introduced exotic tree species (terrestrial lecture 13)

Question 1

Where are eucalypts from? Where are they cultivated? Where and how have they become an invasive species?

Answer 1

• Eucalypts originated in Australasia. Now cultivated globally.
• E. camaldulensis (river red gum) cultivated in South Africa for wood production and land reclamation
• became invasive along S. Africa watercourses

Question 2

What are the dominant trees in African/Australian savannah & what is their ecological significance?

Answer 2

Africa - Acacia, flat high canopy, more shade
Australia - Eucalypts, rounder foliage coverage, less shade

• less shade = more grass growth = more fuel for fire = savannah extends into wetter areas

Question 3

Phylogeographic history

• dispersal
• niche occupation
• ecological significance of dominant plant groups

Answer 3

• global distribution of species limited by dispersal
• barriers for dispersal/migration can be geographic/ecological/environmental
• particular phylogenetic groups of each life form do not fill entire niche space
• different continents have different dominant plant types, influencing ecosystem structure and function

Question 4

Afforestation and exotics

global challenges

• the bonn challenge (2011)
• the new york declaration (2012)

national commitments

• 20x20
• afr100
• development funding

unintended outcomes

Answer 4

Global challenges:

• bonn challenge: 150m hectares of deforested/degraded land restored by 2020
• new york declaration: 350m hectares restored, halve natural forest loss, zero net deforestation by 2030

National commitments:

• 20x20: restore 20m hectares in Latin American and Caribbean nations by 2020
• AFR100: 100m hectares in Africa by 2030

Developmental funding: $1.5B development funding for landscape restoration, e.g. REDD+

Unintended outcomes:

• afforestation with exotic species to meet goals
• 78,000km2 (2% Brazilian forest cover) is eucalypt and pine plantation
• afforestation of native grassland

Question 5

Importance native grassy ecosystems:

• comparison w degraded ecosystems
• value compared w forests: biodiversity
• C storage
• importance for water supply
• social importance

Answer 5

• native systems: maintained by fire, high C and biodiversity
• degraded: result of deforestation, low C and biodiversity
• biodiversity can approach that of tropical forests
• stores most of C underground: vegetation + soil (up to 1m depth) = 265.0MgCha-1
• contain the headwaters of hydrological basins that serve millions of people
• pasture for grazing domestic animals
• firewood harvesting/charcoal production
• tourism revenue: charismatic animals

Question 6

How does afforestation with exotic species degrade native grasslands?

Answer 6

• degrades underground C stocks (Berthrong et al., 2012)
• compromises water resources (Farley et al., 2005)
• e.g. invasive river red gum along S. African watercourses reduce groundwater recharge
• Working for Water volunteers in South Africa remove alien trees to restore streamflow and groundwater recharge
• reduced biodiversity
• no recovery after afforestation
  
  • ground plant flora did not return even 17 years
    after a pine plantation was cleared

Question 7

How should restoration be targeted?

Answer 7

• should not be targeted at native grassy ecosystems, but systems that are grassland as a result of deforestation
• low biodiversity and depleted carbon

Question 8

How to recognise a native grassy system?

Answer 8

• intact disturbance regimes, e.g. fire
• high species diversity
• underground storage and resprouting capacity
• fire adaptations, e.g. resprouting from underground buds, fire-insulated bark, fire simulated flowering

Question 9

What is is Taita hills project, Kenya?

Answer 9

• accounts for avoided conversion of grasslands
• generates REDD+ carbon offsets from protection of forest/savannah mosaics
• focus on soil carbon, conserving biodiversity and sustainable charcoal production
• conservation within existing mechanisms