Matching root water uptake patterns to fine root and soil water distributions

Aims Exploring the relationships between water uptake, fine root, and soil water is essential for many fields, such as plant physiology, ecological hydrology, and water conservancy. Methods In four Populus tomentosa stands with different ages (young and mature) and stand structures (low and high stand density), we matched root water uptake patterns obtained from stable isotope techniques with fine root and soil water distributions, respectively. The effects of soil water content and meteorological factors on these matching degrees were further explored. Results Increased competition intensity within a stand would suppress the matching degree between fine root distribution and water uptake pattern ( M FR ), but have little effect on the matching degree between soil water distribution and water uptake pattern ( M SR ). Additionally, water uptake pattern was closer to soil water distribution (average M SR were 0.89) than to fine root distribution in mature stands (average M FR were 0.68), while water uptake pattern matched both fine root and soil water distribution closely in young stands (average M FR and M SR were 0.89 and 0.83). There is a relatively high positive or negative correlation between M FR and M SR in all four stands. Compared with the direct effect of soil water content, the influence of meteorological factors on matching degrees was weak. Conclusion The results indicate that the expression of water uptake function of the young stand depends on a combination of root structure and available water resources, while the water uptake function of mature stands is driven more by available water resources rather than root structure.