增温和施氮对亚热带杉木人工林土壤溶液养分的影响

The effects of warming and nitrogen addition on soil nutrients in the soil solutions from a subtropical Cunninghamia lanceolata plantation

在增温和氮沉降等气候变化背景下,土壤溶液养分元素供应是否平衡对加速或减弱土壤养分循环起着至关重要的作用。为探究增温和施氮对亚热带杉木人工土壤溶液养分动态的影响,分别于各样地的0—15、15—30cm和30—60cm土层安装土壤溶液采集器。利用真空泵的负压原理采集土壤溶液,对其有机组分及无机组分进行了两年的动态监测。结果显示:增温及增温+施氮显著增加了各土层溶解性总氮(DTN)及硝态氮(NO-3)浓度,而施氮促进了植被对其的大量吸收而未呈现显著的促进作用。整体而言,短期增温和施氮处理显著降低了可溶性有机碳(DOC)浓度,对土壤溶液K^+、Ca^(2+)、Na^+、Mg^(2+)等离子含量影响较小。但相比于施氮,增温对土壤溶液中矿质元素的影响远大于施氮。增温导致的土壤孔径增大,通透性增强可极大地促进Fe^(3+)、Al^(3+)淋溶,同时导致表层Na^+、Mg^(2+)离子含量显著降低。增温+施氮交互作用对土壤溶液各养分的影响存在叠加效应,但并不是增温和施氮单因子的简单累加,要深入了解土壤养分对未来气候变迁的内部机制需进一步长期监测。

Climate change can alter soils by causing warming and nitrogen deposition. It is not clear whether the nutrient supply balance in the soil solution plays an important role in accelerating or weakening soil nutrient cycling. The aim of this study was to analyze the effects of warming and nitrogen addition on nutrients in the soil solutions taken from a subtropical Cunninghamia lanceolata plantation. Soil solution collectors were installed at soil depths of 0-15, 15-30, and 30-60cm in every sample plot. The soil solutions were collected using the negative pressure supplied by a vacuum pump, and the dynamic changes to the organic and inorganic components were analyzed for two years. The results showed that warming and warming＋N addition significantly inhibited the dissolved total nitrogen （DTN） and NO3^- concentrations in all the soil layers, and N addition had no significant effect on them due to the increase in mass vegetation absorption of these nutrients. In general, the short-term treatments of warming and N addition significantly decreased the concentrations of dissolved organic carbon （DOC）, but had little effect on the K^＋, Ca^2＋, Na^＋, and Mg^2＋ concentrations in the soil solution. However, the effect of warming on the mineral elements in the soil solution was much greater than that of N addition. Warming increased the soil pore-size and permeability, which greatly promoted Fe^3＋ and Al^3＋ leaching and decreased Na^＋ and Mg^2＋ concentrations in the surface soil. The interaction between warming and N addition may have a combined effect that is more than the simple addition of a single factor. Therefore, further long-term monitoring to understand the internal mechanism of soil nutrient response to future climate change is needed.