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X-WR-CALNAME:ESS Oral Defense:  Natan Holtzman "From satellites to stomata:
   Measuring and modeling vegetation responses to water stress at ecosystem
  scale"
X-WR-TIMEZONE:Pacific Time (US & Canada)
BEGIN:VEVENT
DTSTAMP:20260520T045805Z
UID:tag:localist.com\,2008:EventInstance_45280096523933
DTSTART:20240112T223000Z
DTEND:20240112T233000Z
DESCRIPTION:The response of plants to water stress (dry soil and/or dry air
 ) is a first-order control on the water and carbon cycles\, and plays a ke
 y role in wildfire\, crop productivity\, and forest mortality. \n\nPlants 
 respond most immediately to water stress by adjusting their stomatal condu
 ctance (the amounts of carbon let in\, and water let out\, through pores o
 n leaves)\; the degree of this adjustment under different conditions varie
 s greatly among different plants. While water stress response has been stu
 died extensively in individual plants\, ecosystem-scale data and models ar
 e largely missing\, limiting our ability to understand plant water stress 
 effects at large spatial scales. This dissertation helps address that gap.
  In Chapter 2\, I present the first field experiment directly testing the 
 sensitivity of microwave radiometry (a type of remote sensing) to plant wa
 ter potential in a forest. I show that vegetation optical depth derived fr
 om radiometry mirrors diurnal and seasonal changes in tree leaf water pote
 ntial. \n\nIn Chapter 3\, I use a simulation experiment to investigate how
  plant traits describing water stress response could be estimated by combi
 ning microwave radiometry with a land surface model. In this setting\, I e
 xamine various satellite orbit configurations with different time-of-day s
 ampling patterns. When simulated data from two satellites in different orb
 its is used to constrain the model\, predicted evapotranspiration during d
 rought has 40% less root mean square error than when only one satellite is
  used. Encouragingly\, using two satellites similar to those already in Su
 n-synchronous orbits yields similar accuracy to using a geostationary sate
 llite observing at all hours of the day\, which has been proposed but woul
 d be much more expensive in practice.\n\nIn Chapter 4\, I introduce a new 
 model of stomatal response to water stress in which plants maximize time-i
 ntegrated carbon gain that is discounted over a given time scale. This mod
 el is more biologically realistic than most current models in which only i
 nstantaneous carbon gain is maximized. By fitting the new model to eddy co
 variance data\, I show that an ecosystem's stomatal discounting time scale
  is empirically linked with that location's typical time interval between 
 rainfall events. Overall\, the results presented in my dissertation can he
 lp see the forest for the trees - that is\, help understand how water stre
 ss affects entire ecosystems. In the future\, this work could be extended 
 to predict vegetation responses to the increased stresses of climate chang
 e and identify hot spots of vulnerability or resilience around the world\,
  among other applications.
GEO:37.42816;-122.175935
LOCATION:Y2E2 Building\, 299
SUMMARY:ESS Oral Defense:  Natan Holtzman "From satellites to stomata:  Mea
 suring and modeling vegetation responses to water stress at ecosystem scal
 e"
URL;VALUE=URI:https://events.stanford.edu/event/ess_oral_defense_natan_holt
 zman_from_satellites_to_stomata_measuring_and_modeling_vegetation_response
 s_to_water_stress_at_ecosystem_scale
CATEGORIES:PhD Defense
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