Source: California Invasive Plant Council


URL of this page: http://www.cal-ipc.org/site/paf/342
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Cal-IPC Plant Assessment Form

For use with "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands"
by the California Invasive Plant Council and the Southwest Vegetation Management Association

Table 1. Species and Evaluator Information

Species name
(Latin binomial):
The official Latin binomial name for this species. Specify only one name here. Additional species names may go into the Synonyms field.

Eucalyptus globulus

Synonyms:
Additional Latin binomial names for this species. Separate multiple names with a ; character. Please avoid narrative descriptions, and list only the binomial names.
Eucalyptus maidenii subsp. globulus (Labill.) J.B.Kirkp.
Common names:
Common names for this species. Separate multiple names with a ; character.
blue gum; Tasmanian blue gum; blue gum eucalyptus; common eucalyptus; Southern blue gum; Victorian blue gum
Evaluation date:
The date(s) when this species PAF was filled out, modified, or reviewed. This is free-form text, so it may include multiple dates or other notes.
03/19/04
Evaluator #1 Peter J. Warner
California Dept. of Parks and Recreation; Cal-IPC
P. O. Box 603, Little River, CA 95456
(707) 937-2278; (707) 937-9172
corylus@earthlink.net; pwarner@mcn.org; pwarn@parks.ca.gov
List committee members: Carla Bossard, Joe DiTomaso, John Randall, Cynthia Roye, Jake Sigg, Alison Stanton, Peter Warner
Committee review date: 03/19/04
List date:
Re-evaluation date(s): 3/25/2014
General comments
on this assessment:
Enter any additional notes about this assessment, such as factors affecting the reliability or completeness of the answers, likely affects of impacts, or research which is not specific to California but is still relevant in the evaluation of this species.

Re-evaluated 03/25/2014
Kristina Wolf
University of California, Davis
Plant & Environmental Sciences
PES 1210 Mail Stop 1
1 Shields Avenue
Davis, California 95616
(530) 750-9771
kmwolf@ucdavis.edu

Table 2. Criteria, Section, and Overall Scores

Overall Score

Plant scoring matrix
Based on letter scores from Sections 1 through 3 below

ImpactInvasivenessDistribution
AA BAnyHighNo Alert
AC DAnyModerateAlert
BA BA BModerateNo Alert
BA BC DModerateAlert
BC DAnyLimitedNo Alert
CAA BModerateNo Alert
CAC DLimitedNo Alert
CBAModerateNo Alert
CBB DLimitedNo Alert
CCAnyLimitedNo Alert
DAnyAnyNot ListedNo Alert

Moderate

Alert Status

Plant scoring matrix
Based on letter scores from Sections 1 through 3 below

ImpactInvasivenessDistribution
AA BAnyHighNo Alert
AC DAnyModerateAlert
BA BA BModerateNo Alert
BA BC DModerateAlert
BC DAnyLimitedNo Alert
CAA BModerateNo Alert
CAC DLimitedNo Alert
CBAModerateNo Alert
CBB DLimitedNo Alert
CCAnyLimitedNo Alert
DAnyAnyNot ListedNo Alert

No Alert

Documentation

The total documentation score is the average
of Documentation scores given in Table 2.

Reviewed Scientific Publication4 points
Other Published Material3 points
Observational2 points
Anecdotal1 points
Unknown or No Information0 points

3.4 out of 5

Score Documentation
1.1 Impact on abiotic ecosystem processes
Consider the impact on the natural range and variation of abiotic ecosystem processes and system-wide parameters in ways that significantly diminish the ability of native species to survive and reproduce. Alterations that determine the types of communities that can exist in a given area are of greatest concern. Examples of abiotic processes include:
- fire occurrence, frequency, and intensity;
- geomorphological changes such as erosion and sedimentation rates;
- hydrological regimes, including soil water table;
- nutrient and mineral dynamics, including salinity, alkalinity, and pH;
- light availability (e.g. when an aquatic invader covers an entire water body that would otherwise be open).

Select the one letter below that best describes this species’ most severe impact on an abiotic ecosystem process:
A. Severe, possibly irreversible, alteration or disruption of an ecosystem process.
B. Moderate alteration of an ecosystem process.
C. Minor alteration of an ecosystem process.
D. Negligible perceived impact on an ecosystem process.
U. Unknown.
A. Severe Reviewed Scientific Publication
Impact
Section 1 Scoring Matrix
Q 1.1Q 1.2Q 1.3Q 1.4Score
AAAnyAnyA
ABA,BAnyA
ABC,D,UAnyB
AC,D,UAnyAnyB
BAAAnyA
BABAA
BAB,CB-D,UB
BAC,D,UAA
BAC,D,UB-D,UB
BBAAA
BC,D,UAAB
BB-DAB-D,UB
BB-DB-D,UAnyB
BD,UC,D,UA-BB
BD,UC,D,UC,D,UC
C-D,UAAAnyA
CBAAnyB
CA,BB-D,UAnyB
CC,D,UAnyAnyC
DA,BBAnyB
DA,BC,D,UAnyC
DCAnyAnyC
DD,UAnyAnyD
UAB,CAnyB
UB,CA,BAnyB
UB,CC,D,UAnyC
UUAnyAnyU


Four-part score
ABBD

Total Score
A
1.2 Impact on plant community
Consider the cumulative ecological impact of this species to the plant communities it invades. Give more weight to changes in plant composition, structure, and interactions that involve rare or keystone species or rare community types. Examples of severe impacts include:
- formation of stands dominated (>75% cover) by the species;
- occlusion (>75% cover) of a native canopy, including a water surface, that eliminates or degrades layers below;
- significant reduction or extirpation of populations of one or more native species.

Examples of impacts usually less than severe include:
- reduction in propagule dispersal, seedling recruitment, or survivorship of native species;
- creation of a new structural layer, including substantial thatch or litter, without elimination or replacement of a pre-existing layer;
- change in density or depth of a structural layer;
- change in horizontal distribution patterns or fragmentation of a native community;
- creation of a vector or intermediate host of pests or pathogens that infect native plant species.

Select the one letter below that best describes this species’ impact on community composition, structure and interactions:
A. Severe alteration of plant community composition, structure, or interactions.
B. Moderate alteration of plant community composition.
C. Minor alteration of community composition.
D. Negligible impact known; causes no perceivable change in community composition, structure, or interactions.
U. Unknown.
B. Moderate Reviewed Scientific Publication
1.3 Impact on higher trophic levels
Consider the cumulative impact of this species on the animals, fungi, microbes, and other organisms in the communities that it invades. Although a non-native species may provide resources for one or a few native species (e.g. by providing food, nesting sites, etc.), the ranking should be based on the species’ net impact on all native species. Give more weight to changes in composition and interactions involving rare or keystone species or rare community types.
Examples of severe impacts include:
- extirpation or endangerment of an existing native species or population;
- elimination or significant reduction in native species’ nesting or foraging sites, cover, or other critical resources (i.e., native species habitat), including migratory corridors.

Examples of impacts that are usually less than severe include:
- minor reduction in nesting or foraging sites, cover, etc. for native animals;
- minor reduction in habitat connectivity or migratory corridors;
- interference with native pollinators;
- injurious components, such as awns or spines that damage the mouth and gut of native wildlife species, or production of anti-digestive or acutely toxic chemical that can poison native wildlife species.

Select the one letter below that best describes this species’ impact on community composition and interactions:
A. Severe alteration of higher trophic populations, communities, or interactions.
B. Moderate alteration of higher trophic level populations, communities, or interactions.
C. Minor alteration of higher trophic level populations, communities or interactions.
D. Negligible impact; causes no perceivable change in higher trophic level populations, communities, or interactions.
E. Unknown.
B. Moderate Reviewed Scientific Publication
1.4 Impact on genetic integrity
Consider whether the species can hybridize with and influence the proportion of individuals with non-native genes within populations of native species. Mechanisms and possible outcomes include:
- production of fertile or sterile hybrids that can outcompete the native species;
- production of sterile hybrids that lower the reproductive output of the native species.

Select the one letter below that best describes this species’ impact on genetic integrity:
A. Severe (high proportion of individuals).
B. Moderate (medium proportion of individuals).
C. Minor (low proportion of individuals).
D. No known hybridization.
U. Unknown.
D. None Other Published Material
2.1 Role of anthropogenic and natural disturbance in establishment
Assess this species’ dependence on disturbance—both human and natural—for establishment in wildlands. Examples of anthropogenic disturbances include:
- grazing, browsing, and rooting by domestic livestock and feral animals;
- altered fire regimes, including fire suppression;
- cultivation;
- silvicultural practices;
- altered hydrology due to dams, diversions, irrigation, etc.;
- roads and trails;
- construction;
- nutrient loading from fertilizers, runoff, etc.

Examples of natural disturbance include:
- wildfire;
- floods;
- landslides;
- windthrow;
- native animal activities such as burrowing, grazing, or browsing.

