Biological Traits of Vascular Plants: A database.

Introduction

The data collection described in this paper is based on a literature compilation of biological traits from vascular plants. The first taxa considered have been recorded during surveys in an arable landscape in Southwest-Germany and in the Stuttgart municipal area. As more taxa are being worked on, the database is designed to be a ‘work in progress’. The complete file currently available is on the enclosed disk. The database is written in the dbase IVÒ -format that is compatible with many other applications.

The database should also to be viewed as a ‘work in progress’, because literature references are either lacking or vague for many biological features and for many species. Regarding the number of species, a complete review of the published literature for each of them was not practical. The present database therefore remains incomplete and, in part, unclear. In addition, many classifications are based on relatively few data or anecdotal information. Users are advised to check the indicated literature in order to evaluate the origin and quality of the data.

Biological data of plant species - from biological traits to the assessment for conservation

Of the several purposes that this database may be valuable for, just one shall be briefly addressed here. It concerns the assumption that the biological characteristics of an individual plant allow survival and reproduction in only a small subset of all environments, in adaptation to interactions with biotic and abiotic environmental conditions. This functional relationship should constitute the ‘success’ of plants at the sites where they grow (Schimper 1889, Drude 1913, Ellenberg 1950, Schulze & Chapin 1987, Keddy 1990, Solbrig 1993).

Plant species can be distinguished by many different biological features. Which of these is ecologically relevant at a given site, may become obvious if several species on this site represent a similar pattern of features (Grime et al. 1988). By comparing many different stands of vegetation along environmental gradients on a landscape scale, such patterns of similar biological features or functional groups can be revealed (Kleyer 1991).

In ecology applied to conservation, it is necessary to anticipate and assess changes of plant communities as a consequence of planned activities in the landscape. Direct or indirect effects of impacts or perturbations in landscapes (e.g. road construction, land reclamation or conservation management practices) are leading to modifications of physical conditions on sites facing such impacts (e.g. change of resource supplies or frequency of mechanical disturbance). If these changes are greater than the ability of the plants to compensate for them by plasticity, a succession risk becomes probable. Other species finding their optimum in the new environmental situation may competitively displace the present plants and alter the composition of the communities.

As plant dispersal is mainly passive, the arrival and subsequent establishment of particular plant species at a given site are subject to chance. It can only be predicted for indefinite time periods. Statements such as, "if this project is going to be realised, an individual of Cypress Spurge (Euphorbia cyparrissias) will arrive and become established here", are therefore questionable. However, if a functional relation between biological traits and environmental conditions could be demonstrated, functional groups that may be successful are predictable along with changes of the environment. The groups would consist of a fuzzy-set of species with similar biological characteristics ("the species may be either Cypress Spurge (Euphorbia cyperissias) or Yellow Bedstraw (Galium verum), but it is highly probable to have elongated rhizomes, scleromorphic leaves, low plant height etc.").

If the succession of functional groups can be predicted along with changes in the environmental conditions, two main advantages are gained for conservation and environmental evaluation purposes:

• Evaluation of the environmental situation that will be the result of the planning process (‘scenarios’). The actual procedure of assessment considers only the present situation as no prediction of future states is possible.
• Checking and inspection of the preceding planning statements after realisation (‘monitoring’).

It has often been recognised that the biological characteristics of an individual contribute to its probability to survive environmental changes (Cornelius & Meyer 1991, Given 1994). There is a vast body of literature dealing with environmental factors leading to extinction. In contrast, only a relatively small number of publications traces the relationship between environmental factors and plant species back to the biological reasons of extinction. Such investigations are offering the following advantages:

