## 4 Discussion
Its vegetation composition, however, was silver maple (_Acer saccharium_), eastern cottonwood (_Populus deltoides_), boxelder (_Acer negundo_), and sycamore (_Platanus occidentalis_), which is mostly different from that found around the US-ULM tower in the RSWMA. [PERSON] [30] reported R\({}_{\rm n}\) as a major driver in upland hardwood growth forests and VPD as a major driver in wetland ecosystems during the vegetatively active time of the year in northern Wisconsin. The dominant hardwood vegetation composition at this site was sugar maple (_Acer saccharium_), basswood (_Tilia americana_ L.), and green ash (_Frazimus pennsylvania_ Marsh), mostly different from the hardwood community found in the RSWMA. However, a much higher effect of precipitation has been reported in water-limited ecosystems such as BHFs and seasonal cycles of canopy greenness in energy-limited ecosystems in higher latitudes using path analyses [31]. Similarly, in humid boreal regions, VPD and R\({}_{\rm n}\) were characterized as major drivers of sap flow and thus transpiration during the growing season, as well as during drought [32]. In closed-canopy deciduous BHFs like the one in this study, R\({}_{\rm n}\) controls the variability of ET through two different pathways: first is the direct pathway, in which throughout the growing period (spring to summer) and early autumn, R\({}_{\rm n}\) directly promotes transpiration, which contributes about 80-90% of the total ET, as shown by [24]; second is the indirect pathway, in which when there are no leaves in the vegetatively dormant period, the direct impact of R\({}_{\rm n}\) is somehow attenuated, and the R\({}_{\rm n}\) influences ET variability indirectly via temperature and VPD. This is also supported by the consistent variability pattern shown by R\({}_{\rm n}\) and ET in seasonal plots (except winter) in Figure 3, and as reported by others [33; 34]. Seasonally, WS and precipitation play a critical role during summer when the atmospheric humidity is higher compared to other seasons, albeit a small one. The increase in WS and precipitation positively influences wetnes (one of the latent constructs), subsequently affecting ET negatively in the process (path coefficients = 0.70 and \(-\)0.26 for dryness-ET and wetness-ET, respectively). However, the negative effect of WS on ET, as seen in Figure 5a, could be due to its significant negative impact on temperature, which in turn has a strong influence on ET through the VPD. As observed in the structural model in Figure 5b, WS contributes significantly as a major driver of atmospheric wetness, a latent construct with a significant negative effect on ET. In a study by [PERSON] [35] in the Atacama Desert ecosystem of Chile, it was shown that strong winds in the afternoon enhance mechanical turbulence and increase evaporation. A similar path analysis conducted in a mid-latitude agricultural site in China found similar results, with WS having the least direct and indirect effects on ET [17]. On the other hand, precipitation has a minor positive impact as a driver of ET, as seen in the correlograms (Figure 2). However, there is an increasing negative impact of precipitation, as seen in Figure 3, and it has a significant negative contribution to latent construct wetness; hence, over larger timescales the impact is suggestive of a seasonal reduction in ET, as precipitation is observed for longer periods, especially during growing season. From similar research carried out at high-latitude regions, [PERSON] [15] reported similar control of precipitation as a driver of ET and suggested it as a potentially relevant driver of ET in mid-latitude regions such as these BHFs. These findings of seasonal relations of ET with meteorological variables are consistent with those from similar studies in Canadian forest ecosystems [36]. This also strengthens the conclusion that precipitation contributes positively to short-term enhancement in ET and negatively in the long run.