Select the first letter in the sequence below that describes the ability of this species to invade wildlands:
A. Severe invasive potential—this species can establish independent of any known natural or anthropogenic disturbance.
B. Moderate invasive potential—this species may occasionally establish in undisturbed areas but can readily establish in areas with natural disturbances.
C. Low invasive potential—this species requires anthropogenic disturbance to establish.
D. No perceptible invasive potential—this species does not establish in wildlands (though it may persist from former cultivation).
U. Unknown.
C. Low Other Published Material
Invasiveness
Section 2 Scoring Matrix
Total pointsScore
17-21A
11-16B
5-10C
0-4D
More than two U’sU


Total Points
7

Total Score
C
2.2 Local rate of spread with no management
Assess this species’ rate of spread in existing localized infestations where the proportion of available habitat invaded is still small when no management measures are implemented.

Select the one letter below that best describes the rate of spread:
A. Increases rapidly (doubling in <10 years)
B. Increases, but less rapidly
C. Stable
D. Declining
U. Unknown
C. Stable Reviewed Scientific Publication
2.3 Recent trend in total area infested within state
Assess the overall trend in the total area infested by this species statewide. Include current management efforts in this assessment and note them.

Select the one letter below that best describes the current trend:
A. Increasing rapidly (doubling in total range statewide in <10 years)
B. Increasing, but less rapidly
C. Stable
D. Declining
U. Unknown
C. Stable Reviewed Scientific Publication
2.4 Innate reproductive potential
(see Worksheet A)
Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.
C. Low Other Published Material
2.5 Potential for human-caused dispersal
Assess whether this species is currently spread—or has high potential to be spread—by direct or indirect human activity. Such activity may enable the species to overcome natural barriers to dispersal that would not be crossed otherwise, or it may simply increase the natural dispersal of the species. Possible mechanisms for dispersal include:
- commercial sales for use in agriculture, ornamental horticulture, or aquariums;
- use as forage, erosion control, or revegetation;
- presence as a contaminant (seeds or propagules) in bulk seed, hay, feed, soil, packing materials, etc.;
- spread along transportation corridors such as highways, railroads, trails, or canals;
- transport on boats or boat trailers.

Select the one letter below that best describes human-caused dispersal and spread:
A. High—there are numerous opportunities for dispersal to new areas.
B. Moderate—human dispersal occurs, but not at a high level.
C. Low—human dispersal is infrequent or inefficient.
D. Does not occur.
U. Unknown.
C. Low Other Published Material
2.6 Potential for natural long-distance dispersal
We have chosen 1 km as the threshold of "long-distance." Assess whether this species is frequently spread, or has high potential to be spread, by animals or abiotic mechanisms that can move seed, roots, stems, or other propagules this far. The following are examples of such natural long-distance dispersal mechanisms:
- the species’ fruit or seed is commonly consumed by birds or other animals that travel long distances;
- the species’ fruits or seeds are sticky or burred and cling to feathers or hair of animals;
- the species has buoyant fruits, seeds, or other propagules that are dispersed by flowing water;
- the species has light propagules that promote long-distance wind dispersal;
- The species, or parts of it, can detach and disperse seeds as they are blown long distances (e.g., tumbleweed).

Select the one letter below that best describes natural long-distance dispersal and spread:
A. Frequent long-distance dispersal by animals or abiotic mechanisms.
B. Occasional long-distance dispersal by animals or abiotic mechanisms.
C. Rare dispersal more than 1 km by animals or abiotic mechanisms.
D. No dispersal of more than 1 km by animals or abiotic mechanisms.
U. Unknown.
C. Rare Reviewed Scientific Publication
2.7 Other regions invaded
Assess whether this species has invaded ecological types in other states or countries outside its native range that are analogous to ecological types not yet invaded in your state (see Worksheets B, C, and D for California, Arizona, and Nevada, respectively, in Part IV for lists of ecological types). This information is useful in predicting the likelihood of further spread within your state.

Select the one letter below that best describes the species' invasiveness in other states or countries, outside its native range.
A. This species has invaded 3 or more ecological types elsewhere that exist in your state and are as yet not invaded by this species (e.g. it has invaded Mediterranean grasslands, savanna, and maquis in southern Europe, which are analogous to California grasslands, savanna, and chaparral, respectively).
B. Invades 1 or 2 ecological types that exist but are not yet invaded in your state.
C. Invades elsewhere but only in ecological types that it has already invaded in the state.
D. Not known as an escape anywhere else.
U. Unknown.
C. Already invaded Other Published Material
3.1 Ecological amplitude/Range
(see Worksheet C)
Refer to Worksheet C and select the one letter below that indicates the number of different ecological types that this species invades.
A. Widespread—the species invades at least three major types or at least six minor types.
B. Moderate—the species invades two major types or five minor types.
C. Limited—the species invades only one major type and two to four minor types.
D. Narrow—the species invades only one minor type.
U. Unknown.
A. Widespread Other Published Material
Distribution
Section 3 Scoring Matrix
Q 3.1Q 3.2Score
AA, BA
AC,D,UB
BAA
BB,CB
BDC
CA,BB
CC,DC
DAB
DB,CC
DDD
A,BUC
C,DUD
UUU


Total Score
B
3.2 Distribution/Peak frequency
(see Worksheet C)
To assess distribution, record the letter that corresponds to the highest percent infested score entered in Worksheet C for any ecological type.
C. Low Observational

Table 3. Documentation

Scores are explained in the "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands".
Short citations may be used in this table. List full citations at end of this table.

Section 1: Impact

Reviewed Scientific Publication A Question 1.1 Impact on abiotic ecosystem processes
Consider the impact on the natural range and variation of abiotic ecosystem processes and system-wide parameters in ways that significantly diminish the ability of native species to survive and reproduce. Alterations that determine the types of communities that can exist in a given area are of greatest concern. Examples of abiotic processes include:
- fire occurrence, frequency, and intensity;
- geomorphological changes such as erosion and sedimentation rates;
- hydrological regimes, including soil water table;
- nutrient and mineral dynamics, including salinity, alkalinity, and pH;
- light availability (e.g. when an aquatic invader covers an entire water body that would otherwise be open).

Select the one letter below that best describes this species’ most severe impact on an abiotic ecosystem process:
A. Severe, possibly irreversible, alteration or disruption of an ecosystem process.
B. Moderate alteration of an ecosystem process.
C. Minor alteration of an ecosystem process.
D. Negligible perceived impact on an ecosystem process.
U. Unknown.
Identify ecosystem processes impacted:

Eucalyptus globulus was most frequently planted in grasslands, although some exist mixed within native tree stands (Griffiths & Villablanca 2013); the intensity, and frequency of natural grassland fire regimes is very different when compared with eucalyptus stands (Bossard et al. 2000, FEMA 2013, LSA Associates 2009). While eucalyptus may have been planted within or escaped into native forests, this is less common. Fire regimes within native tree stands may not be substantially altered by the presence of eucalyptus, but no experimental or anecdotal evidence is available to evaluate this. Woody plant encroachment into grasslands may be more of a concern for changes to fire regime (Russell & McBride 2002), but eucalyptus stands significantly alter abiotic processes, including fire regimes, in previously existing pure grasslands.


Ignition/Flammability: Dickinson & Kirkpatrick (1985) found that live eucalyptus leaves were resistant to combustion, but dead leaves were the most energy-rich component. Eucalyptus globulus juvenile and adult leaves had intermediate flammability in comparison to other species evaluated. They concluded that on the whole, eucalypt dry forest species and fuel components had the greatest tendency to propagate fires relative to species from wet sclerophyll and gully habitats and Casuarina dry forest communities. The East Bay Parks Vegetation Management Plan states that species with oily resins, such as eucalyptus, are far more ignitable than those that lack such characteristics. Eucalyptus is given a high fire hazard rating in comparison with native grass and tree species, which are given low to moderate ratings. Ignition potentials are comparatively low for eucalyptus, meaning it is easy to ignite. On a scale of 1-10, with 1 being most easy to ignite and 10 most difficult, eucalyptus scored 1-2; for comparison, oak/bay woodland 6-8, redwood 8, scrub vegetation 4-8, and grassland vegetation 1-3 (LSA Associates 2009). The 2013 Environmental Impact Statement for the FEMA Hazardous Fire Reduction grant in the East Bay Hills, Eucalyptus globulus flammability (flame length is a proxy for flammability) was estimated at 6-21 feet; for comparison, flame length (feet) for oak/bay woodland is 1-34, Monterey pine 2-16, redwood 7-31, Northern coastal scrub 14-32, and non-native grasslands 2-10 (FEMA 2013). The wide range of flame lengths/flammability is related to the depth of the litter layer below trees, the amount of dead litter within and around trees, stand density and understory, and species characteristics specific to eucalyptus (shedding bark, volatile oils in leaves, aerodynamic leaf structure). The flame lengths in young eucalyptus forests range from 7-31 feet depending on fuel volumes, stand structure, treatment history, and slope. The multiple stems originating from a single trunk create a basket structure that catches dead materials which burn easily and intensely. Ignited leaves and bark are lofted into the air and distribute embers long distances, sending firebrands miles from the fire front to ignite spot fires. Because leaves and bark are large, embers are generally still burning when they land, increasing fire spread; this can occur year-round, although will be limited on foggy summer and winter mornings. Both young and mature eucalyptus stands have a high fire hazard rating (Bossard et al. 2000, LSA Associates 2009). Eucalyptus globulus stands are particularly susceptible to fire during the dry season in California. The bark hangs in strips from the stems and readily carries fire into the crowns, while leaves contain volatile oils that produce a hot fire (Skolmen & Ledig). The flammability of eucalyptus leaf litter may be exacerbated by rare deep freezes, which cause die-back of eucalypts, contributing to fuel loads (Rejmanek & Richardson 2011).


