Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Fraxinus uhdei
(tropical ash)

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Datasheet

Fraxinus uhdei (tropical ash)

Summary

  • Last modified
  • 27 September 2018
  • Datasheet Type(s)
  • Invasive Species
  • Host Plant
  • Preferred Scientific Name
  • Fraxinus uhdei
  • Preferred Common Name
  • tropical ash
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Dicotyledonae
  • Summary of Invasiveness
  • Fraxinus uhdei is a fast-growing, medium to large tree (up to 35-40 m tall and 1 m stem diameter) that grows naturally in mixed mountain forests from west-central Mexico to Costa Rica. It has been introduced to...

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Pictures

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PictureTitleCaptionCopyright
F. uhdei growing on the slopes of Mauna Loa island of Hawaii.
TitleTree
CaptionF. uhdei growing on the slopes of Mauna Loa island of Hawaii.
CopyrightA. Ares
F. uhdei growing on the slopes of Mauna Loa island of Hawaii.
TreeF. uhdei growing on the slopes of Mauna Loa island of Hawaii.A. Ares
TitleLeaves and samaras of Fraxinus uhdei
Caption
CopyrightA. Ares
Leaves and samaras of Fraxinus uhdeiA. Ares

Identity

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Preferred Scientific Name

  • Fraxinus uhdei (Wenz.) Lingelsh.

Preferred Common Name

  • tropical ash

Other Scientific Names

  • Fraxinus americana f. ovalifolia Wenz.
  • Fraxinus americana var. uhdei Wenz.
  • Fraxinus cavekiana Standl. & Steyerm.
  • Fraxinus chiapensis Lundell
  • Fraxinus hondurensis Standl.
  • Fraxinus ovalifolia (Wenz.) Lingelsh.
  • Fraxinus uhdei var. pseudoperiptera Lingelsh.

International Common Names

  • English: Hawaiian ash; Mexican ash; Shamel ash
  • Spanish: fresno; fresno blanco

Local Common Names

  • Colombia: urapan

EPPO code

  • FRXUH (Fraxinus uhdei)

Summary of Invasiveness

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Fraxinus uhdei is a fast-growing, medium to large tree (up to 35-40 m tall and 1 m stem diameter) that grows naturally in mixed mountain forests from west-central Mexico to Costa Rica. It has been introduced to Hawaii, Puerto Rico and sub-Himalayan regions of India for watershed protection and timber production. It is also a popular street and shade tree in California, Arizona and Mexico. F. uhdei is shade tolerant and a prolific seed producer, and has become highly invasive in Hawaii where it has spread from cultivation into disturbed forest areas. It has been recorded as naturaized on the islands of Hawaii, Maui, Molokai and Oahu, where it has been included among the alien species most disruptive to native ecosystems. Invasions are more intense on fertile soils and along streams. In some stands of F. uhdei, understorey vegetation is almost completely absent, but stands with sparse canopies can harbour a profuse understorey of native and introduced species. Chemical control with a range of herbicides has proved to be very effective in Hawaii. Monitoring where introduced and replacement with native trees where naturalization is observed would reduce future risks.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Dicotyledonae
  •                     Order: Oleales
  •                         Family: Oleaceae
  •                             Genus: Fraxinus
  •                                 Species: Fraxinus uhdei

Notes on Taxonomy and Nomenclature

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Fraxinus is a large genus in the family Oleaceae, with 43 species native to temperate and subtropical regions of the northern hemisphere. Phylogenetic relationships among 40 of the 43 recognized species were estimated on the basis of nuclear ribosomal ITS sequences (Wallander, 2008). This research suggested that the previous subgenera and subsections be abandoned, and a new section established. A sectional key is presented in which the genus Fraxinus is divided into six sections: Dipetalae, Melioides, Pauciflorae, Sciadanthus, Fraxinus and Ornus. F. uhdei is placed in section Melioides (Endl.) Lingelsh.

Although two varieties of F. uhdei have been described, var. pseudoperiptera and var. typica, the Plant List (2013) recognizes no infraspecific taxa. The synonym F. americana var. uhdei Wenz. highlights the close relationship of F. uhdei and F. americana.

Fraxinus species are all commonly known as ash trees in English, with variants based on the species. The generic name is the Latin for ash tree, while the specific epithet uhdei honours Carl Uhde, a German plant collector who explored eastern Mexico in 1844-48 (Bracewell, 2005).

