Eucalypts Overview and Taxonomy

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Questions and Answers

What is one of the main concerns regarding eucalypt species?

  • High seed production rates.
  • Resistance to pests.
  • Excessive water use. (correct)
  • Rapid growth in urban settings.

What regenerative strategy is associated with Eucalyptus fraxinoides?

  • Obligate seeder (correct)
  • Lignotuber sprouter
  • Seed bank performer
  • Root sucker

Which of the following is NOT one of the specified concerns related to eucalypt species?

  • Suppression of ground vegetation
  • High soil fertility (correct)
  • Poor wildlife value
  • Increased fire hazard

Which eucalypt regenerative strategy is common to three of the listed species?

<p>Lignotuber sprouter (A)</p> Signup and view all the answers

How many species of eucalypts are classified as invasive in at least one region?

<p>Six species (C)</p> Signup and view all the answers

What is the total area of eucalyptus plantations estimated to be in 2008?

<p>19.6 million ha (D)</p> Signup and view all the answers

Which genus of trees is more extensively cultivated than eucalypts?

<p>Pinus (pines) (A)</p> Signup and view all the answers

Which region had the highest extent of eucalyptus plantations in the 1990s?

<p>Americas (A)</p> Signup and view all the answers

What factor is indicated by lower terminal velocity values in seeds?

<p>Extended seed dispersal distance (B)</p> Signup and view all the answers

In which year did the total area of eucalyptus plantations increase to more than four times the global total from the 1970s?

<p>1990s (B)</p> Signup and view all the answers

Which country is mentioned as having the highest eucalyptus plantation area in the Americas?

<p>Brazil (D)</p> Signup and view all the answers

What is the approximate area of eucalyptus plantations in Oceania?

<p>0.9 million ha (B)</p> Signup and view all the answers

Which ecological consequence is associated with eucalyptus plantations as mentioned in the content?

<p>High mortality of seedlings (B)</p> Signup and view all the answers

What is the primary classification of the genus Eucalyptus?

<p>Monocalyptus and Symphyomyrtus (A)</p> Signup and view all the answers

How many species does the subgenus Symphyomyrtus contain?

<p>360 species (C)</p> Signup and view all the answers

Which of the following statements about naturalized eucalypts is accurate?

<p>Naturalized eucalypts belong almost exclusively to two subgenera. (D)</p> Signup and view all the answers

What is indicated by the term 'monotypic' in relation to subgenera?

<p>A subgenus with only one species. (C)</p> Signup and view all the answers

Which authors contributed to the publication on Eucalypts?

<p>Marcel Rejmanek and David Mark Richardson (B)</p> Signup and view all the answers

What height range do most eucalypts typically fall under?

<p>10 to over 50 meters (D)</p> Signup and view all the answers

What is a characteristic of the subgenus Eucalyptus in the context of Eucalyptus classifications?

<p>It includes more than 140 species. (C)</p> Signup and view all the answers

Which of the following subgenera of Eucalyptus is considered monotypic?

<p>Angophora (D)</p> Signup and view all the answers

Which subgenus does the species Eucalyptus camaldulensis belong to?

<p>Eucalyptus (A)</p> Signup and view all the answers

Which of the following species is classified as an obligate seeder?

<p>Symphyomyrtus spathulata (D)</p> Signup and view all the answers

What is a common characteristic of species in the subgenus Symphyomyrtus compared to those in Eucalyptus?

<p>Shorter terminal velocities (B)</p> Signup and view all the answers

Which of the following statements is true regarding the species classified as lignotuber sprouters?

<p>None are classified as invasive in at least one country. (D)</p> Signup and view all the answers

What can be inferred about the seed dispersal of Symphyomyrtus species?

<p>They can be dispersed longer distances by wind due to their smaller size. (A)</p> Signup and view all the answers

Which Eucalyptus species is explicitly mentioned as having no conclusive evidence of naturalization?

<p>Eucalyptus camaldulensis (B)</p> Signup and view all the answers

How do the seeds of the subgenus Eucalyptus generally compare to those of Symphyomyrtus?

<p>They are generally larger. (A)</p> Signup and view all the answers

Which factor is pointed out as primary in determining invasive species classification?

<p>Seed dispersal methods (C)</p> Signup and view all the answers

What characteristic of eucalypts contributes to their potential spread along rivers and streams?

<p>Seeds can be dispersed by running water (B)</p> Signup and view all the answers

Which factor is NOT mentioned as a concern regarding the planting of eucalypts near water bodies?

<p>Nutrient depletion of soil (C)</p> Signup and view all the answers

What may be a reason for the extensive planting of invasive species like eucalypts?

<p>Growth and timber characteristics (A)</p> Signup and view all the answers

What is suggested about the classification of eucalypts in terms of invasiveness?

<p>They are generally considered noninvasive. (A)</p> Signup and view all the answers

Which of the following statements about eucalypt seedlings is true?

<p>They establish spontaneously in suitable habitats. (A)</p> Signup and view all the answers

What environmental issue arises from planting eucalypts near rivers?