Fuel Loads: Eucalyptus globulus accumulates relatively more fuels for wildfires than grasslands and native tree species due to dropped limbs, bark and leaves. Eucalyptus accumulates 30.84 tons/acre, California bay produces 18.93 tons/acre, and coast live oak accumulates 11.82 tons/acre (National Park Service 2006). Eucalyptus has the greatest tendency to propagate fires via open tree crowns, and long swaying branches that encourage maximum updraft (Esser 1993, LSA Associates 2009). The National Park Service (2006) estimated that 70% of the energy released through combustion of vegetation was due to eucalyptus in the deadly 1991 Oakland Tunnel Fire.





2. Potential changes to erosion and sedimentation rates.


Like many eucalypts in plantations, Eucalyptus globulus litter from leaves and bark may restrict the germination of understory species through the production of allelopathic chemicals. This may result in forests on drier hillsides becoming an erosion risk because of poor development of the understory and exposed soil surface (HEAR 2007). Causal evidence is lacking on this point, but is inferred by low vegetative cover beneath many eucalyptus trees.





3. Alters natural hydrologic regimes in grasslands and invaded forests.


Even under drought conditions Eucalyptus globulus taps into deep water and transpires freely (DiTomaso & Healy 2007), altering soil water tables and water availability to depths of 45 feet and distances of 100 feet from the trunk. Condensation of fog and fog/rain drip alters moisture regimes in grasslands. Despite its ability to withstand prolonged dry summers (Pryor 1976, Florence 1996), Eucalyptus globulus is not particularly drought tolerant (USDA PLANTS), and is only able to survive by tapping into deep water reservoirs; they do not economize in the use of water but have far-reaching root systems to access water, and can extract water from the soil at even higher soil moisture tensions than most mesophytic plants (Pryor 1976, Florence 1996). The trees are more susceptible to drought on shallow soils, and generally only do well in areas with at least 21 inches of annual rainfall if there is a pronounced dry season (such as coastal California) (Esser 1993, Skolmen & Ledig). It has been suggested that one reason for absence of plant life below trees might be due to strong competition for water (HEAR 2007). Thus, in dry areas the benefits of eucalyptus may be outweighed by their negative impacts on soil water due to high water consumption (Rejmanek & Richardson 2011). Williams (2002) states that stream beds become eroded and dewatered by eucalyptus; observations from Bolinas (Marin County) would indicate that this negatively impacts the few remaining coho salmon and steelhead (both threatened).





4. Reduces light availability


Eucalyptus globulus shading appears to create conditions that inhibit the growth of seedlings and most other plants in the understory (DiTomaso & Healy 2007); while any trees growing in crowded conditions would also shade understory plants, the combination of a thick litter layer and allelopathy likely exacerbate the effects of shading (Bossard et al. 2000). Eucalyptus globulus alters light availability in otherwise open grasslands and within invaded native forests which may interfere with the germination and growth of some plant species (Warner 2004). While other native tree stands may also heavily shade the forest floor, they do not alter historic light regimes where they exist; Eucalyptus globulus located in previously unforested areas dramatically alters historic light/shade conditions. However, according to Metcalf (1924), eucalyptus trees have relatively thin crowns and do not make a dense shade.





5. May alter nutrient dynamics


Leaves and branches decompose very slowly (DiTomaso & Healy 2007), potentially altering nutrient dynamics and germination, emergence and growth of seedlings. Causal evidence for this is lacking, although observational evidence would support this impact. However, in riparian areas where eucalyptus was present, Lacan et al. (2010) found no difference in litter breakdown between eucalyptus and native vegetation. Aggangan et al. (1999) reported a reduction in nitrogen mineralization rates in the soil below eucalyptus litter.





5. Allelopathic


Natural unconcentrated fog drip from Eucalyptus globulus inhibits growth of annual grass seedlings (Del Moral & Muller 1969). Unconcentrated stemflow contains sufficient levels of allelopathic chemicals to inhibit germination of some herbs as well, and the volume of stemflow is greater from gum barked species (e.g., Eucalyptus globulus) than fibrous-barked species. The volume of water channeled down the stem is about eight times more than that of falling rain, so soil at the base of trunks evidently receives large quantities of water containing allelopathic compounds. The associated suppression of plant growth seems likely to be due more to allelopathy than water shortage. Thick litter layers may also suppress germination of both Eucalyptus globulus seedlings and other plants (May & Ash 1990). The effects of allelopathy may be exacerbated in areas with low rainfall (Lange & Reynolds 1981). Watson (2000) found that the percentage of native Achillea millefolium and Elymus glaucus seeds germinated was significantly less in the Eucalyptus globulus treatment than in the control and oak (Quercus agrifolia) treatments. In contrast, Bromus carinatus germination and root length were not affected by the eucalyptus treatment relative to the control. Eucalyptus had the greatest germination inhibition of Achillea with germination in the eucalyptus treatment being 11% in comparison to the control and 8% in comparison to the oak treatment. In addition, average time of Achillea germination was delayed in the eucalyptus treatment, at 6.2 days compared to 4.5 in the oak treatment. These results showed that water extracts of Eucalyptus globulus inhibit the growth of Achillea and Elymus. Watson concluded that (quote) restoration projects intended to replace eucalyptus infested habitats with native plants should consider that the possible effects of allelochemicals persisting in the soil may interfere with recruitment and establishment of native species (endquote). A separate experiment with soil from under eucalyptus showed no significant inhibition of germination (although it was lower) relative to the control. The author indicates that winter rains may have leached out allelochemicals and suggests samples should be taken in multiple seasons; this hypothesis is supported by Lange & Reynolds 1981. Molina et al. (1999) also found allelopathic properties of Eucalyptus globulus in Spain, although their results may be different in California (Lacan et al. 2010).



Sources of information:

Aggangan et al. 1999


Bossard et al. 2000


Del Moral & Muller 1969


Dickinson & Kirkpatrick 1985


DiTomaso & Healy 2007


Esser 1993


FEMA 2013


Florence 1996


Griffiths & Villablanca 2013


HEAR 2007


Lacan et al. 2010


Lange & Reynolds 1981


LSA Associates 2009


May & Ash 1990


Metcalf 1924


Molina et al. 1999


National Park Service 2006


Pryor 1976


Rekmanek & Richardson 2011


Russell & McBride 2002


Skolmen & Ledig


USDA PLANTS


Warner 2004


Watson 2000


Williams 2002


Reviewed Scientific Publication B Question 1.2 Impact on plant community composition,
structure, and interactions
Consider the cumulative ecological impact of this species to the plant communities it invades. Give more weight to changes in plant composition, structure, and interactions that involve rare or keystone species or rare community types. Examples of severe impacts include:
- formation of stands dominated (>75% cover) by the species;
- occlusion (>75% cover) of a native canopy, including a water surface, that eliminates or degrades layers below;
- significant reduction or extirpation of populations of one or more native species.

Examples of impacts usually less than severe include:
- reduction in propagule dispersal, seedling recruitment, or survivorship of native species;
- creation of a new structural layer, including substantial thatch or litter, without elimination or replacement of a pre-existing layer;
- change in density or depth of a structural layer;
- change in horizontal distribution patterns or fragmentation of a native community;
- creation of a vector or intermediate host of pests or pathogens that infect native plant species.

