Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu...
-
Upload
shawn-norton -
Category
Documents
-
view
212 -
download
0
Transcript of Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu...
![Page 1: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/1.jpg)
Rhizosphere interactions under elevated CO2: Impact on soil organic carbon dynamics
Shuijin HuNorth Carolina State University
Raleigh, NC 27695Email: [email protected]
![Page 2: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/2.jpg)
Plant-Microbe Interactions
Microbial responses to climate change
Carbon & nitrogen dynamics in agroecosystems
Microbes & plant competition
Microbial diversity & ecosystem stability
An Overview of Recent and Ongoing Research Projects
![Page 3: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/3.jpg)
Air temperature has increased ca. 0.6 oC
Air temperature is predicted to increase another 2-5 oC in the
next 100 years
![Page 4: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/4.jpg)
The increasing atmospheric CO2 is correlated with the temperature rise
![Page 5: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/5.jpg)
Global warming has some major
consequences
![Page 6: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/6.jpg)
Global climate change: Atmospheric CO2 has been increasing since the Industrial Revolution
![Page 7: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/7.jpg)
One central goal of global change research is to understand:
whether and how terrestrial ecosystems can sequester more organic C.
![Page 8: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/8.jpg)
Why ecosystem C sequestration for mitigation of climate change?
1. Air CO2-C: 750 × 1015 g
2. Biomass-C: 550-650 × 1015 g
3. Soil organic C: 1500-2100 × 1015 g
Active C pools on the Earth surface:
![Page 9: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/9.jpg)
Elevated CO2 stimulates photosynthesis and net primary production – Increases short-term C inputs
Herrick & Thomas. 2001
![Page 10: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/10.jpg)
Prerequisites for long-term ecosystem C sequestration under elevated CO2
1. Plants can effectively acquire available nutrients;
2. Mechanisms exist to sustain N supply for plants;
3. Microbial decomposition is “contained”.
Plants are primarily nutrient-limited but microbes are C-limited
![Page 11: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/11.jpg)
1. Can plants acquire available nutrients more effectively under elevated CO2?
The prevailing paradigm in 1990’s was:
Microbes outcompete plants for acquiring nutrients in soil.
![Page 12: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/12.jpg)
Microbes
Elevated CO2
Plants
Available N
Organic N
C inputs
Elevated CO2 alters the plant-microbial competition in favor of plant N utilization.
Hu et al. 2001. Nature
![Page 13: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/13.jpg)
Luo et al. 2004. Bioscience
Nutrient Limitation of Ecosystem C Sequestration
![Page 14: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/14.jpg)
2. Are there mechanisms that sustain N supply for plants under elevated CO2?
Can CO2-stimulation of plant growth be sustained
over time?
To a large degree, it will depend on whether plants can acquire sufficient nutrients from the organic pool.
![Page 15: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/15.jpg)
Elevated CO2
Plants
Microbes
Available N
Organic N
C inputs
+ Elevated CO2 increased plant N acquisition from soil organic N pool.
Hu et al. 2005. Global Ch. Biol.Zak et al. 2011. Ecology Letters.Drake et al. 2011. Ecology Letters
![Page 16: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/16.jpg)
The Summary
Plants are more effective in nutrient acquisition under elevated than ambient CO2.
Next Question
How does elevated CO2 increase plant nutrient acquisition from soil?
How does elevated CO2 increase plant nutrient acquisition from soil?
Plants are more effective in nutrient acquisition under elevated than ambient CO2.
How does elevated CO2 increase plant nutrient acquisition from soil?
The Summary
Plants are more effective in nutrient acquisition under elevated than ambient CO2.
How does elevated CO2 increase plant nutrient acquisition from soil?
![Page 17: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/17.jpg)
NO3–
NO3–
NO3–
NH4+
Ca2+
K+
PO43-
Mg2+
Residues
PO43-
(15NH4)2SO4
bacteria
fungi
Elevated CO2
Hu et al. 2005, Global Change Biol.
![Page 18: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/18.jpg)
Indeed, one major finding over the last two decades is: Elevated CO2 increases soil fungi,
particularly mycorrhizal fungi.
