Luke Flory University of Florida

florylab.com

The Biology and Ecology of Invasive Plants

What is an invasive species?

Synonyms: exotic non-indigenous non-native

(1) non-native to the ecosystem under consideration AND (2) whose introduction causes or is likely to cause

economic or environmental harm or harm to human health

(Federal Executive Order 13112, signed by Pres. Clinton 1999)

Historical context

Charles Elton, 1958

Elton, 1958

~ 50,000 species are non-native to the U.S. (includes cultivated and domesticated species) ~ 5000 plants ~ 20 mammals ~ 97 birds ~ 53 amphibians and reptiles ~ 138 fish ~ 4500 arthropods ~ 11 earthworms ~ 88 molluscs undetermined numbers of pathogens, microbes, diseases

In the U.S.A.

In Florida • ~$40 mil spent on

management per year • 1.7 mil acres invaded

by some non-native species

• >500 non-native fish and wildlife

Why are there so many introduced species?

Increased global travel and trade

Intentional or accidental

dispersal of species

Declines in biodiversity and

changes in ecosystem functions

US and international flights Shipping cargo internationally

The stages of biological invasions

Adapted from Lockwood et al, 2007

Transport

Death

Introduction

Fail

Establish

Remain

Spread Impact

Ecosystems

Communities

Local or regional

Management/eradication

Recovery of native community

Biological invasions as agents of global change

Potential effects: • Declines in biodiversity, habitat quality,

and system productivity • Altered succession patterns • Changes in ecosystem functions • Pathogen epidemics/outbreaks

* Invasions provide unique opportunities for ecological and evolutionary research

Invasive species as ‘drivers’ vs. ‘passengers’

Native community

Invaded community

diversity

native abundance

altered ecosystem processes

Methods to evaluate the community and ecosystem consequences of plant invasions

1. Comparative – invaded and invader-free areas Advantage: Quick and easy, broad patterns

Disadvantage: Cause and effect may be hard to disentangle

2. Removal experiments Advantage: Method may alter results, some effects cannot be removed

Disadvantage: Native species may respond to removal

3. Experimental invasions Advantage: Provide controlled, realistic situation

Disadvantage: Ethical concerns

Patterns in the use of research methods to evaluate impacts of plant invasions

• Literature search 1990 – 2010 • 207 published studies

Year

1990 1995 2000 2005 2010

# st

udie

s

0

10

20

30

40

Year

# st

udie

s

0

2

4

6

8

10

12

14Experimental

removal Experimental

addition

Year1990 1995 2000 2005 2010

# st

udie

s

0

2

4

6

8

10

12

14Model

1990 1995 2000 2005 2010

Observational

a) b)

c) d)

Impacts of plant invasions

1. Community effects a. Biodiversity b. Productivity c. Composition d. Habitat quality e. Succession patterns

2. Ecosystem effects

a. Nutrient (C, N, P) cycling b. Hydrology, water availability c. Erosion patterns d. Fire regimes

Alvarez and Cushman, 2002

Cape ivy removal experiment

Cape ivy invasion, California

Microstegium vimineum (stiltgrass)

• Shade tolerant annual grass

• May fill “empty niche”

• Native to eastern Asia

• Few herbivores/pathogens First documentedpre 1940

1940-1960post 1960

1920

-198

0

post

1980

pre 1

920

invasions < 3 yrs old

Characteristics

tree seeds

tree saplings

tree saplings

+ Microstegium

tree seeds

+ Microstegium

x 8 replicates

Design: Invasion experiment

All plots

9 tree sp

12 herb sp

Fall 2009

Control

Invaded

IU Research and Teaching Preserve Bayles Road

Planting, fall 2005

2006 2007

Div

ersi

ty (e

H' )

2

3

4

5

6

7

8

*

2006 2007 2008

Nat

ive

biom

ass

(g)

0

5

10

15

20

25

30

35

40

45ControlInvaded

** *

Results: Microstegium reduces native plant productivity and diversity

Flory, S.L and K. Clay Biological Invasions, 2010

Invaded

Control

Microstegium inhibits small-seeded tree regeneration

Sweetgum Tulip poplar Green ash

Tree

see

dlin

gs/p

lot

0

2

20

25

30

ControlInvaded

A

B

A

A

A

A

Small-seeded species

Hickory

Pin oa

k

Black w

alnut

Whit

e oak

Bur oa

kTr

ees

seed

ling

surv

ival

0.00

0.25

0.50

0.75

1.00

ControlInvaded

Large-seeded species

survival of small-seeded species -No effect on large-seeded species

- additional research needed on oak spp.

