Temporal dynamics of tree source water in sky island ecosystems with ephemeral snow pack: a case study using Pseudotsuga menziesii (Douglas Fir)
Abstract
In semiarid regions, such as the desert southwest, water is a scarce resource that demands careful attention to its movement throughout the environment for accurate accounting in regional water budgets. Ephemeral snow pack in sky island ecosystems delivers a large fraction of the water resources to communities lower in the watershed. Because the major source of loss to those water resources is evapotranspiration (ET), any change in ET in these ecosystems will have major implications downstream. Climate scientists predict more intense and less frequent precipitation events in the desert southwest, which will alter the existing soil-plant-atmosphere continuum (SPAC). Therefore, understanding how water currently moves within that continuum is imperative in preparing for these predicted changes. This study used stable isotopes (δ18O and δD) to study the SPAC that exists in the Santa Catalina Mountain Critical Zone Observatory (SCM-CZO) to determine where the dominant tree species (Pseudotsuga menziesii, a.k.a., Douglas Fir) retrieves its water from and whether that source varies with season. We hypothesize that the Douglas Fir uses shallow soil water (< 40 cm) during the summer monsoon season and deeper soil water (> 40 cm) during the snowmelt season. The findings of this work will help to better account for water losses due to ET and the movement of water throughout the environment. With a shift in the SPAC dynamics, the Douglas Fir may become increasingly water stressed effecting its ability to survive in the desert southwest which will have important consequences for water resources in this region.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.H23H1779P
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 1625 Geomorphology and weathering;
- GLOBAL CHANGE;
- 1813 Eco-hydrology;
- HYDROLOGY;
- 1824 Geomorphology: general;
- HYDROLOGY