Dendrosenecio keniodendron
Encyclopedia
Dendrosenecio keniodendron or Giant Groundsel is a species
of the genus
Dendrosenecio
of the large family
Asteraceae
and is one of the several species of giant groundsels endemic to the high altitudes of the Afrotropic
, including Dendrosenecio johnstonii
(Senecio battiscombei)
occurring on Mount Kilimanjaro
, Mount Kenya, and the Aberdare Mountains, Dendrosenecio keniensis
occurring the lower alpine zone of Mount Kenya and D. keniodendron occurring in higher and drier sites on Mount Kenya. The giant rosette plants, sometimes 6 metres (19.7 ft) tall, often grow in even-sized stands (presumably even-aged), with different understory communities under different-aged stands.
occurring at altitudes between 3900 metres (12,795.3 ft) and 4500 metres (14,763.8 ft). D. keniensis
grows in wetter sites, and therefore at lower altitudes on average, but their ranges abut and they occasionally hybridise.
Leaves and stems:
D. keniodendron has woody stems up to 8 metres (26.2 ft) tall
and 50 centimetres (19.7 in) in diameter with an 8 centimetres (3.1 in) diameter pith
.
that grow 1 centimetre (0.393700787401575 in) to 5 centimetres (2 in) per year.
Its 1-15 evergreen
rosettes which grow from the top of the stout stems
are composed of 50–100 leaves each 82 centimetres (32.3 in) long and 22 centimetres (8.7 in) wide.
The upper leaf-base has long, yellowish hairs, sometimes extending along upper midvein; the lower surface hairless or with sparse hairs becoming more dense along lower midvein.
Leaf longevity is less than a year.
D. keniodendron protects itself against freezing temperatures by closing its leaves when it becomes cold (at night) and opening them when it is warm (during the day); an adaptive insulation method sometimes called nyctinasty, or a night bud. The older outer leaves freeze while the younger inner meristematic buds remain above the freezing point.
Flowers:
A reproductive rosette produces a single terminal flower stalk as much as 2 metres (6.6 ft) tall.
Flower clusters are loosely branched below and gradually simpler toward the end to 250 centimetres (98.4 in) tall, 120 centimetres (47.2 in) in diameter; with flower heads that bend downwards. Ray florets absent; 80–140 disc florets.
Flowers are predominantly wind pollinated and the original rosette dies after seed maturation, and up to eight new rosettes are produced around the flower stalk base. Up to five of these new lateral rosettes survive (typically 2-3), each producing a new branch. Each flowering episode therefore results in new forks in the stem. Branching occurs only after flowering, and so provides a record of past reproduction. These branching patterns suggest that plants seldom reproduce more than 4 times before dying.
Fruits:
Flowers produce plumed achenes which are wind-dispersed.
Reproduction occurs synchronously over the entire population on Mount Kenya, at intervals of 5 to 29 years,
making D. keniodendron a mast year
species.
Communities:
In the alpine zone of Mount Kenya, Dendrosenecio keniodendron is the dominant woody species, forming evenly sized and evenly aged dense stands with nearly closed canopies. The taller stands tend to support a community of the shrubs from the Alchemilla
genus: Alchemilla argyrophylla and Alchemilla johnstonii and shorter stands supporting grasses from the genus Festuca and Carex
: Festuca pilgeri and Carex monostachya which resemble each other and have perhaps been often misidentified. Also found in these communities are the species pairs: from Poa
: Poa schimperi and Poa leptoclada, Cerastium
: Cerastium octandrum and Cerastium afromontanum, and the pair of Erica
s: Erica timera and Erica arborea.
D. keniodendron is endemic to valley slopes and ridges in the alpine zone of Mount Kenya. 0 degrees latitude at altitudes of 3700 metres (12,139.1 ft) and 4500 metres (14,763.8 ft).
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Dendrosenecio
Dendrosenecio
Dendrosenecio is a genus of flowering plants belonging to the family Asteraceae. It is a segregate of Senecio, in which it formed the subgenus Dendrosenecio...
of the large family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Asteraceae
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...
and is one of the several species of giant groundsels endemic to the high altitudes of the Afrotropic
Afrotropic
The Afrotropic is one of the Earth's eight ecozones. It includes Africa south of the Sahara Desert, the southern and eastern fringes of the Arabian Peninsula, the island of Madagascar, southern Iran and extreme southwestern Pakistan, and the islands of the western Indian Ocean. It was formerly...