Select the one letter below that best describes this species’ impact on community composition, structure and interactions:
A. Severe alteration of plant community composition, structure, or interactions.
B. Moderate alteration of plant community composition.
C. Minor alteration of community composition.
D. Negligible impact known; causes no perceivable change in community composition, structure, or interactions.
U. Unknown.
Identify type of impact or alteration:

While Eucalyptus globulus stands are often monocultures, this is not necessarily due to outcompetition of native trees, but could be because they were planted at high densities for firewood and timber (Griffiths & Villablanca 2013). Impacts (alteration of canopy structure, inhibition and growth of native plant species, displacement of native species) are pronounced in dense stands (Warner 2004), perhaps at least partly due to allelopathy (Del Moral & Muller 1969, Molina et al. 1991, Watson 2000). Some sources indicate that Eucalyptus globulus outcompetes native vegetation as it naturalizes in mesic areas (see review by Griffiths & Villablanca 2013), but experiments have not been found to support this. Moreover, Eucalyptus globulus was primarily planted in grasslands not previously known to support native tree cover. As such, plantings of Eucalyptus globulus stands in grasslands represent a sweeping change to community composition. In grasslands supporting livestock and native ungulates, Eucalyptus globulus has a considerable competitive advantage as compared with most other tree species in that its juvenile foliage is seldom browsed by cattle or sheep. This condition not only caused it to be a popular tree for planting in open grasslands years ago, but it permits natural seedlings to survive in the presence of grazing animals alongside the planted stands (Skolmen & Ledig). Reports of plant diversity within Eucalyptus globulus stands are variable, ranging from depauperate and virtually free of other plant species (Esser 1993, DiTomaso & Healy 2007, Bean & Russo 2014), to reports of several native species being supported in the understory (LSA Associates 2009). Reports that vegetation is sparse under Eucalyptus globulus stands are more frequent, however (Bean & Russo 1989, Esser 1993, Santos 1997b, DiTomaso & Healy 2007, Bean & Russo 2014), and this is likely due to the combined effects of competition for water, tree density/shading, allelopathy, and a thick inhibitory litter layer. Metcalf (1924) reported that Lombardy poplar (Populus nigra), a rapidly-growing non-native tree planted between blue gums, was only able to persist within the stand for 15-20 years before it was overtopped and killed out by the eucalyptus. Without removal of Eucalyptus globulus, plant community composition is not likely to support historic community composition and stands will probably persist, continuing to impact species composition; even with removal, treatments must be repeated multiple times due to resprouting or a flush of seedlings (Skolmen & Ledig, LSA Associates 2009), resulting in continued disturbance and potentially detrimental impacts on community composition for several years. While native plants may be found beneath eucalyptus trees at some locations in California (City of Albany Parks & Recreation Commission 2011), evidence regarding the relative amounts of native cover and trends in native vegetation is lacking. Cover where eucalyptus is present is generally dominated by eucalyptus and other non-native species. San Franciscos Natural Resource Area Management Plan (San Francisco Recreation & Parks 2006) indicates that native trees are relatively rare within the natural areas, and most of the trees within the area, of which eucalyptus was specifically mentioned, are non-native and invasive. The urban forests are dominated by Eucalyptus globulus and in some areas are so dense they have resulted in deteriorating forest health. For example, at Mount Davidson, only 36% of the understory is native, and 29 of 50 species were non-native.


Sources of information:

Bean & Russo 1989


Bean & Russo 2014


City of Albany Parks & Recreation Commission 2011


Del Moral & Muller 1969


DiTomaso & Healy 2007


Esser 1993


Griffiths & Villablanca 2013


LSA Associates 2009


Metcalf 1924


Molina et al. 1991


San Francisco Recreation & Parks 2006


Santos 1997b


Skolmen & Ledig


Warner 2004


Watson 2000


Reviewed Scientific Publication B Question 1.3 Impact on higher trophic levels
Consider the cumulative impact of this species on the animals, fungi, microbes, and other organisms in the communities that it invades. Although a non-native species may provide resources for one or a few native species (e.g. by providing food, nesting sites, etc.), the ranking should be based on the species’ net impact on all native species. Give more weight to changes in composition and interactions involving rare or keystone species or rare community types.
Examples of severe impacts include:
- extirpation or endangerment of an existing native species or population;
- elimination or significant reduction in native species’ nesting or foraging sites, cover, or other critical resources (i.e., native species habitat), including migratory corridors.

Examples of impacts that are usually less than severe include:
- minor reduction in nesting or foraging sites, cover, etc. for native animals;
- minor reduction in habitat connectivity or migratory corridors;
- interference with native pollinators;
- injurious components, such as awns or spines that damage the mouth and gut of native wildlife species, or production of anti-digestive or acutely toxic chemical that can poison native wildlife species.

Select the one letter below that best describes this species’ impact on community composition and interactions:
A. Severe alteration of higher trophic populations, communities, or interactions.
B. Moderate alteration of higher trophic level populations, communities, or interactions.
C. Minor alteration of higher trophic level populations, communities or interactions.
D. Negligible impact; causes no perceivable change in higher trophic level populations, communities, or interactions.
E. Unknown.
Identify type of impact or alteration:

1. Rejmanek & Richardson (2011) state that eucalyptus is a major source of nectar and pollen for honeybees, as well as an important overwintering site for monarch butterflies. Historical records suggest that Monarch butterflies (Danaus plexippus) clustered on native trees prior to the introduction of eucalyptus (Riley & Bush 1881, Riley & Bush 1882, Shepardson 1914). Natural experiment evidence from mixed stands (native trees mixed with eucalyptus) show that Monarchs do not consistently cluster preferentially on eucalyptus, and at times, appear to prefer native trees in some seasons and locations. At overwintering mid-season (~Dec. 31), when microhabitat conditions are probably the least favorable and Monarchs might be more likely to express a preference for the most favorable microclimate, they clustered disproportionately on native trees. Planting of additional native conifers, rather than planting or removal or bluegum eucalyptus, is recommended to enhance microhabitat conditions for monarchs (Griffiths & Villablanca 2013). Management of eucalyptus should take into account the decline in Monarch butterfly populations (Xerces 2014a, 2014b), which is likely due at least in part to declines in overwintering and milkweed habitat (Meade 1999, Oberhauser et al. 2001, Pleasants and Oberhauser 2012). Young or small eucalyptus stands do not offer the same overwintering microhabitat conditions as mature or large stands, and as such there is little ecological reason to protect them (LSA Associates 2009).


2. Impacts on animal species are mixed: some species are found at higher rates in eucalyptus than native tree stands, while others are comparatively less frequent in eucalyptus. It is common for significantly lower species diversity of arthropods, small mammals, and birds to be reported from eucalyptus stands (Warner 2004, Rejmanek & Richardson 2011). For example, in Angel Island State Park, 41 species of birds were observed in native vegetation, but only 30 species in eucalyptus. However, approximately three times more California slender salamanders (Batrachoseps attenuatus) were found in eucalyptus vegetation than in native forests (Rejmanek & Richardson 2011). Sax (2002) found that species richness was nearly identical for invertebrates, amphibians, and birds in native and eucalyptus forests, although rodents had significantly more species in native forests; moreover, species composition was different between the two forest types for all groups. Many birds, mammals, and invertebrates utilize eucalyptus forests at some point, although there is no consistent trend across all species for relative use of eucalyptus as compared to native forests. Raptors may use eucalyptus for nesting in the spring, although no evidence exists regarding rates at which eucalyptus is used in comparison to native vegetation (HEAR 2007, LSA Associates 2009, Rejmanek & Richardson 2011). Macroinvertebrate species diversity did no differ between eucalyptus and native vegetation in riparian areas in California (Lacan et al. 2010). Particularly in large or mature stands, management actions affecting eucalyptus trees should be preceded by a thorough investigation by a wildlife biologist who can identify active nests or other wildlife that might be impacted, so that treatments can be scheduled around sensitive periods (e.g., nesting, overwintering) (LSA Associates 2009). San Franciscos Natural Resource Area Management Plan (San Francisco Recreation & Parks 2006) recommends thinning of eucalyptus and replacement with higher wildlife value native vegetation. At Mt. Davidson, the reed grass/California huckleberry mosaic series is unique in San Francisco and much of Mount Davidson was likely composed of this vegetation type before eucalyptus was planted. In the Elkhorn Slough eucalyptus workshop, David Suddjian (2004) states that habitat quality of eucalyptus depends on many factors, including tree size, stand density, canopy closure, understory development, and type of surrounding habitat. Stands with a mixed age structure at low to moderate densities in proximity to native woodland habitat and water provide the highest value of habitat in terms of eucalyptus stands. In the Monterey Bay region, over 90 birds make regular use of eucalyptus habitat, although many species that nest in eucalyptus appear to do so at lower densities than in native habitats. The nesting bird community is depauperate in eucalyptus, however: decay-resistant wood offers limited opportunities for nesting to woodpeckers and birds that excavate their own holes, and birds that glean insects from foliage are also present at notably lower densities. However, some other bird species nest in eucalyptus preferentially as compared to the remaining native trees, possibly due to the tall growth patterns and large limbs. In Santa Cruz County, great blue herons, great egrets, and double-crested cormorants only nest in eucalyptus, while 85% of red-shouldered and red-tailed hawk nests were found in eucalyptus. However, Suddjian also notes that (quote) eucalyptus stands do not provide an equivalent tradeoff for the oak woodland and deciduous riparian that they have replaced. The breeding bird communities in these native habitats have much better representation by cavity nesting species, foliage-gleaning species, and those that nest on the ground or in understory vegetation. Many of the breeding species that are most representative of oak and riparian habitats make little or no use of eucalyptus in the Monterey Bay region (end quote). In Santa Clara County, Rottenborn (2000) found that red-shouldered hawks nesting in eucalyptus and other non-native tree species had higher fitness due to better stability and cover provided by eucalyptus as compared to native trees. In contrast, Williams (2002) stated that while native birds do use eucalyptus groves, the Point Reyes Bird Observatory (PRBO) found that species diversity there drops by at least 70 percent. Moreover, Williams reported that PRBO found 50 percent of the Anna's hummingbird nests are shaken out by the wind, while only 10 percent of nests are destroyed by wind in native vegetation. The presence of non-native eucalyptus may alter native migratory bird patterns, as rare wintering species are attracted to the eucalyptus food sources, and might not otherwise visit the area (Suddjian 2004); however, no evidence as to whether this has positive or negative impacts was found.


