Throughfall and stemflow serve as two important transport mechanisms for water and solutes in urban forests, though these fluxes are seldom quantified within cities. This study is the first to utilize two flux-based enrichment ratios for stemflow to characterize spatial patterns in water and solute distribution in urban forest fragments. Using event-based, in situ sampling, this study quantified stemflow enrichment for Quercus rubra (northern red oak) and Quercus alba (white oak) trees relative to open precipitation (E_P,B) and throughfall (E_T,B) per unit trunk basal area for dissolved Ca, K, Mg, Mn, NO₃-N, and S. The study investigated variability in nutrient enrichment at the fragment, municipal, and regional scales. Among all solutes, observations for E_P,B and E_T,B for Q. rubra and Q. alba were generally lowest for Mg and highest for Mn and K. Significant intra-urban variability in stemflow enrichment was limited to E_P,B of K and E_T,B of Ca (p < 0.05), while trans-regional variability in stemflow enrichment consistently indicated higher E_P,B and E_T,B in more highly developed portions of the study region. At the fragment scale, E_P,B and E_T,B for Q. rubra was consistently higher than for Q. alba, with variability in these observations significant for all solutes. For example, interspecific variability in E_P,B was greatest for K, where median values ranged from 2.8 ± 29.7 in Q. alba to 87.1 ± 97.1 in Q. rubra. While observations for E_T,B were generally lower than those for E_P,B, observations for Q. rubra also consistently exceeded those for Q. alba, with median values for K ranging from 1.5 ± 0.5 to 21.9 ± 3.1 for Q. alba and Q. rubra, respectively. Findings were likely driven by variability in biophysical characteristics between the two species (e.g., bark morphology). Further, findings indicate that species heterogeneity within the urban forest contributes to significant variability in nutrient (and possibly pollutant) transport and fate via throughfall and stemflow below the canopy, with subsequent impacts on urban forest biogeochemistry.

穿透流量和茎流是城市森林中水和溶质的两个重要传输机制，尽管在城市内部很少量化这些通量。这项研究是首次利用两种基于通量的富集比率进行茎流特征，以表征城市森林碎片中水的空间分布和溶质分布。使用基于事件的原位采样，该研究量化了相对于每单位开放降水量（E _P，B）和贯通量（E _T，B）的栎（北方红橡树）和栎（白栎木）树的茎流富集用于溶解的Ca，K，镁，锰，NO躯干断面积₃-N和S。该研究调查了片段，城市和区域范围内养分富集的变异性。在所有溶质中，对Q. rubra和Q. alba的E _P，B和E _T，B的观测值通常对于Mg最低，而对于Mn和K最高。在市区内，茎流富集的显着变化仅限于E _P，B的钾和钾的E _T，B（p  <0.05），而茎流富集的跨区域变异性始终表明较高的E _P，B和E _{T ，B}在研究区域更发达的地区。在片段的规模，ē _P，B和ē _T，B为Q.杨梅是比一贯较高问：阿尔巴，在这些意见对所有溶质显著变化。例如，E _P，B的种间变异性最大的是K，中位值的范围从Q. alba的2.8±29.7到ruba Q. rubra的87.1±97.1 。虽然对E _T，B的观测值通常低于对E _P，B的观测值，但对Q. rubra的观测值也始终超过Q. alba，其中Q. alba和Q. rubra的K中值分别在1.5±0.5至21.9±3.1范围内。两种物种之间生物物理特性的可变性（例如，树皮形态）可能驱动发现。此外，研究结果表明，城市森林内物种的异质性通过冠层下的穿透和茎流，导致养分（可能还有污染物）的运输和命运发生显着变化，从而对城市森林的生物地球化学产生了影响。