Drought tolerance mechanisms and water flux effects of oil peony in Chinese Loess Plateau

The Chinese Loess Plateau (CLP) is a degraded ecosystem that has not been fully restored, characterized by perennial drought and erosion. Oil peony is an important plant that can tolerate drought and produce abundant seeds for high-quality edible oil. As a result, it will be widely planted as part of a vegetation restoration project to control soil erosion in the CLP and increase farmers' income. However, the drought-resistant mechanism and hydrological effect of oil peony remain unclear. In this study, stable hydrogen and oxygen isotopes (SHOI) testing, which is dominant in identifying potential plant water use sources, and Hydrus-1d software, which is excellent in quantifying vegetation water balance, were combined to quantify the contribution of soil water, groundwater, and precipitation to plant growth, as well as the evapotranspiration and infiltration flux of oil peony in mature and juvenile stages. The results showed that juvenile oil peonies mainly used 0–20 cm surface soil water in spring, and their water utilization rate (61.8 %) was lower than that of mature oil peonies (70.7 %). In summer and autumn, when the water content of surface soil mainly from precipitation was high, oil peony tended to absorb water from deep soil layers. The contribution rate of soil water in dry soil layers was much higher than that in water-sufficient soil layers. The modelling flux of water absorbed by peony in different soil layers was consistent with the direct tests of SHOI. Based on modelling, water loss due to evaporation from mature oil peony was smaller than that from juvenile peony, but the infiltration of water to deep soil layers in mature peony land was larger than that in juvenile peony land. We found that oil peony prefers to use water in dry soil layers, explaining its drought tolerance characteristics. The water use strategy of mature oil peony was more diverse than that of juvenile ones. This work reveals the drought tolerance strategy of oil peony and its hydrological effects in promoting more water conservation in the soil. • Contribution rate of soil water to oil peony is negatively related to soil water content. • Mature oil peony tends to absorb the water of the deep soil layers. • Oil peony tends to absorb water in relatively dry soil layers. • Planting oil peony can promote water infiltration by simulation of Hydrus-1d. • Planting oil peony can better inhibit surface evaporation.