Senecio keniodendron
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Senecio_keniodendron".

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Giant Groundsel

Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Asterales
Family: Asteraceae
Tribe: Senecioneae
Genus: Dendrosenecio
Species: D. keniodendron
Binomial name
Dendrosenecio keniodendron
(R.E.Fr. & T.C.E.Fr.) B.Nord.12
Image:Range of Dendrosenecio keniodendron.svg
Range of D. keniodendron in the Afrotropic
Synonyms

Senecio keniodendron R.E.Fr. & T.C.E.Fr.34

Dendrosenecio keniodendron or Giant Groundsel is a species of the genus Dendrosenecio of the large family Asteraceae and is one of the three species of giant groundsels5 endemic the high altitudes of the Afrotropic, Dendrosenecio johnstonii6 (Senecio battiscombei)7 found on Mount Kilimanjaro, Dendrosenecio keniensis occupying the lower alpine zone of Mount Kenya and in the upper area D. keniodendron. The giant plants, sometimes 6 metres (20 ft) tall, grow in even-aged and even-sized stands, dominate the communities they live in and play host to different eco-communities in their understory.8

Contents

Description

Dendrosenecio keniodendron is a giant rosette plant that can be found growing at altitudes between 3,900 metres (13,000 ft) and 4,500 metres (15,000 ft). D. keniensis grows at slightly lower altitudes, but their ranges overlap slightly and they regularly hybridise.8

Leaves and stems: D. keniodendron has woody stems up to 8 metres (26 ft) tall9 and 50 centimetres (20 in) in diameter with an 8 centimetres (3.1 in) diameter pith.3 that grow 1 centimetre (0.39 in) to 5 centimetres (2.0 in) per year10. Its 1-15 evergreen rosettes which grow from the top of the stout stems9 are composed of 50–100 leaves each 82 centimetres (32 in) long and 22 centimetres (8.7 in) wide.3 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.3 Leaf longevity is less than a year.9

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 "night bud". The older outer leaves freeze while the younger inner leaves remain above the freezing point.11

Flowers: A reproductive rosette produces a single terminal flower stalk as much as 2 metres (6.6 ft) tall.9 Flower clusters are loosely branched below and gradually simpler toward the end to 250 centimetres (98 in) tall, 120 centimetres (47 in) in diameter; with flower heads that bend downwards. Ray florets absent; 80–140 disc florets.3

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.9

Fruits: Flowers produce plumed achenes which are wind-dispersed.9 Reproduction occurs synchronously over the entire population on Mount Kenya, at intervals of 5 to 29 years,10 making D. keniodendron a mast year species.9

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 Ericas: Erica timera and Erica arborea.8

Distribution

Found in the higher altitudes of Mount Kenya.

D. keniodendron is endemic to valley floors and ridges in the alpine zone of Mount Kenya. 0 degrees latitude at altitudes of 3,700 metres (12,000 ft) and 4,500 metres (15,000 ft).9

Predators

Other giant rosette plants endemic to Mount Kenya

References

Giant Dendrosenecio flowers, Mount Kenya, Kenya.
  1. ^ International Plant Names Index. "Plant Name Details" (HTML). Retrieved on 2008-07-07.
  2. ^ Missouri Botanical Garden. "Dendrosenecio keniodendron" (HTML). Tropicos Nomenclatural Data Base. Retrieved on 2008-07-07.
  3. ^ a b c d e "Entry for Dendrosenecio keniodendron (R.E.Fr. & T.C.E.Fr.) B.Nord. [family COMPOSITAE" (HTML). Retrieved on 2008-03-27.
  4. ^ "Dendrosenecio keniodendron (R.E.Fr. & T.C.E.Fr.) B.Nord. record n° 105269" (HTML). African Flowering Plant Database (1978). Retrieved on 2008-03-27.
  5. ^ Beck, Erwin (March, 1986). "Biology of afroalpine Dendrosenecio (Asteraceae)". Plant Systematics and Evolution (Springer Wien) 152 (1-2): 123–131. doi:10.1007/BF00985353, http://www.springerlink.com/content/p41j824112323h47/. Retrieved on 27 March 2008. 
  6. ^ World Conservation Monitoring Centre; Langdon D. Clough. "Kilimanjaro National Park, Tanzania" (HTML). Encyclopedia of Earth. United Nations Environment Programme. Retrieved on 2008-03-27.
  7. ^ "Senecio johnstonii Oliv. var. johnstonii [family COMPOSITAE" (HTML). Retrieved on 2008-03-27.
  8. ^ a b c Young, Truman P.; Mary M. Peacock (March 1992). "Giant senecios and alpine vegetation of Mount Kenya". Journal of Ecology (JSTOR) 80 (1): 141–148. doi:10.2307/2261071, http://links.jstor.org/sici?sici=0022-0477(199203)80%3A1%3C141%3AGSAAVO%3E2.0.CO%3B2-P. Retrieved on 26 March 2008. 
  9. ^ a b c d e f g h Alan P. Smith and Truman P. Young (1982). "The Cost of Reproduction in Senecio keniodendron, a Giant Rosette Species of Mt. Kenya". Oecologia (Springer Science+Business Media) (55): 243–247, http://tpyoung.ucdavis.edu/publications/1982CostReprodOecol.pdf. Retrieved on 26 March 2008. 
  10. ^ a b c Stephen S. Mulkey, Alan P. Smith, Truman P. Young (1984-09). "Predation by Elephants on Senecio keniodendron in the alpine zone of Mount Kenya". Biotropica (JSTOR) 16 (3): 246–248. doi:10.2307/2388062, http://tpyoung.ucdavis.edu/publications/1984ElephantsBiotropica.pdf. Retrieved on 26 March 2008. 
  11. ^ a b Ernst-Detlef Schulze, Erwin Beck, Klaus Müller-Hohenstein (2005). "1.3 Temperature", Plant Ecology (HTML), Translated by G. Lawlor, Springer Science+Business Media, 702 pages. ISBN 354020833X. Retrieved on 2008-03-26. 


External links

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