Effects of Nitrogen on Temporal and Spatial Patterns of Nitrate in Streams and Soil Solution of a Central Hardwood Forest

Figure 2

Mean annual stream water NO₃₋ for WS3 (treatment: solid symbols) and WS4 (control: open symbols) at Fernow Experimental Forest, West Virginia. Arrow indicates initiation of N treatments on WS3. Horizontal dashed lines represent thresholds based on The State of the Nation’s Ecosystems (see text). Heavy dashed line represents correlation between mean annual stream water NO₃₋ and time from 1981 to 2004 for WS4 (𝑟=−0.51, 𝑃<.05); solid line represents relationship from 1998 to 2004 for WS3 (𝑟=−0.90, 𝑃<.01).