• A more coherent view on the causes of threat: The biological factors (e.g., dispersal, expansion, reproduction, physiology, regeneration, genetics; the ‘dependant variables’) are often either neglected or confounded with the environmental factors (the ‘independent variables’). However, to become a threat, a specfic type of habitat modification or curtailment must match a specific set of biological features. For instance, nutrient enrichment becomes a threat only if it affects plants characterised by low vertical expansion. Those plants may become overtopped by taller plants. If the plants affected are already tall and fast growing or if they are able to exploit temporal niches in such communities, nutrient enrichment may not be a threat to them. With respect to threat, environmental and biological factors are most often paired. Just some of all possible pairs may lead to endangerment. It is then necessary to sort out the pairs of environmental and biological factors caused by recent changes of the environment from the evolutionary consequences of vicariance, genetic depletion or taxon age (Fiedler 1986).
• An opportunity to scale the degree of threat in relation to the degree of environmental change: Criteria such as rarity draw attention towards species with low population numbers and a limited geographical range. However, it is impossible to infer from rarity to which threshold of environmental change populations of these species may survive or become locally extinct. Consider the construction of a road. Along the route itself, habitats are destroyed and all local populations face extinction. In the neighbourhood, growth sites prevail but may be subject to slight environmental changes (e.g., modifications of the soil water table, the soil nutrient content or the mesoclimate). The persistence of functional groups in the neighbourhood of the route depends upon the adaptive capacity to survive and regenerate under the modified environmental conditions. Conservation measures or rejection of the planned activities would be necessary if the impact is greater than the adaptive capacity of the functional groups affected.

Detailed comparative studies are necessary to describe the relationships between environmental factors and the biological traits of plants, both on the level of the population and of the community. This collection may be a resource for such studies.

Organisation of the database

Attempts to describe plants with respect to morphology and structure can be dated back to the Greek philosophers, especially to Theophrastos (371-285 BC). His writings are the earliest preserved with a detailed classification of different root, leaf or flower forms (Mägdefrau 1992).

Beginning with the works of Alexander von Humboldt (1806, 1815-25), classifications of growth forms and life forms reached their peak by the end of the 19th century (see reviews in Du Rietz 1931, Barkman 1988). Examples for a recent application of the life-form-system following Ellenberg & Mueller-Dombois (1974) are Schiefer (1980), Box (1981), Styner & Hegg (1984), Konold (1984) and Briemle & Schreiber 1994. Other attempts (Schmidt 1981, Tatoni 1994) use the life-form-system of Raunkiaer (1910) or individual classifications of plant morphology (Dansereau 1951, Gimmingham 1951, Hallé et al. 1978, Barkman 1979, 1988, Komarkova & McKendrick 1988, Day et al. 1988, Kleyer 1991, Guillén et al. 1994, Pettit et al. 1995).

Considering its agglomerate-hierarchical structure and its physiognomic direction, the life form system of Ellenberg & Mueller-Dombois (1967) remains in the tradition of earlier life- and growth-form-systems (e.g., Grisebach 1872, Warming 1884, 1909, Drude 1913, Braun-Blanquet 1928, Du Rietz 1931). All these groupings attempt to categorise each plant species with one single class that linearly combines all the individual traits the classification considers. An example from Ellenberg & Mueller-Dombois (1974) is ‘medium-sized scapose summer-green rhizome geophyte’. Within the life-form ‘geophytes’, this classification already offers 216 combinations of the four characteristics height, shoot habit, phenology and ground axis. The obvious disadvantage is that the number of combinations is rapidly multiplied by incorporating new features in such systems. The diverse authors could not come to agreement which features should be omitted and which should be preferred (Barkman 1988, Dierschke 1994).

In this database, all biologial characteristics are arranged side by side without building linear combinations of all categories for all characteristics (see Fitter & Peat 1994, Hodgson et al. 1995, Kleyer 1991). The grouping of plants with similar biological characteristics could be done with the help of a cluster analysis (see Grime et al. 1988)

Limitations of the database

The biological characteristics are mainly related to the morphology and the life cycle of plants. Many features relevant for dispersal, germination, establishment, expansion, regeneration and reproduction could not be taken into account as data are lacking for most taxa. Moreover, the characteristics considered so far are useful only for the evaluation of plants on terrestrial sites. If plants on subhydric or hydric sites are to be investigated, more features should be considered (see Den Hartog & van der Velde 1988, Wiegleb 1991). Traits associated with herbivory are also lacking.

Established classifications of plant traits have been adopted, mainly from Grime et al. (1988). If any established classification could not be used for the purpose of this database, parallels and differences are indicated.