Then the question is:
Why?
Treseder, 2004. New Phytologist
![Page 19: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/19.jpg)
1. Mycorrhizae are symbiotic associations between plant roots and fungi;
2. Over 80% of terrestrial plants form mycorrhizae with fungi;
3. Plants allocate up to 20% of photosynthates to mycorrizal fungi under ambient CO2 and up to 35-40% under elevated CO2.
Ectomycorrhzae Arbuscular Mycorrhizae
![Page 20: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/20.jpg)
AM fungi protect organic C from microbial attack
Scanning electron micrograph of a VA mycorrhizal fungus with particles of clay firmly attached (left) and VA mycorrhizal fungi binding microaggregates into a stable macroaggregate (Tisdall and Oades 1979).
![Page 21: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/21.jpg)
The current paradigm of elevated CO2 impact on soil C
Rillig et al., 1999, Nature; Treseder & Allen, 2000, New Phytol.Antoninka et al. 2009, GCB. Wilson et al. 2009. Ecol. Letters
Elevated CO2
Plant Growth
Soil Aggregation
Mycorrhizae
Extraradical Fungal Hyphae
Cell Wall Materials (Chitin)
Carbon Sequestration
GlomalinPolysaccharides
![Page 22: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/22.jpg)
Major issues related to the current paradigm
1. The current paradigm is largely based on correlative information, rather than direct evidence;
2. Emerging evidence suggests that AM fungi may increase decomposition of organic residues (Hodge et al. 2001, Nature; PNAS 2010; Tu et al. 2006, Global Change Biology).
![Page 23: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/23.jpg)
Hodge et al. 2001
![Page 24: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/24.jpg)
Can CO2-stimulation of AM fungi increase decomposition of organic matter in soil?
Five steps to assess the impact of CO2–enhancement of AM fungi on organic C
decomposition
![Page 25: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/25.jpg)
CSTR chambers
Step 1
A microcosm experiment to assess AMF-mediated organic C decomposition under different CO2 and N levels
Microcosm unit
![Page 26: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/26.jpg)
Fig. 7 Root- and hyphal-ingrowth cores
Nylon net(1.6 mm)
Nylon mesh(20 µm )
Fig. 7 Root- and hyphal-ingrowth cores
Nylon net(1.6 mm)
Nylon mesh(20 µm )
13C/15N labeled materials
Isolation of root contribution from fungal effects on organic C decomposition
![Page 27: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/27.jpg)
Step 2A microcosm experiment to examine the impact of AMF
identity on AMF-mediated organic C decomposition under different CO2 levels
AM fungal species or assemblages
A. Acaulospora morrowiae
B. Gigaspora margarita
C. Glomus clarum
D. Assemblage A: The combination of A, B and C
F. Assemblage B: Eight species from field, including A, B & C
![Page 28: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/28.jpg)
Step 3 A field experiment to determine AMF-mediated
organic C decomposition under elevated CO2
Open-top chambers used to simulate atmospheric CO2 concentrations under future climate scenarios
![Page 29: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/29.jpg)
Elevated CO2 increased mycorrhizal infection of roots and AMF biomass in soil
Fig. S3. Elevated CO2 stimulated the growth of AMF in roots of Avena fatua and wheat, and in soil
Result 1:
![Page 30: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/30.jpg)
Result 2: Higher AMF under elevated CO2 increases decomposition
Cheng et al. 2012. ScienceA: Microcosm Exp. 1; B. Microcosm Exp. 2;C. Field Exp.
![Page 31: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/31.jpg)
Why does elevated CO2 concentration increase organic C decomposition?
Our initial hypothesis was:
Elevated CO2 stimulates organic C decomposition because 1. N becomes more limiting, 2. plants under elevated CO2 need to obtain more N, and 3. plants allocate more carbohydrates to prime
decomposition through stimulating saprotrophs.
Does elevated CO2 really reduce N availability?
![Page 32: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/32.jpg)
Result 3:
Elevated CO2 reduces soil NH4+ in N-limiting soils but
increases soil NO3- in the N-rich field soil
Cheng et al. 2012. Science
A: Microcosm Exp. 1; B. Microcosm Exp. 2;C. Field Exp.
