Examining the linkages between forest water use, hydrology, and climate using dual-isotope approaches: insights and challenges in headwater catchments (Invited)
Abstract
The amount of biologically available water is arguably the central driver in plant processes. While many studies have examined the hydrological components of biologically available water, the role that vegetation water use plays within the forested ecosystem water balance is poorly understood. Fundamental questions of forests' effect on the hydrologic cycle remain unanswered. Stable isotope observations play an important role in studies that explore the interface between plant physiological function and watershed flowpaths, flow sources, and residence times. We use multiple approaches, including stable isotopes to mechanistically assess the inter-relationships between vegetation water use, hydrology, and climate. We measured deuterium and 18O of xylem water and soil water to track changes in the depth of transpiration source water throughout the summers in a headwater catchment in western Oregon. Additionally, we measured transpiration, soil moisture, and foliar pre-dawn water potential. Forest transpiration and soil evaporation are often not separately measured, and yet respond to environmental drivers in fundamentally different ways. A promising approach for partitioning the evapotranspiration into its component fluxes involves measurement of the stable isotope composition (2H and 18O) of water vapor exchanged between vegetation and atmosphere. We present some preliminary data examining changes in ET partitioning in response to bark beetles outbreaks in the Rocky Mountains. Last, to examine the linkages between vegetation function and micro-climate, we applied a dual isotope (13C and 18O) approach to infer physiological response of trees to changing environmental conditions. We found that stable isotopes of oxygen were directly related to stomatal conductance and inversely related to relative humidity; however, the relationship with relative humidity was more apparent. The correlation of stable isotopes in tree rings with environmental variables can be particularly useful for assessing the impacts of environmental change on vegetation over short time series. This work represents one step forward in elucidating the linkages between vegetation processes, hydrology, and climate.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.H54B..01B
- Keywords:
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- 0454 BIOGEOSCIENCES / Isotopic composition and chemistry;
- 1813 HYDROLOGY / Eco-hydrology;
- 1818 HYDROLOGY / Evapotranspiration;
- 1843 HYDROLOGY / Land/atmosphere interactions