Abstract:
The Yellow River floodplain exhibits variation in soil depth due to bank erosion, with soil thickness decreasing in proximity to the riverbank. Water acquisition strategies of jujube (
Ziziphus jujuba Mill.) cultivated under these heterogeneous edaphic conditions remain insufficiently defined. To address this gap, a field investigation was conducted in July and August 2023 within a representative jujube orchard, trees were sampled at near (120 m), middle (240 m), and far (360 m) distances from the Yellow River. Jujube water status, soil moisture dynamics, root morphology, and leaf carbon isotope composition (δ
13C). Leaf water content remained consistently high across all distances, indicating stable plant water status. Average soil water content was lowest at the middle distance, intermediate at the far site, and highest near the riverbank. Near-bank soils with content declining at greater depths, far-distance soils with increasing water content at depth. Middle-distance soils demonstrated a complex pattern: surface dryness was followed by moisture accumulation to 80 cm, but total soil moisture declined when the layer deepened to 100 cm. Root morphological traits varied significantly with distance. Far-distance trees exhibited the most extensive root systems, root development was reduced at the middle distance and least extensive near the river. Leaf δ
13C values differed significantly with position, with middle-distance leaves exhibiting the highest δ
13C values, consistent with higher intrinsic water use efficiency. No significant difference was observed between near and far sites. Despite spatial variability in soil characteristics, jujube trees across all distances maintained a normal water state. Near-bank trees accessed subsurface water beyond the thin topsoil, while far-distance trees benefited from greater rooting volume and enhanced soil moisture retention. In contrast, middle-distance trees were constrained by both limited soil depth and insufficient hydraulic connectivity to the river, necessitating greater water use efficiency. These findings provide mechanistic insight into distance-dependent water acquisition strategies of
Z. jujuba in the Yellow River floodplain.