Convenient Sampling of Xylem Sap from Adult Tree Trunks and Analysis of Its Components

Abstract

Sampling xylem sap, especially from adult tree trunks, is a major challenge. In this study, we developed a new sampling method and tested its efficacy for sampling xylem sap from deciduous Quercus serrata and evergreen Cryptomeria japonica. The water-absorbing resin was placed in cylindrical holes in the tree trunks, and the xylem sap that was collected in the resin was analyzed for 15 metals, 4 nonmetals, total sugars, and the chemical forms of nitrogen, phosphorus, and sulfur. The volume of the collected xylem sap increased with increases in the mean monthly air temperature and the monthly precipitation when it was less than ca. 200 mm. The concentrations of sap components were higher in Q. serrata than in C. japonica. In Q. serrata, the concentrations of most sap components (e.g., K) began to increase in early spring, remained high in spring–summer, decreased in late summer–early autumn, and remained low in winter. This seasonal variation was likely associated with tree phenology. Relationships between the concentrations of elements in the sap and those in the leaves and soil solution were observed. This sampling method is appropriate for characterizing weekly and monthly mean concentrations of xylem sap components.