Plant community (or "phytocoenosis", spelled also "phytocenosis", both rarely used) is a collection of plant species within a designated geographical unit, which forms a relatively uniform patch, distinguishable from neighbouring patches of different vegetation types. The components of each plant community are influenced by soil type, topography, climate and human disturbance. In many cases there are several soil types within a given phytocoenosis[1].
A forest community includes the overstory, or upper tree layer of the canopy, as well as the understory, further subdivided into the shrub layer, herb layer, and sometimes also moss layer. In some cases of complex forests there is also a well-defined lower tree layer.
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An example is a grassland on the northern Caucasus Steppes, where common grass species found are Festuca sulcata and Poa bulbosa. A common sedge in this grassland phytocoenosis is Carex shreberi. Other representative forbs occurring in these steppe grasslands are Artemisia austriaca and Polygonum aviculare.[2]
An example of a three tiered plant community is in Central Westland of South Island, New Zealand. These forests are the most extensive continuous reaches of podocarp/broadleaf forests in that country. The overstory includes miro, rimu and mountain totara. The mid-story includes tree ferns such as Cyathea smithii and Dicksonia squarrosa, whilst the lowest tier and epiphytic associates include Asplenium polyodon, Tmesipteris tannensis, Astelia solandri and Blechnum discolor.[3]