Fig. 4. Graphs of landscape measures for the five watersheds in the Western Corn Belt Plains (watersheds > 25 km2) with the highest habitat index (HI) scores and the five lowest. ED, edge density ([m/ha]/10); TP, total phosphorus (mg/L); SHDI, Shannon diversity index, ranging from 0 to 1 with higher values indicting a watershed with a relatively greater balance of land use–land cover (LULC) types; HI, habitat index ranging from 0 to 1 with higher scores indicating higher quality habitat; HI-a, riparian vegetation quality; HI-b, lack of disturbance in riparian zone; HI-c, substrate quality. This graph shows what at first appears to be counterintuitive relationships: Watersheds with higher quality habitat have a lower edge density and lower landscape diversity. In a rural, predominantly agricultural area, edge density might intuitively indicate more forest and hence lower turbidity and better substrate, and a higher Shannon diversity index might intuitively indicate more forest or grassland. But urban areas also add edge, and the presence of forest might be indicative of erosion from bluffs along the Missouri River. The correlation tables (Tables 5 and 6) indicate that, in fact, higher turbidity is associated with percent forest and percent urban.
