This work highlights the role of plants in governing soil water variation and demonstrates that they can also strongly influence the isotope ratios of soil water. In this ecosystem, the soil water content was higher than that at the neighbouring Grass site, and thus, 25% more water was available for transpiration by Q. We also found some support for H isotope discrimination effects during water uptake by Q. gambelii in these soils relative to the grass‐dominated site. gambelii, perhaps due in part to hydraulic redistribution of deep soil water or groundwater by Q. We found that soil water content and isotopic variability were damped under Q. We document patterns of depth‐ and time‐explicit variation in soil water isotopic conditions at these sites and consider mechanisms for the observed heterogeneity. We found that sites spaced only 20 m apart had profoundly different soil water isotopic and volumetric conditions. Using in situ soil water vapour probe techniques, combined with conventional soil and plant water vacuum distillation extraction, we monitored the hydrogen and oxygen stable isotopic composition of soil and plant waters at paired sites dominated by grasses and Gambel's oak (Quercus gambelii) within a semiarid montane ecosystem over the course of a growing season. ![]() New advances are being driven by measurement approaches allowing sampling with high density in both space and time. Our findings enhance our understanding of water‐root interaction in deep soil and reveal the unintended consequences of critical zone dewatering during the lifespan of apple trees.read more read lessĪbstract: Spatio‐temporal heterogeneity in soil water content is recognized as a common phenomenon, but heterogeneity in the hydrogen and oxygen isotope composition of soil water, which can reveal processes of water cycling within soils, has not been well studied. The one‐way root water mining may have changed the fine root profile from an exponential pattern in the 8‐year‐old orchard to a relative uniform distribution in older orchards. The deficits are not replenished during the life‐span of the orchard, showing a one‐way mining of the critical zone water. Measured root deepening rate was far great than the reported pore water velocity, which demonstrated that trees are mining resident old water. ![]() Soil water deficit in deep soil increased with tree age and was 1,530 ± 43 mm for a stand age of 22 years. Apple trees rooted progressively deeper for water with increasing stand age and reached 23.2 ± 0.8 m for the 22‐year‐old trees. ![]() To clarify the interaction between water use and root development in deep soil, we investigated soil water and root profiles beyond maximum rooting depth in five apple orchards planted on farmland with stand ages of 8, 11, 15, 18, and 22 years in a subhumid region on the Chinese Loess Plateau. However, the links between root development and water usage in the deep critical zone remains poorly understood. Abstract: There have been significant recent advances in understanding the ecohydrology of deep soil.
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