Cycas arnhemica
Eucalyptus woodlands and savanna grasslands·Arborescent·Stable
Cycas arnhemica is a species of cycad native to Arnhem Land in Australia's Northern Territory. It is characterized by erect stems reaching up to 2.5 meters and pinnate leaves with numerous leaflets. This species is commonly found in eucalyptus woodlands and savanna grasslands, with a restricted distribution around specific river systems.
Key Facts
- ›Native to Arnhem Land, Northern Territory, Australia.
- ›Stems are erect, growing to 1.5-2.5 meters tall.
- ›Leaves are pinnate, 70–160 cm long, with 160-260 leaflets.
- ›Found in eucalyptus woodlands and savanna grasslands.
- ›Has three recognized subspecies: C. arnhemica subsp. arnhemica, C. arnhemica subsp. muninga, and C. arnhemica subsp. natja.
- ›Seeds are 28–32 mm long and 25–29 mm broad.
Australia
Erect, 1.5-2.5 m Tall
- Numerous
- Flat
- 70–160 cm long
- Pinnate
- 160-260 leaflets
- New young leaves deep white tomentose at first
- Becoming bright to dark green
- Moderately glossy above
- Down often persisting on the underside
- Female cones: Open, 15–24 cm long, with grey sporophylls and orange hairs, two to six ovules per sporophyll, triangular lamina, toothed, with an apical spine.
- Male cones: Solitary, ovoid, 18–36 cm long and 6.5–12 cm diameter, covered in orange hairs.
28–32 mm Long, 25–29 mm Broad, Orange Sarcotesta When Ripe
Grass Fires
About Cycas arnhemica
Cycas arnhemica is a distinct species of cycad found in the Northern Territory of Australia, specifically within the Arnhem Land region, from which it derives its name. This species is characterized by its erect stems, which can reach heights of 1.5 to 2.5 meters, and its numerous, long, pinnate leaves. These leaves, measuring between 70 and 160 cm, are comprised of a substantial number of leaflets, ranging from 160 to 260. Young leaves emerge with a striking deep white tomentose covering, eventually maturing to a bright or dark green with a moderate gloss on the upper surface, often retaining some down on the underside.
Habitat and Distribution
The natural habitat of Cycas arnhemica is primarily within eucalyptus woodlands and savanna grasslands, a niche it shares with species like Cycas arenicola. Its distribution is somewhat restricted, being found predominantly around the Goyder River and the lower Blyth River in Arnhem Land. While the species is considered stable in terms of conservation status, largely due to its inhospitable habitat and healthy population numbers, it does face threats from recurring grass fires.
Botanical Features and Subspecies
Cycas arnhemica exhibits striking reproductive structures. Female cones are open, measuring 15–24 cm in length, adorned with grey sporophylls and orange hairs, and typically bear two to six ovules per sporophyll. These cones feature a triangular lamina with toothed margins and an apical spine. Male cones are solitary, ovoid, and can range from 18 to 36 cm in length and 6.5 to 12 cm in diameter, also covered in characteristic orange hairs. The seeds are a notable feature, measuring 28–32 mm long and 25–29 mm broad, developing an orange sarcotesta when ripe.
The species is further classified into three subspecies, distinguished primarily by the width of their leaflets and seed size:
- Cycas arnhemica subsp. arnhemica: Characterized by broad leaflets measuring 5-6.5 mm wide.
- Cycas arnhemica subsp. muninga: Features slender leaflets (3.5-5.5 mm wide) and seeds that are over 32 mm wide.
- Cycas arnhemica subsp. natja: Also has slender leaflets (3.5-5.5 mm wide) but with seeds under 32 mm wide.
First described in 1994, Cycas arnhemica is recognized as being closely related to Cycas maconochiei. The impact of grass fires is a significant factor for this species, as they can be detrimental to seed and seedling survival, unlike their positive effect on some other cycad species.
Source: Wikipedia ↗
Frequently Asked Questions
What is the scientific name for this cycad species?
The scientific name for this species is Cycas arnhemica. It belongs to the genus Cycas.
Where is Cycas arnhemica found naturally?
Cycas arnhemica is native to Australia, specifically in the northwest of the Northern Territory in Arnhem Land. Its distribution is somewhat restricted, found around the Goyder River and the lower Blyth River.
What are the typical habitats for Cycas arnhemica?
This cycad thrives in eucalyptus woodlands and savanna grasslands. It shares similar habitat preferences with other species like Cycas arenicola.
What are the main distinguishing features of Cycas arnhemica?
Cycas arnhemica has erect stems that can grow to 1.5-2.5 meters tall. Its leaves are long and pinnate, featuring a large number of leaflets that are initially white and tomentose, maturing to a glossy green.
Are there different subspecies of Cycas arnhemica?
Yes, there are three recognized subspecies: Cycas arnhemica subsp. arnhemica, which has broader leaflets; Cycas arnhemica subsp. muninga, with slender leaflets and larger seeds; and Cycas arnhemica subsp. natja, also with slender leaflets but smaller seeds.
How do grass fires affect Cycas arnhemica populations?
Grass fires, while beneficial to some cycad species, can cause damage to Cycas arnhemica populations. Many seeds and seedlings are killed off by these frequent events.
Related Cycad species
Cycas armstrongii
Cycas armstrongii is a species of cycad native to the Northern Territory of Australia, found across the Top End region. It is characterized by its relatively tall stems and unique deciduous leaves that shed during the dry season, earning it the nickname "fire fern." This species is notably abundant and highly tolerant of the annual grass fires common in its habitat.
Cycas bougainvilleana
Cycas bougainvilleana is a species of cycad native to the islands northeast of Papua New Guinea, including New Britain, the Bismarck Archipelago, and the Solomon Islands. It typically grows on or near the coast in calcareous coral sand dunes and adjacent forests. Botanically, it is characterized by erect stems up to 5 meters tall, crowned with numerous long, pinnate leaves, and distinct reproductive cones.
Cycas cairnsiana
Cycas cairnsiana is a species of cycad found in northern Queensland, Australia, specifically on the Newcastle Range. It is characterized by its distinctive blue-green leaves, spiny petioles, and a stem that can reach up to 5 meters in height with a swollen base. This species thrives in dry, rocky woodlands and is noted for its resilience to seasonal extremes.