1. Sensitivity of Biogenic Emissions to Climate Jihee Song Global Physical Climatology December 5, 2006

2. Outline Introduction Sensitivity of biogenic emissions to climatic factors Conclusion

3. Isoprene Trees are the major source of BVOCs (Biogenic Volatile Organic Compounds)  Annual global emission is ~ 1150 TgC  BVOC emission > AnthroVOC emission Isoprene  A highly reactive BVOC, accounting for 43% of total BVOC inventory*  Predominantly emitted by Oak trees * Guenther et al. (1995)

4. Why important? Isoprene * EPA: Health and Environmental Impacts of Ground-level Ozone http://www.epa.gov/air/urbanair/ozone/hlth.html Ozone * + NOx

5. Sensitivity of Biogenic Emissions to Climate* Land cover Climatic factors  Surface temperature  Light intensity  Relative humidity  CO 2 concentration * Fuentes et al. (2000); Guenther et al. (1999); Kesselmeier et al. (2002); Lerdau et al. (1997)

6. 15 20 25 30 35 40 45 50 120 100 80 60 40 20 0 Temperature Isoprene flux (nmoles m -2 s -1 ) Temperature ( o C) * Lerdau et al. (1997) White oak leaves*

7. 15 20 25 30 35 40 45 50 120 100 80 60 40 20 0 Temperature optimum Isoprene flux (nmoles m -2 s -1 ) Temperature ( o C) * Lerdau et al. (1997) White oak leaves*

8. 15 20 25 30 35 40 45 50 120 100 80 60 40 20 0 Temperature Isoprene flux (nmoles m -2 s -1 ) Temperature ( o C) * Lerdau et al. (1997) White oak leaves*

9. 15 20 25 30 35 40 45 50 120 100 80 60 40 20 0 Temperature optimum Isoprene flux (nmoles m -2 s -1 ) Temperature ( o C) * Petron et al. (2001) White oak leaves Long-term, as well as short-term effects of temperature influence isoprene emissions (up to 15 day prior to measurement*)

10. Light Intensity Light intensity (μmoles m -2 s -1 ) Isoprene flux (nmoles m -2 s -1 ) 60 40 20 0 Light intensity (μmoles m -2 s -1 ) Isoprene flux (nmoles m -2 s -1 ) * a) Lerdau et al. (1997), b) Fuentes et al. (2000) a)b) White oak leaves Saturation point

11. Light Intensity * Lerdau et al. (1997) Tropical deciduous forest leaves* Light intensity (μmoles m -2 s -1 ) Isoprene flux (nmoles m -2 s -1 )

12. Light Intensity Oak (n=5)Aspen (n=3) Sunlit30.6±6.012.1±1.7 Shade7.6±2.97.4±1.5 * Sharkey et al. (1991) Isoprene emissions (nmol m -2 s -1 )*

13. Light Intensity Oak (n=5)Aspen (n=3) Sunlit30.6±6.012.1±1.7 Shade7.6±2.97.4±1.5 Isoprene emissions (nmol m -2 s -1 )* * Lerdau and Keller (1997) Sunlit leaves are exposed to higher radiation and leaf temperature than shaded leaves located inside or at the bottom of the canopy

14. Relative Humidity Increasing with RH  Aspen leaves (Monson and Fall, 1989)  Eucalyptus leaves (Guenther et al., 1991) Decreasing with RH  Kudzu leaves (Sharkey and Loreto, 1993)  Deciduous tree leaves (Kuhn et al., 2004) * a) Guenther et al. (1991), b) Kuhn et al. (2002) b) Relative humidity (%) Normalized rate 1.2 0.9 0.6 0.3 0 10 40 70 100 a)

15. CO 2 Partial Pressure* O C O CO 2 partial pressure (Pa) 100 80 60 40 20 0 Isoprene emission (nmol m -2 s -1 ) 100 80 60 40 20 0 Isoprene emission (nmol m -2 s -1 ) 0 20 40 60 80 * Sharkey et al. (1991) a) Oak leavesb) Aspen leaves Ambient CO 2 condition (40Pa) High CO 2 condition (65Pa)

16. Conclusion A comprehensive review of research on the sensitivity of biogenic emissions to climatic conditions; temperature, light intensity, relative humidity, and CO 2 concentration

17. Conclusion Light intensity  GloBEIS (Global Biosphere Emissions and Interactions System) allows isoprene emissions to increase until the saturation point around 1000 μmol m -2 s -1. However, many studies have shown that isoprene emissions for various vegetation species continue to increase. GloBEIS’ saturation point leads to the discrepancies between modeling results and observations. Other climatic factors: RH and CO 2 concentration  Uncertainties in climatic factors arise due to the limited number of species and conditions for which emission measurements have been made. Uncertainties in the isoprene emission rates can lead to greater uncertainties in the global / regional air quality prediction of other chemical species. Light intensity Isoprene flux

18. Conclusion Results of this review demonstrate that  isoprene emissions are strongly linked to climate variables which have changed in the past and have great potential to change further in the future.  link between isoprene emissions and climate variables should be considered with vegetation species. Since isoprene and other biogenic VOC play a large role in producing ground level ozone, a better understanding of the potential changes in biogenic emissions from natural global change, as well as human-induced change, is needed.

19. References Fuentes et al. (2000); Guenther et al. (1991; 1995; 1999); Kesselmeier et al. (2002); Kuhn et al. (2004); Lerdau et al. (1997); Lerdau and Keller (1997); Monson and Fall (1989); Monson et al. (1994); Petron et al. (2001); Sharkey et al. (1991); Sharkey and Loreto (1993)