3. No evidence has been found to strongly support the notion that nectar from bluegum gums up and blocks the beaks and airways of birds, leading to suffocation. Anecdotal reports of two dead birds with gummed beaks found in a eucalyptus forest are probably not sufficient to support this concern (see popular press articles by Death of a Million Trees 2013, Hills Conservation Network 2010). Suddjian (2000) reported that (quote) As the birds spend time feeding amid the flowers, the feathers on their faces become matted with a black pitch-like residue (or gum) from the nectar. This affects their ability to maintain those feathers, and in some cases the gum may plug their nostrils or bills, and prevent breathing or feeding. Articles published in the Point Reyes Bird Observatory newsletter (Stallcup 1997) and in Audubon magazine (Williams 2002) have suggested that the effects of this black pitch cause substantial mortality among the North American species that feed at eucalyptus flowers. It seems to be a reasonable conclusion, and Stallcup (1997) cites some instances of mortality. But in my experience, and the experience of a number of other long time field ornithologists, we have seen very little evidence of such mortality. It has been argued that the bird carcasses do not last long on the ground before they are scavenged. However, when observers spend hundreds of hours under these trees over many years but find hardly any evidence of such mortality, then it seems fair to question whether the incidence of mortality is as high as has been suggested. Not all bird carcasses are scavenged rapidly, and large amounts of time under the trees should produces observations of dead birds, if such mortality were a frequent event. Im not making a judgment either way, but I just think more evidence is needed (end quote). In contrast, Williams (2002) stated that (quote) One local bird author I talked to--Rich Stallcup, who writes for the Point Reyes Bird Observatory (PRBO)--told me that over the years he has found about 300 moribund warblers with eucalyptus glue all over their faces. Says Stallcup: (quote) We see a large number of gummed-up Townsend's warblers, yellow-rumped warblers, ruby-crowned kinglets, Anna's and Allen's hummingbirds, and a few Bullock's orioles. Anyone who birds around eucalyptus trees sees it all the time (end quote).


4. In general, organisms will respond differently to eucalyptus trees than they would to original vegetation in grasslands or native forests, and subsequently must alter their behavior according to their needs.



Sources of information:

Death of a Million Trees 2013


Griffiths & Villablanca 2013


HEAR 2007


Hills Conservation Network 2010


LSA Associates 2009


Rejmanek & Richardson 2011


Riley & Bush 1881


Riley & Bush 1882


Rottenborn 2000


Sax 2002


Shepardson 1914


Stallcup 1997


Suddjian 2004


Warner 2004


Williams 2002


Other Published Material D Question 1.4 Impact on genetic integrity
Consider whether the species can hybridize with and influence the proportion of individuals with non-native genes within populations of native species. Mechanisms and possible outcomes include:
- production of fertile or sterile hybrids that can outcompete the native species;
- production of sterile hybrids that lower the reproductive output of the native species.

Select the one letter below that best describes this species’ impact on genetic integrity:
A. Severe (high proportion of individuals).
B. Moderate (medium proportion of individuals).
C. Minor (low proportion of individuals).
D. No known hybridization.
U. Unknown.
Identify impacts:

No congeners native to the United States; no hybridization between non-native Eucalyptus spp. and native plant species in California.


Sources of information:

Baldwin et al. 2012


Calflora 2014


Section 2: Invasiveness

Other Published Material C Question 2.1 Role of anthropogenic and natural disturbance
in establishment
Assess this species’ dependence on disturbance—both human and natural—for establishment in wildlands. Examples of anthropogenic disturbances include:
- grazing, browsing, and rooting by domestic livestock and feral animals;
- altered fire regimes, including fire suppression;
- cultivation;
- silvicultural practices;
- altered hydrology due to dams, diversions, irrigation, etc.;
- roads and trails;
- construction;
- nutrient loading from fertilizers, runoff, etc.

Examples of natural disturbance include:
- wildfire;
- floods;
- landslides;
- windthrow;
- native animal activities such as burrowing, grazing, or browsing.

Select the first letter in the sequence below that describes the ability of this species to invade wildlands:
A. Severe invasive potential—this species can establish independent of any known natural or anthropogenic disturbance.
B. Moderate invasive potential—this species may occasionally establish in undisturbed areas but can readily establish in areas with natural disturbances.
C. Low invasive potential—this species requires anthropogenic disturbance to establish.
D. No perceptible invasive potential—this species does not establish in wildlands (though it may persist from former cultivation).
U. Unknown.
Describe role of disturbance:

Eucalyptus was introduced in 1856 and is now naturalized in California (Esser 1993). In particular, purposeful cultivation is the primary mode of establishment, and little spread into wildlands or native forests occurs (Skolmen & Ledig, Esser 1993, HEAR 2007, LSA Associates 2009, Baldwin et al. 2012). About 40,000 acres were planted to eucalyptus in California, extending from Humboldt County in the north to San Diego County in the south, with best growth in the coastal fog belt in the vicinity of San Francisco (Skolmen & Ledig). Long-distance dispersal is unlikely and very rare when eucalyptus is not located near waterways (Rejmanek & Richardson 2011). Fire promotes eucalyptus (Williams 2002). Germinates best on bare mineral soil (Bean & Russo 1989), and may germinate prolifically after logging or fire (Skolmen & Ledig), so germination within dense forests is difficult (Bean & Russo 1989). However, establishment of eucalyptus in undisturbed forests and scrub has been observed repeatedly (Warner 2004). Within dense stands, litter and allelochemical may inhibit germination of both eucalyptus and other plants (Bean & Russo 1989, Molina et al. 1999, Watson 2000).


Sources of information:

Baldwin et al. 2012


Bean & Russo 1989


Esser 1993


HEAR 2007


LSA Associates 2009


Molina et al. 1999


Rejmanek & Richardson 2011


Skolmen & Ledig


Warner 2004


Watson 2000


Reviewed Scientific Publication C Question 2.2 Local rate of spread with no management
Assess this species’ rate of spread in existing localized infestations where the proportion of available habitat invaded is still small when no management measures are implemented.

Select the one letter below that best describes the rate of spread:
A. Increases rapidly (doubling in <10 years)
B. Increases, but less rapidly
C. Stable
D. Declining
U. Unknown
Describe rate of spread:

Some sources cite that blue gum can spread by seeding into openings in planted stands and near edges, but do not provide specific documentation of such spread, and state that in general it rarely spreads far (Skolmen & Ledig, Esser 1993, HEAR 2007). Potential to spread has been estimated at 10-20 feet in diameter per year under favorable conditions, but this is not documented as an actual observed rate of spread (Bean & Russo 2014), and this is most likely to occur along the coast with summer fog drip (HEAR 2007). Unpublished photodocumentation (Potts 2003) and personal observations (Warner 2004) seem to show expansion of stands far beyond some initial plantings on the coast, but this has not been quantified or monitored, and spread toward the ocean may be unlikely due to high winds. Once a tree matures and produces seed, it can produce a profusion of progeny within a few years doubling of stand area within 10 years possible, but this has not been well documented (Bean & Russo 1989). A quantitative assessment of changes in cover over a 58-year period at three parks in San Francisco, California indicated a decline in eucalyptus cover at all three locations (Chabot, Tilden, and Redwood Regional Parks) (Russell & McBride 2003). CalWeedMapper (2014) allows land owners and managers to report on the status (spreading, spreading/decreasing with management, eradicated) and occurrence of blue gum in the state, although it does not account for duplicate reports or naturally decreasing populations (if any). Of the reported occurrences, approximately 75 are spreading (and all of these occur along the coast), 8 are spreading with management, 18 are decreasing with management, 18 require verification of occurrence, 27 require verification of the species identification, 48 do not indicate the trend in spread (93 if quads requiring verifications are included). In the Central Valley E. globulus does not receive enough moisture to propagate from seed. Therefore, total cover may be increasing, decreasing, or remaining stable at different sites, but there may be no overall change in cover statewide (Warner 2004) even without management.


