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Distribution and ecology
The family is largely composed of plants that can tolerate acidic, infertile conditions. Like other stress-tolerant plants, many Ericaceae have mycorrhizal fungi to assist with extracting nutrients from infertile soils, as well as evergreen foliage to conserve absorbed nutrients. This trait is not found in the Clethraceae and Cyrillaceae, the two families most closely related to the Ericaceae. Most Ericaceae (excluding the Monotropoideae, Pyroloideae, and some Styphelioideae) form a distinctive accumulation of mycorrhizae, in which fungi grow in and around the roots and provide the plant with nutrients. The Pyroleae tribe are mixotrophic and gain sugars from the mycorrhizae, as well as nutrients.
In many parts of the world, a "heath" or "heathland" is an environment characterised by an open dwarf-shrub community found on low-quality acidic soils, generally dominated by plants in the Ericaceae. A common example is Erica tetralix. This plant family is also typical of peat bogs and blanket bogs; examples include Rhododendron groenlandicum and Kalmia polifolia. In eastern North America, members of this family often grow in association with an oak canopy, in a habitat known as an oak-heath forest.
Some evidence suggests eutrophic rainwater can convert ericoid heaths with species such as Erica tetralix to grasslands. Nitrogen is particularly suspect in this regard, and may be causing measurable changes to the distribution and abundance of some ericaceous species.
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