Subdivision of variable traits

Many plant traits may show either ecotypic or continuous variation according to environmental conditions. In general, shapes of flowers or leaves vary less than, for instance, the number of seeds produced by a certain plant. By subdividing variable traits into classes of different levels, any possible variation ranging between the limits of a given level is rendered zero. If the subdivision is reduced to a very low number of levels, the probability that the environmental variation is fully absorbed within the level limits will rise. Plant traits considered highly variable were therefore subdivided in a low number of class levels. For instance, diaspore number was subdivided in just four levels (1 - 1000, 1000 - 10000, > 10000 diaspores per plant, diaspores normally absent).

Stöcklin (1992) proposed to regard the degree of environmental plasticity itself as a plant trait. However, this degree can differ for different traits of one plant. Plasticity expresses the biological scale of each trait rather than a trait of its own. The representation of fuzziness offers the opportunity to incorporate an estimation of plasticity into the classification (see below).

Incompleteness and fuzziness

For every plant feature, a datafield (‘...._lit’) indicates the literature reference. The references are labelled with numbers. The corresponding publication is cited in the bibliographic database, also on the disk (see below). All classifications without literature reference are estimations based on field observations by the author.

If no information was available for a certain plant, datafields are labelled with ‘...._nd’, meaning ‘no data’. Information is mainly lacking for traits associated with the generative reproduction of plants, as laborious experimental approaches are often necessary to study them.

If the membership of a plant to a single category of a given feature is uncertain, several categories are indicated (‘....’, ‘....2’, ‘....3’). For each of these categories, the percentage membership (0 - 100 %) of the plant to the category was estimated (‘fuzzy coding’, ‘....1mem’, ‘....2mem’, ‘....3mem’). For instance, the achenes of Cirsium arvense are dispersed by means of a readily-detached pappus and also by agricultural practices (Korsmo 1930, Müller-Schneider 1986, Grime et al. 1988). Dispersal is indicated in field DIS as "DIS_PAPP" (Diaspores with umbrella-like structures, i.e. pappus) and in field DIS2 as "DIS_MAN" (Anthropochory). Membership to DIS is estimated with 75 % in field DIS1_MEM and membership to DIS2 with 25% in field DIS2_MEM. The literature references are indicated in the field DIS_LIT as "8" (Grime et al. 1988), "9" (Müller-Schneider 1986) and "74" (Korsmo 1930).

Dividing the membership between several categories avoids arbitrary assignments to one category if the real membership is uncertain. It is often necessary when either

• literature references comprise contrasting or vague statements with respect to a certain feature, or,
• a plant displays variation over several categories of a certain feature.

Further evaluation, e.g., computation of spectra for a certain community, may proceed like the qualitative computation of indicator values (Ellenberg et al. 1991). The estimation of the membership is then used as a weighting factor. As abundance data are correlated with morphological traits that refer to the vertical and lateral expansion of plants, presence-absence data should be preferred.

The author is grateful for any comments on errors, additional references or for any information serving to update the database.

Organisation of the bibliographic database

The datafield ‘Label’ refers to the number of the reference. The fields ‘Author’ and ‘SEC_AUTHOR’ indicate the first author and all others, respectively. ‘YEAR’ contains the year of the publication, ‘TITLE’ the title of the publication. If the article belongs to an edited book, then the field ‘EDITOR’ refers to the editor and the title of the book. If it was published in a journal, ‘JOURNAL’ contains name and volume of the journal. Publisher and city of publication are indicated in the fields ‘PUBLISHER’ and ‘CITY’. The first and last page numbers are in the field ‘PAGES’.

Explanation of tables

Species

The nomenclature is adopted from the database of Ellenberg et al. (1993). Their database contains information on indicator values, geographical distribution, status and conservation needs. Both datasets can easily be merged by using the generic name and the species name as related items. The database contains both in separate datafields as in Ellenberg et al. (1993). The code number of Ehrendorfer (1973) is also adopted from that database.

The datafield ‘STAGE’ has been included to distinguish woody plants in different growth stages. ‘3’ indicates a plant at maturity. This applies to all herbaceous species, trees and shrubs. If a tree occurs as a sapling, a ‘2’ has been assigned. A ‘1’ has been assigned for a seedling. For plants denoted with ‘2’ or ‘1’, reproductive traits or growth forms are different from the mature plant. This division may be useful as managed herbaceous plant communities sometimes include seedlings or saplings of woody plants that never reach maturity.