Sources of information:

Some sources cite that blue gum can spread by seeding into openings in planted stands and near edges, but do not provide specific documentation of such spread, and state that in general it rarely spreads far (Skolmen & Ledig, Esser 1993, HEAR 2007). Potential to spread has been estimated at 10-20 feet in diameter per year under favorable conditions, but this is not documented as an actual observed rate of spread (Bean & Russo 2014), and this is most likely to occur along the coast with summer fog drip (HEAR 2007). Unpublished photodocumentation (Potts 2003) and personal observations (Warner 2004) seem to show expansion of stands far beyond some initial plantings on the coast, but this has not been quantified or monitored, and spread toward the ocean may be unlikely due to high winds. Once a tree matures and produces seed, it can produce a profusion of progeny within a few years doubling of stand area within 10 years possible, but this has not been well documented (Bean & Russo 1989). A quantitative assessment of changes in cover over a 58-year period at three parks in San Francisco, California indicated a decline in eucalyptus cover at all three locations (Chabot, Tilden, and Redwood Regional Parks) (Russell & McBride 2003). CalWeedMapper (2014) allows land owners and managers to report on the status (spreading, spreading/decreasing with management, eradicated) and occurrence of blue gum in the state, although it does not account for duplicate reports or naturally decreasing populations (if any). Of the reported occurrences, approximately 75 are spreading (and all of these occur along the coast), 8 are spreading with management, 18 are decreasing with management, 18 require verification of occurrence, 27 require verification of the species identification, 48 do not indicate the trend in spread (93 if quads requiring verifications are included). In the Central Valley Eucalyptus globulus does not receive enough moisture to propagate from seed. Therefore, total cover may be increasing, decreasing, or remaining stable at different sites, but there may be no overall change in cover statewide (Warner 2004) even without management.


Reviewed Scientific Publication C Question 2.3 Recent trend in total area infested within state
Assess the overall trend in the total area infested by this species statewide. Include current management efforts in this assessment and note them.

Select the one letter below that best describes the current trend:
A. Increasing rapidly (doubling in total range statewide in <10 years)
B. Increasing, but less rapidly
C. Stable
D. Declining
U. Unknown
Describe trend:

Of the reported occurrences on CalWeedMapper (2014), approximately 75 are spreading (and all of these occur along the coast), 8 are spreading with management, 18 are decreasing with management, 18 require verification of occurrence, 27 require verification of the species identification, 48 do not indicate the trend in spread (93 if quads requiring verifications are included). While Angel Island populations were removed by 1996 (Boyd 1997), there is no evidence that current removal/thinning efforts are widespread or widely successful (Jones 2009, Gross 2013, Klatt 2013), although rate of spread is also slow (Esser 1993, HEAR 2007, Forrestel 2008, Rejmanek & Richardson 2011) and may be balanced by removal/thinning projects (Boyd 1997). Bean & Russo (1989) reported that an active Eucalyptus control program was in progress at the Jepson Prairie Preserve since August 1981 but was very unsuccessful (< 5% effectiveness), and new plans to remove trees were put in place in 1986. They also report on active management programs at China Camp state park were little or no spread occurred, and within the East Bay Regional Parks. A quantitative assessment of changes in cover over a 58-year period at three parks in San Francisco, California indicated a decline in eucalyptus cover at all three locations (Chabot, Tilden, and Redwood Regional Parks) (Russell & McBride 2003). Personal observations by Warner (2004) are that removal efforts are roughly equal to expansion of stands.


Sources of information:

Bean & Russo 1989


Boyd 1997


Esser 1993


Forrestel 2008


Gross 2013


HEAR 2007


Jones 2009


Klatt 2013


Rejmanek & Richardson 2011


Russell & McBride 2003


Warner 2004


Other Published Material C Question 2.4 Innate reproductive potential
Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.
Describe key reproductive characteristics:

1. Reaches reproductive maturity in 2 years or less: No


Most sources estimate trees usually begin to produce seeds at 4 to 5 years and yield heavy seed crops in most locations at 3- to 5-year intervals (Skolmen & Ledig, HEAR 2007). However, Metcalf (1924) stated that flowers and fruits could be found on sprouts only two or three years old, although not in great quantities.


2. Dense infestations produce >1,000 viable seed per square meter: Unknown


Sources indicate prolific seed production, but viable seeds produced per square meter are not given. There are 18 to 320 seeds per gram (500 to 9,100/oz) of seeds and chaff, or about 460 clean seeds per gram (13,000/oz) (Skolmen & Ledig). Germination rates are typically very low: a 1% germination rate is good, given the more usual 0.1% germination success rate (Bean & Russo 2014). This does not indicate the amount of viable seed, as germination may be limited by other factors as well (e.g., allelopathy, thick litter layer, moisture, etc).


3. Populations of this species produce seeds every year: Yes


Bluegum eucalyptus in California flowers from November to April during the wet season. The fruit (a distinctive top-shaped woody capsule 15 mm long and 2 cm in diameter) ripens in October to March, about 11 months after flowering. Trees yield heavy seed crops in most locations at 3- to 5-year intervals. This does not indicate whether seed is produced every year and only heavily at several year intervals, or whether seed is produced only at 3- to 5-year intervals (Skolmen & Ledig). It is likely that seed is produced every year, and observations would corroborate this, but published evidence was not found.


4. Seed production sustained over 3 or more months within a population annually: Yes


Bluegum eucalyptus in California flowers from November to April during the wet season. The fruit (a distinctive top-shaped woody capsule 15 mm long and 2 cm in diameter) ripens in October to March, about 11 months after flowering (Skolmen & Ledig).


5. Seeds remain viable in soil for three or more years: No


Germination occurs readily (within 26 days) after seeds are released if conditions are suitable (Skolmen & Ledig). When stored, seeds can remain viable for several years, but in field conditions, seed soil banks are not maintained. Seeds in the soil last less than a year, although resprouting of cut trees makes can make control of eucalypts difficult (Rejmanek & Richardson 2011).


6. Viable seed produced with both self-pollination and cross-pollination: No


When the cap covering the reproductive organs (the operculum) is shed, the anthers have mature pollen, but the stigma does not become receptive until some days later. This sequence impedes self-pollination of an individual flower. Flowers are pollinated by insects, hummingbirds, and other pollen and nectar feeders. There is no evidence that wind plays anything but a minor role in eucalypt pollination. The flowers of eucalypts are not highly specialized for insect pollination (HEAR 2007).


7. Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes: Yes


Bluegum eucalyptus sprouts readily from the bole, from stumps of all sizes and ages, from the lignotuber, and from the roots. The lignotuber can live for many years in the soil after stems die back. Bluegum eucalyptus also reproduces by layering (Esser 1993). No information found as to whether this occurs quickly, or occurs without disturbance.


8. Fragments easily and fragments can become established elsewhere: No


No evidence found.


9. Resprouts readily when cut, grazed, or burned: Yes


Bluegum eucalyptus coppices readily from stumps of all sizes and ages. If the tree is cut down, lignotubers become active and each bud may produce a shoot bearing foliage. Such shoots are commonly known as "sucker growth," or coppice shoots, and a large number are usually formed (Skolmen & Ledig, Bean & Russo 2014).


Sources of information:

Bean & Russo 2014


DiTomaso & Healy 2007


Esser 1993


HEAR 2007


Metcalf 1924


Rejmanek & Richardson 2011


Skolmen & Ledig


Other Published Material C Question 2.5 Potential for human-caused dispersal
Assess whether this species is currently spread—or has high potential to be spread—by direct or indirect human activity. Such activity may enable the species to overcome natural barriers to dispersal that would not be crossed otherwise, or it may simply increase the natural dispersal of the species. Possible mechanisms for dispersal include:
- commercial sales for use in agriculture, ornamental horticulture, or aquariums;
- use as forage, erosion control, or revegetation;
- presence as a contaminant (seeds or propagules) in bulk seed, hay, feed, soil, packing materials, etc.;
- spread along transportation corridors such as highways, railroads, trails, or canals;
- transport on boats or boat trailers.

Select the one letter below that best describes human-caused dispersal and spread:
A. High—there are numerous opportunities for dispersal to new areas.
B. Moderate—human dispersal occurs, but not at a high level.
C. Low—human dispersal is infrequent or inefficient.
D. Does not occur.
U. Unknown.
Identify dispersal mechanisms:

No evidence that recent plantings are extensive or common, although landowners may plant them as ornamentals on a limited scale. Most plantings occurred in the 1800s (Santos 1997a/b, Rejmanek & Richardson 2011). The horticultural variety compacta is a dwarf form that was widely used along California freeways (Skolmen & Ledig). One California nursery was found that reportedly sells seeds (Daves Garden 2014). Overall, the Cal-HIP Plant Right survey of nurseries around California indicated that few nurseries now sell E. globulus (<1%) (DiTomaso 2014).


Sources of information:

Daves Garden 2014


DiTomaso 2014


Rejmanek & Richardson 2011


Santos 1997a


Santos 1997b


Skolmen & Ledig


Reviewed Scientific Publication C Question 2.6 Potential for natural long-distance dispersal
We have chosen 1 km as the threshold of "long-distance." Assess whether this species is frequently spread, or has high potential to be spread, by animals or abiotic mechanisms that can move seed, roots, stems, or other propagules this far. The following are examples of such natural long-distance dispersal mechanisms:
- the species’ fruit or seed is commonly consumed by birds or other animals that travel long distances;
- the species’ fruits or seeds are sticky or burred and cling to feathers or hair of animals;
- the species has buoyant fruits, seeds, or other propagules that are dispersed by flowing water;
- the species has light propagules that promote long-distance wind dispersal;
- The species, or parts of it, can detach and disperse seeds as they are blown long distances (e.g., tumbleweed).

