Synoptic Climatological Approaches to Assessing Subcanopy Hydrologic and Nutrient Fluxes in a Temperate Deciduous Forest

The partitioning of precipitation incident to a forest canopy into throughfall and stemflow is controlled by biotic and abiotic factors. Biotic factors include canopy architecture, bark and leaf morphology, and leaf presence whereas abiotic factors include precipitation, antecedent moisture conditions, and wind speed. Previous studies relating the subcanopy hydrologic flux to storm events consider the aforementioned abiotic factors at the event level. This research applies atmospheric classification methods from the field of synoptic climatology to relate large scale weather patterns to local forest hydrologic conditions. A daily synoptic calendar is employed to categorize the observed subcanopy hydrologic flux during storm events and is evaluated as a tool for historical reconstruction and future prediction of forest hydrologic conditions as precipitation regimes are influenced by climate change. At the seasonal scale, the majority of precipitation occurs in 4 out of 13 synoptic types in winter, 4 out of 13 in spring, 2 out of 9 in summer, and 5 out of 11 in autumn, the remaining synoptic types are dominated by fair weather conditions (although small precipitation amounts are sometimes observed). During the study period, precipitation is correctly predicted by synoptic types 82% of the time in winter, 70% in spring, 88% in summer, and 73% in autumn. Analysis of variance (ANOVA) indicates that spring, summer, and fall precipitation-producing synoptic types predict statistically different subcanopy throughfall fluxes. The absence of foliage and more homogenous winter canopy may diminish the predictive ability of synoptic typing in regards to throughfall at that time of year. Biogeochemical canopy fluxes associated with storm events are also distinguishable using the synoptic calendar.