a coastal
setting. This heterogeneity allowed the existence of diverse animal and plant taxa
with different habitat preferences in close proximity to each other.

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