1. Features of dispersal, germination and establishment

Dispersal of diaspores DIS

Autochory

Self-Dispersal

Luftensteiner (1982): Autochor; Müller-Schneider (1986): Autochor-Blastochor, Autochor-Ballochor; Grime et al. (1988): UNSPcw.

• Explosive discharge (ballists) DIS_EXPL

Dispersal by gravity

Luftensteiner (1982): Barochor, Semachor; Müller-Schneider (1986):

Boleochor, Hydrochor-Ombrochor ; Grime et al. (1988): WINDm, WINDc.

• Heavy diaspores - falling DIS_FALL
• Light diaspores - shed DIS_SHED
• Bulbils DIS_BULB

Allochory

Dispersal by wind

Luftensteiner (1982): Anemochor-Pterochor, Anemochor-Pogonochor,

Anemochor-Lophochor, Anemochor-Saccochor, Anemochor-Cyclochor;

Müller-Schneider (1986): Anemochor-Cystometeorochor, Anemochor-

Pterometeorochor, Anemochor-Trichometeorochor, Anemochor-Chamaechor;

Grime et al.(1988): WINDp, WINDw.

• Winged diaspores (including twisted bristles etc.) DIS_WING
• Diaspores with umbrella-like structures (i.e. pappus) DIS_PAPP
• Plumed diaspores DIS_PLUM
• Balloon-like diaspores DIS_BALL
• Rollers DIS_ROLL

Dispersal by water

Luftensteiner (1982): - ; Müller-Schneider (1986): Hydrochor-Nautochor,

Hydrochor-Bythisochor; Grime et al. (1988): AQUAT.

• Transport by water currents (floating) DISFLOAT
• Turiones DIS_TURI

Dispersal by animals

• Fleshy berries DISBERRY

<dir> <dir>

Luftensteiner (1982): Zoochor-Sarcochor; Müller-Schneider (1986):
Zoochor-Endochor; Grime et al. (1988): ANIMi, ANIMn.

</dir> </dir>

• Nuts DIS_NUT

<dir> <dir>

Luftensteiner (1982): Zoochor-Sarcochor; Müller-Schneider (1986):

Zoochor-Dysochor; Grime et al. (1988): ANIMn.

</dir> </dir>

• Elaiosomes DIS_ELAI

<dir> <dir>

Luftensteiner (1982): Zoochor-Elaiosomochor; Müller-Schneider

(1986): Myrmechor; Grime et al. (1988): ANIMe.

</dir> </dir>

• Burrs DIS_BURR

<dir> <dir>

Luftensteiner (1982): Zoochor-Acanthochor; Müller-Schneider (1986):

Zoochor-Epichor; Grime et al. (1988): ANIMa, ANIMb.

</dir> </dir>

• Secretion of Mucilage DIS_MUCI

<dir> <dir>

Luftensteiner (1982):Myxochor; Grime et al. (1988): ANIMm

</dir> </dir>

Dispersal by man

• Anthropochory DIS_MAN

<dir> <dir>

Luftensteiner (1982): N.B.; Müller-Schneider (1986): Hemerochor-

Ethelochor, Hemerochor-Speirochor, Hemerochor-Agochor; Grime et al.

(1988): UNSPag.

</dir> </dir>

• Diaspores normally absent DIS_NOS
• No data available DIS_ND

Number of diaspores per shoot NUM

The number of diaspores per shoot is considered to be highly variable (Salisbury 1942, Harper 1977). Plants, especially annuals, may produce very large amounts of diaspores, if they grow free of competition and with optimal resource supply. On the other hand, production of diaspores can be considerably reduced in case of environmental stress or competition (Myerscough & Marshall 1973). To compensate for at least a part of this environmental variability, only four classes were set up.

The cited numbers of diaspores mostly refer to field tests (e.g. Korsmo 1930, Salisbury 1942). Amounts of diaspore production on natural sites are compiled in Perttula (1941).