Description

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Based on the description given by Wagner et al. (1999) as reported by PIER (2016), F. uhdei is a forest tree up to 35-40 m tall and up to 1 m in trunk diameter, with furrowed grey or brown bark, producing a canopy 9-13 m wide. Young branches are pubescent, soon glabrate. Leaves are 15-28(-30) cm long, compound and oppositely pinnate with 5-9 leaflets, (5-)7-11 cm long, 2-5 cm wide, upper surface dull green, glabrous, lower surface pale green, puberulent along midrib, margins irregularly serrulate, apex long-acuminate, base cuneate, petioles 6-10 cm long, petiolules 3-13 mm long. Flowers are unisexual (and the plants dioecious), in panicles 13-20 cm long; buds paired, covered with brown, finely pubescent scales; calyx minute, 4-toothed. Samaras are oblong-elliptic to oblong-oblanceolate, 2-4 cm long, the wing 5-6 mm wide, apex with a small notch. F. uhdei is sometimes referred to as an evergreen species but it is winter-deciduous in some regions.

Plant Type

Top of page Broadleaved
Perennial
Seed propagated
Tree
Vegetatively propagated
Woody

Distribution

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The native range of F. uhdei is commonly cited as mainland Central America, from Costa Rica, through Honduras and Guatemala to Mexico, and it is reported in many Mexican states north to Sinaloa, San Luis Potosi and Durango (USDA-ARS, 2016). McClintock (2001) also notes it in the Mexican states of Oaxaca and Chiapas; in Chiapas it has been observed in pine-oak-liquidambar forest, where it generally occurs along drier streams with other deciduous and semideciduous tree species.

USDA-ARS (2016) reports F. uhdei as native to Bolivia, but this is questionable. Records in the Missouri Botanical Garden (2015) confirm its presence in La Paz and Cochabamba; however, all these records are recent (2014-15) with a single other record from 2009. Thus, also noting the disjunct nature of these occurrences from the Central American native range, and that this species is widely planted as a street tree especially at higher altitudes, it is probable that the Bolivian records represent introductions. In her detailed work on the genus Fraxinus, Wallander (2008) also noted the presence of F. uhdei only in Central America (and Hawaii). F. uhdei (called ‘urapan’) is also recorded in Colombia (Bogota, Medellin, Pereira and Manizales) and Ecuador (Quito), where Fraxinus spp. are noted as widely planted in urban and rural settings in the Andes (Filguera et al., 2004). Thus, South American records are taken here as being introduced, and it is possible that it may be more widespread than reported. However, that the species is also possibly native to the Andean region cannot be discounted, and this assumption requires verification.

In the USA, F. uhdei is introduced, naturalized and invasive in Hawaii (PIER, 2016) and, more recently, in California (Hrusa et al., 2002; Calflora, 2016; USDA-NRCS, 2016). It is present but less common as a street tree in Arizona (Bricker and Stutz, 2005). F. uhdei is grown as an ornamental in Taiwan (Shen and Chen, 1993). As well as Hawaii, it has been introduced as a potential forestry species to Puerto Rico (Liogier and Martorell, 1982) and also India, where Shukla and Sangal (1980) reported on trial plantations established at Dehra Dun in the northern state of Uttarakhand (formerly Uttaranchal) in 1960. The India Biodiversity Portal (2016) has a single report (from 2015) of the species in a tropical moist deciduous forest near Dahanu in northwestern Maharashtra.

As an ornamental street tree, it is also possible that it is has been more widely introduced than is reported. 

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasivePlantedReferenceNotes

Asia

IndiaPresentPresent based on regional distribution.
-MaharashtraPresentIntroduced Not invasive India Biodiversity Portal, 2016
-Uttar PradeshPresent Planted
-UttarakhandPresent only in captivity/cultivationIntroduced Not invasive Shukla and Sangal, 1980Introduced into forestry trials in New Forest, Dehra Dun
TaiwanPresent only in captivity/cultivationIntroduced Planted Shen and Chen, 1993Cultivated as a street tree

North America

MexicoPresentNative Not invasive Natural USDA-ARS, 2016
USAPresentPresent based on regional distribution.
-ArizonaPresent only in captivity/cultivationIntroduced Not invasive Planted Bricker and Stutz, 2005Cultivated as a street tree
-CaliforniaPresentIntroduced Invasive Hrusa et al., 2002; Calflora, 2016; USDA-NRCS, 2016
-HawaiiPresentIntroduced Invasive Wagner et al., 1999; Haysom and Murphy, 2003; USDA-NRCS, 2016

