Monitoring dryland riparian vegetation water use and stress via ECOSTRESS
Abstract
Throughout semi-arid ecosystems worldwide, changes in water availability driven by climate and land-use threaten the extent and health of riparian woodlands. In the southwestern US, streamflow diversions and abstraction of groundwater imperil dominant riparian trees such as cottonwoods (Populus spp.) and willows (Salix spp.) which rely on soil moisture and shallow groundwater. Yet, while it is well known that reduced water availability negatively affects riparian trees, there are large uncertainties about the water requirements of and use (i.e. evapotranspiration) by healthy riparian trees at stand-level and landscape scales. Riparian plant-water relations depend not only on internal biophysical needs, but also external factors such as atmospheric dryness, quantified by meteorological variables such as vapor pressure deficit (VPD).
Here we test the applicability of a paradigm for monitoring plant water-use and stress developed at leaf scales - namely, evapotranspiration (ET)—vapor pressure deficit (VPD) relations - at landscape scales for assessing riparian vegetation water-use and stress in the San Pedro River corridor in SE Arizona. We test the hypothesis that diurnal ET patterns and ET-VPD variability in riparian vegetation communities is dependent on water availability (measured by streamflow). Key to this study is a new evapotranspiration data product based on thermal imagery from the international space station (ISS)-mounted ECOSTRESS sensor. ECOSTRESS provides data at novel diurnal timescales that enables study of how ET varies with VPD at local meteorological sensors from pre-dawn through mid-day, across hundreds of square kilometers of riparian and surrounding vegetation. We find that higher midday ET and larger differences in midday-predawn ET metrics differentiate riparian communities between sites with perennial flow from those with intermittent flow. We developed a new landscape-scale, multi-temporal quantification of riparian vegetation water use dynamics, and show that diurnal ET-VPD metrics may be useful for identifying water stress for riparian vegetation communities across semi-arid ecosystems, which may inform land and water management.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGC51E1108M
- Keywords:
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- 1632 Land cover change;
- GLOBAL CHANGE;
- 1640 Remote sensing;
- GLOBAL CHANGE;
- 4333 Disaster risk analysis and assessment;
- NATURAL HAZARDS;
- 4217 Coastal processes;
- OCEANOGRAPHY: GENERAL