Select the one letter below that best describes natural long-distance dispersal and spread:
A. Frequent long-distance dispersal by animals or abiotic mechanisms.
B. Occasional long-distance dispersal by animals or abiotic mechanisms.
C. Rare dispersal more than 1 km by animals or abiotic mechanisms.
D. No dispersal of more than 1 km by animals or abiotic mechanisms.
U. Unknown.
Identify dispersal mechanisms:

Most seeds are distributed by wind and gravity; calculated dispersal distance from a 40-m (131-ft) height, with winds of 10 km/hr (6 mi/hr), was only 20 m (66 ft) (Skolmen & Ledig). Some seed is moved by such agents as flood, erosion and birds, but usually seed is dropped within 100 feet of the parent tree (Bean & Russo 2014). In studies of plantations in Florida and South Carolina, elevation was the primary predictor of seed dispersal and establishment, with 27 degrees N being the highest latitude at which seedlings established with regularity (Callaham et al. 2013); this suggests that spread is unlikely in the higher latitudes of California. Eucalyptus seeds can be dispersed long distances by water, and as such should not be planted near streams or rivers (Rejmanek & Richardson 2011). In general, however, seed is not easily dispersed over large distances and the spread is likely to be relatively slow, if at all (Skolmen & Ledig, HEAR 2007, Rejmanek & Richardson 2011).


Sources of information:

Bean & Russo 2014


Callaham et al. 2013


HEAR 2007


Rejmanek & Richardson 2011


Skolmen & Ledig


Other Published Material C Question 2.7 Other regions invaded
Assess whether this species has invaded ecological types in other states or countries outside its native range that are analogous to ecological types not yet invaded in your state (see Worksheets B, C, and D for California, Arizona, and Nevada, respectively, in Part IV for lists of ecological types). This information is useful in predicting the likelihood of further spread within your state.

Select the one letter below that best describes the species' invasiveness in other states or countries, outside its native range.
A. This species has invaded 3 or more ecological types elsewhere that exist in your state and are as yet not invaded by this species (e.g. it has invaded Mediterranean grasslands, savanna, and maquis in southern Europe, which are analogous to California grasslands, savanna, and chaparral, respectively).
B. Invades 1 or 2 ecological types that exist but are not yet invaded in your state.
C. Invades elsewhere but only in ecological types that it has already invaded in the state.
D. Not known as an escape anywhere else.
U. Unknown.
Identify other regions:

Eucalyptus globulus has great climatic adaptability, with the most successful introductions worldwide in locations with mild, temperate climates, or to high, cool elevations in tropical areas. The ideal climate has no severe dry season, mean annual rainfall 900 min (35 in), and minimum temperature never below -7 degrees C (20 degrees F). In coastal California, the tree does well in only 530 mm (21 in) rainfall accompanied by a pronounced dry season, primarily because frequent fogs compensate for lack of rain. This also is seen in Chile where deep fertile soils and fogs mitigate the effect of low, seasonal precipitation. In Hawaii, Eucalyptus globulus does best in plantations at about 4,000 ft where the rainfall is 1270 mm (50 in) annually and is evenly distributed or has a winter maximum. Seasonality of rainfall is not of critical importance to the species. Although it generally grows well in countries with a Mediterranean or cold season maximum rainfall, it grows well also in summer rainfall climates of Ethiopia and Argentina (Skolmen & Ledig). In California, Eucalyptus globulus already exists in most suitable sites (Calflora 2014). Metcalf (1924) stated that in California, blue gum was (quote) found almost everywhere in groves, windbreaks, along highways or in lawns and parks (end quote).


Sources of information:

Baldwin et al. 2012


Calflora 2014


Metcalf 1924


Skolmen & Ledig


Section 3: Distribution

Other Published Material A Question 3.1 Ecological amplitude/Range
Refer to Worksheet C and select the one letter below that indicates the number of different ecological types that this species invades.
A. Widespread—the species invades at least three major types or at least six minor types.
B. Moderate—the species invades two major types or five minor types.
C. Limited—the species invades only one major type and two to four minor types.
D. Narrow—the species invades only one minor type.
U. Unknown.
Describe ecological amplitude, identifying date of source information and approximate date of introduction to the state, if known:

In California, establishment in wildlands appears dependent on proximity to planted or otherwise established, seed-producing stands, summer fog OR sufficient year-round groundwater OR irrigation, as well as lack of killing winter frosts. Introduced ca. 1853. Published information on distribution and biology and ecology, and observations.


Sources of information:

Bean & Russo 2014


reviews of online horticultural websites (2014)


Warner 2004


Observational C Question 3.2 Distribution/Peak frequency
To assess distribution, record the letter that corresponds to the highest percent infested score entered in Worksheet C for any ecological type.
Describe distribution:

Fairly common outside cultivation in central and north coastal California; no reports from inland riparian areas, but could become established where moisture is sufficient.


Sources of information:

Warner 2004


Calflora 2014


CalWeedMapper 2014


References

List full citations for all references used in the PAF (short citations such as DiTomaso and Healy 2007 may be used in table above). Websites should include the name of the organization and the date accessed. Personal communications should include the affiliation of the person providing the observation. Enter each reference on a separate line.

1. Aggangan, R. G., A. T. O'Connell, J. F. McGrath, and B. Dell 1999. The effects of Eucalyptus globulus leaf letter on C and N mineralization in soils from pasture and native forest. Soil Biology and Biochemistry 31:1481-1487.


2. Baldwin, B. G., D. H. Goldman, D. J. Keil, R. Patterson, T. J. Rosatti, and D. H. Wilken, eds. 2012 The Jepson manual: Vascular plants of California. 2nd ed. University of California Press, Berkeley and Los Angeles, CA.


3. Bean, C., and M. J. Russo 1989. Elemental stewardship abstract for Eucalyptus globulus (revised). The Nature Conservancy, Arlington, VA. Accessed 24 Mar 2014 at http://www.invasive.org/gist/esadocs/documnts/eucaglo.pdf.


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5. Bossard, C. C., J. M. Randall, and M. C. Hoshovsky 2000. Invasive plants of Californias wildlands. University of California Press, Berkeley, CA.


6. Boyd, D. 1997. Eucalyptus removal on Angel Island. California State Parks, Novato, CA. Accessed 25 Mar 2014 online at http://www.cal-ipc.org/symposia/archive/pdf/1997_symposium_proceedings1936.pdf.


7. Calflora: Information on California plants for education, research, and conservation, with data contributed by public and private institutions and individuals, including the Consortium of Calif. Herbaria. [web application]. 2014. Eucalyptus globulus Labill. Taxon report 3534. The Calflora Database, Berkeley, CA. Accessed 22 Mar 2014 at http://www.calflora.org/.


8. Callaham, Jr., M. A., J. A. Stanturf, W. J. Hammond, D. L. Rockwood, E. S. Wenk, and J. J. OBrien 2013. Survey to evaluate escape of Eucalyptus spp. seedlings from plantations in southeastern USA. International Journal of Forestry Research 2013:1-10.


9. City of Albany Parks & Recreation Commission 2011. Vegetation management plan. Albany Hill and Creekside Park. Preliminary draft. Accessed 31 Mar 2014 online at http://www.albanyca.org/index.aspx?page=1014.


10. Daves Garden 2014. Eucalyptus globulus. Accessed 31 Mar 2014 online at http://davesgarden.com/guides/pf/go/62576/.


11. Death of a Million Trees. 2012. More evidence that eucalypts are not invasive. Accessed 23 Mar 2014 online at http://milliontrees.me/2012/11/06/more-evidence-that-eucalypts-are-not-invasive/.


12. Death of a Million Trees. 2013. Eucalyptus trees do not kill birds. Accessed 20 Mar 2014 online at http://milliontrees.me/2013/11/05/eucalyptus-trees-do-not-kill-birds/.


13. Del Moral, R., and C. H. Muller 1969. Fog drip: A mechanism of toxin transport from Eucalyptus globulus. Bulletin of the Torrey Botanical Club 96:467-475.


14. Dickinson, K. J. M., and J. B. Kirkpatrick 1985. The flammability and energy content of some important plant species and fuel components in the forests of southeastern Tasmania. Journal of Biogeography 12:121-134.


15. DiTomaso, J. M., and E. A. Healy 2007. Tasmanian blue gum. In: Weeds of California and other western states. Vol. 2 Geraniaceae-Zygophllaceae. pp.951-954. Regents of the University of California, Oakland, CA.


16. Esser, Lora L. 1993. Eucalyptus globulus. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [2014, March 20].


17. FEMA 2013. East Bay Hills Hazardous Fire Risk Reduction Environmental Impact Statement. Accessed 24 Mar 2014 online at http://ebheis.cdmims.com/Documents.aspx.