<p>Potential spread of their seedlings due to flooding (A)</p> Signup and view all the answers

Regarding the habitats suitable for eucalypt seedling establishment, which statement is accurate?

<p>Flooded or eroded banks are ideal habitats. (D)</p> Signup and view all the answers

What is a limitation to the planting of eucalypts near freshwater sources?

<p>Their seeds can be dispersed far by water. (A)</p> Signup and view all the answers

What is one potential negative impact of consecutive cutting cycles of eucalypts?

<p>Long-term yield decline (B)</p> Signup and view all the answers

Which eucalypt species are noted for their contribution to the honey industry?

<p>Eucalyptus camaldulensis and Eucalyptus cladocalyx (D)</p> Signup and view all the answers

What practice is imperative for maintaining site quality and biomass production of eucalypts?

<p>Prohibiting or controlling litter raking (B)</p> Signup and view all the answers

How does the species diversity in eucalypt plantations compare to that of native vegetation?

<p>Lower species diversity in eucalypt plantations (C)</p> Signup and view all the answers

What is a potential benefit of growing eucalypts on degraded soils?

<p>Reduction of pressure on native forests (A)</p> Signup and view all the answers

Which of the following is true about unmanaged stands of eucalypts?

<p>They accumulate highly flammable dead material (B)</p> Signup and view all the answers

What factor contributed to the discussions regarding the intensity of the Berkeley–Oakland Hills fire in 1991?

<p>Specific eucalypt species' characteristics (D)</p> Signup and view all the answers

Which statement about the environment where eucalypts are often grown is true?

<p>They are often grown on abandoned agricultural land (A)</p> Signup and view all the answers

Flashcards

Eucalypts

A genus of trees, comprising numerous species.

Subgenera of Eucalyptus

Eucalyptus is divided into distinct groups, some containing single species.

Monotypic subgenera

Subgenera with only one species.

Eucalyptus subgenera (Eucalyptus)

One of the largest subgenera of Eucalyptus, containing more than 140 species.

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Eucalyptus subgenera (Symphyomyrtus)

One of the largest Eucalyptus subgenera, containing more than 360 species.

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Naturalized eucalypts

Eucalypts that have spread outside their native area, often becoming invasive species.

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Tree Height (Eucalypts)

Most Eucalypts are trees ranging in height from 10 meters to over 50 meters.

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Angophora and Corymbia

Often treated as subgenera of Eucalyptus (sensu lato).

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Eucalyptus Species

Different types of Eucalyptus trees, with over 360 known species.

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Regenerative Strategy

How a Eucalyptus species reproduces and spreads, often by seeds or sprouting from existing roots.

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Invasive Species

Plants (or animals) that spread aggressively, often outcompeting native species in an area.

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Concerns about Eucalyptus Plantations

Potential negative impacts of large-scale eucalyptus plantations, including water use, soil erosion, and fire hazards.

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Allelopathic Effects

When a plant releases chemicals into the soil that inhibit the growth of other nearby plants.

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Eucalyptus Plantations

Large-scale cultivation of eucalyptus trees outside of Australia.

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Global Eucalyptus Extent (1990s)

15.6 million hectares of eucalyptus plantations.

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Eucalyptus Plantations (2008)

Estimated at 19.6 million hectares.

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High Seedling Mortality

High death rates of young eucalyptus seedlings.

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Eucalyptus Seed Terminal Velocity

Speed at which eucalyptus seeds fall through the air, impacting their dispersal range.

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Pinus Plantations

Cultivated trees more widely grown than eucalyptus.

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Global Plantations (1970s)

Eucalyptus global plantation size significantly less than in the 1990s.

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Eucalyptus Global Spread Areas

Various regions have large-scale Eucalyptus plantations.

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Eucalypts as Invasive Species?

While eucalypts are widely planted, they are considered relatively non-invasive. However, their planting near rivers can be problematic due to their potential to spread and compete with native species.

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Regenerative Strategies of Eucalypts

Eucalypts have efficient methods of reproduction and spread, such as by seeds and sprouting from roots, contributing to their resilience.

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Correlation of Planting and Invasiveness

Extensive planting of eucalyptus is linked to their invasive potential. Traits like rapid growth and strong roots contribute to their ability to spread.

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Impact of Water on Eucalypts

Eucalypts can spread through water, as their seeds can be dispersed long distances by rivers and streams.

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Suitable Habitats for Eucalypts

Eucalypts are most likely to establish themselves in areas with temporarily flooded or eroded banks, making river edges vulnerable.

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Temporary Flooding and Eucalypts

The presence of temporary floods or erosion along riverbanks creates conditions favorable for the establishment of eucalyptus seedlings.

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Lignotuber sprouter

A type of Eucalyptus tree that regrows from a woody base called a lignotuber, making it resistant to fire and disturbances.

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Obligate seeder

A type of Eucalyptus that only reproduces by seed, relying on dispersal for new growth.

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Subgenus Symphyomyrtus

A diverse group within the Eucalyptus genus, containing over 360 species, known for their smaller seeds and a tendency to be more invasive.

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Subgenus Eucalyptus

A group of Eucalyptus species, including over 140 species, known for their larger seeds and a lesser tendency to be invasive.

