施氮频率和强度对内蒙古温带草原土壤pH及碳、氮、磷含量的影响

Effects of the frequency and intensity of nitrogen addition on soil pH,the contents of carbon,nitrogen and phosphorus in temperate steppe in Inner Mongolia,China

以内蒙古温带典型草原为研究对象,通过9个氮沉降梯度以及一年12次和一年2次的施氮频率比对,经过4年的氮沉降模拟,研究不同氮沉降强度和频率对不同土层土壤p H及碳、氮、磷含量的影响.结果表明：随着施氮强度的增加,土壤p H及全磷含量逐渐降低,但土壤有效氮和有效磷的含量呈增加趋势,可溶性有机碳（DOC）含量无明显变化规律,而土壤全碳、全氮含量基本保持不变.与更接近于自然氮沉降状况的一年12次施氮相比,一年2次施氮明显高估了氮沉降在降低土壤p H和增加有效磷含量上的作用,低估了氮沉降在增加土壤有效氮含量上的作用,其中0~5 cm土层差异显著.

A four-year simulated nitrogen（ N） deposition experiment involving nine N gradients and two N deposition frequencies（ N was added either twice yearly or monthly） was conducted in Inner Mongolian grassland,to examine the effects of frequency and intensity of N addition on p H and the contents of carbon,nitrogen and phosphorus in soil. The results indicated that the soil p H and total phosphorus content,regardless of the N addition frequency,gradually decreased with the increase of N addition intensity. By contrast,the contents of soil available nitrogen and available phosphorus showed an increasing trend,while no significant variation in dissolved organic carbon（ DOC） content was observed,and the contents of soil total carbon and total nitrogen had no change. Compared with the monthly N addition,the twice-a-year N addition substantially overestimated the effects of N deposition on decreasing the soil p H and increasing the available phosphorus content,but underestimated the effects of N deposition on increasing the soil available nitrogen content,and the significant difference was found in 0-5 cm soil layer.