Using stable water isotopes and borehole NMR to inform an ecohydrological model in a subalpine and upper montane catchment in the Rocky Mountains
Abstract
Recent work using stable water isotopes has revealed that vegetation across a range of different biomes preferentially take up tightly bound soil water over more mobile pools. This so called two water worlds hypothesis (TWWH) has important implications for hydrological modeling efforts in ecosystems where it holds true, since few if any ecohydrological models incorporate this phenomenon. Further, in ecosystems where the TWWH is supported, information regarding the proportion of soil water in the bound and mobile pools is necessary to inform plant-soil water dynamics in models. In this study, we investigate which soil water pools are used by dominant vegetation in an upper montane and subalpine catchment in the Rocky Mountains of southern Wyoming, and use this information to inform the Terrestrial Regional Ecosystem Exchange Simulator (TREES). Within each catchment, we test the TWWH using stable water isotope analyses in an upland coniferous forest and an adjacent, downgradient groundwater-supported wetland. The proportion of soil water in each pool within each ecosystem was inferred from borehole nuclear magnetic resonance (NMR). These field data are being incorporated into TREES, by partitioning plant water uptake between bound and mobile pools. NMR analyses were conducted in all four ecosystems down to a depth of approximately 75 cm and revealed that while mid growing season soil water content was approximately two-fold higher in the subalpine forest versus that of the upper montane forest, the vast majority of soil water, 86% on average, existed in the bound pool in both ecosystems. Alternatively, soils in both wetlands were saturated throughout their profiles, with a majority of the soil water existing in the mobile pool, 63% on average. These initial findings highlight the importance of bound soil water pools in both upland forests, as opposed to the wetlands, which had an abundance of water in both pools.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.H54A..03M
- Keywords:
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- 1839 Hydrologic scaling;
- HYDROLOGYDE: 1847 Modeling;
- HYDROLOGYDE: 1873 Uncertainty assessment;
- HYDROLOGYDE: 1879 Watershed;
- HYDROLOGY