Environmental Controls on Foliar Respiration in Arctic Plants ! - - PowerPoint PPT Presentation

Mary Heskel!

!

Dissertation Defense 4.26.13!

Environmental Controls on Foliar Respiration in Arctic Plants
 !

Foliar respiration and the terrestrial carbon cycle!

Trumbore 2006!

• Foliar respiratory release ≈

1/2 photosynthetic uptake

(Poorter et al. 1990; Atkin et al. 2007) ! !

• Provides energy and C

skeletons in all tissues at all times!

!

• Promotes efficient

photosynthesis (Kromer 1995;

Hoefnagel et al. 1998) !

• Global foliar respiratory CO2

release >> fossil fuel emissions (Canadell et al. 2007) ! Photosynthesis (A)!

! ! ! !!!!!!!! ! Photorespiration! ! !

! !

Respiration (R)!

CO2!

Environmental controls on respiration!

Photosynthe*c!uptake! Respiratory!release!

Environmentally sensitive !

• Temperature*!
• Nutrient availability!
• Seasonality and

phenology!

• Canopy position!
• LIGHT!

Currently no mechanistic model for foliar R. !

!

Models based on temperature, N, % of photosynthetic C gain, or multiple processes. !

• Arctic soils and vegetation store ~1/3 global

terrestrial carbon (Gorham 1991; Ping et al. 2008; Tarnocai et al.

2009)!

!

• Arctic warming ~ 2x faster than global average

(Chapin et al. 2005)!

!

• Multiple ecological consequences!
• Increased shrub cover and canopy height!
• Earlier snowmelt!
• Increased N+P availability!

Respiration in arctic plants!

• Few prior measurements (McNulty et
• al. 1988; Bliss and Dawson 1993; Atkin and Cummins

1994; Collier 1996; Collier and Cummins 1996; Arnone and Korner 1997; Shaver 1998; Muraoka et al. 2008)! !

• Fewer comparing rates across

environmental variation (Atkin and

Cummins 1994; Shaver et al. 1998; Arnone and Korner 1997) !

!

• Ecosystem measurements do

not capture foliar fluxes!

No existing quantification of foliar CO2 release in the light. !

!

! !Only ecologically relevant measure in Arctic ecosystems!

! !Also environmentally sensitive !

Arctic carbon budget under change! A "" " R" ""

"""""""""Plant" """Soil/!!! !!!!! !!!!!!!!!Heterotroph!!

Controls on respiration !

Environmental! Cellular processes!

Biotic!

(Species/ phenology)!

Chapter 3! Foliar and cellular carbon cycling responses to a nitrogen and phosphorus gradient!

Mary A. Heskel, O. Roger Anderson, Owen K. Atkin, Matthew H. Turnbull, and Kevin L. Griffin*!

*Heskel et al. 2012 American Journal of Botany!

• Aboveground NPP controlled by N+P in tundra (Bret-Harte

et al. 2004; Mack et al. 2004, Chapin et al. 1995)!

!

• Soil N+P limitation expected to relax with warming

and shrub cover (Shaver and Chapin 1986; Hobbie et al. 2002; Weintraub &

Schimel 2005; Nadelhoffer et al. 1991)!

!

• Few multi-level studies (Baddeley et al. 1994; Arens et al. 2008)!

!

• Physiological response is poorly characterized!

!

• Decoupled photosynthetic and respiratory responses !

less C gain under high N+P!

!

• Cross-taxa decrease of inhibition of R by light!

!

• Species specific organelle response!

10 20 30 40 1 2 3

% Inhibition Leaf N concentration (%)

! R

2 = 0.999

" R

2 = 0.674

10 20 30 40 0.25 0.5 0.75 1

Leaf P concentration (%)

! R

2 = 0.695

" R

2 = 0.104

Chapter 4!

Differential physiological responses to environmental change promote woody shrub expansion!

Mary Heskel, Heather Greaves, Ari Kornfeld, Laura Gough, Owen K. Atkin, Matthew H. Turnbull, Gaius Shaver, and Kevin L. Griffin*!

*Heskel et al. Ecology and Evolution, In press.!

Can foliar physiology explain woody shrub dominance under warming and fertilization? !

!

!

0.25 0.5 0.75 1 CT GH NP GHNP Relative species cover A GH NP GHNP

• 100

100 200 300 % Change in species cover B

2 4 6 8

Carbon gain efficency

CT a a a GH a a b NP a a a 2 4 6 8 GHNP a a a

• Physiological advantage ! dominance of
• B. nana under long-term warming, but not

under fertilization!

!

• Increased N+P availability may not

translate into higher C assimilation per leaf!

– Morphological response ! resources allocated to growth (Bret-Harte et al. 2001, 2002)!

Can foliar physiology explain woody shrub dominance under warming and fertilization? !

!

!

