We quantified wetland relationships with lake total phosphorus (TP) and water color in relation to landscape features at local and regional scales using multilevel mixed effects models on 1,790 north-temperate lakes. Our two research questions were: 1) do human land use disturbances at local scales affect wetland relationships with lake TP and water color? And 2) are wetland relationships with lake TP and water color different across regions, and if so, what regional characteristics are related to this variation? We found that land use disturbance at the local scale did not interact with wetland-lake TP relationships but regional agriculture was negatively related to wetland-TP slopes. In regions with low proportions of agriculture wetland-TP slopes were positive, and in regions with high proportions of agriculture wetland-TP slopes were negative. In addition, lake TP and water color were related to similar local lake and catchment characteristics but different regional characteristics. Regional agriculture explained 22% of the variability in TP and regional groundwater explained 4% of the variability in water color. Regional groundwater was negatively related to wetland-water color slopes such that wetland effects were weak in regions with high groundwater. These results demonstrate that lake TP and water color are hierarchically controlled by landscape variables at both local and regional scales and that the regional setting influences wetland relationships with both lake TP and color.
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