Microstegium reduces natural tree regeneration

All spe

cies

Box el

der

Red m

aple

Spiceb

ush

Dogwoo

d

Tree

see

dlin

gs/p

lot

0

1

2

102030405060

ControlInvaded

P = 0.06

A

B

A

AA

A

BB

>400% greater natural tree regeneration in control plots –

but varies by species

Microstegium facilitates further invasions

• Alliaria produced 316% greater total biomass and 214% more total fruits in invaded compared to control plots

• = “invasional meltdown”

Microstegium vimineum

Alliaria petiolata

Impacts of plant invasions

1. Community effects a. Biodiversity b. Productivity c. Composition d. Habitat quality e. Succession patterns

2. Ecosystem effects

a. Nutrient (C, N, P) cycling b. Hydrology, water availability c. Erosion patterns d. Fire regimes

Sedge meadow Invaded by reed canary grass

Reed canary grass (Phalaris arundinacea)

Ecosystem effects: plant invasions can change hydrology

Ecosystem effects: Myrica (shrub) invasion in Hawaii alters N cycling Myrica has N-fixing bacteria in roots In low nitrogen (volcanic) areas with no native nitrogen-fixing plants, Myrica dramatically alters the N-cycle

1. Microstegium invades

2. Dense, continuous litter

layer

3. Increased fire severity and extent

4. Damage to native community

Hypothesized Microstegium –

Fire Cycle

Prescribed fire in Microstegium- invaded area

Research plan: fire intensity, effects

Prescribed fires a. Fire intensity

b. Tree/plant community responses

Big Oaks National Wildlife Refuge

Research plan: fire intensity, effects

Methods: a. Paired plots (10x25m)

invaded/uninvaded

b. Vegetation before and after

c. Experimentally planted trees

d. Temperature, flame height, area burned

Thermocouple data loggers

Experimental trees

Flame height Video

25m

10m

trees

tre

es

trees

tre

es

trees

tre

es

temp

Flame ht

Results: fire intensity

Results: tree survival and regeneration

Experimental trees: White oak (Quercus alba) Bur/black oak (Quercus macrocarp/velutina) Tulip (Liriodendron tulipifera) Maple (Acer rubrum)

Consequences of invasion

• Native plant diversity

• Forest succession

• Arthropod diversity

• Nutrient dynamics

• Decomposition

• Disease vectors

• Carbon storage

• Fire behavior

Microstegium vimineum

The stages of biological invasions

Adapted from Lockwood et al, 2007

Transport

Death

Introduction

Fail

Establish

Remain

Spread Impact

Ecosystems

Communities

Local or regional

Management/eradication

Recovery of native community

Management goals

• Eradication: Remove current invasions • Containment: Slow or stop the spread of

further invasions • Mitigation: Restore native community

diversity and ecosystem functions • Prevention: Avoid future invasions

Grass specific Post-emergent

herbicide plus

Pre-emergent herbicide

Reference

(control)

Hand-weeding

POST herbicide

POST + PRE herbicide 2m

2m

4 Treatments

Flory, S.L, Restoration Ecology, 2010 Flory, S.L and K. Clay Journal of Applied Ecology, 2009

Removal Experiment

Post-emergent: fluazifop-P-butyl (Fusilade DX)

Pre-emergent: pendimethalin (Pendulum AquaCap)

REF HW POST POST+PRE

Mic

rost

egiu

m b

iom

ass

(g)

0

10

20

30

40 2005 2006

a

b

cd

eefno

data e

Fall

Results: Efficiency of removal

REF HW POST POST+PRE

Mic

rost

egiu

m c

over

(%)

0

20

40

60

80

10020062007

a

b

c

d

e

f f f

Spring

Flory, S.L, Restoration Ecology, 2010

REF HW POST POST+PRE

Tree

see

dlin

gs (0

.25m

2 )

0.0

0.5

1.0

1.5

2.0

aab

b

a

Spring 2007

REF HW POST POST+PRECom

mun

ity d

iver

sity

(eH

' )

0

1

2

3

4

a

b

a

b

Nat

ive

biom

ass

(g)

0

10

20

30

REF HW POST POST + PRE

a

b

b b

2006

Results: Native community responses

Plot with Microstegium removed

Flory, S.L and K. Clay Journal of Applied Ecology, 2009

2006

Management: successful removal with hand weeding or post-emergent grass specific herbicide

Restoration: removal results in return of native plants, greater diversity, and increased tree regeneration

Impacts: positive response of native community suggests negative effects of invasion

Take home messages

1. Global travel and trade will continue to result in non-native plant introductions

2. Plant invasions can have significant community and ecosystem consequences

3. Understanding plant invasion dynamics will increase management efficiency and inform priorities

4. Consider goals when managing invasions: Aim to restore native communities and ecosystem functions, not just remove invasions