Redwoods go wireless: discovering the links between trees and the hydrological cycle Todd Dawson Center for Stable Isotope Biogeochemistry & Department of Integrative Biology, University of California - Berkeley

Global Context: Forests cover 32% of the Earth’s surface Forests cover 32% of the Earth’s surface Forests recycle ~66% of all the fresh water on Earth each year Forests recycle ~66% of all the fresh water on Earth each year (~7,500,000 km 3 moves through trees each year) (~7,500,000 km 3 moves through trees each year) The “climate” system has long been thought to ‘drive’ this water The “climate” system has long been thought to ‘drive’ this water movement through forests movement through forests BUT... Trees and forests significantly modify the climate and micro- Trees and forests significantly modify the climate and micro- climates that are known to drive water loss climates that are known to drive water loss There is a pressing need to determine the relative importance of 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

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) California’s water resource issues  Fog, and its importance in coastal California’s 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.

Redwood Program Objectives : Elucidate the role of fog for/on: 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 California’s water limited environs Place such an understanding into the broader view of how TREES shape the hydrological cycle and in particular the hydrology of California’s water limited environs

Present-day Coast Redwood Geographical Distribution Berkeley/SF Influenced by Maritime Fog in Summer

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

But…how do you determine the role of redwood trees in the hydrological cycle when canopy heights exceed 100m and environmental variation is perhaps the greatest we’ll ever find? THINK WIRELESS!

intel wireless sensor networks Weather mote Burrow mote 2002 Weather mote Redwoods go wireless!

2003, unpublished Bottom Top 36m 34m 30m 20m 10m

What’s 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 XX YY ZZ

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

A time of tremendous biological activity Dawson, 1998 Typical Pattern of Rainfall and Fog Occurrence in Coastal California

Remove Trees and Fog inputs decline by 33 to 50% Dawson, 1998 Total = 1,845mm 465mm

WET leaves

Heat Ratio Sapflow Method (Burgess et al. 2001) Data logger, storage module & battery in tree Well-organized multiplexer & wiring set-up Probe set Solarpower

Because of its symmetric configuration, the HRM can resolve zero flows as well as reverse flows! T2T2T2T2 T1T1T1T1 Heat Ratio Method Zero sap flow Heater

Heat Ratio Method Active sap flow V = thermal diffusivity x Ln T 1 probe distance T 2 T2T2T2T2 T1T1T1T1 Heater Flow velocity (V) is logarithmically related to the ratio of temperature increases up- and down-stream from a heater Active sap flow

Low Humidity Night NighttimeTranspiration [10-40% of day]

High RH Wet leaves No transpiration Reverse flow [in daytime too] 5-7% of daily max

 13 C (‰) C i (ppm) Plant or environment?

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 Ecosystem Scale

Sapflow (m 3 x 10 3 month -1 ) FOG J F M A M J J A S O N D 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 L/day but in summer use L/day 2001

Inter-annual comparison: 2001 vs Rain fall (mm) Fog drip (mm) VPD summer (kPa) H 2 O use (L) ,700 61, ,300 73, ,450 75,210 BB SE 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)

PDO & ENSO influence SST and in turn fog formation warm cool