New publication - Multi-Level Temporal Variation of Sap Flux Densities in Oil Palm

The transformation of tropical forests to monoculture plantations such as oil palm was reported to increase profitability while leading to losses of biodiversity and ecosystem multifunctionality. Severe changes after transformation of forests to oil palm were also reported for the hydrological cycle, i.e., increased periodical water scarcity and flooding in oil palm-dominated landscapes. Previous studies hypothesized that high transpiration (plant water use) of oil palms may be facilitated by internal stem water storage mechanisms, which would explain previously observed, unusually early diurnal peaks of oil palm transpiration. Led by researchers from the University of Göttingen, a collaborative international team assessed the water use characteristics of oil palms at different horizontal and vertical positions in the plant by using three sap flux techniques. In a radial profile of the stem, sap flux densities were low at the outer margin, increased to 2.5 cm under the bark and remained relatively high to the innermost measured depth at 7.5 cm. In a vertical profile of the stem and with further sensors in leaf petioles, we found only small time lags in sap flux densities. Time lags along the flow path are often used for analyzing the contribution of water storage to transpiration. Thus, the small observed time differences in our study would leave only little room for the contribution of water storage to transpiration, leading us to reject the original hypothesis. However, water storage might still contribute to transpiration in ways that are not detected by time lag analysis, which may be explored in future studies.

Reference: Ahongshangbam, J., Hölscher, D., Hendrayanto, Röll, A. Multi-Level Temporal Variation of Sap Flux Densities in Oil Palm. Forests 16 (2025): 229. doi: https://doi.org/10.3390/f16020229