Principal response curves for the NH\({}_{3}\) treatment, showing the time-dependent, community-level effects of nitrogen form and dose. The \(y\) axis shows the treatment-time coefficients \(c_{dt}\) from the first PRC component, representing the multivariate measure of plant species composition which best captures the time-dependent response of the vegetation to treatments. Control values are shown as a horizontal line on the plot at \(c_{dt}=0\). The right-hand panel depicts the species loadings, \(b_{s}\). The further these are from zero, the more closely the response pattern for that species correlates with the overall response pattern. \(b_{s}\) values near zero were omitted from the plot for legibility.