【摘要】 造林是固碳（C）的有效方法之一,也深刻地影响土壤氮（N）动态,然而不同造林树种对土壤C和N收支的影响及其机制尚不明确.本研究采用同质园试验方法,测定了东北温带水曲柳、胡桃楸、白桦、落叶松和樟子松5个主要造林树种造林后第3年和第11年表层（0～10 cm）土壤有机C(C_soil)、全N含量(N_soil)的变化,以及植被特性和土壤微生物等相关因子,探究了不同树种造林对土壤C、N的影响及驱动因子.结果表明:试验期间,5个树种纯林的C_soil、N_soil均显著降低,C_soil与N_soil变化量呈显著正相关,并且C_soil减少速率(2.6%·a^-1～4.8%·a^-1)显著高于N_soil减少速率(0.8%·a^-1～2.8%·a^-1).阔叶树种纯林C_soil、N_soil减少量显著小于针叶树种纯林.树种特征、微生物特性共同解释了C_soil变化率的68.5%、N_soil变化率的90.9%,C_soil、N_soil变化率随凋落叶C/N及微生物生物量C/N的增大而减小,但随着细根生物量、微生物生物量C及微生物获取C酶与获取N酶之比的增加而增大;N_soil变化率还随凋落叶产量及微生物代谢熵的增大而减小.这些温带人工林在造林11年后表层土壤C、N含量显著减少,而树种间的不同变化强度主要是由树种特征和土壤微生物特性的差异引起的.更多还原

【Abstract】 Afforestation is an effective way for carbon（C） sequestration, which also profoundly influences soil nitrogen（N） dynamics in the forest ecosystem. The impacts of tree species on soil C and N budgets and the underlying mechanism remain uncertain. In this study, we used a common garden experiment and measured the soil organic C(C_soil) and total N contents(N_soil) of the topsoil（0-10 cm） and related vegetative and soil microbial properties in 2007 and 2015（3 and 11 years after afforestation）, respectively. Our aim was to explore the effects of five major tree species（i.e., Fraxinus mandshurica, Juglans mandshurica, Betula platyphylla, Larix gmelinii and Pinus sylvestris var. mongolica） in the temperate forests in Northeast China on soil C and N contents and their dri-vers. The results showed that both C_soil and N_soil of the five stands decreased as the stand ages increased, the change rates of which were significantly correlated with each other. The rate of change in C_soil(2.6%·a^-1-4.8%·a^-1) was significantly greater than that in N_soil(0.8%·a^-1-2.8%·a^-1). The decrements of the C_soil and N_soil for the broadleaved stands were significantly lower than those of the coniferous stands. The tree-species traits and microbial properties together explained 68.5% and 90.9% of the variability of the change rates of C_soil and N_soil, respectively. The change rates of C_soil and N_soil decreased with the increases in leaf litter C/N and microbial biomass C/N, but increased with the increases of fine root biomass, microbial biomass C, and the ratio of the C-acquisition to the N-acquisition enzyme activity. Additionally, the change rate of N_soil decreased with the increases of the leaf litter production and the microbial metabolic activity. Our findings indicated that C and N contents in the topsoil of these temperate plantations decreased significantly 11 years after afforestation, while the different change rates mainly resulted from different properties of tree species and soil microbes.更多还原