, including Dendrosenecio johnstonii
(Senecio battiscombei)
occurring on Mount Kilimanjaro
Mount Kilimanjaro
Kilimanjaro, with its three volcanic cones, Kibo, Mawenzi, and Shira, is a dormant volcano in Kilimanjaro National Park, Tanzania and the highest mountain in Africa at above sea level .-Geology:...
, Mount Kenya, and the Aberdare Mountains, Dendrosenecio keniensis
Dendrosenecio keniensis
Dendrosenecio keniensis Dendrosenecio keniensis Dendrosenecio keniensis (syn. Senecio keniensis and S. brassica is one of the giant groundsels endemic the higher altitudes of Mount Kenya. It is in the family Asteraceae and the genus Dendrosenecio (previously a Senecio). Dendrosenecio keniodendron...
occurring the lower alpine zone of Mount Kenya and D. keniodendron occurring in higher and drier sites on Mount Kenya. The giant rosette plants, sometimes 6 metres (19.7 ft) tall, often grow in even-sized stands (presumably even-aged), with different understory communities under different-aged stands.
Description
Dendrosenecio keniodendron is a giant rosette plantRosette (botany)
In botany, a rosette is a circular arrangement of leaves, with all the leaves at a single height.Though rosettes usually sit near the soil, their structure is an example of a modified stem.-Function:...
occurring at altitudes between 3900 metres (12,795.3 ft) and 4500 metres (14,763.8 ft). D. keniensis
Dendrosenecio keniensis
Dendrosenecio keniensis Dendrosenecio keniensis Dendrosenecio keniensis (syn. Senecio keniensis and S. brassica is one of the giant groundsels endemic the higher altitudes of Mount Kenya. It is in the family Asteraceae and the genus Dendrosenecio (previously a Senecio). Dendrosenecio keniodendron...
grows in wetter sites, and therefore at lower altitudes on average, but their ranges abut and they occasionally hybridise.
Leaves and stems:
D. keniodendron has woody stems up to 8 metres (26.2 ft) tall
and 50 centimetres (19.7 in) in diameter with an 8 centimetres (3.1 in) diameter pith
Pith
Pith, or medulla, is a tissue in the stems of vascular plants. Pith is composed of soft, spongy parenchyma cells, which store and transport nutrients throughout the plant. In eudicots, pith is located in the center of the stem. In monocots, it extends also into flowering stems and roots...
.
that grow 1 centimetre (0.393700787401575 in) to 5 centimetres (2 in) per year.
Its 1-15 evergreen
Evergreen
In botany, an evergreen plant is a plant that has leaves in all seasons. This contrasts with deciduous plants, which completely lose their foliage during the winter or dry season.There are many different kinds of evergreen plants, both trees and shrubs...
rosettes which grow from the top of the stout stems
are composed of 50–100 leaves each 82 centimetres (32.3 in) long and 22 centimetres (8.7 in) wide.
The upper leaf-base has long, yellowish hairs, sometimes extending along upper midvein; the lower surface hairless or with sparse hairs becoming more dense along lower midvein.
Leaf longevity is less than a year.
D. keniodendron protects itself against freezing temperatures by closing its leaves when it becomes cold (at night) and opening them when it is warm (during the day); an adaptive insulation method sometimes called nyctinasty, or a night bud. The older outer leaves freeze while the younger inner meristematic buds remain above the freezing point.
Flowers:
A reproductive rosette produces a single terminal flower stalk as much as 2 metres (6.6 ft) tall.
Flower clusters are loosely branched below and gradually simpler toward the end to 250 centimetres (98.4 in) tall, 120 centimetres (47.2 in) in diameter; with flower heads that bend downwards. Ray florets absent; 80–140 disc florets.
Flowers are predominantly wind pollinated and the original rosette dies after seed maturation, and up to eight new rosettes are produced around the flower stalk base. Up to five of these new lateral rosettes survive (typically 2-3), each producing a new branch. Each flowering episode therefore results in new forks in the stem. Branching occurs only after flowering, and so provides a record of past reproduction. These branching patterns suggest that plants seldom reproduce more than 4 times before dying.