18. Florence, R. G. 1996. Ecology and silviculture of eucalyptus forests. CSIRO Publishing, Victoria, Australia


19. Forrestel, A. 2008. Eucalyptus removal. National Park Service. Accessed 25 Mar 2014 online at http://biomass.forestguild.org/Case-Studies/1001.html.


20. Griffiths, J., and F. Villablanca 2013. Management of monarch butterfly (Danaus plexippus) overwintering habitat: Recommendations based on patterns of tree use. Monarch Alert, California Polytechnic State University, San Luis Obispo, CA.


21. Gross, L. 2013. Eucalyptus: California icon, fire hazard, and invasive species. KQED Science. Accessed 25 Mar 2014 online at http://blogs.kqed.org/science/2013/06/12/eucalyptus-california-icon-fire-hazard-and-invasive-species/.


22. HEAR 2007. Eucalyptus globulus. Accessed 22 Mar 2014 online at http://www.hear.org/pier/wra/pacific/eucalyptus_globulus_htmlwra.htm.


23. Hills Conservation Network. 2010. Birds and blue gum: Love or death? Accessed 20 Mar 2014 online at http://www.hillsconservationnetwork.org/Additional_Resources_files/HCNnewsletterApril2010-D.pdf.


24. Jones, C. 2009. UC Berkeleys eucalyptus removal plan stalled. SFGate. Accessed 25 Mar 2014 online at http://www.sfgate.com/bayarea/article/UC-Berkeley-s-eucalyptus-removal-plan-stalled-3252677.php.


25. Klatt, T./UC Regents 2013. Q&A: Campus environmental manager Tom Klatt talks about hillside tree removal plan. U.C. Berkeley News Center. Accessed 25 Mar 2014 online at http://newscenter.berkeley.edu/2013/05/31/qa-campus-environmental-manager-tom-klatt-talks--about-hillside-tree-removal-plan/.


26. Lacan, I. V. H. Resh, and J. R. McBride 2010 Similar breakdown rates and benthic macroinvertebrate assemblages on native and Eucalyptus globulus leaf litter in Californian streams. Freshwater Biology 55:739-752.


27. Lange, R. T., and T. Reynolds 1981. Halo effects on native vegetation. Transactions of the Royal Society of South Australia 105:213-214.


28. LSA Associates, Inc. 2009. Wildfire hazard reduction and resource management plan. V. Vegetation management plan. East Bay Regional Park District, Oakland, CA. Accessed 23 Mar 2014 online at http://www.ebparks.org/Assets/files/fireplan/ebrpd_whrrm_plan/5-VegMan.pdf.


29. May, F. E., and J. E. Ash 1990. An assessment of the allelopathic potential of Eucalyptus. Australian Journal of Botany 38:245-254.


30. Meade, D. E. 1999. Monarch butterfly overwintering sites in Santa Barbara County, California. County of Santa Barbara Planning and Development Department, Santa Barbara, CA.


31. Metcalf, W. 1924. Growth of eucalyptus in California plantations. Bulletin No. 380. University of California Publications, Berkeley, CA.


32. Moore, P. 1997. Re: Effects on biodiversity from Eucalyptus. Accessed 23 Mar 2014 online at http://www.metla.fi/archive/forest/1997/05/msg00176.html.


33. National Park Service 2006. Eucalyptus. San Francisco Bay Area National Parks, Fire Education Office, Point Reyes Station, CA. Accessed 23 Mar 2014 online at http://biomass.forestguild.org/casestudies/1001/Eucalyptus.pdf.


34. 34. Oberhauser, K. S., M. D. Prysby, H. R. Mattila, D. E. Stanley-Horn, M. K. Sears, G. Dively, E. Olson, J. M. Pleasants, W. F. Lam, and R. Hellmich 2001. Temporal and spatial overlap between monarch larvae and corn pollen. Proceedings of the National Academy of Sciences USA 98:11913-11918.


35. Pleasants, J. M., and K. S. Oberhauser 2012. Milkweed loss in agricultural fields because of herbicide use: Effect on the monarch butterfly population. Insect Conservation and Diversity 6:135-144.


36. Potts, Michael. 2003. About this edition. Caspar News. Accessed 31 Mar 2014 online at http://casparcommons.org/Press/News0305.htm.


37. Pryor, L.D. 1976. The biology of eucalypts. Edward Arnold (Publishers) United, London, UK.


38. Rejmanek, M., and D. M. Richardson 2011. Eucalypts. In: Encyclopedia of biological invasions (Simberloff, D., and M. Rejmanek, eds.) pp. 203-209. University of California Press, Berkeley, CA.


39. Riley, C. V., and A. E. Bush 1881. Trees attractive to butterflies. American Naturalist 15:572.


40. Riley, C. V., and A. E. Bush. 1882. The butterfly trees of Monterey again. American Naturalist 16:64.


41. Rottenborn, S. C. 2000. Nest-site selection and reproductive success of urban red shouldered hawks in central California. Journal of Raptor Research 34:18-25.


42. Russell, W. H., and J. R. McBride 2002. Vegetation change and fire hazard in the San Francisco bay area open spaces. In: Proceedings of the California's 2001 Wildfire Conference: Ten Years After the East Bay Hills Fire; October 10-12, Oakland California. Technical Report 35.01.462 (Blonski, K.S., M.E., and T. J. Morales) pp. 27-38. University of California Forest Products Laboratory, Richmond, CA. Accessed 24 Mar 2014 online at http://www.diablofiresafe.org/pdf/proceedings2001.pdf.


43. Russell, W. H., and J. R. McBride 2003. Landscape scale vegetation-type conversion and fire hazard in the San Francisco bay area open spaces. Landscape and Urban Planning 64:201-208.


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53. Warner, PJ. 2004. Personal observations from 1980-2004 working in and adjacent to eucalyptus stands in Marin, Sonoma, and Mendocino Counties. 707/937-9172; pwarner@mcn.org.


54. Watson, K. 2000. The effect of eucalyptus and oak leaf extracts on California native plants. Masters Thesis, University of California, Berkeley. Accessed 31 Mar 2014 online at http://nature.berkeley.edu/classes/es196/projects/2000final/watson.pdf.


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57. Xerces Society. 2014b. Number of monarch butterflies overwintering in California holds steady, but still well below the 1990s. Accessed 31 Mar 2014 online at http://www.xerces.org/2014/01/31/number-of-monarch-butterflies-overwintering-in-california-holds-steady-but-still-well-below-the-1990s/.


Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less No
Dense infestations produce >1,000 viable seed per square meter Unknown
Populations of this species produce seeds every year. Yes, 1 points
Seed production sustained over 3 or more months within a population annually Yes, 1 points
Seeds remain viable in soil for three or more years No
Viable seed produced with both self-pollination and cross-pollination No
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes No
Fragments easily and fragments can become established elsewhere No
Resprouts readily when cut, grazed, or burned Yes, 1 points
Total points: 3
Total unknowns: 1
Total score: C
Scoring Criteria for Worksheet A
A. High reproductive potential (6 or more points).
B. Moderate reproductive potential (4-5 points).
C. Low reproductive potential (3 points or less and less than 3 Unknowns).
U. Unknown (3 or fewer points and 3 or more Unknowns).
Note any related traits:
Return to Table 2

Worksheet B - Arizona Ecological Types is not included here


Worksheet C - California Ecological Types
 
(sensu Holland 1986)

Major Ecological Types Minor Ecological Types Code
A means >50% of type occurrences are invaded;
B means >20% to 50%;
C means >5% to 20%;
D means present but ≤5%;
U means unknown (unable to estimate percentage of occurrences invaded)
Marine Systemsmarine systems
Freshwater and Estuarine lakes, ponds, reservoirs
Aquatic Systemsrivers, streams, canals
estuaries
Dunescoastal
desert
interior
Scrub and Chaparralcoastal bluff scrub
coastal scrubD. < 5%
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrub
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparralC. 5% - 20%
Grasslands, Vernal Pools, coastal prairieD. < 5%
Meadows, and other Herbvalley and foothill grassland
CommunitiesGreat Basin grassland
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swampC. 5% - 20%
Riparian and Bottomland habitatriparian forestD. < 5%
riparian woodlandD. < 5%
riparian scrub (incl.desert washes)
Woodlandcismontane woodland
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forestC. 5% - 20%
North Coast coniferous forestC. 5% - 20%
closed cone coniferous forest
lower montane coniferous forest
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth)   B
Distribution (highest score)   C
Return to Table 2

Addendum J - Jepson Regions Infested
 
Click here for a map of Jepson regions

Infested Jepson Regions:
Check the boxes to indicate the Jepson floristic provinces in which this species is found.














Addendum L - External Links & Resources

Cal-IPC Plant Profile
The Cal-IPC Plant Profile for this species.
http://www.cal-ipc.org/ip/management/plant_profiles/Eucalyptus_globulus.php
Calflora Plant Profile:
The Calflora Plant Profile for this species.
CalWeedMapper:
Load CalWeedMapper with this species already selected.