**2.3 The therophyte vegetation**

#### **2.3.1 Class** *Stellarietea*

The plant communities that have mainly therophyte species are referred to the class *Stellarietea*, and they are characterised by an annual cycle and reproduction by seed (Rivas Martinez et al., 2002).

This syntaxon includes phytocoenoses of commensals of annual-seeded crops, as both autumn to winter and spring to summer, and initial and immature grasslands that are seen under conditions of recurring disturbance, mainly by man. This disturbance can be caused by herbicides or by movement or removal of the surface layer of the soil.

In a serial context, the class *Stellarietea* occupies the first evolutionary step. The phytocoenoses of this syntaxonomic unit take on pioneering characters and tend to be the first to grow on bare substrata. In these communities, exotic species or species with a large

Environmental Evaluation and Monitoring of Agro-Ecosystems Biodiversity 339

 *Thero-Brometalia*: This includes the nitrophilous-ruderal associations of a xerothermophilous type that are limited to Mediterranean and Submediterranean territories. These coenoses are usually found where there are high nutrient concentrations in the

The class *Polygono-Poetea* is diffuse throughout the World and includes the vegetation typologies that are characteristic of habitats that are compacted. It is linked to humanised and strongly compacted environments, as it has the ability to grow in environments such as the edges or centres of dirt tracks; some communities can colonise the spaces between the bricks of paved tracks or paths (Rivas-Martinez et al., 2002). The phytocoenoses in this class are ephemeral and are made up of annual plants, and in some cases, small perennials, which are anyway always characterised by the ability to grow in edaphic contexts with relatively high nitrate contents. In the agroecosystem, the communities that are included in this syntaxon can frequently be found where the tyres of farm vehicles have compacted the

Although this is a vegetation class that has a strong human footprint, *Polygono-Poetea* does not tolerate excessive disturbance and reacts negatively to practices such as weeding or soil tillage, which, as already indicated, more favours species from the class *Stellarietea*. From an

 *Polygono arenastri-Poetalia annuae*: This order includes communities of grass, whether or not creeping, that can be found in temperate and Mediterranean climates, in sandy, silty and clayey edaphic contexts, and in some cases, rich in limestone. This order has a large ecological valence: some of the coenoses included in the order favour more wet and

evolutive point of view, *Polygono-Poetea* is positioned a step higher than *Stellarietea*.

The only order recognised for this class is *Polygono arenastri-Poetalia annuae*.

shady locations, others instead grow in more arid contexts.

vegetation and to keep the rain drains free (Biondi & Baldoni, 1991).

soil.

Fig. 2. *Biforo testiculatae-Adonidetum cupanianae*.

**2.3.2 Class** *Polygono-Poetea*

ground.

*\*Aveno barbatae-Brometum diandri*: This is an association of herbaceous margins that is relatively diffuse in the central Adriatic sector of Italy and it belongs to the alliance *Hordeion murini*. It is characterised by the species *Avena barbata* and *Bromus gussonei*. It has a spring development and it is easy to recognise in the month of April, while it tends to completely dry out with the advancing season; it is often found in situations where the soil is removed periodically to avoid invasion of the farm tracks by the

distribution that were accidentally introduced by man are often strongly represented, and these are distinguished by their high invasive capacity; in some cases, these same species have a dominant physiognomy and end up by taking over from the other species.

*Stellarietea* has a ruderal, nitrophilous or semi-nitrophilous character, and it is diffuse throughout the World, except in the tropical zones. Relative to the temperate zones and to part of the Mediterranean bioclimate distribution area, five different orders can be identified, as described below.

 *Centaureetalia cyani*: This syntaxon includes the infesting coenoses of the autumn to winter crops (cereals) without irrigation. This is well represented on marly-arenaceous or calcareous soils more or less rich in nutrients and alkaline or subalkaline, in the hilly and montane zones of the temperate bioclimate.

*\*Biforo testiculatae-Adonidetum cupanianae* (Fig. 2): This is the reference association for the commensals of the autumn to winter seeded crops of the marly-arenaceous hilly sectors of central Italy. It can be found in the Mesomediterranean and temperate hilly bioclimate belts, and it belongs to the alliance *Caucalidion lappulae*. The species belonging to this association have relatively early flowering, and the characteristic species are *Legousia hybrida*, *Adonis annua* ssp. *cupaniana*, *Papaver hybridum*, *Bifora testiculata*, *Gladiolus italicus* and *Valerianella eriocarpa*.


*\*Linario spuriae-Stachyetum annuae*: This belongs to the alliance *Polygono-Chenopodion polyspermi* and it represents the infesting vegetation of spring-summer crops in the hilly clayey and marly zones that are not irrigated. It is diffuse in many sectors of the Italian peninsula south of the River Po, and it is mainly present in situations of strong edaphic aridity, interrupted only by the contribution of the limited summer rain. The characteristic species are *Linaria spuria*, *Stachys annua* and *Picris echioides* (Baldoni, 1995).


and Biondi, 1987) and prefers soils rich in organic deposits that are frequently disturbed

or removed.

*\*Aveno barbatae-Brometum diandri*: This is an association of herbaceous margins that is relatively diffuse in the central Adriatic sector of Italy and it belongs to the alliance *Hordeion murini*. It is characterised by the species *Avena barbata* and *Bromus gussonei*. It has a spring development and it is easy to recognise in the month of April, while it tends to completely dry out with the advancing season; it is often found in situations where the soil is removed periodically to avoid invasion of the farm tracks by the vegetation and to keep the rain drains free (Biondi & Baldoni, 1991).

 *Thero-Brometalia*: This includes the nitrophilous-ruderal associations of a xerothermophilous type that are limited to Mediterranean and Submediterranean territories. These coenoses are usually found where there are high nutrient concentrations in the soil.

Fig. 2. *Biforo testiculatae-Adonidetum cupanianae*.
