Effect of nitrogen addition on soil respiration in a larch plantation

Abstract

Knowledge about the impact of nitrogen (N) addition on soil respiration (Rs) is critical for understanding soil carbon (C) balance and its responses to climate change. We conducted a long-term field experiment to evaluate the response of Rs to N addition in a larch (Larix principis-rupprechtii) plantation during the growing season in northern China. We applied four N (in the form of NH4NO3) levels, i.e., control (N0: 0 g N m-2 year-1), low-N (N1: 5 g N m-2 year-1), medium-N (N2: 10 g N m-2 year-1), and high-N (N3: 15 g N m-2 year-1) monthly starting in June 2015. The results showed that N addition especially N2 and N3 levels significantly stimulated Rs. N1 and N2 levels resulted in the increase of Rs in a short time, whereas the duration of N3 level can last across the whole month or at least 10 days. The results highlight the need for improving the Rs sampling interval after N addition to ensure more accurate evaluation of C emission. Soil temperature and soil moisture together explained more variations of Rs. N addition exhibited a slight increase in the sensitivity of Rs to temperature (Q10), but no significant differences were found for the Q10 among N levels.