Browsing by Author "Hudson, Sean A."
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Item The effects of meteorological conditions on throughfall drop size distribution under a broadleaved deciduous forest canopy in northeastern Maryland(University of Delaware, 2016) Hudson, Sean A.Forests cover roughly a third of the ice free land surface on the planet. The partitioning of incident precipitation by a forest canopy into throughfall and stemflow varies as a function of meteorological conditions, tree species, leaf morphology and surface roughness, among other factors. Nanko et al (2016) examined the throughfall drop size signature of precipitation events relative to changes in leaf canopy state of deciduous forests. However, little work has been done to quantify the influence of meteorological variables (air temperature, wind speed, wind direction, rainfall intensity and duration) on drop size among discrete rain events. To quantify individual throughfall drops, a laser disdrometer gauge was deployed below an observed drip point under a Liriodendron tulipifera L. (yellow poplar) tree, in northeastern Maryland, USA. Using multiple correspondence analysis, lower air temperature (4.0-12.0°C), low precipitation intensity (0.1-1.5 mm.5min-1), and low wind speed (0.1-1.0 m.s-1) were found to associate with periods of large throughfall drop production. Two canopy storage systems were identified, static and dynamic, with the static storage system being dominant during the foliated period and the dynamic during the unfoliated period. These results have implications for understanding biogeochemical cycles, as well as identification of throughfall hotspots from meteorological observations.Item Relevant field data for Phenoseasonal subcanopy light dynamics and the effects of light on the physiological ecology of a common understory shrub, Lindera benzoin - PLOS ONE(Department of Geography, University of Delaware, Newark, DE, 2017) Hudson, Janice E.; Levia, Delphis F.; Hudson, Sean A.; Bais, Harsh P.; Legates, David R.Item Soil water potential response to double funneling of precipitation on a forested, Mid-Atlantic hillslope(University of Delaware, 2019) Hudson, Sean A.Soil matric potential measurements were taken on a hillslope beneath a 74 cm diameter at breast height (dbh) Fagus grandifolia Ehrh. (American beech) tree between January 2012 and November 2014. Thirty-six sensors were installed in three transects at four locations downslope from the tree, at three depths (30, 45 and 60 cm). Data were examined for temporal persistence and variability, preferential flow, and change in soil water storage and drainage. Results indicate that as sensors reveal greater soil wetness, both temporal variability and the root mean square error of mean relative difference increase. This indicates that short term increases in soil moisture are responsible for the observed variability. Additionally, stemflow infiltration is observed as a short-lived increase in storage, with significant drainage occurring within the first thirty minutes. Preferential flow occurred along consistent flow paths which were identified not only by the occurrences of out-of-sequence flow, but also indicated by temporal persistence and storage/drainage. Finally, year-to-year variation indicated the relationship of preferential flow occurrences and timing of precipitation; 2013 had significantly more precipitation early in the growing season and led the three study years in the occurrence of both preferential and sequential flow responses. Further investigation into the five identified precipitation classes indicate that precipitation events over 30mm which included extreme events such as Hurricane Sandy, have more common occurrences of preferential flow smaller magnitude events. Thus, the major conclusion of this study is stemflow infiltration and transport increases the moisture along a set group of sensors that coincide with the location of roots > 2.54cm in diameter. Additionally, stemflow infiltration and transport causes a short-term increase in soil water storage, with sensors identified along the preferential flow path having higher soil storage maximum values, larger post rain fall drainage (WD0.5) and additional drainage after soil moisture levels return to antecedent conditions. Precipitation events with magnitudes greater than 30mm tend to have higher instances of preferential flow as well as larger increases in maximum soil water storage than smaller magnitude events. Finally, year to year variability is more related to changes in yearly precipitation event timing, which has implications for changing precipitation regimes.