Supplement

S1: The Conservation status of the German flora

In Germany, protection and maintenance of biodiversity are based on (1) the national nature conservation legislation, (2) the red list of endangered species, and (3) the responsibilities in the context of the EU Habitat directive Natura-2000 (European Commission 2014) and EU wildlife trade regulations.

Legal protection, as the earliest instrument of biodiversity protection is based on a list of plant species for which trade, up-digging and picking are not permitted. Historically, the list of species has developed by recommendations from the public. Plant species were protected for their beauty, and not necessarily based on rarity.

The Red List of endangered species is based in the Law of Conservation which directs federal and state agencies to “observe” the status of “nature”. The Red Lists are an instrument to summarize observations (IUCU 2014: http://www.iucnredlist.org/) that are carried out by public administrations assisted by members of biological societies, by individual scientists, by an interested amateurs. The results are summarized by governmental institutions, and published in un-reviewed “reports”. Red Lists are legally not binding, but contain information to guide public awareness. Nevertheless, repeated observations allow a trend analysis of the conditions of nature. For example, the Red List of Thuringia, a state of Germany, states that the intensification of agriculture led to an increased deterioration of biodiversity of 0.3 units for all organisms, which is 38% of the change due to land abandonment (an increase 0.8). Thus, terminating earlier (moderate) management is worse for biodiversity of the open-land flora than intensification in already existing intensively used agricultural fields (Rote Listen Thüringens 2014, p24). For forests, the intensification of forest management led to 0.2% decrease of diversity, which is equal to the effects of termination of forest use (protection for wilderness) with 0.2% decrease in diversity under current conditions. Currently, moderate (sustainable) levels of land use best maintain organismic diversity, at least in Germany.

The responsibility for species is the latest conservation instrument resulting from the Habitats Directive of the EU, which is built around the Natura-2000 network and the existing system of species protection (European Commission 2014). It requests from individual nations to take the legally binding responsibility for future maintenance of certain habitats and key species (Gruttke 2004a, Welk 2002). The original definition was expanded, to include disjunct populations (Gruttke et al. 2004b).

Taking Germany as example, a total of 369 species are protected by law (Fig. S1). Only 16% of these protected species can be regarded as true forest species. The red list of endangered species (category 1 to 3) lists 712 species for Germany, with only 7% constrained to forests (Schmidt et al. 2011). There are additional 114 species which are “near threatened” (Red List category G), with 4% growing in forests. Germany claims responsibility for 301 plant species, with only 6% of these being associated with forests. The three classes of protection cover 1,044 species (37% of the flora excluding apomictics), of which 173 species grow in forests (50% for the forest flora, see also Fig. 1).

For the total flora of Germany all three categories of protection overlap by 54 species. In forests the overlap are 5 species. However, two of these five forest species are restricted to rock surfaces (Asplenium adulterinum growing on unforested serpentine rocks and Hymenophyllum tunbringense growing in unforested wet cracks of sandstone cliffs). Thus, only three true forest species remain that are protected, endangered and for which Germany has taken responsibility. These three remaining species are Chimaphila umbellata growing in sandy areas of the north-eastern German lowland and along the Rhine-Main-Danube rivers, Pulmonaria collina growing in SW-Germany and Central Thuringia, and Epipogium aphyllum which is rare but formerly more widely distributed.

References for S1

European Commission (2014): The Habitats Directive, last updated: 30/10/2014

//ec.europa.eu/environment/nature/legislation/habitatsdirective/index_en.htm#top-page. Accessed 5 November 2014

Gruttke H (2004) Grundüberlegungen, Modelle und Kriterien zur Ermittlung derVerantwortlichkeit für die Erhaltung von Arten mit Vorkommen in Mitteleuropa, eine Einführung. In: H Gruttke (ed) Ermittlung der Verantwortlichkeit für die Erhaltung mitteleuropäischer Arten. Naturschutz und Biologische Vielfalt 8:7-23

Gruttke H, Ludwig G, Schnittler M, et al. (2004) Memorandum: Verantwortlichkeit Deutschlands für die weltweite Erhaltung von Arten. Naturschutz und Biologische Vielfalt 8: 273-280

Huntley B (1996) Quaternary palaeoecology and ecology. Quaternary Science review 15:591-606

