Pacific Island Ecosystems at Risk (PIER)


Khaya senegalensis


RISK ASSESSMENT RESULTS: Low risk, score: 0


Australian/New Zealand Weed Risk Assessment adapted for Hawai‘i.

Research directed by C. Daehler (UH Botany) with funding from the Kaulunani Urban Forestry Program and US Forest Service

Information on Risk Assessments
Original risk assessment

Khaya senegalensis; dry zone mahogany

Answer

1.01

Is the species highly domesticated?

y=-3, n=0

n

1.02

Has the species become naturalized where grown?

y=-1, n=-1

n

1.03

Does the species have weedy races?

y=-1, n=-1

n

2.01

Species suited to tropical or subtropical climate(s) (0-low; 1-intermediate; 2-high) – If island is primarily wet habitat, then substitute “wet tropical” for “tropical or subtropical”

See Append 2

2

2.02

Quality of climate match data (0-low; 1-intermediate; 2-high) see appendix 2

2

2.03

Broad climate suitability (environmental versatility)

y=1, n=0

n

2.04

Native or naturalized in regions with tropical or subtropical climates

y=1, n=0

y

2.05

Does the species have a history of repeated introductions outside its natural range? y=-2

?=-1, n=0

y

3.01

Naturalized beyond native range y = 1*multiplier (see Append 2), n= question 2.05

n

3.02

Garden/amenity/disturbance weed y = 1*multiplier (see Append 2)

n=0

n

3.03

Agricultural/forestry/horticultural weed y = 2*multiplier (see Append 2)

n=0

n

3.04

Environmental weed y = 2*multiplier (see Append 2)

n=0

n

3.05

Congeneric weed y = 1*multiplier (see Append 2)

n=0

n

4.01

Produces spines, thorns or burrs

y=1, n=0

n

4.02

Allelopathic

y=1, n=0

n

4.03

Parasitic

y=1, n=0

n

4.04

Unpalatable to grazing animals

y=1, n=-1

4.05

Toxic to animals

y=1, n=0

n

4.06

Host for recognized pests and pathogens

y=1, n=0

y

4.07

Causes allergies or is otherwise toxic to humans

y=1, n=0

n

4.08

Creates a fire hazard in natural ecosystems

y=1, n=0

n

4.09

Is a shade tolerant plant at some stage of its life cycle

y=1, n=0

4.1

Tolerates a wide range of soil conditions (or limestone conditions if not a volcanic island)

y=1, n=0

n

4.11

Climbing or smothering growth habit

y=1, n=0

n

4.12

Forms dense thickets

y=1, n=0

n

5.01

Aquatic

y=5, n=0

n

5.02

Grass

y=1, n=0

n

5.03

Nitrogen fixing woody plant

y=1, n=0

n

5.04

Geophyte (herbaceous with underground storage organs -- bulbs, corms, or tubers)

y=1, n=0

n

6.01

Evidence of substantial reproductive failure in native habitat

y=1, n=0

n

6.02

Produces viable seed.

y=1, n=-1

y

6.03

Hybridizes naturally

y=1, n=-1

6.04

Self-compatible or apomictic

y=1, n=-1

6.05

Requires specialist pollinators

y=-1, n=0

n

6.06

Reproduction by vegetative fragmentation

y=1, n=-1

y

6.07

Minimum generative time (years) 1 year = 1, 2 or 3 years = 0, 4+ years = -1

See left

20

7.01

Propagules likely to be dispersed unintentionally (plants growing in heavily trafficked areas)

y=1, n=-1

n

7.02

Propagules dispersed intentionally by people

y=1, n=-1

y

7.03

Propagules likely to disperse as a produce contaminant

y=1, n=-1

n

7.04

Propagules adapted to wind dispersal

y=1, n=-1

y

7.05

Propagules water dispersed

y=1, n=-1

7.06

Propagules bird dispersed

y=1, n=-1

n

7.07

Propagules dispersed by other animals (externally)

y=1, n=-1

n

7.08

Propagules survive passage through the gut

y=1, n=-1

8.01

Prolific seed production (>1000/m2)

y=1, n=-1

y

8.02

Evidence that a persistent propagule bank is formed (>1 yr)

y=1, n=-1

n

8.03

Well controlled by herbicides

y=-1, n=1

8.04

Tolerates, or benefits from, mutilation, cultivation, or fire

y=1, n=-1

y

8.05

Effective natural enemies present locally (e.g. introduced biocontrol agents)

y=-1, n=1

Total score:

0

Supporting data:

Source

Notes

1.01

no evidence

1.02

no evidence

1.03

no evidence

2.01

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

Review of natural distribution
K. senegalensis occurs naturally in Africa between 15 and 8N in a strip extending from the Atlantic to the Indian Ocean across Mali and Senegal, northern Cameroon and northern Uganda, as well as the southern part of Sudan.
The natural phytogeographical distribution corresponds to the 'Sudanian Regional Centre of Endemism' and the 'Guineo-Congolia/Sudania Regional Transition Zone' (White, 1983). The species is often found individually dispersed in natural vegetation and secondary forest, in association with Detarium senegalense, Parinari excelsa and Erythrophleum suaveolens.
Natural latitude range
Approximate limits north to south: 15N to 8N

2.02

2.03

(1)CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International. (2)www.forests.qld.gov.au/qts/treetext.html (3)http://www.raingardens.com/bbs/index.cgi?read=2652 (4)http://www.pfnq.com.au/Species%20Map.htm#Khaya (5)Irvine, F.R. 1961. Woody plants of Ghana. Oxford University Press :London.

