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The effects of groundwater availability on Kiawe (Prosopis pallida) physiology and growth Bruce Dudley, Flint Hughes, Rebecca Ostertag, Susan Cordell.

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Presentation on theme: "The effects of groundwater availability on Kiawe (Prosopis pallida) physiology and growth Bruce Dudley, Flint Hughes, Rebecca Ostertag, Susan Cordell."— Presentation transcript:

1 The effects of groundwater availability on Kiawe (Prosopis pallida) physiology and growth Bruce Dudley, Flint Hughes, Rebecca Ostertag, Susan Cordell

2 Kiawe history in Hawaii Introduced in 1828 Spread and planted throughout leeward Hawaii during the 19 th century Farmed as cattle feed By 1900 Kiawe was the dominant lowland tree species on western coasts Currently covers 58,766 ha (3.55% of the total land area of the Hawaiian islands)

3 Potential negative effects Reduction in regional groundwater levels Reduction in habitat for native species (by shading) Reduction in anchialine pond habitat and water quality

4 Potentially increases water and nutrient availability in surface soils Prosopis seed pods can be made into beer Potential positive effects

5 Research questions 1.What proportion of water used by kiawe comes from deep (aquifer) and shallow (rainfall events) sources? 2.How does water availability alter kiawe growth and productivity? 3.How does water availability alter kiawe N inputs to soil and groundwater

6 Deep groundwater includes high altitude rainfall - Isotopically lighter Sea δ 18 O = zero δ 18 O = -X‰ δ 18 O = - -X‰ δ 18 O = - - -X‰ δ 18 O = X‰ Lighter… Surface water - Isotopically heavier

7 Upland Lowland Kiholo Bay Upland Lowland

8 Water sources – December 2010 Upland rain -7.73‰ Lowland rain -7.77‰ Aquifer -7.16‰ Summer rain / shallow soil water (From Cordell and Sanquist 2008) ~ +1.5 to -1‰

9 Water potential This will tend to decrease with water availability

10 Photosynthetic efficiency Pre-dawn (PD) yield in healthy plants typically around.83 (83%) This will tend to decrease in (water-) stressed plants

11 Leaf chemistry

12 Soil Chemistry

13 Work still to do… Continue water availability and plant physiology measurements at 3 month intervals for 21 further months. Assess N inputs and losses from upland and lowland soils


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