Global climate change may influence the distribution and water uptake patterns of plants in the rocky mountainous areas of North China. The change in climatic conditions with elevation in mountainous areas provides an opportunity to understand the potential impacts of global climate change on plant water use. To assess the responses and adaptations of plants to the elevations, three aspects were investigated for Platycladus orientalis (L.) Franco and Pinus tabuliformis Carrière, namely source of water used, water use efficiency (WUE), and specific leaf area (SLA). These aspects were assessed for the selected species along an elevation from 100 to 1000 m (100, 400, 700, and 1000 m) in a seasonally arid area. The results showed that the soil water contents were significantly and positively correlated with the elevation (P < 0.05). The soil water content increased by 0.33% for every 100 m increase in elevation. P. orientalis (L.) Franco was sensitive to the change in elevation and showed plasticity with regard to the water source used, while P. tabuliformis Carrière was not. P. orientalis mostly used water from the 60–100 cm soil layer (28.6–33.8%) and groundwater (27.8–36.2%) at four elevations. The water utilization ratio of P. orientalis at the 60–100 cm soil layer and groundwater decreased with elevation, while that at the 0–20 and 20–60 cm soil layers increased gradually with elevation. The water sources of P. tabuliformis exhibited no variation with elevation and growing stages. P. tabuliformis obtained over 60% of the water from the 60–100 cm soil layer (27.8%) and groundwater (35.9%), while small amounts were from the 0–20 and 20–60 cm soil layers. The SLA of P. tabuliformis and P. orientalis decreased by 0.73 and 0.70 cm2/g, respectively, for every 100 m elevation. The SLA and WUE were significantly and negatively correlated with elevation. At the same elevation range, the SLA of P. tabuliformis was 1.5% higher than that of P. orientalis, while the WUE of P. tabuliformis was 3.4% lower than that of P. orientalis. The results indicated that P. orientalis was better adapted to environmental changes than P. tabuliformis. P. orientalis can change its source of water, improve WUE, and reduce SLA to adapt to the change in elevations, showing a synergistic adaptation to elevation. However, P. tabuliformis showed trade-off adaptation to elevation by adjusting only WUE and SLA.