In case of clonal plants the term ‘shoot’ refers to a ‘ramet’. Unfortunately, many authors indicate numbers of diaspores per ‘plant’. It then remains uncertain if the genet or the ramet is meant.

• 1-1000 NUM_1000
• 1001-10000 NUM10000
• More than 100000 NUM_MAX
• Diaspores normally absent NUM_NOS
• No information available NUM_ND

Weight of diaspores MASS

The classification follows Grime et al. (1988).

• Too small to be measured easily. MASS_MIN
• Weight <= 0.2 mg MASS_02
• Weight 0.21 - 0.5 mg MASS_05
• Weight 0.51 - 1.00 mg MASS_10
• Weight 1.01 - 2.00 mg MASS_20
• Weight 2.01 - 10.00 mg MASS_100
• Weight > 10.00 mg MASS_MAX
• Diaspores normally absent MASS_NOS
• No information available MASS_ND

Shape of diaspores FORM

The classification follows Grime et al. (1988).

• Length/breadth ratio < 1.5 FORM_MIN
• Length/breadth ratio 1.5 - 2.5 FORM_25
• Length/breadth ratio > 2,5 FORM_MAX
• Diaspores normally absent FORM_NOS
• No information available FORM_ND

Diaspore bank longevity LON

The categories were set up according to Bakker (pers. comm.) and Hodgson et al. 1995 (following an unpublished database of K. Thompson, J.P. Bakker and R. Becker; see also Bakker 1989).

• Transient: diaspores rarely persisting for more than one year LON_TRAN
• Short term persistent: seeds persisting for more than one
  year but usually less than five years LON_SPER
• Long-term persistent: seeds persisting for at least five years,
  and often much longer LON_LPER
• Diaspores normally absent LON_NOS
• No information available LON_ND

Temperature required for germination GT

The classification follows Lauer (1953). It refers to plant species, whose germination requirements have been identified by laboratory experiments.

• Germination at high temperatures GT_HIGH
  (Min. 20-25°C, Opt. 35-40°C, Max. 35-40°C)
• Germination at a broad range of temperatures,
  but optimum is high GT_HIOPT
  (Min. 5°C, Opt. 24-30°C, Max. 35-40°C)
• Germination at intermediate temperatures GTMEDIUM
  (Min. 2-5°C, Opt. 13-20°C, Max. 35°C)
• Germination at a broad range of temperatures,
  but optimum is low GT_LOOPT
  (Min. 2-5°C, Opt. 7-13°C, Max. 25-30°C)
• Germination at low temperatures GT_LOW
  (Min. 2-5°C, Opt. 2-5-7(-13)°C, Max. 13-20°C)
• Germination at a broad range of temperatures GT_BROAD
  (Min. 2-5°C, Opt. - , Max. 35°C)
• Diaspores normally absent GT_NOS
• No information available GT_ND

Seasonal time of germination GS

If the information originates from experiments or phenological observations in the field, the following classification was used:

• Early spring GS_EARLY
• Spring GS_SPRIN
• Early summer GS_EASUM
• Spring and summer GS_SPSUM
• Summer GS_SUM
• Autumn GS_AUT
• Spring and autumn GSAUTSUM
• Shortly after being shed GS_SHED
• Diaspores normally absent GS_NOS
• No information available GS_ND

2. Features concerning the vegetative expansion of plants

Plants are often described as modular organisms, the modules (termed ramets) being temporary structures of the plant as a whole (termed genet; Harper 1981, Watkinson & White 1985). Following this concept, each single ramet is a combination of the units root, ground-axis and stem with branches and leaves. The units may differ in their stature from species to species. Unitary genets are characterised by one combination of root, ground-axis and shoot. Clonal genets are conceptualised as an iteration of this combination.

2.1 Features of the ramet

Growth form of the shoot ST

• Lianas ST_LIANA
• Stem erect ST_ERECT
• Stem ascending to prostrate STASCPRO
• Stem prostrate ST_PROST
• Epiphytes ST_EPI
• Aquatic plants, floating ST_FLOAT
• Aquatic plants, submerged STSUBMER
• No information available ST_ND

Branching BRA

The classification of branching refers only to the aerial shoot. Shoots that branch near the cotyledons (epicotyl) were classified as ‘basiton’. Shoots that branch below the cotyledons (hypocotyl) were assigned to the class ‘Unitary individuals with several shoots’ in the category ‘Growth form of the genet ‘.