Central America and Caribbean

Costa RicaPresentNative Planted USDA-ARS, 2016
GuatemalaPresentNative Natural USDA-ARS, 2016
HondurasPresentNativeUSDA-ARS, 2016
Puerto RicoPresentIntroducedLiogier and Martorell, 1982; USDA-ARS, 2016

South America

BoliviaPresentIntroducedMissouri Botanical Garden, 2015; USDA-ARS, 2016Uncertainty whether native or introduced
ColombiaPresentIntroducedFilgueira et al., 2004Uncertainty whether native or introduced
EcuadorPresentIntroducedFilgueira et al., 2004Uncertainty whether native or introduced
-Galapagos IslandsPresentIntroduced Not invasive Charles Darwin Foundation, 2008

History of Introduction and Spread

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According to Little and Skolmen (1989), F. uhdei was introduced to Hawaii from Mexico for use as a shade tree in the late 1800s, when two trees were planted on Oahu, one in Kalihi Valley and the other in Nuuanu Valley. These two trees are believed to be the seed sources for all the tropical ash planted in Hawaii. The Division of Forestry began planting this species for watershed cover about 1920 and subsequently planted over 700,000 trees on all the major islands. For a time in the early 1960s the species was extensively planted as a potential timber crop but was later found to have such poor form that it was dropped from consideration. The poor form may have resulted from inbreeding depression, since the entire population appears to have originated from the two parent trees.

However, weak wood strength was also noted in the species when it was introduced into the New Forest at Dehra Dun, northern India, in plantation trials established in 1960 (Shukla and Sangal, 1980).

F. uhdei, apart from tropical ash, is also commonly known as Shamel ash, named after Dr. Archie Shamel who first planted the trees in California in the 1920s, in Fairmont Park, Riverside, being a member of the Parks Commission there (McClintock, 2001).

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
California Mexico 1920s Ornamental purposes (pathway cause) Yes No McClintock (2001)
Hawaii Mexico late 1800s Ornamental purposes (pathway cause) Yes No Little and Skolmen (1989)
India 1960 Forestry (pathway cause) Yes No Shukla and Sangal (1980)

Risk of Introduction

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F. uhdei is reported in a Pacific island risk assessment to be invasive or potentially invasive, with a high risk of invasion score of 11 (PIER, 2016). Acknowledging its use and value as an ornamental and street tree, as well as a forestry species, it is highly likely to be introduced further.

Habitat

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In Hawaii, where F. uhdei is most invasive, it is observed commonly in forests and forest edges, rapidly colonizing disturbed forest areas (Weber, 2003). Invasions are also more intense on fertile soils and along streams (Harrington and Ewell, 1997). In Hawaii, it is an invasive at high altitude zones (PIER, 2016), but in California and elsewhere it also naturalizes at lower elevations.

It thrives in moist soil conditions, is typically confined to water courses and moist areas, but can survive arid conditions. In California where it is used as a street tree it appears to be spreading into canyons below mesas, and is also seen to be invading oak woodland as well as riparian and wetland areas (Council for Watershed Health, 2016).

Habitat List

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CategorySub-CategoryHabitatPresenceStatus
Terrestrial
Terrestrial – ManagedManaged forests, plantations and orchards Principal habitat Productive/non-natural
Disturbed areas Principal habitat Harmful (pest or invasive)
Disturbed areas Principal habitat Natural
Urban / peri-urban areas Secondary/tolerated habitat Productive/non-natural
Terrestrial ‑ Natural / Semi-naturalNatural forests Principal habitat Harmful (pest or invasive)
Natural forests Principal habitat Natural
Riverbanks Principal habitat Harmful (pest or invasive)
Riverbanks Principal habitat Natural
Wetlands Secondary/tolerated habitat Harmful (pest or invasive)
Wetlands Secondary/tolerated habitat Natural

Growth Stages

Top of page Seedling stage, Vegetative growing stage

Biology and Ecology

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Reproductive Biology

Section Melioides contains 15 American Fraxinus species, all dioecious trees with unisexual apetalous and wind-pollinated flowers (Wallander, 2001), though flowers of F. uhdei are known to be visited by bees, such as in Colombia (Obregon and Nates-Parra, 2014). F. uhdei regenerates rapidly from seed and trees coppice vigorously when cut and have also been reported to sucker.