Kottek M, Grieser J, Beck C, Rudolf B, Rubel F (2006) World map of the Köppen-Geiger climate classification updated. Meteorologische Zeitschrift 15: 259-263

Kreeb KH (1983) Vegetationskunde. Ulmer vergal, Stuttgart, 331pp

Ludwig G, May R, Otto C (2007) Verantwortlichkeit Deutschlands für die weltweite Erhalung der Farn- und Blütenpflanzen: Vorläufige Liste. BfN-Skript 220: 102pp

Schmidt M, Kriebitzsch WU, Ewald J (2011) Waldartenlisten der Fran- und Blütenpflanzen, Moose und Pflechten Deutschlands. BfN-Skript 299, 109pp

Welk E (2002) Arealkundliche analyse und Bewertung der Schutzrelevanz seltener und gefährdeter Gefäßpflanzen Deutschlands. Schriftenreihe für Vegetationskunde 37:21-187

Fig. S1: The distribution of species between different protection categories. Nature conservation and red list: Korneck et al. 1996; Responsibility: Ludwig et al. 2007, Forest species category 1.1 and 1.2: Schmidt et al. 2011


S2: Geographic distribution of tree species

When comparing the Central European tree species with other regions of the world we only can rely on regional floras and their categorization as “trees”. Botanically these are plant species with a clear stem, and a branching crown elevated above the ground. This definition is independent of height, which is often taken as a parameter for structural analysis in vegetation surveys (Kreeb 1983). The morphology-based definition separates trees from shrubs, which inherently have multiple stems and a branching crown near the ground. Obviously, there are transitions, and some species listed in the following, e.g. Salix appendiculata, may be regarded more often as shrub in nature. Here we list Salix appendiculata as a tree, as it is listed in the Flora Europaea as tree (arborescent). This approach appears to be the only way to include the floras of other continents into our analysis, because the local floras are the only published documentation of these vegetations. It is promising to see, that using the flora-approach (Table 1) we also end up with 64 tree species for Central Europe as in Schmidt et al (2011).

Our flora-analysis is based on the Flora Europaea for Europe, the PLANTS database for eastern North America (http://plantsusda.gov/java/), and on Flora of China (http:// efloras.org/flora_page.aspx?flora_id=2) and the Flora of Japan (http://foj.c.u-tokyo.ac.jp/gbif/foj/) and for Korea using the Flora of China and of Japan. In this assessment it is crucial how the borders between the temperate region and the subtropical region are drawn (see Table 1). Based on the climate-classification of Köppen-Geiger (Kottek et al. 2006), Europe and Eastern North America differ in part from China. The Climate of Central Europe and of the Eastern USA is of the Cfb-type (warm temperate, fully humid, warm summer), but it changes into the Cfa-type (a: hot summer) in the interior and south of the USA, and the Dfb-type (D: snow, f: fully humid, b: warm summer) towards Southwest Canada, and into the Cfa or Csb-types (f: fully humid; s: summer dry) in the European Mediterranean region. In contrast, temperate China, Korea and Japan are for the largest part of the Cfa- and Cwa-type as in the more continental USA. In the continental part, China has a climate of the Cwb and Cwa-type (w: winter dry, a: hot summer). Thus, Huntley (1996) explains differences in plant biodiversity between China and Europe/USA not only by differing Pleistocene histories, but also by differences in present climates. Recently observed changes in the distribution of laurophyllous species in Switzerland, including the invasion of palms originating from subtropical China, may indicate a change in Sub-Mediterranean Europe climate towards the Cwa type as in China (Walther 1999). Under climate change, models predict a change into Csa climates for large areas in Western Europe and Cfa in central Europe (Rubel and Kottek 2010).

Table 1: Comparison of total broadleaved and coniferous species native to Central Europe, geographic Europe excluding the Mediterranean, and geographic Europe including the Mediterranean, as well as NE-America and temperate East Asia based on regional floras (see text). Conifers are printed in bold letters. Hybrids were excluded. The assessment of E-Asia by Röhrig (1991) is included as comparison. Central Europe includes Germany, Benelux states, Switzerland, Austria, Poland, Czech Republic, Slovakia, Hungary and Romania. Europe minus Mediterranean refers to geographic Europe excluding the Mediterranean region. We also refer to geographic Europe including the Northern Mediterranean region. NE-North America includes SE Canada (S-Ontario, Quebec, New Brunswick and Nova Scotia) and USA with North Carolina as southern border. E-Asia includes North China north of 25° to 30° latitude, excluding the southern subtropical provinces Fujian, Guangdong, Gunagxi, Hainan, Hunan, Jiangxi, Yunnan, Zehjiang, and excluding Taiwan, Honkong und Macau. Japan-Korea includes the northern Japanese islands of Hokkaido and Honshu and the Korean peninsula. The present investigation on the occurrence of tree species is compared with earlier enumerations by Röhrig and Ulrich (1991) for East Asia.