• Without branching BRA_NO
• Distal branches are growing more vigorously (akrotony) BRA_AKRO
• Branches are distributed regularly all the way up the
  stem (mesotony) BRA_MESO
• Proximal branches are growing more vigorously (basitony) BRA_BASI
• No information available BRA_ND

Woodiness WOO

• Woody WOO_WOO
• Woody at base WOO_BAS
• Grasses WOOGRAS
• Herbs WOOHERB
• No information available WOO_ND

Shoot height HIGH

• < 100 mm HIGH_MIN
• 101 - 299 mm HIGH_03
• 300 - 599 mm HIGH_06
• 600 - 999 mm HIGH_09
• 1.0 - 1.5 m HIGH_15
• 1.6 - 3.0 m HIGH_30
• 3.1 - 6.0 m HIGH_60
• 6.1 - 15.0 m HIGH_150
• > 15.1 m HIGH_MAX
• submergent or floating HIGH_SUB
• variant HIGH_VAR

Life form (sensu Raunkiaer) LF

Classification and data from Ellenberg et al. (1991)

• Therophytes LF_THERO
• Geophytes LF_GEO
• Hemikryptophytes LF_HEMI
• Herbaceous chamaephytes LF_HCHAM
• Woody chamaephytes LF_WCHAM
• Nanophanaerophytes LF_NANOP
• Phanaerophytes LF_PHAN
• Hydrophytes LF_HYDRO
• Hygrophytes LF_HYGRO
• No information available LF_ND

Leaf distribution along the stem LEAF

• Leaves only proximal (rosette) LEAF_ROS
• Largest leaves proximal (semi-rosette) LEAFSEMI
• Leaves distributed regularly all the way up the stem LEAF_REG
• Shoot scarcely foliated, stem and twigs assimilating. LEAF_NO
• Epiphytes, submerged or floating aquatic plants LEAF_ESF
• No information available LEAF_ND

Leaf anatomy ANA

Classification and data from Frank et al. (1990), following the dataset of Ellenberg (1979).

• Mesomorph ANA_MESO
• Scleromorph ANA_SCLE
• Hygromorph ANAHYGRO
• Helomorph ANA_HELO
• Leaf-succulent ANA_SUCC
• Hydromorph ANAHYDRO
• No information available ANA_ND

Leaf phenology PHE

Classification and data from Ellenberg et al. (1991).

• Evergreen PHE_EVER
• Hibernal (green from autumn to spring) PHE_WINT
• Aestival (green mainly in summer) PHE_SUMM
• Vernal (green mainly in spring) PHE_SPRI
• No information available PHE_ND

Leaf size SIZE

The classification follows Barkman (1979).

• Bryophyllous (< 0.04 cm²) SIZE_BRY
• Leptophyllous (0.04 - 0.2 cm²) SIZE_LEP
• Nanophyllous (0.2 - 2 cm²) SIZE_NAN
• Microphyllous (2 - 20 cm²) SIZE_MIC
• Mesophyllous (20 - 100 cm²) SIZE_MES
• Macrophyllous (100 - 500 cm²) SIZE_MAC
• Megaphyllous (> 500 cm²) SIZE_MEG
• No information available SIZE_ND

2.2 Features of the ground-axis and the roots

Growth form of the ground-axis RT

Referring to Kutschera & Lichtenegger (1982, 1992), those parts of a plant that generate new aerial shoots near or below the soil surface will be termed a ground-axis. The classification of the ground-axis follows Kutschera & Lichtenegger (1982, 1992) and Cannon (1949). If ground-axis growth forms are analogous in relation to storage and lateral expansion, they were assigned to the same class. No differentiation was made with respect to homologous variation, e.g. primary vs. adventitious root systems.

To organise groups as different as trees, shrubs, herbs, monocotyledons and dicotyledons in a simple classification system, some compromises were necessary.