Physiology and Phenology

F. uhdei trees are fast growing, reaching 7.5-10.5 m in 10 years. They are fire and shade tolerant; Pimienta-Barrios et al. (2012) report on the ecophysiological responses of F. uhdei to drought and recovery after rainfall. The species has also shown growth and physiological changes along an elevational gradient in Hawaii (Ares and Fownes, 2000).

When Gleason and Ares (2004) examined the physiological and morphological characteristics of Acacia koa (koa) and F. uhdei to understand the possible mechanisms facilitating invasion of koa forests in Hawaii uplands by F. uhdei, they found that F. uhdei was better able to survive defoliation than koa especially under high-light conditions, and seedlings allocated more carbon and nitrogen to storage, favouring their survival in high light under intense herbivory and on sites with seasonal or highly variable N availability. Ares and Fownes (2001) also reported on the competitive interactions between these two species.

F. uhdei is a deep-rooting species; roots in one study were seen to penetrate deeper than those of Quercus crassipes and Q. crassifolia. In fine-textured soil, F. uhdei root and shoot dry weight was significantly greater than in either Quercus species, but this was not the case in coarse-textured soil (Chacalo et al., 2000).

Regarding the chemical composition of plant parts, 18 compounds were isolated from the fruits, leaves and bark of F. uhdei, including secoiridoids, phenylpropanoids, lignans, phenylethanoids and triterpenoids, plus mannitol and β-sitosterol (Pérez-Castorena et al., 1997).

Longevity

Seeds of F. uhdei may remain viable in the soil for at least eight years (Council for Watershed Health, 2016).

Associations

In Mexico, F. uhdei is associated with the following forest plant communities: Quercus forest, pine forest, montane mesophyllic forest and gallery forest (Zepeda Dominguez, 2006). McClintock (2001) noted it in pine (Pinus) - oak (Quercus) - liquidambar (Liquidambar) forest in Chiapas. In the floodplain between Puebla and San Martín Texmelucan in the state of Puebla at an altitude of 2200 m, F. uhdei was found growing along watercourses in association with Alnus glabrata [Alnus acuminata subsp. glabrata], Salix bonplandiana, Buddleja cordata, Schinus molle and Populus species (Rzedowski, 2006).

In western North America F. uhdei is a food plant for larvae of several swallowtail butterflies, including Papilio eurymedon, P. multicaudata and P. rutulus (Calflora, 2016).

Environmental Requirements

F. uhdei is generally a species of subtropical upland areas up to 2750 m above sea level in Mexico, and also occasionally up to higher elevations in the Andes, to 3600 m in Bolivia (Missouri Botanical Garden, 2015), but it is also known to grow, but only rarely, in coastal areas. The species prefers higher rainfall zones, though tolerates dry seasons up to six months. Although it prefers light and fertile soils, according to Calflora (2016) it tolerates fine, medium or coarse soils and very slightly saline conditions. It prefers a soil pH of 5.7 to 7.6 and a temperature range of 4ºC in winter to 32ºC in summer. 

Climate

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ClimateStatusDescriptionRemark
Af - Tropical rainforest climate Tolerated > 60mm precipitation per month
Am - Tropical monsoon climate Tolerated Tropical monsoon climate ( < 60mm precipitation driest month but > (100 - [total annual precipitation(mm}/25]))
Aw - Tropical wet and dry savanna climate Preferred < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25])
BS - Steppe climate Tolerated > 430mm and < 860mm annual precipitation
Cs - Warm temperate climate with dry summer Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
10-35 300 3600

Air Temperature

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Parameter Lower limit Upper limit
Absolute minimum temperature (ºC) -2
Mean annual temperature (ºC) 12 25
Mean maximum temperature of hottest month (ºC) 20 32
Mean minimum temperature of coldest month (ºC) 4 20

Rainfall

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ParameterLower limitUpper limitDescription
Dry season duration46number of consecutive months with <40 mm rainfall
Mean annual rainfall8004000mm; lower/upper limits

