Ozone Good up high, bad for crops down low

Transcription

1 Ozone Good up high, bad for crops down low OLLI Bradley University Lisa Ainsworth USDA ARS Global Change and Photosynthesis Research Unit Outline Ozone in the atmosphere How does ozone affect crops? How does ozone impact global food security? 1

2 Composition of the Atmosphere Composition of the Atmosphere 40 parts per billion 400 parts per million 2

3 What is ozone? Where is ozone? 3

4 Ozone good up high (in the stratosphere) 4

5 Ozone has more than doubled since the Industrial Revolution Ozone precursors can travel across the globe NOx emissions in Asia have tripled since 1990, contributing as much as 65% to modeled springtime background ozone increases in the Western United States (where NOx emissions have decreased. 5

6 Ozone is a dynamic pollutant Shanghai Ozone is a dynamic pollutant 6

7 08:00 11:00 14:00 NO NO 2 O 3 Ozone in Champaign, IL: Aug 26 29, Ozone level (ppb) :00:00 08:00:00 16:00:00 00:00:00 08:00:00 16:00:00 00:00:00 time 08:00:00 16:00:00 00:00:00 08:00:00 16:00:00 00:00:00 7

8 1 DU = 1.54 ppb (40 DU = 62 ppb) Fishman et al. (2008) BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY, 89: Is ozone a problem in the United States? 8

9 Summary Ozone is a trace gas in the atmosphere. Concentrations of ozone are dynamic and depend on precursor emissions and temperature. Changes in future concentrations will depend upon emissions. 9

10 Outline Ozone in the atmosphere How does ozone affect crops? How does ozone impact global food security? How does ozone damage plants? 10

11 Ozone damage can both be acute and chronic Acute in response to a single exposure to a high concentration (>~ ppb) Chronic in response to growth in an elevated background concentration (generally lower than ~100 ppb) Ozone damage can both be visible and invisible Visible damage to leaves speckling, chlorosis, bronzing Invisible damage decreased photosynthetic rates, increased respiration, decreased winter hardening Stipple (small dark pigmented areas) and chlorosis (yellowing due to lack of chlorophyll). Charcoal-filtered air No filter 11

12 Necrotic targets, Speckling, Early senescence Visible symptoms of ozone damage Bronzing 12

13 Ozone injury on white pine. Tip necrosis and chlorosis. O 3 Photosynthesis Senescence Leaf water status Production Leaf area 13

14 How do we know that ozone causes damage to plants, and not NOx, SO 2, hydrocarbons or other components of photochemical smog or disease? 14

15 Soybean Free Air CO 2 Enrichment: A field laboratory for study of soybean and maize responses to global environmental change Soybean response to elevated [O 3 ] Dwight 93B15 LN IA-3010 Loda HS Pana Photo by Andrew Leakey 15

16 Experimental Design Ambient Elevated CO 2 Elevated O Ring Target [O 3 ] 2 70 ppb ppb ppb 8 85 ppb ppb 12 Carl Bernacchi 40 ppb ppb ppb Effects of ozone on soybean seed yield Yield (kg ha -1 ) Harvest Index 100 Seed Weight (g) y = x R 2 = 0.89 p = y = x R 2 = 0.71 p = AOT40 (ppm h) y = x R 2 = 0.98 p < y = x R 2 = 0.91 p < y = x R 2 = 0.79 p = y = x 0.45 R 2 = 0.20 p = Total seed yield, seed weight and harvest index decreased linearly with increasing exposure to O 3. 16

17 Genetic variation in soybean response to ozone 1.1 Relative Yield Response LG Holt Cutler 71 Corsoy 79 NE3399 IA 2052 Beeson Dwight Beeson 80 A 3127 HS Pana Spencer Loda IA 3010 LN Jack Clark DSR 304 Flyer 0.6 L Average seed yield response over 5 growing seasons. Genetic and genomic approaches to understand and improve maize response to elevated [O 3 ] Hp301 M37W NC338 CML333 IL14H Oh43 Mo17 B73 MS71 C123 17

18 Elevated [O 3 ] accelerates loss of photosynthetic capacity (i.e., accelerates senescence in diverse maize lines) Ambient [O 3 ] Elevated [O 3 ] Summary of Effects of Elevated [O 3 ] on Crops Leaf photosynthesis Leaf non-structural carbohydrates Stomatal conductance Plant water status Shoot biomass and leaf area Senescence - Accelerated Seed number and yield 18

19 Outline Ozone in the atmosphere How does ozone affect crops? How does ozone impact global food security? What is Food Security? 19

20 The World Food Summit of 1996 defined food security as existing when all people at all times have access to sufficient, safe, nutritious food to maintain a healthy and active life. Food security is built on four pillars: Food availability: sufficient quantities of food available on a consistent basis. Food access: having sufficient resources to obtain appropriate foods for a nutritious diet. Food use: appropriate use based on knowledge of basic nutrition and care, as well as adequate water and sanitation Food stability: having inadequate access to food on a periodic basis (from weather, political or economic conditions) Source: World Health Organization 20

21 Estimate % Wheat Yield Loss to Ozone How much has ozone affected U.S. maize & soybean production? Time series regression of maize and soybean yield with historical T, P/PET & O 3 data USDA NASS Yield Records EPA Air Pollution data 21

22 Ozone significantly decreases soybean and maize yields, especially under sub-optimal water availability Air quality regulations in the US have been effective in reducing crop losses to ozone 22

23 Estimates of annual crop yield losses to ozone (%) 23