An informative guide to the vegetation of an area is the life-form spectrum. The plants are divided into the following life-forms:
- phanerophytes = trees and shrubs
- chamaephytes = dwarf shrubs (under half a meter high)
- hemicryptophytes = herbaceous perennial plants that survive the unfavorable period of the year only in their underground parts with the renewal buds lying directly at the surface
- cryptophytes = plants surviving as roots, tubers or bulbs with the renewal buds lying underground
- hydrophytes = aquatic plants
- therophytes = annual plants
In the life-form spectrum of Naxos the therophytes (annual plants) have by far the largest share, namely 50%. The number of species of therophytes can be especially high in sparse vegetation.
meadow with numerous species of therophytes (annuals)
The second largest share is held by the hemicryptophytes (Herbacious perennials) with 23%, followed by the cryptophytes (plants with tubers or bulbs) with 13%. Although these species are perennial, only their roots, tubers or bulbs survive the unfavorable summer season and they sprout again after the first rains in autumn.
Many large grass species are hemicryptophytes.
Typical cryptophytes (bulbous plants) are the crocuses.
8% of the plants are chamaephytes (dwarf shrubs, 74 species) and only 5% phanerophytes (large shrubs and trees, 45 species). These larger species that survive the summer drought not only as seeds or in their underground parts, but as the whole plant, are clearly in the minority. Nevertheless dwarf shrubs and low perennial plants are characteristic of the mediterranean vegetation whereas they play only a very small role in the vegetation of Central Europe. Only 1% of the species of Naxos are hydrophytes (aquatic plants).
typical dwarf shrub vegetation on Mount Zeus
In this forest occur at least 10 species of phanerophytes (trees and large shrubs).
Hydrophytes (aquatic plants) are rather rare on Naxos, here a species of Ranunculus.
Life-form spectra similar to Naxos are found in the deserts or semi desert areas of North Africa. The high proportion of therophytes is caused not only by drought and grazing pressure, but also by millennia of farming which have favored short-lived weeds.
Four strategies
According to the different life-forms, we can characterise four different strategies with which plants have adapted to the specific conditions of the Mediterranean region such as summer drought, grazing, and fire.
The annual plants (therophytes) solve the problem of drought by flourishing only during the favorable season; they die with the beginning of the summer. Annual plants put their energy into the rapid production of many seeds. They often protect themselves only imperfectly from grazing (many species grow in rosettes, some have thorns); usually they strive to survive simply by their high number and rapid growth.
In winter the abandoned fields are covered with many therophytes.
The Hop Treefoil (Trifolium arvense) is a typical therophyte which is equipped for the rapid production of seeds even under unfavorable conditions.
The same is true of the daisies, which often form dense stands.
The crypto- and hemicryptophytes survive the summer only in their underground parts. This allows them a quick start in autumn; many species flower immediately after the first rainfalls while the leaves appear later. As perennial plants they have to protect themselves better against grazing than the annuals: many species have stiff inedible leaves or are poisonous. They produce tubers or bulbs for the storage of nutrients during the unfavorable season.
The asphodel (Asphodelus ramosus) is a typical cryptophyte with inedible leaves and fleshy roots forming tubers.
The sea onion (Urginea maritima) is the first plant to flower in late summer. Being poisonous it occurs in heavily grazed areas often in large numbers.
The dwarf shrubs (chamaephytes) and shrubs have perennial overground parts, but remain low. With many species the leaves are shed or wither in summer; other species produce only minute leaves. The dwarf shrubs do not form a very deep root system, but try to absorb rain water immediately by a dense superficial network of roots. They are exposed to grazing, so that most species are thorny, and many are toxic, highly aromatic, hairy or otherwise deterrent. Most dwarf shrubs reproduce by seeds, some also vegetatively. Compared to the trees, dwarf shrubs have only a limited ability to compete. In the shade of trees they grow poorly. In areas with good enough soil that are undisturbed by grazing and fire, dwarf shrubs are slowly replaced by trees. Therefore, some shrub species such as Cistus are highly flammable and germinate very quickly after fire, so that they can occupy large areas in the first years after a fire until they are gradually replaced again by other shrubs or trees.
phrygana in spring
flowering Cistus (Cistus monspeliensis)
The same place in late summer: the dwarf shrubs have dropped their leaves.
The trees (large phanerophytes with a stem) put their energy into forming a high stem by which they can escape grazing. Their leaves are usually edible, only a few species have prickly leaves. Most species of the Mediterranean region are evergreen, but in the more humid regions deciduous species also occur. Trees can only grow in locations where the underground allows deep rooting so that they reach sufficient water supplies during the summer. The fact that there are no trees that shed their leaves in summer, like so many mediterranean dwarf shrub species, is probably due to their considerably longer generation cycle, so that the time that elapsed since the origin of the Mediterranean climate about 7000 years ago was too short for a proper adaptation. The mediterranean trees can generally survive fire well by virtue of their deep roots and they usually have a high ability for sprouting and vegetative reproduction. Reproduction by seed plays a much smaller role.
Along the rivers grow riparian forests with deciduous species such as Plane trees (Platanus orientalis) and Alder (Alnus glutinosa).
In drier locations, especially on marble, grow sclerophyllous trees such as Kermes Oak, Wild Olive and Phillyrea; in some places these species form small woods.
see also: The vegetation of Naxos
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