60 40
Nitrate (NO2) concentration
(milligrams per liter)
Undisturbed
(control)
watershed
-Disturbed
(experimental)
watershed
20
1963 1964 1965 1966 1967 1968 1969 1970 1971 1972
Year
Figure 1: Nitrate concentration from a deforested watershed experiment (Miller and
Spoolman, 2011)
9 Figure 1 above illustrates the measured differences in the concentration of nitrate ions in a
watershed, resulting from an experimental deforestation. Which one of the following
observations is true?​