Presidential address at the BSA festival Hull 2018 Why plants haven’t conquered the land: Facing up to Climate Change Ever since plants left the nutrient soup of the sea, they have evolved a series of adaptations to help overcome the harsh conditions of the terrestrial environment. It’s dry, nutrients are scarce and CO2 is difficult to obtain. Plants have never managed to fully solve the need to need prevent too much water loss but at the same time to take up CO2 for photosynthesis that is essential for nearly all life on earth. The leaf stomatal pores are the key gatekeepers and mediate this photosynthesis – transpiration compromise. Evolution fits organisms to their environment but the environment is changing. What will be the impact of on plants as climate change rapidly elevates CO2? Will the balance shift from CO2 acquisition to saving water? Will plant use the extra resource to become more susceptible to pests, or will pest find them more palatable? There are many models of how plants respond to elevated CO2 and the other aspect of climate change but these are only as good as the data. There is lots of research aiming get this data but this often focusses on crop plants. Forests are a crop as a natural resource and an ecosystem that provides many benefits to humans. We need to understand how tree as long lived and sophisticated organisms will react to elevated CO2. To find out what will really happen we have to do this work outside in the real world. For a forest, this is not trivial. The FACE (Free Air Carbon Enrichment) experiment that the University of Birmingham Institute of Forest Research (BifoR) has set up is helping to find the answers. CO2 is fumigated into patches of forest over the next a decade and the reaction of the oak woodland ecosystem examined, from the soil root interface to the leaves 50 m up in the canopy. The experiment is already producing huge quantities of data that address how water and carbon cycle through the system. This data is becoming publicly available as data is streamed live over the internet. We are developing resources that teachers will find useful in school and for citizen science.

1. Why Plants Haven’t (quite)
Conquered the Land
Professor Jeremy Pritchard
@DrJPritchard

2. Outline
• Photosynthesis
• Evolution
• Climate change; CO2
• FACE
Why do trees have rings?

4. CO2 - light - Sugar

7. CO2
Sugar
O2
Rubisco

8. 4 x 1013g Rubisco on the planet

9. Land plants evolved from an algal ancestor that
lived in water.

12. Early land:
A harsh environment

19. Transpiration - photosynthesis compromise

20. Minutes Millennia

21. Stomata close at night Stomatal density
decreases under
elevated CO2
Stomatal density has
decreased over
climate change
Hours Weeks Centuries

23. CO2
Sugar

26. http://www.esrl.noaa.gov/g
md/ccgg/trends/history.html

28. CO2 can be good for plants

29. CO2 can be good for plants

31. Positive effect of CO2 only seen under fertilisation
Growth

34. CO2
Carbon
Soil?
Growth?
Stomata?
Defence?
Reproduction?
Ecology?

41. http://phenocam.sr.unh.edu/webcam/sites/millhaft/

43. Transpiration - photosynthesis compromise

47. H2O

49. Water columns can snap

50. Water columns can snap

51. Cavitation is water boiling – Temperature AND pressure

52. • Cavitation makes a click
• Clicks can be heard with
a microphone

53. Cavitation greater when transpiration is high

54. Transport efficiency vs cavitation resistance

56. Tree rings are a consequence of
• CO2 fixation
• transport efficiency vs cavitation resistance

57. Root pressure can flush out cavitation

59. Professor Jeremy Pritchard
@DrJPritchard
• Plants have breathable waterproofs
• More CO2 doesn’t always mean better plants
• Water transport is tricky
• FACE gives us new data to predict climate change

60. Mosses Bryophytes
Thank you….