Chapter 5! Seasonality of foliar respiration: response to long-term warming and short-term temperature variability !

Mary A. Heskel, Owen K. Atkin, Matthew H. Turnbull, and Kevin L. Griffin*!

*Heskel et al. Functional Ecology, In review.!

Respiration! Rlight: Rdark !

Leaf9out ! !!Mid9Season !!!!!!!!!!Senescence! GROWING!SEASION !!

! Betula CT

! Betula WG

! Eriophorum CT " Eriophorum WG

0.2 0.4 0.6 0.8 1 160 170 180 190 200 210 Rlight / Rdark Julian Day

5 10 15 A

max (µmol CO

2 m

• 2 s
• 1)

Betula A 5 10 15 Eriophorum B C D 2 4 6 160 170 180 190 200 R

light (µmol CO

2 m

• 2 s
• 1)

E Julian Day 1 2 3 4 Julian Day F 160 170 180 190 200 210

• Stronger seasonal and thermal response in respiration

than photosynthesis!

• Inhibition of R varies within growing season!
• No clear short-term thermal acclimation of R!

– High intra-seasonal temperature variability!

Chapter 6! Examining intra-canopy carbon cycling patterns in an Arctic shrub community !

Mary A. Heskel, Matthew H. Turnbull, and Kevin L. Griffin*!

Myers-Smith et al. 2011!

• Shrub canopy height

increase (Walker et al. 2006;

Elmendorf et al. 2012)!

!

• Can influence climate

(Loranty et al. 2012; Bonfils et al. 2012! !

• Increased complexity, and

intra-canopy variation not yet addressed!

*Heskel et al. Physiologia Plantarum, In review.!

1 2 3 80 100 120 140 160 180 SLA (cm

2 g

• 1)

2011 1 2 3 80 100 120 140 160 180 200 Leaf Area Index (m

2 m

• 2)

SLA (cm

2 g

• 1)

2010 1 2 3 1 1.5 2 2.5 3 N (g m

• 2)

2011 1 2 3 1 1.5 2 2.5 3 N (g m

• 2)

Leaf Area Index (m

2 m

• 2)

2010

• Significant leaf trait

response…!

!

• No significant variation

in gas exchange !

No clear indication of canopy optimization !

Chapter 7!

Bringing the Kok effect to light:! Integrating daytime respiration and net ecosystem exchange!

Mary A. Heskel, Matthew H. Turnbull, and Kevin L. Griffin*!

*Heskel et al. Ecosphere, In review.!

RL! RD!

Leaf ! ! ! ! ! ! ! ! Ecosystem !

• Details light inhibition of respiration at leaf level!
• Reviews incorporation in eddy co-variance studies;

suggests potential 13C/12C ecosystem application!

2 4 6 8 10 2 4 6 8 10 R

Light

R

Dark

Mean R

Light/R Dark = 0.62

R

2 = 0.82

• ~ 37% average inhibition!
• Decreases with energy

demand !

• N, P, early season growth!
• Possible increase with warmth?!

Arctic carbon budget under change!

Species / Community!

!

• Shrubs may have

greater physiological adaptive ability! !

Ecosystem!

!

• Overestimate GPP!
• C cycle under change? !

Environmental! Cellular processes!

Biotic!

(Species/ phenology)!

Controls on respiration !

• Shrub > non-

shrub species!

!

• Higher in early

season!

!

! Organelle size + density!

!

Energy demand for growth!

!

Light inhibition varies with energy demand! ! Thermal acclimation*!

!

N+P response*!

!

Duration effects!

Future applications of research!

• Landscape description!
• Shrub / non shrub cover!
• Approximate N availability!
• LAI!
• Ambient temperature/light!

! !

• Respiration*!
• Degree of inhibition!
• Temperature response!
• Seasonal timing!

*Stems, roots, and soil! Modeling Arctic C exchange! Scaling up to Ecosystem!

• Stable isotope ratios of C !

!

• Ecosystem chamber CO2

fluxes!

!

• Eddy covariance corrections!

Other ecological changes!

• Fire / Drought!

!

• Latitudinal transects!

!

• Space for time !

thermokarsts!

Acknowledgements! !

Advisors: Kevin Griffin, Hilary Callahan! Committee: Shahid Naeem, O. Roger Anderson, Matthew H. Turnbull!

! Griffin Lab " Callahan Lab !

Owen K. Atkin (ANU)" Heather Greaves (Idaho) " Ari Kornfeld (Carnegie)

E3B Department " Lourdes, Maria, Chiconia, Amy ! EDC at Toolik Field Station " Arctic LTER! Gus Shaver & Ed Rastetter (MBL)!

• Quantification of ecologically relevant

measures of foliar respiration (RLight) ! !

• Response of foliar C fluxes to warming-

mediated environmental variation !

Myers9Smith!et!al.!2011!

Shrub expansion feedback network!