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M. Susana Alvarado- Barrientos , F. Holwerda , H. Asbjornsen and T. Dawson

Linking fog climatology and transpiration suppression for Mexican weeping pine in a seasonal tropical montane cloud forest. M. Susana Alvarado- Barrientos , F. Holwerda , H. Asbjornsen and T. Dawson 2012 ESA Meeting COS 189-9. Tropical Montane Cloud Forests.

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M. Susana Alvarado- Barrientos , F. Holwerda , H. Asbjornsen and T. Dawson

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  1. Linking fog climatology and transpiration suppression forMexican weeping pine in a seasonal tropical montane cloud forest M. Susana Alvarado-Barrientos, F. Holwerda, H. Asbjornsen and T. Dawson 2012 ESA Meeting COS 189-9

  2. Tropical Montane Cloud Forests Biodiversity hotspots and hydrologically unique. Net water gain: • Cloud water interception • Transpiration suppression + P (rainfall, fog, drizzle) - transpiration + water yield

  3. Climate change: lifting of cloud base • Reduced fog occurrence • Likely scenario: foggy to overcast • Deforestation of • lowland forests, • Changing sea surface • temperature Lawtonet al. 2001 Expect less transpiration suppression? How much more transpiration can we expect?

  4. Objectives + transpiration ?? • Quantify the Et suppression effect of fog • for Mexican weeping pine (Pinuspatula). • Examine implications of rising cloud base.

  5. Study area and study period 10-year old 2100 m a.s.l. Mulligan & Burke (2005) 80% Wet 2009 Dry 2010 Dry 2009 26% 26% 42%

  6. Methods: Transpiration under different weather conditions Foggy OvercastSunny

  7. Methods: Transpiration under different weather conditions • Et : Heat Ratio sap flow • Micro-meteorology: VIS, Rs, RH, P • Canopy wetness

  8. Weather conditions Foggy: VIS < 1000 m Two fog classes: Dense (≥ 60%)Light (< 60%)

  9. Weather conditions • Daily theoretical clear-sky Rs compared to measured Rs to identify “golden days” • Month-specific Rs daily courses for golden days Overcast: fog-free and cloudiness ≥ 0.7 Sunny (& partially cloudy) fog-free and cloudiness < 0.7 Excluded hours overlapping rainfall and assoc. leaf wetness

  10. Weather conditions • Daily theoretical clear-sky Rs compared to measured Rs to identify “golden days” • Month-specific Rs daily courses for golden days Overcast: fog-free and cloudiness ≥ 0.7 Sunny (& partially cloudy) fog-free and cloudiness < 0.7 Excluded hours overlapping rainfall and assoc. leaf wetness

  11. Results: Daily courses of Et • Seasonal differences, but non-sunny • conditions remain consistently low. Dry 2009 Wet 2009 Dry 2010

  12. Total daytime Et suppression relative to sunny conditions • Dense fog reduces Et the most. • More Et suppression during the dry season. 69% 75% 88%

  13. Et suppression effect of fog and overcast different? • No sig. difference between light fog and overcast

  14. How significant for total Et?Linking fog climatology 23% 19% 16% 10% 13% 13% Dry 2010 Dry 2009 Wet 2009 • Very low % of time under dense fog.

  15. How significant for total Et?Linking fog climatology • About half of all fog events were accompanied by rainfall; suppression effect of fog outweighed. 21% 10% 16% 42% 45% 9% Dry 2009 Wet 2009 Dry 2010

  16. Time of day with fog • At time of maximum transpiration, generally low fog occurrence. Dense fog (all seasons) Light fog (all seasons)

  17. Fog-induced canopy wetness • Canopy usually • remained • (partially) dry. • Et suppression was mainly through reductions in radiation and increasing air humidity.

  18. Total Et suppression due to fog relative to overcast conditions % of total seasonal Et 4% 2% 2% • If foggy conditions replaced by overcast, ~4-6% more water transpired annually.

  19. Total Et suppression due to fog relative to sunny conditions 23% % of total seasonal Et 16% 10% • If foggy conditions replaced by sunny, ~26-33% more water transpired annually…but, unlikely scenario!

  20. Conclusions • Similar Et suppression effect for foggy and overcast conditions, combined with • low amount of water “saved” from being lost to the atmosphere (via Et) due to fog, relative to overcast conditions: • Lift of cloud base may have low impact on the amount of water transpired by a young pine plantation in this seasonal TMCF • Et suppression of fog was mainly through reductions in radiation and increasing air humidity, than by canopy wetness.

  21. Thank you! Acknowledgements Funding: NSF to H.A. and T.D. – USA U. of New Hampshire and Iowa State U. – USA Institute of Ecology of Xalapa (INECOL) – Mexico CONACyT– Mexico Advising: L.A. (Sampurno) Bruijnzeel Technicians, students and local inhabitants Sergio Cruz Martínez AdánHernándezHernández AgustinaSánchezParada Lori Andrews Eric Redmond Jose Antonio López David Buock Laura Luna Maira Leonides y familia Loma Alta and Tierra Grande communities

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