Fruits:
Flowers produce plumed achenes which are wind-dispersed.
Reproduction occurs synchronously over the entire population on Mount Kenya, at intervals of 5 to 29 years,
making D. keniodendron a mast year
Mast year
A mast year is a year in which vegetation produces a significant abundance of mast . The term originally applied solely to trees, like oak trees, that produce fruit useful for feeding farm animals...
species.
Communities:
In the alpine zone of Mount Kenya, Dendrosenecio keniodendron is the dominant woody species, forming evenly sized and evenly aged dense stands with nearly closed canopies. The taller stands tend to support a community of the shrubs from the Alchemilla
Alchemilla
Alchemilla is a genus of herbaceous perennial plants in the Rosaceae, and a popular garden herb with the common name Lady's mantle. There are about 300 species, the majority native to cool temperate and subarctic regions of Europe and Asia, with a few species native to the mountains of Africa,...
genus: Alchemilla argyrophylla and Alchemilla johnstonii and shorter stands supporting grasses from the genus Festuca and Carex
Carex
Carex is a genus of plants in the family Cyperaceae, commonly known as sedges. Other members of the Cyperaceae family are also called sedges, however those of genus Carex may be called "true" sedges, and it is the most species-rich genus in the family. The study of Carex is known as...
: Festuca pilgeri and Carex monostachya which resemble each other and have perhaps been often misidentified. Also found in these communities are the species pairs: from Poa
Poa
Poa is a genus of about 500 species of grasses, native to the temperate regions of both hemispheres. Common names include meadow-grass , bluegrass , tussock , and speargrass. "Poa" is Greek for fodder...
: Poa schimperi and Poa leptoclada, Cerastium
Cerastium
Cerastium is a genus of annual, winter annual, or perennial plants belonging to the family Caryophyllaceae. The around 100 species are commonly called Mouse-ear chickweed; different species are found nearly worldwide but the greatest concentration is mainly from the northern temperate areas of the...
: Cerastium octandrum and Cerastium afromontanum, and the pair of Erica
Erica
Erica ,the heaths or heathers, is a genus of approximately 860 species of flowering plants in the family Ericaceae. The English common names "heath" and "heather" are shared by some closely related genera of similar appearance....
s: Erica timera and Erica arborea.
Distribution
Predators
- Cape HyraxCape HyraxThe Rock Hyrax , or Cape Hyrax, is one of the four living species of the order Hyracoidea, and the only living species in the genus Procavia. Like all hyraxes, it is a medium-sized terrestrial mammal, superficially resembling a guinea pig with short ears and tail...
or Rock Hyrax (Procavia capensis) or (Procavia johnstoni mackinderi) - African Bush ElephantAfrican Bush ElephantThe African Bush Elephant or African Savanna Elephant is the larger of the two species of African elephant. Both it and the African Forest Elephant have usually been classified as a single species, known simply as the African Elephant...
(Loxodonta africana)
Other giant rosette plants endemic to Mount Kenya
- Lobelia keniensis or Lobelia deckeniiLobelia deckeniiLobelia deckenii is a species of giant lobelia of the mountains of East Africa. It grows in moist areas, such as valley bottoms and moorland, in contrast to Lobelia telekii which grows in a similar, but drier habitat. These two species produce occasional hybrids...
- Dendrosenecio keniensisDendrosenecio keniensisDendrosenecio keniensis Dendrosenecio keniensis Dendrosenecio keniensis (syn. Senecio keniensis and S. brassica is one of the giant groundsels endemic the higher altitudes of Mount Kenya. It is in the family Asteraceae and the genus Dendrosenecio (previously a Senecio). Dendrosenecio keniodendron...
- Lobelia telekiiLobelia telekiiLobelia telekii is a species of flowering plant in the bellflower family, Campanulaceae, that is found only in the alpine zones of Mount Kenya, Mount Elgon, and the Aberdare Mountains of East Africa. It lives at high altitudes on well-drained sloped hillsides...
- Carduus keniensis