BGC & SusMan 8.12.14: Impacts & management of invasives Prof. Nina Buchmann, Institute of Agricultural Sciences

What is wrong in these pictures? Eichhornia crassipes (water hyacinth)

Pueraria lobata (kudzu, Fabaceae) (also seen in Southern Switzerland)

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What do these species have in common? Further examples:

nutria

rat wasp

mussels (GISP; Rangi 2006)

BGC & SusMan – Class 11 Impacts and management of invasive species • • • • • •

Definitions: Alien, exotic, invasive species Invasions and invasibility Impacts of invasion Example: Bromus tectorum Example: Rabbits in Australia Management of invasives

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What are „invasive species“? Several terms are available and used: • Archaephytes: have arrived before 1500. • Neophytes: have arrived/been introduced after 1500. • Alien, non-native, exotic species: Species have not evolved in the region or have reached the region with (direct or indirect) help of humans. Most of them do not persist for a long time without human assistance. • Naturalized species: Aliens that do not necessarily spread. • Invasive species, invaders: Species with ability to spread. • Harmful invaders: exotic weeds, pests.

Steps towards a „biological invasion“ Arrival

Alien species

Establishment

(Schulze et al. 2002, p. 583)

Naturalization

Naturalized sp.

Spread

Invasive species

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Fraction of alien species

Alien but not invasive: e.g., Robinia, Douglas Fir, other nonnative conifers, Red Oak, Horse Chestnut or Liriodendron.

Some invasive species in Switzerland

Watch out: Assignment might change due to different perspectives! Ex.: Robinia (Forum Biodiversität Schweiz 2004, p.106)

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„Dirty dozen“ The Dirty Dozen - America's Least Wanted Alien Species • • • • • • • • • • • •

flathead catfish green crab purple loosestrife (Lythrum salicaria) brown tree snake rosy wolfsnail Miconia (Miconia calvescens) tamarisk (Tamarix spp.) balsam woolly adelgid Tamarix Chinese tallow zebra mussel hydrilla leafy spurge (Euphorbia esula)

Lythrum Miconia

How do invasions take place? For example:

(GISP; Rangi 2006)

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Do species only invade once?

Lantana camara

(Harper et al. 2006, p. 195)

Lantana in India (Nilgiri National Park)

Lantana camara

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Prone to invasion? • Often mesic environments seem to be more invasible than more extreme environments (enough resources). • Xeric: too dry for seed germination and seedling establishment (abiotic resistance) • Wet terrestrial: too dark for newcomers due to fast growth of resident vegetation (biotic resistance) • But: many exceptions, e.g., Bromus in arid rangelands, Brassica in Mojave and Sonoran desert, …

Invasibility = vulnerability to invasion

= properties of organisms and habitats (Rejmánek et al. 2005)

Factors enhancing invasibility

BGC (Rejmánek et al. 2005)

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What makes a plant invader successful?

(Rejmánek et al. 2005) Q

What are the impacts of invasions? On biodiversity: changing population size, community composition, enhancing acclimation, changing genetics, … On BGC: changing nutrient and water cycles, disturbance regimes (e.g., fire, erosion, flooding), … On management: changing yields, weed/pest control, … On economics: changing profit, creating additional costs for monitoring or control, … On society: creating health problems, changing land use Might be modulated by climatic conditions

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Bioenergy plants and invasives?

(Raghu et al. 2008)

Some economic impacts of invasions

(GISP; Rangi 2006)

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How to study? • Monitoring over time or space (space-for-timesubstitution) • Chronosequences • Archives • Addition experiments • Removal experiments

(Strayer et al. 2006)

Example: Spread of Bromus tectorum

Annual cheatgrass invading the perennial prairie/steppe vegetation of the Great Basin during the 19th century 1981 1889 (Mack 1981)

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One of the most significant pl. invasions in N‘Am. Mines, railroads, cattle trails, local overgrazing met dry annual grasslands without sodforming grasses (instead biological crusts) and without undulates (no bisons, antelopes, …). Plowing for crops (winter wheat) brought bromes.

(Internet 2006)

Successful Bromus Winter annual plant with fall germination, life cycle finished in spring, originally from ruderal and sand dune communities in Eurasia: • needed open ground to germinate (trampling by overgrazing), • shift from spring to winter wheat with autumn grazing helped further (no light competition for germinating seedlings in the fall plus open ground) • Anatomy of seeds: great for animal dispersal • Resistant seed bank in the soil:

(Mack 1981)

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Impacts of Bromus

Large dead biomass accumulation in spring after annual life cycle has finished, fires spread rapidly with increasing summer temperatures, no negative effect on Bromus (already dead), seeds survive, but fire kills competitors (other perennial grasses or shrubs/trees). (D‘Antonio and Vitousek 1992)

Impacts on BGC: grass-fueled fires

Fire cycle per site shortened from 60 – 110 yrs to only 3-4 yrs with Bromus present!!! Thus, occasional fire favored Bromus during invasion, after invasion fires more frequent. Further consequences: flooding and erosion. (D‘Antonio and Vitousek 1992)

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Impacts on BGC: litter production

Study in Canyonlands National Park, Utah, after 2 yrs of invasion!

(Evans et al. 2001)

Impacts on BGC: N dynamics

Plus: net N mineralization was reduced > 50% in sites with Bromus, thus further reducing the N availability in these arid grasslands

(Evans et al. 2001)

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Management of invasives

More promising: • Prevention programs • Education materials and activitites • Economical and sustainable multi-year integrated approaches (DiTomaso 2000)

Management of invasive rabbits in AUS • •

• •

• •

Australia was originally rabbit free, rabbits were introduced in 1788 by the first British settlers Release of 24 wild rabbits in 1859 “The introduction of a few rabbits could do little harm and might provide a touch of home, in addition to a spot of hunting.” Spread widely and fast, 15 to >100 km per year 1926: 10 billion rabbits

Impacts: loss of plant diversity, erosion, harvests loss, loss of grazing land for livestock, … Huge economic impact: in VIC alone, in 1998 estimated as $360 million dollars (CSIRO; Richardson 2001; RFA; VIC government)

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Management of invasive rabbits in AUS • •

Controls: hunting, poisoning, trapping, destruction of warrens Rabbit proof fences, built from 1903 to 1907, > 3200 km lang

(Fenner 2010; RFA)

Management of invasive rabbits in AUS •

Myxoma virus released between 1937 and 1950 after decades of testing for rabbit specificity: reduced population from 600 mio to about 100 mio by the 1990s resistance developed

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Escape of rabbit haemorraghic disease virus RHDV (i.e., rabbit calicivirus) in 1995 from an island in SA where tests had been done, most effective in dry, arid areas, less in cool, wet areas In 1998: Rabbit-Free Australia foundation (RFA) (Fenner 2010; RFA)

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Rabbit-Free Australia (RFA)

Partners Research, Education

Awareness

(http://www.rabbitfreeaustralia.org)

http://www.dpi.vic.gov.au/agriculture

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