Climate
The main geographical distribution corresponds to the climatic zone of the Sudan, which is characterized by an annual precipitation of 650-1300 mm in summer, a dry season lasting for 4-8 months and an annual mean temperature of about 24C. In the Fouta Djalon region of Guinea, K. senegalensis tolerates minimum temperatures of at least 5C and the maximum annual rainfall can be of up to 1750 mm in certain sites in Guinea. This distribution corresponds to the north half of the 'Tropical savanna climate zone (Aw)' of Koeppen/Geiger and to the 'Wet and dry tropical climates (V3)' of Troll/Pfaffen. In moister regions, K. senegalensis is replaced by K. grandifoliola, K. anthotheca and K. ivorensis.
A modified description of climatic requirements (see climatic data table of this data sheet) was prepared by CSIRO (see Booth and Jovanovic, 2000).
Descriptors
- Altitude range: 0 - 1800 m
- Mean annual rainfall: 700 - 1750 mm
- Rainfall regime: summer; winter
- Dry season duration: 2 - 8 months
- Mean

2.04

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

Review of natural distribution
K. senegalensis occurs naturally in Africa between 15 and 8N in a strip extending from the Atlantic to the Indian Ocean across Mali and Senegal, northern Cameroon and northern Uganda, as well as the southern part of Sudan.
The natural phytogeographical distribution corresponds to the 'Sudanian Regional Centre of Endemism' and the 'Guineo-Congolia/Sudania Regional Transition Zone' (White, 1983). The species is often found individually dispersed in natural vegetation and secondary forest, in association with Detarium senegalense, Parinari excelsa and Erythrophleum suaveolens.
Natural latitude range
Approximate limits north to south: 15N to 8N

2.05

(1)CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International. (2)http://www.raingardens.com/bbs/index.cgi?read=2652

(1)Location of introductions
Plantations have been established within its area of natural distribution and are well established in Vietnam, India (for example, Maharashtra, Tamil Nadu), Java, Cuba and Guadeloupe. More recent plantings have occurred in Australia (Brennan and Radomiljac, 1988), Brazil, Puerto Rico, Guyana, Thailand (Limpiyaprapant et al., 1996), Cape Verde (Spaak, 1990), Reunion (Tassin et al., 1998) and South Africa. (2)Exotic: Australia, Cuba, India, Indonesia, Puerto Rico, Singapore, South Africa, Vietnam

3.01

no evidence

3.02

no evidence

3.03

no evidence

3.04

no evidence

3.05

A Global Compendium of Weeds. Website available at: <http://www.hear.org/gcw/index.html>

Status(es) of K. nyasica : Naturalised~Cultivation Escape [not listed as a weed]

4.01

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

no description of these traits

4.02

no evidence

4.03

no evidence

4.04

(1)http://www.raingardens.com/bbs/index.cgi?read=2652 (2)http://www.pfnq.com.au/Species%20Map.htm#Khaya (3)Omokanye, A. T.; Balogun, R. O.; Onifade, O. S.; Afolayan, R. A.; Olayemi, M. E. 2001. Assessment of preference and intake of browse species by Yankasa sheep at Shika, Nigeria. Small Ruminant Research, 42: 203-210 (4)Petit, S.2000. Woody fodder and livestock trails of Peul herdsmen in western Burkina Faso.: Bois et Forêts des Tropiques No.265, pp.77-80 (5)Irvine, F.R. 1961. Woody plants of Ghana. Oxford University Press :London.

(1)Fodder: Young leaves contain fairly large amounts of digestible crude protein. The leaves are used as a fodder for cattle and camels, although they are not very palatable. (2)Foliage is suitable as fodder for grazing stock. (3)Khaya senegalensis and Gliricidia sepuim were completely rejected by sheep. (4)The main fodder species used are .... Khaya senegalensis (5)Leaves are used as fodder for cattle and camels though not very palatable

4.05

http://www.raingardens.com/bbs/index.cgi?read=2652

Fodder: Young leaves contain fairly large amounts of digestible crude protein. The leaves are used as a fodder for cattle and camels, although they are not very palatable.

4.06

(1) CAB International, (2000) Forestry Compendium Global Module. Wallingford,
(2) Tilakaratna, D. (2001) Hypsipyla shoot borers of Meliaceae in Sri Lanka. Floyd, R. B.; Hauxwell, C. , editors. Forestry Research Centre, Kumbalpola, Boyagane, Sri Lanka., pp.3-6, 13 ref. (3)http://www.pfnq.com.au/Species%20Map.htm#Khaya

(1) "The most important problem that has a significant influence on the silviculture of Khaya spp., as well as other Meliaceae, is borer attack, principally by Hypsipyla robusta. "
(2) AB: "Out of five introduced species of subfamily Swietenioideae, two are very important (Swietenia macrophylla and Khaya senegalensis ). H. robusta is a serious problem in plantings on open sites as practised by the private sector and research to find a control technique is important. " (3)Khaya senegalensis has been observed in many areas of Northern Australia to be significantly less prone to attack from the Tip-moth borer (Hypsipyla robusta) than other species in its family (Meliaceae).