Family / Genus / Central Europe / Geographic Europe minus Mediterranean / Geographic Europe plus Mediterranean / NE-N-America / E-Asia / Röhrig-E-Asia
Altingiaceae / Liquidambar / 0 / 0 / 0 / 1 / 2 / 1
Anacardiaceae / Pistacia / 0 / 0 / 3 / 0 / 2 / 2
Aquifoliaceae / Ilex / 1 / 1 / 2 / 14 / 71 / 0
Betulaceae / Alnus / 2 / 3 / 3 / 4 / 8 / 14
Betulaceae / Betula / 2 / 2 / 2 / 10 / 19 / 36
Betulaceae / Carpinus / 1 / 2 / 2 / 1 / 25 / 25
Betulaceae / Ostrya / 0 / 1 / 1 / 1 / 2 / 3
Bignoniaceae / Catalpa / 0 / 0 / 0 / 2 / 4 / 4
Buxaceae / Buxus / 1 / 1 / 2 / 1 / 2 / 0
Cannabaceae / Celtis / 0 / 4 / 4 / 4 / 10 / 14
Cannabaceae / Pteroceltis / 0 / 0 / 0 / 0 / 1 / 1
Caprifoliaceae / Sambucus / 1 / 1 / 1 / 1 / 1 / 0
Cercidiphyllaceae / Cercidiphyllum / 0 / 0 / 0 / 0 / 1 / 2
Cornaceae / Cornus / 0 / 1 / 1 / 6 / 20 / 0
Cupressaceae / Cupressus / 0 / 0 / 1 / 0 / 5 / 0
Cupressaceae / Juniperus / 1 / 1 / 8 / 6 / 14 / 0
Cupressaceae / Chamaecyparis / 0 / 0 / 0 / 1 / 2 / 0
Cupressaceae / Thuja / 0 / 0 / 0 / 1 / 2 / 0
Davidiaceae / Davidia / 0 / 0 / 0 / 0 / 1 / 1
Ebenaceae / Diospyros / 0 / 0 / 0 / 1 / 13 / 25
Elaeagnaceae / Hippophae / 1 / 1 / 1 / 0 / 6 / 0
Euphorbiaccae / Sapium / 0 / 0 / 0 / 0 / 2 / 4
Fabaceae / Gleditsia / 0 / 0 / 0 / 2 / 3 / 7
Fabaceae / Cercis / 0 / 0 / 0 / 1 / 3 / 2
Fabaceae / Gymnocladus / 0 / 0 / 0 / 1 / 1 / 3
Fabaceae / Laburnum / 0 / 2 / 2 / 0 / 0 / 0
Fabaceae / Maackia / 0 / 0 / 0 / 0 / 4 / 3
Fabaceae / Robinia / 0 / 0 / 0 / 3 / 0 / 1
Fabaceae / Albizia / 0 / 0 / 0 / 0 / 8 / 10
Fagaceae / Castanea / 0 / 1 / 1 / 2 / 3 / 7
Fagaceae / Castanopsis / 0 / 0 / 0 / 0 / 27 / 5
Fagaceae / Cyclobalanopsis / 0 / 0 / 0 / 0 / 27 / 30
Fagaceae / Fagus / 1 / 2 / 2 / 1 / 4 / 7
Fagaceae / Lithocarpus / 0 / 0 / 0 / 0 / 41 / 47
Fagaceae / Quercus / 4 / 11 / 20 / 45 / 29 / 66
Juglandaceae / Carya / 0 / 0 / 0 / 12 / 3 / 4
Juglandaceae / Juglans / 0 / 1 / 1 / 4 / 3 / 4
Juglandaceae / Platycarya / 0 / 0 / 0 / 0 / 1 / 2
Juglandaceae / Pterocarya / 0 / 0 / 0 / 0 / 4 / 0
Lauraceae / Phoebe / 0 / 0 / 0 / 0 / 18 / 16
Lauraceae / Sassafras / 0 / 0 / 0 / 1 / 1 / 2