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Terminal velocity

The speed at which seeds fall through the air, affecting how far they can travel from the parent tree.

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Invasive Eucalyptus species

Eucalyptus species that have invaded ecosystems outside their native range, potentially harming native species.

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Eucalyptus species and invasiveness

Eucalyptus species with smaller seeds, belonging to the subgenus Symphyomyrtus, are more likely to be invasive due to their ability to be dispersed further by wind.

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Lignotuber sprouting and invasiveness

No Eucalyptus species classified as invasive is a straight lignotuber sprouter, suggesting that seed dispersal is crucial to invasive behavior.

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Eucalypts and degraded soils

In many tropical countries, eucalypts are grown on degraded soils that are unsuitable for native trees, often abandoned agricultural land. This practice can be beneficial as it reduces pressure on natural forests.

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Eucalypt cutting cycles

Consecutive cutting cycles of eucalypts, especially when done frequently, can lead to reduced yields and degradation of the forest site over time. This happens due to soil depletion and damage.

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Sustainable eucalypt management

To ensure long-term site quality and sustainability when harvesting eucalypts, longer cutting cycles and controlled litter raking are crucial. This allows the soil to recover and the forest to thrive.

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Eucalypts and honeybees

Eucalypts are a significant source of nectar and pollen for honeybees. This is especially true for species like E. camaldulensis and E. cladocalyx because their flowering is abundant and lasts for a long time.

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Eucalypts and biodiversity

While providing resources for honeybees, eucalypts often lead to lower biodiversity compared to native vegetation. This is observed among arthropods, small mammals, and birds.

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Fire risk in eucalypt stands

Unmanaged stands of some eucalypt species can accumulate large amounts of flammable dead material, raising the risk of intense fires. This is an important consideration when planting or managing eucalypt forests.

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Eucalyptus globulus and the Berkeley–Oakland Hills fire

The role of Tasmanian blue gum (Eucalyptus globulus) in the 1991 Berkeley–Oakland Hills fire is debated, but its potential contribution to the intensity of the fire is a significant concern.

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Study Notes

Eucalypts

  • Over 800 species of eucalypts (Angophora, Corymbia, Eucalyptus) are native to Australia and some Pacific islands
  • Important solid timber and paper pulp forestry trees
  • Second most commonly cultivated exotic trees after pines
  • Over 70 species are naturalized outside their native range
  • Less invasive than many other widely cultivated trees and shrubs

Taxonomy, Growth Forms, Regenerative Strategies, and Habitats

  • Classified into three genera: Angophora (14 species), Corymbia (113 species), Eucalyptus (over 740 species)
  • Eucalyptus (sensu stricto) is currently divided into 10 subgenera, 6 of which have only one species
  • Primarily tall trees (10–50+m), some are "mallees" (multi-stemmed, generally under 10 m), and some are shrubs
  • Tallest non-coniferous trees in the world
  • Maximum age estimated between 400–600 years

Eucalyptus Breeding System

  • Mixed mating with preferential outcrossing
  • Reduction in fruit production, seed set, and seedling vigor after self-pollination
  • Pollination primarily by bees, wasps, birds, mammals or wind

Eucalyptus Adaptations to Fire

  • Lignotubers: woody swellings at the base of the stem, for sprouting after fire
  • Epicormic buds: buds in the outer bark, for sprouting new branches from stems
  • Serotiny: seeds kept in fruits and released after fire

Seeds and Seedlings

  • Majority produce seeds with no obvious endosperm.
  • Seeds usually are small (1–3mm), with low weight (0.5-3 mg)
  • Seedlings depend on cotyledon photosynthesis and quick root growth in suitable substrate
  • Seeds can be shed in large numbers (up to 4,000 seeds per m²)

Cultivation

  • Used for farm construction, fencing, firewood since early European settlement
  • First cultivated species ( E.obliqua) was in 1774 at Kew Botanic Gardens
  • Widely cultivated in tropical, subtropical, and temperate countries for timber, plywood, fiberboard, pulp, poles, firewood, charcoal production, essential oils, honey and for shelter
  • Globally, total plantation area is over 19.6 million hectares (larger than Washington State).

Naturalized Species

  • Naturalized species mostly belong to the two largest subgenera (Eucalyptus, Symphyomyrtus)
  • Extensive planting has resulted in widespread distribution, but they don't have the same impact as some other species as invaders. Their high success rate is lower compared to other extensively planted trees (pines).
  • Reasons for limited invasiveness include relatively limited seed dispersal, high mortality of seedlings, and lack of compatible ectomycorrhizal fungi.

Invasiveness of Eucalypts

  • Eucalypts are not considered highly invasive
  • Concerns include water consumption, ground vegetation suppression, increase in fire hazard, and lower wildlife value compared to native species.

Environmental Controversies and Control Methods

  • Concerns about water use, soil erosion, and fire hazard
  • Relatively non-invasive, spreading is limited
  • Control by cutting back regrowth, application of herbicides to stumps
  • Not usually considered amenable to biological control due to their economic value as timber and/or ornamental trees

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