4.07

no evidence

4.08

a single-trunked, large tree

4.09

(1)CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International. (2)http://www.raingardens.com/bbs/index.cgi?read=2652

(1)"K. senegalensis is generally a light-demanding species (although it will tolerate up to 50% shade when immature)" (2)Moderately shade tolerant; Seedlings can survive light to moderate shade.

4.1

(1)CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International. (2)http://www.raingardens.com/bbs/index.cgi?read=2652

(1)Soil and physiography
K. senegalensis prefers moist sites, such as depressions and the banks of rivers and streams (gallery forest). Favourable hydrological conditions seem to be more important for growth than for nutrient availability. Moist alluvial formations are favoured over lateritic soils (ferrosols) in open savanna. Areas with termite nests appear to be favourable for the development of K. senegalensis (Evy Thies, address available on request, personal communication, 1999).
Descriptors
- Soil texture: medium; heavy
- Soil drainage: free
- Soil reaction: acid; neutral
- Special soil tolerances: shallow; infertile
- Soil types: acid soils; cambisols; ferralsols; fluvisols; lateritic soils; vertisols (2)Tolerant to a wide range of soil conditions, from neutral to very strongly acidic and from very well-drained, coarse sandy loam to somewhat poorly drained clay. Prefers neutral, deep, sandy loam soil that is well drained. Such fertile conditions are often found in alluvial soils.

4.11

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

"A deciduous tree, reaching 15-20 m in savanna, on fertile and deep soils up to 35 m high and up to 1.5 m in diameter, with a clean bole 8-16 m long"

4.12

http://www.pfnq.com.au/Species%20Map.htm#Khaya

Natural regeneration from seed is poor,

5.01

terrestrial

5.02

tree; Meliaceae

5.03

no evidence

5.04

tree

6.01

no evidence

6.02

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

"Mature seed is classified as intermediate in germination"

6.03

no evidence

6.04

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

"K. senegalensis is monoecious"

6.05

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

"insect pollinated."

6.06

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

"Regeneration is favoured in clearings, the species develops stool sprouts and root suckers. "

6.07

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

Trees begin to produce seed after 20-25 years.

7.01

no evidence

7.02

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

Location of introductions
Plantations have been established within its area of natural distribution and are well established in Vietnam, India (for example, Maharashtra, Tamil Nadu), Java, Cuba and Guadeloupe. More recent plantings have occurred in Australia (Brennan and Radomiljac, 1988), Brazil, Puerto Rico, Guyana, Thailand (Limpiyaprapant et al., 1996), Cape Verde (Spaak, 1990), Reunion (Tassin et al., 1998) and South Africa.

7.03

no evidence

7.04

(1)http://www.raingardens.com/bbs/index.cgi?read=2652 (2)CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

(1)"Seeds are brown, broadly transversely ellipsoid to flat, paper thin (about 25 x 18 mm) with narrowly-winged margins."Seed may be dispersed up to 100 m by prevailing winds.; (2)"Dissemination of K. senegalensis is anemochorous and natural regeneration is abundant. "

7.05

http://www.raingardens.com/bbs/index.cgi?read=2652

occurs in riverine forests and is scattered within the higher-rainfall savannah woodlands. In moister areas, K. senegalensis is found on uplands, but it is restricted to riparian habitats or stream bottoms that extend into the savannah in the drier portions of the range. [possibly water dispersed]

7.06

no evidence

7.07

no evidence of ingestion

7.08

no evidence

8.01

(1)CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International. (2)http://www.raingardens.com/bbs/index.cgi?read=2652

Seed is collected from mature fruits (4500-7000 seeds per kg).; The fruit is an upright, almost spherical, woody capsule, 4-10 cm in diameter, opening by four valves from the apex. Seeds are brown, broadly transversely ellipsoid to flat, paper thin (about 25 x 18 mm) with narrowly-winged margins. (2)Seeds brown, 6 or more per cell [24 per fruit, probably reaches 1000 = 42 fruit per m2 in adult trees]

8.02

(1)CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International. (2)http://www.raingardens.com/bbs/index.cgi?read=2652

(1)" Mature seed is classified as intermediate in germination behaviour and the longevity of the seed is 6-8 months at ambient temperature." (2)Germination is epigeal, about 90% of fresh seed germinate within 18 days.

8.03

no evidence

8.04

(1)CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International. (2)http://www.raingardens.com/bbs/index.cgi?read=2652

(1)"Regeneration is favoured in clearings, the species develops stool sprouts and root suckers."; "Saplings are browsed by wildlife and are very sensitive to fire, whereas adult trees are relatively resistant." (2)Khaya senegalensis coppices well.

8.05

no evidence


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