Fig. 1

Locations of study area (open square) in the Great Lakes region of North America (A) and Nissouri Creek subwatershed (closed circle) in the agriculturally dominated landscape of southwestern Ontario (B), where the majority of agricultural lands have tile drainage (red shading). Panel C shows the studied headwater branch of Nissouri Creek located in a woodlot with stream sampling sites distributed along two first order segments draining a spring-fed marsh (western branch, grey triangles) and a tile drained field (northern branch, orange triangles), as well as the downstream combined segment (magenta triangles). Blue arrows on stream lines indicate direction of flow