Download Hydrology Slideshow - Hō`ike o Haleakalā Curriculum

Effects of Miconia on Hydrology
(A version of this was presented by Thomas W.
Giambelluca at the 2009 International Miconia
Conference May 4-7 2009 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.
Miconia Calvescens: a
slender, fast-growing tree from
South America
Alien Trees in
Hawaiian Forests
Biologists observed that alien
trees damage rather than
support hydrological functions,
especially ground-water
recharge.
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.
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 sponge
• large leaves cycle high percentage of
rainfall out of system through
transpiration
• shallow roots create conditions for hard,
packed soil
• all of the above increases likelihood of
soil erosion
•Miconia Pilot Study in Hawai‘i
• Abundance of light under canopy
• Ground cover
• Throughfall drop size and velocity
• Root exposure as a measure of soil loss
Light abundance
Ground Cover
Thurston: Native Forest
Onomea: Miconia Stand
Throughfall:
Rainwater
that hits
trees or
other
obstructions
on its way to
the earth
Results of
Drop Size
Survey
Natural Rain
Miconia median drop
size = 3.8 mm
Very high compared
with previous
observations
Artificial Spray
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.