Rainfall Regime

Top of page Uniform
Winter

Soil Tolerances

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Soil drainage

  • free

Soil reaction

  • acid
  • neutral

Soil texture

  • light
  • medium

Special soil tolerances

  • saline

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Aceria fraxiniflora Herbivore Inflorescence to genus
Alternaria alternata Pathogen Leaves not specific
Candidatus Phytoplasma asteris Pathogen Whole plant not specific
Fusarium sporotrichioides Pathogen Leaves not specific
Homalodisca vitripennis Herbivore Stems not specific
Phytoplasma fraxini Pathogen Whole plant not specific

Notes on Natural Enemies

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F. uhdei is attacked by two phytoplasmas, Phytoplasma asteris and Phytoplasma fraxini, causing ash yellows. Perilla-Henao et al. (2012) noted P. asteris for the first time on F. uhdei in Colombia, and Filgueira et al. (2004) provided the first confirmed record of ash yellows occurring outside North America, on F. uhdei in Colombia and Ecuador, with significance for Fraxinus species which are widely planted in urban and rural settings throughout the Andean range, as well as natural stands in Mexico. Testing in Arizona, USA, for the presence of ash decline showed symptoms of this phytoplasma disease (progressive tree dieback) on F. velutina but not on F. uhdei (Bricker and Stutz, 2005).

Foliar necrosis, related to the prevalence of Alternaria alternata, was observed in F. uhdei in Azcapotzalco, Mexico, and a potential association between the ash flower eriophyid (Aceria fraxiniflora) and the micromycete Fusarium sporotrichioides was also noted (Reséndiz Martínez et al., 2015).

F. uhdei is also a host to the glassy-winged sharpshooter (Homalodisca vitripennis) which is a vector for Pierce’s disease of grapevines caused by Xylella fastidiosa (Calflora, 2016).

Means of Movement and Dispersal

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Natural Dispersal

F. uhdei samaras are dispersed by wind and water run-off, and possibly via storm drain systems (Council for Watershed Health, 2016). Trees can coppice vigorously from root and shoot sprouts (PIER, 2016).

Intentional Introduction

Tropical ash is widely grown as an ornamental and street tree in its native range, and is one of the most common trees in Mexico City, for example. Because of its value as an ornamental, it has been introduced to other countries such as the USA (Bricker and Stutz, 2005) and Taiwan (Shen and Chen, 1993). In Hawaii, it was introduced as a shade tree and then was widely planted as a forestry tree (Little and Skolmen, 1989; PIER, 2016), these plantations becoming the source of invasions into the wild.

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Disturbance Yes
Escape from confinement or garden escape Yes
Forestry Yes Yes
Landscape improvement Yes Yes
Nursery trade Yes
Ornamental purposes Yes Yes

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Water Yes
Wind Yes

Impact Summary

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CategoryImpact
Cultural/amenity Positive
Economic/livelihood Positive and negative
Environment (generally) Positive and negative
Human health Negative

Economic Impact

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As a secondary host for H. vitripennis, a vector of Pierce’s disease (Calflora, 2016), the infestation and presence of F. uhdei near vineyards, particularly in California, could lead to disease outbreaks and consequent crop and economic losses. 

Environmental Impact

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Impact on Habitats

Smith (1985) considers F. uhdei to be one of the 86 alien plant species most disruptive to native ecosystems in Hawaii because it can form single species stands. It can spread into disturbed forest areas and exhibits rapid growth, creating shade and outcompeting native plants. It germinates easily and prolifically, and is shade tolerant so can survive within existing native forest canopy (Council for Watershed Health, 2016).

In Hawaii, invasions have been recorded on the islands of Hawaii, Maui, Molokai and Oahu, where F. uhdei has been included among the species most disruptive to native forest ecosystems. F. uhdei is seen as a threat in particular in Kamakou Preserve, a rainforest in the mountains of East Molokai, and also in Waikamoi Preserve on the slopes of Mt. Haleakala in East Maui (Tunison, 1991). Invasions are more intense on fertile soils and along streams (Harrington and Ewell, 1997). In some stands, understorey vegetation is almost completely absent but stands with sparse canopies can harbour a profuse understorey of native and introduced species.