Magnoliaccae / Liriodendron / 0 / 0 / 0 / 1 / 1 / 1
Magnoliaceae / Magnolia / 0 / 0 / 0 / 7 / 10 / 50
Moraccae / Maclura / 0 / 0 / 0 / 1 / 1 / 1
Moraceae / Morus / 0 / 0 / 0 / 2 / 10 / 6
Nyssaceae / Nyssa / 0 / 0 / 0 / 4 / 1 / 2
Oleaceae / Fraxinus / 2 / 4 / 4 / 8 / 25 / 20
Oleaceae / Osmanthus / 0 / 0 / 0 / 1 / 13 / 10
Pinaceae / Abies / 1 / 2 / 5 / 2 / 22 / 2
Pinaceae / Larix / 1 / 1 / 1 / 1 / 10 / 0
Pinaceae / Picea / 1 / 1 / 1 / 4 / 20 / 0
Pinaceae / Pinus / 4 / 7 / 12 / 17 / 20 / 0
Pinaceae / Pseudotsuga / 0 / 0 / 0 / 1 / 2 / 0
Pinaceae / Tsuga / 0 / 0 / 0 / 2 / 6 / 0
Platanaceae / Platanus / 0 / 1 / 1 / 1 / 0 / 0
Rhamnaceae / Frangula / 1 / 1 / 1 / 1 / 0 / 0
Rhamnaceae / Paliurus / 0 / 0 / 0 / 0 / 4 / 5
Rhamnaceae / Rhamnus / 1 / 1 / 2 / 1 / 17 / 0
Rosaceae / Crataegus / 2 / 5 / 7 / 135 / 11 / 0
Rosaceae / Malus / 1 / 4 / 4 / 3 / 21 / 8
Rosaceae / Prunus / 3 / 6 / 6 / 13 / 8 / 59
Rosaceae / Pyrus / 2 / 7 / 11 / 0 / 13 / 5
Rosaceae / Sorbus / 4 / 4 / 4 / 4 / 53 / 18
Rutaceae / Phellodendron / 0 / 0 / 0 / 0 / 2 / 0
Rutaceae / Tetradium (Euodia) / 0 / 0 / 0 / 0 / 6 / 6
Salicaceae / Populus / 3 / 3 / 3 / 6 / 56 / 33
Salicaceae / Salix / 12 / 13 / 13 / 28 / 84 / 97
Sapindaceae / Acer / 5 / 9 / 10 / 11 / 99 / 66
Sapindaceae / Dipteronia / 0 / 0 / 0 / 0 / 1
Sapindaceae / Aesculus / 0 / 1 / 1 / 5 / 3 / 4
Scrophulariaceae / Paulownia / 0 / 0 / 0 / 0 / 6 / 10
Simaroubaceae / Ailanthus / 0 / 0 / 0 / 0 / 3 / 3
Simaroubaceae / Picrasma / 0 / 0 / 0 / 0 / 2 / 1
Styracaceae / Halesia / 0 / 0 / 0 / 3 / 1 / 1
Styracaceae / Sinojackia / 0 / 0 / 0 / 0 / 3 / 3
Tamariscaceae / Tamarix / 0 / 0 / 13 / 0 / 9 / 13
Taxaceae / Taxus / 1 / 1 / 1 / 0 / 3 / 0
Taxaceae / Torreya / 0 / 0 / 0 / 0 / 4 / 0
Theaceae / Stewartia / 0 / 0 / 0 / 2 / 5 / 8
Tiliaceae / Tilia / 2 / 4 / 5 / 2 / 19 / 20
Ulmaceae / Ulmus / 3 / 4 / 6 / 6 / 19 / 30
Ulmaceae / Zelkova / 0 / 0 / 1 / 0 / 3 / 3
Species / Sum / 64 / 114 / 169 / 398 / 990 / 833
Broad leaved / 55 / 101 / 139 / 363 / 879 / 835
Coniferous / 9 / 13 / 29 / 35 / 110 / 2
Genera / 28 / 36 / 40 / 52 / 78 / 59
Families / 16 / 21 / 23 / 28 / 37 / 41

References for S2