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3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes
• Increasing atmospheric CO2
400
Atmospheric [CO2] (ppmv)
Mauna Loa
380
360
340
320
Keeling & Whorf (2004) CDIAC
300
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes
• Increasing atmospheric CO2
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes
• Increasing atmospheric CO2 has 2 direct effects on plants:
Increases photosynthesis → more C for growth
Photosynthesis:
6CO2 + 6H2O + light 
C6H1206 + 6O2 + energy
CO2
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes
• Increasing atmospheric CO2 has 2 direct effects on plants:
Increases photosynthesis → more C for growth
Closes leaf stomates → uses less water
Photosynthesis:
6CO2 + 6H2O + light 
C6H1206 + 6O2 + energy
CO2 H2O
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes
• Increasing atmospheric CO2 has 2 direct effects on plants:
Increases photosynthesis → more C for growth
Closes leaf stomates → uses less water
• Not all species react the same:
C3 plants – responsive to CO2; high stomatal opening
Photosynthesis:
6CO2 + 6H2O + light 
C6H1206 + 6O2 + energy
CO2 H2O
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes
• Increasing atmospheric CO2 has 2 direct effects on plants:
Increases photosynthesis → more C for growth
Closes leaf stomates → uses less water
• Not all species react the same:
C3 plants – responsive to CO2; high stomatal opening
C4 plants – CO2 concentrating mechanism; small stomatal opening
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes
• Increasing atmospheric CO2 has 2 direct effects on plants:
Increases photosynthesis → more C for growth
Closes leaf stomates → uses less water
• Not all species react the same
C3 plants – responsive to CO2; high stomatal opening
C4 plants – CO2 concentrating mechanism; small stomatal opening
CAM plants – CO2 fixed at night & stored; stomata open at night
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes
• Increasing atmospheric CO2 has 2 direct effects on plants:
Increases photosynthesis → more C for growth
Closes leaf stomates → uses less water
• Not all species react the same
C3 plants – responsive to CO2; high stomatal opening
C4 plants – CO2 concentrating mechanism; small stomatal opening
CAM plants – CO2 fixed at night & stored; stomata open at night
Photosynthesis:
6CO2 + 6H2O + light 
C6H1206 + 6O2 + energy
CO2 H2O
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes – Increasing atmospheric CO2
From Dukes in Mooney & Hobbs (2000) – Table 5.1: Stimulation of
growth for invasive species by elevated atmospheric CO2
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes – Increasing
atmospheric CO2
From Belote et al. (2003) New Phytologist
161:827-835 – Oak Ridge Free Air
CO2 Enrichment (FACE) experiment in
sweet gum forest
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes – Increasing
atmospheric CO2
From Belote et al. (2003) New Phytologist
161:827-835 – C4 invasive annual
grass & C3 invasive woody vine in
sweet gum forest
2001 = wet year
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes – Increasing
atmospheric CO2
From Belote et al. (2003) New Phytologist
161:827-835 – C4 invasive annual
grass & C3 invasive woody vine in
sweet gum forest
2001 = wet year
<
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes – Increasing
atmospheric CO2
From Belote et al. (2003) New Phytologist
161:827-835 – C4 invasive annual
grass & C3 invasive woody vine in
sweet gum forest
2001 = wet year
>
<
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes – Increasing
atmospheric CO2
From Belote et al. (2003) New Phytologist
161:827-835 – C4 invasive annual
grass & C3 invasive woody vine in
sweet gum forest

>
<
2001 = wet year
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes – Increasing
atmospheric CO2
From Belote et al. (2003) New Phytologist
161:827-835 – C4 invasive annual
grass & C3 invasive woody vine in
sweet gum forest

2001 = wet year
>
<
2002 = dry year
<
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes – Increasing
atmospheric CO2
From Belote et al. (2003) New Phytologist
161:827-835 – C4 invasive annual
grass & C3 invasive woody vine in
sweet gum forest

2001 = wet year
>
<
2002 = dry year

<
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes – Increasing
atmospheric CO2
From Belote et al. (2003) New Phytologist
161:827-835 – C4 invasive annual
grass & C3 invasive woody vine in
sweet gum forest

2001 = wet year
>
<
2002 = dry year
<

<
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes – Increasing atmospheric CO2
From Smith et al. (2000): Nevada Desert FACE Facility
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes – Increasing atmospheric CO2
From Smith et al. (2000): Red brome (Bromus madritensis ssp. rubens)
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes – Increasing atmospheric
CO2
From Dukes in Mooney & Hobbs (2000) –
Fig. 5.1: Stimulation of growth by
elevated CO2 for invasives vs.
noninvasives
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes
• Increasing atmospheric CO2
Evidence in some specific cases
But not all invasives benefit
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes
• Increasing atmospheric CO2
• Global warming
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes
• Increasing atmospheric CO2
• Global warming
• Increasing N deposition
3) What makes a species invasive?
b) Environmental <Global> Change Hypothesis
Global Changes
• Increasing atmospheric CO2
• Global warming
• Increasing N deposition
SUMMARY: Global Changes
• General response is similar to that observed for elevated CO2
Evidence in some specific cases
But not all invasives benefit