F. uhdei affects decomposition dynamics and nutrient turnover in montane Hawaiian rainforests (Rothstein et al., 2004). Compared to native species, it produces greater quantities of litter which is thinner, and has higher N and P concentrations and lower concentrations of lignin and soluble polyphenols. Microbes decomposing the litter produce fewer enzymes involved in N and P acquisition and more of those involved in cellulose degradation. Differences in litter quality and microbial activity result in a strong effect of litter type on rates of mass loss, and F. uhdei litter decomposes and releases nutrients at nearly twice the rate of Metrosideros litter regardless of site of decomposition. It is suggested that the large amounts of N and P in F. uhdei litter raise nutrient availability to decomposers in the forest floor, and the greater immobilization of N and P under an F. uhdei canopy may act as a governor on rates of nutrient cycling, limiting the degree to which F. uhdei invasion accelerates N and P cycling in this system (Rothstein et al., 2004).

Kagawa et al. (2009) found that forest water use was influenced by species composition, stem density, tree size, sapwood allocation and understorey contributions. In Hawaii, at the stand level, F. uhdei had nine times great water use than native M. polymorpha trees.

Impact on Biodiversity

Where invasive in Hawaii, several native species may be threatened in ecozones where F. uhdei has become naturalized. These include plant species in the genera Bidens, Calamagrostis, Cyanea, Cyrtandra, Geranium, Mucuna and Wikstroemia, as well as the tree snail Newcombia cumingi (US fish and Wildlife Service, 2012).

Native sandalwood trees on Hawaii are also threatened by competition from F. uhdei. Santalum haleakalae var. haleakalae is rare and restricted to Haleakala volcano on East Maui. S. haleakalae var. lanaiense, federally listed as endangered, occurs on the islands of Maui, Molokai and Lanai. Despite this wide distribution, seedlings are rarely, if ever, observed. It spreads locally via vegetative means by root sprouts when surface roots are damaged or exposed. Threats to both sandalwoods include competition for space, light, water and nutrients with alien plant species, including F. uhdei (Harbaugh et al., 2010).

Silene lanceolata is a short-lived perennial, federally listed as endangered, which is present on Hawaii, Oahu and Molokai. On Molokai it grows in Metrosideros polymorphaDodonaea viscosaLeptecophylla tameiameiae shrubland on gulch slopes, ridge tops and cliffs in dry to mesic shrubland between 581 and 1043 m elevation. Habitat destruction by feral ungulates, fire and competition from invasive introduced plants such as F. uhdei, Lantana camara and Ricinus communis are immediate threats to S. lanceolata on that island (US Fish and Wildlife Service, 2010).

Threatened Species

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Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Santalum haleakalaeUSA ESA listing as endangered species USA ESA listing as endangered speciesHawaiiCompetition - monopolizing resourcesHarbaugh et al., 2010
Silene lanceolata (Kauai catchfly)USA ESA listing as endangered species USA ESA listing as endangered speciesHawaiiCompetition - monopolizing resourcesUS Fish and Wildlife Service, 2010

Social Impact

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Pollen from members of the Oleaceae, including Fraxinus, is a widespread cause of pollinosis. In tests carried out in Mexico City, F. uhdei was found to provide almost 30% of the total pollen load and was an important source of Oleaceae-associated aeroallergens in that city (Robledo-Retana et al., 2015).

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
  • Pioneering in disturbed areas
  • Tolerant of shade
  • Benefits from human association (i.e. it is a human commensal)
  • Long lived
  • Fast growing
  • Has high reproductive potential
  • Has propagules that can remain viable for more than one year
  • Reproduces asexually
Impact outcomes
  • Ecosystem change/ habitat alteration
  • Modification of successional patterns
  • Monoculture formation
  • Negatively impacts forestry
  • Negatively impacts human health
  • Reduced native biodiversity
  • Threat to/ loss of endangered species
  • Threat to/ loss of native species
Impact mechanisms
  • Causes allergic responses
  • Competition - monopolizing resources
  • Competition - shading
  • Rapid growth
Likelihood of entry/control
  • Highly likely to be transported internationally deliberately

Uses

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Economic Value

As a timber tree, F. uhdei provides a valuable, medium density (0.5 g/cm3), pale brown wood with a straight grain and moderately fine texture (Shukla and Sangal, 1980). The wood is used mainly for cabinetwork, furniture, moulding and panelling, but it is also suitable for boat building, craftwood, flooring, interior trim, joinery poles, particleboards, pulpwood, plywood, structural sawnwood and veneer. It is easy to season, machine and finish but is susceptible to blue stain, Lyctus borers and termites. The sapwood is permeable to preservatives and the heartwood is moderately resistant.

