Redwoods go wireless: discovering the links between trees and the hydrological cycle

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Redwoods go wirelessdiscovering the links
between treesand the hydrological cycle

• Todd DawsonCenter for Stable Isotope
  Biogeochemistry
• Department of Integrative Biology, University of
  California - Berkeley

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Global Context
Forests cover 32 of the Earths surface
Forests recycle 66 of all the fresh water on
Earth each year (7,500,000 km3 moves through
trees each year) The climate system has long
been thought to drive this water movement
through forests
BUT . . . Trees and forests significantly
modify the climate and micro- climates that are
known to drive water loss There is a pressing
need to determine the relative importance
of biological physical drivers of the
hydrological cycle via, Precise
characterizations of the biological activities of
trees Precise characterizations of the
environmental drivers
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Local Context

• Coast redwood occupy a unique hydrological zone
  near the land-sea interface are characterized by
• Maritime Fog
• What is unknown is its importance for
• (a) redwood tree ecology and physiology,
• (b) the water balance of redwood forests,
• (c) Californias water resource issues
• Fog, and its importance in coastal Californias
  hydrology is unknown, yet could be central to
  understanding what links ocean and land systems
  and impacts coastal ecology.
• In other coastal zones (Chile, W. Africa) fog is
  part of water resource management and
  conservation issues.

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Redwood Program Objectives

• Elucidate the role of fog for/on
• - The ecophysiology of redwood trees
• - The functioning of redwood forests with a
  focus on marine subsides of water
• Place such an understanding into the broader view
  of how TREES shape the hydrological cycle and in
  particular the hydrology of Californias water
  limited environs

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Present-day Coast Redwood Geographical
Distribution
Berkeley/SF
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PAST APPROACH Deployment of gear is done by us
(read Homo sapiens) Sensors are all wired
and therefore can only sample a very small
fraction of what we need to sample
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Buthow do you determine the role of redwood
trees in the hydrological cycle when canopy
heights exceed 100m and environmental variation
is perhaps the greatest well ever find?
THINK WIRELESS!
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intel wireless sensor networks
2002 Weather mote
Redwoods go wireless!
Weather mote
Burrow mote
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10m
20m
34m
30m
36m
2003, unpublished
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Whats next?

• Gather data in 3-D - play the movie
• Render data and place trees into context
• Model the plant-environment system
• Compare to other systems

Z
Y
X
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Now MATCH with other Field Methods

• TREE-SCALE Sap flow sensors (heat ratio method)
  placed in the lower stem, upper stem (50 m) and
  upper branches of a 60-110 m redwood tree in
  coastal California
• Ecosystem methods that permit us to characterize
  site water balance

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Typical Pattern of Rainfall and Fog Occurrence in
Coastal California
Dawson, 1998
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Total 1,845mm
Dawson, 1998
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Heat Ratio SapflowMethod (Burgess et al. 2001)
Probe set
Solar power
Well-organized multiplexer wiring set-up
Data logger, storage module battery in tree
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Heat Ratio Method
Because of its symmetric configuration, the HRM
can resolve zero flows as well as reverse flows!
?
Zero sap flow
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Heat Ratio Method
Flow velocity (V) is logarithmically related to
the ratio of temperature increases up- and
down-stream from a heater
Active sap flow
V thermal diffusivity x Ln T1
probe distance T2
Active sap flow
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d13C ()
Ci (ppm)
Plant or environment?
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Ecosystem Scale
How do oceanic subsidies of water shape stand
water use? Can we use natural gradients to help
us obtain comparative data? Can we elucidate the
importance of various controls the donor, the
plant, the microbes?
From Gilliam 1962
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For 2001 Big Basin trees use more water than do
trees in Sonoma (drier nights?) Interior trees
use more than edge trees (unless its very foggy
Aug Sept) Trees in winter use 30-75 L/day but
in summer use 175-350 L/day
2001
FOG
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Sapflow (m3 x 103 month-1)
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4
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J F M A M J J A S
O N D
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Inter-annual comparison 2001 vs. 2002
Rain fall (mm) Fog drip (mm) VPDsummer (kPa)
H2O use (L)
1285 1340 355 240 1.9-3.3 2.2-3.1 70,700 61,350
1390 1455 440 415 1.2-2.6 1.3-2.8 57,300 73,140
1390 1455 370 350 1.1-2.4 0.9-2.6 64,450 75,210
2001 2002
BB
2001 2002
SE
2001 2002
SI

• Tree water use and stand water balance is a
  function of
• Fog inputs and evaporative demand for summer
  water
• (supply vs. demand)
• Water stress in summer
• (influences both supply and demand)

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warm
cool
PDO ENSO influence SST and in turn fog formation