![Page 33: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/33.jpg)
These results led us to ask: 1. Why do plants not use the increased NO3
- under elevated CO2?
2. Does elevated CO2 lead to plant preference of soil NH4
+ over soil NO3- ?
![Page 34: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/34.jpg)
Bloom et al. 2010. Science
Fig. 1. Three methods for assessingnitrate absorption (Absorb) and assimilation (Assim.) in wheatand Arabidopsis plants in hydroponic solutions where the shoots were exposed to atmospheres containing 380-ppm CO2 and 21% O2, 720-ppm CO2 and 21% O2, or 380-ppm CO2 and 2% O2.
![Page 35: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/35.jpg)
Does elevated CO2 lead to plant preference of soil NH4
+ over soil NO3- ?
Step 4
A meta-analysis of elevated CO2 impact on soil N and plant N acquisition in the literature
![Page 36: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/36.jpg)
Step 4
A meta-analysis of elevated CO2 impact on soil N and plant N acquisition in the literature.
1. 38 studies that quantified the concentrations of soil NH4
+ and NO3– and/or the capacity of plant use of NH4
+ and NO3
– under eCO2;
2. These studies encompassed more than 58 species of crop, grass, and tree species.
![Page 37: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/37.jpg)
Result 4:
Elevated CO2 reduced plant NO3- uptake and
increased soil NO3- (Net effect %).
Cheng et al. 2012. Science
20
40
-20
-40
![Page 38: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/38.jpg)
Step 5
A field experiment to assess the impact of nitrification inhibition on AMF-mediated organic C decomposition under elevated CO2
X
![Page 39: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/39.jpg)
Result 5:Inhibition of nitrification offsets CO2-enhancement of
AMF-mediated organic C decomposition
Cheng et al. 2012. Science
![Page 40: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/40.jpg)
The Summary
Fig. 4. A conceptual frameworkof AMF-mediated decompositiondriven by CO2-enhancement of plant N acquisition. CO2-enhancement of AMF primes residue decomposition and ammonium (NH4
+) releaseand optimizes NH4
+ acquisition, while reducing nitrification.
Cheng et al. 2012. Science
![Page 41: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/41.jpg)
Potential Implications
1.The contribution of arbuscular mycorhizal fungi to soil C sequestration under future CO2 scenarios may have been over-estimated;
2.Increasing plant N use efficiency and reducing decomposition through effective management of soil N transformations are keys to facilitate soil C sequestration.
![Page 42: Rhizosphere interactions under elevated CO 2 : Impact on soil organic carbon dynamics Shuijin Hu North Carolina State University Raleigh, NC 27695 Email:](https://reader030.fdocuments.us/reader030/viewer/2022032605/56649e755503460f94b75c1b/html5/thumbnails/42.jpg)
Acknowledgements
Lab members (in the last 6 years): Sean Blosvies*, Xin Chen, Jared Chauncey, Lei Cheng, Mary Claire Garrison, Natalie Gross*, Anna Johnson, Marissa Lee, Lingli Liu, Karen Parker, Tomin Sa*, Qinghua Shi*, Cong Tu*, Jinping Wang*, Liang Wang, Yi Wang, Dolly Watson, Scotty Wells*, Li Zhang*, Yi Zhang*, Lishi Zhou*
Major CollaboratorsNCSU: David Shew, Chris Reberg-Horton, Julie Grossman, Frank Louws, Mike Benson,
David Bird, Mike Burton, Nancy Creamer, Marc Cubeta, Ralph Dean, Greg Hoyt, Paul Mueller, Jean Ristaino, David Ritchie, Tom Rufty, Michelle Schroeder, Wei Shi, Lane Tredway, Dolly Watson
USDA-ARS: Fitz Booker, Kent Burkey
Funding Agencies: USDA-NRI: Soil Processes, Pest Management Alternative, Managed EcosystemsUSDA-SAREUSDA_NIFA_ORGNC Center for Turfgrass Environmental Research & EducationUSDA-ARS Plant Research Unit