biological invasion + ailanthus altissima

Question 1

what are biological invasions?

Answer 1

Spread of species that had been introduced (accidently or deliberately) by humans to a region beyond their natural range
example: tree of heaven (Ailanthus altissima)

Question 2

invasion process -> steps

Answer 2

introduced ->
casual (starts with first regeneration, not necessarily able to establish permanent population) -> established (specie remains in area) -> invasive (spreads further)

Question 3

definition of invasive species

Answer 3

scientific definition: spreading species
in nature conservation: species causing negative impact on biodiversity (or ecosystem services)
legal definition in the EU/D: Species listed as invasive alien species of conservation concern in the EU regulation 1414/2011

Question 4

examples invasive species

Answer 4

Conyza canadensis, Robinia pseudoacacia, Heracleum mantegazzianum

Question 5

biological invasions in city - why important?

Answer 5

patterns:
1. threat to biodiversity
2. cities as hotspots of biological invasions
values/social:
3. xenophobia: fears about alien species
4. hot issue in NGOs, media and urban policies
5. need for evidence based assessments of risks and benefits -> facts and values

Question 6

Why do urban areas have more non-native (and native!) plant species than rural areas?

Answer 6

• for native species: diversity of ecosystems, habitat heterogeneity
• non-native: introduction hotspot because of travel, transport, ornamentals

Question 7

Why does urbanization enhance non-native species?

Answer 7

• cities as hotspots of introduction

- high levels of disturbance encouraging the establishment of many species

Question 8

Example of urban grasslands (lawns): Why are alien species less important in Europe compared to other continents?

Answer 8

• Because its an older tradition in Europe to establish parks/lawns
• European settlers introduced seed mixtures to establish lawns in the colonies
• less native species in these countries that can survive these conditions
• –> so it depends on the vegetation type if non-native species dominate + differences between biogeographical regions

Question 9

Do non-native species have a value for pollinators?

Answer 9

• for pollinators, flower morphology is often more relevant than native status
• can be recommended for pollinators

Question 10

What factors are relevant for pollinators?

Answer 10

• diversity of plants
• presence of woody species
• size of garden
• exposure to sunshine

Question 11

potential of non-native species?

Answer 11

• Non-native species may offer alternatives, in particular when native plants are challenged by harsh urban conditions, e.g. along streets
• spectrum of available native tree species is small, we cannot afford to exclude non-native species

Question 12

Robinia peudoacacia

Answer 12

• adequate for greening streetscapes, tolerates heat/draught
• important for pollinators
• invasive
• can have negative impacts on biodiversity on low productive sites (dry grassland, steppe vegetation) due to N-fixation -> eutrophication -> many rare species are being outcompeted

Question 13

What is one effect of grazing?

Answer 13

• colonization of woody species -> loss of biodiversity

Question 14

Does ailanthus altissima change biodiversity patterns and ecosystems?

Answer 14

Changes to species composition
-> Decrease in biodiversity measures reported
Changes to ecosystem properties
-> Multidirectional changes to soil features

But usually no threat to endangered species

Question 15

Does the precautionary principle justify generalizations?

Answer 15

Yes, if anthropogenic sites were the primary
source of invasions of near-natural sites

No, if invasions of near-natural sites
largely depend on local factors

Question 16

Ecosystem Services of Ailanthus altissima

Answer 16

Provisioning ESS
• Timber, fibers
• Biochemical information
• Honey ...
Regulating ESS
• Bioclimate, air filtration
• Carbon sequestration
• Erosion control, revitalization ...
Cultural ESS
• Aesthetics
• Recreation
• Inspiration ...
Supporting ESS
• Natural processing ...