Figure 4
From: Productivity depends more on the rate than the frequency of N addition in a temperate grassland
Effects of N addition on soil factors across 2012–2013.
The top 10 cm soil water content (a), soil temperature (b), soil pH (c), soil ammonium concentration (NH4+–N); (d) and soil nitrate concentration (NO3−–N); (e) in response to the two N addition frequencies (filled symbols = 2 N additions yr−1, open symbols = 12 N additions yr−1) and N-rate. Error bars indicate 1 SE. F, N addition frequency and N, N-rate (N as the continuous factor), ns, *, ** and ***: statistically significant at P > 0.05, P < 0.05, 0.01 and 0.001, respectively.
