Soils in a Changing World

Transcription

1 Soils in a Changing World Carbon Sinks or Carbon Sources? Nancy Collins Johnson

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3 Human activities, particularly fossil fuel burning and deforestation, have upset the balance in the Earth's carbon cycle. Woods Hole Research Center,

4 Since the Industrial Revolution began in 1750, atmospheric CO 2 has increased from about 280 parts per million to about 385 parts per million. Woods Hole Research Center,

5 Human caused emissions of CO 2 are the primary driver of Earth's increasing surface temperature.

6 Of all the CO 2 humans have added to the atmosphere since the start of the Industrial Revolution, only about 40% has remained in Earth's atmosphere. Woods Hole Research Center, About half of the remaining 60% can be accounted for in Earth's ocean.

7 The rest must have been absorbed somewhere on land, but scientists cannot yet determine specifically where this is taking place or what controls the efficiency of these land sinks. Woods Hole Research Center,

8 Soil contains more than twice the amount of carbon than does the atmosphere Relatively small changes in the flow of carbon into or out of soils could be significant on a global scale shelbycountyswcd.org/photogallery/

9 Rising temperatures brought about by climate change will cause microorganisms in the world's soils to decompose organic matter more rapidly, releasing extra CO 2 and accelerating climate change

10 Nature 2005

11 Mycorrhizas are symbioses between plants and fungi Mycorrhizal fungal mycelium may be important carbon sinks

12 Arbuscular mycorrhizas form in most plant species

13 Approximately HALF of the biomass of microorganisms in agricultural and grassland soils is from AM fungi A few grams of soil often contains many kilometers of AM hyphae.

14 Grants from the National Science Foundation support studies of the impacts of CO 2 enrichment on mycorrhizas

15 Research Questions: Does CO 2 enrichment influence mycorrhizal structure & function? Can mycorrhizas be managed to increase belowground C sequestration?

16 Research Questions: Does CO 2 enrichment influence mycorrhizal structure & function? YES Can mycorrhizas be managed to increase belowground C sequestration? Maybe

17 Field studies show that mycorrhizal hyphae increased with CO 2 enrichment

18 Greenhouse studies show that plant species respond differently to mycorrhizas and CO 2 enrichment

19 ...and the mycorrhizal effects on plants differs among fungal species Glomus spp. became less beneficial at elevated CO2 Gigaspora spp. became more beneficial at elevated CO2

20 Plant community composition is significantly influenced by the INTERACTION between [CO 2 ] and mycorrhizas

21 Mycorrhizas reduce plant species richness at ambient [CO2]... but they INCREASE plant species richness at elevated [CO2]

22 We can conclude that: Plant and fungal species differ in their responses to elevated CO 2 Elevated CO 2 does not uniformly increase mycorrhizal benefits. Mycorrhizas interact with CO 2 to influence plant community composition.

23 Research Questions: Does enrichment of C and N influence mycorrhizal structure & function? YES! Can AM fungi be managed to increase belowground C sequestration?

24 Wilson et al. 2009

25 Research Questions: Does enrichment of C and N influence mycorrhizal structure & function? YES! Can AM fungi be managed to increase belowground C sequestration? Depends on... the availability of soil nutrients and the plant and fungal species

26 NASA's first spacecraft dedicated to studying atmospheric CO 2 is in final preparations for a February 23, 2009 launch from Vandenberg Air Force Base in California.

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28 Mission data will help scientists more accurately identify CO 2 sources and sinks. Policymakers and business leaders can use this information to make more informed decisions that improve the quality of life on Earth.

29 Questions?