Effects of Miconia on Hydrology (A version of this was presented by Thomas W. Giambelluca at the 2009 International Miconia Conference May Keanae, Maui, Hawai‘i)

Hydrology: The branch of science concerned with the properties of the earth's water, especially its movement in relation to land.

But until recently, no one had demonstrated exactly how alien trees affect the water cycle. Scientists from the University of Hawai‘i at Mānoa, University of South Carolina, and National University of Singapore sought to measure the hydrological effects of miconia. Alien Trees in Hawaiian Forests Miconia Calvescens: a slender, fast-growing tree from South America Biologists observed that alien trees damage rather than support hydrological functions, especially ground-water recharge.

How might invasive trees affect the water cycle? What are their possible hydrological impacts?

large leaves shade out understory plants that act as a natural spongelarge leaves shade out understory plants that act as a natural sponge large leaves cycle high percentage of rainfall out of system through transpirationlarge leaves cycle high percentage of rainfall out of system through transpiration shallow roots create conditions for hard, packed soilshallow roots create conditions for hard, packed soil all of the above increases likelihood of soil erosionall of the above increases likelihood of soil erosion

Miconia Pilot Study in Hawai‘i Miconia Pilot Study in Hawai‘i Abundance of light under canopyAbundance of light under canopy Ground coverGround cover Throughfall drop size and velocityThroughfall drop size and velocity Root exposure as a measure of soil lossRoot exposure as a measure of soil loss

Light abundance

Thurston: Native ForestOnomea: Miconia Stand Ground Cover

R R ainwater that hits trees or other obstructions on its way to the earth Throughfall:

Results of Drop Size Survey Natural Rain Artificial Spray Miconia median drop size = 3.8 mm Very high compared with previous observations Median drop size Miconia: 5.5 mm ‘ohia: 3.7 mm

Miconia Covered Area vs. an Open Area: Decreased number of raindrops impacting the soil surface Significant increases in drop size (mass), and therefore significant increases in kinetic energy (KE) and momentum Result: more erosive rainfall that has a greater effective KE to erode and transport sediment, organics and nutrients

Root exposure: an obvious sign of soil erosion.