Stemflow is a conduit for the transport of canopy-derived dissolved organic matter (DOM) to the forest floor. This study examined the character of stemflow DOM for four tree species over four phenophases (leafless, emergence, leafed, and senescence for deciduous species and leafed-winter, emergence, leafed- spring/summer, and senescence for coniferous species) occurring in temperate forests; namely, Betula lenta L. (sweet birch), Fagus grandifolia Ehrh. (American beech), Liriodendron tulipifera L. (yellow poplar), and Pinus rigida Mill. (pitch pine). American beech exhibited the lowest average specific UV absorbance at 254 nm (SUVA₂₅₄) values, while yellow poplar displayed the highest values. SUVA₂₅₄ values were largest in senescence and smallest in emergence. The spectral slope ratio was lower for pitch pine than the deciduous tree species. Humification index (HIX) values decreased across all species during the emergence phenophase. The developed and validated stemflow-specific four-component parallel factor analysis (PARAFAC) model demonstrated the combined influence of interspecific and temporal fluctuations on the composition of humic and protein-like substances within stemflow. By separating and examining stemflow DOM independent of throughfall, our study provides fresh insights into the spatiotemporal dynamics of stemflow inputs to near-trunk soils that may inform hot spots and hot moments theories.

Stemflow 是将树冠产生的溶解有机物 (DOM) 运输到森林地面的管道。本研究考察了温带森林中四种树种在四个物候期（落叶树种的无叶、出苗、有叶和衰老，以及针叶树种的冬季有叶、出苗、春季/夏季有叶和衰老）的茎流 DOM 特征;即，Betula lenta L.（甜桦）、Fagus grandifolia Ehrh。 （美国山毛榉）、Liriodendron tulipifera L.（黄杨）和 Pinus stricta Mill。 （沥青松）。美国山毛榉在 254 nm 处表现出最低的平均比紫外吸光度 (SUVA ₂₅₄ ) 值，而黄杨则表现出最高的值。 SUVA ₂₅₄ 值在衰老时最大，在出苗时最小。油松的光谱斜率比落叶树种低。在羽化物候期，所有物种的腐殖化指数（HIX）值均下降。开发和验证的茎流特异性四组分平行因子分析（PARAFAC）模型证明了种间和时间波动对茎流内腐殖质和类蛋白质物质组成的综合影响。通过分离和检查独立于径流的茎流 DOM，我们的研究为近树干土壤的茎流输入的时空动力学提供了新的见解，这可能为热点和热点理论提供信息。