Influence of bedrock geology and tree species composition on stream nitrate concentrations in mid-Appalachian forested watersheds
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Water, Air, and Soil Pollution. 160: 55-76.
Although the large variations in nitrate export from forested watersheds have been attributed to a variety of natural and disturbance-related factors, baseflow nitrate concentrations in 49 mid-Appalachian forested watersheds were most strongly related to differences in bedrock geology. Within the mid-Appalachian region of Pennsylvania, Maryland and West Virginia, watersheds dominated by Pottsville and Allegheny sandstone (PVA), Catskill, Chemung, and Pocono shale and sandstone (CCP), and Mauch Chunk shale and Greenbrier limestone (MCG), respectively, exhibited significantly different low, intermediate, and high mean stream nitrate concentrations. Soil pH, soil percent N concentration (%N), soil C:N mass ratio, soil exchangeable Ca, watershed slope, and the occurrence of white ash (Fraxinus americana L.), sugar maple (Acer saccharum Marsh.), and eastern hemlock (Tsuga canadensis L.) were related significantly to bedrock geology type as well as stream nitrate levels. Other factors such as past land disturbances (fire and agriculture) and stand age (old-growth) typically were associated with only one bedrock geology type. However, within a bedrock geology type, past agriculture and the presence of old-growth forest may be important in explaining stream nitrate concentrations on an individual watershed basis.
Keywordsagriculture; black locust (Robinia pseudoacacia L.); C:N ratio; fire; forest; land-use history; old-growth; nitrate leaching; nitrogen saturation; water quality
Williard, Karl W.J.; Dewalle, David R.; Edwards, Pamela J. 2005. Influence of bedrock geology and tree species composition on stream nitrate concentrations in mid-Appalachian forested watersheds