Eco-hydrological pathways inferred from stable isotopes in a Pinus ponderosa and Pinus monophylla woodland of the Sheep Range, southern Great Basin, USA
AuthorHoover, Kelli Jo
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The North American Monsoon System (NAMS) is highly variable bothtemporally and spatially, and variability is likely to increase with climate change. The impact of summer precipitation on ecosystem patterns and processes, particularly at high elevations in the Great Basin, is poorly understood. In order to develop better predictions of ecological responses to climate change in the southern Great Basin, I tested the hypothesis that tree xylem water during the growing season is a reflection of either groundwater or summer precipitation from the NAMS. Stable isotope ratios were used to examine seasonal plant water sources in two high-elevation tree species found in the southern Great Basin of Nevada- <italic>Pinus ponderosa</italic> and <italic>Pinus monophylla</italic>.Samples of xylem and leaf tissues from multiple trees at the site were collected and analyzed for δ<super>18</super>O and δD. Additional samples from groundwater, soil layers, and precipitation were collected and analyzed. Sampling was performed twice for the 2009 growing season, once pre-monsoon (June) and once post-monsoon (October). Results indicate that both <italic>P. ponderosa</italic> and <italic>P. monophylla</italic> rely on groundwater as their primary water source both pre- and post-monsoon. This suggests that both species at this site have adapted to variability in summer precipitation by relying primarily on groundwater sources rather than inconsistent, unreliable precipitation events. Such information is critical for determining potential ecological shifts in isolated, semi-arid, high-elevation environments in the face of future climate change.