Effects of long-term nitrogen addition on fine root dynamics in a temperate natural secondary forest

ABSTRACT In order to study the response of fine root production (FRP), mortality (FRM) and turnover (FRT) to nitrogen (N) addition, we have conducted 12 years of continuous N addition experiments in the natural secondary forest in Northeast China. According to the local N deposition, three N treatments were set up. The response of FRP, FRM and FRT to N addition during the growing season was studied. The results showed that N addition would lead to phosphorus (P) limitation, and fine roots could increase the absorption of N and P by increasing their diameter. The increase in the diameter of fine roots led to a decrease in the FRT, and the soil layer also affected the FRT. Nitrogen addition increased the FRP and FRM in all soil layers. Nitrogen addition did not change the seasonal variation of FRP and FRM. The highest value of FRP occurred in May, and the lowest value of FRM occurred in August. Nitrogen addition increased the total number (TNLR) and surface area (TSALR) of live fine root in all soil layers. The TNLR and TSALR decreased with the deepening of soil layer. Collectively, fine roots may respond to environmental stress through self-regulation and changing growth strategies.