Biotic and abiotic factors affecting throughfall volume and spatial variabiity in a New England forest

The hydrologic characteristics of New England forests are likely to change as eastern hemlocks (Tsuga canadensis) are increasingly impacted by the hemlock woolly adelgid (Adelges tsugae), an exotic insect pest. The declining hemlocks abandon their unique ecohydrologic role as a riparian foundation species in New England. In order to predict the hydrologic changes that may take place in New England forests as a result of climate change and forest species composition shifts, it is important to understand how vegetation affects precipitation inputs into forested ecosystems. This study investigated the effects of forest stand type and meteorological factors on throughfall volume and spatial variability in four forest stands in at the Smith College MacLeish Field Station in Whately, Massachusetts. The two hemlock stands demonstrated greater interception loss than the mixed deciduous stand and the young black birch (Betula lenta) forest stand. Throughfall spatial distribution beneath the deciduous and birch stands had high spatial variability (CV = 0.33, 0.13, 0.28) and was positively skewed (γ = 2.8, 0.01, 2.7), while throughfall distribution beneath hemlock stands was negatively skewed (γ = -0.14, -0.39, -0.89) and demonstrated comparable spatial variability to the deciduous forest stands (CV = 0.24, 0.27, 0.16). Analysis of variance indicates significant differences in throughfall volume and interception fraction between forest stands. Throughfall spatial patterns beneath all forest stands demonstrated temporal persistence. Analysis of variance indicates distinctions in throughfall coefficient of variation among different forest stands (p\u3c0.05). Linear regression models indicate that precipitation amounts were positively correlated with throughfall coefficient of variation and skew in the black birch stand and negatively correlated with coefficient of variation in the deciduous stand. Increased wind 2 velocity during precipitation was positively correlated with coefficient of variation in the hemlock and positively correlated with skew in the deciduous stand