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

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 30-60 cm 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+,Ca2+,Na+,and Mg2+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 increasedthe soil pore-size and permeability, which greatly promoted Fe3+ and Al3+ leaching and decreased Na+and Mg2+ 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.