Subterranean rhizomes are divided into those being elongated and thin and those being short and stout. Within the class of elongated and thin rhizomes, a division may be useful that resembles the distinction between stolons and runners as above-ground structures (see Leakey 1981). The first group is characterised by very elongated plagiotropic internodes at the proximal section, while at the distal end, with the beginnings of their orthotropic orientation, the internodes are shortened to the forming of a rosette (‘Ausläufer’, Troll 1937-1943). Here, most adventitious roots emerge from the nodes and spontaneous vegetative multiplication is possible. The other group of elongated and thin rhizomes has internodes of a more uniform length and roots regularly distributed along the plagiotropic shoots (‘Kriechsprosse’, Troll 1937-1943). Older parts of the rhizomes in this group may decay continuously (Kutschera & Lichtenegger 1992), which then results in fragmentation of daughter plants. Examples for plants of the first group are Poa compressa, Carex flacca and Ononis repens, examples for plants of the second group are Teucrium chamaedrys or Galium verum (Kahne 1966). Many transitions are found between the two groups (Kutschera & Lichtenegger 1992). Both groups were classified as having the same ground-axis growth form, but their distinction remains relevant to assess the type and frequency of vegetative regeneration.

As ‘Kriechsprosse’, short and stout rhizomes may decay, starting from the old proximal section. If decaying proceeds towards a branch junction, the rhizome plant will become fragmented into separate individuals.

A tussock ground-axis is not only associated with grasses. Herbs were assigned to this class if their ground-axis is compressed and relatively thin and if its orientation is plagiotropic-orthotropic. For instance, basal perennial shoots may be pulled below the soil surface by proximal contractile roots and adventitious roots formed. A ring of shoots with roots results, growing in a tussock fashion.

Mühlberg (1967) classified tussock grasses as loosely and densely tufted forms. Loosely tufted grasses are tillering within the section of the subterranean short (compressed) internodes and within the section of the near-surface elongated internodes. Therefore, such grasses are classified as ‘Short and thin ground-axis’ concerning the feature ‘Growth form of the ground-axis’, and ‘Basitony’ concerning the feature ‘Branching’ of the aerial shoot.

Densely tufted grasses are branching only within the section of the subterranean short internodes (Mühlberg 1967). Such species were classified as ‘Without branching’ with respect to the aerial shoot. Similar groupings were made for rhizomatous grasses with or without shoot branching.

As shrubs consist mainly of a primary tap root and of shoots emerging near the cotyledons, they were assigned to the classes ‘Short and thick ground-axis’ (‘Growth form of the ground-axis’) and ‘Basitony’ (‘Branching of the aerial shoot’). Trees were treated similarly, but grouped as ‘Acrotony’ or ‘Mesotony’. Differences between shrubs or trees and herbaceous species are obvious from the features ‘Woodiness’ and ‘Plant height’.

If aerial shoots of species like Rubus spp. or Rosa spp. bend under their own weight down to the soil surface, adventitious roots are formed at the touching part. When the parent shoot decays, an independent plant may grow up. This feature will be called ‘Bending shoots’.

• Ground-axis orthotropic, thin. A single basal shoot. RT_1POL
• Ground-axis orthotropic, short and stout. A bulb, a corm,
  a stem tuber or a tap root tuber. Several basal shoots
  (i.e., by splitting of the orthotropic ground-axis). RT_1TUBE
• Ground-axis plagiotropic, short and thin. A tussock. RT_TUSS
• Ground-axis plagiotropic, short and thick. A stolon tuber,
  a rhizome tuber, a root tuber or a stout rhizome. RT_RHIZ
• Ground-axis elongated, thin, above surface. Runners
  and stolons. RT_STOL
• Bending shoots. RT_BEND
• Ground-axis elongated, thin, below surface (thin rhizomes). RT_ELON
• Ground-axis elongated, thin, deeply below surface.
  Deep thin rhizomes and suckers developed from deep root
  buds. RT_DEEP
• Epiphytes, submergent or floating plants RT_ESF
• No information available RT_ND

Root depth DEEP

• Down to 50 cm deep DEEP_05
• Down to 100 cm deep DEEP_1
• Deeper than 100 cm DEEP_MAX
• No information available DEEP_ND

