关键词: 氮沉降, 凋落物, 土壤, 落叶松次生林

Abstract: We conducted a nitrogen addition experiment (0, 25, 50 and 75 kg N·hm^-2·a^-1 denoted as control, low nitrogen, middle nitrogen and high nitrogen, respectively) in a secondary Larix gmelinii forest to measure C, N, P, K, Ca, Mg, S, Fe, Mn and Zn contents in undecomposed and decomposed litter layers, as well as that in 0-10 cm and 10-20 cm soil layers. The results showed that N and Mn contents in undecomposed litter layer significantly increased by 15.0%-28.5% and 13.1%-22.2% respectively under nitrogen addition treatments; K content significantly increased by 19.3%-24.8% under middle and high nitrogen treatments; P content significantly decreased by 8.8% under high nitrogen treatment; Ca and S contents significantly decreased by 12.2%-13.1% and 9.9%-13.5% respectively under middle and high nitrogen treatments; C, Mg, Fe and Zn contents showed no significant change under nitrogen addition treatments. Compared with control, C and S contents in decomposed litter layer significantly decreased by 10.2%-20.9% and 19.5%-33.9% respectively under middle and high nitrogen treatments; Fe content significantly decreased by 6.5%-9.4% under low and middle nitrogen treatments; Mn content significantly increased by 10.7%-21.2% under nitrogen addition treatments; Zn content significantly increased by 9.3% under high nitrogen treatment; N, P, K, Ca and Mg contents showed no significant changes. Nitrogen addition accelerated the release rates of C, N, K and S from litter, suppressed the release rates of P, Ca and Zn, and did not affect that of Mg, Fe and Mn. Compared with control, Soil organic carbon (SOC) and N contents in 0-10 cm soil layer significantly increased by 40.1%-70.0% and 6.6%-18.8% respectively under nitrogen addition treatments, whereas P and Zn contents significantly decreased by 6.2%-25.0% and 15.1%-32.8%, respectively. Fe content significantly increased by 1.8%-3.9% under low and middle nitrogen treatments, while K content signifi-cantly decreased by 2.4%-3.4% under low and middle nitrogen treatments. Ca and S contents significantly decreased by 8.8% and 39.4%, respectively, under high nitrogen treatment. Mg and Mn contents showed no significant changes. Compared with control, N and S contents in 10-20 cm soil layer significantly increased by 4.3%-13.7% and 24.2%-69.3% respectively under nitrogen addition treatments, while SOC content significantly increased by 55.6%-72.7% under low and middle nitrogen treatments. P and Zn contents significantly decreased by 19.1%-24.2% and 17.8%-24.9% respectively under middle and high nitrogen treatments, whereas K content significantly decreased by 5.8% under low nitrogen treatment. Ca, Mg, Fe and Mn contents showed no significant changes. N and Ca contents in 0-10 cm soil layer were significantly positively correlated with those in undecomposed litter layer, while SOC, N, P, Ca, Mg and Zn contents in 0-10 cm soil layer were significantly positively correlated with their corresponding release rates in litter, respectively.

Key words: nitrogen deposition, litter, soil, Larix gmelinii secondary forest