In its native range, F. uhdei has been selectively logged but it is not a prime timber species. In Chiapas, Mexico, it has been grown in hedgerows for wood and fuel. In plantations, F. uhdei has high survival and rapid initial growth on favourable sites, but often exhibits uneven growth rates across sites, poor form and has a tendency to lodge. F. uhdei is relatively shade tolerant and can regenerate by coppicing (Walters and Wick, 1973). In Hawaii, F. uhdei has higher growth rates in relatively deep soils derived from volcanic ash than in shallow, stony organic soils. Timber yields in Hawaii and Puerto Rico have ranged between 4.1 and 11.5 m3/ha/year. 

Social Benefit

F. uhdei is planted as an ornamental street or shade tree in its native range and has been introduced as such in California, Hawaii and elsewhere. It is considered to have attractive leaves.

Uhdenoside, a secoiridoid dilactone isolated from leaves of F. uhdei, has potential applications in natural medicine (Shen et al., 1995).

Environmental Services

In the 1920s, F. uhdei was planted extensively in Hawaii for watershed protection (Harrington and Ewell, 1997).

Uses List

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Environmental

  • Amenity
  • Landscape improvement
  • Windbreak

Fuels

  • Fuelwood

Materials

  • Wood/timber

Medicinal, pharmaceutical

  • Source of medicine/pharmaceutical

Ornamental

  • garden plant

Wood Products

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Boats

Furniture

Pulp

  • Short-fibre pulp

Roundwood

  • Pit props
  • Posts
  • Stakes

Sawn or hewn building timbers

  • Carpentry/joinery (exterior/interior)
  • Flooring
  • For light construction
  • Wall panelling

Veneers

Wood-based materials

  • Fibreboard
  • Hardboard
  • Medium density fibreboard
  • Particleboard
  • Plywood

Woodware

  • Cutlery
  • Industrial and domestic woodware
  • Sports equipment
  • Tool handles
  • Toys
  • Turnery
  • Wood carvings

Similarities to Other Species/Conditions

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F. uhdei was originally described as a variety of F. americana, apparently based on similarities in samara morphology. The abaxial leaf surfaces of F. uhdei, however, lack the papillose cuticular structure characteristic of F. americana and its presumed closest relatives in eastern North America (Nesom, 2010). A channeled leaf axis and a smaller (2.5-4 cm long) samara also distinguish F. uhdei from F. americana.

Prevention and Control

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Prevention

The Council for Watershed Health (2016) suggests alternative species to F. uhdei for planting as street trees in areas where it has become invasive in California, including several native species.

Cultural Control and Sanitary Measures

When Friday et al. (2008) assessed whether disturbance from logging facilitated the spread of F. uhdei and other alien species beyond existing plantations on windward Mauna Kea on the island of Hawaii, they found that F. uhdei was able to regenerate following logging more rapidly than native tree species. Although basal area growth of F. uhdei was large enough to offset a decline in native trees and cause an increase in forest productivity, it was recommended that when F. uhdei plantations are harvested, forest managers should plan ways of favouring regeneration of the native Acacia koa, a species more valuable both for timber and for conservation.

Physical/Mechanical Control

Fraxinus trees coppice readily and can propagate vegetatively, so any mechanical control must also remove the roots. Manual or mechanical pulling of seedlings and small saplings is recommended by Tunison (1991).

Chemical Control

Tunison (1991) reports on research in Hawaii which found that undiluted triclopyr amine salt in a continuous ring notch application offered complete control of F. uhdei. Application of triclopyr to cut stumps was more practical for smaller trees. Lower concentrations than that recommended for notching were also effective. Control should begin with outlying plants and the edges of larger stands, progressing inwards toward the centre of the stand.

In other chemical control trials conducted in Hawaii, F. uhdei was controlled completely by cut-surface (continuous ring) applications of 2,4-D, dicamba, glyphosate or picloram. If applied in two notches in the trunk, all these herbicides except picloram also caused severe injury, but trees took 18 months to die. Better control was achieved if herbicide was applied in four drilled holes per tree and continuous ring notching, when using dicamba, glyphosate, metsulfuron or triclopyr. Good control was also reported with triclopyr ester in diesel oil applied to basal bark, and with undiluted triclopyr amine applied to frills, though only saplings were susceptible to triclopyr ester applied to basal bark (Motooka et al., 2002, 2003).

References

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Contributors

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20/01/2016 Invasive Species Compendium sections added by:

Nick Pasiecznik, Consultant, France

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