Middle Miocene palynoflora of the Legnica lignite deposit complex ...

as xylitic brown coal – from resin-containing
coniferous trees was formed. This coal is dark
and contains a lot of wood and bark remains
(Teichmüller 1958, Neuy-Stolz 1958).
These swamp forests were wide-spread
in Europe during the Oligocene to Pliocene
period. In the Polish Lowland they had most
favourable conditions in the Early and Middle
Miocene. Presently, similar forests occur in
the Mississippi River delta, Florida, Georgia,
North Carolina, and the Gulf of Mexico coast.
In south-eastern China (Canton, Hainan) forests
with Glyptostrobus pensilis grow (Wang
1961, von Jux 1966, Kac 1975, Mai 1981).
Today swamp forests grow in stagnant
water-bodies that are nearly fi lled with sediments
(sloughs) or in areas where water is
impounded behind the river levee and remains
for much of the year. The principal species are
Taxodium distichum, Nyssa aquatica, and N.
ogeche (northern Florida and southern Georgia).
In the coastal lowland also Taxodium
ascendens and Nyssa sylvatica (including var.
bifl ora), as well as Ilex myrtifolia grow (Knapp
1965, Kac 1975, Barnes 1991). Pinus caribaea,
Fraxinus profunda, and F. caroliniana could
also play a considerable role in these forests
(Hall & Penfound 1943). Associated with the
swamp forests are valleys, in which many species
of the swamp forests have their dominant
role. For example on the Dismal Swamps in
both types of forests Acer rubrum plays a signifi
cant role. Besides there occur Fraxinus
caroliniana, rarely Quercus phellos, Magnolia
virginiana, Ilex opaca, Carpinus caroliniana,
Salix nigra, Alnus rugosa, Liriodendron tulipifera,
Liquidambar styracifl ua, and others.
There also grow climbers Vitis rotundifolia,
V. labrusca, Ampelopsis arborea, Rhus radicans,
Smilax rotundifolia, S. walteri, and others.
Along ditches and in open places Arundinaria
gigantea (=A. macrosperma), a bamboo
grass up to 5–6 m high, is frequent. Herbs are
very rare – Boehmeria cylindrica (Urticaceae),
Polygonum arifolium, and Aster difusus are
some of them. Such ferns as Osmunda regalis,
O. cinnamomea, Polypodium polypodioides
(incanum), and Woodwardia virginica are frequent
in some places (Kearney 1901).
In Florida there occur cypress swamps predominated
by Nyssa sylvatica, Taxodium distichum,
and Salix caroliniana as well as swamp
hardwoods with Acer rubrum, Nyssa sylvatica,
and Taxodium distichum (Crumpacker
69
et al. 2001), accompanied by Fraxinus pennsylvanica,
F. caroliniana, Carya aquatica,
Persea borbonia, Magnolia virginiana, Ilex
cassine, Juniperus virginiana, and Sabal palmetto
(Hofstetter 1983, Abbott & Judd 2000),
as well Morus rubra, Quercus laurifolia, and
Rhus copallinum (Willard et al. 2004). Similar
forests also grow in Louisiana (Neyland et al.
2000).
RIPARIAN FOREST
Along riversides and streams favourable
conditions existed for riparian forests dominated
by Liquidambar, Carya, Ulmus, Salix
as well as Alnus, Acer, Celtis, Fraxinus, Pterocarya,
Juglans, Quercus, Staphylea, and
Itea, accompanied by climbers Parthenocissus
and Vitis. Nowadays similar plant communities
occur among others in the Atlantic zone of
North America as well as in the Tierra Templada
in Central America (Mai 1981). Riparian
forests in the eastern part of North America
are distinctly richer than European ones.
Among them elm–maple riparian forests, with
Acer saccharinum, A. negundo var. violaceum,
and Ulmus americana, accompanied by Platanus
occidentalis and Aesculus glabra, have the
great species diversity. In these forests such
climbers as Parthenocissus quinquefolia and
Smilax herbacea play an important role. There
also occur birch–alder, poplar and, the nearest
the water, willow riparian forests. Towards
the south they are replaced by Quercus–Fraxinus–Carya
forests (Podbielkowski 1987a). In
the Mississippi Alluvial Plain grow forests
dominated by Liquidambar styracifl ua, Acer
rubrum, ash species (predominantly Fraxinus
pennsylvanica), Acer saccharum, Nyssa
aquatica, Carya species (such as C. cordiformis),
Ulmus americana, oak species (such
as Q. rubra), Aesculus discolor, Fagus grandifolia,
Populus deltoides, Celtis laevigata,
Platanus occidentalis, Tilia americana, Ilex
decidua, Cornus foemina, C. fl orida, Carpinus
caroliniana, Diospyros virginiana, Liriodendron
tulipifera, Salix nigra, and Smilax species
(Robertson et al. 1978).
Penfound (1952) recognized four types of wet
forests, growing on soils which are inundated
for only short periods during the growing season:
1. Salix nigra and S. exigua – fl oodplains
having deepest water and longest periods of
inundation of all shallow swamps; 2. Quercus