Because the criteria are matters of degree rather than of kind, the definition of a subshrub is not sharply distinguishable from that of a shrub; examples of reasons for describing plants as subshrubs include ground-hugging stems or low growth habit. Subshrubs may be largely herbaceous, with overwintering perennial woody growth much lower-growing than deciduous summer growth. Some plants described as subshrubs are only weakly woody and some persist for only for a few years; others however, such as Oldenburgia paradoxa live indefinitely, rooted in rocky cracks.
A chamaephyte or dwarf-shrub is a plant that bears hibernating buds on persistent shoots near the ground – usually woody plants with perennating buds borne close to the ground, usually less than 25 centimetres (9.8 in) above soil surface. The significance of the closeness to the ground is that the buds remain within the soil surface layer and are thus somewhat protected from various adverse influences. Accordingly, the chamaephyte habit is especially common in stressful environments, for example:
- ecosystems on nutrient-poor soils or rock
- exposed alpine or arctic ecosystems where seasonal or perennial wind and freezing conditions are prone to kill growing shoots
- ecosystems subject to frequent burning, where many species of e.g. Banksia or Eucalyptus regrow from a lignotuber or caudex.
- heavily grazed or overgrazed ecosystems, such as tortoise turf
Examples of chamaephytes
The term chamaephyte is most formally used within the context of Raunkiær plant life-forms. Examples of chamaephytes are many of the species of the maquis and other plants of submediterranean dry ecosystems (species such as thyme, Thymus vulgaris, and rosemary, Rosmarinus officinalis); others include heather species (e.g. Calluna vulgaris and Ericas), African wild olive (Olea europaea ssp. cuspidata) and edelweiss (Leontopodium alpinum). Chamaephytes also include cushion plants.
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