2.3 Features of the genet

Growth form and lateral expansion CLON

• Unitary with a single shoot CLONUNI1
• Unitary with several shoots, branching at the hypocotyl. CLONUNIM
• Clone, subterranean expansion, very compact (some
  centimetres). Small tussocks of densely tufted grasses,
  clones generated through splitting of a stem tuber or a
  tap root tuber. CLONSMIN
• Clone, subterranean expansion, compact (many
  centimetres to some decimetres). Stout rhizomes, small
  and thin rhizomes, loosely tufted tussocks. CLONSCOM
• Clone, subterranean expansion, with a diameter ranging
  from several decimetres to some meters. Elongated thin
  rhizomes or shoots from root buds. CLONSMAX
• Clone, expansion above soil surface, compact (many
  centimetres to some decimetres). Small stolons and
  runners. CLONACOM
• Clone, expansion above soil surface, with a diameter ranging
  from several decimetres to some meters. Elongated stolons
  and runners. CLONAMAX
• No information available CLON_ND

3. Features of generative reproduction and vegetative regeneration.

Period of flowering FP

• Starting in spring, flowering period less than 3 months. FP_SPRIS
• Starting in spring, flowering period more than 3 months. FP_SPRIL
• Starting in early summer, flowering period less than 3
  months. FP_ESUMS
• Starting in early summer, flowering period more than 3
  months. FP_ESUML
• Flowering in late summer or autumn. FP_SUMAU
• No information available FP_ND

Seed shedding period SP

• Starting in early summer, seed set within less than
  3 months. SP_ESUMS
• Starting in early summer, seed set may take more than
  3 months. SP_ESUML
• Starting in late summer, seed set within less than 3 months. SP_LSUMS
• Starting in late summer, seed set may take more than
  3 months. Some seeds are retained on the plant during
  winter. SP_LSUML
• No information available SP_ND

Life cycle LC

• Summer annual LC_SUMAN
• Winter annual LC_WINAN
• Biennial LC_BIENN
• Monocarpic perennial LC_PERMO
• Polycarpic perennial LC_PERPO
• No information available LC_ND

Pollination POL

Allogamy (sexual, cross-pollination)

• Insect-pollinated POL_INS
• Wind-pollinated POL_WIND
• Water-pollinated POL_WAT
• Autogamy (sexual, self-pollination, including cleistogamy) POL_AUTO
• Apomixis (asexual) and heterogamy (subsexual). POL_APO
• No information available POL_ND

Age at first flowering TREP

Many records concerning this feature originate from experiments, mostly seed sowings in plot experiments. Investigations of plants at natural sites are rare. Apparently, the vegetative period without flowering is much longer in natural communities than in experimental situations (compare for instance records from Pertulla 1941 and Korsmo 1930 for the Scandinavian region).

• Less than 3 months TREP_03
• 3 months to 1 year TREP_1
• 1 to 2 years TREP_2
• 2 to 3 years TREP_3
• 3 to 6 years TREP_6
• 6 to 15 years TREP_15
• 15 to 30 years TREP_30
• More than 30 years TREP_MAX
• No diaspores developed TREP_NOS
• No information available TREP_ND

Type of vegetative multiplication and regeneration VEG

Many plant species are capable of forming buds to build up new shoot systems. Buds may be found at a stolon, a tuber, a rhizome, a root or at the hypocotyl. Detachment of daughter plants involves adventitious rooting and fragmentation of the connecting plant tissue. Vegetative multiplication happens either only in the case of physical damage or as part of the normal life cycle, by decay of connecting tissue or abscission of bulbils. Concerning the latter case, a division is suitable between plant species that form independent daughter plants within a short period and those where the connection between ramets is retained for a longer time period.

• Without vegetative multiplication and regeneration. VEG_NO
• Spontaneous vegetative multiplication, connection to the
  parent plant only for a short time period (one or two years). VEGCLONS
• Spontaneous vegetative multiplication, connection to the
  parent plant is retained for a longer time period (more than
  two years). VEGCLONL
• Bulbils, turions, false vivipary. VEG_PROP
• Vegetative multiplication by regenerative buds following
  damage. VEG_BUD
• No information available VEG_ND

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